Annual methane budgets of sheep grazing systems were regulated by grazing intensities in the temperate continental steppe: A two-year case study

摘要

AbstractMethane (CH4) emission from animal husbandry accounts for a large percentage of anthropogenic contributions to CH4emissions. Fully understanding of grazing management effects on the CH4budget is essential for mitigating CH4emissions in the temperate grazing steppe systems. Annual CH4budgets for the sheep grazed steppes at various grazing intensities, un–grazing (UG, 0 sheep ha−1year−1), defer grazing (DG, 1.0 sheep ha−1year−1), moderate grazing (MG, 1.43 sheep ha−1year−1), and heavy grazing (HG, 2.43 sheep ha−1year−1) were assessed across 2012–2014 in the agro–pastoral region of northern China. Annual soil CH4uptake averaged across 2012–2014 were 1.1 ± 0.1, 2.4 ± 0.2, 2.2 ± 0.2, and 1.3 ± 0.1 kg CH4–C ha−1for UG, DG (only 2013–2014), MG and HG sites. Non–growing season CH4uptake comprised 50.0 ± 4.3% of annual CH4uptake in 2012–2013 and 37.7 ± 2.0% in 2013–2014. DG and MG significantly promoted annual soil CH4uptake (P < 0.05), while there was no difference between HG and UG (P > 0.05). Bell–shaped relationship was presented between stocking rates and soil CH4uptake (r2 = 0.59,P < 0.05). Annual soil CH4uptake significant linearly and positively correlated with root biomass (r2 = 0.30,P < 0.05). Annual CH4budgets for the grazed grasslands were −1.1 ± 0.1, 5.7 ± 0.6, 11.5 ± 1.5 and 15.5 ± 1.3 kg CH4–C ha−1year−1in UG, DG (only 2013–2014), MG and HG across 2012–2014. Soil CH4uptake could offset 29.7 ± 5.6, 15.9 ± 4.3 and 6.8 ± 1.0% of total annual CH4emissions from sheep, sheepfold and faeces in DG, MG, and HG. All grazed steppes are sources for atmospheric CH4and the magnitude is regulated by grazing intensities. Sheep CH4emissions for 1–g liveweight gain were 0.21, 0.32 and 0.37 g CH4–C in DG, MG and HG, respectively. DG is the recommended grazing management in this region to achieve greater herbage mass, higher sheep performance and lower CH4emissions simultaneously.Graphical abstractDisplay OmittedHighlights•Sheep grazing systems were net sources for atmospheric CH4.•Magnitude of CH4budget was determined by grazing intensity.•The non-growing season contribute 37.7–50.0% of annual soil CH4uptake for steppes.•Deferred and moderately grazing promoted soil CH4uptake.