title: Recent changes in mountain grasslands: a vegetation resampling study.
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.
authors.affiliation: Université Bourgogne Franche-Comté - CNRSUMR 6249 Chrono-environnement 16 route de Gray 25030 Besançon Cedex France; Ecole Polytechnique Fédérale de Lausanne Laboratory of Ecological Systems Station 21015 Lausanne Switzerland.
authors.forename: François
authors.identifier: 0000-0002-3334-1069
authors.initials: F
authors.lastname: Gillet
authors.affiliation: Université Bourgogne Franche-Comté - CNRS UMR 6249 Chrono-environnement 16 route de Gray 25030 Besançon Cedex France.
authors.forename: Leslie
authors.initials: L
authors.lastname: Mauchamp
authors.affiliation: Université Bourgogne Franche-Comté - CNRS UMR 6249 Chrono-environnement 16 route de Gray 25030 Besançon Cedex France.
authors.forename: Pierre-Marie
authors.initials: PM
authors.lastname: Badot
authors.affiliation: Université Bourgogne Franche-Comté - CNRS UMR 6249 Chrono-environnement 16 route de Gray 25030 Besançon Cedex France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Mouly
keywords: Anthropogenic changes; CSR strategies; Jura Mountains; community diversity; diachronic survey; ecological indicator values; grassland; resampling vegetation plots; vegetation dynamics