Grazing alters sandy soil greenhouse gas emissions in a sand-binding area of the Hobq Desert, China

Deserts are sensitive to environmental changes caused by human interference and are prone to degradation. Revegetation can promote the reversal of desertification and the subsequent formation of fixed sand. However, the effects of grazing, which can cause the ground-surface conditions of fixed sand to further deteriorate and result in re-desertification, on the greenhouse gas (GHG) fluxes from soils remain unknown. Herein, we investigated GHG fluxes in the Hobq Desert, Inner Mongolia Autonomous Region of China, at the mobile (desertified), fixed (vegetated), and grazed (re-desertified) sites from January 2018 to December 2019. We analyzed the response mechanism of GHG fluxes to micrometeorological factors and the variation in global warming potential (GWP). CO2 was emitted at an average rate of 4.2, 3.7, and 1.1 mmol/(m(2)center dot h) and N2O was emitted at an average rate of 0.19, 0.15, and 0.09 mu mol/(m2 center dot h) at the grazed, fixed, and mobile sites, respectively. Mean CH4 consumption was as follows: fixed site (2.9 mu mol/(m(2)center dot h))>grazed site (2.7 mu mol/(m(2)center dot h))>mobile site (1.1 mu mol/(m(2)center dot h)). GHG fluxes varied seasonally, and soil temperature (10 cm) and soil water content (30 cm) were the key micrometeorological factors affecting the fluxes. The changes in the plant and soil characteristics caused by grazing resulted in increased soil CO2 and N2O emissions and decreased CH4 absorption. Grazing also significantly increased the GWP of the soil (P<0.05). This study demonstrates that grazing on revegetated sandy soil can cause re-desertification and significantly increase soil carbon and nitrogen leakage. These findings could be used to formulate informed policies on the management and utilization of desert ecosystems.

Automated summary

Deserts are highly sensitive to human-induced environmental changes and require re-vegetation to reverse desertification. However, grazing may further deteriorate fixed sand and lead to re-desertification, and its effects on soil greenhouse gas fluxes remain unclear.