| Three Gorges reservoir area has complex landform types, adequate water and heat condition and rich plant and animal species. Ecological problems of the Three Gorges reservoir area directly related to the safety of the Three Gorges Project and downstream people's lives and property, which always pay close attention to by our country and even internationally. The Three Gorges reservoir area has been listed as China's focus on the protection of Soil and Water Conservation District because of serious soil erosion and a large number of sediment silting in the reservoir area. Enhance the construction of increase forest vegetation in the Three Gorges Reservoir Area, give full play to its soil and water conservation and hydrological functions, has a significant role to improve the ecological environment of the Yangtze River basin. Studying on hydrological functions of different types of forests in the Three Gorges reservoir area has important practical significance to guide the construction and operation of water conservation shelter forest system in the reservoir area.The study object of this paper is4natural forest types (coniferous forest, broad-leaved forest, broadleaf-conifer mixed forest and bamboo forest) in Simian Mountain. We set test standards of4natural forest types at Qin Jia-gou in the study area, used the methods of field investigation and laboratory test, studied the hydrological function of4natural forest types. The hydrological function of canopy layer, litter layer and soil layer were analyzed and compared by the analysis method of correlation analysis, single factor analysis of variance, principal component analysis, gray relational analysis, etc. Considered and selected to the evaluations which could reflect the Hydrological function of4natural forest types and comprehensive evaluated them used the entropy method, the author ranked4natural forest types'order in accordance with the strength of Hydrological and ecological function, and filtered out the forest type which has the best hydrological and ecological function. The findings are:(1) Under the same conditions of precipitation, the4natural forest types'canopy interception capacity in the order of the coniferous forest> broad-leaved forest> broadleaf-conifer mixed forest> bamboo forest.The influencing priority of meteorological factors for temperate coniferous forest is precipitation> rainfall intensity> wind velocity> temperature> air humidity. For broad-leaved forest, the priority is wind velocity> precipitation> rainfall intensity> temperature> air humidity. For broadleaf-conifer mixed forest, the priority is precipitation> rainfall intensity> wind velocity> temperature> air humidity. For bamboo forest, the priority is wind velocity> rainfall intensity> precipitation> air humidity>temperature. Between the canopy interception amount of each standard land and precipitation showed a power function, the precipitation of each standard land when they reach the saturated canopy interception are102.4mm,102.4mm,101.4mm and52.2mm.From the general trend, the canopy interception increases with precipitation increases when it has not reached the saturation interception, and gradually tends to saturation interception; When the canopy interception close to or reach saturation interception, its increase will have little or no further increase.(2) The total volume of4natural forest types' litter followed by broad-leaved forest(19.68t·hm2)> broadleaf-conifer mixed forest(17.57t·hm-2)> coniferous forest(17.40t·hm-2)>bamboo forest(17.08t·hm-2).The effective storing amount of4natural forest types'litter followed by broad-leaved forest(12.79t·hm-2)> bamboo forest(11.44t·hm-2)> coniferous forest(8.70t·hm-2)>broadleaf-conifer mixed forest(5.82t·hm-2). Broad-leaved forest's litter is best for storing precipitation, and broadleaf-conifer mixed forest's litter is worst for storing precipitation; Bamboo forest's litter storing result is also well because of its natural moisture content of the lowest.The roughness coefficients (n) of undecomposed layers of4types of natural forest litter followed by broad-leaved forest(0.0369)>coniferous forest(0.0348)>bamboo forest(0.0314)> broadleaf-conifer mixed forest(0.0272); The roughness coefficients (n) of Semi-decomposed layers of4types of natural forest litter followed by broadleaf-conifer mixed forest(0.0854)>broad-leaved forest(0.0768)>coniferous forest(0.0502)>bamboo forest(0.0422); From the overall, The roughness coefficients (n) of4types of natural forest litter followed by broad-leaved forest(0.1039)>coniferous forest(0.0888)> broadleaf-conifer mixed forest(0.0880)>bamboo forest(0.0580).The litter reserves make a great impact on roughness coefficient. The correlation coefficients between roughness coefficient and litter reserves obtained by correlation analysis was0.901, and significantly related at the0.01level (unilateral). The roughness coefficient (n) and the thickness of the litter, litter reserves both showed a power function, the roughness coefficient (n) increased with the increase of the thickness of the litter and litter reserves.(3)The order of4natural forest types' soil stranded storage capacity is bamboo forest(676.0t/hm2)> broad-leaved forest(639.0t/hm2)> coniferous forest(527.4t/hm2)> broadleaf-conifer mixed forest(351.6t/hm2). The order of4natural forest types' soil maximum stranded storage capacity is broad-leaved forest(2932.6t/hm2)> bamboo forest(2586.0t/hm2)> coniferous forest(2539.4t/hm2)> broadleaf-conifer mixed forest(2389.8t/hm2).Non-capillary porosity and soil bulk density are the main factor to affect the soil saturated hydraulic conductivity, and they both have power function with soil saturated hydraulic conductivity. If the soil non-capillary porosity greater, the soil will provide more quick channels for water infiltration, and its saturated hydraulic conductivity will greater; If the soil bulk density smaller, the soil will more loose, the resistance of the water infiltration will smaller, and the saturated hydraulic conductivity will greater. Broad-leaved woodland soil moisture initial infiltration rate is the fastest(49.0mm·min-1), broadleaf-conifer woodland soil moisture initial infiltration rate is the slowest(23.0mm·min-1); Bamboo woodland soil moisture steady infiltration rate is the fastest(3.1mm·min-1), broadleaf-conifer woodland soil moisture steady infiltration rate is the slowest(1.7mm·min-1). Soil bulk density is the most important factor to affect the steady infiltration rate.(4) In the4natural forest types, broad-leaved forest's hydrological function is the best, bamboo forest's hydrological function and coniferous forest's hydrological function are similar and at an intermediate level, and broadleaf-conifer forest's hydrological function is the worst. |
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