Abstract
Abstract. Soil organic carbon (SOC) accounts for two-thirds of terrestrial carbon. Yet, the role of soil physicochemical properties in regulating SOC stocks is unclear, inhibiting reliable SOC predictions under land use and climatic changes. Using legacy observations from 141 584 soil profiles worldwide, we disentangle the effects of biotic, climatic and edaphic factors (a total of 31 variables) on the global spatial distribution of SOC stocks in four sequential soil layers down to 2 m. The results indicate that the 31 variables can explain 60 %–70 % of the global variance of SOC in the four layers, to which climatic variables and edaphic properties each contribute ∼35 % except in the top 20 cm soil. In the top 0–20 cm soil, climate contributes much more than soil properties (43 % vs. 31 %), while climate and soil properties show the similar importance in the 20–50, 50–100 and 100–200 cm soil layers. However, the most important individual controls are consistently soil-related and include soil texture, hydraulic properties (e.g. field capacity) and pH. Overall, soil properties and climate are the two dominant controls. Apparent carbon inputs represented by net primary production, biome type and agricultural cultivation are secondary, and their relative contributions were ∼10 % in all soil depths. This dominant effect of individual soil properties challenges the current climate-driven framework of SOC dynamics and needs to be considered to reliably project SOC changes for effective carbon management and climate change mitigation.
Highlights
Soil organic carbon (SOC) represents the largest pool of terrestrial carbon (Le Quéré et al, 2016; Batjes, 2016) and plays a key role in combating climate change and ensuring soil productivity
The 19 climatic variables could be represented by four principal components (PCs, i.e. Climate1–4, which were selected by Kaiser’s criterion) which could explain 88 % of their variance (Fig. 2; only the first two PCs were shown); and 72 % of the variance in nine soil properties could be explained by three PCs (i.e. Soil1–3, Fig. 2)
We argue that soil physicochemical characteristics define the boundary conditions for the climatic and biotic factors
Summary
Soil organic carbon (SOC) represents the largest pool of terrestrial carbon (Le Quéré et al, 2016; Batjes, 2016) and plays a key role in combating climate change and ensuring soil productivity. To better manage land for maintaining SOC levels or enhancing carbon sequestration, it is vital to elucidate controlling factors of SOC stabilization and stock. As an important soil property, it is reasonable to expect that SOC might be integrally influenced by five predominant factors controlling soil development and formation – namely, climate, organisms, topography, parent materials and time (Jenny, 1941). SOC can be physically protected from decomposition via occlusion within soil aggregates and adsorption onto minerals (Six et al, 2000), which create physical barriers preventing microorganisms from decomposing carbon sources (Doetterl et al, 2015; Schimel and Schaeffer, 2012) regardless of climate conditions, but how this protection influences global SOC stocks is unclear. The soil physicochemical environment controls the supply of water, nutrients, oxygen and other resources, which
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
