Mowing weakens the positive effects of nitrogen deposition on fundamental ecosystem service of grassland

Abstract Forage yield is the fundamental ecosystem service of grasslands. While the quantitative responses of forage yield to nitrogen (N) enrichment are well known, its qualitative responses remain unclear. Even less known is the relative contribution of changes in community composition to the quality of the yield at the community level. We examined the quantitative and qualitative responses of forage yield at both plant functional group and community levels with factorial treatments of N addition and mowing in a temperate steppe. Nitrogen addition significantly enhanced the community-level yield by favoring the growth of rhizomatous grass. Mowing tended to mediate the impacts of N addition on the yield. Nitrogen addition increased the concentrations of crude protein and crude fat in forage at the community level. Neither the main effects of mowing nor its interactive effects with N addition affected forage quality. The N-induced shifts in plant species composition significantly contributed to the effects of N addition on forage quality at the community level. Our results suggest that mowing wound weaken the positive effects of N deposition on the quantity but not the quality of forage yield. Changes in plant community composition are important in driving the qualitative responses of yield to N deposition.