Divergent environmental filters drive functional segregation of European peatlands

Abstract:

Plant communities are largely shaped by prevailing climatic conditions. As a result, environmental change is expected to alter the (functional) composition in plant communities. Because plants, and particularly the composition of plant species, play an important role in driving ecosystem processes, it is crucial that we improve our understanding on which environmental factors are most important in shaping plant communities. Here we presnt the results for a cross–Eurpean study, were we assessed the role of environmnetal conditions on plant community composition in 56 peatlands. We show that plant species richness and diversity are relatively stable across the main environmental gradients. Nevertheless, we observe large changes in the plant community structure. In other words, species turnover increased with increasing differences in environmental viariables. Such turnover in the community composition is largely associated to gradients temperature and precipitation, whilst nutrients –often reported as major driver for changes in peatland ecosystems– were only important at the end of the gradient of current deposition levels in Europe. Using a combination of species distribution modelling and species co-occurence patterns, we identified two spatially non–exclusive groups of plant species. Species within a distinct group responded similarly to bioclimatic variables and nutrient deposition levels, whilst between group response was mirrored. These results suggest that these two groups of plants are subjected to divergent environmental filters. Additionally, European peatlands aggregate into two distinct clusters based on plant functional trait composition. Each cluster was dominated by plant species from either one of the two co-response groups. Overall, our results demonstrate that environmental change results in a gradual replacement of plant species from two divergent groups, consequently affecting the functional trait composition in peatlands.