Species composition in agroecosystems:: The effect of landscape, habitat, and farm management

It has been suggested that species richness in agricultural ecosystems depends on both landscape heterogeneity and farm management, but how these factors affect species composition is still poorly understood. In this study, we investigated the species composition of plants, butterflies, and carabid beetles in three different habitats (cereal fields, leys, and semi-natural pastures) in relation to farm management (conventional vs. organic) and landscape complexity at 16 farms in south-eastern Sweden. The farms were divided into eight pairs of one conventional and one organic farm based on land use, location, and landscape features to enable us to separate the effects of landscape features and farm management on species composition. Habitat type explained most of the variation in species composition of butterflies, carabids, and plants. Landscape features in the surrounding landscape explained additional variation, but little relative to habitat, in species composition. The effect of landscape features was larger in the disturbed habitats (cereal fields and ley) than in the more stable semi-natural pastures. Moreover, the effect of landscape features was largest for the most mobile group, butterflies, and least for the sessile plants. The percentage of ley (land temporarily with perennial grass and clover) was the most important landscape feature for butterfly and plant species composition, whereas landscape heterogeneity was the most important landscape feature for carabid species composition. Farm management explained some additional variation in species composition of carabids and butterflies, but it was of minor importance compared to landscape features for species composition of butterflies and plants. We classified the species as common or rare, but for no taxa were common or rare species associated with any landscape feature or farm management.