Relationship between the slope microtopography and the spatial redistribution pattern of soil organic carbon under water erosion

Abstract

Soil erosion affects the dynamics of soil organic carbon (SOC) by redistributing SOC within the slope. The spatial redistribution of SOC was closely related to the slope of microtopography erosion. Although the mechanism of this process is poorly understood, it has the potential to influence the C balance of terrestrial ecosystems. This research aimed to study the relationship between the slope microtopography and the spatial redistribution pattern of SOC and to explain the spatial variation in SOC via water erosion. An observation was conducted on the runoff plot to quantify the change in the SOC content (0 to 1 cm depth) based on the 40 soil sample sites before and after erosion. A microtopographical digital elevation model was built by using a three-dimensional laser scanner, which was used for the automated measurement of point-by-point elevation on the slope surface before and after rainfall events. A generalized additive model and a geostatistical approach were combined to explain the relationship between the slope microtopography and the loss of SOC. Results showed that the slope microtopography significantly changed after erosion, and all the microtopographic indices in post-erosion were higher than those in pre-erosion. The SOC content decreased after erosion, and the spatial redistribution of SOC was closely related to the intensity of erosion. The spatial variability of SOC was reduced by water erosion. Moreover, the relief amplitude was the key factor that affected the spatial distribution of SOC pre- and post-erosion. The relief amplitude and net loss volumes significantly influenced the change in SOC.