Nicola Arndt und Matthias Pohl - Neobiota

Nicola Arndt und Matthias Pohl - Neobiota Nicola Arndt und Matthias Pohl - Neobiota

22.02.2013 Aufrufe

aktuellen Vorherrrschen der landwirtschaftlichen Nutzfläche. Die absolute Gesamtzahl der Arten in der Landschaft liegt dagegen höher wegen der vielen eingeführten und neu zugewanderten Arten 1 Introduction Up until now, little attention seems to have been devoted to the possible use of potential natural vegetation as a baseline for evaluation of current landscape patterns (cf. RICOTTA et al. 2000). This is due to problems involved in estimating and mapping potential natural vegetation of a given area of land, especially if the area is subjected to intensive land use, as is mostly the case in the European lowlands. The completion of the Map of Natural Vegetation of Europe at the scale 1 : 2 500 000 (hereafter ’the European map’) now provides us with a tool for comparing current and potential natural vegetation of Europe, and thereby enables us to discuss, e.g., the role of humans in relation to the development and structure of contemporary landscapes. In the present paper, the relationship between potential natural and current vegetation of Denmark will be dealt with in order to estimate the impact of human land use upon natural biodiversity of the Danish landscape. Table 1: Vegetation units of the Map of Potential Natural Vegetation of Denmark. ’Local species density’ refers to the number of species normally found within a stand (ca. 25 x 25 m) of the unit. ’Weighted species density’ is local species density multiplied by the area (%) of the unit. Units more or less corresponding to NATURA 2000 habitat types are marked as follows: x: NATURA 2000 type, ο: high priority NATURA 2000 type, xx: includes several NATURA 2000 types, xο: includes several NATURA 2000 types, one or several of which are of high priority. Natura 2000 X 286 Natural vegetation Mapping unit Area (ha) Area (%) Local species density Weighted species density x F8 Oligotrophic birch-oak forest 560,700 13.0 20 260 F37 Oak-hornbeam forest 77,300 1.8 25 45 X F79 Oligotrophic beech forest 1,525,400 35.4 10 354 x F108 Meso-eutrophic beech forest 1,718,400 39.9 25 998 x F109 Beech forest on limestone 9,900 0.2 30 6 Ο T1 Wet alder woodland 55,000 1.3 30 39 U28 Oak-ash-elm-alder polder forest 61,500 1.4 25 35 Xx P4 Baltic sand dune complex 2,200 0.1 60 6 Xο P5 NW European sand dune complex 107,500 2.5 60 150 Xx P19 W European salt marsh vegetation 6,600 0.2 40 8 X P22 Baltic coastal saline grassland 15,700 0.4 40 16 Ο E10 Frisian-Danish coastal dune heath 75,300 1.8 15 27 Ο S8 Sphagnum magellanicum raised bog 22,000 0.5 15 8 Xx R1 Freshwater areas incl. R1 (= tall reed swamps) 70,000 1.5 --- --- Total 4,307,500 100.0 1,952

Figure 1: Potential natural vegetation of Denmark. For explanation of the map units, see Table 1. 2 The natural vegetation of Denmark According the the European map (see Figure 1 and Table 1), about 93 % of the total land area of Denmark is judged to be covered by different types of deciduous forest under natural conditions. The remaining area is occupied by coastal biotopes, open inland biotopes and freshwater areas (Figure 2). The map of the potential natural vegetation of Denmark includes 14 vegetation units. In Table 1, the area of each unit has been estimated in hectares as well in percent of the total land area. Below, the distribution pattern of the units in relation to geomorphology and climate will be dealt with (cf. JACOBSEN 1989). Special attention will be given to units which occupy small areas, but for which the Danish occurrences seem to represent the major part of their total European distribution. 287

Figure 1: Potential natural vegetation of Denmark. For explanation of the map units, see Table 1.<br />

2 The natural vegetation of Denmark<br />

According the the European map (see Figure 1 and Table 1), about 93 % of the total land area of<br />

Denmark is judged to be covered by different types of deciduous forest <strong>und</strong>er natural conditions. The<br />

remaining area is occupied by coastal biotopes, open inland biotopes and freshwater areas (Figure 2).<br />

The map of the potential natural vegetation of Denmark includes 14 vegetation units. In Table 1, the<br />

area of each unit has been estimated in hectares as well in percent of the total land area. Below, the<br />

distribution pattern of the units in relation to geomorphology and climate will be dealt with (cf.<br />

JACOBSEN 1989). Special attention will be given to units which occupy small areas, but for which the<br />

Danish occurrences seem to represent the major part of their total European distribution.<br />

287

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