Effect Of Different Vegetation Types On Runoff And Sediment Yield In Liuxihe Small Watershed

Based on the data from the experiment runoff plots located at Liuxihe small watershed,a research project has been carried out into the hydrological characteristics quantitatively,such as the canopy layer interception,the vegetation types litter layer water-holding capacity,soil layer water-holding capacity,runoff and sediment yield and so on,with the vegetation of coniferous broadleaf mixed forest,evergreen broadleaf forest,Pinus massoniana, Cunninghamia lanceolata,Phyllostachys pubescens and grassland,the results show that:(1) The canopy layer interception rate for coniferous broadleaf mixed forest,evergreen broadleaf forest,Pinus massoniana,Cunninghamia lanceolata and Phyllostachys pubescens is 21.41%,35.48%,26.22%,46.14%and 25.63%,respectively.There is a positive relation between precipitation and the canopy interception.(2) It shows a power regression between the water absorption velocity of litter and the immersion time.In general the water absorption rate for litter decreases sharply in the beginning 2 hours after soaked in water and reaches to saturation about 10 hours,and the litter layer of different vegetation types shows a good water-holding capacity,the maximum ranges from 12.02mm to 32.13mm,the water-holding capacity of litter is in following order: evergreen broad-leaf forest＞coniferous broadleaf mixed forest＞Pinus massoniana＞Cunninghamia lanceolata＞grassland＞Phyllostachys pubescens.The available interception of litter ranges from 9.69mm to 29.10mm,the available interception of litter is in the order: evergreen broadleaf forest＞Coniferous broadleaf mixed forest＞Pinus massoniana＞Cunninghamia lanceolata＞grassland＞Phyllostachys pubescens.(3) The available water-holding of the soil layer of Coniferous broadleaf mixed forest, evergreen broadleaf forest,Pinus massoniana,Cunninghamia lanceolata,Phyllostachys pubescens is 55.40mm,55.80mm,52.96mm,57.98mm and 72.54mm,respectively,and it is much more than that of grassland with 44.98mm.The soil steady infiltration rate of coniferous broadleaf mixed forest,evergreen broadleaf forest,Pinus massoniana, Cunninghamia lanceolata,Phyllostachys pubescens is 8.45 mm·min^-1,13.02 mm·min^-1,1.28 mm·min^-1,2.75 mm·min^-1 and 2.03 mm·min^-1,respectively,and it is bigger than that of grassland.The beginning infiltration rate of the soil layer for each vegetation keeps the same way. (4) The effect of different influence factors,such as the canopy of a stand or the coverage of a grassland,the thickness of litter layer,the canopy interception rate,the available water-holding deep of litter layer,the available water-holding deep of soil layer and the steady infiltration rate of soil,on the runoff coefficient and sediment yield for six vegetations in Liuxihe small watershed have been studied by means of Grey correlation analysis.The results indicate that all the effect of different influenced factors on runoff coefficient and sediment yield grey correlation reading is more than 0.65.The available water-holding of soil layer is the greatest effect on runoff coefficient in different factors,the grey correlation reading 0.740, the canopy density the smallest with 0.691;the runoff coefficient is the greatest effect on sediment yield,the grey correlation reading is 0.990,the canopy density the smallest with 0.676.(5) According to data from the runoff experiment plots,the effect of forest lands on reducing runoff and sediment yield is better than those of grasslands.Both A coniferous broadleaf mixed forest and an evergreen broad-leaf forest have a good water-holding capacity in a forest ecosystem in Liuxihe small watershed.