Structure Of Water Conservation Forest And Its Regulatory Mechanism On Ecological Functions In Jinyun Mountain, Southwestern China

Jinyun Mountain is located in the end of the Three Gorges Reservoir, as an important source of water in Chongqing area. Water conservation forest in this region has an important role to improved water quality. The quantitative and qualitative research on the structural characteristics and ecological functions of water conservation forest in Jinyun Mountain was conducted by using field surveys, location monitoring and laboratory analysis of the means applied to statistical analysis, to survey a large sample, the classical statistical analysis method, the weighted index method, BP neural network, gray correlation method, AHP, etc. more comprehensive and in-depth on research, respectively, and the establishment of relations between structure and ecological function of the coupling model. The mechanism on forest structure on the ecological function was analyzed by path analysis and sensitivity testing. These fill in the blanks of analysis and evaluation of water conservation forest structure and ecological function and mechanism at Jinyun Mountain. The purpose of this paper is to provide scientific evidence for the management of water conservation forest of Three Gorges reservoir area of the Yangtze River and the whole construction. The main results are as follows:The nine typical forests were studied by analyzing the overall distribution pattern of the forest by using the forest resource GIS database and remote sensing images, which contains Pinus massoniana and Broad-leaved tress mixed forest(MKF); Cunninghamia lanceolata and Broad-leaved tress mixed forest(SKF); Pinus massoniana, Cunninghamia lanceolata and Broad-leaved tress mixed forest(MSKF); Gorodnia axillaris and other Broad-leaved tress mixed forest(DKF); Castanopsis fargesiiFranch and other Broad-leaved tress mixed forest(KKF); Phyllostachys pubescens and Pinus massoniana mixed forest(ZMF); Phyllostachys pubescens and Broad-leaved tress mixed forest(ZKF) Phyllostachys pubescens and Cunninghamia lanceolata mixed forest(ZSF); and Phyllostachys pubescens Pure forest(ZPF).The non-spatial structure of stands has been studied quantitatively, and the stand density, species composition style, mixed ratio, diameter distribution, tree height distribution characteristics are indicated using a large sample investigation and classical statistical analysis, from the species composition, diameter, tree height, tree species distribution within the forest floor, and other aspects of species. Overall forest is the diameter structure of a typical uneven-aged forest. There is a wide range of tree height of the stand. The forest type on the distribution of tree height and diameter significantly. The spatial structure of forests is analyzed by the index of five parameters containing mixed degrees the size ratio of the number of angular scale, the variance mean ratio and the aggregate for the first time. The mingling degree and frequency, neighborhood comparison and frequency and spatial pattern of stands as well as the degree of aggregation within the size of tree species of the typical stands have been received. The structure of mixed coniferous water conversation forest structure type is the best, followed by evergreen broad-leaved forest, and the one of bamboo forest community is the worst.The spatial variation of soil physical and nutrient characteristics was moderate heterogeneity to evaluate and study on soil ecological functions of stands. The order of soil conservation function of forest as follows:MKF(0.422)>KKF(0.404)>SKF(0.394)>DKF(0.388)> MSKF(0.383)>ZKF(0.346) >ZMF(0.344)>ZSF(0.340)>ZPF(0.316).Water conservation mechanism of the forest in Jinyun Mountain was studied and evaluated respectively, based on the quantitative analysis on canopy, shrub, litters and soil horizon. Results showed that the hydrological function of MKF is the strongest. However, pure bamboo forest is the worst. The strength order of water conservation functions of 9 stands as follows:MKF(0.838)> MSKF(0.815)>SKF(0.738)>KKF(0.685)>DKF(0.661)>ZKF(0.648)>ZSF(0.570)>ZMF(0.452)> ZPF(0.450).Comparison of water quality of rainfall and runoff water of forest stands and the multi-method evaluation in the Jinyun Mountain, the results showed that the water quality of the output of the forest has gotten better improvidently, the buffering effect of acid rain a significant, are up to state, "Surface Water Quality Standard "(GB3838-2002) of theⅡclass of water or more, has reached the level of centralized drinking water, some plots have been basically reached for the source of water, the water level of the National Nature Reserve.The ecological functions model of water conservation forest in Jinyun Mountain was constructed by AHP, and adopt an integrated score obtained the order of the ecological functions of forests, the results showed that:MKF(0.668)> MSKF(0.612)>SKF(0.594)>KKF(0.533)>DKF(0.512)> ZKF(0.491)>ZSF(0.480)>ZMF(0.445)>ZPF(0.387). Ecological functions of forest the size of water to mixed conifer forest community is better than the evergreen broad-leaved forest community, which is better than the bamboo community.The structure factors on the ecological functions of individual factors with significant influence and the order of the direct and indirect factors influence have been received by stepwise regression and path analysis. The role of stand structure on soil conservation, water conservation, and improve the function of water quality are very significant, especially the density characteristics, tree species diversity and spatial pattern characteristics of the most prominent. The coupling model of forest structure and ecological function is constructed, as follow, Z=11.907-0.006X1+0.084X2-0.166X3+0.025X4+0.024X5-0.008X6-0.043X7+0.226X8+0.17X9+1.246X10+0.451X11 +0.058X12+0.648X13+0.771X14-0.556X15+0.436X16-2.885X17Where, "Z" for water conservation forest ecological function of quantitative indicators; "X1-X17" for the stand structure factor.The degree of influence structural factors on the ecological function of is drawn by single factor sensitivity analysis. It showed that Stand density>Soil thickness>Undergrowth density> upper forest density>litter depth>Middle forest density>Distribution pattern>Herb diversity>overall species diversity>Average dbh> Mingling degree and frequency>Tree diversity＞Neighbourhood comparison and frequency>Shrub diversity>Canopy density>Average height>Undergrowth coverage. The impact of various structural factors than significant interactions between factors together restrict the ecological functions.