The Breck Fens

TRANSACTIONS THE BRECK FENS S. M . HASLAM

(Botany School, Cambridge*) Introduction THE Lark, the Little Ouse, and the Wissey, are all rivers flowing westwards through the Breckland to the Fenland, and the fens associated with them and their tributaries were called the Breck fens. The fens on the Little Ouse and its tributaries in the region of fertile sands east of the Breckland form a unified group with the others, and these, together with those at the head of the Waveney (which has a joint watershed with the Little Ouse but flows eastwards) are also termed Breck fens. Little of the work covered by this paper however, was done in the Valley of the Wissey.

There are fens around the main sources of the Little Ouse and its tributaries. These sources consist of many small springs or seepage areas and the extent of the fens is detcrmined by the relief, the land rising round their edges. Above Thetford the Valleys alternate between broad and flat, with peat, and narrow, without it.

Below Thetford the Valley is continuously broad. Similarly the Lark Valley is continuously broad below Lackford, and has intermittent alluvium above it. Fens at the sources of streams are called hcadwater fens, and those in the main parts of the Valleys, Valley fens, the two differing markedly in soil and Vegetation.

The underlying rock is principally the Upper Chalk. This comes to the surface only in the Feltwell-Methwold region and in a small area near Mildenhall, and its main effect on the fens is to provide highly calcareous water, to determine the position of emergence of springs, and to give an easily drained substratum.

The soil type above this (whether Breck sand, or fertile sand, etc.) has no effect on the fen Vegetation—except very locally, on shallow peat at fen edges. *Now at Biology Department, Royal University of Malta.

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History and E c o n o m i c U s e Most of the early colonisation was near the rivers and fens.

Neolithic finds are especially abundant in the Lark Valley between Mildenhall and Lackford, the Eriswell Lode Valley, and the Little Ouse Valley between Brandon and Santon Downham.

Bronze Age finds are commonest in the Lark, Eriswell Lode, and Wangford area, though later ones are distributed more evenly throughout the area (Fox, 1923).

Domesday book (Darby. 1952) records meadow along the Lark, Little Ouse, T u d d e n h a m Mill stream, Eriswell Lode, and in the Wangford area, though with less along the Little Ouse than along the Lark (as at the present time). While there are only a few records of pasture, e.g., near Thetford, pasture is not regularly mentioned in the survey. It is noteworthy that the drainage and reclamation of the Valleys had been considerable by this early date.

T h e rivers were extensively used for fishing, fisheries bemg recorded in most parishes, as also were mills.

T h e rivers were canalised for bärge traffic in the seventeenth Century, the Lark up to Bury St. Edmunds (in 1600, Butcher, 1941), and the Little Ouse to Thetford (soon after 1670, Clarke, 1926).

T h e most important effect on the Vegetation was that flooding by silty floodwater in winter was decreased or stopped. T h e draining of the Fenland also started in the seventeenth Century, the main eastwards drains being cut 1605-1623, and 1821-1852 (Darby, 1940). This would have tended to lower the water table in the Breck fens, and the easier drainage, coupled with the Enclosure Acts of the late eighteenth and early nineteenth centuries, would have increased the area put down to pasture.

T h e early O.S. maps (c. 1824) show that the total area of " wild " Vegetation—i.e., fen—was similar to that of the present time.

T h e changes are principally a decrease in the area of what are now wet fens, and the appearance of dry fens consequent on abandoning grass fields, these fields being scattered all over the region. Similar information is provided by the Tithe maps (c. 1840). T h e distribution of duck decoy ponds and Washlands (for taking floods) indicates the water level was then higher than it now is.

T h i s conclusion is confirmed by the c. 1906 O.S. maps, which record considerable areas as " liable to flooding " which do not now flood—even in 1958—and various springs which no longer exist. T h e present dryness of much of the surface peat in normal weather and the scarcity of peat formation, provide further corroboration.

In one fen the water table dropped from several inches to several feet within living memory (Eriswell Lode fen : M r . J. Peachey of Holywell Row). Local Floras, etc., of the last Century show that many marsh and fen species have since decreased in abundance, e.g., Carex paniculata, Typha spp,

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Drosera spp, Eriophorum angustifolium, Parnassia palustris (Trimmer, 1866 ; Hind, 1889 ; Bunbury, 1889) ; Saxifraga granulata was noted slightly later as dominant in the peat-dry land transition on the Suffolk border (Wallis, in Marr and Shipley, 1904) : this species is now uncommon. This again shows the lowering of the water table.

