Abstract
Soil respiration that releases CO2 into the atmosphere roughly balances the net primary productivity and varies widely in space and time. However, predicting its spatial variability, particularly in intensively managed landscapes, is challenging due to a lack of understanding of the roles of soil organic carbon (SOC) redistribution resulting from accelerated soil erosion. Here we simulate the heterotrophic carbon loss (HCL)—defined as microbial decomposition of SOC—with soil transport, SOC surface redistribution, and biogeochemical transformation in an agricultural field. The results show that accelerated soil erosion extends the spatial variation of the HCL, and the mechanical-mixing due to tillage further accentuates the contrast. The peak values of HCL occur in areas where soil transport rates are relatively small. Moreover, HCL has a strong correlation with the SOC redistribution rate rather than the soil transport rate. This work characterizes the roles of soil and SOC transport in restructuring the spatial variability of HCL at high spatio-temporal resolution.
Highlights
Soil is the largest reservoir of carbon in the terrestrial system, which contains an estimated 1,500– 2,400 Pg C (Friedlingstein et al, 2020)
Soil erosion/deposition, and bioturbation by soil fauna, the soil organic carbon (SOC) mass conservation in a soil column is summarized as Yan et al (2019): Surface processes:
Comparing the relationship between the soil transport rate and annual accumulated heterotrophic carbon loss (HCL) ( Soil Depth) at each 2-D grid box in the study domain, we find that the sites with fast soil deposition rate does not necessarily correspond to high HCL (Figure 3A1), even though depositional sites show higher HCL than erosional sites by average
Summary
Soil is the largest reservoir of carbon in the terrestrial system, which contains an estimated 1,500– 2,400 Pg C (Friedlingstein et al, 2020). The amount of CO2 released through soil respiration contributes to about 120 Pg C/yr to the atmosphere, which roughly balances the net primary productivity but much higher than what fossil fuel burning contributes to the atmosphere (≈9 Pg C/yr) (Boden et al, 2010; Friedlingstein et al, 2020). Understanding the spatio-temporal dynamics of soil respiration rate is vital for quantifying terrestrial carbon cycling and developing future climate change mitigation strategies. Soil respiration can be characterized as (1) root and litter respiration (autotrophic carbon loss), and (2) microbial metabolic decomposition of organic carbon (heterotrophic carbon loss). The heterotrophic carbon loss (HCL) is sustained by organic matter inputs to the soil from aboveground litterfall, humic substances, and root detritus. Many studies have investigated factors that directly influence the HCL such as soil type, land cover, and climate
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