| After implementing a series of ecological restoration projects such as returning farmland to forest(grassland)and warping dam in the Loess Plateau region,the conditions of the underlying slope surface have changed and a new hydrological cycle model has appeared.Therefore,this paper selected different vegetation types as the research object in Fangta watershed of Ansai District,Shaanxi Province.Through to the vegetation of the slope and soil investigation and sampling,and the runoff and sediment yield in the area rainfall,soil moisture,monitoring and analysis of different farmland slope is studied in the process of vegetation succession of plant community and soil recovery characteristics,the characteristics of soil water and sediment yield and sediment yield on slopes restored by vegetation returning from farmland under different rainfall conditions were explored,and the responses of sediment yield and sediment yield to rainfall and vegetation restoration characteristics were explored,in order to provide reference for the regulation of slope water and soil resources and improvement of soil erosion model in this area.The main conclusions are as follows:(1)The family number,genus number and species number of plant species in herbaceous and shrub communities increased with the increase of retiring years.With the succession of vegetation,soil organic matter content in different vegetation restoration slopes showed an increasing trend,while the dry-screened aggregates showed a slight increasing trend,and soil mechanical stability was enhanced.Under the same rainfall condition,the response rate of soil water to rainfall and the amount of soil water infiltration of different vegetation types were in the order of A.lupus community > A.sphaerocephala +Stipa grandis community > A.suerocephala + Miscanthus community.(2)The runoff and sediment yield of each vegetation plot was significantly lower than that of the bare slope plot,and the runoff and sediment yield of robinia pseudoacacia forest plot were the least.Compared with bare slope,runoff and soil loss of different plant communities were reduced by 72.5-99.7% and 98.8-99.9% respectively.Under general erosive rainfall conditions,the benefit of vegetation coverage increase is higher than that of sediment reduction.However,under the condition of heavy rain erosive rainfall,the increase of vegetation coverage produced more runoff reduction benefits,but there was little difference in sediment reduction benefits.When the vegetation coverage was above 40%,the effect of vegetation type on sediment yield was not obvious.(3)The maximum rainfall intensity of 60 minutes,maximum rainfall intensity of 30 minutes,vegetation coverage,vegetation type and average weight diameter of dry screen aggregates in 0-10 cm soil layer had significant effects on slope runoff yield(P<0.01),which could explain 38.4% change of slope runoff yield.In general erosive rainfall,the maximum rainfall intensity of 60 minutes and maximum rainfall intensity of 30 minutes are the main factors affecting runoff yield,and the maximum rainfall intensity of 60 minutes is the most important factor affecting sediment yield.The maximum 30-minute rainfall intensity is the most important factor affecting runoff yield,and runoff depth is the most important factor affecting sediment yield. |
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