Success Under Stress: Managing and Restoring the Metroforest

SUCCESS UNDER STRESS: MANAGING & RESTORING THE METROFOREST

by

Leslie Sauer and Carol Franklin University of Pennsylvania Graduate School of Fine Arts Department of Landscape Architecture & Regional Planning 34th & Walnut Streets Philadelphia PA 19104

Prepared under Grant No. 87-4251-0067 of the Design Arts Program National Endowment for the Arts Room 625, 1100 Pennsylvania Avenue, NW Washington DC 20506

• 28 February 1989 .~

TABLE OF CONTENTS

-,Introduction

1

The Metroforest

3

A Proposed Approach & Framework to a Forest Management & Restoration Program

11

Ground Stabilization

16

Stormwater Management

17

Excess Fill

36

User Activities Which Damage Landscapes

40

Soil Compaction

44

Dead Wood & Brush

50

Invasive Exotics

54

Landscape Management Strategies: Control of Invasive Exotic Vegetation

63

Forest Vegetation Restoration

71

Criteria for Forest Review & Evaluation

73

Replanting Strategies

80

Habitat Corridor Networks

92

Recommended Reading List

95

INTRODUCTION

There is no such thing as a preserved landscape, any more than a human being can be preserved, frozen in time. We can dedicate parkland and restrict development from selected natural areas, but this does not eliminate continued impacts from surrounding development on a local scale or from environmental alterations on a global scale.

Those responsible for the care of protected landscapes have become increasingly concerned about the accelerating deterioration of their resource. At the same time, park usage has increased dramatically. The negative impacts of use and abuse are already sadly apparent in urban parks and are becoming increasingly visible in suburban and rural areas.

Natural areas are sometimes seen as "maintenance" liabilities. Further acquisition of preserved land may be restricted by the unWillingness of agencies to be responsible for their care. The situation is even worse on developed lands, where there are virtually no provisions for the protection of natural habitats.

And in the meantime, native habitats are everywhere declining and the rate of deterioration is accelerating. Over half the planet's trees have been cut since 1950. For millions of people, contact with the natural world, restricted to public parks and remnant wildlands, is an increasingly diminished experience. From New England to the south along the East Coast, the fate of our forests is in our hands. Rural areas are experiencing rapid suburbanization, a fragmenting and displacing the remaining wildlands. In smaller cities like Wilmington, we are just beginning to see the problems that plague larger cities like Philadelphia, and for the serious time traveler, there is New York City, where the forests of our future can be seen: the metroforest.

Park users and managers alike are growing aware of the urgency of the problem, but are hampered by the lack of information and experience in recognizing and dealing with the management and restoration of disturbed landscapes. Natural resource managers may be trained to work with natural systems, but often have no familiarity with disturbance ecology. Horticulturalists usually are even more poorly equipped. There are no consistent policies or proven methodologies that deal with disturbance and deterioration. Despite this, many people are tackling these problems and getting good results for their efforts. Progress is not necessarily smooth and transformations are not instantaneous, but the deterioration can be stopped and improvements can be initiated.

The art and science of the care of the metroforest are being developed right now by concerned managers, who are monitoring, studying, maintaining, replanting, and experimenting in urban forests. They are aware that restoration is an on-going job, that natural systems are often too compromised to expect them to recover if simply left on their own. This manual is intended to assist in this restoration process, providing an Success Under Stress: Managing & Restoring the Metroforest

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approach for assessing each site, guidelines for determining management goals, and an overview of appropriate management and restoration techniques.

Most of the material presented here will hopefully need updating within a short period of time, as the actual management of natural systems creates numerous demonstration areas for applied research and increases our stock of knowledge and experience.

Unfortunately, many of the problems of urban forests go far beyond the scope of this manual. Many of the more intractable problems facing landscapes are linked to larger social issues, which are not yet being satisfactorily resolved. Trampling resulting from encampments by the homeless, for example, is not simply a landscape management concern, but requires a concerted effort from a broad spectrum of people and agencies.

Landscape managers must add their voices to those seeking positive change or else face a hopeless task.

The format of the manual includes both a discussion of the larger issues to give a context for decision making as well as descriptions of specific approaches and techniques. Several case studies are reviewed and recommended management programs are delineated for a variety of landscape types which are generic to urban areas.

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THE METROFOREST

Prior to settlement by Europeans, the entire megalopolitan region was blanketed by forest which was broken only by rocky outcrops, large rivers, and coastal wetlands. With the onset of lumbering and agriculture, the land was cleared and the houses, towns, pastures, and croplands of northeastern America were carved out of the forest and maintained through constant effort at controlling natural growth. In the mid-nineteenth century, this intensive pressure was partially diverted by industrialization and subsequent migration to the cities, as well as the opening of rich farmland in the midwest. Farms were abandoned and the total amount of forested land in the east slowly increased until just recently. At the same time, many park systems, both public and private, were established, especially in valleys, as the importance of the role of forests in protecting water quality and regulating the flow of surface and ground waters was recognized.

The returning forest is different, however, from that which greeted the 18th-century settlers. The unbroken forest expanse has been replaced by small islands, each with little or no forest interior and cut off from other forest systems. Today's forests generally have been restricted to less productive land: the rocky outcrops and steep slopes not suitable for farming or development. The landscapes around us are also younger, and there are many miles of "edge", an increasing habitat that favors species which were limited in older forests. Hundreds of new species of both plants and animals have been introduced on a large scale, both deliberately and accidentally. Some have joined native communities, like the bird cherry, and are hardly distinguishable from indigenous species in their behavior. Others, such as Norway maple, kudzu, honeysuckle, and Asian knotweed, have experienced population explosions, away from their natural controls, and are spreading so rapaciously that they are overwhelming many stressed native plant communities. Similarly, some diseases and pests introduced from abroad have found unresistant hosts here, eliminating several important native species. The chestnut and elm now make token appearances in landscapes they once dominated.

Virtually all remaining native and volunteer landscapes occur in the fabric of developed land and have recently been subjected to rapid changes in environmental conditions, including major alterations in the hydrologic cycle, soil disturbance from vegetation clearance, increased erosion, trampling, and air and water pollution.

The look of the 'metroforest' is familiar to all of us. The ground is most glaringly different in appearance from that of an undisturbed forest. Litter is often ubiquitous and may range from abandoned cars and dumped construction rubble to larger particles of urban soil, including broken glass, paper bits, and cigarette butts. Bare soil may be exposed often over a large area, resulting from trampling, stormwater runoff, filling or excavation.

In urban areas, wildlands may also provide temporary shelter to the homeless and toilet facilities for many users.

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Where disturbance is chronic, invasive exotic vegetation may prevail, typically in monospecific stands. Even where forest persists, alien vegetation is almost always present and is usually increasing. Large relic native canopy trees may still occur, but have long since ceased reproducing. Volunteer saplings of cherry and locust, usually typical of young field landscapes, may fill the large gaps in the canopy. Norway maple frequently can be found in every layer of the landscape. Vines, both native and exotic, may occur in heaping mounds on the ground, draped over shrubs and saplings, and cloaking trees in the canopy. Ferns and woodland wildflowers may be conspicuously absent or reduced to one or two species. Species diversity has usually been declining for years, although human use, especially for recreation, may be steadily increasing.

While nature herself is remarkably variable, disturbance is typically simplistic. When disturbance is uncontrolled, deterioration usually accelerates and a once rich site steadily diminishes in diversity, value, and interest.

There are so many sources of disturbance in the modern urban environment that it is often all too easy to assume that solutions are too complicated to implement. Parks are frequently perceived as becoming "unmanageable". Air pOllution, for example, is visible and extreme, yet seems beyond a park's control. More importantly, however, is the fact that the greater share of disturbance is due to the nature of human activities, not environmental conditions. The same changes which are observable in urban woodlands can also be seen in woodlands of rural parklands as well. The intensity of use is certainly problematic, and a growing stress on parkland, yet this is also the very reason most parks exist: to be used by people. A major goal of this report is to assist parks departments to confront and change those uses and activities which damage the landscape, for urban wildlands can be sustained over time only if we succeed, through management, to prevent further damage and compensate for environmental stresses.

Despite the complexity of urban systems, there are actually only a few major stresses that account for the bulk of disturbance. They include landscape disturbance from the off-trail use of bicycles and vehicles, trampling, dumping stormwater management, the proliferation of invasive exotic vegetation, and the lack of maintenance and security.

They must be tackled directly, for until they are resolved, true restoration will remain an illusion. Once disturbance is controlled, the landscape will become far more able to renew itself. The task of restoration is immense and recovery will not happen overnight.

It is necessary to set priorities. Rather than trying to deal with everything, this program focuses on a few critical activities, in order to effect significant changes for the better, to reverse the process of deterioration, and to initiate recovery.

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SUCCESS UNDER STRESS: MANAGING & RESTORING THE METROFOREST ~ . ,

by Leslie Sauer & Carol Franklin

THE HUNTER'S FOREST The forest before settlement was closed and dark, a place of very gradual change. Lofty white pines (1) which persist above an established hardwood canopy, and the evergreens (2) of shaded valleys recall a colder landscape. Tall, straight trees predominate, among then the oaks, chestnuts, maples, and hickories (3). Gaps occur infrequently in this forest. The space of a fallen tree is rapidly occupied by shade-intolerant species, such as the tulip poplar, or closed in by new growth on the surrounding vegetation (4). Where Indians have burned (5), the landscape is open and park-like beneath a high canopy. The narrow stream is marked only by a subtle change in composition. At the water's edge, elm and silver maple are draped with vines (6).

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THE SETTLED FOREST The appearance of the settled forest is radically different from the hunter's forest, although many of the species are the same. The pastures and croplands are geometric in layout and the forest is relegated to lines and pockets. As soon as management of the land stopped, however, the forest came back in many different ways. The hemlocks have been spared on only the steepest slopes (1) and the hardwoods (2), sprouted from old root stock, are brushy and many stemmed from repeated logging. A farmer's field (3), only recently abandoned, is once again filled with a great diversity of plants and the hedgerow (4) already grows in tight forest layers. A lone tree -- a relic of the forest -. shelters cows in a pasture. Protected from trampling, hay-scented fern (5) spreads beside an old stone wall. These stones, cleared from a field for plowing, and the dense young woodlands nearby give evidence of past farming as surely as the chimney ruins of a farmhouse.

Along an early roadside (6), European weeds mingle with the briars and vines, whose tangle is yet another first step in the return of the forest. When the land was cleared, the dramatic increase in run-off and sedimentation made the stream more active. The rapidly cut and filled banks provide good habitat for willow and box-elder (7).

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THE METROFOREST The forest is completely fragmented now, confined to isolated patches and narrow corridors. The oldest, least disturbed forest persists on the steep slope, but the steady invasion of Norway maple from adjacent plantings is visible in the shrub layer (1). Fill, trash, and honeysuckle prevail at the edge but a remnant native community struggles in the interior. The rural fields and pastures are rapidly succumbing to suburban development. Familiar pastoral elements such as hedgerows and lone specimen trees (2) now serve a landscape character for adjacent new buildings. Most reproduction of native communities is eliminated, having been replaced by asphalt, turf, or mulch bed. A few vigorous vines and garden escapees are the only volunteers. In a few small park areas which have been under-maintained for decades support discontinuous woodlands of dense black cherry and black locust amid older oaks and maple and relic privet and euonymous (3). Joggers, birdwatchers, dirt bikers, and baby carriages are all on the increase. Remnant woodlands in the urbanized areas are more dominated by non-native trees, especially tree-of-heaven and princess tree with a few tolerant species characteristic of floodplains, such as box elder (4). Horticultural plantings are typically confined in beds and boxes and frequently highly maintained. the stream course is hardly recognizable, having been channelized and, in places, bulkheaded. Japanese knotweed forms a continuous edge punctuated only by a few remaining sycamores (5).

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Photograph: Showing a healthy, mature, oak-tulip poplar forest of the southern Pennsylvania metropolitan area. Note the presense of 4 clearly visible layers -- canopy, understory shrub and ground layers and the absence of vines, large numbers of dead and damaged trees and bare areas or deadwood and brush on the ground.

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Photograph: Illustrating initial forest deterioration. The shrub and understory layers are still in tact, but vines are beginning to move in from the disturbed edges and occasional pest species are present in the canopy. Unusual amounts of brush and deadwood are present and unfilled holes are apparent in the canopy, while bare areas have developed on the ground.

Photograph: Showing a highly disturbed metro-forest. Note the presense of many damaged and dying trees, The ground is either bare and eroded -- exposing tree roots, or covered with heaping vines. The complexity of forest structure is reduced to two layers and two non-native species, Norway maple in the canopy and Japanese honeysuckle on the ground.

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Photograph: Showing a deep gully created by stormwater outflow. Urban wildlands, often found in protected stream valleys, are especially subject to severe damage from stormwater collected at the edge of the plateau and discharged downslope from open pipes or culverts. Here, the gully has been eroded 6 feet or more to bedrock and is draining groundwater from the surround slopes.

Photograph: Showing a trampled and heaVily compacted area at a scenic overlook adjacent to a well used park trail. Overuse and abuse of popular visitor places has emerged as a second major cause of damage to the urban forest.

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Drawing illustrating the difficult world of the urban tree root, where stresses range from compaction and pollution by salts above ground to minimal water, oxygen, and soil below ground. This drawing was made for the 1980 Philadelphia Flower show exhibit of the Morris Arboretum of the University of Pennsylvania and later became a weekly reader poster.

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A PROPOSED APPROACH & FRAMEWORK TO A FOREST MANAGEMENT & RESTORATION PROGRAM

Returning complex native plant communities to the forest and with them native wildlife is usually the primary goal of those interested in restoring the landscape. Yet simply replanting a diversity of species on a site in which they may have thrived in the past is often doomed to failure. Eager volunteers often plant hundreds of wildflowers in an urban woodland fragment only to find that even with vigorous maintenance almost none are left after a few years. Elsewhere rare plants may be rescued from a site being developed and relocated to a nature preserve where they seem to thrive for a season or two and then suddenly disappear.

It is often very difficult for landscape managers to accept that restoration is not a simple horticultural procedure of planting followed by maintenance. Indeed a background in gardening or horticulture often creates very false perceptions in the landscape manager, for the gardener rarely expects the landscape to become self-sustaining nor does the horticulturalist wish the plants to breed according to their own inclinations. These disciplines along with landscape architecture usually presume a high level of control over the site and the landscape and tend to focus on the individual plant. Unsuitable conditions are changed as needed; a lot of effort is concentrated in a relatively small area; and it is often desirable to accomplish as much as possible all at once. Thousands of laborers, for example, were brought into Central Park to implement Olmsted and Vaux's Greensward Plan, draining swamps, and filling over barren bedrock to create rolling hills with idyllic pools and cascades along meandering streams. The Ramble, at the Center of the Park, was planted as an idealized, romanticized forest-like landscape crafted with the highest level skills of Victorian design. It was a triumph, and it was a significant habitat alteration, but it was not a habitat restoration.

Landscape restoration is not about creating a complete new landscape modelled on a natural ideal, anymore than a child can be viewed as a blank form to be molded into whatever model we select.

The most difficult obstacle to restoration is determining a restoration model that is suitable to and feasible on a given site. For any area there are an infinite number of landscape types that might occur over time just as there are an infinite number of communities that would never occur on sites with similar environmental conditions.

Some sites will be so disturbed that habitat alteration will be the most appropriate restoration model. Restoring a sanitary landfill site to a mature forest may be overly ambitious and benefit from a shorter-term restoration model that seeks to establish native successional plant communities which are gradually and naturally developing into forest.

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On the other hand, a healthy native mature forest may be a very appropriate restoration model for a degraded forest. Similarly, establishing healthy native meadows where invasive dominated meadows occur is probably a sounder goal than assuming a transition to a forest type, at least at the outset. Obviously a general goal is to achieve as high a degree of restoration possible but if our goals are too far removed from the original site the necessary intervening steps may be too difficult to visualize and too complicated to realize. It is important to aim high, but also be aware that sustaining ever larger areas of healthy native communities is a very high goal. Just turning the cycle of destruction into a cycle of restoration, however slowly, would be an extraordinary achievement. As a general rule of thumb it is probably advisable to initiate recovery over as large an area as possible rather than focusing intensive effort in a few small areas.

This should be combined with great efforts to preserve all relatively undisturbed areas.

This is probably the last generation who will even have the option of protecting native landscapes, for the last remaining natural habitats are being threatened right now across the globe.

Another significant obstacle to woodland restoration has been the difficulty of finding an approach which reconciles the seemingly conflicting needs of the various interests, especially between those who feel all 'natural' areas should be left in Mother Nature's hands and unmanaged and those who are concerned about historic landscape character and aesthetic design. A real problem seems to lie in the idea that 'restoration' can be accomplished as a discreet project, analagous to an architectural reconstruction project or a conventional landscape installation.

Such an approach by definition concentrates site disturbance, involving removal of all vegetation at once before initiating replanting and stabilization. A large project, which includes architectural reconstruction, may span several seasons, during which time nearly all valued wildlife is displaced from a site. An area which is a temporary resting site for migratory warblers may be irreplaceable in a vast urban wasteland. Even a project affecting only a portion of such a site may deny critical habitat to birds who cannot wait out a one or two year hiatus.

Struggling natural vegetation would be similarly impacted. When forest restoration is viewed in the spirit of a capital project, the sheer amount of work undertaken becomes a severe stress to fragile remnant systems. Large-scale grading operations, extensive soil reworking, and massive planting efforts are, in this perspective, sources of disturbance and should be undertaken only where the landscape is in collapse, completely overwhelmed by knotweed, or with extensive and severe erosion. Similarly, where the vegetation is a mix of desirable species and pests, complete elimination of all invasives at once may actually open up the landscape so much that a reinvasion, perhaps even greater in scale, is invited.

A common approach to solve these problems is fragmenting a project into smaller pieces. However, though this confines damage to more limited areas at one time, it does not address the fact that this is simply a stressful way of working, and antithetical to establishing healthier, more self-sustaining natural systems. The discreet design and Success Under Stress: Managing & Restoring the Metroforest

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construction phase, under the tight control of the landscape architect, completed in one fell swoop, is simply not effective or even acceptable in the forest.

The recommended alternative involves incremental implementation and seeks to achieve restoration in discrete phases, which represent levels of health of the system, instead of area-by-area project completion. An important key to this approach to restoration is the principle of "minimal intervention", that is, taking only those actions which are necessary to counteract disturbance, but also taking no actions which may inhibit the natural processes of restoration.

