Different responses of soil C:N:P stoichiometry to stocking rate and nitrogen addition level in an alpine meadow on the Qinghai-Tibetan Plateau

Abstract

Livestock grazing and nitrogen (N) deposition influenced most grasslands in the world by affecting the element contents and their stoichiometry in soil. Although the individual effects of grazing or N deposition on soil nutrients are well understood, how their interaction effects on soil stoichiometric characteristics are unclear. To reveal the response of soil carbon:nitrogen:phosphorus (C:N:P) stoichiometry to grazing and N deposition, we conducted an experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP), which included three stocking rates (0, 8 and 16 sheep ha−1) and four N addition levels (0, 50, 100 and 200 kg N ha−1 yr−1). The results showed that grazing had no significant impact on soil C:N:P stoichiometry. Nitrogen addition significantly increased soil total N and N:P ratio at the stocking rate of 8 sheep ha−1 in the surface soil. The interactive effects of grazing and N addition did not significantly affect soil C:N:P stoichiometry, however, the interplay between grazing and N addition caused vegetation changes, which had indirect effects on soil C:N:P stoichiometry. The differential responses of plants and soil indicated that soil was less sensitive to grazing and N addition than plants. Our findings indicated that N was still a major limit factor for plant growth in the alpine meadow of QTP, and hopefully, provided that stocking rate at 8 sheep ha−1 and N addition at 50 kg N ha−1 yr−1 could be a suitable grassland management technique for soil fertility sequestration in the QTP.