The impact of excretal returns from yak and Tibetan sheep dung on nitrous oxide emissions in an alpine steppe on the Qinghai-Tibetan Plateau

This study describes the impact of excretal returns derived from livestock dung on nitrous oxide (N2O) emissions in a grazed alpine grassland ecosystem. N2O flux, vegetation and soil characteristics were measured in an alpine steppe on the Qinghai-Tibetan Plateau. Measurements were obtained from control (CK) plot and experimental plot to which either yak dung (YD) or Tibetan sheep dung (SD) was added. We found significantly lower surface soil temperature and higher soil moisture in the YD plot than in either the CK or SD plot. The application of YD resulted in significantly less biomass of aboveground vegetation, lower carbon and nitrogen uptake, and significantly higher cumulative N2O emission in comparison to the CK or SD treatment. N2O from SD treatment was probably mainly produced via nitrification, while N2O from YD treatment was primarily produced by denitrification. Emission factors of N2O for both YD and SD were far lower than the default values proposed by the IPCC and the release of N2O from YD and SD patches is low.