Recommendations made by foresters and horticulturalists often are very inappropriate in woodland areas. Every effort should be made to avoid unnecessary soil disturbance, such as grubbing and rototilling. These methods may be appropriate to renovating a horticultural bed planting, but are not suited to woodlands. If the surface is presently stable, even if supporting only exotic invasives, beneath the soil there are roots of numerous different plants often from a great distance away. Tree roots, for example, are completely opportunistic, seeking any favorable ground, and easily extend thirty or more feet beyond the furthest reach of their branches. Grubbing and rototilling also disrupts fragile microorganisms and may impact the mycorrhyzae on which good forest growth depends.

The directive to thin canopy in order to stimulate shrub growth is almost always inappropriate in woodlands. No urban of the woodlands yet has anywhere near the canopy cover of a typical healthy native forest in the region ; nor is a forest a place to favor specimen shrubs or specimen trees, for that matter. The round canopy of an open grown specimen is not the forest ideal, but reflects a gardener's or horticulturalist's goal instead. If this forest were a vast expansive, unbroken, and undisturbed tract, then creating openings and some canopy thinning would greatly diversify the habitat and favor desirable shrubs and herbaceous growth as well as canopy reproduction. But urban woodlands are, instead, fragmented and disturbed, with a discontinuous canopy.

Successional species, such as black cherry, black locust, and mulberry, often prevail and it is these species, as well as invasives, which would be favored by thinning, not the more desirable mast species of oak, hickory, and beech.

Critically ill people in need of surgery often must wait until they have recovered acceptably to be strong enough to face the hardships of surgery. An analagous situation is faced in urban woodlands. The 'surgery' these landscapes require -- rebuilding the infrastructure -- will be stressful. New paths are usually needed, drainage must be controlled. These activities, while stressful, cannot be avoided if the landscapes are to be utilized without damage by park visitors. But before this is undertaken, the woodlands' recovery must be initiated.

At the outset, two management priorities are recommended for the forest management team. First, exotics removal concentrating in those areas where they are invading and becoming established, rather than in areas where they are fully entrenched. Second, erosion control should focus on stabilizing all exposed bare soil. The team should be Success Under Stress: Managing & Restoring the Metroforest

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trained in mechanical control of exotics and it is advisable if one team member is trained and licensed in the application of herbicides, although this is not absolutely necessary.

At the same time, the team will require training in conventional planting as well as stabilization techniques, including long straw, jute matting, and dead stout stakes, and using bioengineering techniques of live stakes, fascines, and brush layering to establish new plants. Erosion control and exotics control should be the only major priorities until a much greater degree of stability is achieved.

Where new pathways are proposed, they should be laid out for evaluation and modified in the field as necessary. Large trees along the route may benefit from root pruning as well a prophylactic canopy pruning to compensate for projected root losses.

The margins of all existing and proposed pathways and other features to be reconstructed should be the special focus of exotics control to reduce the presence of invasives available for recolonizing the site. Restabilization of all severely eroded areas should be given the highest priority. Once bare ground is exposed, deterioration typically accelerates rapidly.

Stabilization and exotics control should precede planting for restore diversity, although some planting, of course, will be integral to stabilization.

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GROUND STABILIZATION

Before we can address the issue of restoring vegetation, we must insure that the ground on which the plants are growing is stable. Frequently a manager will want to improve an obviously deteriorating habitat without being aware that serious trampling or stormwater damage is occurring and must be controlled first for restoration to be effective. Soil disturbance is one of the most common sources of stress to urban wildlands and frequently precedes invasion by exotic species. The problems encountered typically include soil loss or erosion, excess fill or the addition of soil, soil compaction, or a combination of the above. In all cases, it is important to address the problems of soil stabilization before attempting to manage the vegetation. There are many sources of ground disturbance which characterize landscapes in the developed corridor.

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STORMWATER MANAGEMENT

Erosion from excessive runoff represents one of the most ubiquitous and costly sources of damage to urban wildlands. A single outfall from a storm sewer discharged on a steep slope can cut a deep gully very rapidly. Many of the stormwater problems observed will originate off site, beyond the boundaries of immediate ownership. People often feel helpless to deal with stormwater, in part because it may require complicated negotiation with adjacent landholders and public regulatory agencies. However, stormwater should be treated as close to the source as possible, that is, not by riprapping the banks of the stream in the park but rather on the property of the development where the excess runoff begins. This will require a willingness to confront problems off-site, effective negotiation, and constant monitoring. Enforcement and upgrading of local regulations should also be pursued by land managers. Sadly, many stormwater management regulations are applied only to new development and are non-existent and unenforced in urban areas, where all runoff is simply shunted to the existing storm sewer, which is, at best, enlarged when it fails to function. Where regulations apply, detention basins are often used to reduce peak discharges by holding water and releasing it more slowly; however, problems can still result if the outfall is improperly sized and located. Stormwater design often focuses on flooding only and the outlet structure may not provide any detention of the smaller but very frequent one or two-year storm which travels through the pipe at high velocities. A graduated outlet structure sized to maintain flows which are no higher than when they would occur if the site were covered with a dense meadow, or even forest for a range of storms, from the two-year to the 1OO-year storm, will provide a much greater degree of protection.

Beyond the visible damage to slopes and stream channels, the natural hydrologic regimen is also altered by poor stormwater management. Water that previously infiltrated into the soil now runs off, failing to replenish groundwater. Streams which once ran year round became flashier, subject to periods of flooding and periods of drying out. Dropping groundwater levels, which reduce the base flow of streams, may also severely impact vegetation. Many mesic species, such as beech and white oak, are dependent upon closeness to water table to weather times of drought, and cannot survive continued lowered water table conditions. If adequate levels of recharge are not sustained over time even larger changes in vegetation are likely.

Correcting these problems goes well beyond the scope of this manual, however, several general recommendations are appropriate.

Stormwater management is best addressed over the entire watershed. The simplest approach usually is to seek multiple solutions at different points, rather than a single cure-all at the point of discharge.

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Look first for solutions which most closely mimic nature's solutions路 those will likely maximize opportunities for recharge. Permeable surfaces such as porous asphalt paving over shallow infiltration beds are an excellent way to achieve recharge as well as detention wherever long-term clogging of the lot can be controlled.

Upland retention ponds can also be designed to provide both open water and marsh habitats while effecting recharge when water levels are high. Both these technologies provide significant improvement of water quality of urban runoff and serve to limit contamination of both ground and surface water. Sometimes simply altering the management of landscapes can effect substantial reductions in run-off. Turf areas, when even only gently sloped, shed water nearly as rapidly as pavement. Conversion of all or part of the lawn to tall grass and wildflower meadow can provide friction to slow runoff velocities and a root system which effects higher levels of infiltration. Tall grass can also serve to inhibit trampling or help confine walking to trails and turf areas. If retaining runoff and maximizing recharge are vigorously pursued in the uplands the problems of erosion in lowland areas will become more manageable. No site is too small; the process is cumulative. Each infiltration trench adds up.

Solutions to the problems of lowland areas should also seek to mimic analagous natural situations. In the course of restorations, typical actions include taking a stream out of pipe rather than put the stream into a pipe, reestablishing a natural meandering channel rather than channelizing a stream and planting trees along the stream corridor rather than removing them.

Occasionally some disturbance to wetlands will be unavoidable and this should, of course, be mitigated to the greatest extent feasible, however it should be recognized that 'created' wetlands are not comparable to natural wetlands and should not be 'traded'. The regulatory process should not be used to facilitate this attitude.

One of the most important roles a designer can play today is to solve site problems in a manner that does not take such a terrible toll on our remaining natural areas. The natural hydrology of each site should be respected, that is it should be preserved in all lowland and floodplain areas and it should be restored where the system has been fragmented. Increases in runoff which are generated by development should be handled in the uplands where the development occurs.

There are several excellent publications which describe the design and construction of marsh and open water detention ponds available from the Maryland Department of the Environment Sediment and Stormwater Division, Tawes State Office Building D-2 Annapolis MD 21401 : #6 Guidelines for Constructing Wetland Stormwater Basins (March 1987). #7 Wetland Basins for Stormwater Treatment: Discussion & Background (March 1987). #11 Feasibility & Design of Wet Ponds to Achieye Water Quality Control (Bruce Harrington, July 1986).

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Also available from the same department are several publications describing a variety of infiltration practices including porous paving and the results of their pollutant modelling programs to date: #3 "Results of the State of Maryland Infiltration Practices Survey" (Kenneth Pesyl & Paul Clement, August 1987) #10 "Infiltration as a Stormwater Management Component (H. Earl Shaver, July 1986). #15 Standards & Specifications for Infiltration Practices (February 1984).

Also of interest concerning porous paving and other infiltration practises is Chesapeake Bay Research/Demonstration Project Summaries July 1, 1984 - June 30, 1987 Virginia Department of Conservation & Historic Resources, Division of Soil & Water Conservation.

There is always concern about the pollutant load when dealing with stormwater and the extent to which either ground or surface waters might be contaminated by different modes of handling runoff. The Nationwide Urban Runoff Program is the most comprehensive evaluation being undertaken currently. An Executive Summary of the Results of the Nationwide Urban Runoff Program PB 84-185545 December 1983 was published by the Environmental Protection Agency, Office of Water Program Operations and is available from the National Technical Information Service, U.S. Department of Commerce.

Beyond reducing runoff as a first priority, there is also the problem of restoring areas which have been eroded and handling runoff on site which cannot be reduced at the source. The goal is to divert small amounts of the load over and over, to effect a substantial cumulative reduction in runoff. This is the opposite of conventional drainage practices in the past which concentrated runoff. Water can be impounded over a variety of landscape types for short periods to reduce the rate and amount of runoff and to effect greater recharge. There are several techniques which can be used, including: temporary shallow impoundments, shallow terraced impoundments, low earthen berms with imfiltration trech, check dams in gullies, check logs on slopes, and path reinforcements.

Woodland slopes can be better protected using temporary shallow Impoundments and low earthern berms with infiltration trenches to retain small amounts of runoff on adjacent meadow and lawn areas. Shallow terraced impoundments can help control flows along sloped sites. Check dams can be constructed in gullies to reduce velocities and redeposit sediment. Where only minor control is required, check logs on slopes can be be very useful.

Stable, healthy vegetation, of course, is the most desirable erosion control and, as a general rule, more vegetation is better than less and diversity is usually preferred. It is the first line of defense. All areas of bare soil in the forest should be revegetated although the vegetation is comprised primarily of stratified woody plants rather than a more uniform ground cover, or turf, or shrub beds.

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Case Study: Runoff Recharged Through Basins Beneath Porous Asphalt Parking Lots At a new world headquarters for a major chemical company to be located adjacent to a stream and beech forest, storm water recharge beds eliminated the need for a retention basin, preserving the natural setting of the site and saving enough land to build another building.The new headquarters building had already been designed with a conventional storm water management system with runoff from impermeable surfaces directed to a seven foot deep retention basin, which would have required excavation of the stream bed and destruction of the adjacent lowland forest.

Andropogon, with consulting engineers T.H. Cahill, designed a new system where recharge beds "leak" storm water into subsoils via gravel filled basins located underneath parking areas paved with porous asphalt.

I I ~ ,

I

Runoff scenario directs storm water runoff to a large retention basin destroying stream and forest.

Recharge scenario directs all storm water runoff to recharge beds beneath the parking lots, preserving stream and forest, and allowing water to seep slowly into the ground.

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Case Study: Runoff Recharged Through Infiltration Trenches at Edge of Parking Lot At an automobile dealership, located on a slope adjacent to a stream valley, uncontrolled stormwater from the parking area had eroded the hillside and was damaging the banks of the stream. The new owners, an oriental rug store, wanted a more appropriate businesss image, and were under community pressure to clean up an unsightly lot. Andropogon redesigned the parking to accomodate the same number of cars, but removed unecesssary paving to create a landscaped setting for he building. To control stormwater, a continuous infiltration trench was dug at the lower edge of the lot and backfilled with broken asphalt recycled from the demolished paving. The trench was topped with a layer of river gravel in order to provide an attractive appearance and areas newly released to soil, planted to grass and trees.The recharge trench has been effective in containing all runoff from the site, during even peak rainstorms, and after 10 years is still working well.

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Before: Blacktop completely covers the site, sloping to the road without any provision for drainage.

After: Reorganized parking area with infiltration trench allows edges of lot to be landscaped.

Success Under Stress: Managing & Restoring the Metroforest

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----

Recharge beds are excavated to porous subgrade and covered with filter fabric. Clean uniformly graded, coarse aggregate is placed in the basin and later "choked" with fines and topped with porous asphalt paving.

Storm Water Recharge Beds

---'==---- Compacted---- I subgrade

Section: Showing recharge bed surfaced with porous asphalt. Stormwater can enter the basin in three ways, through perforated pvc pipe which drain roof surface into beds, through porous asphalt paving and by an open gravel trench at the edge of the parking lot which acts as a backup system if the porous asphalt becomes clogged

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22

The recharge trench during construction, showing the broken asphalt infilland filter fabric linear to prevent fine material moving up from the soil below and clogging the voids.

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Several years after construction, the vegetation is well established and the banks are stable with no signs of erosion.

Storm water is recharged into the subsoil and percolates slowly into the stream.

Success Under Stress: Managing & Restoring the Metroforest

24

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TALI: of ""I$I:路S MILL RUN

by Rolf Sauer To follow the tale simply apply,the numbered captions below to the numbers on the illustration at left.

1. '1'0 remedy parking overflow from nearby developments, make Port Royal Avenue (formerly a country lane) into a four-lane arterial street. Add curb8 and street drains' to assure .that the now thousands of gallons of rain water will not filter into the ground, bur rather go directly into pipes. The word most often used to describe this work, even within the Streets Department, is "abomination." Cost: Just under $1 million.

2. Allow high.density development near the park for maximum detrimental effect. Clear the area of trees, fill in valleys, and direct all rain that falls on parking lots and roofs into pipes. If community objects, cite historical architectural images that imply good taste, or say "you won't even see the building from the road." Get all streets and sewers fully designed before submitting them to the Planning Commission, so that rejection or revisions are impossible. If community objections persist, pull out the old show路 stopping "tax ratable" ploy, but be careful not to mention (or even consider) the in路 creased public costs from traffic congestion, flooding; park destruction, minimal developer assessments for public services, and the dimunition of the quality of life.

3. Tear up the park and put in steeply inclined pipes to increase velocity of flood waters.

4. End job by dumping all this into tiny park streams, which will scour the banks .and send tons of eroded debris downstream. Let the Park Commission take it from here, since they have a miniscule budget and now an uncontrollable torrent of water to boot.

5. Should things become unsightly, what with roads and bridges washing out, turn Wise's Mill Run into a concrete gutter, which both concentrates the water and maximizes its destructive velocity, sending eroded debris right into the Wissahickon. The word moot often used to describe this work, from conservative city engineers all the way up to the Managing Director's Office, is "disastrous:' Cost: Just over $500,000.

6. Dump tons of eroded debris into Wissahickon Creek, so that the creek's width is r~duced to only 10 feet. The Wissahickon will then have to change its course.

7. In changing course, the opposite creek bank will collapse and large trees will fall into the creek.

8. The creek will then start to meander, scouring the other side as well, endangering the stability of l<'orbidden Drive: The final irony of all this is that the sediment will be carried into the Schuylkill River, reducing its depth, and further cost the public recurrent expenses in dredging the harbor for ship passage. Our water quality will also be reduced (note that the city intake for the water we drink is just below the Wissahickon on the Schuylkill).

This not so apocryphal tale is presently on view just above Valley Green along Forbidden Drive. In introducing the capital budget, Mayor Green's wish that our streets should be cleaned and our park grass cut seemed to pale before these more fundamental issues involving millions upon millions of taxpayers' dollars.

This satirical description of the impact of stormwater mismanagement from development located on the plateau above a stream valley, on the forested urban park below, was published in a local newspaper The Chestnut Hill Local, April 9, 1981.

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Case Study: Riprap Swale Transformed into Plant and Animal Habitat After construction of its world headquarters, Andropogon worked with Animal Health Products, a Smith-Kline Beekman company, and their site managers, to develop and implement a 3-year landscape plan for the entire site. This plan focused on solving problems caused by mismanaged storm-water runoff, and on preserving, and enhancing, the unique pastoral charactor, and natural habitats of this 300 acre farm.

Before: Unable to carry the increased load of stormwater after development, existing turf swales were stabilized with unsightly rocks and riprap.

After: Rip rap was removed and swales regraded and treated as a meandering, intermittant, stream. Swale banks were planted with emergents, native wetland grasses, and lowland trees and shrubs.

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-,

Techniques: Temporary Shallow Impoundment Whenever there are open areas such as lawns or pavement, there are likely to be opportunities for impounding surface runoff. the most obvious choices for locating such impoundments are areas where standing water is found during and after a rainstorm and where the existing level of impoundment can be easily increased to provide more retention. Temporary shallow impoundments are essentially broad, shallow retention 'puddles' created either by excavation or by the creation of a low berm to hold back water a! the point of runoff. Downslope water movement will not be eliminated by these measures, but it can be slowed and reduced. While no single impoundment will make that great a diffference, numerous, small, basins throughout a site can make a significant contribution. These shallow depresions can be maintained in a turf grass that tolerates standing water for short periods, such as K31, or planted to a wet meadow of ferns, sedges, rushes and native wetland grasses, or copses of native, lowland trees and shrubs. It is important that runoff does not carry high sediment loads or these small basins will rapidly silt in, however, where surrounding areas are appropriately stabilized, siltation should not be a problem on upland sites.

CREATE SHALLOW TEMPORARV IMPOUNDMENTS BV REGRADING GRASSED AREAS IN LOW TRAFFIC AREAS

Plan: Showing typical temporary shallow impoundment.

SHALLOW TEMPORARV

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Section: Showing typical temporary shallow impoundment.

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26

Techniques: Shallow Terraced Impoundments Where a slope is long and shallow and largely open, a sequence of berms and inflitration trenches can be effective in slowing stormwater movement downslope and recharging it into the ground. The number and spacing of these trenches should be determined on site, and depends on the degree of current erosion, the steepness of the slope and the amount of use. Soil from the trench should be used to build the berm, topsoil should be separated from subsoil and placed on top of the berm, and the trench filled with gravel. The berms can be seeded and allowed to grow up into tall grasses arid wildflowers, if it is desired to keep the hillside open, or planted to successional woody species to form hedgerows. Whatever the landscape treatment, however, increasing the 'roughness' of the ground will slow movement of any water not impounded.

RECHARGE TRENCHES ~-+- PLANTED BERMS

TERRACE

Plan: Showing typical shallow impoundment terrace.

