模拟侵蚀对元江流域黄红壤土壤微生物和土壤有机碳的影响OA

Microorganisms are key drivers of the carbon cycle,and soil erosion is a major force that causes carbon loss.Investigating the mechanisms of soil erosion on soil microorganisms and soil organic carbon(SOC)is of great significance for understanding the coupling mechanisms of erosion,microbial communities,and carbon cycling.We conducted a simulated erosion experiment using the"cutting-and-filling"method from 2012 in a typical mountain area.A completely randomized design with five soil erosion thicknesses(5,10,20,30,and 40 cm)and a control(0 cm)was employed.Each treatment was performed in triplicate.Using phospholipid fatty acid(PLFA)and structural equation modeling(SEM)analysis,we found that 1)SOC and dissolved organic carbon(DOC)decreased in a quadratic pattern with the intensification of erosion,and there was a nonlinear relationship.The total PLFAs,fungal,bacterial(Gram-positive[G+],Gram-negative[G-]),actinomycete,and arbuscular mycorrhizal fungal(AMF)abundance significantly decreased with increasing erosion(p<0.05),whereas fungal/bacterial ratios and G+/G-significantly increased(p<0.05).2)Multi-response permutation procedure(MRPP)analysis confirmed significant differences in soil microbial communities under varying erosion intensity(δ=0.189,p=0.001),demonstrating that erosion intensity directly regulates microbial composition.3)SEM revealed that erosion directly explained 89.0%of SOC loss,while the decline in DOC was jointly driven by the direct effect of erosion(69.1%)and microbial mediation(53.6%),with reduced bacterial and G-gram positive GPLFAs serving as key indirect pathways.These findings indicate that SOC loss primarily results from erosion-induced reduction in soil mass,whereas DOC depletion is mainly mediated by the reduction in microbial PLFA content caused by soil erosion.This study provides a theoretical basis for soil erosion control and carbon management in southwestern China.