Mette Løyche Wilkie is a Forestry
Officer in the Forest Resources
Division, FAO Forestry Department,
Rome.
Plantation forests established centuries ago to stabilize sand dunes in Denmark now contain abundant biological diversity.
Denmark was one of the first countries to stabilize sand dunes by planting trees. By the mid-1800s a number of forest plantations were being established using a variety of both conifer and broad-leaved species. In addition to their continuing function of dune fixation, some of these older plantations now have considerable recreational and amenity value and have become important habitats for a large variety of plants and animals.
References to the damage caused to arable land and buildings by drifting sand in Denmark started to appear in the fifteenth century. The first attempt to reverse this trend was a Royal Decree in 1539 which prohibited removal of vegetation and grazing of animals in coastal areas susceptible to sand drifts (Nielsen, 1994; Danish Forest and Nature Agency, n.d.,c). However, the decree had limited effect as people needed the vegetation for thatch, fuelwood and fodder and the areas were important communal grazing areas. By 1867 approximately 62 000 ha - close to 5 percent of the total arable land in the western part of the country - had been destroyed by drifting sand formations, some of them reaching more than 10 km inland and forcing the relocation of entire villages. Several farms were relocated more than once (Nielsen, 1994; Danish Forest and Nature Agency, 2001; Royal Danish Ministry of Foreign Affairs, 2002).
In the 1720s attempts were begun to combat the sand drifts, e.g. with fences made of cut branches (wattle fences) and, more successfully, by placing seaweed and sod on the sand and sowing grasses such as European beachgrass (Ammophila arenaria) and lyme grass (Leymus arenarius), but attention later turned towards the planting of trees. By the 1850s the techniques had been developed and large tree plantation programmes were initiated to stabilize dunes in the western part of the country. The necessary legal framework was created through the law to combat sand drift (Sandflugtsloven) of 1867, by which the State took over most of the responsibilities for the costs of stabilization measures and was granted the option of purchasing land for the establishment of dune plantations.
In some places a wide range of species were tried, including hardwoods such as oak and beech, conifers such as Scots pine, Pinus sylvestris (the only pine indigenous to Denmark), and introduced firs such as Abies nobilis, Abies alba and Abies nordmanniana. In other places, the environmental conditions for establishing forests were extremely difficult and the introduced Swiss mountain pine, Pinus mugo, was established over large areas, creating "a carpet of mountain pine rolled out over the dunes" (Nielsen, 1994). Later introductions included the North American lodgepole pine, Pinus contorta, and Sitka spruce, Picea sitchensis. Several of the original stands of introduced Pinus mugo, which in most places only reach a height of 2 to 4 m, have since been converted to a mix of other species, taking advantage of the improved soil and shelter conditions created by the first plantings.
Today there are approximately 30 000 ha of dune plantations (Danish Forest and Nature Agency, 2001), equivalent to approximately 7 percent of the total forest cover in the country.
Tisvilde Hegn in northern Zealand was one of the first dune plantations to be established (Danish Forest and Nature Agency, n.d.,a,b). The area used to be covered by forest and agricultural land, but in the sixteenth century sand started drifting inland and within a couple of centuries the area was completely abandoned.
After initial stabilization of the dunes through the sowing of lyme grass and European beachgrass in the 1730s, the establishment of a forest plantation began in 1800. In the beginning, seeds of Scots pine were sown, and later also seeds of spruce (Picea sp.), birch, beech and oak. Progress improved with the planting of seedlings, and by 1900 the whole area (2 000 ha) was forested.
Tisvilde Hegn now contains a very valuable flora, including the orchid creeping lady's-tresses (Goodyera repens) and several species of wintergreen (Pyrola sp.) which are dependent on the moss-rich coniferous forests. These species are known to have in-migrated from the Nordic conifer forests with the aid of migrating or visiting birds and are generally viewed as a natural enrichment of the indigenous flora. Several of these species are thought to have previously existed in Denmark, before the original forest cover was almost totally depleted (reaching a low of 4 percent of total land area around 1800). A total of 113 species of fungi on the national Red List of threatened species (classified according to the categories of the World Conservation Union [IUCN] Red List) have been recorded from Tisvilde Hegn (Danish Mycological Society, 2002). As in many of the other dune forests, collection of wild edible mushrooms is a popular activity among local people, visitors and tourists.
The plantation contains many nationally rare insects, especially beetles and butterflies associated with the older coniferous stands where more light penetrates. There are also numerous species of ants of which one, Formica foreli, is found nowhere else in Denmark (Collingwood, 1979).
The forest is also a valuable habitat for amphibians such as newts (Triturus sp.) and the green frog (Rana esculenta). The large and diverse bird population includes several rare species such as tawny pipit (Anthus campestris) and stock pigeon (Columba oenas). The black woodpecker (Dryocopus martius) also breeds in this area.