PLANTED BERM SHALLOW IMPOUNDMENT TERRACE GRAVEL RECHARGE TRENCH

Section: ShOWing typical impoundment terrace.

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Techniques: Low Earthen Berm with Infiltration Trench An important level of protection from stormwater runoff can be provided for a wooded slope by the creation of a low earthen berm and infiltration trench, located between the developed portions of the site (on the plateau) and the forested slopes. The berm will reduce the frequency and velocity of overslope water movement and provide limited stormwater retention. It is critical that the berm be placed at right angles to the slope or it will cOi~'/ey water downslope. A trench can also be dug beyond the top of the slope, on the plateau or flatter area, and filled with gravel to create a linear soak pit.

Sediment must be controlled or the trench will silt in rapidly. Soil from the trench should be used to build the berm. Topsoil should be separated from subsoil and placed on the surface.The berm should be seeded and allowed to grow up into wildflowers and tall grasses or planted to ground cover to increase the 'roughness' of the ground and slow movement of any water not retained. Although only a small volume of runoff can be held and recharged in this manner at anyone site, if these measures are employed continuously or nearly continuously along the slope significant protection can be achieved.

INFILTRATION TRENCHES

Plan: Showing low earthen berm with infiltration trench

REGRADE TO FORM A RIM BERM WITH A LEVEL TOP OF NOT MORE THAN 18" HIGH SURFACE IMPOUNDMENT INFILTRATION TRENCH OF NOT MORE THAN 2'-0" DEEP

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Section: Showing low earthen berm with infiltration trench.

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Techniques: Check Dams in Gullies Where gullies have formed, low wooden check dams can be built from tree trunks found on the site and used to reduce the velocity of runofff and encourage the deposition of sediment within the gully. These dams should be small and located at frequent intervals. Their purpose is to reduce the velocity of stormwater which in turn will reduce the capacity of this water to erode. At the same time the check dams encourage the deposition of sediment in the runoff, all along the length of the gully, rather than at the bottom of the slope. It is important to acknowledge, however, that complete gully restoration cannot take place until the quantity stormwater received has been significantly reduced. These check dams must be small enough to permit a flow of water over the dam or new channels will be cut at the sides. These dams must also be located so that the top elevation of the downstream dam is no lower than the bottom of the upstream dam or scour just below each dam will occur. Check dams made from wood found on the site do not typically last more than three to four years and should be rebuilt as needed.

ERODED SWALE

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LOG CHECK DAMS EACH DAM SHOULD BE SPACED TO BACK WATER UP TO THE BASE OF THE HIGHER DAM - INCREASED EROSION OF GULLY WILL OCCUR IF TH IS IS NOT DONE

Long Section: Showing gully with check dams.

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.;::'!'''i~'' "" THE HEIGHT OF THE CHECK DAM ~~~:E:s:i,.~''~"~ SHOULD NOT BE MORE THAN HALF THE DEPTH OF THE GULLY OR GREATER THAN 2"-0"

Cross Section: Showing gully with check dam.

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Techniques: Check Logs on Slopes Where no gullying has occurred, but bare soil and limited erosion are evident, a series of check logs staked along the contours can help control erosion. These low barriers will reduce the velocity of runoff and may retain water long enough to provide some recharge into the ground as well. By trapping both water and sediment, they encourage natural regeneration and provide good sites for replanting, particularly the shrub and understory layers of a forest. The number and spacing of these check logs should be determined in the field depending on the steepness of the slope and the degree of erosion. Slope check logs can also be used as reinforcement, on the downslope side of pathways that are channeling stormwater and currently conveying runoff to the slope.

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NEW SOIL BEHIND 'CHECK LOGS' -

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'CHECK LOGS' PLACED ALONG / CONTOURS TO SLOW FLOW OF WATER /

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Section: Showing side of eroded forested slope with new check logs placed along the contours.

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Perspective: Showing Placement of check logs on steep, forested slope.

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31

Case Study: Restoration of a Forested Stream Valley When failure of a city reservoir accidentally released 150 million gallons of water into a stream valley in Philadelphia's Fairmount park, it severely damaged the stream banks and stream bed, as well as the mature forest, and important historic sites adjacent. Andropogon assessed the damage to both natural habitats and cultural artifacts, and provided a phased plan for restoration of the stream channel and the surrounding lowland forest.

Before: Water from the reservoir scoured out the streambed,in some cases dropping the original level by 6 feet or more. The deepened channel resulted in a lowered watertable which was stressing the older trees during summer droughts.

LINE OF ORIGINAL STREAMBED REESTABLISHED WITH FILL ERODED STREAMBED GEOTEXTILE FABRIC3\ DUMPED ROCK FILL FILL MATERIAL TO BE SIMILAR IN TEXTURE AND PERMEABllITV TO ORIGINAL SOIL NEW COMPACTED FILL LAID IN LIFTS

After: Streambed reestablished at original level with backfill of the same density, texture and porosity. Small rock dams at frequent intervals prevent movement of backfill material.

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Techniques: Gully Stabilization Before any physical restoration of the site is attempted, every effort should be made to reduce the volume of runoff as described in the stormwater section of this manual.

If not all the runoff can be accommodated elsewhere, the amount remaining must be calculated so that the proposed solution can handle the necessary volumes. In this example, a corrugated pipe is installed to carry the runoff down the steep slope directly to the receiving stream and has been sized to handle the 50-year storm. Larger but less frequent storm flows are assumed to flow overland downslope.The gully backfill material should be as close as possible in character to the surrounding soil and must be compacted in 6" lifts to densities which approximate adjacent soils. If too loose, the soil will tend to settle and may continue to convey water outside the pope and erode gradually. Note too that a gentle swale configuration is maintained to handle overflow stormwater. Disturbance of adjacent vegetation and uneroded areas must be avoided during reconstruction. The site should be fenced before any work activity is initiated. A qualified arborist should be used for any pruning or tree removal. It is especially important to ensure that adjacent vegetation isn't damaged by taking large trees down in sections. If work is initiated at the bottom of the slope, the fill can be added in lifts and compacted by the construction vehicles themselves, as they use the refilled areas for access to upper portions of the gully. Care must be taken, however, not to crush the pipe.Temporary sediment and erosion controls on the work site are mandatory and may include silt fencing, hay bales, and temporary drainage swales and detention basins.

WIDTH OF ~WA)..f

18"

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Section: Illustrating techniques of gully stabilization

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Photograph:lllustrating the problems of a gully. Not only are roots exposed and trees toppled, but the velocity and volume of runoff have caused a deep ravine. This ravine is actually deeper than water table at some seasons and establishes a new hydraulic gradient back from the gully across the entire slope. Groundwater is drained away and water taable levels permanently lowered. Sensitive species like beech and oak will gradually die off and be replaced by earlier successional species such as ash and maple which are more tolerant of fluctuating, flashier conditions unless nearly exotics overwhelm this disturbed site.

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35

EXCESS FILL

Urban wildlands are frequently subject to disposal of excess fill. There are a variety of reasons for this; typically, development has already occurred on the flatter well-drained soils, leaving steeper slopes and wetlands in vegetation. As increasingly marginal lands are built upon, fill is used to even out the topography for easier construction. Despite wetlands legislation and regulations to limit construction on steep slopes, you can find hundreds of examples of filling throughout the region, often on sites too numerous and small to demand the attention of enforcement officials. Lots are casually enlarged and roads widened by continuously pushing a little fill over the slope. Even when a legal fill project is conducted, excessive fill and sedimentation off site is still routine. In addition to the direct application of fill, there is a large amount of silt carried in uncontrolled stormwater. Excessive runoff from a storm culvert or road which dead-ends in a park may bring large volumes of silt and debris, which may then erode the banks of a now overloaded stream channel, and later deposit the fill lower in the valley.

The impacts of this fill are severe, but may take years to be fully visible. Ground layer vegetation is covered up and trees and shrubs may be damaged or pushed over by heavy equipment or the sheer weight of the fill. Vegetation which seems to be spared is often also killed, slowly, by the presence of fill over root systems. Different tree species are tolerant of differing amounts of fill; oaks and beech, for example, are notoriously sensitive and may be killed by just a few inches of soil. Box elder and sycamore are especially tolerant and often survive under conditions that would kill other species.

Roots also respire and the added layer of soil inhibits the exchange of atmospheric gases that occur in the upper soil horizons. New roots can extend upward into the fill zone, but this may not be rapid enough to save the plant and will not occur if the fill has been compacted. Toxic gases given off by the roots also accumulate beneath the fill.

The weight of the fill may also be enough to compact the soil, further inhibiting plant recovery. Soil piled against the trunk can also rot the bark and damage the root collar.

The response of trees, for example, to excess fill over their roots is all too frequently visible in new developments, where large trees have been spared the axe, but not the bulldozer. New home buyers are often unaware of what has occurred and are dismayed three years later when their beautiful trees start to drop large limbs, dying in pieces until they have to be removed at considerable cost.

The new fill is usually very poor quality soil, low in organic matter and largely mineral subsoil. This is a poor medium for renewal of the forest and a great place for invasive disturbance vegetation. Frequently bits of exotic plants may have arrived with the fill.

Almost any part of the Japanese knotweed, for example, including a sliver of root or piece of stalk material, is capable of rooting to establish a new colony.

Where fill has been added to flat sites, the surface is often compacted by heavy equipment so densely that it is like concrete. Conversely, fill on a slope is almost always very loose, having been simply pushed over the edge. It erodes and slumps Success Under Stress: Managing & Restoring the Metroforest

36

continuously, making it almost impossible for new plants to become established on the ever-shifting ground.

One of the most difficult questions to answer is whether or not to attempt to remove the fill, which can be a costly and disturbing event in itself. In most cases, even if the bulk of the fill cannot feasibly be removed, some regrading is almost always advisable.

The more recently the filling occurred, the more likely that with prompt removal the existing vegetation can be saved, if it was not cleared or severely damaged during the filling operation. It is advisable to pull some fill away from tree trunks to examine the condition of the bark. Some species, such as sycamore, are more tolerant and will survive years under partial fill, sending numerous adventitious roots out from the buried portion of the trunk. Others, like tulip poplar, are much more sensitive and may show signs of bark rotting after only months of cover. If the trees still appear alive and vigorous and do not show signs of losing major limbs or broad areas of rotting bark, removal of the fill is strongly recommended. Substantial hand labor may be necessary to keep from damaging trees with heavy equipment. As close a grade as possible to the original topography should be reestablished. The regraded area should also be stabilized immediately.

The proper disposal of the fill which is removed is important. Transport is costly and almost anywhere the fill is disposed impacts natural habitats adversely. On site, however, the fill can often be reused to further restoration efforts to refill eroded gullies, as described in the following section.

Overall Guidelines When Fill is Removed If fill can be removed, regrade to original, or at least gentlest slope that can be achieved, without damaging roots of existing trees or disturbing other stable vegetation.

Hand work and raking may be necessary or use the smallest equipment feasible. A small drag line operated from the top of the slope may also be feasible. Even if there are no surviving trees, it may be desirable to achieve a shallower and more stable slope.

Typically, a slope steeper than 3 to 1 of fill soils will be difficult to stabilize. In regrading, heavy equipment can be used if access is available, however, the lightest equipment is preferable to minimize damage to the soil. Once the fill is removed, the ground should be restabilized as soon as possible (see the guidelines for surface stabilization). Where there is inadequate vegetative cover, additional planting may be necessary, as described in later sections.

If the fill cannot be removed, or too little can be removed to save existing vegetation, it may be necessary to remove dead or dying trees along walkways or where they pose a hazard to people or to other areas of healthy vegetation. Otherwise, dead treas should be left in place for their value to wildlife (see section on dead wood). Filled slopes are often easily colonized by exotic invasives; therefore, it is likely that control of exotics will also be required as described in later sections.

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Overall Guidelines When Fill Is Left In Place When fill is left behind it often causes long-term problems of vegetation management.

There are, for example, numerous urban valleys with tons of construction rubble that years after deposition still support only mugwort, common reed, and a few isolated weedy trees. The fill material is usually of very poor composition and may be excessively drained or very poorly drained or both, in patches. The costly addition of a layer of topsoil rarely addresses the real problems though may support a stand of turf for a few years before it starts to deteriorate. As an alternative to simply capping the site with topsoil more detailed investigations of what comprises the fill are usually necessary. The upper three feel of soil usually require some level of reworking which may include mixing in various missing soil components such as sand where the material is too clayey, or organic matter where too little is present or powdered rock where there is no mineral component.

Sometimes the soil is so poor that there is a fine line between fill and debris or trash disposal, which may create more difficult management problems. Junked automobiles and old refrigerators can and should be removed wherever possible without undue disturbance. Indeed, all trash cleanup feasible should be undertaken. Any rubbish left behind is only incentive for further dumping and as with grafitti, the most effective removal is that immediately after the incident has occurred. New dump sites if unattended to may rapidly develop into serious problems and illegal disposal of toxic materials is occurring increasingly often where such activities appear to be tolerated or unnoticed. However, in places, construction rubble may be so mixed in with the fill soil that separation and removal of the rubble component may be extremely difficult and removal of the entire layer too extreme. Such sites should not be expected to support more than the toughest plant communities, at least at the outset. The presence of continuous cover alone will ameliorate extremely bad conditions by loosening soil and adding organic matter over time. Native plants which are volunteering on such sites should be enhanced and typically include sycamore, cottonwood, willow, cherry, black locust, red mulberry, box-elder, white ash, etc. Not until these species are well-established and have had time to modify the site somewhat should major restoration be considered and the goals should be tempered with an awareness of how long it has taken to achieve a satisfactory level of recovery.

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Case Study: Restoration of a Steep Forested Slope For a 30 acre school campus with severe environmental damage and acute access problems, Andropogon prepared a landscape reclaimation program in concert with a site development plan. Construction of a long, shallow, ramp down the hillside created new access to the athletic facilities on the other side of the valley and allowed the highly eroded slopes to be regraded and the ground stabilized. The haphazard parking area on the plateau was reorganized and drained to soak pits to prevent overslope runoff. Overslope dumping was restricted.

Before: Damaged by runoff from parking areas and building roofs as well as dumping, the steep forested slopes were badly eroded and deep channels had formed on the hillside. Aconcrete stairway, linking the upper and lower fields had been undermined when the slope subsided.

After: A new acess ramp on regraded and stabilized slopes connected upper and lower portions of the site.

A newly planted meadow of native grasses was also seeded with native, early successional trees and shrubs to accelerate the return to forest.

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USER ACTIVITES WHICH DAMAGE LANDSCAPES

Innappropriate behavior abounds in the urban wildlands both intentional and inadvertent. Though often very problematic, it is a testament ot the important and exhilarating sense of freedom people experience in parks and other natural areas. The primary activities which directly damage vegetation and disturb the soil surface include the off-trail use of bicycles and vehicles and trampling.

Off-Trail Use of Bicycles & Other Vehicles The off-trail use of bicycles, motorcycles, and all terrain vehicles often goes unnotices.

Enforcement is very difficult, since they are not easily pursued except by another off-trail vehicle which, in turn, also damages vegetation. Bicyclists also have a place in a park system, for example, and often feel strongly that this includes the wooded sites, whether or not they are aware of the damage they cause.

Where off-trail vehicular use occurs, it must be controlled immediately. In park systems a special task force should be appointed to develop a program to control illegal use. The effort should be initiated quickly and widely publicized. Restrictions should be delineated clearly in all signage and park guide materials. The cooperation of organized groups should be sought and it is possible likely that meeting the needs of cyclists elsewhere in the park will be integral to effective negotiation. 'Hot' spots for ilegal use should be targeted for extra security personnel during likely periods of high use.

Trampling Controlling trampling would often make the single greatest improvement to the health of woodlands. This problem is especially severe because remnant forests often occur on steep terrain or poor soils which are easily eroded or compacted.

With the expansion of development, shrinking wildlands are subject to ever-increasing use. Even when there is a path system, many users deliberately avoid the paths in order to have privacy for their activity or simply to experience a sense of greater wildness. A ground plane survey of Central Park conducted in 1982 revealed that over one quarter of the non-turf areas was bare ground, nearly all of it due to trampling or wheeled vehicles. Obviously, the first action to be taken is to determine the cause of trampling and attempt to correct it. In some cases, the problem is lack of enforcement, a failure to control off-trail use of dirt bikes, for example. This requires a concerted effort to regain control of the park, and is essential if stable landscapes are desired and more costly long-term problems are to be avoided. The restoration effort itself will bring additional personnel to the park who serve as a continuous presence in the area, monitoring activities and educating and, augmenting any security forces.

In other areas, trampling may simply indicates the lack of an adequate trail system or the Success Under Stress: Managing & Restoring the Metroforest

40

need to redesign the existing trails. Long-term management concerns must be included in the design process or the new path will only relocate existing problems. Walkers will typically bypass muddy or poorly drained stretches of pathway. Wherever it is desirable to close a trail, it is also important to remove it by restabilizing the soil and replanting. It they remain visible, they will attract a measure of use.

The decline of the landscape following trampling is a familiar scenario: it begins with damage to herbaceous and small woody vegetation. Once exposed, a trampled trail often is well used, and becomes in itself an incentive to further trampling. Often the maintenance of the original paths has been long deferred, which now have deteriorated.

In many places, a desire line is often hard to distinguish from an original path. Until the paths are rebuilt, it is unreasonable to expect the visitor to keep to them. In such a case, restoration of the path infrastructure should be given the highest priority and should precede major replanting efforts.

While this report cannot deal extensively with the design of paths, several general guidelines are offerred.

Overall Guidelines for Paths A path is a balancing act: it offers protection for the ground surface as well as a means to confine pedestrian or vehicular use; but it is also a source of disturbance. Opening a new trail should be undertaken with great care and with recognition that it will have long-term impacts on the landscape and of the maintenance commitment which is entailed. Nearly all paths in urban wildlands are undermaintained and becomes continuous sources of stormwater damage, trash, and exotics. Often deterioration proceeds so far that outlaw trails are indistinguishable from once paved paths. All trails must be monitored and repaired on a periodic basis, adequate to restrict off site damage.

The path surface must be adequate to carry the level of traffic it serves. A dirt trail which is clearly delineated is not eroding and stays dry enough year round, is adequate only in rural areas in areas with light use and no evidence of off-trail use.

Periodic gravelling may be necessary with more moderate use. Where use is heaviest, a paved surface is typically required. Over time, the condition of the trail itself will illustrate the need for a more durable surface or better care.

A hierarchical trail system is often most useful with a main trail accessible to vehicles for maintenance and security purposes as well as to wheelchairs, a secondary trail system for pedestrians only, and a sequence of single-file adventure trails. The latter permit access to special places which walkers consistently favor such as an overlook or pond edge where a larger trail would be inappropriate. Ideally these trails should not look like paths at all but simply be comprised of large stepping stones or wooden rounds which appear like bedrock or smooth stumps yet control ambient trampling.

