The SOC of steppe grasslands is more sensitive to grazing than desert-steppe grasslands and is regulated by precipitation outside the growing season in the Mongolian Plateau

Abstract

Purpose Soil organic carbon (SOC) predominates organic carbon pools in grassland. To address global climate change, it is essential to explore the soil organic carbon influencing factors and mechanisms. Method s We investigated the soil organic carbon (SOC) in 109 plots along the Mongolian Plateau grassland, which covers the desert-steppe and steppe. Specifically, we analyzed the SOC in the top 10 cm soil layer and its relationships with grazing intensity, climatic factors, soil properties, and vegetation diversity index. Results The average SOC of the desert-steppe (0.3%) was lower than that of the steppe (1.5%). In the desert-steppe, SOC did not vary with grazing intensity. In the steppe, SOC varied significantly with grazing pressure. Significant negative relationships were found between the SOC and growing season temperature (GST) and growing season aridity index (GSR) in the two regions. The responses of SOC to mean annual precipitation (MAP), growing season precipitation (GSP), and outside growing season precipitation (OGSP) in two types of grasslands were different. GST and soil EC were respectively identified as the major positive and negative factors influencing the SOC in the desert-steppe; the OGSP and soil PH were the major positive factors influencing the SOC in the steppe. Conclusion Out results proposed that soils of steppe grasslands have a large carbon sink potential but are more susceptible to grazing. These findings enhance our understanding of the different mechanisms of SOC in different grasslands along the Mongolian Plateau, which are crucial for predicting the effects and consequences of environmental change on carbon sequestration.