Soil organic carbon dynamics jointly controlled by climate, carbon inputs, soil properties and soil carbon fractions

• Published in: Global change biology 2017-10, Vol.23 (10), p.4430-4439
• Main Authors: Luo, Zhongkui, Feng, Wenting, Luo, Yiqi, Baldock, Jeff, Wang, Enli
• Format: Article
• Language: English
• Subjects: Agricultural ecosystems; Agricultural practices; agricultural soil; Annual precipitation; Australia; Bulk density; Capacity; Carbon; carbon sequestration; Cation exchange; Cation exchanging; Cations; Clay; Climate; Climate effects; Composition; Crop rotation; Dynamics; Exchange capacity; measured carbon fractions; Organic carbon; Organic soils; Pasture; physical protection; Pools; Precipitation; Properties; Rotation; Soil; Soil - chemistry; Soil dynamics; soil geochemistry; Soil investigations; soil organic carbon; Soil properties; Soil temperature; Stock assessment; Temperature; Tillage
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.13767

Soil organic carbon (SOC) dynamics are regulated by the complex interplay of climatic, edaphic and biotic conditions. However, the interrelation of SOC and these drivers and their potential connection networks are rarely assessed quantitatively. Using observations of SOC dynamics with detailed soil properties from 90 field trials at 28 sites under different agroecosystems across the Australian cropping regions, we investigated the direct and indirect effects of climate, soil properties, carbon (C) inputs and soil C pools (a total of 17 variables) on SOC change rate (rC, Mg C ha−1 yr−1). Among these variables, we found that the most influential variables on rC were the average C input amount and annual precipitation, and the total SOC stock at the beginning of the trials. Overall, C inputs (including C input amount and pasture frequency in the crop rotation system) accounted for 27% of the relative influence on rC, followed by climate 25% (including precipitation and temperature), soil C pools 24% (including pool size and composition) and soil properties (such as cation exchange capacity, clay content, bulk density) 24%. Path analysis identified a network of intercorrelations of climate, soil properties, C inputs and soil C pools in determining rC. The direct correlation of rC with climate was significantly weakened if removing the effects of soil properties and C pools, and vice versa. These results reveal the relative importance of climate, soil properties, C inputs and C pools and their complex interconnections in regulating SOC dynamics. Ignorance of the impact of changes in soil properties, C pool composition and C input (quantity and quality) on SOC dynamics is likely one of the main sources of uncertainty in SOC predictions from the process‐based SOC models. We quantitatively assessed the interconnections of a series of climatic, edaphic and biotic factors in controlling soil organic carbon (SOC) dynamics. We found that, overall, soil properties, soil C pools, climate and C inputs were almost equally important in terms of overall effect on SOC dynamics. However, if the effect of soil was controlled, the effect of climate was significantly weakened, and vice versa, while the effects of carbon input and soil carbon pool composition were significantly strengthened if climate and/or soil were controlled. These results force us to revise SOC predictions based on modelling and empirical approaches mainly considering climatic factors, and provide new insigh