Bare soil is not an acceptable path surface for an urban park. All bare-earth, desire-line Success Under Stress: Managing & Restoring the Metroforest

41

trails should be eradicated and revegetated and all areas of bare soil should be restabilized. When bare soil is visible anywhere, trampling is undertaken far more casually than when paths are well maintained and erosion well controlled.

The role of vegetation In Influencing visitor movement should be recognized. One of the most difficult aspects of trampling is that much of it is deliberate. People often are attempting to find seclusion in the vegetaiton, for private activities, or simply for the sake of feeling removed from civilization. At other times, people want only to achieve greater intimacy with the landscape, to come closer to the water's edge, for example.

A more subtle aspect of erosion has to do with the psychology of trampling and the kinds of spaces that are provided by the vegetation. Wherever privacy is desired, dense shrub or shrub-form vegetation is sought. Brushy vegetation close to the pathway, rather than confining the walker, actually may serve as an incentive to leave the path. The round bushy, newly planted shrubs seem to discourage trampling for awhile, but once they become head high and serve as a visual screen they attract those who wish to hide behind them and the decline begins. When one site, for example, is pounded into oblivion, it is abandoned in favor of another site, until the former site recovers and is once again used. In contrast, the more open character of the mature forest areas actually affords less cover and is less trampled by those seeking shelter than sites with more privacy.

Most forest management recommendations urge thinning of the woodland canopy, in order to stimulate dense shrub and understory growth. However, this approach poses major problems in woodland areas of metroforest. Where invasive exotic vegetation is established, openings in the canopy are likely to lead to rampant growth of disturbance species, rather than favoring more diverse native vegetation. Secondly, more brushy undergrowth may actually encourage, rather than discourage, trampling by increasing cover for private activities. In a mature native forest, shrub and understory growth is typically relatively sparse, comprised of open-branching spicebush and maple-leaf viburnum, as well as leggy sassafras and dogwood. This more open character in the woodlands would provide both greater visibility and better security. Dense, round shrub mounds should, instead, be confined to planting beds in turf areas, where security is less problematic and plantings more easily replaced.

There are several excellent trail maintenance handbooks available including: Trail Building & Maintenance, 2nd edition. Robert D. Proudman & Reuben Rajala. 1981.

Appalachian Mountain Club (5 Joy Street, Boston MA 02108; telephone: 617-523-0636).

Trail Design. Construction, & Maintenance. William Birchard, Jr. & Robert D. Proudman.

The Appalachian Trail Stewardship Series. 1981. Appalachian Trail Conference (P.O. Box 236 Harpers Ferry WV 25425; telephone: 304-535-6331).

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A pocket size manual is also available: Appalachian Trail Fjeldbook - a Self-Help Guide for Trail Maintenance. William Birchard, Jr. & Robert D. Proudman. The Appalachian Trail Stewardship Series.1982.

Trails Manual - EQuestrian Trails. Charles Vogel. 1982. Equestrian Trails Inc. (13376 Sayre Street, P.O. Box 44135 Sylmar CA 91342).

These manuals are geared to larger wilder areas than many of those found in more urban areas, but the techniques are still applicable, especially where paths are largely unpaved. There is also a sequence of English trail manuals designed for volunteer conservation corps. The series includes numerous topics illustrating the very sophisticated level of maintenance which has sustained a public and private trail network which is in places centuries old. These handbooks are published by the British Trust for Conservation Volunteers, 36 St. Mary's Street, Wallingford, Oxfordshire OX10 EU; telephone: 0491-39766. Compiled by Alan Brooks. The Practical Conservation Handbooks were revised in 1982 by Elizabeth Agate. Titles include: Waterways & Wetlands and Footpaths.

o

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SOIL COMPACTION

Soil compaction can be a very insidious problem, largely because its effects are often underestimated. Any time there is visible soil compaction, there has also been damage to vegetation. Herbaceous vegetation may be killed outright. In heavily used areas, shrubs and small trees may also be trampled to death. However, even trees not directly damaged above ground may have sustained damage in the root zone (which typically extends well beyond the reach of the branches). EXisting roots can be crushed and the soil may now be too tight for new roots to grow. In general, an ideal soil would be around 50% void space and of that space 50% would be air and 50% water. A compact soil typically has too little of both, lacking water and oxygen in the root zone for adequate respiration and growth. Not only are existing plants damaged, but the growth of new plantings can be severely restricted. A great place to observe this phenomenon is on new construction sites, where heavy grading equipment has been used in areas around the building, and were later landscaped without adequate soil restoration. New trees planted often simply fail to thrive. They decline slowly, becoming more mishapen and feeble over time, necessitating frequent replacement.

Where compaction has occurred, it is important to repair the site as quickly as possible or the compacted surface will continue to serve as a barrier to root growth, inhibit the exchange of atmospheric gases, and restrict the infiltration of water. Plants improve soil by adding organic matter and by loosening compacted layers. Without vegetative cover, no organic matter is added and rainsplash action alone, without further trampling, will increase compaction. In combination with air-borne pollutants, an impermeable surface or crust is formed, which reduces the infiltration of water and inhibits air circulation, building up harmful levels of carbon dioxide. The compacted zone must be broken up. There will be few, if any, roots in this layer so no damage to healthy roots is likely if care is taken using a hand rake. The addition of organic matter is nearly always important and may be as simple as adding leaves from nearby. Straw mulch as well as jute or matting is usually the necessary to stabilize the surface until new plants are adequately established. If the mat is then covered with leaves and light brush, all traces of both soil and the repair work can be disguised.

Where continued compaction is unavoidable, it may also be advisable to modify the soil structure to make it less compactible. Where the soil is excessively clayey or silty, the addition of coarse material can make the soilless prone to compaction. Sand is frequently added, sometimes in proportions of up to 30%. This practice also improves drainage which is impeded by heavy soils; however, this may also make the soil excessively drained during periods of drought and therefore the amount added should be carefUlly evaluated. Because water movement is so restricted in a heavy soil, in extended dry periods, this soil is also droughty because moisture is not conveyed upward from groundwater. In some area a fly ash product is used in lieu of sand. The fly ash is sintered; that is, heat treated to render it inert and to improve its texture. Another product that may prove very useful is expanded shale or expanded Success Under Stress: Managing & Restoring the Metroforest

44

slate which is also heat treated to make it quite porous. Because this stone product is porous, it absorbs moisture -- up to 10% or more with expanded shale and appears to improve moisture retention which would be a significant advantage over sand.

Another method which has been proposed for combating the problems of soil compaction entails mimicking the function of the rotting roots of dead trees. After a tree dies, the decomposing roots leave long continuous channels which are like pipes in the upper soil horizons, conveying water, nutrients, and gases downward and serving to counteract compaction. Several researchers have proposed driving numerous stakes into the ground around large trees as an alternative to reworking the soil extensively which would damage existing root systems. Obviously this would be costly to implement over a very large area but might be ideal for selected sites with important specimens.

Combined with breaking up the zone of surface compaction described earlier, the use of soil stakes should be evaluated further.

The demand for composted leaves for renovation efforts always exceeds the supply and will surely grow once woodland restoration begins. In many areas of the woodlands the importation of large quantities of topsoil may be far more costly than adding and mixing soil amendments such a manure, humus, leaf mold, compost, dredge spoil, sand, and expanded slate with existing compacted subsoils.

Powdered rock dust is also worth considering as an alternative to synthetic mineral fertilizers. The depth of fill often prevesnts the soil from gaining nutrients from the action of weathering of bedrock. It should be evaluated in the woodlands as a mineral amendment which can be sprinkled on top of the soil or worked into the soil when stabilization is undertaken.

Large boulders are extremely valuable and should never be simply disposed of. They can be used as aesthetically pleasing rip-rap and to create artificial 'bedrock' surfaces as part of indian-file trails and stream channels, and to provide access to special features such as the water's edge.

Where bare ground has been so eroded that the addition of soil is required, it is usually not necessary to incorporate new material deeply into the existing soil. Where the surface has been compacted, however, it is mandatory to break up the compacted layer completely and stabilize the surface with jute and long straw. Otherwise it serves as an impermeable membrane between old and new soil, preventing roots from growing upward into the new soil and inhibiting water infiltration from above; the new soil and new plantings will never properly knit with the existing soil, leaving the site permanently less stable than was the goal. Because there are no viable roots in tightly packed soil, the risk of disturbance is very low. This layer may only be inches thick, and there is rarely a need to go deeper. Hand excavation and raking is the most appropriate method for this task.

At this point, organic matter and other soil amendments can be added, and if necessary additional topsoil to reestablish the pre-existing grade. In other situations, mulch and Success Under Stress: Managing & Restoring the Metroforest

45

seed, sod or groundcover plantings would complete renovation. However, this is not the case in the woodlands. Because of the heavy canopy, vegetative recovery is very slow.

Reproduction by seed is negligible and vegetatively established plants may take several years to provide adequate cover under dense shade. Therefore, additional protection in the form of an erosion-control blanket is usually beneficial. A three-inch layer of long straw (that is, uncut rather than shredded) covered with jute matting tacked with wooden stakes is a completely organic treatment which provides erosion control as well as a measure of protection from damage should some trampling occur. Jute matting alone is not adequate. When the soil surface is treated in this fashion, uncomposted leaves may be used as organic amendment without worrying that they will induce slippage of the new soil. Both the leaves and the matting with soil will decompose in place, providing additional nutrients. This technique is durable enough that the surface will withstand significant levels of runoff and disturbance and can be effectively implemented before complete construction of drainage structures.

Exotics control should be carried out concurrently and incrementally -- a kind of continuous attack policy. Any area cleared should be replanted immediately, with a straw and jute matting, wherever existing native cover is inadequate to close the gap in a single growing season. The rate at which ground should be opened and replanted should be determined by what can be adequately maintained in subsequent years.

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Case Study: Rehabilitation of Bare Compacted Soil A familar sight in urban woodlands today - bare, compacted, soil from uncontrolled trampling. This area, part of the Richmond National battlefield Park in Virginia, was restored as part of a demonstration project sponsored by the National park Service and given by Robbin Sotir of Soil Bioengineering in concert with Andropogon.

Soil rehabiltation was followed by surface protection and replanting with live stakes.

Where the shade from the forest canopy is too great for plants used in live staking, other replanting techniques such as the use of balled and bagged, bareroot and container material or shrub mats dug from the site, would also be effective.

Before: Uncontrolled trampling has exposed tree roots and destroyed shrub and herbaceous layers, effectively halting all reproduction of native species.

After: Showing the last step in the restoration process. Jute mating has been laid over prepared ground to hold the surface, and held in place with diagonally split 2 inch x 4 inch stakes approximately 18 inches long, called 'stout stakes'. Live stakes have been planted through the jute matting.

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Photograph: Showing zone of compacted soil broken up carefully with hand rakes, taking care to avoid damaging existing roots. Note that where bark has formed on large exposed roots connected to living roots outside the compacted area, they are not recovered with soil or the bark will rot.

Photograph: Showing the addition of organic matter over loosened soil. Loose undecomposed leaves collected in the adjacent woods are suitable as an amendment because the straw and jute cover will hold the surface until the leaves break down. Where leaves are not available, compost, sewage sludge, and peat are acceptable alternatives.

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Photograph: Showing add irian of new top soil where significant amounts have been lost. Note that roots that had developed bark were left exposed. Often the eroded soil can be recovered downslope and returned to its original site Heavy clay soil should be lightened with sand or expanded slate or soil will recompact. Trampling by workers and use of wheel barrows during construction should be confined to a limited area to minimize impact.

Photograph: Showing the use of long straw as a mulch over the rehabilitated soil. Mulch is laid down in a 3 inch layer and used uncut (not shredded) from the bale. Where straw is unavailable, another layer of leaves can be added.

Woodchips should not be used as they are often too "hot' and also deplete the soil of nitrogen as they decompose.

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DEAD WOOD & BRUSH

In an undisturbed natural forest, dead trees and brush play an important role in providing shelter for wildlife and food for a host of insects and decomposers.

In an urban forest fragment, numerous dead trees and large areas of brush may result from a variety of impacts. Filling over the edge of the plateau can kill trees all along the slope. Similarly, a stream carrying greatly increased volumes of urban runoff can severely undercut the edge of the channel and topple numerous floodplain trees. If sufficiently extensive, the resulting debris can inhibit natural regeneration and provide opportunities for the invasion of disturbance species. Because dead wood and brush can be a liability, as well as an asset, it is important for the landscape manager to observe carefully its impact on each site.

As a rule, individual dead trees should be left in the landscape wherever possible. They are used as dens by many animal species and harbor insects and micro-organisms which provide food for many other animal species. Woodpecker populations, for example, have increased dramatically is some places where gypsy moths have killed large numbers of oak trees. A useful guideline would be to leave 3 to 5 standing dead trees per acre for wildlife. Fallen logs and branches are also important to wildlife. Two large and sound logs, in excess of one foot in diameter and 20 feet in length, are recommended and as many rotting logs as possible. Where logs are abundant, some can be moved to other locations where there is too little dead wood. The logs can also be placed on site to help control erosion. Partially submerged logs can be placed along shorelines to benefit fish, birds, and amphibious organisms. Logs in a stream can both aerate water and provide additional habitat. Leaf litter and woody debris can be reused elsewhere to add organic matter to eroded sites.

Occasionally, however, some selective clearing may be advisable to prevent damage to adjacent vegetation or to remove dead trees which pose a direct threat to the visitor, such as along a path. Where numerous trees have fallen, the resulting branch and brush piles can be extensive. Dead leaves and twigs may accumulate deeply enough to severely limit the reproduction of native plants. Vines, especially disturbance species such as Japanese honeysuckle, may establish quickly in the open landscape where the canopy is now gone, heaping over branches and further inhibiting natural regeneration.

Once well-entrenched, vine cover may persist for decades, displacing more diverse native habitats. Over time, such sites may also serve as a source of disturbance species which can invade adjacent landscapes.

Where an open or successional landscape is desired for habitat diversity or wildlife management, a grassland or shrub landscape may be preferable to a vinescape, especially where the vines are predominantly invasive exotics, such as kudzu, Japanese honeysuckle, porcelain berry, wisteria, or oriental bittersweet. Where vines are acceptable, native grapes, blackberries, raspberries, and woodbine should be favored.

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If it is desirable that a forest be reestablished, some removal of dead trees may be necessary and present no unacceptable habitat loss if other snags, logs, and brush are left.

Sometimes brush is deliberately deposited on a slope with the expectation that it will help control erosion. While brush may be temporarily effective in limiting access and discouraging trampling, it rarely reduces erosion. In fact, it can serve to obscure the problem while conditions worsen. It is also unattractive and makes a forest look trashed.

Therefore, all brush laid on slopes should be removed, and more comprehensive restabilization initiated.

A familiar concern with removing dead wood and brush often is disposal. Vehicular access may also be restricted on many sites, making transport from the site difficult.

There are, however many uses for dead wood in on-site restoration efforts including the contruction of check dams, check logs, and soil stakes described earlier as well as to improve wildlife habitat by constructing a wildlife shelter or brushpile.

Small fragments of natural habitat can be very restrictive for small mammals. Snakes where they are more visible and easily attacked. Winter mortalities can also be very high. The construction of a shelter can be especially valuable in reducing mortality due to vandalism as well as winter conditions.

If well-sited, a brushpile can also provide shelter for wildlife. Select a sunny site, preferably away from human activity. Make the pile as compact as possible, laying the larger limbs across the top to minimize wind damage. The brushpiles also improve long-term soil quality and provide habitat for soil organisms.

Where there are no restoration needs, any unused wood can be cut and stacked along any well-used path to be carried away be visitors. This method is often surprisingly effective. Where access is suitable, wood can be chipped for use off-site or as mulch for landscaping purposes. Woodchips can often be suitably disposed of on the path itself in a layer ranging from 2-5 inches in depth. As a rule, however, woodchips should not be simply disposed of in the forest. They can form a suppressive layer of mulch which inhibits herbaceous growth and the reproduction of many species.

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Techniques: Construction of a Wildlife Shelter (Snake Hibernacula) The accompanying plans are designed for a large, sturdy and long lasting shelter constructed with pressure-treated wood and using a backhoe for excavation where access is limited a smaller shelter, hand dug, is still appropriate. Similarly, the shelter may also be built of dead wood on site, however, it will not last beyond a few years. In the most restrictive situations, a simple brushpile located in a sunny spot which consolidates a site's debris is suitable. A wildlife shelter should be located in a field or at a woodland edge which provide the maximum level of sun exposure and minimum of contact with people. It is also important that no valuable vegetation is displaced or damaged by the construction. For the large shelter, a backhoe should dig a trench 4.5 feet wide, 8.5 feet long and 6.5 feet deep. Topsoil and root stocks of existing vegetation should be stockpiled and reserved separately from the subsoil. Lay 2 full length ties on the floor of the trench along the sides. Place 2 of the pre-cut ties on tope of the full length ties, thus forming a rectangle. Secure the ties to one another with large nails; this will keep them together and prevent them from coming apart over a long period of time. Repeat the procedure 8 times so the ties form a box. Fill the opening with stumps, logs, branches and boards almost to the top. 4 inch orangeburg (perforated) pipe (8-12 feet long) may be used as entrance and egress points, one in each compass direction. Cover the top with 6 ties side by side, thus forming the roof. Cover the roof with plastic sheeting or tarpaper to prevent sand from washing down from the top. Stack more logs, stumps, and branches on the top of the ties up to 4 feet high, then cover the pile with the sand that was dug from the trench. Cover the entire mass until the mound is about 6 feet in height. By using railroad ties in the construction of the snake dens (hibernacula), it is predicted they will last up to 50 years or more. Without the ties, the mound would only last 4 to 8 years because termites will eat the pine logs and other wood.A total of 22 railroad ties is needed for each full-size shelter as well as several stumps and branches and soil to cover mound. Cut each of the ties in half (4-foot lengths).

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Cross-section: Showing man-made wildlife shelter/snake hibernaculum The plans and specifications for this wildlife shelter were provided by Herpetological Associates, Inc., 1018 Berkeley Avenue, Beachwood NJ 08722,

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INVASIVE EXOTICS

As soil disturbance is the most visible aspect of environmental damage in the woodlands of the park, the spread of exotic invasive vegetation is perhaps the most pernicious consequence. Planted woodlands and native forests alike can be overwhelmed by exotics and end up looking like overgrown vacant lots, if adequate control is not undertaken quickly enough.

