The assessment of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions from excreta patches of grazing grasslands and pasture under a variety of soil and seasonal conditions needs to be improved particularly, and the uncertainly attached to the size of the various sources needs to be reduced. In order to clarify this contribution, in this study CH4, CO2, and N2O fluxes were measured from experimental yak excreta patches placed on the alpine meadow of the plateau during the summer grazing seasons in 2005 and 2006. Dung plots was CH4 source (average 687 μg m-2 h-1)during the investigation period of two years, while urine (-34 μg m-2 h-1) and control plots (-39 μg m-2 h-1) consumed CH4. The cumulative CO2 emission at dung plots (average 12644 kg ha-1 in 2005 and 2006) was significantly higher than at control plots (average 8869.5 kg ha-1 in 2005 and 2006) throughout the investigation period. The cumulative N2O emission at urine and dung plots was 2.1~3.7 times and 1.8~3.5 times higher than at control plots both of the two years. However, although yak excreta patches significant affect GHGs fluxes, their contribution for the whole grazing ecosystem in terms of CO2 equivalents can be ignored due to small areas (approximately 3% of the whole grazing ecosystem) covered by excreta patches under moderate grazing intensity (1.45 yak ha-1) during the investigation period. Soil water-filled pore space (WFPS) explained 35% and 36% of CH4 flux variation at urine and control plots, respectively; soil temperature explained about 40%-75% of temporal variation in CO2 emissions for all treatments; temporal N2O flux variation at urine (34%), dung (48%), and control (56%) plots was mainly driven by the simultaneous effect of soil temperature and WFPS.
The study has published on SBB：
Xingwu Lin, Shiping Wang*, Xiuzhi Ma, Guangping Xu, Caiyun Luo, Yingnian Li, Gaoming Jiang, Zubin Xie. 2009. Fluxes of CO2, CH4, and N2O in an alpine meadow affected by yak excreta during summer grazing periods on the Qinghai-Tibetan plateau. Soil Biol. Biochemistry. 41:718-725 (Corresponding author)