Studies On Surface Soil Hydrologic-physical Properties Of Different Land Use Types In Nanyang Danjiangkou Reservoir Area

Due to the start of the midcourt line project of the south-to-north water transfer,Danjiangkoureservoir area becomes a focus area of our country.with the building of the midcourt line project of thesouth-to-north water transfer,Ecological environment problems of the reservoir area not only concern tothe water safety of the surrounding region and downstream areas people’s lives and agriculture and theindustry,but also has a big influence to the existing of the project’s successfulworking.therefore,developing the research of surface soil hydrological physical properties of differenttypes of land utilization has a vital significant to the instruction of reservoir area’s land utilization andvegetation construction.This paper has a sample field survey of typical and representative vegetation of Nanyangdanjiangkou reservoir area,such as high forest,shrub grassland,terrace and sloping farmland andgrassland,it has a research to the surface soil hydrological physical properties of different types of landutilization and reveals the diversities of the volume weight of surface soil,porosity,pondage,andinfiltration rate of different types of vegetations,it provides theory basis for the tree species selection ofsoil-water conservation and ecological restoration and the building of high efficient water conservationforest.The main conclusions are as follows:The volume weight of surface soil of five types of vegetations not exceeding1.35g/cm3, thevolume weight of surface soil of shrub grassland and high forest is less than others’,the range ability ofsloping farmland and terrace is larger, the volume weight of surface soil of grassland is less than others’as a whole.With the increasing of sea level elevation, in0to10cm depth of soil, soil water storage of highforest,terrace and sloping farmland showed a rising trend,the porosity and storage of the shrub grasslandsoil showed a declining trend;while the volume weight of soil and noncapillary porosity of the10to20cm depth of different types of land utilization have no certain regularity; the total porosity and capillaryporosity of plough(terrace and sloping)and the10to20cm depth soil of high forest showed a decliningtrend with increasing of sea level elevation,the other types of land utilization showed a declining trendin the10to20cm depth soil except the high forest. The surface soil infiltration rate(The initialinfiltration rate and stability infiltration rate) of the five types of land utilization decreases with theincreasing of sea level elevation.In the same extent of sea level elevation and gradient,the surface soil total porosity and capillaryporosity of shrub grassland and high forest are comparatively large as a whole,in the meantime,theexperimental date shows the soil porosity of high forest is larger than shrub grassland;by contrast,thesloping farmland and terrace showed a unstable character,while the grassland had the minimum porosity.In the same extent of sea level elevation, the water storage and infiltration of the five types ofland utilization basic showed a trend similar to the soil porosity.With the increasing of gradient,the soil porosity of0to10cm soil depth of high forest and shrubgrassland showed a declining trend,in the10to20cm soil depth,the soil porosity of high increasedwith the increasing of gradient,while the shrub grassland decreased with the increasing of gradient;thesoil water storage of shrub grassland decreased with increasing of gradient,while the high forest had aunstable regularity.In the0to10cm soil depth of5to25degree gradient, the total water storage and absorbed waterstorage of high forest,shrub grassland and grassland are comparatively large,sloping farmland is thelowest,the water detention storage of high forest and terrace is comparatively large;in the10to20soildepth,the soil total water storage and absorbed water storage of high forest and sloping farmland arehigher than other types of land utilization,while the water detention storage of shrub grassland andgrassland is comparatively high;in the meantime,in the same gradient,in the0to10cm soil depth ofthe five kinds of land utilization,the Initial infiltration rate of sloping farmland next to shrubgrassland,the stability infiltration rate closes to terrace;the Initial infiltration rate of high forest is thelargest in the10to20cm soil depth,the stability infiltration rate closes to terrace,it is superior to theother kinds of land utilization;whether in the0to10cm soil depth or in the10to20cm soil depth,theinfiltration rate of grassland are the minimum and far less than the other kinds of land utilization.in theextent of30to60degree gradient,the every index of high forest soil water storage is higher than shrubgrassland.No matter what the sea level elevation and the size of gradient are,the soil infiltration rate of thefive kinds of utilization land decreased with the increasing of soil depth;in the meantime,the volumeweight of soil increased with the increasing of soil depth.In most of cases,the soil Initial infiltration rate is higher than the stability infiltration rate.In conclusion,the soil hydrological physical properties are obvious diversity in different kinds ofutilization land,different community structure ameliorate soil physical properties differently.high forestand shrub grassland have significant advantage,they can ameliorate soil physical propertiesperfectly,these show that the soil texture of high forest and shrub grassland is comparatively loose,itcan improve the infiltration ability of moisture and ensure that more rainfall infiltrate the soil so that canstorage in the soil or form soil midstream or underground runoff,it can reduce the wastage of surfacerunoff,this plays an important role in the function of soil and water conservation and waterconservative,what’s more,community structure can greatly maintain their own development state through regulate and control capillary porosity,we should promote planting and protection of the twokinds of land utilization.The ecological hydrological effect of terrace and sloping farmland is goodtimes and bad,the instability may contact with human activity and operating procedure.the hydrologicalphysical properties of grassland is the worst,this means that the function of soil and water conservationand water conservative of grassland is comparatively poor.Moreover,the volume weight of soilincreases with increasing of soil depth,it states the surface soil is comparatively loose,it contacts withthe amount of dry branches and fallen leaves on different kinds of sample plots and decomposing speedwhich ameliorate soil physical properties.The dry branches and fallen leaves improve the soil waterretention performance,they increase the content of soil humus and can obviously ameliorate soilphysical properties.The decomposing of dry branches and fallen leaves increase the soil organic matterand ameliorate the soil structure and physicochemical property,it enhances the ability of water storageand erosion resistance of soil.