Abstract
A one-step community trait selection model is proposed and fitted to observed changes in pin-point plant cover data from a manipulated grassland experiment, in which the level of nitrogen input was varied. In the trait selection model, population growth is modelled, and the observed trait selection is partitioned into direct selection and selection that was mediated by interspecific interactions. The effect of a nitrogen gradient on the trait selection processes on canopy height, leaf dry mater content and specific leaf area was estimated. Both direct selection and selection that was mediated by interspecific interactions were important in the plant community selection process for the three investigated plant traits. The finding that interspecific interactions play an important role in community selection processes on plant traits is of general ecological importance.