Dynamics of a mountain grassland: Environment predicts long‐term trends, while species' traits predict short‐term fluctuations.

Aims: Dynamics of plant communities are an outcome of species' responses to the external environment influenced by species' life history, growth patterns and their mutual interactions. We aimed to disentangle the long‐term directional trends, likely associated with decadal change in environmental conditions, from short‐term species fluctuations. Location: Krkonoše Mountains, North Bohemia, Czech Republic. Method: To disentangle these processes, we used data from four plots in a temperate mountain grassland recorded yearly from 1985 to 2019. Results: We identified distinct types of temporal dynamics of individual species (using Fourier analysis) as well as directional shifts in abundance of individual species. Species fluctuations were best predicted by species' traits (namely taller species and those with a larger bud bank being less likely to fluctuate), likely due to demographic processes specific for individual species within the community. In contrast, directional trends were better predicted by species' environmental preferences expressed by Ellenberg indicator values. We found consistent shifts in vegetation composition towards that with higher Ellenberg indicator values for soil reaction and light and lower indicator value for moisture, which can be explained both by the global change and local factors. Conclusion: Our results thus show that short‐term dynamics of individual species is determined by their traits, while long‐term trends of a grassland community are determined by the environmental change. [ABSTRACT FROM AUTHOR]