The components of natural habitats found in a region have co-evolved over millennia and produced a natural system of checks and balances. While this does not mean that dramatic change will never occur, the overall vulnerability of a complex community to natural stresses is reduced. The introduction and often widespread dissemination of an alien species, such as Norway maple and Japanese honeysuckle, planted by man into an environment where there are no natural controls or defenses have been devastating.

While it is true that over time natural systems will adapt the presence of a new entity or disturbance, it is also true that this change can decimate extensive areas of native habitat and limit the capacity for recovery in a system already severely hampered by a wide range of other environmental stresses. Indeed, some native pests are exerting a much greater influence now than in the past due to accumulated stresses on the landscape. The diversity and quality of protected natural areas are deteriorating everywhere in the developed corridor along the East Coast.

When kudzu was in vogue, for example, and falsely perceived of as a cure-all for erosion, over 34 million seedlings were distributed from a single government nursery in Georgia. Today, this plant is a menace, renowned for its unparalleled rate at which it swallows up forests and farms alike. Indeed, kudzu, once thought to be confined to the south, has begun a slower but still effective invasion to the north.

Though not all introduced exotic species become invasive, the success of a few species is more than enough to jeopardize virtually every native habitat. Honeysuckle, like kudzu, was once widely perceived as an excellent ground stabilizer. Again, like kUdzu, honeysuckle was on a massive scale with the greatest efforts coming from the railroads, which used honeysuckle to quickly cover steeply sloped embankments. Although growth is rapid and cover seems complete, the long-term results did not warrant this optimism. The vine's shallow, opportunistic root systems do not provide anything close to the level of stabilization of native forest systems. Slumping and soil slippage continue to occur and surface soils are still exposed to erosion beneath the heaping cover. As it matures, it heaps higher and higher over old stems and the number of rooting sites diminishes, with a probable decrease in its capacity to check erosion. Not only does this fail to stabilize as hoped, it has proved to be highly invasive and largely free from the natural controls in their own native habitats. Birds also help disseminate this plant, which produces abundant berries. Because of this, honeysuckle is occasionally Success Under Stress: Managing & Restoring the Metroforest

54

defended as valuable to wildlife. However. this is a very short-sighted perspective.

Plenty of honeysuckle is likely to always be with us. However. the continued loss of habitat diversity will be devastating to birds and other wildlife. In urbanized corridors, it is difficult to find a fragment of habitat that is uncontaminated and in places nearly all narrow strips can be thoroughly infested. And as forests throughout the larger region are increasingly disturbed and fragmented, they are ever more vulnerable to honeysuckle.

Equally invasive are the Norway and sycamore maples, which are gradually taking over many forests in the northeast. Because they do not have the heaping vine form, but look to most people like any other tree in the forest, the evidence of disturbance may be less apparent. In late fall, however, when the leaves from other trees have fallen, the butter-yellow foliage of the Norway maple. for example, reveal a continuous understory of saplings. When these mature. the woodland may be entirely Norway maple, displacing a host of native species. Because almost no other species can coexist with it. the soil is often bare beneath its canopy and subject to erosion.

While vegetation, in general, is usually perceived as providing soil stability, many invasive exotics actually provide very poor erosion control, as compared with healthy native communities or well maintained horticultural landscapes. Norway and sycamore maple have very large and thick dark leaves which emerge early in the spring and typically fall off the tree long after those of the native maples, creating a shade so dark that it severely inhibits ground layer vegetation. Even more problematic is the fact that Norway and sycamore maples are strongly allelopathic, that is, they suppress the growth of other plant species due to the release of toxic substances in the soil. As a result, once Norway or sycamore maple become established, reproduction of other species comes to a halt and the ground beneath them is often totally barren. Without the additional protection of ground layer and/or small tree and shrub vegetation, the root systems of the trees do not provide adequate stabilization. Even more devastating, of course, is the loss of native plant communities or valuable planted vegetation.

There are few other exotic species which appear to pose such a threat to native populations. The widespread dissemination of Norway maple has been accomplished.

Like many other disturbance species, its vigor in our landscape is part of what made it so popular. Until very recently, more than half of the trees recommended for use on city streets by Philadelphia's Fairmount Park Commission were varieties of Norway maple.

Typically, a nursery will have more varieties of Norway maple than all other maples combined. Philadelphia has stopped recommending this tree and some townships discourage its use, but demand for the plant is still large enough to warrant its cultivation on a massive scale.

Japanese knotweed is an even greater failure at site stabilization. Although large in size, often up to eight feet or more height, this plant is actually a stout-stemmed herbaceous plant which dies completely back to the ground each winter, leaving no winter cover. This problem is compounded by the fact that knotweed lacks a fibrous root system, which would provide greater soil stability. Spreading quickly by rhizomes, it Success Under Stress: Managing & Restoring the Metroforest

55

soon displaces other more stabilizing vegetation completely. Given its behavior pattern, it may also be highly allelopathic.

There are, at present, no effective natural controls for these plants. Even though Norway maple, for example, is subject to numerous diseases and pests which create problems in horticultural settings, as yet none has checked its spread in the wild. Over time, it is inevitable that some organism will take advantage of so widespread a host but, in the meantime, extensive areas of native habitat are being decimated and their recovery is severely hampered by a wide range of other environmental stresses.

It is also clear that a very large effort is required to repair the damage done. There are only a few other exotic species which appear to pose such a threat to native populations. Purple loosestrife, escaped from garden cultivation, has overwhelmed wetlands from New York to Minnesota. Its spread is so rapid that a single plant observed is considered an infestation. Even today, new exotic plants are still being pushed as cure-ails exactly because they spread so rapidly.

The future of our native forests may depend on our taking immediate action. The state of Illinois, for example, is considering legislation introduced in 1987, for an Exotic Weed Control Act, to prohibit the sale and planting of problem exotic plants in Illinois.

It is strongly recommended that no species which has demonstrated itself to be a successful invader at the expense of native habitats in the region, or is even suspected of being a pest, be planted at all, because of the threat they pose to the woodlands, planted sites, and regional natural areas. This is a very conservative policy, but the consequences of being too optimistic may be very costly to remanant habitats. Urban wildlands are already severely stressed and it is important not to compound that risk.

This is especially relevant to woodland areas, where it is desired that nature take its course as much as possible.

What makes a plant an exotic invader, instead of a simple garden escapee? It is all a question of degree and context; how fast, how widespread, and most importantly to what extent does it displace native habitats. Appropriate evaluation of exotics requires careful observation of their behavior throughout the region. It is critical to identify what we call 'Huns', those plants which are not only reproducing rapidly in highly disturbed sites, such as vacant lots, but are also making significant inroads in less disturbed areas, such as large woodlots. The most conspicuous trait of a 'Hun' is that it displaces whole communities, not just a few species. No one looking at plants in the eastern corridor, for example, can fail to have observed knotweed and Norway maple. There is already more than enough evidence to alert any park manager to the seriousness of the threat these pose to native habitats.

A ban may seem extreme, however, many of the species are dispersed by birds and quickly traffic over fairly large distances. All are extremely difficult to eradicate once established and none is so critical to landscape character that it cannot be replaced by another less threatening species. Beyond jeopardizing native habitats, invasive species Success Under Stress: Managing & Restoring the Metroforest

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typically represent a significant maintenance drain on more horticultural landscapes and often outcompete desirable exotics as well as indigenous species.

An informative article on the real costs of invasives is entitled, Exotics & their Ecological Ramifications, (1987). Harty, F.M., Natural Areas Journal, vol. 6 no. 4:20-26.

It is strongly recommended that the following species be banned from being planted in the Northeast: Trees: Norway maple Sycamore maple Russian olive Autumn olive Osage orange White mulberry White cottonwood

(Acer platanoides) (Acer pseudoplatanus) (Eleagnus angustjfolia) (Eleagnus umbellatus) (Madura pomifera) (Morus alba) (Populus alba)

Shrubs & Small Trees: Barberry Winged euonymous Amur honeysuckle Tartarian honeysuckle Blunt-leaved privet Smooth buckthorn Shining buckthorn Multiflora rose Rugose rose

(Berberis japonica) (Euooymous a1atus) (Lonicera maackii) (Lonicera tatarjca) (Ligustrum obtusjfolium) (Rhamnus cathartica) (Rhamnus frangula,) (Rosa multiflora) (Rosa rugosa)

Vines: Porcelain berry Oriental bittersweet Japanese honeysuckle Silver fleece vine Kudzu Japanese wisteria

(Ampelopsis brevipedunculata) (Celastrus orbjculata) (Lonicera japonica,) (Polygonum aubertii) (Pueraria lobata) (Wisteria floribunda,)

Herbaceous Plants: Yellow flag iris Purple loosestrife Japanese knotweed

(Iris pseudacorus) (Lythrum salicaria) (Polygonum cuspidatum)

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The control of exotic invasive species is considered in this manual to be one of the most critical management tasks necessary to the conservation of native plant communities.

This is as simple as it might sound. At present, it is not remotely feasible, or necessarily even desirable, to remove all exotics. Some species which are largely confined to areas of severe disturbance such as the tree-of-heaven (Ailanthus altissima), bring welcome green into areas which may be incapable of supporting vigorous native communities.

Instead of eliminating it, we should be grateful for its tolerance of inhospitable conditions.

The approach taken in this manual is to concentrate on the most pernicious species by waging a continuous effort of monitoring and control. The broad goals are to keep undisturbed areas free of invasion and, in areas of moderate disturbance, to incrementally remove exotics and replace them with native species. In the most severely disturbed areas, the objective may simply be to contain the exotics. This approach is not unlike medical triage which identifies those who are beyond assistence, those who do not need assistence, and those who can be helped.

Even when the need to control invasive vegetation, such as honeysuckle is accepted, how to achieve effective results is often unclear or hotly debated. The most frequent conflicts arise over the use of herbicides. For most people, the justification for using an herbicide is the perception that this will require less labor. Managers note that it is important not to devote a disproportionate amount of energy to control a few areas if the invasives are busily spreading unchecked elsewhere, because there is no labor left available. For others, the most intractable aliens, such as Norway and sycamore maple and Japanese knotweed, seem to be simply uncontrollable without herbicides. Some have suggested Japanese knotweed is simply uncontrollable I There is always the danger, however, of overrelying on herbicides.

In a system where pesticide use is more restricted and judicious, limited herbicide management to control exotics might account for only a fraction of the current haphazard and routinely excessive pesticide treatment to support poorly adapted ornamentals. If we give up herbiciding gravel and mulch beds, roadsides, and building margins perhaps some pesticide control of exotics would be viewed as more acceptable.

Because arguments in favor of both sides are strong, we have provided both recommendations for control which are entirely mechanical as well as procedures which include the use of herbicides, but in combination with other non-chemical procedures to minimize the reliance on herbicides. Our guidelines for herbicide use also seek to minimize the volume of chemical used and to maximize the selectivity of the application.

When herbicides are used, it is recommended that you contact an integrated Pest Management (IPM) practioner. This policy seeks to achieve effective control rather than total eradication and to minimize the use of chemicals by employing a combination of methods, inclUding mechanical and environmental controls, such as prescribed burning.

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In response to these concerns, we recommend the following guidelines: 1. Every effort should be made to minimize the use of herbicides. In some areas, any herbicide use at all may be deemed inappropriate, particularly where wildlife might be jeopardized.

2. Wherever herbicide use is being considered, entirely mechanical non-herbicide procedures should be implemented as well and evaluated for effectiveness.

3. Herbicide use should be confined, to the maximum extent possible, to severely invasive exotic species.

4. All management which includes herbicide use should follow the Integrated Pest Management (IPM) approach, which advocates combining herbicides with non-chemical procedures to minimize the reliance on herbicides.

5. The initial management should include at least one mechanical clearance before any herbicide is used.

6. Herbicide use should diminish over time on each site, as initial control is accomplished and more desirable plant communities are established.

Where use has remained high for several years, the management program should be reevaluated.

7. Be consistent and continuous with management. Follow-through is critical. Do not initiate management on an area larger than can be sustained over time. Where prioritization is required, protecting the least disturbed habitats should be given the highest priority.

Zen and the Art of Motorcycle Maintenance (Pirsig, 1974, p. 158) states, "Assembly of a Japanese bicycle requires great peace of mind." We can easily adapt it to say that peace of mind is required in the control of exotic invasives. Persistence and patience, not weaponry, is the key to control. What is important is not how hard you hit the target, but how often. After all, we are talking about plants that have shown themselves to be favored and spread by disturbance. They are all resilient, prolific, and ubiquitous.

There has also been serious concern raised about the spread of several native species, foremost among them the black cherry (Prunus serotina). The 1982 tree inventory in Central Park, for example, revealed that over 19% of the trees in the park greater than six inches in diameter were black cherry, and the ratio was far higher if one includes sapling size trees. This plant is clearly reproducing aggressively. Some have argued that, in the interest of maintaining diversity, this species should be treated like an invasive exotic. There are, however, some important distinctions. A defining Success Under Stress: Managing & Restoring the Metroforest

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characteristic of an invasive exotic is that native species and often whole native communities are literally displaced. The cherries are not invading healthy and diverse landscapes, such as oak and beech forests. At worst, they are reproducing well on sites which were previously turf or tended shrub beds and establishing dense stands which temporarily occupy the space. In many cases, it is not native species they are crowding out, but exotic disturbance vegetation. Perhaps more importantly, the cherries do not preempt the return to native forest. If the exotics could be kept at bay and adequate seed sources for indigenous plants were available, natural succession would gradually replace the cherries with more diverse native vegetation.

In sharp contrast, where Norway maples are established, there is no evidence that native communities would gradually colonize the site, even if the cherries were kept at bay. More than anything else, the cherries are taking advantage of reduced levels of maintenance which permit early successional vegetation to colonize many areas of the park which were formerly tended. Because disturbance levels are high and there is only limited representation of native habitats in the vicinity, only a few natives, all easy propagators, account for a disproportionate amount of new growth. They represent a greater problem in horticultural landscapes, where they grow like weeds, than they do in the woodlands where their reign will be short-lived if more stable forest cover is established. American elm and black locust are similarly prolific and will also be controlled naturally once more forest-like conditions prevail. This, of course, is the critical distinction. Cherries, elms, and black locusts are easily controlled naturally, that is, by other native vegetation. This is not at all true for knotweed and Norway or sycamore maple, which actually control and eliminate native vegetation.

For this reason, the cherries and other prolific natives are not appropriately viewed as a threat to native habitats, but may be deemed as a maintenance problem in the horticultural landscapes. Where they are abundant in woodland areas, it may be desirable to remove cherries and replace them with more diverse native vegetation of greater value to wildlife and scenic character. However, this may not be a recommended course of action, where exotic invasives currently pose a much greater threat. Whenever . trees are cut, it is an open invitation to disturbance species to colonize. First priority should be given to stabilization and exotics control. Once this is accomplished, then selective removals accompanied by additional planting can be considered.

Occasionally it is suggested that native species are more vulnerable to urban stresses.

Unfortunately, however, the exotics which are held up as successful examples often are invasive, causing problems in planted beds and woodlands alike. While the full breadth of native communities is not sustainable in the city, more than enough species survive to create rich and compelling landscapes if appropriately managed. While exotic food sources are also used by wildlife, they do not appear to be necessary to wildlife.

Another aspect of woodland management is that native plant communities, once established, will be far more self-sustaining than the more maintenance intensive landscapes that characterized Olmsted's era. Exotics, however, often become pests if Success Under Stress: Managing & Restoring the Metroforest

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they naturalize well and, if they don't reproduce, they fail to support a naturally self-sustaining system and must be tended and replanted. This is not to say that native communities will be maintenance-free, but that the care required is more appropriately described as management, rather than maintenance, and that the major activites required will involve more repair of damage from use and exotics control than direct horticultural support of the plantings. This is especially important given the realities of the maintenance dollar today and the pressing need for many other maintenance tasks.

Despite the evidence that exotics pose such severe threats and cost so much to control, new species are continuously being promoted on a grand scale. A current example is the Sawtooth oak (Quercus acutjssjma), pushed as potentially valuable for wildlife. It is foolhardy to spread it throughout the landscape and then sit back to see if it naturalizes all too well. Because so little is known about many exotics, it is strongly urged that plantings in woodlands be confined to native species. Where greater diversity is desired, it is worth concentrating effort on reintroducing native species, including the new American chestnut crosses which are being developed currently.

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Photograph: Showing a Norway Maple invasion in this relic urban woodland. Hundreds of Norway maple saplings, still holding their leaves in late fall, dominate the understory. Reproduction by native canopy and understory trees has almost halted, while the Norway maple gradually displaces an entire forest community.

Photograph: Showing Japanese knotweed, Japanese honeysuckle, and silver fleece vine completely displacing the native floodplain forest along this urban stream channel.

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LANDSCAPE MANAGEMENT STRATEGIES: Control of Exotic Invasive Vegetation The two most serious exotic invasive pests in the region are Norway maple and honeysuckle. Both occur most extensively along typical disturbance corridors such as roads, paths, railroads, and the devloped edges, though their distribution is occasionally widespread. The approach taken in this Manual is to wage a continuous effort to control these species. The broad goals are to keep undisturbed areas from becoming infested by monitoring and removing invaders before they become entrenched. Where there is more disturbance and infestation, the goals are to reduce the stresses on the site, and incrementally remove exotics and replace them with native canopy species. In the mostly severely disturbed areas, the objective is simply to contain the exotics. This approach is not unlike medical triage, which identifies those who are beyond assistance, those who do not need assistance, and those who can be helped.

The methods described for these two species may be adapted for use on other pest species. Continuous experimentation and evaluation is mandatory.

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Control of Exotic Invasive Vegetation: Japanese Honeysuckle (Lonicera japonica) Native to Japan, China, and Korea, Japanese honeysuckle is basically an early successional invader, lying dormant in mown pastures and taking a firm hold in woody oldfields. However, it is also found in the light shade of disturbed woodlands. As forests throughout the region are increasingly fragmented, they are more vunerable to honeysuckle, which invades from adjacent cleared areas. Although intolerant of heavy shade, honeysuckle will persist even in the interior of a mature forest as a sparse groundcover.

A trailing and mat-forming vine, Japanese honeysuckle, once entrenched, forms monospecific patches. The rate of spread of the plant varies with the degree of local infestation, the age of the patch, and the amount of disturbance on the site. Widely disseminated by birds and small mammals who eat the berries, once established, honeysuckle can hold a site very successfully by its ability to spread vegetatively -- its long trailtng stems are able to root at every node. Honeysuckle, like kudzu, was once widely perceived as an excellent ground stabilizer. However, when young, although the plant roots frequently, these root systems are small and shallow, and as the plant matures, heaping up over the older stems, the number of rooting sites is greatly reduced and the ground beneath the mound is virtually bare.

