| The Three Gorges Area was the hotspot for research from China to global because of its'complex topography, rich species diversity and variety community types. With the constructionproject, the regional ecological problem was not only related to the people's lives and propertysafety in this area, but impact crucially to the country's economic development. Meanwhile, theThree Gorges Reservior was an important water sources area, the study and evaluation onstructure and function of forest ecosystem, and in particular for water resource conservation inThree Gorges Reservior Area was of great significance in guidance on land use and vegetationconstruction.In this paper, the forest cover geographic information systems (FGIS) using the forestmanagement inventory data and climate data was established. The distribution of climate andvegetation in spatial was analyzed, and the vegetation structure was also provided. The modelfor leaf area index was built on the basis of investigation and monitoring of sample plot, andthe forest water conservation function in the Three Gorges Reservior, including interception,water-holding ability of litter and soil, was evaluated. The results are shown that as follows.(1)The forest cover area of Three Gorges Reservior was 2.7239 million hectares, andincludedll types, such as Masson pine forests, Chinese fir forests, cypress forests, deciduousbroad-leaved forests, evergreen broad-leaved forests, temperate pine forests,coniferous-deciduous mixed forests, coniferous mixed forests, economic forests and bambooforests, Shrubbery, The forest coverage rate reached 46.96％and the forest spatialcharacteristics showed the pattern "East higher West lower".(2)Forest subcompartments of homogeneous spatial climatic factors spatial data wasgenerated using the methods of spatial interpolation model and model simulating. Theprecipitation in summer and autumn was about 68％of annual precipitation. The day predictionmodels for different day precipitation ranks in the month were established. Meanwhile, thecorrelation model between precipitations with a different number of days of precipitation levelswas established. The model was that: P=1.7899d1+19.0732d2+33.4977d3+77.694d4, Theparameters in this model was the average of daily precipitation in the levels daily precipitation.(3)104 permanent plots and 114 temporary plots were surveyed of species compositionand community structure. The results indicated that: Forest vegetation area was rich in speciescomposition, but the rate of phanerophyte was low; there was a significant difference ofdiversity index in different type's vegetation, and the low-elevation area with high frequencyhuman activities has their lower diversity-index. The spatial distribution of population in most communities was clumped distribution, and a few artificial populations was regulardistribution.(4)The leaf area individual tree of dominant species of different type vegetation wasmeasured using the methods of standard trees and sticks standards, and the LAI simulatingmodels were established with the variables, including DBH, height, canopy density. And theresults of trees LAI and shrubs LAI calculated by the models showed that: there was greatdifference among different types vegetation. The LAI was show from max to min as follows:bamboo forsts (34.15), evergreen broad-leaved forests (9.02), economic forests (6.10),broad-leaved forests (4.48), Chinese fir forests (4.09), coniferous-deciduous mixed forests(4.05), temperate pine forests (3.78), coniferous mixed forests (3.47), shrubbery (3.25), thecypress forests (3.20) and Masson pine forests (2.20). the LAI class map of forest vegetation inthe Three Gorges Reservior Area showed that: the LAI was mainly concentrated in the 2-10,and the forest with high LAI areas are mainly concentrated in the western of Hubei Provinceand the eastern of Chongqing, with signs of "East higher West lower" the spatialdistribution pattern.(5)The experiments of plant leaves immersed and dehydration indicated that: saturationwater-holding capacity of plant leaves in the Three Gorges Reservior Area from high to lowwas deciduous broad-leaved forests (915.34g·m-2), evergreen broad-leaved forests(691.41g·m-2), bamboo forests (666.19g·m-2), coniferous-deciduous mixed forests(638.93g·m-2), shrubbery (629.10g·m-2), cypress forests (624.78g·m-2), Chinese fir forests(615.75g·m-2), coniferous mixed forests (534.35g·m-2), economic forests (467.78g·m-2),temperate pine forests (366.08g·m-2), Masson pine forests (362.52g·m-2). Plant leaves waterquantity and water immersion time was a very significant positive correlation, and the modelsof leaves immersed with water quantity, water speed and time of immersion were established.Water saturated leaf water loss and time was a function of power, Leaves water at the time waswith the countdown, correlation models of water loss of time and dehydrates speed and thetime were established.Using 2004-2006 field hydrological monitoring data, on the basis of analysis of factorsaffecting crown interception and leaf water process, the interception models of main types offorest vegetation canopy in the Three Gorges Reservior were established.