Plant diversity effects are robust to cutting severity and nitrogen application in productive grasslands

摘要

The replacement of nitrogen fertilizer with nitrogen derived from N_2 fixation offers important economic and environmental advantages. We investigated the effects of plant diversity of grasses and legumes, nutrient application and cutting on ecosystemfunction (aboveground biomass) in a productive grassland system. We varied resource levels (two levels of nitrogen fertilizer) and biomass removal intensity (two levels of cutting height) across a gradient of plant diversity (four species: Lolium perenne, Phleum pratense, Trifolium pratense and Trifolium repens) and relative abundance (varying species proportions) over a period of three years. Aboveground biomass was on average 16.5% greater in mixtures than in monocultures. On average, the yield benefits due to increasing evenness of four species mixtures were at least as big as the effects of increasing nitrogen by 150 kg ha~(-1) yr~(-1). These results indicate the potential of grass-legume mixtures to provide yield benefits at moderate levels of nitrogen application.