Long-term study of an alpine grassland: local constancy in times of global change

The impact of climate change, especially on alpine vegetation is well documented. Here, we present the results of a long-term study on the vegetation composition of an alpine grassland (Caricetum curvulae) located in the central Alps, where we performed vegetation surveys since 1980. Our study comprised 99 non-permanent plots that were randomly distributed in the studied grassland and contained 59 species in total. We estimated species cover in each plot and conducted a detrended correspondence analysis to investigate changes in vegetation composition since 1980. We also calculated species richness, evenness, as well as Shannon diversity for each plot and computed Jaccard similarity between the plots of the same year as well as between the plots of 1980 and all subsequent years. Linear regression analyses were carried out to test these parameters for significant changes between 1980 and 2012. In the correspondence analysis, plots from all years were intermixed and the sampling year as a factor was not correlated with the axes. Species richness, evenness and Shannon diversity of the study plots, as well as the Jaccard similarity between the plots of the same year and between plots of 1980 and all subsequent years did not change significantly since 1980. The cover of individual species within plots changed significantly for only six out of the 59 identified species. Polygonum vivparum and Oreochloa disticha decreased, whereas Vaccinium vitis-idea, Luzula alpina, Avenochloa versicolor, and Agrostis rupestris increased significantly since 1980. The results of our study revealed almost no changes in vegetation composition and only very small changes in species cover, although temperature continuously rose since 1980. This local constancy in times of global change can most likely be attributed to the extreme longevity of many alpine grassland species and, therefore, to the persistence of alpine grasslands.