Depth-Dependent Controls Over Soil Organic Carbon Stock across Chinese Shrublands

• Published in: Ecosystems (New York) 2023-03, Vol.26 (2), p.277-289
• Main Authors: Ge, Jielin, Xu, Wenting, Xiong, Gaoming, Zhao, Changming, Li, Jiaxiang, Liu, Qing, Tang, Zhiyao, Xie, Zongqiang
• Format: Article
• Language: English
• Subjects: Analysis; Biomedical and Life Sciences; Carbon; Carbon content; Carbon cycle; Climate effects; Ecology; Environmental Management; Geoecology/Natural Processes; Hydrology/Water Resources; Life Sciences; Multilayers; Organic carbon; Organic soils; Plant Sciences; Random sampling; Seasonal variations; Shrublands; Soil depth; Soil profiles; Soil properties; Soils; Statistical sampling; Stocks; Subsoils; Terrestrial ecosystems; Topsoil; Zoology
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-022-00757-6

Soil organic carbon (SOC) in shrublands is an important component of global carbon cycling. However, there is a dearth of large-scale systematic observations of SOC stocks at different soil depths, and it remains uncertain whether and how the relative importance of biotic and abiotic variables in regulating SOC stocks changes with soil depth. Here, we quantified large-scale patterns and controlling factors of SOC storage per area (SOCD, kg m −2 ) for both topsoils (0–30 cm) and subsoils (30–100 cm) by taking full advantage of a consistent stratified random sampling study of one-meter soil profiles across 1211 sites in Chinese shrublands. We found that subsoils stored about 53.30% of total SOCD, falling into the range of previously reported values for terrestrial ecosystems. SoilGrids250m model-derived assessments overestimated SOCD by 13.72 and 65.49% for topsoils and subsoils, respectively. The effects of climate means and seasonality on SOCD were equally strong in both topsoils and subsoils. The predominant effects of edaphic properties on SOCD were more robust in subsoils than in topsoils. Belowground biomass of shrublands was the only significant predictor of topsoil SOCD, but it did not predict subsoil SOCD accurately. These findings have refined our understanding of the pivotal role of shrublands in SOC storage and sequestration potential and could serve as an ecologically valuable baseline for large-scale improvement and validation of depth-dependent SOC dynamics for multilayer SOC modules in Earth Systems Models.