In the early nineteenth Century some skirt lands were levelled by moving sand from high ground into " moor pits " (Fox, 1923), which produced some of the present mixed sand and peat soils at the edges of fens.

Patterns of drainage have varied. Early work apart from the river Channels, etc., has been lost, but several different types remain, depending both on locality and on type of water table in the fens. In headwater fens, where springs arise, there may be a single main Channel into which any side streams flow (e.g., Redgrave and Lopham fens, Wangford fen*, Weston fen), or side ditches leading to a river, or a complex system of side ditches and main Channel, as in t h e higher reaches of t h e Eriswell L o d e .

Here the Lode forms the main Channel, but a carefully arranged network of ditches, often with sluices, was apparently designed to maintain the water table at a suitable level for exploitation of the fen. The system has been discontinued some time. In valley fens the drainage is by ditches along the edge of the Valleys and ones crossing from these to the river. On each side of the tow path there is usually a ditch, into which the water drains, which itself drains into the river at intervals, sometimes through sluices or pipes. In this way the rivers are separated from the water table in the fens. This is shown clearly when the rivers are controlled by sluices, etc. The river level may be considerably above or below the fen water level, but variations in river level have no effect on the variations in fen level, as e.g., in the Icklingham-Tuddenham region of the Lark. This region also has the remains of an older drainage system in which there were double ditches at the edge of the Valleys running along the contours—the present drainage ditches are straight and single.

Each parish adjoining fenland had a Poor's Fen, these being often those parts of the parish which it would be most difficult to drain. Peat was the fuel of the villages until the Coming of the railways brought cheap coal in the mid-nineteenth Century, and it was taken largely from these Poor's fens. In some it was cut in rows, e.g., Cavenham and Hopton Fens, and in others the whole surface was lowered, e.g., Icklingham Poor's Fen. High ground was necessary for the removal of the peat. In some fens trackways were left on high peat levels, e.g., Icklingham Poor's *The fen here designated Wangford fen is that Poor's fen of Lakenheath which is sited in the Wangford region.

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Fen, and in others soil was moved into the fen to form a higher trackway, e.g., fen at head of Eriswell Lode. Carex elata peat was cut with its " hair " (Vegetation) on, and was considered less valuable than that of Cladium mariscus and Phragmites communis (Mr. Peachey, Holywell Row). Past peat cutting is also shown by the names of fens, e.g., " Turf fen " Tuddenham, " Turf fen " Lakenheath, " Dolvers", etc. Peat cutting continued locally until fairly recently for out-of-door purposes.

Reeds (Phragmites) were probably the second most important produce of valley fens, being widely used for thatching. This also has almost ceased ; it ended about forty years ago in Cavenham and Tuddenham Poor's fens (Mr. Grimwood, Tuddenham), and where reeds are now cut they are more likely to be used for litter (e.g., a stand with Phalaris arundinacea and Glyceria maxima near Brandon).

In the lower reaches of the rivers, some parts of the Valleys were frequently cut off from the rest by banks, and used as Washlands for winter floods, which were thus localised on a small part of the area. T h e Washlands are now reduced, and the area actually in use is very small, owing to the lowering of the water table and the improvement of the drainage.

T h e fens also had other uses, osiers were cut for various purposes (e.g., at Tuddenham) as was litter, principally from Cladium and Phragmites stands but also from others ; and Carex paniculata tussocks were cut (old C. paniculata hassocks are still present in All Saints Church, Icklingham).

Apart from occasional cutting, the principal economic use of the fens at present is for the planting of poplars in valley fens (Forestry Commission). This planting has been mainly since 1955 in dry fens with herbaceous Vegetation. Since this Vegetation dies down in winter, access and planting is simple. T h e shade cast by the young trees is beginning to affect the Vegetation, and the most characteristic and abundant plant Community of the Breck fens in 1956—Epilobium hirsutumn—Urtica dioica—Galium aparine—Filipendula ulmaria—will presumably be scarce in the near future.

There is a little grazing, mainly in headwater fens since these usually have shorter Vegetation than valley fens, e.g., Weston Fen. Some fens are burnt, but fires are less frequent than they were ten years ago. Burning also was almost confined to those headwater fens in which low Vegetation gave easy access. Grazing by deer is occasionally noticeable, as is also damage to above-ground reed buds by water rats.

