| Popis: |
In recent decades, agricultural intensification has led to a strong decline in biodiversity. Field margins are defined as the uncultivated herbaceous vegetation strip located between the cropland and an adjacent habitat. Field margins act as shelters and dispersal corridors for biodiversity in highly disturbed landscapes, and are critical to the maintenance of ecosystem services. However, they are also impacted by agricultural practices in neighbouring fields. Agricultural impacts are often studied at field to landscape scales, and rarely include national spatial extents. One of the challenges in large- scale studies is the lack of standardized monitoring schemes including both biodiversity and accurate estimation of agricultural practices. Here, we take advantage of a national monitoring scheme in 462 sites in France, to assess the effects of agricultural practices on field margin flora at different extents and resolutions. We used spatial simultaneous autoregressive and generalized dissimilarity models to assess the response of plant richness and composition to climatic, soil and landscape conditions, and to agricultural (fertilization, herbicides) and margin management drivers. Analyses were repeated at the site-level, 40 and 75 km resolutions, and at regional and national extents. We found that the impact of agricultural practices on species richness was important at the site-level, whereas climate and crop diversity were important at the 75 km resolution. It was the opposite for compositional variations, with climate being more important at the site-level, and fertilization and crop diversity at the coarsest resolution. There was a strong variation in the variance explained by models among regions, but climate effects were weaker within biogeographic units compared to the national level. Regional analyses revealed interactions between local and regional effects suggesting that specific agricultural practices have contrasting impacts depending on the regional context. To efficiently conserve biodiversity, we therefore suggest implementing an agricultural regulatory framework adapted to each region. |
