History and ecology of European heathlands

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HISTORY AND ECOLOGY OF EUROPEAN HEATHLANDS N. R. WEBB Lowland heaths occur throughout the Atlantic region of western Europe in a zone extending from northem Spain (Galicia) to beyond the Polar Circle on the north-west coast of Norway (Fig.). This zone is marked by its temperate climate which corresponds more or less to the Cfb climate zone of Koppen (Gimingham, 1972; Webb, 1986). In this, the summers are cool and moist and the winters warm. The mean temperature of the wärmest month is < 22° C and that of the coolest > 0° C. Mean winter temperatures vary from 0°C in southem Scandinavia to 9°C in northern Spain with intermediate values (3-6°C) in the British Isles and France. The Netherlands experience mean winter temperatures of about 1.5° C decreasing eastwards through Germany to the boundary of the zone. Likewise, mean summer temperatures ränge from 16°C in southern Scandinavia to almost 20°C in northem Spain with intermediate values (usually about 15°C) in the intervening areas.

Mean annual precipitation is 600-1000 mm with the greatest amount falling on the western coastal areas. Precipitation varies from about 1500 mm in the western parts of southern Scandinavia (increasing to 2000 mm or more both northwards and as one moves inland) and northern Spain decreasing in the intermediate areas to 600-800mm. The lowest amounts fall in eastem England, the Netherlands and Germany. Jutland (Denmark) and Hailand (Sweden) experience averages of about 700mm a yeai or less.

It is within this region that heath formations occur with gradients in the composition of the Vegetation depending on soils and climate. Dwarf shrub Vegetation, especially that dominated by Calluna vulgaris, forms a continuum of types from upland moorland through lowland heaths (see Gimingham, 1972) throughout this region. Upland moorland has affinities with montane and tundra Vegetation types, while at its southern limits lowland heath has affinities with Mediterranean shrublands. Because of this wide ränge, an artificial distinction is usually drawn between moorland and lowland heathlands. The so-called lowland heaths occur in those parts of the Atlantic Region with an altitude <300m, annual precipitation < 1000mm and where the dwarf shrub Vegetation develops on mineral soils. This definition also encompasses the valley mires of the lowlands (Webb, 1986). Winter protection afforded by snow cover is a significant factor in the occurrence of heaths beyond the defined region. Adequate snow cover enables heaths to persist at higher latitudes, further eastwards into central Europe and in montane regions.

A Classification of European heathland Vegetation has been developed by Gimingham (1972) and summarised by Gimingham, Chapman and Webb (1979) while British Heathlands have now been classified under the National Vegetation Classification (NVC) (Rodwell, 1991).

Dwarf shrub Vegetation comparable with heathland forms in other parts of the world where there is a similar oceanic climate. The best examples are the heathlands (fynbos) in the Cape Province of South Africa. These heathlands are noted for their exceptional biodiversity and for the large number of endemic species present. In particular there are over 500 species of the genus Erica in the Cape Floral Region (Huntley, 1989). Similar types of Vegetation

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are found in Western Australia although they do not contain members of the Ericaceae (Specht, 1979) Soils Lowland heathland depends on the occurrence of chemically poor and acidic soils. Characteristically, heaths form on podsols and the growth of heath Vegetation contributes to the process of podsolization. There are three main parent materials; sands and gravels, dunes and weathered silicious rocks. Sands may be derived from in situ deposits of sands and gravels such as those of southern England or from fluvial glacial deposits such as Jutland, north Germany, the Netherlands and eastern England. In places, these fluvio-glacial sands may have been re-deposited by wind and may Cover calcareous strata to varying depths resulting in greater biological diversity. In other areas heaths form on dune sands which, although of marine origin, have become decalcified. Good examples of this type of heath are to be found on the North Sea coasts of the Netherlands and Germany.

Heathland forms on soils derived from the weathering of old metamorphic and sedimentary siliceous rocks which are characteristic of the western -most regions - northern Spain, western France (Brittany), south-west England (Cornwall), Wales, Ireland and Scotland.

Topography and Hydrology Topography, which in turn affects hydrology, produces considerable local Variation in heath Vegetation. There is a clearly marked series of types (Webb, 1986). In dry heath the water table is well below the surface and the soils are free draining throughout the year. Here the soils are typical podsols. Humid heath occurs where drainage is impeded and gley soils are found. Here the water table is within 40 cm of the soil surface. In wet heath drainage is impeded and the water table is very close (<10cm) to the soil surface and at times may be at the surface. Valley mires occur where the water level is at or above the soil surface, resulting in the formation of peat.