In late winter large mole heaps are thrown up in many dry fens, causing local disturbance.

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Two areas have suffered from a recent lowering of the water table. The largest of these is the area around the new Lark Cut. Unlike the Channels of the rivers themselves, the water level in this cut has not always been isolated from the surroundings, and the consequences to the fen Vegetation have been serious. The fen at the head of the Eriswell Lode, which had the best-grown communities of Schoenus nigricans, of Cladium succeeding Schoenus, and of Carex elata, has suffered particularly, most of the wet fen species being in poor condition or dead.

The smaller fall in water table is in the Redgrave and Lopham fens. Here the Schoenus dominated Community deteriorated sharply, but recovered in 1965, so that Schoenus shade which was formerly light because of burning, is now considerable—and wet fen species such as Drosera spp, Sphagnum spp, Pinguicula, orchids, and Erica tetralix, have diminished or disappeared.

Soil and Water Table The Breck fen soils ränge from soft organic muds and clays to and fibrous peats. In Valley fens the inorganic content is high, owing to deposition of silt in the past, and the soils are silty Phragmites peat or silty organic muds and clays. Bands of clay (containing fresh water shells) are found in the middle of Phragmites peat in, e.g., the Icklingham region, indicating past changes in water level. Now, the water level is too low for any significant accumulation of peat. Headwatcr fen soils, with no source of silt, have a low inorganic content, and are usually lake muds, with some Cladium and Carex peat (e.g., Tallantire, 1953, 1954). Physical differences in soil type have no apparent effect on the vegatation, but chemical differences are of major importance (see below and Haslam in press). The deeper soils have a consistently high pH (6-7-3) owing to the underlying Chalk. (On peat 5-20 cm. deep above acid sand the pH may be low).

Large springs arise in the chalk, e.g., Mitchell Head, Caudle Head. These have fast-flowing water, and no accumulation of peat. Small springs, however, are present in all headwater fens, usually near the outer edges. In spring-controlled water tables in these fens the water level is usually maintained near ground level (there being good drainage) except in times of drought. Subsurface run-off may be channelled via Valleys leading to the fens.

Ditches, if plentiful, can do much to stabilise the water level.

Naturally, with more efficient drainage, effects of rain disappear faster, e.g., after one summer thunderstorm the average water level rose by 10 cm. in a headwater fen, by 16 cm. in a valley fen with a slight spring, ditches and channelled run-off, and by 23 cm. in a Valley fen without these. Two days after a similar storm the level had fallen 5-10 cm. in the first fen, 2-6 cm. in the second, and not at all in the third, where sub-surface run-off was just

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reaching the lower part of the fen. In general the water tables are more variable in summer than winter, partly because in Breckland summer rains tend to be in heavy storms, and partly because of the continuous lowering of the level by evaportranspiration in summer.

Variations in type, as well as in height, of water table are important in determining Vegetation, e.g., Schoenus is dominant in spring-controlled water tables only ; alder (Alnus glutinosä) is absent from badly drained places. Carex elata, on the other hand grows better in badly drained habitats, and Salix cinerea, is more common in these.

Weather T h e elfects of differences in weather were studied in 1956-9.

Winter 1956-7 was mild, but severe frosts (—4°C. and below) continued until the end of June in the Mildenhall district : the effect was less elsewhere. Most species grew slowly, with obvious frost damage ; dry herbaceous communities suffering most. In late June they were barely over \ m. high, the plants being sparse, with many patches 10-20 m. wide in which all plants were dead. Subsidiary species were frequent—more so than in other years—the dominants being damaged the most severely.

In the same places in 1958, the Vegetation was dense, and was over 1 m. high in late June. Crop yields were low in 1957, the spring frosts being followed by a drought, off-setting the favourable effect of the high temperatures in late summer. Winter 1957-8 was cold (temperatures down to —15°C.) and the Vegetation was hardened against spring frosts. In warm spells in winter and early spring the stems of herbaceous species (e.g., Epilobium hirsutum, Urtica dioica) may Start to elongate. Subsequent frosts will kill the shoots (or stop development) while the short winter shoots of the species are normally unharmed. 1958 was very wet, and the crop yields were high (up to twice the yield in 1957). T h e next winter and spring were mild. T h e high water table caused by the previous wet season persisted for part of the summer. T h i s 1959 summer was both hot and dry.

