[Effects of nitrogen supplementation on forage yield and quality of a degraded grassland in Hulunbuir, China.].

Long-term overuse of grasslands results in quantitative and qualitative decline of forage yield. Nutrient supplementation is a key strategy to improve forage yield. While mounting evidence showed that nitrogen (N) supplementation can increase forage yield, little is known about its impacts on forage quality. To understand the effects of N supplementation on forage quality at the community level, we carried out a field experiment in the meadow steppe of Hulunbuir. Our results showed that N supplementation significantly increased forage yield by 23%, which was mainly due to positive responses of perennial rhizomatous grass. The yield of other plant functional groups showed neutral response to N supplementation. The concentrations of crude protein, crude fat, and crude fiber varied significantly among different plant functional groups. Nitrogen supplementation significantly enhanced the concentration of crude protein in rhizomatous grass, bunchgrass, legume, and sedge. It enhanced the content of crude fat in rhizomatous grass but with no effect on other functional groups. Nitrogen supplementation had no effect on the concentration of crude fibre in all functional groups. At the community level, N supplementation significantly increased the concentrations of crude protein and crude fat. Our results are important for understanding the responses of forage production in meadow steppe under the scenarios of N enrichment.