Takeover by Japanese honeysuckle creates a static landscape by suppressing reproduction. Because of its ability to climb by twining, the thick and impenetrable mass, produced by the many intertwined stems, inhibit tree and shrub germination and young saplings are strangled and eventually completely covered. If a dense canopy can develop, honeysuckle diminishes and is reduced to a flatter, ground-hugging vine; however, reproduction of other species is still curtailed.

Japanese honeysuckle is semi-evergreen in the mid-Atlantic states, keeping its leaves until late November. As with many other Asian species, late fall is an excellent time to monitor and evaluate the extent of honeysuckle takeover, as these plants remain green after our native plants have lost their leaves, and are then clearly visible in the landscape. In addition, the characteristic heaping form of honeysuckle is so familiar and unbiquitous, it can be easily spotted at any time of year.

Treatment for Eradication Where Japanese honeysuckle has completely overwhelmed a site and no native species are present, a black plastic mulch can be used to kill the plants. Although this plastic is unsightly, it is later removed and involves no herbicides. First, cut and remove the heaping portions of the vines. A blade weed-whipper can be especially useful for cutting the stems. The black polyethylene should be held tightly in place, using staples Success Under Stress: Managing & Restoring the Metroforest

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or stakes. Where appearance is an issue, an open mesh fiber can be used to secure a leaf mulch over the slippery plastic. It may take at least 18 months to adequately control the honeysuckle. When the plastic is removed, complete restabilization of the site is necesssary. An erosion control blanket and/or check logs and additional replanting are usually required.

Where Japanese honeysuckle is mixed with desirable native species, repeated weeding of the honeysuckle will gradually give a competitive edge to the other plants.

However, real diligence is required. These plants must be pulled up gently by the roots when the soil is moist and all runners that have rooted pulled up as well. Although this approach is tedious at the outset, it will provide excellent control over time. Some limited use of herbicides, in combination with removal, can be very effective while reducing the amount of herbicides required.

Similarly, honeysuckle growing in trees can be tackled by severing the stem connections to the ground. Again, a blade weed-whipper is useful or a rachet lopper.

The vines can be left to rot in the trees if appearance is not a problem. An herbicide treatment of the stumps is important, otherwise mechanical removal of a sometimes massive rootstock is the only option.

When herbicides are used, the object is to minimize the use of the herbicide by combining it with mechanical procedures. Several successive cuttings can be extremely effective in exhausting the rootstocks and at least one cutting and removal of the top growth is required before applying the herbicide. Herbicide should be applied only to the places of resurge, where the vine is resprouting, during the active growing season.

Subsequent herbicide applications should function largely as a monitoring operation, catching any recovery sites before new root systems develop.

Recommended Treatment Schedule May -- complete hand cutting and removal of vines June -- complete hand cutting and removal of vines August -- Initial herbicide application October or November -- Follow-up monitoring and herbicide application The honeysuckle vines should be cut to 12-18 inches above ground in May, and again in June, some 4 to 6 weeks before the initial herbicide application. This will allow sufficient time for the remaining vine to resprout new foliage, which will then be treated with the herbicide application. Because the pieces of the stem re-root very easily, vines should not be chipped on site. All cut portions of vine should be removed from the site to eliminate re-contamination. If placed in mulch or compost piles, adequate time must pass before use to ensure enough rotting to prevent introduction of the plant elsewhere, via the mulch.

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Safety Measures The herbicide applicator must be state-licensed and must possess the necessary insurance required by law. All precautions and environmental hazard protections on product labels must be observed. Only labelled herbicides in original containers obtained from the basic manufacturers must be used. Only clean tap water should be used for mixing and rates indicated on the product label must not be exceeded.

The spray must be carefully directed to resprout areas only. Avoid spraying desired plants and minimize spray contact with the soil. To effect selective application, a vegetable dye should be added to the mixture to provide an exact record of the area treated.

The weather during application must be warm, between 75째 - 95째F is preferred, to ensure rapid uptake by the plant. The air must be calm with less than 5 mph winds to avoid spray drift. Do not spray herbicide into or near water.

Recommended Herbicides and Application Rates Herbicide application shall use: "Roundup", applied with a 3-gallon backpack sprayer with 80-02 or 80-03 nozzle. Fill tank 2/3 full with clean water; add 6 fluid ounces or 0.375 pints of "Roundup", and then finish filling tank with water. Mix thoroughly. Apply as a fine spray at a pressure of 40 to 50 #psi to leaves and stems for complete coverage.

After the first year's herbicide treatment, continue monitoring and retreat plants once annually, clearing in June if necessary and herbiciding in August.

Products Glyphosate. "Roundup", (EPA Reg. No. 524-308-AA), as manufactured by Monsanto Company Agricultural Products, 51. Louis MO 63167.

Water based dye, Bulls Eye, as manufactured by Milliken Chemicals, Division of Milliken &Co.

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Photograph: Showing vine control at a disturbed forest edge. Japanese honeysuckle, porcelainberry, and wisteria hang in curtains at the edge of this urban slope forest, where it abuts the developed plateau. Control begins with mechanical removal -. here, a weedwhipper with a saw blade, instead of a nylon line, is used to cut the top growth.

Photograph: Showing top growth being hauled away. In this case the sheer volume of cut vines required a front end loader for removal. Vines must be carefully disposed of as many will root readily from pieces of stem or root.

Photograph: Showing spot application of herbicide after cutting and removal of top growth. Herbicide application is restricted to remaining portions of the plant where regrowth is occurring.

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Control of Exotic Invasive Vegetation: Norway Maple (Acer platanoides)

Native to continental Europe, this invader is one of the biggest threats to the northeastern deciduous forest. Escaped from cultivation in suburban and rural areas, Norway maple can be found throughout the region, displacing complex native forest plant communities with monospecific woodlands.

Prodigious quantities of mobile, windborne seeds, reproduction in sprouting, a tolerance for dense shade, and an ability to thrive in a broad range of soil conditions give the Norway maple a competitive edge over many native species, especially in areas of disturbance. Once established, Norway maple holds the ground for decades, releasing powerful chemicals which inhibit the germination of other species. In forested areas, this species is typically found at the edges and within the interior, following roads, pathways, and erosion channels. However, the vigorous spread of Norway maple is not limited only to disturbed forests. It is so widespread that acres of abandoned fields throughout the mid-Atlantic states have been transformed into monospecific woodlands of Norway maple within a period of 30 to 40 years, precluding the succession of native habitats.

A dense but weak wooded tree, Norway maple is prone to damage by winds and ice and snow loads and rots quickly when wounds are untreated. Like other maples, it is subject to verticillium wilt. Despite its many problems and its invasive behavior, Norway maple is still widely planted and appears on many recommended street-tree lists.

The fall is the best time to monitor and evaluate the extent of Norway maple takeover, as these maples remain dark green when the red and sugar maples are in full color. Only after the native trees have lost their leaves will the Norway maple turn a deep yellow, easily visible in the leafless forest.

Treatment for Eradication Norway maple sprouts vigorously, especially when cut, and can be very difficult to control mechanically, although repeated sprout cutting will eventually kill the tree.

Where numerous seedlings are present, hand pulling is effective in removing them, but the entire root system must be pulled up with the shoot, and ultimately the major seed sources must be eliminated. Convincing an owner to cut down a large specimen tree which is deseminating seeds over a wide area can be an intractable problem. However, recently, a number of horticultural and botanical institutions have taken the lead in efforts to remove seminal trees from their parks and campuses and to restrict the planting of Norway maple in the wider community. Since Norway maple is so aggressive, an approach combining both mechanical and chemical methods appears to be most effective.

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Because of the widely varying sizes of trees involved, two different treatment modes are recommended. In the first, the tree is cut and removed and the herbicide treatment is confined to the cut surface of the stump. This method is called 'notch and frill'. In other situations where it is not possible or desirable to remove the tree, a strip of herbicide in an oil medium is applied to the circumference of the trunk. This treatment is most effective on younger, smooth-barked trees and is especially suitable for treating sites where numerous small saplings have become established. This procedure is less effective on trees over 6 inches in caliper or where a platy bark has developed. It can take several months for death of the tree to occur. Follow-up applications are sometimes necessary. It is critical to monitor treated trees and apply a foliar spray to resprouts.

Using either stump or trunk treatments initially, instead of a foliar spray, minimizes the amount of herbicide used while permitting very accurate application.

Recommended Treatment Schedule Mid-August through September -- Initial herbicide application on trunk or on stump immediately after cutting June through August -- Follow-up monitoring and foliar herbicide application The herbicide application should be timed to effect maximum translocation to the root zone.

Safety Measures The herbicide applicator must be state-licensed and must possess necessary insurance as required by law. All precautions and environmental hazard protections on product labels must be observed. Only labelled herbicides, in original containers, obtained from the basic manufacturers should be used. Do not exceed use rates indicated on the product label and be sure not to exceed the amount of active ingredient per acre specified on the label. This herbicide is an effective killer of woody species; however, it is also extremely dangerous to humans and must be used with extreme caution. Oil impervious gloves should be worn. The basal oil is combustible and should not be used near fire.

To effect selective application, a vegetable dye should be added to the mixture to provide an exact record of the area treated. Warm weather during the application is necessary to ensure rapid uptake by the plant. A temperature between 75째 - 95째F is preferred. For spray applications, the air must be calm with winds of less than 5 mph to avoid spray drift. Do not apply herbicide to water. Effective control will be reduced in wet weather. Lastly, when trees are to be cut, caution should be taken not to disturb adjacent vegetation. For larger trees, topping may be necessary, lowering the upper branches to the ground with ropes.

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Recommended Herbicides and Application Procedure A low volume basal (LVB) control treatment is recommended, using basal oil and a Triclopyr ester herbicide, such as Dow Chemical's "Garlon 4 Herbicide". The oil medium penetrates the bark and woody tissue, transporting the herbicide along with it, permitting a very selective application and the use of less herbicide than a foliar spray, while reducing drift and worker exposure. A dye is also added to clearly delineate the area treated.

A 25% concentration (1:3 ratio) has been found to be effective. One gallon of herbicide should be mixed with three gallons of basal oil and stirred for approximately ten minutes until a clear solution is obtained. Add up to 0.4 ounces of basal dye per gallon of basal spray mix. Shake or stir until the liquid is uniformly mixed. Use a backpack sprayer with a spray wand fitted with a spray system 5500 nozzle and a Y-2 tip to achieve a precise, drip-free, low-volume application. Only a small amount of the herbicidel oil mix should be applied. Lightly spray the lower circumference of the stem, root, collar, and any exposed roots. Do not allow the mixture to puddle or drip around the base. The height of the treated band should be 2 to 4 times the caliper of the tree.

On a cut stump, the cambium layer should be sprayed as soon as possible after cutting as well as the remaining bark and exposed roots to discourage resprouting. Again, puddling and dripping at the base should be avoided. It is unnecessary to spray the heartwood area.

Contact with the cambium layer can be increased with the "notch and frill" method. Use an axe to peel back the bark to allow greater exposure of the cambium tissue.

Products Triclopyr, "Garlon 4 Herbicide" (EPA, Reg. No. 464-546), as manufactured by The Dow Chemical Company, Midland M148640.

Basal Dye, "Automate Blue 8", as manufactured by Morton Thiokollnc., Morton Chemical Division, 333 West Wacker Drive, Chicago, ILL 60606 - 1292.

Basal oil "Arborchem Basal Oil" (Hazardous waste No. 0001 Ignitable), as supplied by Arborchem, P.O. Box 1567, Fort Washington PA 19103.

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FOREST VEGETATION RESTORATION

Replanting is the aspect of restoration that is usually most eagerly anticipated. And just as most people want to start replanting prematurely, before disturbance is controlled, there is also a frequent tendency to want to start at the end rather than the beginning, with the rare and the unusual rather than with the common and the typical. The mortality rate for forest plantings can often be very high making it especially important to assess what is really feasible in any given situation. Perhaps the most difficult task for any manager is learning to 'read' the landscape, to take the cues provided by what is there now about what is likely to work. Ideally the manager also will have been observing the landscape over time while stabilizing erosion and removing exotics. In order to help determine what plants are most appropriate and where, practice the habit of observation.

The most important place to begin is with the existing habitats on the site.

Describe the environmental conditions as fully as possible and the range of native forest plant communities which might be found locally in such environments and how they change over time. If the forest has been substantially modified look for the closest natural analog. Compare the native plant communities in undisturbed areas with those that typify more disturbed conditions. What's the habitat? What are the environmental conditions? What sequence of habitats and plant communities might occur on this site over time? What is succession under undisturbed conditions? How does it change when disturbed?

Look at each landscape, preferably over time, to evaluate what is happening on its own.

Are, for example, canopy species reproducing on their own? If so, where and why? Are there Norway maples competing with the natives? Does the shrub layer need enhancing? Where are shrubs occurring naturally? In what places would new plants experience the least competition from established vegetation. Try to see the landscape changing before your eyes. What did the landscape look like ten years ago? What will it look like next year? Ten years from now? Fifty years from now? How might this be altered with management? Ask yourself as many questions possible about the region in general and the relationship of this landscape to it. Ideally, this exercise should be a dialogue engaging a vareity of different people who are familiar with the site. Go back to the site as frequently as possible and always compare and contrast different sites. Test your observations out with others. There are two journals that are very helpful.

Natural Areas Journal of the Natural Areas Association -- "The Association is a national non-profit organization involved in the identification, preservation, protection and management of natural areas and elements of our natural diversity."Published by the Natural Areas Association, 320 South Third Street, Rockford, IL 61104.

Restoration & Management Notes --"A forum for the exchange of news, views, and information among ecologists, land reclamationists, managers of parks, preserves and Success Under Stress: Managing & Restoring the Metroforest

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rights-of-way, naturalists, engineers, landscape architects and other committed to the restoration and wise stewardship of plant and animal communities." Published by the University of Wisconsin Press, University of Wisconsin - Madison Arboretum, 1207 Seminole Highway, Madison WI 53711 (608) 263-7889.

The single most informative book on learning to observe plant behavior must be Ib..e.

Natural Geography of Plants by Henry A. Gleason and Arthur Cronquist, published by Columbia University Press in 1964. This book has been out of print for years and may require a book search of used bookstores.

Seek out descriptions of regional vegetation such as Vegetation of New Jersey by Murray Buell and Beryl Robichand, Rutgers University Press, 1973 or The Natural Gardens of North Carolina by B.W. Wells, University of North Carolina Press, Chapel Hill, 1967.

A brief recommended reading list is included at the end of this manual.

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CRITERIA FOR FOREST REVIEW & EVALUATION

Configuration One of the most critical aspects of a forest is its configuration. The continuous forest cover which greeted the European settlers has been reduced to fragments and strips in an increasingly developed context. Species composition has been affected, invasive alien species and pests have been widely disseminated, and natural processes, such as fire or rainfall and recharge have been substantially altered. Most endangered is the forest interior and the species limited to that environment. While a popular axiom holds that because forest edge conditions are favored by wildlife (often 'game species'), the creation of more edge is desirable, a more realistic view is that forest edge abounds, while the amount of forest interior is diminishing steadily.

Measurements of the distance into the forest over which edge effects occur are variable, and may range over 300 feet. Therefore, a block of forest 1,000 feet square or almost 23 acres in size can support little more than 3-1/2 acres of interior habitat. A minimum of ten acres of forest is required, roughly circular in shape, to reliably support any interior habitat at all. Clearly then, every effort should be made to minimize disturbance to any forested blocks over ten acres in size. This includes road building and facilities development as well as the clearance of vegetation. Where disturbance does occur, it should be confined to the edges, which are already subject to more disturbance and more accessible to management. Since most disturbance in a forest occurs on the edges, large unbroken forest tracks require the least management of all configurations.

The long-term management of smaller and narrower forested areas, which might not necessarily support interior habitat, is also facilitated by limiting the amount of edge condition created and sustaining a less fragmented pattern. Long-term management costs will be reduced and long-term maintenance of native communities will be fostered.

Continuity Continuity is as important to natural systems as configuration. Islands of habitat isolated from surrounding natural areas experience a decline in native species diversity and are less adaptable to stress over time. Management and proposed alterations in current forest patterns should always encourage, rather than reduce, the continuity of natural habitats. Critical forest linkages should be protected and missing links should be reestablished through management. This is equally important at all scales of the landscape.

Natural Processes A major goal of management is to undertake the least intervention necessary to achieve the desired condition. In all cases, where natural processes regulate and sustain the Success Under Stress: Managing & Restoring the Metroforest

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habitat, the need for outside management diminishes while the health of the whole landscape system is superior.

Environmental conditions have been substantially altered by man's activities over time and severely compromise the long-term prospects for the sustenance of complex natural systems. Some impacts are virtually global, such as the greenhouse effect, must be addressed at every scale at all times. The maintenance of expansive forest cover is somewhat helpful, for example. Others, such as acid rain are expressed more regionally and can be substantially impacted by activities and regulations at the federal and state levels. Still others are operative almost entirely at the local level and the gradual accumulation of negative impacts can be substantially turned around by actions taken on a single site. It is these issues that are primarily addressed in the Management Manual.

Fire The control of fire has been a focus of forest management for so long that many people forget that fire was once integral to the natural processes of the forest. Some areas, such as sandy, barren sites with mixed oak and pine often burned more frequently and visibily, but no forest does not have a fire history. Recent management efforts have concentrated on a rediscovery of the importance of fire to the management of natural areas, as well as to the beneficial effects and relatively low cost of fire as a management tool. Management approaches range from virtually wild fire cycles which are being reinstituted on large tracts where a major conflagration would not pose undue hazard to settled areas to annual winter burns over smaller areas to favor certain game species and reduce the likelihood and severity of wildfire. Ultimately, the goal of all fire management should be to restore as near a natural fire cycle as possible. In most developed areas, light controlled burns limited to restricted sites are probably the most feasible.

The National Park Service recognizes the importance of fire as a management tool.

Consequently, guidelines for the control of wildfires and the management of prescribed and research burns have been developed and are described in Wildland fire Management: NPS 18. Major topics included in this Manual are the identification of roles and responsibilities of governmental agencies, procedures for fire analysis, documentation, and staff training and distribution, as well as guidelines for wildfire control and management objectives for prescribed burning. Local air management regulations vary and should be reviewed. Wherever possible, local fire department should be involved in order to gradually develop a wider network of personnel trained in controlled burning of landscapes.

