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Dryad

Data from: Turnover and nestedness drive plant diversity benefits of organic farming from local to landscape scales

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Jan 18, 2022 version files 65.89 KB

Abstract

Biodiversity-benefits of organic farming have mostly been documented at the field scale. However, these benefits from organic farming to species diversity may not propagate to larger scales, because variation in the management of different crop types and semi-natural habitats in conventional farms might allow species to cope with intensive crop management. We studied flowering plant communities using a spatially replicated design in different habitats (cereal, ley and semi-natural grasslands) in organic and conventional farms, distributed along a gradient in proportion of semi-natural grasslands. We developed a novel method to compare the rates of species turnover within and between habitats, and between the total species pools in the two farming systems. We found that the intra-habitat species turnover did not differ between organic and conventional farms, but that organic farms had a significantly higher inter-habitat turnover of flowering plant species compared to conventional ones. This was mainly driven by herbicide-sensitive species in cereal fields in organic farms, as these contained 2.5 times more species exclusive to cereal fields compared to conventional farms. The farm-scale species richness of flowering plants was higher in organic than conventional farms, but only in simple landscapes. At the inter-farm level, we found that 36% of species were shared between the two farming systems, 37% were specific to organic farms while 27% were specific to conventional ones. Thus, our results suggest that that both community nestedness and species turnover drive changes in species composition between the two farming systems. These large-scale shifts in species composition were driven by both species-specific herbicide and nitrogen sensitivity of plants. Our study demonstrates that organic farming should foster a diversity of flowering plant species from local to landscape scales, by promoting unique sets of arable-adapted species that are scarce in conventional systems. In terms of biodiversity conservation, our results call for promoting organic farming over large spatial extents, especially in simple landscapes, where such transitions would benefit plant diversity most.