Distribution characteristics and influencing factors of soil organic carbon in alpine desert ecosystem of Qinghai Province

Yangong Du^1,2#, Boliang Cui^1#, Xun Ke^2#, Jingmei Li^1,3, Guangmin Cao², Kelong Chen¹*

¹ College of Geosciences, Qinghai Normal University, Xining, China, 810005

² Qinghai Provincial Key Laboratory of Restoration Ecology for Cold Region, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, China, 810008

³ Qinghai Academies of Social Sciences, Xining, China, 810012

Correspondence E-mail: caogm@nwipb.cas.cn, ckl7813@163.com

Abstract: Alkaline deserts soils acted as important soil pools in arid and semiarid regions. Contents of soil organic carbon (SOC) and its driven factors remained still not clear in alpine deserts on the Tibetan Plateau. In this study, we analyzed 223 soil organic carbon contents and total nitrogen and pH values, and its space distribution pattern under 0-30 cm. It was indicated that average and median SOC were approximate 4.86 and 3.80 g/kg with variation coefficient of 81.14%. SOC contents ranged from 0.54 to 24.34 g/kg. Soils organic carbon contents were divided into four groups. The largest group was around 3.32 g/kg (145 sites) when air temperature and altitude were higher than 1.49 ^oC and 2793 m. Alpine desert SOC were mainly controlled by total nitrogen (TN) and pH and precipitation with R² of 0.87 (P<0.001). Furthermore, soil pH was positively affected by air temperature not precipitation (P<0.05). Models may predict SOC through precipitation, air temperature and altitude (R²= 0.40, P<0.001). In addition, increasing regional precipitation perhaps decreased desert soils organic carbon storage in future climate scenarios.

Key words: SOC, alpine deserts, precipitation, generalized additive models

Global mean temperature was 1.2 ± 0.1 °C above the 1850–1900 baseline in 2020, the past six years have been the six warmest years on record (WMO 2020). Increasing atmosphere greenhouse gases have been the major driver of global warming due to anthropogenic activities (Bossio et al., 2020, Topa et al., 2021).

Increasing soil carbon is an appealing way to prevent carbon emissions (Bossio et al., 2020, Feyissa et al., 2021). Soil organic carbon (SOC) may represent 25% of the potential of natural climate solutions (Bossio et al., 2020). Chinese land biosphere was a robust sink of 1.11 ± 0.38 petagrams of carbon, and Tibetan Plateau ecosystems covered about 10% (Wang et al., 2020). Alpine soils are increasingly recognized for carbon sequestration in high‐altitude ecosystems (Liu et al., 2016, Du et al., 2019, Zhou et al., 2021). Natural desert lands contain some 7.84 petagrams of organic carbon in China (Feng et al., 2002). Deserts soil organic carbon contents were 4.37, 2.12 and 1.50 g/kg in the northwestern China, Norwest Mexico and Israel Negev desert (Mamat et al., 2011, Drahorad et al., 2013, Ayala-Niño et al., 2020).

Soil family types and land use were main driver factors on SOC contents and storage (Bai and Zhou 2020, Vries et al., 2020). Grassland types affected ecosystem carbon densities and contents (Liu et al., 2016, Du et al., 2019). Root-derived inputs are major contributors to soil carbon in temperate land ecosystems (Keller et al., 2021). Increased soil available nutrients had higher positive effects on carbon contents (Topa et al., 2021). Improving N-use efficiency are important for decreasing soil carbon losses from acidification (Frac et al., 2020, Raza et al., 2020). Soil nitrogen nitrification and denitrification rates increased significantly with pH (Drahorad et al., 2013, Feyissa et al., 2021). Addition of minimum temperature led to a significant increase in soil carbon sequestration capacity (Zhou et al., 2021). Desert grasslands SOC decreased with mean annual temperature, but increased significantly with annual precipitation (Feng et al., 2002, Drahorad et al., 2013, Wang et al., 2014). Greenhouse gas emissions from peatlands drained for agriculture could be greatly reduced (Cooper et al., 2020, Evans et al., 2021). Temperature and precipitation interaction significantly affected SOC density in alpine steppe (Liu et al., 2016).

Qaidam Basin covered an area over 250,000 km² (Tan et al., 2009). However, SOC contents distribution characteristic and its driven factors were underlying indistinct on the Tibetan Plateau. In this study, we hypothesized that significant regional variability changes in SOC contents in Qinghai. Moreover, soil pH and precipitation and air temperature significant affected SOC contents in alpine deserts.