Recent changes in mountain hay meadows of high conservation value in eastern France

Aim To assess vegetation changes in mountain hay meadows of high conservation value over 15 years. Location Jura Mountains and Vosges Mountains (France). Methods In 2019, we resampled old phytosociological releves (made from 2005 to 2009) in extensive mountain hay meadows. To detect shifts in composition from old to recent releves, we performed a permutational multivariate analysis of variance, and visualized observed patterns using non-metric multidimensional scaling on the Bray-Curtis dissimilarity matrix of the vegetation data. We tested for differences in taxonomic, functional and phylogenetic diversity metrics, CSR strategies and ecological indicator values using paired Wilcoxon-Mann-Whitney tests. Results Non-metric multidimensional scaling paired with a permutational multivariate analysis of variance showed that, overall, old and recent plant communities were not different in the Vosges Mountains, contrary to the situation in the Jura Mountains. Wilcoxon-Mann-Whitney paired tests revealed that, in the Jura Mountains, plant communities underwent a significant decrease in taxonomic, functional and phylogenetic diversity, associated with an increase of ruderal and competitive strategies. Ecological indicator values for nutrient availability and defoliation tolerance both increased, suggesting an intensification of agricultural practices. In the Vosges Mountains, only species richness increased while the inverse Simpson index and Pielou evenness decreased. Conclusions Our results show that plant diversity is not currently threatened in the studied grasslands in the Vosges Mountains. By contrast, in the studied grasslands in the Jura Mountains, plant diversity is declining. The situation in the Vosges shows that agricultural activities and biodiversity conservation can be reconciled. This situation should be further investigated to help resolve conflicts between agriculture and biodiversity conservation in semi-natural grasslands.