| In loess hilly gully region of central Gansu is one of the most serious water erosion areas in China.One of the most effective soil and water conservation measures in the region is the artificial cultivation of pasture and the prohibition of natural vegetation.Therefore,study on the Loess Hilly Region of central Gansu Grassland in response to different types of erosive rainfall,analyzed the change of soil moisture in the growing season of vegetation,in order to provide theoretical basis and construction of ecological environment restoration of vegetation in the region.Based on measurements in 2007-2015 from runoff plots located in Anjiagou catchment,the Dingxi city.We analyzed the effects of rainfall characteristics and slope factors on soil erosion,and the response of artificial grassland and natural grassland with slope of 20°to erosive rainfall was discussed.The soil moisture of artificial grassland,natural grassland and farmland was measured by drying method,and comparison of farmland,the characteristics of the changes of soil moisture in different land use types and soil water balance state in profile in growing season were analyzed.The results showed that:(1)In the study area,the erosive rainfall mainly fell from May to September,the erosive rainfall was larger in August,and the amount of erosion caused by it is more than 70% of the annual erosion.Slope erosion was significantly correlated with PI,PI10,PI30,and the correlation with PI10 was the best,single factor was the best correlation with the maximum I10,slope runoff was significantly correlated with P.(2)The erosion amount of the two kinds of grassland increased with the increase of slope,but runoff is different,with the increase of slope,the runoff of artificial grassland increased,while the natural grassland slope,runoff in 5°~10° interval decreased,increased more than 10°.The amount of erosion of artificial grassland is greater than that of natural grassland,and with the increase of slope,the gap between them is also increasing.(3)From rainfall,the influence of rainfall greater than 25 mm(heavy rain and rainstorm)on runoff and erosion is more obvious with the increase of slope.From rain intensity,when rainfall of low rain intensity(less than 10 mm·h-1),the amount of soil erosion on the slope surface increases slightly with the increase of slope.when rainfall of moderate and high rain intensity(greater than 10 mm·h-1),the amount of soil erosion increased significantly with the increase of slope,especially in the case of high rain intensity rainfall,when the slope was greater than 15°,the increase rate of erosion was the fastest.(4)In the 20°grassland slope,the rainstorm caused by the heavy rain is the largest,accounting for about 11% of the annual erosion amount,the amount of erosion caused by moderate rain and heavy rain accounts for about 86% of it.The erosive rainfall mainly in moderate rain and heavy rain,while the moderate and high rain intensity is the main driving force of grassland slope erosion,erosion caused by grassland accounted for about 91% of the total erosion,the relationship between amount of soil erosion and PI10?PI30 was better expressed by power function.The rainfall with erosivity of 50~100 MJ·mm·hm-2·h-1 was most frequently,but rainfall with high erosivity of than 300 MJ·mm·hm-2·h-1 caused the largest soil erosion,the erosion amount by the erosivity grassland accounted for about 33% of the total erosion,the rainfall with high erosivity has the greatest influence on the soil and water loss on the grassland slope.(5)At 20°slope,the rainfall amount standards of erosive rainfall in artificial grassland(coverage of 75%~82%)and natural grassland(coverage of more than 80%)were 11.3 mm and 11.9 mm,respectively;and the maximum I10 were 10.4 mm·h-1 and 11.7 mm·h-1,respectively,should be the maximum I10 better.The natural grassland has better effect of soil and water conservation than artificial grassland.(6)The different land uses had extremely affect on the soil moisture(P<0.01),the average soil moisture was: natural grassland(10.09%)> farmland(8.23%)> artificial grassland(8.16%).With soil depth,the variation coefficient of soil moisture content was reduced,and the influence of land use types on the water content of soil profile increased.The water content of soil profile changes in seasonal differences,the total water content in September was the largest,and the lowest in July,but the seasonal variation of soil moisture in natural grassland was not obvious in artificial grassland.With the increase of soil depth,the influence of seasonal variation on soil moisture was reduced.(7)In normal flow year,the soil water storage capacity in the period of vegetation growth season was less than that in the beginning of the season,after the rainy season,the soil water storage in the end of the season was greater than that in the early summer.The soil water consumption of artificial grassland was the largest,the soil water Supplement of natural grassland was the largest.Different land use types,the surplus-deficit status of soil water in soil profile has different rules,0-20 cm soil surplus is larger,natural grassland in only 40-60 cm has a deficit,and less deficit(-1.05 mm),artificial grassland in 20-60 cm soil layer has a deficit(-1.53 mm),in the 0-100 cm soil no deficit of farmland,but the soil water storage is small changes under the 40 cm layer. |
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