Study On Water Balance Of Pinus Armandii And Quercus Aliena Var.acuteserrata Under Diffivient Thinning Intensity On South Slop In Qinling Mountains

South slop of Qinling Mountains region is not only a major water conservation area in China, But also is water source area of the Middle Route Project in South-to-North Water Diversion. Forest vegetation in the area is mainly natural forests or plantations and, forest growth is limited and regeneration was slow down. From accelerating tree diameter growth, Improve the economic benefit and carbon sequestration Promote strong trees to create good conditions for natural regeneration into consideration, such as the need for reasonable thinning, thinned stands have reached substantial change in species composition, stand structure and function in contrast to pre-thin stands, To understand the ecohydrological functions and processes of thinned forest ecosystem, the naturally generated Quercus aliena var.acuteserrata and Pinus tabulaeformis forest stands located in the middle elevation of South slop in the Qinling Mountains were selected for this study, thinning Intensity is 5%, 10%,15%,20% and contrast. The research approacheswas field observations. By observing change characteristics of Throughfall, stemflow, canopy interception, litter interception, soil evaporation, transpiration, soil runoff in thinned stands, Study change rule of water balance of two stands under different thinning intensity, The main conclusion are as follows :1)The middle elevation of South slop in the Qinling Mountains Huoditang forest area and Xunyangba forest area total Precipitation are 857.40 mm and 816.61 mm, average rainfall are 11.28 mm and 11.19 mm, The rainfall concentrates from July to September. The correlation of two stands under all thinning intensity between canopy throughfall, stemflow and rainfall was fitted by linear function. The correlation between canopy interception for all different thinning intensity and rainfall was fitted by power function; The peak of throughfall, trunk stemflow and canopy interception of two stands under different thinning intensity were appeared in September, Different thinning intensity of two stands produces different canopy interception, throughfall and stemflow. In general, with the increase of the thinning intensity, throughfall increased, and the trunk stemflow increased, the canopy interception decreased.2)The litter amount of thinning intensity of Quercus aliena var.acuteserrata was 20%thin<15%thin<10%thin<5%thin<contrast, Pinus tabulaeformis was 20%thin <10%thin <15%thin<5%thin<contrast; The peak of litter amount of two stands under different thinning intensity were appeared in September, The value of litter amount of Quercus aliena var.acuteserrata in July, with the increase of the thinning intensity, The litter interception and interception rate of Quercus aliena var.acuteserrata decreased, Pinus tabulaeformis was20%thin< 10%thin<15%thin <5%thin< contrast.3)with the increase of the thinning intensity, Soil bulk density decreased, total soil porosity and capillary porosity were increased. Non-capillary porosity of Quercus aliena var.acuteserrata was increased, Pinus tabulaeformis was15%thin<20%thin<10%thin< 5% thin<contrast. Different thinning intensity of two stands produces different soil water storage capacity, Soil water rate of two stands under different thinning intensity were appeared in September.general, with the increase of the thinning intensity, Soil water rate and Changes in soil water storage were increased.4)Mouth change rule of soil evaporation, transpiration, soil runoff of two stands under different thinning intensity were not significant, The peak of soil evaporation was appeared in August, Soil evaporation of October was minimum; The peak of transpiration was appeared in July, transpiration of April was minimum; The peak of soil runoff was appeared September, soil runoff of April was minimum; with the increase of the thinning intensity, Soil evaporation and soil runoff of Quercus aliena var.acuteserrata increased, The transpiration of Quercus aliena var.acuteserrata decreased. Soil evaporation and soil runoff of Pinus tabulaeformis were 20%thin<10%thin<15%thin<5%thin<contrast;15%thin<20%thin<10% thin<5%thin<contrast. The transpiration of Pinus tabulaeformis was 20%thin<10%thin<15% thin <5%thin< contrast.5)The peak of water output rate of two stands were appeared in contrast. The peak of water output rate of Quercus aliena var.acuteserrata was 94.59%, Pinus tabulaeformis was 94.29%,.Evapotranspiration make largest contribution to water total output, The most prominent is component contribution rate of water balance change. with the increase of the thinning intensity, contribution rate of canopy interception, litter interception, transpiration of two stands were reduce, contribution rate of soil evaporation, soil runoff of two stands were increase.