Arable plant diversity on conventional cropland-The role of crop species, management and environment

Arable plant assemblages are affected by a wide range of management and environmental factors. It is yet unclear which factors are the most important predictors of arable plant diversity and composition in contemporary agricultural landscapes. The dramatic decline in agro-biodiversity calls for strategies to reconcile production and biodiversity goals on the basis of sound knowledge about the determinants of farmland biodiversity. Based on surveys of the arable flora on 240 conventional maize and winter cereal (wheat and barley) fields in two regions of Germany, we assessed the importance of a large number of management, environmental and spatial predictors for arable plant abundance, species richness and community composition. All conventionally managed fields had very low plant diversity (3-6 species 100 m−2). A complete model with all examined factors explained 40 and 32% of the variation in species richness and 42 and 36% of the variation in community composition for the field interior and the field margin, respectively. The choice of crop and other management factors (sowing date, fertilisation, herbicide use and crop rotation) were identified as important predictors of arable plant diversity in contemporary fields. Our results show that unless agrochemical input is markedly reduced, the potential for increasing the floristic diversity of high-input cropland is small.