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Previous research has investigated the effects of different grazing intensities on soil surface greenhouse gas (GHG) emissions, whereas the dynamics of GHG production and consumption within the soil profile and their responses to different grazing intensities remain unclear. In this study, a field experiment was conducted in 2017 and 2018 to evaluate the influences of three grazing intensities (none, light, heavy) on both soil surface and subsurface (0–60 cm) GHG fluxes estimated using chamber-based and concentration gradient-based methods, respectively. Results showed that soil at lower depths (30–60 cm) had higher carbon dioxide (CO2) concentrations but lower methane (CH4) concentrations. In contrast, soil profile nitrous oxide (N2O) concentration did not vary with depth, possibly resulting from the relatively low soil moisture in the semiarid grassland, which increased air diffusivity across the soil profile. Grassland soil acted as a source of N2O and CO2 production but as a sink for CH4 uptake, which mainly attributed to the topsoil (0–5 cm for N2O, and 0–15 cm for CO2 and CH4). The estimated soil surface GHG flux rates based on the concentration gradient method did not align well with those directly measured using the chamber method. Furthermore, the cumulative N2O flux over the study period was significantly higher for the concentration gradient method than the chamber method, whereas a contrary result was observed for CO2 emission and CH4 uptake. This study confirms that the grassland soil serves as an important source of CO2 and N2O emissions and a weak sink for CH4 consumption, playing a crucial role in the annual carbon budget of livestock-grazed grassland ecosystems.
Details
Grazing intensity;
Livestock;
Nitrous oxide;
Topsoil;
Luminous intensity;
Soil moisture;
Grazing;
Emissions;
Grasslands;
Soil properties;
Methane;
Greenhouse gases;
Sheep;
Carbon dioxide;
Consumption;
Livestock grazing;
Chambers;
Simplex method;
Carbon;
Soil profiles;
Concentration gradient;
Carbon dioxide emissions;
Methods;
Soil dynamics;
Fluxes;
Soil surfaces
; Li, Yanyan 3
; Wu, Yufeng 4 ; Kuang, Wennong 5
; Zeng, Fanjiang 6 1 Liaoning Key Laboratory of Urban Integrated Pest Management and Ecological Security, College of Life Science and Engineering, Shenyang University, Shenyang 110044, China; State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;
2 Department of Soil Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
3 Key Laboratory of Agro-Ecological Processes in Subtropical Region and Changsha Research Station for Agricultural & Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China;
4 College of Life Science, Shihezi University, Shihezi 832003, China;
5 Research Center of Forest Management Engineering of State Forestry and Grassland Administration, Beijing Forestry University, Beijing 100083, China;
6 State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;