CO2, CH4 and N2O flux changes in degraded grassland soil of Inner Mongolia, China

Abstract

The main purpose of this study was to explore the dynamic changes of greenhouse gas (GHG) from grasslands under different degradation levels during the growing seasons of Inner Mongolia, China. Grassland degradation is associated with the dynamics of GHG fluxes, e.g., CO 2 , CH 4 and N 2 O fluxes. As one of the global ecological environmental problems, grassland degradation has changed the vegetation productivity as well as the accumulation and decomposition rates of soil organic matter and thus will influence the carbon and nitrogen cycles of ecosystems, which will affect the GHG fluxes between grassland ecosystems and the atmosphere. Therefore, it is necessary to explore how the exchanges of CO 2 , CH 4 and N 2 O fluxes between soil and atmosphere are influenced by the grassland degradation. We measured the fluxes of CO 2 , CH 4 and N 2 O in lightly degraded, moderately degraded and severely degraded grasslands in Inner Mongolia of China during the growing seasons from July to September in 2013 and 2014. The typical semi-arid grassland of Inner Mongolia plays a role as the source of atmospheric CO 2 and N 2 O and the sink for CH 4. Compared with CO 2 fluxes, N 2 O and CH 4 fluxes were relatively low. The exchange of CO 2 , N 2 O and CH 4 fluxes between the grassland soil and the atmosphere may exclusively depend on the net exchange rate of CO 2 in semi-arid grasslands. The greenhouse gases showed a clear seasonal pattern, with the CO 2 fluxes of-33.63-386.36 mg/(m•h), CH 4 uptake fluxes of 0.113-0.023 mg/(m•h) and N 2 O fluxes of-1.68-19.90 µg/(m•h). Grassland degradation significantly influenced CH 4 uptake but had no significant influence on CO 2 and N 2 O emissions. Soil moisture and temperature were positively correlated with CO 2 emissions but had no significant effect on N 2 O fluxes. Soil moisture may be the primary driving factor for CH 4 uptake. The research results can be in help to better understand the impact of grassland degradation on the ecological environment.

Diel and Seasonal Dynamics of Ecosystem‐Scale Methane Flux and Their Determinants in an Alpine Meadow

“…Although soil moisture is commonly considered a critical factor controlling methane production and oxidation, we found no correlation between soil moisture and the seasonal CH 4 uptake in this study. Our result differed from some other studies in grassland ecosystems (Bai et al, 2018;Dijkstra et al, 2013;Zhao et al, 2017), mainly due to that soil 10.1029/2019JG005011 Journal of Geophysical Research: Biogeosciences moisture is not the most important limiting factor in alpine meadow as that in the temperate semiarid steppe.…”

Effects of Grazing Pattern on Ecosystem Respiration and Methane Flux in a Sown Pasture in Inner Mongolia, China

“…Other studies also found that soil temperature and soil moisture played the major role in driving the temporal CO 2 emission variation [35,36]. For example, Bai et al think that soil moisture and temperature were positively correlated with CO 2 emissions [35]. Sun et al obtained similar the same results of Bai et al, they pointed out that temporal variations of CO 2 emission were strongly correlated with air and sediment temperatures [36].These results suggest that higher soil temperatures affect the root systems, enhancing root respiration and microbiological activity along with soil organic matter mineralization [37].…”

“…Using a stepwise multiple regression analysis, the authors found that soil volumetric water content, soil temperature and aboveground green biomass were the three main factors that affect ecosystem respiration, and that aboveground green biomass was the primary factor related to ecosystem respiration [16]. Other studies also found that soil temperature and soil moisture played the major role in driving the temporal CO 2 emission variation [35,36]. For example, Bai et al think that soil moisture and temperature were positively correlated with CO 2 emissions [35].…”