氮素补给对呼伦贝尔草甸草原退化草地牧草产量和品质的影响

长期过度利用导致我国草原的生产功能严重衰退,适量补充关键性养分元素是提升牧草产量的关键.以往研究表明,氮素输入可提升牧草产量,但对牧草品质的影响鲜有涉及.本研究以内蒙古草甸草原退化草地为对象开展控制试验,旨在明确氮素补给如何通过改变不同植物类群的牧草品质和植物群落结构影响群落水平上的牧草品质.结果表明: 氮素输入显著提升了牧草产量达23%,主要得益于根茎禾草类群的贡献; 氮素输入对其他植物类群的生产力无显著影响.不同植物类群的粗蛋白、粗脂肪、粗纤维含量均存在显著差异.氮素输入显著提高了根茎禾草、丛生禾草、豆科植物、苔草类植物的粗蛋白含量,提高了根茎禾草的粗脂肪含量,而对所有类群的粗纤维含量均无显著影响.在群落水平上,氮素输入显著提高了粗蛋白和粗脂肪含量.这对于理解氮素补给对草甸草原牧草生产的影响具有重要意义.

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.