Both the European roe deer (Capreolus capreolus) and red deer (Cervus elaphus) can be seen in the forest, the latter having been reintroduced to the area.
Tversted Dune Plantation, a plantation established on sand dunes in 1858, has great recreational value; visitors feed the ducks in one of the lakes
- M.L. WILKIE
Tversted Dune Plantation in Jutland is the oldest dune plantation in the northern part of Denmark. The establishment began in 1858 and it now covers an area of 775 ha. Although initial efforts were focused on Picea glauca and Pinus mugo, many species were tried in this area including Pinus sylvestris and introduced conifers such as firs (Abies alba, A. grandis, A. nordmanniana and A. procera), pines (Pinus contorta, P. mugo and P. nigra), spruce (Picea glauca and P. abies) and larch (Larix sp.), as well as a number of indigenous broad-leaved species (oak, beech, alder, birch and wild cherry, among others). A couple of small lakes were also created (Sand, 1976).
Efforts to convert some of the first-generation Pinus mugo stands to a mixture of other species have been quite successful. In other areas of the plantation many of the trees, including introduced species, are now regenerating naturally and many stands have a mix of ages as well as species. As a result the forest landscape is very varied, in places bearing a close resemblance to the natural forests of neighbouring Norway and Sweden.
The variety of tree species and habitat niches has encouraged the in-migration of numerous animals including fox, badger, marten, red squirrel and three species of deer (roe deer, red deer and fallow deer, Dama dama). Whereas the first two deer species are naturally occurring in Denmark, the latter probably escaped from a deer farm. A large variety of birds breed in the area, including birds of prey such as goshawks (Accipiter gentilis) and buzzards (Buteo buteo). Ravens (Corvus corax), nightjars (Caprimulgus europaeus), woodpeckers (Picus viridis and Dendrocopos sp.) and woodcocks (Scolopax rusticola) can also be seen or heard.
Noteworthy plants include several orchid and lichen species and a wide range of mosses. Several of the plants are known to have arrived from the forests of neighbouring countries such as Norway and Sweden with the help of migrating or visiting birds. Twenty species of fungi listed on the national Red List have been recorded from this plantation (Danish Mycological Society, 2002). One of the old stands of Abies nordmanniana, established around 1900, has been certified as a national seed stand because of its fine growth form. The forest has great recreational value as evidenced by its many visitors.
Nightjar (Caprimulgus europaeus) is found in Tisvilde Hegn and Tversted Dune Plantation
- I.N. NELSON
No comprehensive national survey of the plant and animal species found in dune plantations has been undertaken, but a number of location-specific surveys have provided an indication of the biological diversity contained in these plantations. For example, a survey of important plant species and areas of high environmental value was conducted from 1996 to 1998 in the dune plantations of Thy Forest District in northwestern Jutland (Søndergaard, 1998).
The District comprises 14 plantations with a total forested area of about 9 900 ha. The species planted in the mid-nineteenth century were mainly conifers (currently accounting for 81 percent of the total forest area), mostly Pinus mugo and other pines on the poorer soils and spruce (Picea glauca), fir (Abies alba) and broad-leaved species such as oak on the better soils further inland (Nielsen, 1994). Today, some of the first-generation P. mugo stands have been converted to other species and an emphasis is being put on the use of indigenous broad-leaved species where feasible, as well as on more productive and economically valuable conifers such as Picea sitchensis, Abies alba and Abies nordmanniana (Nielsen, 1994).
The survey registered all plant species listed in the 1990 and 1997 Danish Red Lists of threatened animal and plant species (Stolze and Pihl, 1998a) and the 1997 Danish Yellow List (Stolze and Pihl, 1998b), which contains plant and animal species that are decreasing in Denmark yet still occur in numbers high enough to exclude them from the 1997 Red List, as well as species for which Denmark has special international responsibility, even if they are not included in the 1997 Red List.
Locally rare plant species not on the Red Lists were also registered, as were some of the more common species where they occurred in a form or in an abundance that made them particularly noteworthy or of high protection priority (e.g. old juniper, Juniperus communis).
The plant species were classified into five groups - three, "critically endangered", "vulnerable" and "rare", in accordance with the Red List classifications; and two additional categories: locally threatened or rare species, and semi-rare or non-indigenous species that require monitoring or that might be of interest for excursions and guided nature walks.
Rare fungi and animals and the location of more or less permanent nests (goshawks, buzzards and grey heron, Ardea cinerea) and dens (badger, Meles meles) were also recorded (Søndergaard, 1998).
The survey registered and mapped a total of 106 species of plants of local or national interest. The total number of plant species in the plantations is obviously much higher, since planted tree species and common plant species were not included unless they were of special interest.
