Landscape structure influences grassland productivity through plant functional diversity

Agriculture intensification led to the gradual destruction of semi-natural habitats and landscape simplification in the North-Western Europe. All these profound changes affected plant assemblages, especially in semi-natural ecosystems such as grasslands. They could have negative effects on the plant diversity and the related ecosystem functions, such as primary productivity. At the landscape scale this biodiversity-productivity relationship still have to be tested in real-world systems. It could have important economic implications concerning fodder production. We used a large-scale sampling design (30 landscape windows – 1 ×1 km) to quantify landscape structure variables (semi-natural habitat amounts and landscape heterogeneity), grassland plant taxonomic diversity and functional diversity calculated from multidimensional functional spaces (functional richness, evenness, dispersion), and grassland productivity (mean, temporal stability, spatial variability) derived from satellite image time-series. Taxonomic dissimilarity, functional evenness and functional dispersion of grassland plant assemblages were related to semi-natural habitat amount. Functional evenness and dispersion decreased with grassland amount whereas taxonomic dissimilarity and functional evenness increased with hedgerow amount. Only taxonomic and functional richness depended on landscape heterogeneity, and with a positive relationship. Grassland plant assemblages with a higher functional evenness presented a higher and more stable mean productivity. In addition to the direct effect of landscape heterogeneity on plant productivity, we demonstrated plant trait-mediated effect of landscape structure on mean and temporal stability of grassland productivity at the landscape scale. Landscape management, especially through the conservation of hedgerows can help maintain high and resilient production of fodder in the future as a result of their positive effects on plant functional diversity.