Schmidtlein, S; Ewald, J: Landscape Patterns of Indicator Plants for Soil Acidity in the Bavarian Alps., Journal of Biogeography, 30, 1493-1503 (2003)
Aim. Electronic distribution atlases and lists of ecological indicator values are becoming important tools in plant geography. In this contribution we combine a geographical and an ecological databank, and map out patterns of indicator value spectra (instead of single or average values) across a physiographically complex landscape. For our study, we select indicators of soil reaction as a key environmental factor that bears strongly on overall plant diversity patterns in the temperate zone. Our goal is to relate the distribution and diversity of indicator plant groups for soil reaction to environmental controls at the landscape-scale, and thus contribute to a causal understanding of species pools.

Location. We studied the Bavarian Alps, which represent the German portion of the Northern Alps.

Methods. Based on the existing floristic survey, we calculated relative frequencies of nine classes of indicator plants for soil reaction in grid cells. The resulting attribute matrix (cells by indicator class frequencies) was subjected to principal components analysis and to k-means clustering. Results were compared and mapped out in the grid array of the whole region, resulting in continuous and discrete representations of species pool structure. We used GIS to derive physiographic landscape properties from a geological map and a digital elevation model and analysed their statistical relationship with the shapes of indicator spectra.

Results. Averages of indicator values for soil reaction follow the geological structure quite closely. Surprisingly, the diversity of indicator plant groups does not appear to be a function of geological or topographic heterogeneity. It rather seems to be tied to areas of high elevation with uniform geology. The effect is a matter of additional acidophytes in high mountain areas and, in the high calcareous Alps, extreme calciphytes, while species with intermediate requirements are rarer than usual. For explanation, we suggest two facts: (1) a frequent lack of mature soils at high elevations and (2) particularities in soil genetic processes occurring under the harsh climatic conditions of high mountains.

Keywords: Biodiversity, Ellenberg values, floristic database, indicator plants, landscape pattern, soil reaction, altitudinal gradient, GIS.

last modified 2010-10-25