Nitrogen deposition intensification influences nutrient cycling in grassland ecosystems， yet plant nutrient responses under grazing and enclosure remain unclear. This study conducted a two-year multi-level nitrogen addition experiment in an alpine steppe in Qinghai to investigate the responses of nitrogen （N） and phosphorus （P） contents at both the plant functional group and community levels to nitrogen addition under enclosure and grazing conditions. The results showed that N addition significantly increased the N concentrations in grasses， sedges， forbs， and the community as a whole （P<0.001）， but had no significant effect on legumes （P>0.05）； N addition significantly enhanced the P concentrations in grasses， sedges， and the community （P<0.001）， while significantly reducing that in legumes and forbs （P<0.05）. Management practices further regulated the nutrient response pathways： under enclosure condition， nitrogen addition primarily induced a phosphorus dilution effect， thereby increasing the N∶P； while under grazing condition， it promoted nitrogen absorption and altered phosphorus dynamics， leading to an elevated N∶P， with the overall N∶P being higher in enclosed grasslands. The study demonstrated that grazing and fencing， as distinct management approaches， were key factors regulating the response of plant nutrients to nitrogen deposition in the alpine steppe， holding significant implications for understanding regional nutrient limitations and guiding sustainable grassland management.

Fencing  /  Grazing  /  Nutrients addition  /  Alpine grassland  /  Plant functional groups  /  Plant nitrogen and phosphorus content