Plant Feedback Aggravates Soil Organic Carbon Loss Associated With Wind Erosion in Northwest China

Soil organic carbon (SOC) loss caused by wind erosion can profoundly impact carbon (C) balance in arid and semiarid regions. Nevertheless, previous researches mainly focused on the direct effect of wind erosion through removing surface soil only but ignored its indirect effects associated with soil nitrogen (N) loss and subsequent reductions of plant productivity. To better understand the wind erosion effect on SOC storage, we conducted a large-scale field experiment by manipulating wind erosion at 371 sites in arid and semiarid regions of northwest China from 2014 to 2016. We further integrated an observation-based empirical equation of wind erosion process into a terrestrial biogeochemical model to evaluate the direct and indirect effects of wind erosion on SOC storage in northwest China. The observed results showed that direct SOC losses increased linearly with the square of wind speed but decreased nonlinearly with soil water content. Over the 34 years (1980-2013), simulated cumulative SOC losses associated with wind erosion in northwest China were 27.47 Tg C, among which the indirect effects contributed to 2.68 Tg C (9.76%). The indirect effect of wind erosion initially enhanced SOC storage by decreasing heterotrophic respiration from 1984 to 1988 but decreased SOC pool by reducing net primary productivity due to soil N loss under the long-term wind erosion scenario. This work, for the first time, quantified the indirect impact of wind erosion on SOC storage via feedback of suppressed plant productivity, which is crucial for the convincing assessment on SOC storage in arid and semiarid regions. Plain Language Summary Understanding the magnitude of soil organic carbon (SOC) loss caused by wind erosion is beneficial to assess SOC storage in arid and semiarid regions. Through integrating an empirical relationship of direct SOC loss with environmental factors from a large-scale field experiment by manipulating wind erosion into a terrestrial biogeochemical model, we simulated wind erosion effect on SOC storage in northwest China from 1980 to 2013. Results showed that wind erosion not only directly removed SOC but also decreased soil nitrogen content, leading to a reduction of plant productivity, and thus indirectly decreased SOC storage. This study reveals that omitting plant feedback due to soil nitrogen loss could underestimate wind erosion effect on SOC storage.