Research

Maintaining and restoring connectivity are proposed as a key landscape-level strategy to mitigate biodiversity loss in fragmented landscapes. However, there is a limited consensus about its efficiency for plant communities. To deepen and broaden our understanding about the role of connectivity, this PhD thesis aims to determine the effect of connectivity and its temporal connectivity on the taxonomic and the functional structure of plant communities. Carried out in the LTSER Zone Atelier Armorique, this study focuses on three dominant habitat types in agricultural landscapes (woodlands, grasslands and winter cereal crops). The connectivity provided by the different habitat types and its temporal dynamics (the magnitude and the variability of the temporal changes in connectivity) do not affect species diversity nor the total abundance of species. Rather, they shape species composition of plant communities, selecting species identity depending on their functional trait values related to seed production and transport, as well as seedling recruitment. Below one kilometre, and over decades, connectivity thus shapes the functional structure of plant communities, thereby affecting agroecosystem functioning. We reveal then new insights into the specific interaction between landscape and plant dispersal. Of note, the connectivity provided by other habitat types can impede or facilitate the dispersal of species of a given habitat type. We also showed that the magnitude and the variability of changes in connectivity over the last seven decades are still shaping current communities. Overall, our results may have far-reaching implications for plant biodiversity in agricultural landscapes, its conservation depending, in part, on the relevance and the effectiveness of the actions deployed under the Green and Blue Belt Network policy.