The Extent of European Heathlands The principal areas of heathland in Europe (Fig.) are in north-west Spain (Galicia), south-western France and in Brittany, the British Isles, Belgium and the Netherlands. Some heathland occurs further south in Spain, even as far as the Strait of Gibraltar but at higher altitudes. Extensive areas of heathland occur not only in western Germany ( the States of Schleswig Holstein and Lower Saxony) but also in the eastern parts in the State of Brandenburg where the heathlands extend almost to the River Oder and the border with Poland, and in Mecklenburg-Vorpommern. There are also important areas of heathland on the Baltic coast although we are not certain of their eastern limit. In Denmark there is heathland in Jutland and parts of Sjaeland. There is heathland in southern Sweden (Scania) and on the west coast of Norway northwards to the Polar Circle. The eastward extent of heathland in Europe has only been recently determined and we are not certain whether there is any heathland further east in western Poland and on the Baltic coast. However, eastwards, as the winters become more severe, Calluna vulgaris is unable to form open

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Approximate distribution of heathland in western Europe. heathlands and exists only in the ground flora of the forests, so long as there is not too much shade, where it receives protection from the low winter temperatures.

In Britain, heathland occurs in the south west peninsula, in the Scilly Isles and on the coasts of Cornwall and north Devon. On these coasts invasion by trees and scrub is checked by exposure (wind and salt spray) and here heathland may be considered as climax Vegetation. Heathland occurs on the Pebble Bed commons in south Devon and in Dorset and the New Forest.

Heathlands occur in northern Hampshire and Surrey and in Sussex, especially Ashdown Forest, with small areas in Kent. In East Anglia there are heathlands in the Breckland on the Sandlings in Suffolk and in north Norfolk. The Breckland heathlands have formed sandy deposits derived from glacial outwash. Sands of glacial origin (the Cover Sands) also occur in Lincolnshire and formerly carried heathland, but today only small areas remain. Further north heathland occurs in the Vale of York. Scattered heathlands still occur in the Midlands (Leicestershire and Nottinghamshire) and there are good areas in

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Shropshire. There are extensive coastal heathlands in west and north-west Wales. Most of northern Britain contains moorland but here and there are scattered areas of lowland heathland.

In former times lowland heathland in Europe extended over several million hectares but today a little over 350 000 ha remain (Diemont, Webb & Degn, 1996) (Table). These figures are incomplete. We have poor estimates for the amount of heath in Ireland and Norway. In both these countries, and in Sweden, lowland heathland merges with mire communities which roakes estimation difficult. Likewise, southwards in Spain and Portugal there are transitions to Mediterranean shrubland communities.

Estimates of current area of heathland in Europe (from Diemont, Webb & Degn, 1996) Area (ha) in 19th Century

Current area (ha)

United Kingdom

145 000

58 000

The Netherlands

800 000

40 000

Belgium

163 000

13 000

France

200 000

65 000

Germany

1 000 000

55 000

Denmark

658 000

70 364

Sweden

300 000

93 000

Everywhere there has been a startling decrease in the extent of heathland due to conversion of the land to forestry, farmland, and urban and industrial development. Today in most countries heathland is protected. Nevertheless, losses continue through inadequate management. Almost everywhere the traditional uses of the heathlands have ceased and, as a result of succession, the heathlands disappear under scrub and trees. To conserve them they must be actively managed and all too frequently the management has been insufficient, especially as burning and grazing are no longer practised so widely. The current estimates for British lowland heathland is 58000 ha. The national biodiversity action targets are to maintain this area and through restoration increase the area of heathland by 6000 ha (Anon, 1995).

The Origin and Use of European Heathlands For the most part. European heathlands developed following forest clearances which commenced about 4000 years ago. The pattern is much the same throughout the entire ränge of the heathlands. At a few locations the clearance of forest to provide fuel for iron smelting occurred in the fifteenth and sixteenth centuries. It is now clear that the subsequent use of the land by humans was one of the factors which prevented the regeneration of the forest.

Nevertheless, climate changes in the Sub-boreal period are thought to have

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hastened the deterioration of the sandy acidic soils once the tree cover had been removed, which in combination with the use of the land by humans made it more difficult for trees to re-establish.

