Towards the assessment of biodiversity and management practices in mountain pastures using diagnostic species?

International audience

anglais. Diversity of plant communities in semi-natural grasslands is strongly dependent on management practices. Tocharacterize community diversity and agricultural practices, we need easy-to-use indicators. The diagnosticspeciesareusedtocharacterizeanddifferentiatevegetationtypes,butaretheyusefultoassessthevariousfacetsof community diversity and the agricultural practices applied to managed grasslands?Based on the fidelity analysis of 311 phytosociological relevés, considered as references for mesic grasslandclassification in the Franche-Comté region (eastern France), we identified eight diagnostic species of mesicpastures (Cynosurion cristati). We then compared the number of diagnostic species observed in 45 mountainpastures with taxonomic, phylogenetic and multi-trait functional diversity indices, as well as with agronomicvariables describing stocking rate and fertilization. To account for the role of diagnostic species identity, wecomparedSpearmanrankcorrelationsobtainedforthesediagnosticspecieswithcorrelationscalculatedfor1000random samples of eight species from the regional species pool of mesic grasslands.The number of diagnostic species in the grassland plot was significantly positively correlated with mosttaxonomic,phylogeneticandfunctionaldiversitymetrics.However,onlythepositivecorrelationswithSimpsontaxonomic diversity and Rao functional diversity were significantly different from those obtained from randomsamples. Moreover, the number of diagnostic species was significantly negatively correlated with stocking rateand fertilization intensity,although onlycorrelationswith industrialfertilizer input weresignificantly differentfrom results obtained from random samples.These results show thatthe numberofdiagnostic species observedin apasturemaybea goodindicator ofahightaxonomicandfunctionaldiversityandofalowfertilization.Thereby,aspecialattentionshouldbegiventodiagnostic species to assess the status of grassland biodiversity, including functional aspects.