In places where the water table dropped early there was visible damage from drought (wilting and slow growth) and the crop yields were less than in 1958. Where the high water table persisted for most of the summer crop yields were increased, conditions being both wet (like 1958) and hot (unlike 1958).

As far as is known differences in weather affect the current seasons' growth only, the effects having disappeared the next year.

Vegetation Most of the peat-covered regions of these Valleys are under grass, either permanent or, presumably, semi-permanent. They

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are mainly used for summer pasture by cattle. Some are mown in mid-summer, but may be grazed later. Throughout the length of the Valleys their Vegetation is remarkably similar, provided their soil is peat. T h e r e is a sharp change of Community on alluvial sand higher up the Lark Valley (species lists for these and other communities are given in Haslam, 1960). Wetter parts contain more " wet f e n " species, e.g., Carex acutiformis, Equisetum palustre, Caltlia palustris, Menyanthes trifoliata.

Plantago major and larger Rumex spp are found, near gateways, i.e., on muchtrampled ground. Bellis peretinis usually occurs only with aboveaverage trampling. Filipendula ulmaria, white present in some wet areas, is short, and usually does not flower. It increases with lighter grazing, and when the field is mown, not grazed.

Galium uliginosum is characteristic of wet peat fields, as well as of various fen communities, but G. palustre is normally confined to wetter areas such as ditch banks and hollows, and in the fens to wet communities. T h e two are differentiated by water level, as are Ranunculus repens and R. acris, the former being more abundant on lower levels. However, R. acris is found sparsely in wetter places than can be tolerated by R. repens. Poa palustris and P. trivialis appear to be separated by human interference, P. pratense being abundant in fields, while P. trivialis, though occasionally found there, is abundant in various dry fens at the same water level. Arrhenatherum elatius is rare in wet fields, occasional in dry fields, and abundant in disturbed peat-sand transitions and in some dry fens, a rather similar distribution to that of P. trivialis. jfuncus effusus is common in wet peat fields and in peat-sand transitions. J. inflexus is fairly common in these fields, but unlike J. effusus is concentrated on more trampled areas and where clay has been laid down. Species characteristic of nutrient-poor areas occur locally in wet trampled parts, e.g., Eriophorum angustifolium.

Such treatment seems to decrease the nutrient status of the soil (see Haslam in press). Such species while occurring in fields in Valley areas, are never found in Valley fens, but are common in headwater ones.

Interspersed between the fields are the fens—the areas of " wild " V e g e t a t i o n . These can be interpreted as remnants of an originally continuous fenland. T h e y have come into existence in various ways. (1) Poor's fens. Probably much-disturbed relics of the natural Vegetation (i.e., presumably never cultivated or put down to grass). Most of the present Poor's Fens are wet fens, as in them the level has been lowered by peat cutting. (2) Abandoned mowing meadows. These are usually fairly dry, e.g., Brandon-Thetford region (Clarke, 1926). (3) Abandoned fields, these having been " under grass " in the old O.S. Tithe maps.

I hey are dry, the water table being the same as in adjoining fields, e.g., Barton Mills fens, Icklingham Mill fens. (4) Washlands, e.g., Stallode Wash. (5) Fields abandoned owing to neglect of drainage

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Channels and consequent flooding of the area, e.g., Larling Fen (Mosby, 1938). These are rare, as few areas are sufficiently wet.

(6) Small areas left out in the main division of the land.

T h e final category of " wild " areas is the woods. While some were planted in the last Century, most were already in existence.

In dominants—of tree, shrub, and field layer—there is no difference between the older and the newer woods. T h e woods have the same ränge of water table as the grass fields and the dry fens, the level usually being c, 50-60 cm. below the ground, and seldom rising higher than c. 20 cm. In general, the only Breck fens with a higher water level are those from which peat has been cut.

Wet headwater fens are dominated mainly by Cladium mariscus, Schoenus nigricans and Juncus subnodilosus, with some Carex elata.

A large number of subsidiary species are present. T h e dry fen dominants are Cladium, Phragmites, Filipendula—J. subnodulosus, or, in disturbed places Epilobiutn hirsutum—Urtica dioica— Galinim aparine—Phragmites.

Shrub-layer communities (carrs) are rare, and woods are dominated by alder, alder-ash (Fraxinus excelsior), or birch (Betula spp). In wet Valley fens, in contrast, Phragmites is the usual dominant, with few associated species.

