| Ensuring the security of soil and water resources is crucial for human societal development.Recently,soil erosion has become increasingly severe due to population growth and climate change.The Chinese Loess Plateau suffers from particularly high soil and water loss due to loose soil and concentrated rainfall.Vegetation measures are one of the main measures for local soil erosion control.In order to study the soil and water conservation effects of different slopes and vegetation in the hilly and gully area of the Chinese Loess Plateau,this study analyzed the soil and water conservation effects of different slope and vegetation types in Fengjiagou soil and water conservation monitoring station,a hilly and gully region of the Loess Plateau.Based on the artificial runoff field test method,the natural rainfall in 2014-2016 was continuously observed.For 9 slopes of 15°,5 vegetation measures(arbor,shrub,abandonment,pasture,and arable land)were adopted respectively The characteristics of erosive rainfall in the hilly and gully areas of the Loess Plateau were analyzed.The K-means cluster analysis was used to classify 29 erosive rainfall and explore the effect of different vegetation measures on Soil and water conservation under different rainfall types.Six typical erosive rainfalls from 2009 to 2011 were selected to analyze the runoff and sediment yield characteristics of different plant measures(crops,artificial grass planting,abandoned land)under three slope grades(10°,15°,20°)..The following conclusions are drawn:(1)Rainfall in the hilly and gully areas of the Chinese Loess Plateau predominantly occurred from April to September,whereas erosive rainfall was concentrated in July and August.As a result,the frequency of soil erosion was highest in July.(2)The maximum 30-min rainfall intensity and rainfall depth exhibited a significant and extremely significant correlation with runoff and sediment yield,respectively,for the five typical vegetation types;however,there was no obvious correlation between rainfall duration and runoff and sediment yield of different vegetation.Based on K-means clustering analysis,the observed erosive rainfall events were divided into five rain regimes: I rain regime(large rainfall depth,moderate rainfall intensity),II rain regime(small rainfall depth,light rainfall intensity),III rain regime(small rainfall depth,moderate rainfall intensity),IV rain regime(medium rainfall depth,light rainfall intensity),V rain regime(medium rainfall depth,heavy rainfall intensity).Among them,regime II accounted for the largest proportion of rainfall in the study area.Regime V accounted for the smallest proportion but produced the largest amount of soil erosion.(3)Compared with bare land,different vegetation measures exhibited different soil and water conservation effects in different erosive rainfall.Reduction of soil and water loss under different rain conditions decreased in the following order: arbor measures > shrub measures > abandonment measures > artificial pasture and arable measures.The effect of soil reduction in arbor measures reached 100% under regime III,whereas the sediment reduction efficiency of shrub measures was higher than that of arbor measures in regime V,which had the largest rainfall intensity.The soil and water conservation efficiency of abandonment measures were related to the growth year and the efficiency of sediment loss reduction was better than that of runoff reduction;the most effective runoff and sediment reduction occurred in regime III.The soil and water conservation effects of arable and artificial pasture measures were similar and the worst among all vegetation measures.Soil and water conservation is also related to climate and soil characteristics,which should be considered comprehensively when selecting appropriate vegetation measures.(4)The characteristics of runoff and sediment yield differed substantially for different crops.Under various rainfall conditions,the runoff yield and soil loss were highest in corn plots but lowest in sweet potato and millet plots.Minimal differences were observed in runoff yield and soil loss between potato and soybean plots.Therefore,sweet potato was deemed more suitable for soil and water conservation in hilly and gully areas of the Losses Plateau.Conversely,as the yield of corn is relatively large,it is not recommended for the prevention and control of soil and water loss.(5)The runoff sediment yield decreased with decreasing slope angle under the same vegetation conditions.When the slope was greater than 10°,the crops were vulnerable to soil erosion;therefore,slopes greater than 10° are not recommended for planting crops as soil and water conservation measures. |
