Decomposition and C, N and P release of Tibetan sheep dung from an alpine meadow with different stocking rates

Dung decomposition is a key process affecting the cycling of carbon (C), nitrogen (N) and phosphorus (P). However, dung decomposition and nutrients (i.e., C, N and P) cycling in relation to stocking rate are still poorly understood in the alpine meadow. In this study, we carried out a 720-days field experiment to explore the differences in composition, mass, decomposition and nutrient cycling between sheep dung collected from grazing grassland with a high stocking rate (HSRD) and a low stocking rate (LSRD). Our results demonstrate that the dung mass, and C, N and P return were significantly higher for HSRD, whereas the C and N content were significantly greater in LSRD. The time required to achieve 75 % C, N and P loss from HSRD was longer (859.06 to 2664.7 days) than that (806.6 to 2123.7 days) from LSRD. However, after 720 days of decomposition, the release rates of DM (dry matter), C and N from LSRD were lower than that from HSRD; as a result, the leaching and residual mass respectively accounted for 2.03 % and 31.95 % of the original C content in LSRD, which were lower than that in HSRD (2.45 and 36.48 %, respectively); N released into the atmosphere (37.13 %) from LSRD was greater than that (32.08 %) from HSRD. Our findings suggest that stocking rate may change dung quantity, composition and decomposition rate, affecting biogeochemical cycling processes in grassland ecosystems.