(6)There was some difference of litter fall reserves among different types vegetation byinvestigation and analysis in 114 temporary plots. Chinese Fir forests reached the highest(11.610t·hm-2), followed by evergreen broad-leaved forests (10.139 t·hm-2) and temperate pinetrees forests (0.178 t·hm-2), and Cypress forests was lowest (3.948 t·hm-2) The vegetationtypes litter from the aquifer for the highest rate of bamboo forests, reaching 182.9％. Temperature pine forests reached 118.6％, second to the bamboo forests, and cypress forestslitter moisture in the lowest only 32.2％.The results of immersed experimental of litter indicate that: water-holding capacity oflitter increased with the immersion time. The quickest water-absorbing happened within aboutprevious two hours, and then decreased sharply. The trends are almost same in the differenttypes, but here were greater difference on water-holding capacity between different vegetationtypes. Bamboo litter saturated with water reached the highest weight of its own 3.36 times,followed by temperate pine trees, evergreen broad-leaved forest, the weight of its own 2.92 and2.89 times, respectively, bush minimum of 2.09 times. It was logarithmic relation between theforest vegetation types from the water-holding capacity and immersion time. There wasreciprocal relationship between the water absorption speed of the litter layer and the immersetime. And the correction relation was established between water holing capacity of the litterand the immerse time, the speed of absorbing water and the immerse time.(7)The results of soil experiment showed that: soil porosity of A- layer was higher thanthe B-layer in different vegetation types, infiltration rate to the same trends. In variousvegetation types, evergreen broad-leaved forests floor soil porosity and permeability were themaximum speed, Chinese fir forests, coniferous mixed forests and cypress forests soilinfiltration rate were of high level; economic forests soil clay content, porosity and steadyinfiltration rate was low. Masson pine forest above and soil porosity and permeability were theminimum speed. By comparing different types of soil texture and porosity and infiltration rate,it was indicated that: purple soil had the highest infiltration rate for its high non-capillaryporosity, mountain yellow soil porosity was minimum, and had the lowest soil infiltration rate,Sandy has the highest non-capillary pores, the steady infiltration rate for the highest, followedlighter soil, heavy loam and clay.(8)Analysis on the function of water conservation of the canopy, litter layer and the layerof soil in different vegetation type were done. And the results show that: when precipitationwas under small (1.79mm), the rainfall interception by the Canopy (including the undervegetation) was the major function of water conservation. Chinese fir forests, cypress forestsvegetation types such as tree canopy layer interception contributed 100％, Masson pine forestsand temperate pine forests through the shrubbery and herb layers of the tree layer penetratingrain withholding, the entire layer of vegetation retention rate of 100％. This rate decreased withsmaller rainfall, while the function of litter and soil gradually increased. When the rainfallreached 19.07 mm, the canopy interception accounted for about 11.84％～39.07％, andevergreen broad-leaved forest the maximum, bush the minimum. Woodland litter water holdingwas about 6.02％～18.45％(except economic forest), and the soil layer can absorb all holders litter flooding; the rainfall reached 33.50 mm, Canopy interception was about 8.39％～29.97％,and woodland litter-holding water was for a lower proportion of precipitation, about2.51％～8.33％(except for Economic Forest), the function of soil layer to absorb precipitation45.51％～78.13％. 0～32.36％; when the rainfall reached 77.69mm, Canopy interception about5.79％～23.13％, and woodland litter-holding water for a lower proportion of precipitation,about 1.08％～3.60％(except for Foreign Economic Forest), soil layer function to absorbprecipitation 22.78％～49.84％, runoff for 23.54％～68.67％.The total water conservation of forest vegetation was 30004.18 million m3 in the ThreeGorges Reservior Area. And the average of interception function of forest vegetation canopywas about 394.869mm·a-1, and the water conservation was about 10755.82 million m3.a-1,accounting for 35.85％of the total. The function of absorb water by the litter was about85.729mm, and water conservation was about 2335.169 million m3·a-1, which accounted for7.78％of the total. The average of rainfall infiltration by the soil layer was about 620.918mm·a-1, and water conservation was about 16913.191million m3·a-1, accounting for the 56.37％of total.Among all the vegetation types, shrubbery had the maximum water conservation andreached to 8236.849 million m3·a-1, for 27.45％of the total, the follows were Masson pineforests (8171.14million m3·a-1), deciduous broad-leaved forests (3645.747 million m3·a-1) ,coniferous-deciduous mixed forests (2486.038 million m3·a-1), coniferous mixed forests(2425.245 million m3·a-1),cypress forests (1214.012million m3·a-1), economic forests(1191.743 million m3·a-1),evergreen broad-leaved forests (901.846 million m3·a-1), Chinesefir forests (727.501million m3·a-1), temperate pine forests (665.830million m3·a-1), and theminimum was bamboo forests(338.232 million m3·a-1), which was only for 1.12％of the total.The interception of the forest canopy in the Three Gorges Reservior Area was between288.82mm and 586.00mm, and the interception rate was from 19.86％to 38.63％. Except forEconomic Forest, the other forest litter vegetation - holding capacity was between the30.58mm～117.58mm, which was about 2.43％～9.30％to the total rainfall. Infiltrationproperty of forests for soil was between 549.36mm-710.78mm, which contributed 40.42％～54.23％of total rainfall. Temperate pine forests have the maximum water conservation of allvegetation types, reaching to 1364.41mm. Cypress forest was the minimum, only 992.65mm.The Chinese fir have the highest efficiency of water conservation, which reach to 87.15％ofthe conservation of precipitation, and the lowest was bush, only 69.59％.It will provide a scientific basis for the eco-construction planning and the choice ofproject model of the Three Gorges Reservior Area by the research of forest ecosystem water conservation and distribution pattern.
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