Abstract
Understanding how land‐use changes affect different facets of plant biodiversity in seminatural European grasslands is of particular importance for biodiversity conservation. As conclusions of previous experimental or synchronic observational studies did not converge toward a general agreement, assessing the recent trends in vegetation change in various grassland systems using a diachronic approach is needed. In this resurvey study, we investigated the recent changes in grassland vegetation of the French Jura Mountains, a region with a long tradition of pastoralism. We compared the floristic composition of 150 grassland plots recorded between 1990 and 2000 with new relevés made in 2012 on the same plots. We considered taxonomic, phylogenetic and functional diversity as well as ecological characteristics of the plant communities derived from ecological indicator values and life strategies of the species. PCA of the floristic composition revealed a significant general trend linked to the sampling year. Wilcoxon paired tests showed that contemporary communities were generally more dominated by grass species and presented a higher tolerance to defoliation, a higher pastoral value, and a higher nutrient indicator value. Comparisons revealed a decrease in phylogenetic and functional diversity. By contrast, local species richness has slightly increased. The intensity of change in species composition, measured by Hellinger distance between pairs of relevés, was dependent on neither the time lag between the two surveys, the author of the first relevé nor its location or elevation. The most important changes were observed in grasslands that previously presented low pastoral value, low grass cover, low tolerance to defoliation, and high proportion of stress‐tolerant species. This trend was likely linked to the intensification of grassland management reported in the region, with a parallel increase in mowing frequency, grazing pressure, and fertilization level. More restrictive specifications should be applied to agricultural practices to avoid overexploitation of mountain species‐rich grasslands and its negative consequences on their biodiversity and resilience.
Highlights
Grassland ecosystems often comprise high plant species richness at fine scale and contribute to biodiversity conservation at larger scale
Ecology and Evolution published by John Wiley & Sons Ltd
We considered the ecological indicator values given by Landolt et al (2010), as floristic composition gives useful information on ecological conditions
Summary
Grassland ecosystems often comprise high plant species richness at fine scale and contribute to biodiversity conservation at larger scale. Seminatural, temperate European grasslands, managed for a long time with low-intensity grazing or mowing, are the communities with the world records for vascular plant species richness at very small spatial grain (Wilson et al 2012). As predicted by the insurance hypothesis (Yachi and Loreau 1999), a positive effect of species richness on productivity has been found in artificial grasslands, increasing over time (Reich et al 2012). A recent meta-analysis of experimental studies on such artificial species assemblages suggested that species richness generally improves resistance of grassland productivity to climatic extreme events, but not its recovery rate (Isbell et al, 2015).
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