Analysis Of The Growth Characteristics And Water Concervation Of Castanpsis Hystrix And Alnus Formosana Young Growth Plantaion

With 4 years old of Castanpsis hystrix and Alnus formosana young growth plantation at the arid regions of the central in Guangxi as the research object,analysed the biomass and estimated their productivity,water holding characteristics of both ecosystem,water loss dynamic of canopy and soil layer,and so on.Aimed at revealing the growth characteristics and capacity of water conservation of Castanpsis hystrix and Alnus formosana plantation at the arid regions in Guagnxi,and provide a scientific reference for constructing a high value-added water conservation forest at arid regions in Guagnxi.The results showed that:（1）The biomass of single pant of Castanpsis hystrix and Alntus formosana plantation were 15.24kg·pant^-1、24.49 kg·pant^-1 respectively.The total amount of biomass of both ecosystems were 21.45t·hm^-2、28.51 t·hm^-2,respectively.The order of different tree layer organs of Castanpsis hystrix was leaf>branch>stem>branch root>root tip>bark,and Alnus formosana was stem>branch>leaf>bark>root tip>branch root,each component of both showed tree layer>shrub grass layer>litter layer,the net productivity of both were 4.74 t·hm^-2-a^-1 and 6.90t·hm^-2·a^-1,respectively.The biomass and net productivity of Alnus formosana plantation ecosystem were more than Castanpsis hystrix’s,its growth rate was faster than Castanpsis hystrix’s,and the trunk biomass ratio was significant,it’s an ideal tree of fast growing timber.（2）The soil bulk density and natural water content of Castanpsis hystrix（?）plantation on the soil layer of 0-60cm were between 1.41 g·cm-3～1.52g·cm-3 and 17.99%～19.39%.The steady permeation rate of soil layer of 0^-20cm was 5.81 mm·min^-1.The soil total porosity and capillary porosity of each soil layer were 54.29%、54.35%、50.23%and 53.09%、52.65%、48.72%,respectively.The maximum water storage capacity and average water storage rate of 0-60cm layer were 3177.45m³·hm³ and 36.35%.The soil bulk density and natural water content of Alnus formosana plantation on the soil layer of 0-60cm were between 1.29g·cm-3～1.38g·cm-3 and 18.46%～18.79%.The steady permeation rate of soil layer of 0^-20cm was 5.10 mm·min^-1.The soil total porosity and capillary porosity of each soil layer were 58.31%、55.54%、60.92%and 57.11%、52.73%、60.01%respectively.The maximum water storage capacity and average water storage rate of 0-60cm layer were 3495.42m³·hm^-2 and 43.30%.（3）The soil bulk density and water permeation rate in the layer of 0-60cm of Castanpsis hystrix plantation were larger than Alnus formosana’s,natural water content was not much difference.But the soil capillary porosity、the maximum water storage capacity and water storage rate of Alnus formosana plantation were higher than Castanpsis hystrix plantation,and its water loss was relatively lower,so the water storage and water conservation function of Alnus formosana plantation were much better.（4）The natural moisture content of every organs of tree layer of Castanpsis hystrix plantation was between 40.08%～45.46%.Maximum intercept of rainwater during canopy、shrub grass layer and litter layer were 8.40t·hm^-2、（?）5.78t·hm^-2 and 5.54t·hm^-2 respectively.The maximum water holding capacity of aboveground was 19.7t·hm^-2.And water loss ration of last grade branches and leaves after 48h was 44.98%.The natural moisture content of every organs of tree layer of Alnus formosana plantation was between 35.36%～60.84%%.Maximum intercept of rainwater during canopy、shrub grass layer and litter layer（?）were 5.29t·hm^-2、9.17t·hm^-2、1.33t·hm^-2 respectively.The maximum water（?）holding capacity of aboveground was 15.8t·hm^-2.And water loss ration of last grade branches and leaves after 48h was 56.49%.（5）The maximum water holding capacity in canopy and aboveground of Castanpsis hystrix plantation were higher than Alnus formosana plantation,its performance of intercept of rainwater was much better than Alnus formosana,moreover,its water evaporation loss of branches and leaves were much lower,so the water conservation function of Castanpsis hystrix plantation was slightly better than Alnus formosana plantation.