Study On Eco-hydrological Functions Evaluation Of Water Conservation Forests At Jinyun Mountain

Forests at Jinyun Mountain are of great importance to maintain the stability of the local ecosystem and for soil and water conservation, but also can provide guidance for the construction of shelterbelt project of typical sections of Three Gorges Reservoir area. This paper aims to explore the eco-hydrological function of different types of water conservation forests in the study area and the relationship between forest structure and functions by investigating the structural characteristics, community stabilities and water conservation functions of typical water conservation forests at Jinyun Mountain. The results which are integrated in the eco-hydrological functions evaluation of water conservation forests at Jinyun Mountain are helpful to provide scientific basis for forest structure adjustments that based on these functions of water conservation forests at Jinyun Mountain even the subtropical areas. Results of this study are as follows:(1) Artificial scendary water conservation forests in study area include about 9 typical types. Mingling degree of the entire forests is over 55%; mean neighborhood comparison of the 9 forests is between 0.36 and 0.67; trees with uniform angle of 0.5 accounts for the largest proportion. Mid age forest and over mature forest are the largest part and the smallest part respectively in all forest types. Distribution of the forest DBH structure is that trees in small-middle diameter (diameter< 11 cm) are the large part of all. The forest biomass accumulation differences among forest types are big, which is the maximum for mixed forest of Gorodnia axillaris and other broad-leaved trees, while the minimum for pure forest of Phyllostachys heterocycla.(2) Bulk density of the upper lm soil is 1.37 g cm-3 for the average of all 9 forest types, and it shows a gradual increasing trend with the increase of soil depth. Hydro-physical properties as field capacity, capillary porosity, non-capillary porosity and total porosity are of great differences, but the tendency of them are quite similar as decreasing with the increase of soil depth. Soil chemical properties are generally of scarcity degree, and decrease with the increase of soil depth, however, soil pH increase as soil depths go deeper. In natural condition, net photosynthetic rate of Gorodnia axillaris is larger than other species among 9 dominant tree species in the study area, while Pinus massoniana has the smallest net photosynthetic rate of all. Precipitation (acid rain for most cases) and PM2.5 are proved generally suppressed on photosynthesis of these species.(3) Ratio of throughfall, canopy interception and stemflow of different forests range from 73.73% to 85.33%,13.36% to 26.10% and 0.09% to 1.31% respectively. The variation range of maximum interception and effective interception of litters are 1.24 mm to 2.74 mm and 0.95 mm to 2.45 mm respectively. Soil moisture is of great differences in each layer, and the max water storage changes between 515.90 mm and 662.11 mm. Soil infiltration rate changing significantly with the time passed on, although the trend of which is similar.(4) Comprehensive analysis method was used to evaluate the eco-hydrological functions of water conservation forests in Jinyun Mountain, and a forest ecological and hydrological functions evaluation system with 26 indicators was established. Score sequence of forests is approximately: the coniferous and broad-leaved mixed forest community> evergreen broad-leaved forest community> Phyllostachys heterocycla forest community.(5) Coupling analysis between five key indicators of eco-hydrological functions of water conservation forests and their structural factors was used to acquire the structure parameters of great impact on forest eco-hydrological functions, and the influence ability of top 3 parameters in turn from high to low are standard deviation of forest age, mingling degree and uniform angle. The evaluation scores calculated from the actual utilization of forest structure parameters meet the scores of forests derived from the forest ecological and hydrological functions evaluation model.Based on this, the ideal structure model of water conservation forest at Jinyun Mountain could reference the structure of mixed forest of Pinus massoniana and other broad-leaved trees. The very structure is helpful to promote the growth of trees in the forest, maintain the community stability, and give full play of forest to the ecological functions. Moreover, the adjustment of forest structure in the Jinyun Mountain area should first started from the aspects of age structure, mingling degree, and uniform angle.