About 2000 years ago, it is generally thought that open heathland largely lacking trees had become a well marked feature of the landscape wherever tracts of sandy acidic soils occurred (Gimingham, 1972; Webb, 1986). There has been much speculation on the origin and persistence of the heaths and a variety of theories have been proposed (reviewed by Gimingham, 1972). The early ecologists found the absence of trees difficult to explain, although it was widely recognised that a relaxation of grazing resulted in invasion by trees. It was thought that these areas had always been sandy, treeless wastes and that the heath Vegetation was a temporary stage reached during the succession from bare sand to forest. It was not until palynology and historical ecology developed that it become apparent that these areas formerly carried trees, that the trees had been removed through the activities of early humans, and that the same activities were responsible for maintaining the open heath.

Throughout the European heathlands there has been a ränge of traditional management practices involving grazing, cutting turf, burning, cutting Vegetation for fuel, and harvesting the Vegetation for fodder. Many of these activities occurred in combination and the relative importance of each varied from region to region. It is important to note that these traditional activities had been responsible for the maintenance of open heathland until at least this Century and in a few areas the persistence of heathland today still relies on them.

In western Norway, Faeroe Islands, Iceland, Shetland and other islands a characteristic land use was developed in combination with fishing. This land use was well established by Viking times and had persisted until the mid-part of this Century. In western Norway, the Settlements on the coastal heathland consisted of an infield area around the settlement devoted to pasture, hay meadows, and arable plots. An extensive outfield area consisting of heathlands was separated from this. The management of this system was not unlike that practised further south, particularly in the Netherlands and has been described

by Kaland (1986). Cattle were kept in the byre during the winter, whereas sheep and horse grazed out of doors all the year round. To provide adequate forage on the heathland, small, irregularly shaped areas were burnt from time to time. This pattern of burning not only provided a continuous supply of nutritious forage, but created small-scale patterns of diversity in the Vegetation.

Heather was cut on a 3-5 years cycle to provide winter fodder for the animals in the byre. For fuel the farmers cut peat from the boggy areas on the heathland, again increasing the diversity of the Vegetation. In addition, during the autumn they dug the surface of the peat, allowed it to weather over the winter and then, when dried, they would sprinkle this material on the floor of the byre to absorb the excrement of the animals. This material together with the remains of hay and heather fodder was then periodically dug out of the byre and spread on the arable areas. These were small fields or beds, and often seaweed and fish entrails were added as well as peat and manure. This created raised soils of the "plaggen" type which were well formed by the Middle Ages.

The remainder of the infield was used for hay production. Hence, there was a

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well developed use of the heathland which maintained it and sustained a way of life.

A comparable system was operated throughout the north-west European lowland of Flanders, the Netherlands and North Germany (Gimingham & De Smidt, 1983). Here the heaths were used as a source of nutrients for the arable land; the transfer being effected by means of turf cutting and sheep grazing.

Sheep were allowed to graze on the heath for about six hours during the day and were controlled by a shepherd with a dog. For the remaining eighteen hours they were confined in the barn in Order to collect their excrement. The meat and wool which they produced were considered by-products. Turf, in contrast to peat, was cut from the drier parts of the surrounding heathlands and laid on the floor of the barn to absorbed the excrement. Periodically, this material was taken from the bam and dug into the arable fields which surrounded each village. Cattle were kept in the barn all the year round and also supplied with turves. There was a flow of nutrients from the heath to the arable land through the animals and the barn. As a result of adding the turves to the arable land the soil level was raised and over the millennium from 900 to 1900 the characteristic "plaggen" soils developed. In some places these soils were raised to a height of 1 m above the original soil level. The effect on the heathland was considerable. It maintained a low nutrient status and the presence of the grazing animals arrested succession to scrub and forest.

In Jutland (Denmark) a similar system operated. The heaths were grazed principally by sheep, which remained out all the year round and which were frequently supervised by a shepherd. Cattle were also grazed, but often tethered and periodically taken to their stalls to collect their dung. Winter fodder for these animals was collected by cutting young heather and mixing it with lichens and hay. Turves were cut for fuel and a variety of other uses, including house insulation and, as was the case further south, this material was used to absorb the excrement of the animals either in the stable or in the farm yard.

This material was then used to fertilise the arable land. To provide additional fertiliser, turves were burnt and the ash scattered on the arable land or mixed with the turves from the stables. The permanent arable areas were supplemented by small transient plots cultivated from the heath. Often an area of heath Vegetation was bumt, and the ash and humus ploughed in. Further additions of ash obtained by burning yet more turves could be added to these plots, but the plots were short-lived and when abandoned reverted to heath (H0jrup, 1970; Odgaard, 1994). Elsewhere, on the heath soils such as Eastern Jutland, land was taken from the heath and a succession of cereals grown over a period of 6-8 years before the land was abandoned and allowed to revert to heath. (Wors0e, 1990).

