Soil Erosion Of Artificial Shrub Ecosystem In Dongluhe River Basin

In arid and semi-arid areas,the shrub ecosystem shows sparse patch structure in spatial structure.Compared with grassland,it is more likely to lead to the convergence of slope flow,which makes the micro landform change to the direction conducive to the development of erosion,and thus may strengthen runoff erosion.At present,relevant researches mainly focus on the degradation of grassland ecosystem caused by the natural invasion of shrub toward grassland,or the impact of the morphological characteristics and soil properties of shrub ecosystem microtopography under different geographical conditions,but few studies combine the two for comprehensive analysis.The Donglu River Basin is located in the ecotone between agriculture and animal husbandry in China,and the grassland is a zonal ecosystem.In order to repair severe land degradation,desertification,and soil erosion,the region has undergone large-scale vegetation reconstruction projects such as the three-north shelterbelt project and the conversion of cropland to forest and grassland project since the 1970 s and 1980 s.In order to accelerate the speed of vegetation restoration,artificial shrub plantation has become one of the main measures for vegetation construction.However,the zonal vegetation in this area is grassland vegetation,which forms the phenomenon of artificial shrub introduced into grassland,which is different from the shrub ecosystem formed by natural invasion in the process of soil and water.Exploring the effect of soil erosion effects of artificial shrub vegetation on local slope erosion,on the one hand,it can promote the understanding of the soil and water processes of artificial shrub ecosystem on the basis of scientific understanding,on the other hand,it is also of great significance to the restoration and management of ecosystem.In view of this,in this study,the artificial shrub ecosystem in the Donglu River Basin was taken as the research object.From the three dimensions of shrub structure,soil properties and soil erosion,the slope surface was taken as the basic research unit,focusing on the spatial variation characteristics of the shrub ecosystem from the top to the bottom of the slope.In this study,the difference between soil properties and soil erosion was studied by using the method of shrub-grassland inlaid shrub slope and pure grassland slope to reveal the soil erosion characteristics of artificial shrub ecological system.The main results are as follows:(1)There was a significant difference in cover pattern between the shrub-grass mosaic slope and the pure grassland slope.The height of individual shrub and the number of branches gradually decreased from the top to the bottom of the slope,and remained relatively stable as a whole.The long axis and the short axis of the shrub showed significant positive correlation,and they grew together along the slope.Compared with the grassland slope,the bare patches on the shrub slope have smaller density and larger patch area,and the Flowlength index,which represents the connectivity between the "source"(bare land),is higher,indicating that the bare patches on the shrub slope have less quantity and larger shape per unit area.The number and shape of bare land patches on grassland slope are large and small in unit area,and the distance from source landscape to sink landscape is relatively small.(2)The soil physical and chemical properties of the grassland under the shrub and between the shrubs were different.The soil compaction and soil bulk density under the shrub were lower than the grasses between the shrubs,and the soil organic carbon was higher than the grasses between the shrubs.On the one hand,the "fat island effect" under the canopy of the shrubs makes the shrubs have richer nutrients,so it has higher porosity and permeability,and the soil quality is looser than that of the grassland between the shrubs.The shrub has the ability to intercept the runoff sediment resources on the slope.More sediment is collected under the shrub,so the surface soil is relatively loose.(3)There are differences in soil properties between shrub slopes and grass slopes.The soil compactness and soil sand content of shrub slopes are higher than grass slopes,and the soil clay and silt contents are lower than the grassland slope,soil bulk density and soil organic carbon showed different results in the two groups of comparisons.The soil bulk density of the slope of shrub 1 was higher than that of the grassland,and the soil organic carbon was smaller than that of the grassland.The slope 2 had the opposite result.On the shrub slope,the mosaic structure between the shrub and grassland allows the water flow between the shrubs to converge,and the erosion is strengthened.Because of the smaller particle size,the clay particles and powder particles are more easily carried away by wind or runoff than sand particles.The grazing activity has exacerbated the erosion of the grassland between the shrubs.The walking route of the sheep on the shrub slope is more concentrated than that of the grassland,which makes the soil more compact,the porosity is smaller,and the water permeability is poor.(4)The spatial variation of soil erosion between shrubland and grassland is obviously different.The volume of the accretion body under the shrubs quantifies the interception ability of the shrubs on the slope to a certain extent.The results show that the volume of the accumulator decreases from the top of the slope to the bottom of the slope,while the volume of surface erosion increases,and the surface of the slope.The erosion volume is higher than that of grass slopes.The interception function of the shrubs on the one hand increases the volume of the accumulations under the shrubs;on the other hand,the increase of the accumulations exacerbates the height difference between the shrubs and the grassland,and makes the runoff more concentrated scour the slope.The grassland has the same ability to intercept the runoff and sediment on the uphill slope,and the erosion intensity from the uphill water is relatively uniform,so the surface erosion intensity is relatively small compared with the shrub slope.The above results show that although the shrub-grass mosaic slope formed by artificially introduced shrubs will increase the soil organic carbon content as a whole,the formation of micro-topography leads to the formation of large bare patches and strong Erosion.In addition,the shrub-grass mosaic ecosystem makes the movement path of livestock more concentrated,which further strengthens the erosion between shrubs on the shrub slope.In view of this,artificially introduced shrubs for vegetation construction need to pay more attention to the design of the shrub ecosystem spatial structure to avoid further development of soil erosion.