Abstract
The establishment of sown pasture is an important agricultural practice in many landscapes. Although both native grassland and sown pasture play a key role in the global carbon cycle, due to lack of data and field experiments, our understanding of grassland CH4 fluxes and CO2 emissions remains limited, especially when it comes to sown pasture. We measured ecosystem respiration and CH4 fluxes in response to a variety of potential drivers (soil temperature, soil moisture, ammonium nitrogen, nitrate nitrogen and dissolved organic carbon) in CG (continuous grazing), RG (rotational grazing) and UG (ungrazed) plots in sown grassland for one year in Inner Mongolia. Fluxes of CH4 and ecosystem respiration were measured using static opaque chambers and gas chromatography. Grazing significantly reduced ecosystem respiration (p < 0.01), and grazing pattern significantly influenced respiration in CG and RG plots (p < 0.01). We find that the sown grassland is a net sink for atmospheric CH4. No influence of grazing pattern was observed on CH4 flux in CG, RG and UG (p > 0.05). Soil temperature is the most important factor influencing ecosystem respiration and CH4 flux in the sown grassland, with soil moisture playing a secondary role to soil temperature. Variation in levels of ammonium nitrogen, nitrate nitrogen and dissolved organic carbon had little influence on ecosystem respiration or CH4 flux (except in UG plots). The values obtained for ecosystem respiration of grasslands have a large uncertainty range, which may be due to spatial variability as well as differences in research methods. Mean CH4 fluxes measured only during the growing season were much higher than the annual mean CH4 fluxes.
Highlights
Methane (CH4 ) and carbon dioxide (CO2 ), two of the three major greenhouse gases (CH4, CO2, N2 O) play a significant role in the radiative balance of the earth’s atmosphere
The annual precipitation was above the longer-term average value (400 mm) and 82% of it occurred in June-September
Respiration plays a key role in the global carbon cycle and it can prominently influence Respiration plays a key role in the global carbon cycle and it can prominently influence soilsoil-atmospheric andsoil netorganic soil organic carbonstorage (SOC)[26]
Summary
Methane (CH4 ) and carbon dioxide (CO2 ), two of the three major greenhouse gases (CH4 , CO2 , N2 O) play a significant role in the radiative balance of the earth’s atmosphere. At some point in the future, because of the degradation and fragmentation of native grassland, reduction of grazing intensity on native grassland is likely to occur and the establishment of sown pasture will become essential, as it can alleviate the grazing pressure on native grassland and the imbalance in grassland use in terms of space and time [8,9] Though both native grassland and sown pasture play a key role in the global carbon cycle [10,11,12], due to lack of data and field experiments, our understanding of grassland CH4 fluxes and ecosystem respiration remains limited, especially for sown pasture
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