| In this study,four runoff plots,including bare slope,natural shrub and grass,Robinia pseudoacacia forest land and larch forest land,were used to study the changes of soil physical properties such as runoff and sediment yield process,soil moisture content,bulk density,porosity,aggregate and infiltration rate under the condition of secondary rainfall,so as to reveal the differences between different measures.Principal component analysis was used to evaluate the benefits of soil and water conservation of different measures.The results show that there were 22 rainfall events in the study area from May to September2020,including 8 light rain,9 moderate rain and 5 heavy rain,respectively,mainly moderate rain and heavy rain,few light rain events,and no rainfall events such as rainstorm and heavy rainstorm.The cumulative runoff with different soil and water conservation measures was1588.7,1197.81,1091.94 and 1045.63 L,respectively,and there was a significant positive correlation between runoff and rainfall,showing a very significant power function relationship.The cumulative sediment with different soil and water conservation measures was 144178.40,52046.07,39126.40 and 39989.84 g,respectively,and there was a very significant positive correlation between sediment yield and runoff,showing a significant power function relationship.The benefits of reducing flow with different soil and water conservation measures was24.61%-31.27%,and which of the reducing sediment was 63.90%-72.86%.The soil moisture content,bulk density and porosity with different soil and water conservation measures showed weak variability or medium variability.Soil aggregates was mainly >5 mm and 5-2 mm,and the content of aggregates with particle size of 0.5-0.25 mm was the lowest.The soil aggregates MWD and GMD with different soil and water conservation measures was 3.81-4.48 mm and2.51-3.43 mm.The stability of soil aggregates with different measures was Robinia pseudoacacia forest land > larch forest land > natural shrub and grass.The stable infiltration rates of each soil layer were 4.12-14.07,3.75-12.22 and 1.82-6.42 mm/min,which showed that Robinia pseudoacacia forest land > larch forest land > natural shrub and grass > bare slope.The general empirical model could better reflect the soil process under different soil and water conservation measures.Soil infiltration index was negatively correlated with soil bulk density and fractal dimension,and positively correlated with non capillary porosity,soil aggregate MWD and GMD.Through the principal component analysis of different soil and water conservation measures,the comprehensive score results showed that the soil and water conservation benefits of different measures were Robinia pseudoacacia forest land > larch forest land > natural shrub and grass > bare slope.Therefore,Robinia pseudoacacia forest land should be the main arrangement of soil and water conservation measures in the later stage. |
