片蚀过程中[土娄]土团聚体活性有机碳流失特征及其量估算

Characteristics and Estimation of Lou Soil Aggregate-associated Active Organic Carbon Loss During Sheet Erosion

[目的]揭示土壤团聚体破碎、迁移对活性有机碳流失的影响,建立活性有机碳流失量估算方程,为评估水蚀作用下土壤有机碳流失与矿化的定量关系提供理论支撑。[方法]以黄土高原典型[土娄]土为研究对象,设计3种降雨强度(60mm/h,90mm/h,120mm/h)和3个坡度(5°,10°,15°),采用人工模拟降雨技术,通过建立经验方程,对活性有机碳流失量进行估算。[结果]相较雨强,坡度对土壤轻组有机碳(light fraction of soil organic carbon,LFoc)流失的影响更明显,片蚀与溅蚀泥沙LFoc含量均随坡度的增大先减小后增大,而雨强对片蚀泥沙LFoc含量无显著影响(p<0.05);溅蚀泥沙LFoc含量明显低于片蚀,且溅蚀泥沙LFoc未发生明显富集,片蚀泥沙中LFoc发生明显富集;对比不同粒级团聚体LFoc含量发现,<0.05mm黏粉粒、0.05~0.25mm团聚体中LFoc更易于发生富集,而0.25~2mm团聚体LFoc只在小雨强和小坡度条件下发生富集;由于<0.02mm粒级团聚体迁移为LFoc流失的主导因素,基于<0.02mm粒级团聚体迁移量相关指标,建立了拟合方程,对LFoc流失量进行了估算,拟合效果较好(R2=0.727)。[结论]水蚀过程中径流优先输移活性有机碳是造成有机碳大量矿化的原因,未来可以通过团聚体迁移量较好估算活性有机碳流失量。

[Objective]The aim of this study is to explore the response of soil active organic carbon loss to aggregate breakdown and transport,estimate the loss amount of active organic carbon by establishing empirical equations,and provide theoretical support for evaluating the quantitative relationship between soil organic carbon loss and carbon mineralization under water erosion.[Methods]This study took typical Lou soil in the Loess Plateau to conduct artificial simulated rainfall experiments with three rainfall intensities(60 mm/h,90 mm/h,and 120 mm/h)and three slopes(5°,10°,and 15°),and the loss amount of active organic carbon was estimated by establishing empirical equations.[Results]Slope gradient had the more important effect on light fraction of soil organic carbon(LFoc)loss than rainfall intensity.Both LFoc concentrations of sheet erosion and splash erosion sediments decreased first and then increased with the increase of slope gradient.Furthermore,rainfall intensity had no significant effect on the LFoc concentration of sheet erosion sediment(p<0.05).The LFoc concentration of splash erosion sediments was obviously lower than that of sheet erosion sediments.Meanwhile,the LFocs were obviously enriched in sheet erosion sediment while those in splash erosion sediments were not obviously enriched.Compared the LFoc concentrations of aggregates with different particle sizes,the results revealed that the LFoc of<0.05 mm clay and silt particles and 0.05~0.25 mm aggregates were more likely to be enriched,while the LFoc of 0.25~2 mm aggregates was enriched only under light rainfall intensities and gentle slopes.As the transport of<0.02 mm aggregates had great correlation with LFoc loss,such a loss was well estimated by the transport amount of<0.02 mm aggregates(R^(2)=0.727).[Conclusion]Runoff preferentially transports active organic carbon during water erosion,which is the reason for the large amount of mineralization of organic carbon.The loss and mineralization of active organic carbon can be well estimated by the amount of the transported aggregates in the future.