Highest priority should be given to reestablishing fire in larger forested tracts, especially those which support interior. A pUlsed cycle, with varying intervals of burn, rather than regular intervals, is preferable. For example, annual burning for the first few years in a forest to reduce fuel accumulation and renew herbaceous cover may also stimulate germination of oaks and other woody species. At this point, fire could be withheld to

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allow the new saplings to develop to a sufficient size so that they would not be killed by a light ground fire.

Second priority for fire management should be given to those areas where it can meet specific management goals now achieved with more destructive methods, while maintaining stable cover and reducing long-term management costs. For example, woodland areas currently managed by mowing, which often fosters exotic invasion and encourages erosion, could be managed by fire to form more stable herbaceous and low shrub growth while still increasing visibility.

There are several caveats to fire management. Adequate control of a prescribed burn is dependent on a system of fire breaks, which may include natural features, such as streams and wetlands, or built features, such as roadways and lawn areas. Where new fire breaks are required, careful review is mandatory to ensure that the firebreak does not serve as a route for disturbance, disrupt natural drainage, or otherwise adversely impact the forest. Secondly, particular attention should be paid to the possible hazards of smoke reducing visibility on roadways.

The components of natural habitats found in a region have coevolved over millennia and produced a natural system of checks and balances. While this does not insure that dramatic change will never occur, the overall vulnerability of a complex community to natural stresses is reduced. The introduction and often widespread dissemination of an alien species such as Norway maple and Japanese honeysuckle by man into an environment where there are no natural controls or defenses have been devastating.

Evidence is mounting that restoration practices which foster more natural fire and hydrologic cycles make the natural habitats more resistent to invasion by exotic plants and animals as well as to debilitating diseases and pests, both introduced and naturally occurring. Therefore, management which sustains natural processes and patterns in order to foster a healthy diverse community is the most resistent to a wide range of environmental stresses. The restoration of native shrub and understory layers and the reestablishment of a natural fire regimen appears to be more effective in controlling pine bark beetle, for example, than vigorous eradication and clearance efforts. Unfortunately, past management often has fostered the spread of exotic disturbance species and has tipped the scales heavily against native communities, warranting a concerted effort to mitigate the consequences.

Management is purposeful and has a goal. The goal may be as simple as controlling exotics so that the native communities can develop. But when planting is also a goal, it is important to develop a site restoration model, that is a native habitat which serves a landscape model for each site. It should represent a good fit to the existing conditions with the highest reasonable level of restoration. Examine the continuum of landscapes which might occur and select a moment in time. In a forest landscape in a developed area it is usually desirable to advance in time as most area landscapes are already successional and recently disturbed. It is the older forest there is often the least of. Again, please note that this recommendation conflicts with the frequently heard suggestion to thin the canopy in Success Under Stress: Managing & Restoring the Metroforest

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order to develop continuous shrub or grass cover. The forest is stabilized by a multi-layered system of roots of the multi-layered vegetation above. The ground layer may be patchy, but if relatively undisturbed will sustain protective layer of leaves and organic litter over the soil. Therefore, the object is not necessarily to obtain one very dense layer but to establish a more complex system.

It is notable how often a forest dies from the ground up. First the smaller plants, both woody and herbaceous are trampled. The canopy may be the last to go, declining for years above a trampled, compacted and eroded ground. On the other hand, restoration of a forest usually proceeds from the canopy down, dealing with the smallest plants last.

Where the soil has been disturbed, the use of straw and jute affords surface protection and lasts the several years it may take for vegetation cover to develop. In the meanwhile, where planting is desirable there are several guidelines suggested for reestablishing the forest layers.

Guidelines for Reestablishing a Forest's Layers: 1. In forest landscape, the first priority is trees, in particular establishing a closed canopy. This effects some control over those exotic invasives which are intolerant of shade, or at least less aggresive in shade, while establishing the defining characteristic of a wooded landscape, a closed canopy. In older landscapes, under relic canopy trees or where turf and planting beds have been released under old specimen trees, the most suitable trees are likely to be the same canopy replacement species found in local natural areas, such as the beech, and oaks, and hickories of mesic slopes. The species of temporary forest gaps such as tulip poplar, black birch, and black locust are ideal in small breaks in forest cover.

Where larger discontinuities in woodland cover occur, red maple and ash may be ideal.

The actual site, however, should inform the manager about what species are the most suitable. Remember too, that while the canopy layer is being planted first, a whole community is being established, such as an oak/hickory association with a dogwood understory, and a spicebush shrub layer and woodbine, ferns and woodland aster on the ground. Plant the trees in patterns which have been observed on the site or in analagous habitats, not like an orchard or plantation.

2. Once the canopy is closed, the second priorities are the understory and shrub layers. The understory layer will include smaller, younger canopy trees as well as typical understory species such as dogwood and sassafras. Similarly, seedling size tree species are characteristic of the shrub layer growing beside the viburnum or mountain laurel. The plants should be situated where yOU'd expect to find them naturally. Typically, shrub growth will be more dense at edges in gaps, in damp depressions, and anywhere that disturbance has been limited for a very long time.

3. The re-Introduction of herbaceous and groundlayer plants is probably the trickiest. Expect some mortality. Start with small scale experiments.

Monitor over a long time period. Put each species in the environment you'd expect to find it in naturally and with its familiar associates.

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4. At each evaluation, reassess the need to plant at all based on changes which have occurred in the meantime and the rate at which the landscape Is recovering or deteriorating. As a general rule of thumb, it is preferable to opt for exotics removal and stabilizing bare soil over planting if there is only a limited amount of time or labor available.

5. The following species all of which can be found persisting in urban woodlands are recommended for consideration in the Mid-Atlantic area: Cano~y Trees

Red maple Silver maple Sugar maple River birch Yellow birch Pignut hickory Shagbark hickory Mockernut hickory Hackberry White ash Kentucky coffee-tree Black walnut Tulip poplar Sweetgum Sourgum White oak Scarlet oak Swamp white oak Pin oak Chestnut oak Red oak Black oak Black willow Basswood

(Acer rubrum) (Acer saccharinum) (Acer saccharum) (Betula nigra) (Betula lutea) (Carya glabra) (Carya oyata) (Carya tomentosa) (Celtis occidentalis) (Eraximus americana) (Gymnocladus dioica) (Juglans njgra) (Liriodendron tu!j~ifera) (LiQuidambar styraciflua) (Nyssa sylvatica) (Quercus alba) (Quercus coccinea) (Quercus discolor) (Quercus palustris) (Quercus prinus) (Quercus rubra) (Quercus yelutjna) (Salix nigra) (Tilia americana)

Small Trees & Understory Trees Serviceberry Gray birch American hornbeam White fringetree Pagoda dogwood Flowering dogwood Carolina silverbell Cucumber magnolia

(Amelanchier canadensis) (Betula populifolia) * (Carpinus carolina) (Chjonanthus yjrginicus) (Comus alternifolia) (Cornus florida) (Halesja carolina) (Magnolia acuminata)

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Small Trees & Understory Trees (continued) Sweetbay Black cherry Hop hornbeam Black locust Sassafras Bladdernut

(Magnolia yirgjnjana) (Prunus serotina) (Ostrya yjrgjniana) (Robinia pseudo-acacia) (Sassafras a1bjdum) (Staph lea tdfolia)

Shrubs Speckled alder Smooth alder Buttonbush Redbud Summersweet Silky dogwood Black huckleberry Winterberry Spicebush Flame azalea Pinxter Swamp azalea Shining sumac Smooth sumac Staghorn sumac American elder Meadow sweet Hardhack Highbush blueberry Lowbush blueberry Mapleleaf viburnum Arrowwood Nannyberry Northern arrowwood Yellowroot

(Alnus jncana) (Alnus rugosa) (Cepha1anthus occjdentalis) (Cercis canadensis) (Clethra alnifolia) (Cornus amomum) * (Gaylussacia baccata) (Ilex verticillata) (Lindera benzoin) (Rhododendron calendulaceum) (Rododendron nudiflorum) (Rododendron yjscosum) (Rhus coppalina) (Rhus glabra) (Rhus typhjna) (Sambucus canadensis) (Spirea latifolia,) * (Spirea tomentosa) • (Vaccinium corymbosum) • (Vaccinium vacillans) (Viburnum acerjfolium) (Viburnum denta,tum) (Viburnum lentago) (Viburnum recognjtum) (Xanthorhiza sjmplicissima)

• Restricted to open landscapes and woodland edges The simplest rule is to plant each species in a location most analagous to where yOU'd be likely to find it growing naturally and with other species which would likely be its companions. Lastly, plant each species in a pattern that is specific to that species -- in its own 'footprints' rather than in the more uniform on-center horticultural patterns.

There is always considerable interest in establishing evergreens, both trees and shrubs.

Not only are they aesthetically appealing but they also supply winter shelter for wildlife.

It is, however, important to note that very few evergreens are indigenous to the Success Under Stress: Managing & Restoring the Metroforest

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temperate forest landscape. Air pollution which clogs the leaf's pores is especially hard on these plants which shed their leaves (needles) only every three or so years rather than after only eight months use. Several native species, however, do occur throughout the region and persist in well managed urban wildlands. Hemlock (Tsuga canadensis) is the only shade-tolerant forest canopy species, however white pine (Pinus strobus) can be established in glades and adjacent fields. Red cedar (Juniperus vjrginiana) requires very open conditions, and unlike white pine will not persist in the forest.

American holly Wex opaca), inkberry Wex glabra) and laurel (Kalmia latjfolja) can be established in the forest shrub layer.

We strongly urge that you avoid grafted and vegetatively produced plants insofar as is feasible, especially for live species, with the exception of live stakes. All those patented varieties mean no genetic diversity and many plants will show graft incapatability sooner or later. Trees grown on their own roots are far more desirable and sturdier specimens.

Several methods of vegetation replacement are available including tramsplanting, planting balled and burlapped, bareroot, or container-grown species, establishing plants using soil bioengineering techniques, collecting and/or propagating native species, as well as moving whole blocks of soil with the vegetation still intact on them.

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REPLANTING STRATEGIES

Balled and burlapped (B & B) is the most common planting technique for trees and shrubs in the Northeast. Indeed, many native species which are unavailable in the trade are those which do lli21 transplant well in this fashion such as hickories and sassafras.

Although many species are available B & B, especially in larger sizes, the primary drawback is the weight of the ball which can be a major limiting factor in woodland restoration. Even a relatively small tree ball can be almost impossible for two people to carry any distance. In woodland areas where vehicular access is undesirable or unavailable, this will place severe restrictions on the use of B & B plant material.

Containerized plants are usually smaller and therefore are often more easily portaged to a forest location. Plants may be grown in the pot or be field grown and later potted in containers. All container material should be checked for girdling roots which must be cut before planting. Although the plants are typically smaller, the greatest species diversity is available in containers. This method is ideal for many native species which are difficult to transplant such as hickories and sassafras, as noted earlier, and sumac, black locust and black gum.

Bareroot (BR) trees are dug when dormant, usually late fall or early spring and taken to a cold storage unit where they are kept at temperatures just above freeezing and at a very high humidity. After bareroot trees are dug the soil is shaken and washed from the roots, hence the name "bareroot". Plants are only taken from storage the day they are shipped and kept moist during shipping with wet straw around the roots. Bareroot planting is a convenient method for planting large numbers of small trees at relatively low cost, but bareroot trees have advantages beyond lower cost. Without soil around their roots, plants are lighter and therefore easier to handle.Transport is cheaper and vehicles are not always necessary to bring the material to the site. Individual trees can be handled on site, without difficulties, by volunteers. Bareroot trees are fairly readily available, but only in smaller sizes up to 2 inches in caliper only a limited number of species are suitable for this planting method. Although high losses can occur with bareroot trees if they are stored, shipped or planted improperly, nearly 100% survival is possible when larger sizes (8-10 feet) are used, and where trees are planted early in the spring and watered frequently throught the first season. Species diversities is somewhat limited, however, so this method usually must be augmented with some B & B or container plantings.

The option to collect plants for use should not be overlooked and is a very useful method if appropriately undertaken. Obviously, no native habitat should be depleted or even disturbed enough to require replanting. Nor should rare or endangered species be collected or species which are difficult to transplant. Often, however, plants are 'rescued' from an area being developed and may be relocated to analagous habitats. And whre disturbance levels are generally fairly low, some collection from elsewhere on site may be suitable to revegetate a local disturbance. Small mats of shrubs can often be collectd quite easily.

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An analagous opportunity is contracting with propagators to grow native speices, which are otherwise unavailable. 'Plugs' of native grasses such as switchgrass (Panjcum virgatum) and little bluestem (Andropogon scoparius) are easily produced at fairly low cost as well as 'sods' or 'mats' of shrub and/or herbaceous communities.

Live stakes are living pieces of stems or branches taken from trees or shrubs with the ability to root vigorously from cuttings. These plants, such as black willow, alder or sycamore, are generally successional plants of the lowlands and streamsides. Live stakes, although more familiarly used as part of the arsenal of bio-engineering techniques to stabilize an eroded bank or gully, can also be used simply to revegetate bare, open, wet areas and to accelerate the return of a wetland or floodplain to forest.

Live stakes have many of the advantages of bareroot trees, and are even easier to plant, although species diversity is even more limited. Because there is no soil, weight is not an issue. The plants are light and easy to transport, and vehicles are not always necessary to bring the stakes to the site. Since plant material used for live stakes should be collected locally, the planting costs are very low, as they represent only labor and transportion, both of which can be minimal. Unlike bareroot trees available commercially, almost all the plant species that will grow with this method of planting favor the wettest soils, providing an inexpensive method of revegetating these particular habitats. However, some species, such as poplars, which will grow very successfully when planted as live stakes, survive in extremely dry habitats.

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Case Study: Canopy Replacement Stormwater runoff from a broken conduit draining an overhead highway bridge, had caused severe erosion and 1055 of vegetation in a forested stream valley within an urban wilderness park. Restoration of the canopy layer by bare root planting of native lowland forest species was undertaken by the Friends of the Wissahickon in concert with Andropogon. The work was carried out entirely with volunteer labor.

Before: Showing break in forest canopy where no trees or shrubs are present. This large open area was an invitation to colonization by undesirable exotics.

After: Showing replanting of the canopy trees. Although small, these trees already shade the ground and will quickly provide a complete restoration of the closed canopy.

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Photograph: Showing delivery of bare root trees to the site. Note that 120 trees can be carried by a small pick-up trunk and handled easily by volunteers. During transportation trees were completely covered with a nylon tarpolin and their roots covered with wet straw. Upon arrival, trees were unloaded and stored in the shade, with their roots buried in moist mUlch.

Photograph: Showing roots soaking in liqua-gel a water holding medium. Before planting roots are throughly covered with this soulution, to rehydrate roots and provide material which will release water slowly into the soil after planting.

Before dipping, roots were clipped to remove any broken pieces.

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Photograph: Showing trees after planting. Trees have been secured upright with a single stake, placed directly against the trunk. Both stake and trunk are wrapped together from the bottom upwards with plasticized fiber tree wrap. Although trees here are planted singly, they are placed no more than 4 to 6 feet apart. Other trees were planted in groups of 3 to 5 and placed in a single hole. Well rotted leaves were supplied by the Park System for use as mulch. Trees were watered once every two weeks by volunteers during the summer drought.

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Techniques: Balled and Burlapped Tree Planting

The most common error in planting a balled and burlapped tree is to make the planting pit too small, or too deep. It is essential that the pit should be at least 3-4 11 wider on each side so that the gap around the plant's root ball can be filled with good topsoil or peat. However, the pit bottom should be exactly the same depth as the ball so that no settling occurs later. It is essential that the top of the root ball be at the same elevation as it was when the plant was growing in the nursery to ensure that the roots have the same growing relationship with reference to water and air diffusion and are not subject to the stresses involved with filling or settling. The root ball should be removed from any supporting wire basket before planting, but the plant should be planted complete with it's biodegradable burlap wrap and supporting biodegradable twine. Once in the pit, the burlap and twine should be cut back from the top of the ball to avoid strangling the growth of the trunk. Excess burlap can either be cut off, or tucked into the pit and filled over with the backfill mixturet. Tamp the soil firmly to prevent settling and to remove any large air pockets, but do not over compact. Water plant. Prune up to 1/3 of the foliage if necessary to reduce water stress once the plant begins to grow. This may seem drastic, but is essential since the reduced amount of feeding roots will not be able to support a full canopy. Once the plant is firmly in the pit, it should be staked, as noted on the diagram below, to give support and stability while the tree establishes its on root support. Once the tree has become stable, the stakes can then be removed.

~ PRUNE

,":::..,~ ....::....

FOLIAGE BY 1/3

/ WRAP TRUNK TO FI RST BRANCHES WITH COMMERCIAL TREE WRAPPING PAPER GUY WITH GALVANIZED IRON WI RE USE RUBBER HOSE TO PROTECT TRUNK 8' X 2" X 2" STAKES, MI NI MUM TWO PER TREE,PLACED OUTSI DE PIT, 2'INTO GROUND TOP OF TREE BALL INSAME POSITION RELATIVE TO GROUND AS IN NURSERY

~;:~;>~,~~~~~~~~!::..',',' ,, .';'

'<',

'« ',',',',',',','"" ,'," '.',',',» ',',','.'.'"

FORM 3" HIGH SAUCER AND COVER WITH 2" MULCH CUT AND REMOVE BURLAP FROM BALL UNDISTURBED SUBGRADE TR EE PITS SHOULD NOT BE DEEPER THAN DEPTH OF BALL

Planting detail for a B&B tree, showing ideal planting method. Similar directions can be followed for planting B&B shrubs.

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Techniques: Bareroot Tree Planting Ideally, bareroot trees should be planted as soon as the ground can be worked -early March in the mid-Atlantic states, to take advantage of cooler temperatures and damper soils. Bareroot material should not be planted after the weather turns hot and dry -- this condition can occur as early as May in the mid-Atlantic states. Upon arrival on the site, bareroot trees should be stored in the shade and their roots covered with wetted mulch, straw or compost. As the weather warms these protective measures become increasingly important. Mix a wetting solution such as "Liqua-Gel" with water to form a paste thick enough to cling to the roots. The wetting agent retains many times its own weight of water. Before planting, clip any broken or damaged roots and dip the entire root system in this solution to rehydrate the root system and to maintain an even moisture balance in the soil after planting. To plant, dig a hole approximately the size of the spread root system. Make a small, well compacted, mound of earth in the center of the hole and spread roots over this mound as illustrated. Backfill soil around the roots and tamp to prevent air spaces. Hold tree upright and secure with a single stake held against the trunk with plasticized fiber tree wrap. Mulch with rotted leaves where available. If rainfall is insufficient -- less than one inch of rain a week, water newly planted trees at the rate of five gallons of water per tree every two weeks during the drought. Remove stake and wrapping after one year.

