Abstract
BackgroundAlthough soil erosion plays a key role in the carbon cycle, a holistic and mechanistic understanding of the soil erosion process within the cycle is still lacking. The aim of this study was therefore to improve our mechanistic understanding of soil organic carbon (SOC) and soil respiration dynamics through an experiment conducted in an eroding black soil farmland landscape in Northeast China.ResultsThe depositional profiles store 5.9 times more SOC than the eroding profiles and 3.3 times more SOC than the non-eroding profiles. A linear correlation between the SOC and 137Cs (Caesium-137) was observed in our study, suggesting that the SOC decreased with increased soil erosion. Furthermore, the fractions of intermediate C and the microaggregate C were lowest at the eroding position and highest at the depositional position. In the depositional topsoil, the input of labile materials plays a promotional role in soil respiration. Conversely, in the subsoil (i.e., below 10 cm), the potential mineralization rates were lowest at the depositional position—due to effective stabilization by physical protection within soil microaggregates. The field results of soil surface respiration also suggest that the depositional topsoil SOC is prone to be mineralized and that SOC at this depositional context is stabilized at subsoil depth. In addition, the high water contents at the depositional position can limit the decomposition rates and stabilize the SOC at the same time.ConclusionsThe findings from this study support that a majority of the SOC at footslope is stored within most of the soil profile (i.e., below 10 cm) and submitted to long-term stabilization, and meanwhile support that the depositional profile emits more CO2 than the summit due to its high amount and quality of SOC.
Highlights
As the largest terrestrial carbon pool, the soil carbon pool is approximately 3.3 times the size of the atmospheric pool and 4.5 times the size of the biotic pool (Lal 2004a)
We mainly focus on the soil organic carbon (SOC) stocks and soil respiration dynamics in this study
Soil erosion and soil organic content patterns Based on the 137Cs measurements, we quantitatively estimated that the soil erosion rates for A1, A2, and A3 were − 3.5 t ha−1 year−1, − 47.2 t ha−1 year−1, and − 56.1 t ha−1 year−1, respectively, and the soil deposition rate for A4 was approximately 56.9 t ha−1 year−1
Summary
As the largest terrestrial carbon pool, the soil carbon pool is approximately 3.3 times the size of the atmospheric pool and 4.5 times the size of the biotic pool (Lal 2004a). Soil erosion and the subsequent transport of sediments by rivers represent a key pathway for soil carbon lateral transfer at the land surface, which has a profound effect on the carbon budget of terrestrial ecosystems (Ludwig et al 1996; Li et al 2018; Wang et al 2019). Soil lateral redistribution processes induced by water and tillage erosion can often affect carbon cycle dynamics. A full mechanistic understanding of the effect of soil erosion and burial processes on vertical carbon dynamics (such as soil respiration, aboveground respiration, plant production, etc.) is still lacking (Kuhn et al 2012). The aim of this study was to improve our mechanistic understanding of soil organic carbon (SOC) and soil respiration dynamics through an experiment conducted in an eroding black soil farmland landscape in Northeast China
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