Biodiversity conservation strategies in agricultural landscape often recommend keeping margins of arable fields in natural conditions. However, effect of such management method has been estimated only in limited number of taxa and quantitative analysis on the optimal width of such 'green margins' is seldom conducted. We analysed the potential effect of such management method on small mammals, which form an important part in the food chain and thus belong to keystones of the ecosystem. We measured abundance of three rodent species at ecotones between forests and three types of open agricultural biotopes (grasslands, rapeseed fields and cereal fields).
The maximum density of rodents was found at the forest/grassland ecotone. Here the highest densities of the Yellow-necked Mouse Apodemus flavicollis and Striped Field Mouse A. agrarius were detected. The positive edge-effect did not exceed ten meters. Also the highest density of forest-dwelling Bank Voles Myodes glareolus was recorded next to grasslands, but the abundance of this species increased towards forest interior. Rodent densities at forest/arable field ecotones were 3-5 times lower than on the edges of grassland. Summarizing, our results support maintaining narrow grasslands at margins of crop fields. Such management practice would strengthen natural communities at ecotones, but also in adjacent open land and forests.