The use of the heathland in Jutland, while similar to both that in Norway and in the areas further to the south, was not so tightly organised. This was also the case in Britain where in the lowland heaths stock were grazed, peat and turf cut, and the Vegetation cut for fodder and fuel (Webb, 1986). However, we do not have clear evidence whether arable plots were fertilised using material impregnated with animal excrement, although recent evidence suggests this may have been the case. Rather than covering extensive tracts of land, the

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heaths were small yet continuous areas of dwarf shrub Vegetation, and were interspersed with better quality land. The heaths were used in combination with this land. Nevertheless the traditional management, as elsewhere, served two purposes; first, it prevented the regeneration of forest and secondly, it maintained a low nutrient status in the soils.

The role of fire is problematical. It is likely that areas were bumt to provide a flush of new growth which was more nutritious to the grazing stock. The size of the area burnt may have varied from region to region. In some places, small carefully chosen patches were burnt while elsewhere large areas, as in Jutland (Denmark) and Hailand (Sweden) were burnt rotationally. In the past the occasional wildfire may have also occurred. Today, in some regions such as north-western France and southern England large fires occur, especially in hot dry summers. These fires are mostly accidental but occasionally the result of arson. They are often extensive and are very harmful to wildlife.

Grazing with sheep, cattle or ponies has been important in all heathland regions. In the past, these animals were managed rather than allowed to ränge freely, although this too varied from region to region. In many places an in-field and out-field system was operated. Animals were often taken off the heath, sometimes every night or at other specified times, and this had important consequences for the composition of the Vegetation and the cycling of nutrients. Frequently there were breeds of sheep adapted to feeding on the heather rather than the grass.

The heathlands of western Europe are a cultural landscape which makes a significant contribution to biodiversity. This aspect of heathlands has been recognised by the large number of national and international designations which have been attached to them and which should ensure their protection from conversion to other land uses. However, these designations often do little to ensure adequate management. The role of humans in shaping this landscape is paramount and provides us with a background on which to construct our conservation and management. Today only fragments of the original heathland remain. The ownership and management of the countryside have changed in a way which makes the restoration of traditional management difficult. The principles, however, are simple. The use or management of these areas must ensure that succession to scrub and trees is checked and that the nutrient status of the soils is kept low. A variety of management options are available including burning, cutting and grazing. However, as heathland is no longer part of the agricultural system of the lowlands these measures need to be implemented for conservation management alone, for which resources need to be found.

References Anon (1995). Biodiversity: The UK Steering Group Report, Volume 2 Action Plans. HMSO, London.

Diemont, W. Hâ&#x20AC;&#x17E; Webb, N. R., & Degn, H. J. (1996). A pan-European view on heathland conservation. Proceedings of National Heathland Conference 1996. English Nature, Peterborough.

Gimingham, C. H. (1972). Ecology of heathlands. Chapman & Hall, London.

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Gimingham, C. Hâ&#x20AC;&#x17E; Chapman, S. B. & Webb, N. R. (1979). European heathlands. In: Specht, R. L. (ed.) (1979). Ecosystems ofthe World Volume 9A: Heathlands and related shrublands. Elsevier, Amsterdam Gimingham, C. H. & De Smidt, J. T. (1983). Heaths as natural and seminatural Vegetation. Man's impact on Vegetation (eds W. Holzner M J A Werger & I. Ikusima). Dr W. Junk, The Hague.

Huntley, B. J. (ed.) (1989). Biotic diversity in Southern Africa. Oxford University Press, Cape Town.

H0jrup, O. (1970). Hedens udnyttelse, Danmarks Natur 7. (eds A. N0rrevang & T. J. Meyer. Politikens Forlag, K0benhavn.

Kaland, P. E. (1986). The origin and management of Norwegian coastal heaths as reflected by pollen analysis. Anthropogenic indicators in pollen diagrams (ed. K.-EBehre). A. A. Balkema, Rotterdam.

Odgaard, B. V. (1994). The Holocene Vegetation history of northern West Jutland, Denmark. Opera Botanica, 123: 1-171.

Rodwell, J. (ed.) (1991). British plant communities, Volume 2. Mires and Heaths. Cambridge University Press, Cambridge.

Specht, R. L. (ed.) (1979). Ecosystems ofthe World Volume 9A: Heathlands and related shrublands. Elsevier, Amsterdam.

Webb N. R. (1986). Heathlands. Collins, London.

Wors0e, E. (1990). Mols Bjerge. Skippershoved, Randers.

Dr. N. R. Webb Furzebrook Research Station NERC Institute of Terrestrial Ecology Wareham Dorset BH20 5AS

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