Of the 106 plant species registered, 44 species were of national interest (e.g. included on the Danish Red or Yellow Lists). Eleven of these have protected status, including several orchids (e.g. creeping lady's-tresses, found in 18 locations; northern or pale coral-root, Corallorhiza trifida, found in three locations; heart-leaved twayblade, Listera cordata found in 25 locations; and twayblade orchid, Listera ovata, found in only one location).
The list also included some species that were predominantly found in the adjacent ecosystems that have been protected from sand drifts by the plantation, such as the nationally protected spiny-spored quillwort (Isoetes echinospora), which is restricted to nutrient-poor Lobelia lakes and was only found in one location; and three different species of the orchid genus Dactylorhiza, of which the more common species, D. maculata, was found in 41 different locations (Søndergaard, 1998).
In comparison, a national survey found a total of 208 plant species in sand dune ecosystems. Of these species, 14 are listed on the Danish Red List, but most of them were found in green dunes or humid dune slacks (seasonally flooded low-lying areas within dune systems) and not in white dunes, the precursor of most dune plantations (Ellemann et al., 2001; Stolze and Pihl, 1998a).
The results of the survey have been used in the preparation of general management principles for the conservation of important plant species in the forest district, and in designating protection priorities. A species database including maps with location and descriptions of habitat type has been prepared and is used by forest workers and supervisors.
A similar survey is currently being conducted in the province of Viborg.
A broad-based committee representing farmers', fishing and forest associations, non-governmental organizations (NGOs), research institutions, ministries and local government associations was established in March 2000 to prepare a report to form the basis for a government action plan for biological diversity and nature conservation. Several public hearings were held, and the final report, Danish Nature - status, trends and recommendations for future biodiversity policies, was presented in August 2001 (Wilhjelm Committee, 2001a).
The overall recommendations of the report with regard to forests and their biological diversity aim at conserving existing forests and their biological diversity; increasing the existing forest area; increasing the area of natural and semi-natural forests left unmanaged to allow them to develop naturally; and increasing the emphasis on nature-friendly forest management practices, including the use of natural regeneration and the promotion of indigenous trees and shrubs. In addition, more open areas should be accommodated in forests.
With regard to sand dune plantations, one of the goals is to increase the use of indigenous tree species in these plantations from the current 27 percent to 40 percent over 80 years - one tree generation. New plantations in the sand dune districts should contain at least 50 percent indigenous species.
The proposed strategy for managing sand dune areas is aimed at enhancing the environmental values and safeguarding the habitats of the indigenous animal and plant species adapted to and dependent on these ecosystems. The natural dynamism of sand dune formations should be restricted through stabilization efforts only where this is necessary to safeguard significant public assets against sand drifts or to prevent unacceptable nuisance from sand. Removal of introduced conifers such as Swiss mountain pine and lodgepole pine that are expanding on to dune heaths and moors adjacent to the existing plantations is also an important part of the strategy for sand dune areas.
The committee also recommended the identification of three relatively large contiguous nature and forest areas in which interspersed forested and non-forested areas will be left unmanaged. The three suggested areas include one of the largest forests (Grib Skov) and the adjacent lake, a coastal area on the island of Møn and an area of about 20 000 ha in Thy incorporating an existing nature reserve and most of the dune plantations covered in the survey described above. Some conversion of the existing plantations to indigenous Scots pine and mixed stands of oak, Scots pine and birch is suggested, as these will provide more light and increase the value of the plantations for conservation of biological diversity as well as for recreational purposes. Some planted areas may also be cleared to make space for open non-forested areas within the plantations (Wilhjelm Committee, 2001b), which should lead to an increase in the number and extent of different habitats and to improved protection of the plants identified as vulnerable.
Collection of wild raspberries and chantarelle mushrooms is a popular activity in Tversted Dune Plantation, as it is in many other dune plantations
- M.L. WILKIE
Some 150 years after the establishment of the first forest plantations on sand dunes in Denmark, the result is a series of plantations with a wide range of tree species and habitats. Some of the first-generation monocultural stands have been converted to a mixture of different species, and in all areas deliberate interventions to promote a variety of species and habitats through selective thinnings have paid off. Most of the dune plantations have now evolved into varied forest landscapes supporting a large number of plant and animal species within the forests as well as protecting adjacent ecosystems from the smothering effects of sand drifts. In addition to fulfilling the important function of stabilizing sand, these plantations have an important role in the conservation of biological diversity.
Forest plantations are often considered to be limited in biological diversity - yet these dune plantations demonstrate that, with time and careful management, planted forests can become species-rich ecosystems.
A survey of important plant species and areas of high environmental value was conducted in the dune plantations of Thy Forest District in northwestern Jutland (shown here, Tved Plantation)
- I.N. NIELSEN
Yellow bird's-nest (Monotropa hypopitys), one of the rare plants identified during the survey of biological diversity in dune plantations
- I.N. NIELSEN
Bibliography
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