01.12.1 Habitat Function for Rare and Near-Natural Plant Communities
Almost all soils are generally potential growth sites for plants. Therefore, they provide a habitat for plant communities. Differences in efficacy arise from the evaluation of the vegetation potentially growing on the soil in question, with rare species or plant communities being rated higher, primarily from the viewpoint of nature conservation.
Changes in the soil caused by excavation, aggradation and translocation, by nutrient inputs and decreased groundwater levels largely mitigate the characteristics specific to a site. Rare specialized plant species are thus deprived of their habitat. Poor and dry sites with the comparatively rare dry grasslands, which root here, constitute a special case that is not uncommon. Their occurrence in the Berlin area, however, is tied to a low degree of anthropogenic influence.
The assessment of the habitat function carried out here develops the concept developed by Lahmeyer (2000) further. Especially soil associations with extreme water balance conditions and rare soil associations are classified as valuable here. Rare and wet sites fall into the category of special sites. Locations that are particularly valuable from an ecological point of view can thus be highlighted, as can potential sites for the development of lea associations, wet meadows and bog areas.
Extremely dry and nutrient-poor dunes and anthropogenically created young soils represent potential sites for valuable dry grasslands. As a special natural space, these areas receive a “medium” rating, regardless of their near-natural quality.
Overall, the evaluation represents the potential of the soil to sustain specific types of vegetation, and does not assess the current vegetation.
The following criteria are used to assess the habitat function for rare and near-natural plant communities: near-natural quality (cf. Map 01.11.3), regional rarity of the soil association (cf. Map 01.11.1), dampness of the site (cf. Map 01.01 and 01.06.4) and nutrient supply (cf. Map 01.06.9) (cf. Fig. 1). “Special sites” can be identified based on these criteria.
Special sites include:
- Areas on which the site dampness was indicated as “wet”
- Areas on which the regional rarity of the soil association has been rated “very rare to rare”
- Areas with dry, nutrient-poor soils.
As shown in Tab. 1, the evaluation of the habitat function for near-natural and rare plant communities is carried out according to three categories (low (1), medium (2), high (3)), taking into account the near-natural quality. Rare and wet classes are rated considerably higher than dry locations, which are less sensitive because they are able to regenerate more easily. The latter are assigned exclusively a medium potential for development, regardless of their near-natural quality. “Normal” locations are assigned a medium capacity only if they are very close to being near-natural.