4.2 Controlling process of soil chemical characteristic and climate factors on SOC in alpine deserts
Over 6% of the world’s land is affected by the salinity across 100 countries mostly in arid and semiarid regions (Datta et al., 2020, Martínez-García et al., 2020). Deserts soils play a vital role in regulating greenhouse gases concentrations in the atmosphere (Drahorad et al., 2013, Topa et al., 2021). Desert grasslands use may improve the status of soil organic carbon and nitrogen dynamics (Frac et al., 2020).
Nitrogen is essential to regulate the ecosystem functions and services (Ke et al., 2018). A close spatial similarity was observed between SOC contents and total nitrogen (Motaghian and Mohammadi 2012). SOC was significantly correlate with total nitrogen (r=0.997, P<0.01) in the desert of Minqin (Wang et al., 2019). In present study, deserts soil organic carbon contents were also positively driven by total nitrogen. Nowadays, average annual nitrogen deposition increased by approximately 8 kilograms per hectare between the 1980s and the 2000s (Liu et al., 2013). Deserts soil organic carbon contents would increase significantly with adding nitrogen deposition.
Soil pH can affect the content of soil organic carbon by changing plant growth and soil respiration (Chen et al., 2019, Berdugo et al., 2020). The spatial distribution of SOC is related to pH and annual precipitation in Israel deserts (Drahorad et al., 2013). Desert SOC contents were negatively correlated with soil pH (Chen et al., 2019). In addition, we also discovered that soil pH was negatively affected SOC contents in Qaidam basin. It was because there are different degrees of salinization in desert ecosystems. Furthermore, growth of vegetation was seriously restricted by high saline alkali soil, and it greatly reduced the input of soil organic carbon.
Precipitation was driven factor on SOC contents across the desert ecosystem of Hexi Corridor (Ke et al., 2018). The SOC concentrations were significantly positively correlated with annual precipitation in northern China (Chen et al., 2019). Microbial activity decreased strongly in saline soils by decreasing osmotic potential at lower water content (Datta et al., 2020). Mean annual temperature was more important to determine SOC than other abiotic factors in arid desert grasslands (Wang et al., 2014). In this study, it was indicated that deserts SOC was significantly driven by precipitation in Qaidam basin. Over the past several decades, Tibetan Plateau showed an increase in precipitation (Piao et al., 2010, Liu et al., 2018). Then, increasing regional precipitation perhaps decreased desert soils organic carbon storage in future climate scenarios.