International audience1. Dry matter digestibility is a critical component of herbage nutritive value, a major service delivered by grasslands. The aim of this study was to test whether the dominance hypothesis applies to assess the impacts of environmental gradients and management regimes on thiscomponent of herbage nutritive value in permanent grasslands. 2. At the plant level, digestibility has been related to a number of functional traits, but whether this can be scaled up to the community level in species-rich grasslands and how such relationships are modulated by environmental conditions and management regimes remainunknown. Our primary objective was to test whether community-weighted means – species trait values weighted by the species abundance – of morphological, phenological and chemical traits could be used to explain variations in digestibility over a large range of climatic contexts,soil resource levels and management regimes. Our second objective was to explain variations in community digestibility within and among nine contrasting sites along large natural and man-induced environmental gradients.3. Over the whole data set, digestibility and most community-weighted means of traits responded to climatic factors and management regimes, but relations were not always significant when each site was considered separately. Community digestibility was significantly related to one or more plant traits within each site and to all of the measured traits when considering all the sites. Leaf dry matter content (LDMC) had the most consistent effects on digestibility, with a strikingly similar negative effect within each site. Potential evapotranspiration was negatively related to digestibility and contributed to explain a large part of the among-site variance. In addition, a low return interval of disturbance and a high disturbance intensity (biomass removal) were both associated with a high digestibility.4. Synthesis and applications. Disturbance regime, plant traits and local climate impacted dry matter digestibility roughly equally in grasslands. The effects of community composition on digestibility and its response to abiotic factors could be successfully captured by community weightedmeans of leaf dry matter content. This functional marker can be used to develop indicators and grassland management rules to support farmers in the refinement of their practices towards specific needs, such as target production outputs

Although agriculture is pointed to as being one of the major causes of biodiversity loss, it is now recognised that some farming practices, grazing in particular, represent central issues in the on-running debate on wildlife conservation. This paper analyses the relationship between agricultural pasture management and bird preservation, by focusing on the illustrative case study of breeding waders in wet grasslands. After a brief account of the knowledge on research investigating the effect of grazing management on wader distribution or abundance, we reviewed (i) sward structure (i.e. mean sward height and frequency of tussocks) requirements, and (ii) breeding phenologies of five wader species commonly associated with wet grasslands for nesting in Europe. We found differences between species in these two aspects of their biology. Investigating grassland management thus underlines that the question of the timing of grazing should be considered. Moreover, the fragmented characteristic of agricultural landscapes (i.e. a mosaic of fields) in which waders breed emphasises the spatial nature of this management. We examine three spatial scales (i.e. field, set of adjacent fields, landscape) relevant to bird biology and influenced by agricultural activities. Based on these findings, we analyse which livestock system constraints are essential to take into account in order to minimise conflicts between livestock production and conservation aims in marshes. Finally, we highlight possible directions for future research.

SUMMARYManaged grasslands provide environmental and agronomic services that can be predicted from the botanical and functional composition of the vegetation. These are influenced by management, edaphic and climatic factors. The present report set out to estimate and analyse the relative importance of management, soil and climate factors on botanical and functional characteristics of grassland vegetation. A set of 178 French grasslands having a large pedoclimatic and management gradient was selected, and information collected on botanical composition, pedoclimatic factors and management. Six vegetation characteristics were considered: two botanical (floristic composition and species dominance) and four functional (proportion of entomophilous species, number of oligotrophic species, leaf dry matter content and date of flowering). First, the links between the characteristics of the vegetation were analysed to check for any redundancy among them; all were kept. Second, it was demonstrated that botanical and functional characteristics were not driven by the same factors: functional composition was characterized by management, edaphic and climatic factors, whereas botanical composition was influenced mainly by climatic and edaphic factors plus other factors. Interactions between factors also have to be taken into consideration to predict botanical and functional composition of grasslands. Functional and botanical characteristics of vegetation help to predict ecosystem services delivered by grasslands and may be used in combination.

No abstract

No abstract