Study On The Effect Mechanism Of Four Typical Vegetation Types On Red Soil Water Distribution In Hilly Region Of Southern Jiangxi

The hilly area of southern Jiangxi is an important part of the hilly and mountainous barrier belt in the south,which ensures the function of ecosystem services in this area.It is of great significance to maintain the ecological security of the southern region.The hilly area of southern Jiangxi is rich in forest resources,which is an important water source of Ganjiang,Dongjiang and other rivers.The study of forest soil water in the hilly area of southern Jiangxi is of great scientific significance to the rational development and utilization of regional land space and water resources.It is of great scientific significance to improve soil ecological security.In this paper,taking Dayu County of Ganzhou City,a typical area in the red soil hilly area of southern Jiangxi,as the object of study,the sample plots of coniferous and broad-leaved mixed forest,coniferous forest,Phyllostachys heterocycla forest and fallow land were selected.Through the field staining tracer test,the soil profile was dug out,and the staining image data were obtained for follow-up processing.Soil and root samples were collected,and the soil infiltration performance index was obtained by double-ring method.A total of 216 samples of 100 cm~3 undisturbed soil,432 samples of 61.8x20 mm,36 bags of disturbed soil and 180 bags of root samples were collected.The indexes were determined by ring knife weighing method,direct shear test,wet sieve method and dry sieve method,drying method and potassium dichromate method in the laboratory.We integrate the data to set up a database to analyze the effects of different vegetation types on root characteristic index,hydrological index,soil physical and chemical properties in Gannan area,and then analyze the correlation among each index by correlation analysis.The evaluation system of soil water spatial distribution is constructed by principal component analysis,the degree of soil water distribution of different vegetation types is compared,and the evaluation of water characteristics of different vegetation types is obtained to reveal the multiple influence mechanism of soil water transport law of different vegetation types.Research shows that:(1)Among different vegetation types,the stability of soil aggregates in coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest was 148%,411%and 220%higher than that of fallow land,respectively,and their shear strength was 1.33,1.15 and 1.02 times higher than that of fallow land,respectively.The content of soil clay was 2.18,2.53 and 1.79 times higher than that of fallow land,and the capillary porosity was 1.69,1.83 and 2.43 times higher than that of fallow land,respectively.The physical and chemical properties such as soil aggregate stability and soil shear resistance of coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest are better than those of fallow land.(2)Among the different vegetation types,the water-holding capacity of coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest was 40%,67%and 135%higher than that of fallow land,and the permeability was 3.16,3.83 and 5.78 times higher than that of fallow land,respectively.Coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest showed preferential flow,while fallow land showed basal flow.The soil water storage capacity and water distribution of Phyllostachys heterocycla forest are better than coniferous forest,coniferous and broad-leaved mixed forest and fallow land.(3)In different vegetation types,the comprehensive distribution degree of soil moisture was coniferous and broad-leaved mixed forest(112.80)>coniferous forest(83.35)>Phyllostachys heterocycla forest(83.25)>fallow land(12.42).Among them,porosity,permeability coefficient and rate,and root characteristic index are the key indexes to evaluate the degree of soil water distribution.The soil water distribution of coniferous and broad-leaved mixed forest is the best,followed by coniferous forest,Phyllostachys heterocycla forest and fallow land.Generally speaking,among the four vegetation types,the physical and chemical properties and hydrological characteristics of coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest are better than those of fallow land,but the root structure of coniferous and broad-leaved mixed forest is more developed and robust than coniferous forest,Phyllostachys heterocycla forest and fallow land,and the evaluation of soil water distribution is the highest.In the hilly region of southern Jiangxi,coniferous and broad-leaved mixed forest,coniferous forest and Phyllostachys heterocycla forest can be used to ensure the ecosystem service function and maintain the ecological security of the hilly region of southern Jiangxi.