Regulation Effect Of Slope Management Measures On The Loss Process Of Soil Aggregates And Organic Carbon

The Loess Plateau is among the Chinese regions that are most affected by the hydraulic erosion phenomena.Hydraulic erosion adversely affects soil aggregation and the loss of organic carbon,which result in soil degradation and productivity loss.Biotic systems utilize the organic carbon lost from the soil,which exacerbates the greenhouse effect in the atmosphere.Soil erosion on the Loess Plateau has been mitigated to some extent through the establishment of protective measures such as soil and water conservation measures and the transformation of farms to forests and grasslands.Nevertheless,it is crucial to undertake a comprehensive study on the influence of slope measures on soil aggregation and the loss of organic carbon due to hydraulic erosion.The scope of this study is centered on the slope-gully system,a typical erosion unit in China’s Loess Plateau.Seven slope measure arrangements were created through indoor simulated rainfall tests.The control group features bare slopes,while the six other groups involve vegetation being planted on the upper(pattern A),middle(pattern B),and lower(pattern C)parts of the slope,the placement of terraces on the middle of the slope(pattern D),and vegetation being planted on the upper or lower side of the terraces(patterns E and F).We analyzed the characteristics of runoff and sediment yield,soil aggregation,and organic carbon loss under different slope measure setups to reveal the relationship between soil aggregation and organic carbon migration throughout the process of hydraulic erosion.In view of the results,we propose the ideal approach for checking erosion and organic carbon loss in slope-gully systems,which provides a solid theoretical and scientific foundation for the optimization of soil and water conservation interventions in the Loess Plateau region.The most significant conclusions drawn from the research are as follows:(1)The effectiveness of various slope measures in reducing runoff and sediment ranges from 7.00%to 64.67%and from 5.01%to 38.99%.Among single vegetation measures,pattern C is the most effective in reducing both water and sediment.Compared to vegetation measures,terraces located at the same position on the slope are more effective in controlling water and sediment reduction.The combination of the two measures is more effective than a sole measure pattern;pattern F demonstrates the highest capability for reducing water and sediment loss.(2)The loss of soil aggregates under different slope measures consisted mainly of particles with sizes<0.25 mm,which accounted for 65.19%to 90.31%of the total loss.The effect of slope measures on the loss of aggregates with particle sizes>0.25 mm was more significant,and the loss was significantly reduced compared to slopes without measures(P<0.05).Pattern F was the most effective in regulating aggregates of>0.25 mm particle sizes,reducing the loss by 81.96%.Across various slope measure patterns,both the Mean Weight Diameter(MWD)and Geometric Mean Diameter(GMD)of the lost aggregates significantly decreased compared to bare slopes,while the Fractal Dimension(D)significantly increased(P<0.05).The enrichment rate of the aggregates>0.25 mm showed a decreasing trend,whereas that of the aggregates<0.25 mm showed an increasing trend.(3)Various slope measures can regulate the total loss of soil organic carbon.Under single vegetation measure patterns,Pattern C is most effective in reducing organic carbon loss by 21.15%.The terrace measure pattern is better than the vegetation pattern,reducing organic carbon loss by 21.23%.Combined measure patterns are more efficient than single measure patterns,and Pattern F is the most effective in reducing loss,with 29.39%improvement.Loss of organic carbon from aggregates is predominantly from aggregates with particle sizes<0.25 mm,accounting for 61.93%to 89.01%of the total loss,and inversely proportional to the aggregate size.Across different slope measure patterns,organic carbon content is higher for each aggregate size than for the original experimental soil,and the organic carbon enrichment rate increases as the slope measure pattern goes from a bare slope to Pattern F.Among aggregates,those with particle sizes<0.25 mm have the fastest and highest organic carbon enrichment rate.(4)Different slope measure patterns can be fitted with a linear regression equationy=Ax+B(R2>0.97)for the loss of organic carbon with runoff volume,and a power function y=AxB(R2>0.99)for the loss of organic carbon with sediment yield.Changes in the enrichment rate of each aggregate size affect organic carbon enrichment rates differently.An increase in the enrichment rate of aggregates>1 mm,1-0.5 mm,and 0.5-0.25 mm can lead to a decrease in aggregate organic carbon enrichment rate,while the enrichment rate of aggregates<0.25 mm is positively correlated with organic carbon enrichment rate.