Study On The Influence Of Crop Vertical Structure Difference On Rainfall Distribution Process

Soil and water loss caused by soil erosion has posed a serious threat to the development of human society and is one of the ecological and environmental problems of common concern in the world.Vegetation plays an important role in the occurrence and development of soil erosion,such as intercepting rainfall,regulating surface runoff,increasing rainfall infiltration and improving soil properties.The rainfall distribution process of vegetation canopy can reduce the kinetic energy of raindrops and reduce runoff,so as to effectively prevent soil erosion.The vertical structure of vegetation refers to the morphological structure and hierarchical structure in the vertical direction of vegetation,which is an important factor affecting soil erosion.Compared with natural vegetation,crops are greatly affected by man-made factors,the growth cycle is short,and the vertical structure changes significantly during the growth period.The vertical structure of different crops has obvious differences,which makes the relationship between crops and soil erosion complex.Therefore,it is of great significance for soil erosion control and environmental protection to explore the impact of different crop vertical structures on rainfall distribution.In this paper,two typical sloping farmland crops,corn and soybean,are taken as the research objects.Based on three-dimensional laser scanning and point cloud reconstruction technology,the vertical structure parameters of crops are extracted.The rainfall redistribution and raindrop kinetic energy reduction of crops are measured by indoor artificial rainfall simulation test,and the partial least square regression model of vertical structure and rainfall distribution process parameters of crops is constructed,Analyze the relationship between crop vertical structure and rainfall distribution process,reveal the impact of crop vertical structure differences on soil erosion,and provide theoretical basis and technical support for accurate prediction and prevention of soil erosion.The main conclusions of this paper are as follows:（1）Based on three-dimensional laser scanning and point cloud reconstruction technology,nine parameters,including plant height,crown diameter,crown length ratio,leaf inclination,centroid height/plant height,leaf area index,vegetation coverage,leaf length and leaf width,were extracted.The overall accuracy was greater than 85%,and the extraction effect was good.As the growth period goes on,the plant height,crown diameter,leaf area index,vegetation coverage,leaf length and leaf width of crops generally show an increasing trend,while the crown length ratio,leaf inclination and centroid height/plant height generally show a decreasing trend;Among them,the growth rate of leaf area index is large,and the change is the most significant during the growth period.The change range of centroid height/plant height and leaf inclination is small,and it is relatively stable during the growth period.（2）From the seedling stage to the mature stage,the reduction of raindrop kinetic energy,stem flow rate and canopy interception rate of crops generally showed an increasing trend,and the penetration rate of rain showed a decreasing trend.In the same lifetime,the change of rainfall intensity had no significant effect on the throughfall rate,stem flow rate and canopy interception rate.During the whole growth period,the average rain penetration rate of maize was 60.02%,the stem flow rate was 37.80%,and the canopy interception rate was 2.18%;The average rain penetration rate of soybean was 81.59%,the stem flow rate was 15.99%,and the canopy interception rate was 2.42%.Reproductive period,corn and soybean canopy on the average raindrop kinetic energy reductions were 197.49×8)^-2×?^-1 and 139.18×8)^-2×?^-1.（3）The effects of vertical structure of maize and soybean on rainfall distribution were significantly different,and the interception effect of maize canopy on rainfall was better than that of soybean.The overall change trend of the vertical structure parameters of maize and soybean is basically the same,and there are only significant differences in numerical values.The plant height,crown diameter,leaf length and leaf width of maize are larger than those of soybean,and the other vertical structure parameters are smaller than those of soybean.In the process of rainfall distribution,the penetration rate of corn is less than that of soybean,and the reduction of raindrop kinetic energy is greater than that of soybean.Under the same rainfall conditions,corn can intercept more rainfall and reduce more kinetic energy of raindrops.The results of partial least squares regression model showed that the most significant vertical structure parameters affecting the rainfall distribution process of maize and soybean were leaf area index and crown diameter,respectively.