Study On The Function Of Water Conservation With Three Main Forest Types In Dagangshan Mountain Of Jiangxi Province

The relationship between forest and water is always the focus of ecology, and water conservation function is one of the most important functions of forest. Therefore, the water conservation function of Chinese fir forest, evergreen broad-leaved forest and phyllostachys pubescens were studied in Dagangshan Mountain of Jiangxi province. That is cardinal significance to the Dagangshan area, by studying the characteristic of water conservation and storage of the canopy, litter layer and soil layer, the water conservation function was evaluated using Topsis method, and the results could propose the basis and method of forest structure adjustment, and provide the theoretical basis of building and managing of local forest.(1) We observed31rainfalls in experimental area. The total rainfall was531.6mm.There were14light rains,9moderate rains,6heavy rains and2storm during the observation. The duration of rainfall was between0.02and1.03h. The intensity of rainfall was in0.95mm/h-22.86mm/h.(2) Both throughfall and throughfall rate of phyllostachys pubescens were the maximum, which were382.6mm and71.9%, and for the evergreen broad-leaved forest, their values were348.7mm and65.5%, respectively. The throughfall presented distinct spatial variability within each forest. Stemflow fraction of Chinese fir forest, evergreen broad-leaved forest and phyllostachys pubescens was1.4%>8.9%and8.8%, respectively. The moisture degree of forests before a rain event greatly influenced the quantity of stemflow, and for Chinese fir plantation, this effect was greater than for two other forests. The canopy interception and interception rate had same order like Chinese fir forest> evergreen broad-leaved forest> phyllostachys pubescens. The canopy interception and rainfall had a good correlation, In other words, in usual rainfall case, the interception rate of Chinese fir forest is greater obviously than both other forests.(3) The total thickness within the three samples of forests ranged from1.67to3.3cm and decreased in the order of Chinese fir forest> evergreen broad-leaved forest> phyllostachys pubescens. The litter accumulation fluctuated between4.70and5.42t/hm2., and they obeyed the same order as evergreen broad-leaved forest> Chinese fir forest>phyllostachys pubescens. Maximum soil water-holding capacity of Chinese fir forest was the maximum (12.60t/hm2), and highest water-holding proportion of evergreen broad-leaved forest was the biggest(285.24%), The relationships between water-holding rate and immersion time of whether semi-decomposed or un-decomposed litter in all different fir forests were significantly fitted by Logarithmic equation(Q=aln(t)+b). The relationships between water absorption speed rate and soaking time were described by power function(V=ktn).(4) The total porosity different forests had an order like evergreen broad-leaved forest> phyllostachys pubescens>Chinese fir forest, however, the order was contrary in term of soil bulk density, which ranged from0.98to1.22g/cm3. While soil effective water storage showed an order like phyllostachys pubescens>evergreen broad-leaved forest>Chinese fir forest, and ranged from1126.53to1142.76t/hm2.Soil stable infiltration rate of different forests stand ranged from2.36to4.80mm/min, in an order of evergreen broad-leaved forest> Chinese fir forest>phyllostachys pubescens.(5) the evaluation results by Topsis method showed that the sequence of water conservation function with the three main forests is like evergreen broad-leaved forest> Chinese fir forest>phyllostachys pubescens. It implied that in the ideal state,the water conservation function of evergreen broad-leaved forest is superior to the other ones.