4.1 Soil organic carbon contents and its space patters in desert ecosystems
Paris Agreement aimed to hold air temperature below 2 °C above pre-industrial levels (WMO 2020). Protecting SOC pools could deliver many benefits to nature ecosystems and people (Bossio et al., 2020, Vries et al., 2020). Land biosphere absorbed approximately 45% of annual anthropogenic carbon emissions in China (Wang et al., 2020). Potential SOC stock would increase by 0.83 petagrams due to grassland restoration on Tibetan Plateau (Du et al., 2019).
Soil organic carbon and microbial biomass carbon contents varied remarkably among the different species communities in desert grasslands and shrubs (Mamat et al., 2011, Zhang et al., 2019). Average SOC contents of nondegraded and degraded grasslands were 34 and 24 g/kg on Tibetan Plateau (Du et al., 2019). SOC was 25.01 g/kg with 55.26% variation coefficient in karst mountainous area indicating moderate variation (Bai and Zhou 2020). Deserts soil organic carbon contents were 7.05, 3.94 and 1.56 g/kg in West Jilin Province and Inner Mongolia and Tarim Basin in China (Feng et al., 2002). Furthermore, desert soil organic carbon was 5.47 and 5.30 g/kg across Central Iran and India salt deserts, separately (Motaghian and Mohammadi 2012, Datta et al., 2020). It was indicated that deserts soc presented spatial heterogeneity.
In this study, desert soil organic carbon contents in Qaidam basin were higher than both Inner Mongolia and Xinjiang Tarim Basin. Furthermore, it was similar with Iran and India deserts. However, it was much lower than desert grasslands in Jilin Province. Meanwhile, we also revealed that much spatial heterogeneity has been existed in Qaidam basin. SOC contents ranged from 0.54 to 24.34 g/kg with variation coefficient of 81.14%. Therefore, SOC contents were affected by multifactor including precipitation, air temperature and soil characteristics.