International audienceSpecific composition and species clonal traits were characterized along combined flooding and grazing gradients to answer two questions. i) To what extent does the interaction of flooding and grazing influence the clonal characteristics of the vegetation? ii) Are the effects of both environmental factors independent or interactive? This study was carried out in a wet meadow along the Atlantic coast (France). Three plant communities (hygrophilous, mesohygrophilous and mesophilous) were distinguished along a flooding gradient and five levels of grazing pressure were controlled through an experimental design (from no grazing to heavy grazing). We monitored species composition and retrieved, for each species, the type of clonal growth organs (CGOs) and clonal traits from the CLO-PLA3 database. We identified two syndromes of clonal traits: "above-ground splitters" and "below-ground integrators". Clonal traits played a key role in plant assembly in the studied meadows. The interaction of both environmental factors selected for particular syndromes of clonal traits; however, flooding had a stronger filtering effect than grazing. The hygrophilous community was dominated by above-ground splitters, whereas the meso-hygrophilous vegetation was dominated by below-ground integrators. In the mesophilous community, clonal composition was the most diverse and shared clonal traits with the vegetation of both the hygrophilous and meso-hygrophilous communities. Grazing impact on CGOs and clonal traits differed between plant communities, i.e., the effect of grazing was modulated by the flooding regime. This study confirmed that vegetation responses to grazing might depend on the pool of traits, primarily filtered by environmental factors such as flooding

Summary1. The study of plant demography has long been an important component of plant ecological studies. However, in plant communities, e.g. grasslands, where individual plants are not easily distinguished and often vary in size, a convenient method of describing the demography and its ecological consequences has been lacking. 2. The aim of this study was to discuss the potential for using the change in the probability of space occupancy as a measure of ecological success in plant population biology. This will be done by demonstrating how the change in the probability of space occupancy depends on the processes of colonization and survival, and demonstrating how colonization and survival probabilities may be estimated from repeated pin-point recordings at the same pin-position. Furthermore, it will be demonstrated how to calculate the sensitivity and elasticity of the change in the probability of space occupancy to colonization and survival probabilities. 3. The method is applied to a case of repeated pin-point data of the perennial grass Brachypodium phoenicoıdes that underwent different grazing regimes from 2001 to 2008 on xero-halophytic grasslands. 4. It was demonstrated that grazing affected both plant survival and colonization probabilities so that the estimated colonization and survival probabilities of B. phoenicoıdes were highest in the nongrazed regime. Furthermore, using the calculated elasticity of the change in space occupancy, we found that survival was more important than colonization events in determining the ecological success of B. phoenicoıdes in the non-grazed regime, whereas colonization events were more important than survival in the grazed regime. 5. Synthesis and applications. We expect that the relatively simple method may be widely used on existing and future repeated pin-point recordings from the same pin-position and, consequently, that plant demographic questions may be addressed with larger precision in plant communities where individual plants are not easily distinguished.