Dry fens typically bear Epilobium—Urtica—Galium, though other genera, e.g., Filipendula, Arrhenatherum can be co-dominant.

Salix cinerea carr is common, and alder and ash-alder woods are frequent.

T h e wet fens of the two types are markedly different, the dry fens less so, and the woods and carrs are virtually identicai.

Species characteristic of nutrient-poor areas, e.g., Drosera spp, in the Breck fens are confined to headwater fens, and Valley fen species are characteristic of nutrient-rich habitats. T h e differences between the two types are ascribed to differences in nutrient status, available phosphorus, nitrogen, and potassium being lowest in wet headwater fens, increasing in more silted, in drier, and in more disturbed habitats giving a ränge of soils of differing nutrient status. T h u s silting and human interference are important not only in themselves, but also for their effect on soil nutrient status. (The evidence is described and discussed in Haslam in press).

T h e headwater fens studied are listed below :— R. Lark (a) Main river, none (b) Tributaries. Tuddenham Mill stream fen* R. Little Ouse (a) Main river, none (b) Tributaries. Thelnetham Fen, Thelnetham Old Fen (" Thelnetham Stream"), Weston Fen, Hopton Fen (" Weston-Hopton Stream ") •Headwater fen communities not seen, but past presence inferred from old Floras.

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Old Buckenham Fen (R. Thet) Pakenham Fen (Unnamed tributary)* The Wangford Fens ( " Wangford stream " ) Fens at head of Eriswell Lode, Dolvers, Eriswell Fens, High Fen (possibly a transition fen) (Eriswell Lode) " Caudle F e n " (Caudle stream, tributary of the Eriswell Lode) Turf Fen, Lakenheath ( " Turf fen streams " tributaries of the Eriswell Lode).

R. Waveney Main river. Redgrave and Lopham Fens R. Wissey (only partly investigated) Foulden Common ( " Foulden stream ").

These form a group remarkably uniform in Vegetation and habitat, in spite of being found scattered over a considerable area and their surrounding land being of different soil types. It is therefore concluded that the unifying feature is springs emerging from the Chalk. Their soils are predominantly open water organic muds, and so they were originally lakes. Not many fens are transitional between the headwater and valley types, as most of the intermediate region is under grass or without peat. T h e following, though, are transitional : — R. Little Ouse (а) (б)

Main river, Bio Norton Fen. Tributaries, Stallode Wash (on Eriswell Lode) Garboldisham Fen. R Waveney Roydon Fen R. Wissey Borough Fen. Of these, Bio Norton, Garboldisham, and Roydon Fens all show communities characteristic of valley fens on their more disturbed and silted parts, and ones characteristic of headwater fens on undisturbed inflow areas ; while Stallode Wash and Borough Fen both have an intermediate flora. Some valley fens with springs along their outer edges have communities characteristic of more nutrient—poor habitats near these springs, e.g., Icklingham Poor's ren.

The valley fens are too abundant to list.

None of the Vegetation found in the Breck Fens is considered natural, since human interference has been present and intensive tor so long. Probably the principal wet-fen dominants are also the natural dominants, and the communities are not far removed m. t:ie natural ones. T h e abundant dry herbaceous communities, though, are due to a deflection of the natural succession FbrasWater ^

c o m m u n i t i e s n o t seen

>

but

P a s t presence inferred from old.

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to alderwood, by human interference. At the present time these communities are so dense that natural tree colonisation is negligible, but the woods will develop in due course from the planted poplars.

Poplar, however, is not a natural dominant in the fens.

Acknowledgements I am extremely grateful for the continued advice and encouragement of Dr. A. S. Watt, F.R.S., who supervised most of the work described in this paper.

Summary The fens in and east of the Breckland on the rivers Lark, Little Ouse, and Wissey, together with those at the head of the Waveney, have been called the Breck fens. The intensive human interference in the past and present history of the fens is described, together with the changes attributed to this. Variations in soil type and water table are also noted, as are variations due to differences in weather in different years. The Vegetation is discussed briefly, it being divisible into the two main categories of head water and valley areas. Headwater areas are nutrient-poor, Valley ones nutrient-rich. The two differ considerably in the communities found in wet fens, less so in those of dry fens, and hardly at all in those of grass fields and woods. The causes of the differences and the successions, are considered in Haslam (in press).

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