PRUNE UP TO ONE THIRD OF THE FOLIAGE OR AS DI RECTED

PLACE I" X 2" WOODEN STAKE NEXT TO TREE AND WRAP TRUNK AND STAKE TOGETHER WITH TREE WRAP UP TO 4'-0" HIGH

FORM SAUCER OF TOPSOIL 3" HIGH AND FI LL WITH MULCH 2" DEEP ,....- ROOTS LAID OVER OVER MOUND OF TOPSOI L BUI LT BEfORE SETTI NG PLANT

~~~~~~ 'rzwz~~~~ 路

----+~'r'----

FILL HOLE WITH TOPSOIL MIXTURE WELL COMPACTED

~---UNDISTURBED

SUB-GRADE

Detail: Typical bareroot tree planting.

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Recommended Species Uplands: White Oak (Quercus alba) Northern red Oak (Ouercus borealis) Sugar maple (Acer saccharum) Tulip poplar (Liriodendron tulipifera) Lowlands: Red maple (Acer rubrum) White ash (Fraxinus americana) Pin Oak (Quercus palustris)

Nursery Suppliers Princeton Nurseries PO Box 191 Princeton New Jersey 08542 (609-924-1776) Sherman Nursery Company Charles City, Iowa 50616 (515-228-1124) The Buddies Nursery PO Box 14 Birdsboro, Pennsylvania 19508 (215-582-2410)

Products Liqua-Gel (application rate = 4lbs. per 200 trees) E.C. Geiger Box 285, Route 63 Harleysville, Pennsylvania 19438-0332 Plasticized Fiber tree Wrap (1 roll = 4"x50' application rate =1 roll per 4 trees) Phillips 66 "Duon" Blunks 8923 South Octavia Street Bridgeview, Illinois 60455 (312-430-2025)

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Techniques: Shrub Mat Planting Shrub mats can be collected from adjacent sites for woodland restoration where the existing forest canopy creates too dense a shade for the use of native grass plugs or live stakes. To collect, find an area where the shrub cover is thick enough to ensure rapid reproduction and closure of holes created. Shear tops of shrubs before digging to reduce evapo-transporation and make handling easier. Cut a square approximately 2 feet by 2 feet wide, and at least 6 to 8 inches deep, with the shovel tip. The size of a mat is determined by the need to include a sufficient amount of the root systems of the plants to be moved, for these plants to survive and grow, and by the "handleability" of each mat. Where roots are sparse or soil sandy, larger mats will break apart when moved. Upon arrival on the site, mats should be stored in the shade and kept damp.

After the soil has been prepared, dig hole slightly wider, but no deeper than mat to be planted. Add a light sprinkling of peat moss and place mat in hole, replace existing soil around mat edges and tamp carefully.lf mat supply and labor is ample, mats can be butted together to form a continuous carpet. Otherwise, the space between each mat should be no greater than twice mat size. In event of insufficient rainfall -- less than 1 inch per week -- water every two weeks for the first 2 months after installation. If periods of drought occur, continue to water throughout the summer. Do not allow rills and furrows to form as a result of watering.

SHEAR TOPS OF MATS BEFORE DIGGI NG

~

DIGGI NG SHRUB MATS FOR FOR REPAIRING BARE SPOTS

r

TYPICAL BERM SECTION

Drawing: Showing Shrub mat collection and method of planting

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Techniques: Native Grass Planting by Plugs Plugs of Nptive Grasses The most effective method for establishing native grasses on bare soil is by plugs which have been propagated from local stock. Although costly at the outset because it is so labor intensive, this method requires the least maintenance in following years because nearly complete cover is achieved in the first season. This approach is at present still fairly innovative and the plugs are available commercially on a very limited basis. For large area plantings, it is advisable to contract directly with a propagator to obtain adequate supplies at a reasonable price. Arrangements should be made to contract grow this plant material in the fall prior to spring installation. Two-year-old plugs of little bluestem (Andropogon scoparius) in peat pots 2" in diameter and 2.5" deep currently being supplied to the National Park Service by North Creek Nurseries, RR #2, box 33, Landenburg PA 19350; telephone: (215) 255-0100; contact: Dale Hendricks.

Plugs can be seedling grown, or propagated from divisions from "reserved" native grass populations. Collect plants large enough to provide an economical number of plugs, but not so large as to be overgrown and dead inside, approximately 8 inches in diameter, 10 to 30 plugs can be grown from each original plant. Collect stock in early spring before the ground warms and the top growth is still dormant. Plants can be stored for long periods of time, but care must be taken at all times to insure that the roots of the stored plants do not dry out. Cover collected plants with moist burlap and store in the shade until ready to divide. Wash the dirt from the root system, trim the roots and shoots to 1 inch in length, and separate the plant into small pieces -- one big shoot per piece. Set pieces into rooting medium and grow in a greenhouse, in a plastic liner tray in 2 x 1-1/2 inch cubes. Water plants to surround roots and wash out air pockets. Keep soil moist until root growth begins. Cuttings should grow for a minimum of 12 to 16 weeks to ensure a root bound plug. Remove the plugs from the cubes and plant in the same manner as conventional potted perennials. Native grasses are warm weather plants and begin their growing cycle in early summer, so plugs should be planted when the soil is warm enough to get good root growth -- late spring (April/May). Fall planting is not advised because of the likelihood of frost-heaving. Do not allow rills and furrows to form as a result of watering.

Planting should be undertaken with a tree planting bar at one-foot on-center spacing .

Insure soil is firmed around each plant and then mulch to a depth of 2" with weed-free, seed-free, unrotted clean straw. Barley, wheat, or rice straw is acceptable. In event of insufficient rainfall -- less than 1 inch per week -- water every two weeks for the first 2 months after installation. If periods of drought occur, continue to water throughout the summer. Where honeysuckle or invasive exotics were eradicated before planting, continued weeding is required.

89 Success Under Stress: Managing & Restoring the Metroforest

Techniques: Live Stake Planting Live stakes must be cut when the plants are dormant, from December to March and planted no later than one day after collection. Survival rates will be increased if the stakes are planted the same day they are cut. Live stakes should be cut from living stems or branches and should be approximately 1/2 inch to 1-1/2 inches in diameter and 2 to 2-1/2 feet long. Cuttings should have at least two bud scars near the top of the stake to facilitate the growth of new branches. When preparing the stake, remove the side branches cleanly and preserve the bark intact. The top of the stake should be cut off square to provide a flat surface for tamping into the soil and the thicker end, at the bottom, should be cut into a point for easy insertion. Upon arrival at the site, live stakes must be kept fresh and moist -- stored in the shade with their roots covered with wetted mulch, such as straw or compost, to reduce dehydration. Under no circumstances should live-stake plants be left uncovered to bake in the sun before planting. To plant. pound four-fifths of the length of the stake into the ground with a dead blow hammer. A dead blow hammer is a hammer with a hollow head filled with shot, and is used to minimize splitting at the head of the stake.The stake should be placed shoot end up (buds pointed up), root end down. Correct installation is critical -an upside down stake will not grow. Regardless of the steepness of the terrain, live stakes should be positioned at a 45 degree angle to the ground plane, to increase rooting surface. After hammering the stake into the soil, compact soil firmly around the stake where loose.

SHOOT END -- USUALLY THINNER BUDS POINT UP -- CUT END SQUARE

~

./!'~

LEAVE AT LEAST TWO BUD SCARS

;,t ----- 1/2" TO 1 1/2J

DIAMETER

\ ROOT END -- USUALLY THICKER -- CUT END IN POINT

SEVERAL STAKES CAN BE HARVESTED FROM EACH STEM

Drawing: Showing the harvesting and preparing of live stakes.

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LIVE STAKES IN BANK /

LIVE STAKES ON ~ FLAT AREA ~

-~~~~-

\TAKESS::::L: BE PLANTED AT AMINIMUM / OF TWO FEET ON CENTER IN A STAGGERED PATTERN POSITION STAKES AT 45 DEGREES TO GROUND PLANE

LIVE ST AKES ROOTED AND SPROU路

Drawing: Showing live stake installation

Photograph: Showing a live stake removed from the ground after six weeks in order to evaluate growth. Roots are growing on all buried portions of the stake, with the longest roots found at the bottom of the stake.

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HABITAT CORRIDOR NETWORKS

While this report has focused on the management of woodland areas, what occurs in the adjacent landscapes also impacts these sites. No landscape functions independently of its surroundings. In a remnant natural area, disturbance is typically severe at the edges and many sources of stress, such as the spread of exotics, frequently enter from the edges. Large entrenched areas of knotweed, for example, immediately adjacent to the woodlands will spread and continuously require monitoring and maintenance.

More subtle, but just as important, are positive impacts stemming from adjacent landscapes. It has long been documented that diversity diminishes in landsape fragments which are isolated from larger areas of natural habitat. Very positive benefits to each of the woodlands and the wildlife they support could be provided by establishing a network of habitat corridors connecting the woodlands to each other as well as to other more natural areas in a park, such as ponds and wetlands and wildflower meadows. The following general guidelines are recommended:

1.

Provide a continuous corridor of layered forest vegetation with canopy, understory, shrub, and ground layer plants connecting the woodland areas.

2.

The corridors should be no less than 300 feet wide wherever possible, but in smaller systems, narrower corridors of say 100' are preferable to none at all.

3.

A corridor margin of early successional vegetation is recommended, including both shrubs and herbaceous landscapes.

4.

Wherever forest vegetation is not feasible, meadows of native tall grasses and wildflowers with occasional native shrub clumps are preferable to turf as the connecting piece.

5.

Multilayered plantings of horticultural species are also preferable to turf, as long as none of the species is a naturalizing exotic which might run rampant in the less intensively managed woodlands. As replanting is required in these areas, native forest species should gradually be favored over exotics.

6.

Species requiring routine pesticide management should be removed from the wildlife corridors and replaced with native species.

7.

Exotic invasives should be vigorously controlled in the wildlife areas and be given higher priority than elsewhere, except the woodlands themselves.

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8.

Deadwood, both standing snags and fallen logs, is important in the corridors and should be left in place wherever possible.

9.

Contact with human use and high levels of activity should be minimized and should influence the siting of the corridors. Proximity to active recreation and major walkways should be avoided wherever possible.

10. A 300-foot margin around each of the woodland areas should also be managed as part of the habitat corridor system. Exotics control is especially critical here.

Similarly, native plant community types found at earlier stages of succession, from shrublands to native meadows, are desirable.

11. Appropriate signage to designate the habitat corridor is also recommended and will help alert the visitor to the fragile and vulnerable nature of sanctuaries, and establish a more respectful attitude before arrival at the restored woodlands.

12. It is preferable that a pond have a soft vegetated edge wherever its margin meets the corridor network. Where this is not presently the case and only a paved edge is available, large tubs of native aquatic vegetation should be placed in the pond itself. These tubs can be set on boulders to achieve the appropriate water depth.

Appropriate species include sweet-scented water lily (Nymphaea odorata), bullhead lily (Nuphar yarjegatum), arrowhead (Sagjttada latjfolia), pickerel weed (Pontederia cordata), and blue-flag iris (Iris versicolor), among others.

In addition, dense thickets of native wetland shrub species, such as sweet pepperbush (Clethra alnjfolia), buttonbush (Cephalanthus occidentalis), highbush blueberry (Vaccinium corymbosum), winterberry (Ilex verticjllata), and waxmyrtle (Myrica cerifera), can also be planted in larger boxes set in the pond edge where they will be protected from human disturbance. As these species also tolerate drier conditions, additional plantings in the adjacent uplands will enhance the vegetated corridor and should be augmented with groves and thickets of lowland trees, such as tupelo (Nyssa sylyatjca), walnut (Juglans nigra), butternut (Juglans cjnerea), sweetbay magnolia (Magnolia virginiana), and speckled alder (Alnus rugosa).

13. Additional wetland habitat can, in places, be created by storing stormwater runoff in depressions and swales in the habitat corridors. For example, where a low-lying turf area is being converted to meadow to complete a missing link in the corridor network, it may be desirable to regrade the area to trap and retain runoff to create an intermittent wetland, either herbaceous or woody.

14. Small stands of evergreen vegetation should be established at reasonable intervals along the corridor's length averaging no more than 300-500 feet apart.

Species suitable beneath forested canopy include hemlock (Tsuga canadensis), American holly Wex opaca), inkberry (Ilex glabra), and laurel (Kalmia latjfolia).

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White pine (Pjnus strobus) and red cedar (Juniperus vjrgjnjana) require more open landscapes to become established and can be used in meadow areas.

15. Native vines are especially desirable in the habitat corridors. Virginia creeper (Parthenocissus guinguefolia), grape (Vitis spp.), poison ivy (Rhus radicans), and catbrier (Smilax spp.) are all high value wildlife foods and the latter two also help discourage pedestrian traffic.

16. The landscape character of the habitat corridor network should be integrated with the overall design character of a park and should not conflict with other scenic and aesthetic goals. These are managed landscapes, not simply areas where nature is left to run wild, and a naturalistic character compatible with its surroundings is desirable.

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RECOMMENDED READING LIST

PLANT ECOLOGY, HUMAN ECOLOGY & GENERAL ECOLOGY Changes in the Land William Cronon Hill and Wang, New York, 1984

Communities and Ecosystems Robert H. Whittaker Macmillan Co., New York, 1975

Deciduous Forests of Eastern North America E. Lucy Brown Hafner Press, New York 1974

Ecology Robert E. Ricklefs Chiron Press, Portland, 1973

The Ecology of Invasions by Plants & Animals Charles Elton Methuen & Company, Ltd., London, 1958

Fire in America: A Cultural History of Wildland and Rural Fire Stephen T. Pyne Princeton University Press, Princeton, 1982

Fundamentals of Ecology Eugene P. Odum W.B. Sanders Company, Philadelphia, 1971

Landscape Ecology Richard T.T. Forman & Michel Godran John Wiley & Sons, New York, 1986

The Life of the Forest Jack McCormick Our Living World of Nature Series McGraw Hill, New York, 1966

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Man in Adaptlon: The Cultural Present Yehudi Cohen Aldine Publishing Co., Chicago,1968

Man's Role In Changing the Face of the Earth Volumes I and II eds. Sauer, Bates, Mumford University of Chicago Press, Chicago, 1956

The Natural Gardens of North Carolina B.W. Wells University of North Carolina Press, Chapel Hill, 1967

The Natural Geography of Plants Henry A. Gleason and Arthur Conquist Columbia University Press, New York, 1964

The Oxford Book of Trees A.A. Clapham and B.E. Nicholson Oxford University Press, London,1975

pine Barrens: Ecosystem and Landscape Richard Forman Academic Press, New York 1979

Reading the Landscape: An Adventure in Ecology May Theilgaard Watts Macmillan Co., New York, 1963

Rebuilding Central Park: A Management & Restoration Plan Central Park Conservancy The Arsenal 830 Fifth Avenue, Room 103 New York NY 10021

Vegetation of New Jersey Beryl Robichaud and Murray Buell Rutgers University Press, New Brunswick, 1973

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MAGAZINES Landscape Joyrnal eds. Darrel Morrison/Arnold Alanen University of Wisconsin Press, Madison, 1981

Natural Areas Joyrnal Pub. Natural Areas Association 320 South 3rd Street Rockford IL 61104

Restoration & Management Notes ed. William R. Jordan III University of Wisconsin Press, Madison, 1983

PLANNING, DESIGN & VEGETATION MANAGEMENT Art into Landscape. Landscape into Art A.E. Bye PDA Publishing Co. Mesa Arizona, 1983

Bioengineerjng for Land Reclamation and Conservation Hugo Schiechtl University of Alberta Press Alberta, Canada, 1950

Design With Nature Ian L. McHarg The Natural History Press Garden City, New York, 1969

Garden Design Peter Shepherd Design Center Publication McDonald & Company, Ltd., London, 1969

The Granite Garden Anne Whiston Spiro Basic Books Inc. New York,1984

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The Making of the English Landscape Hoskins Penguin Paperback

The New Jerusalem. Planning and politics Arther Kutcher Thames and Hudson ltd. , London, 1973

New Lives. New Landscapes Nan Fairbrother Alfred Knopf, New York, 1970

The Oldest Road. An Exploration of the Ridgeway JRL Anderson and Fay Goodwin Wildwood House, London, 1975

The Oregon Experiment Alexander, Silverstein, Angel, Ishikawa and Abrams Oxford University Press, New York, 1975

A Pattern Language: Towns - Buildings - Construction Alexander, Ishikawa, Silverstein, etc.

Oxford University Press, New York, 1977

Townscape Gordon Cullen Reinhold publishing Corp., New York, 1961

PHILOSOPHY The Aquarian Conspiracy: Personal & Social Transformation in the 1980's Marilyn Ferguson J.P. Tarcher, Inc., Los Angelos, 1980

Earth Keeping: Christian Stewardship of Natural Resources ed. Loren Wilkinson Wm. Eerdmans Publishing Company Grand rapids, Michigan, 1981

Love & Death In the American Novel Leslie Fiedler Criterian Books, New York, 1960

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Nature and Madness Paul Shepheard Sierra Club Books San Francisco, 1982

Speaking for Nature Paul Brooks Houghton Mifflin Co. Boston, 1980

The Subversive Science: Essays Towards an Ecology of Man ed. Paul Shepard and David McKinley Houghton Mifflin Co., Boston, 1964

The Turning Point: Science. Society & The Rise in Culture Fritjof Capra Simon & Schuster, New York, 1982

The Uses of Enchantment: The Meaning & Importance of Fairy Tales Bruno Bettelheim Alfred Knopf, New York, 1976

DRAWING Drawing: The Natural Way to Draw Kimon Nicolaides Houghton Mifflin Company, Boston, 1941

Drawing on the Right Side of The Brain Betty Edwards J.P. Tarcher, Inc., Los Angelos, 1979

PLANT IDENTIFICATION A Field Guide to the Ferns Boughton Cobb Houghton Mifflin Co., Boston, 1956

Grasses: An Identification Guide Lauren Brown Houghton Mifflin Company, Boston, 1979

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Ground Covers for Easier Gardening Daniel Foley Dover, New York, 1961 Manyal of Woody Plants Michael A. Dirr Stipes Publishing Company Champaign, Illinois, 1975 Native Trees, Shrybs and Vines for Urban & Rural American Gary L. Hightshoe Van Nostrand Reinhold Co., New York, 1988 The Tree Identification Book and The Shrub Identification Book George W. D. Symonds Wm. Morrow, Co., New York, 1958

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