|Audorff, V; Kapfer, J; Beierkuhnlein, C: The role of hydrological and spatial factors for the vegetation of Central European springs, Journal of Limnology, 70(Suppl. 1), 9-22 (2011)|
Understanding the driving factors of species occurrence is a prerequisite for estimating the indicator suitability of spring-inhabiting plants. We analysed 18 environmental variables in a two-step approach, regarding their ability to explain the species composition of 222 springs on five siliceous mountain ranges in central Germany and the north west of the Czech Republic (49.9° – 50.8° N, 10.6° – 12.8° E). First, we identified the significant environmental variables in each of the three subsets of spatial, hydrophysical and hydrochemical variables by means of a forward-selection procedure. Then we performed a partial canonical correspondence analysis (pCCA) to estimate the influence of each of the three subsets purely as well as in their combinations. To compare the five regions regarding the dissimilarity of their vegetation composition as well of their environmental variables, we used a multiple response permutation procedure (MRPP).
Hydrochemical factors turned out to play the fundamental role in determining the plant community composition of the investigated springs. Spatial factors, in particular the altitude, were correlated with the hydrochemical factors, but were less meaningful than those. Hydrophysical factors played only a marginal role. More precisely, the species occurrence was mainly driven by a gradient of nutrient availability, which in turn reflected the acidity status. This gradient was primarily represented by high Al, Cd, and Mn concentrations in acidic spring waters, high Ca and Mg concentrations were encountered in circumneutral spring waters.
By comparing the five regions we could show that spatial patterns in the vegetation of springs emerge and provide valuable ecological information on the water quality. Therefore we suggest plant species occurrence to be a suitable tool to unveil the acidity status of springs and their forested catchments by biomonitoring approaches.