Effect Of Sea-buckthorn On Soil Water Infiltration In Pisha Sandstone Area

The Pisha sandstone is mainly distributed in the northern part of the Loess Plateau.Affected by the arid climate and human activities,the ecological environment in this area is very fragile.Because of low permeability and easy runoff,the precipitation resources can not be used well,which brings great challenges to local vegetation restoration.Practice has proved that sea-buckthorn can grow well in this area,and other plants appeared under the degrade sea-buckthorn forest,so it can be seen that sea-buckthorn can improve the local soil habitat,which is of great significance for ecological restoration in this area.At present,the effect and mechanism of sea-buckthorn restoration process on soil properties and water infiltration process in this area are still unclear.Based on this,this study took sea-buckthorn woodland at different growth stages in Junge Banner,Inner Mongolia Autonomous Region as the research object,and bare land and grassland as the control.Double-ring infiltration meter and stained tracer method were used to study the soil water infiltration process and soil preferred flow characteristics,and explored the influence of sea-buckthorn growth process on soil structure and physical and chemical properties.The effects of the growth process of sea-buckthorn on soil water infiltration and preferential flow characteristics were revealed.The main conclusions are as follows:(1)Sea-buckthorn can effectively improve soil physical and chemical properties in the Pisha sandstone area,and the improvement effect varies with different growth stages.Adult sea-buckthorn forest can effectively improve soil water retention,porosity,root biomass,herbaceous biomass and litter accumulation,reduce soil bulk density and improve soil structure.Compared with the bare land,the saturated water content,capillary water capacity and field water capacity of the adult sea-buckthorn forest increased by 74.04%,85.14% and86.06%,and the soil bulk density decreased by 18.06%.The capillary porosity and total porosity increased by 52.56% and 43.82%,respectively.The content of large aggregates and average weight diameter of aggregates increased by 96.56% and 134.45%,respectively.The root biomass,herbaceous biomass and litter accumulation increased by 5.84 times,161.70%and 389.01%,respectively.Degraded sea buckthorn forest land can effectively increase noncapillary porosity,organic carbon content,total nitrogen content,root length density,root surface area density and root volume density,and reduce soil total phosphorus content.Compared with bare land,non-capillary porosity increased by 290.61%,organic carbon and total nitrogen contents increased by 91.33% and 134.45%,total phosphorus content decreased by 63.72%,root length density,root surface area density and root volume density increased by 95.05%,123.10% and 225.71%,respectively.(2)Vegetation restoration of sea buckthorn can promote the development of soil preferential flow.The main patterns of soil water movement in various lands were matrix flow(bare land),unstable flow(juvenile sea buckthorn forest land and grassland),funnel flow(adult sea buckthorn forest land)and macropore flow(degraded sea buckthorn forest land).With the increase of soil depth,the priority flow of sea buckthorn woodland gradually appeared,and the degraded sea buckthorn woodland began to appear in the surface layer(0-10 cm),followed by juvenile sea buckthorn woodland(10-20 cm layer)and adult sea buckthorn woodland(20-40 cm layer).Below 40 cm depth,the priority flow phenomenon of sea buckthorn woodland disappeared and water infiltration ended.Soil texture,nutrient content and vegetation roots were the main factors affecting soil preferential flow.The content of Clay and organic carbon could predicte 75.2% of the preferred flow intensity in 0-10 cm layer,the content of Clay and total phosphorus could predicte 63.5% of the preferred flow intensity in 10-20 cm layer,and the content of total phosphorus and root biomass could predicte 58.1% of the preferred flow intensity in 20-40 cm layer.(3)The vegetation restoration of sea buckthorn can improve the infiltration rate of soil water in the Pisha sandstone area.With the increase of the age of sea buckthorn forest,the infiltration rate of soil water first increased and then decreased,and the infiltration effect of soil water in the adult sea buckthorn forest land was the best.The Philip model fitted the soil water infiltration process well for bare land,adult and degraded sea buckthorn woodland,and the Kostiakov-Lewis model fitted the soil water infiltration process well for juvenile sea buckthorn woodland and grassland.The basic physical and chemical properties of soil at 0-20 cm layer and vegetation roots were the main factors affecting soil water infiltration performance.The direct influencing factors were soil pores,the indirect influencing factors were soil structure and soil nutrients,and the driving factors were soil texture and vegetation roots.The effect of basic physical and chemical properties of soil and vegetation roots on soil water infiltration was weakened below 20 cm layer.Field water capacity(0-10 cm layer),root surface area density(20-40 cm layer)and root biomass(10-20 cm layer)had the best prediction effect on initial,stable and average infiltration rate.This study shows that sea-buckthorn can effectively improve soil physical and chemical properties,promote soil water infiltration,and improve soil habitat in the Pisha sandstone area,especially in the adult aged sea-buckthorn forest.The study results can provide scientific basis for vegetation construction and soil erosion control in the Pisha sandstone area.