Soil Hydrological Characteristics And Anti-erodibility In Different Successional Stages Of Multi-remediation Mode On Grain-for-green Slopes In The Water-wind Erosion Crisscross Region

The ecological problem of the Water-Wind Erosion Crisscross Region is serious,and the trouble of soil erosion has been very valued by the country.Soil hydrological characteristics and anti-erodibility studies play an important role in analyzing the remedial effects under different remediation modes in this area.This study took Liudaogou watershed in Shenmu County which is located in the Water-Wind Erosion Crisscross Region as the research object,and the natural restoration community of grain-for-green slopes?returning 5-year,15-year,25-year and 50-year natural grassland and returning 25-year and 40-year secondary natural grassland?and artificial community?Medicago sativa artificial grassland,Caragana korshinkii artificial shrub forestland and Pinus tabulaeformis artificial arbor forestland?were selected as experimental groups.The cultivated land was selected as a control on the basis of field investigation.This study measured soil moisture and aggregates,and systematically studied soil moisture distribution characteristics and soil structure under different remediation modes,and combined with soil hydrostatic disintegration test to comprehensively analyze soil anti-erodibility.The results can provide a scientific basis for the prevention and control of soil erosion and the effective construction of ecological environment in the Water-Wind Erosion Crisscross Region.The main results are as follows:?1?Cropland with natural abandoned,planted Medicago sativa,Caragana korshinskii and Pinus tabulaeformis respectively could increase soil porosity and water holding capacity during the 25-year period of grain-for-green.And the water retention capacity,penetrating ability and the function of vegetation conservation water source had been enhanced,the cultivation of Medicago sativa and Pinus tabulaeformis had the best effect among them.However,soil particles were hit by gravity and raindrops as long-term,they gradually squeezed down.When the water infiltrated,it carried the dispersed soil clay and filled the small pores of the soil,and the continuous would increase in soil bulk density with the age of grain-for-green cropland,which eventually inhibited soil porosity and water holding capacity of natural grassland and secondary natural grassland.The cropland with natural abandoned and the growth process of Medicago sativa and Caragana korshinskii made the dried layer of soil develop continuously.Among them,Medicago sativa and Caragana korshinskii heavily consumed the deep soil moisture,and the dried layer were extremely deep and thick.But with the degradation of Medicago sativa,the soil water condition gradually optimized.Because the function of water source of Pinus tabulaeformis was stronger,the deep soil moisture was supplemented and there was no dried layer after 25-year of grain-for-green cropland,so it was beneficial to soil moisture recovery.?2?In the early stage of naturally abandoned,soil clay content decreased due to surface exposure.With the succession of the community,the soil clay content gradually increased,the soil aggregates continued to polymerize,the soil mechanical-stable and water-stable increased year by year.The planted of Medicago sativa could increase soil clay content and enhance soil mechanical-stable,but the soil water-stable and anti-erodibility of water property were weakened.With the secondary succession process of Medicago sativa degradation,the vegetation and litter cover were reduced that resulted the enhance of rain splash and runoff scouring,so that the soil clay content reduced,but the soil water-stable aggregates structure continuously improved,the soil water-stable and anti-erodibility of water improved.Planted Caragana korshinskii and Pinus tabulaeformis could enhance soil mechanical-stable as well as the soil water-stable and anti-erodibility of water at 0-10 cm soil layer,but it weakened the two properties of 10-20 cm soil layer.The content of soil clay was higher on Pinus tabulaeformis,which was related to the litter.It is beneficial to the preservation and remediation of clay.?3?The soil anti-disintegration ability gradually increased during the vegetation restoration process,and the soil anti-disintegration ability of the naturally abandoned and the planting Medicago sativa were stable after 25-year of grain-for-green.This study compared with the four vegetation restoration models of returning cropland for 25-year,and the land of planting Pinus tabulaeformis had the weakest soil anti-disintegration ability,and the other three were basically same.This was due to the fact that the soil anti-disintegration ability improved depending on the reinforcement of herbaceous vegetation roots to soil under the premise of good water-stable aggregate structure.The comprehensive anti-erodibility was obtained by principal component analysis method with selecting the valuable soil anti-erodibility index in study.The comprehensive soil anti-erodibility of each sample was SNG₂>NG₄>SNG₁>AT>NG₃>AS>AG>NG₂>NG₁>CK,the comprehensive anti-erodibility of secondary natural grassland in the same year was better than natural grassland,which was related to the excellent nutrient conditions of Medicago sativa grassland.?4?According to the results of this study,the Water-Wind Erosion Crisscross Region should adopt the remediation modes of artificial planting Medicago sativa grassland then let it natural restoration to secondary natural grassland or planting Pinus tabulaeformis,both of which has the best effect on soil water conditions recovery,soil structure improvement and anti-erodibility enhancement.