| Global climate change plays a significant factor to influence the dynamic equilibrium of ecosystems. To eliminate the negative impacts of climate change and maintain social, economic and environmental sustainability have been a common issue to governments and scientists around the world. The Three Gorges Reservoir Area (TGRA) is an important ecological infrastructure and a reserve system of water resources. It is also very important in promoting economic interactions between the east and west and development of the west regions. Located in the transition zone of mountain ecosystems and water ecosystems, TGRA has its inherent vulnerability and instability. Variations of the external environmental factors are potential threat of ecosystem degradation. In this dissertation, the historical climate data, multi-source remote sensing data, basic geographic information and field investigation data were collected to study the interaction between climate-vegetation-soil erosion in TGRA based on multi-disciplinary perspective. Hence, the objectives of our study are focused on climate change trends, vegetation dynamics, spatiotemporal distribution characteristics of soil erosion risk and ecological benefits of forest vegetation in Three Gorges Reservoir Area, and initialed to reveal the response mechanism of regional ecological environment to global climate change. The results could provide essential information for policy-makers and planners to develop and implement appropriate ecological environment construction measures. The main results of this study follow as below:(1) By the monthly data of precipitation and air temperature from 22 meteorological stations in TGRA during 1960-2006, the climatic variations and tendencies were estimated based on the climate statistics methods, including the climate trending rate, Mann-Kendall trend test and moving t-test technique. The results showed that there was no significant increase in during the last 47 years, which only increased rate 0.04℃/10a. The climate trending rates of air temperature in TGRA during the different seasons, spring, summer, autumn and winter were 0.02,-0.09,0.11,0.13℃/10a, respectively. The winter air temperature in the winter showed a significant increase (p 0.05, Mann-Kendall trend test). Additionally, the variation of air temperature showed significant stage characteristics during the last 47 years, and moving t-test technique reveals that notable change of air temperature took place in 1997. Air temperature significantly decreased trend in 1960-1996, but increased quickly after 1997. The climate trending rate of annual precipitation was -8.81mm/10a in last 47 years, with all periods having no significant change points. The climate trending rate during the different seasons, spring, summer, sutumn and winter were -4.37,7.12,-13.19 and 1.62 mm/10a, respectively. The results indicated that the climate style was transformed from cold-wet to warm-dry in TGRA from 1960 to 2006.(2) By using the climatic data from 44 meteorological stations in and around the TGRA, the spatial distribution of precipitation and air temperature were interpolated based on inverse distance weighted, spline, ordinary kriging and ordinary co-kriging method, respectively. Then the results of the four interpolator methods were assessed under cross validation. Results showed that the co-kriging which takes the elevation into account, performed better than other three methods. Through analyzing the spatial distribution of precipitation in TGRA, the annual precipitation was 1000-1300mm in most area, and having an intensive precipitation center in south of BaNan, where annual precipitation was as high as 1743mm. The lowest annual precipitation was less than 1000mm in Northern XingShan. According to interpolated result of temperature in Three Gorges Reservoir Area, the spatial distribution of annual mean temperature has significant difference. The highest annual mean temperature was 8.81℃, and the lowest annual mean temperature was 8.74℃. There are three high temperature centers in ChongQing along Yangzte River valley, where annual mean temperature is higher than 18℃(3) Based on the 10-day composite NDVI from SPOT-VEGETATION with 1000m spatial resolution spanning from Jan.1999 to Dec.2009, the monthly NDVI composites were computed with maximum value composite and mean value iteration filter method to eliminate the influence of noise. Then the spatiotemporal variations of vegetation cover in TGRA were estimated using the linear regression. Results showed that the annual mean NDVI increased significantly by 17.19% in past 11 years, and the increase of NDVI in spring and autumn had contributed tremendously the most to the annual mean NDVI. The annual mean NDVI of different vegetation types presented an obviously increasing trend since the 1999, especially the maximum anomaly appeared in cultivated field by 20.97%. However, the variations had an obvious spatial difference, the pixels which annual mean NDVI increased significantly accounted for 91.32% of total pixels, and the pixels which decreased significantly accounted for 0.23%. This spatial variation was different in different season, the NDVI which increased significantly accounted for 83.84% in spring, but only 32.12% in winter. In summary, temporal and spatial heterogeneity of NDVI variation may be due to the result of a combination of factors, such as urban construction, agricultural practices, local climatic characteristics and different vegetation response to climate change.(4) Ground on the NDVI from SPOT-VEGETATION, the date of monthly temperature and precipitation of TGRA from Jan.1999 to Dec.2009, the response of vegetation cover to climatic variations was analyzed annually, seasonally and monthly. According to the study, climatic variations has weakly positive effect to vegetation growth in the past 11 years, and the primary driving factor of NDVI variation was temperature. Annual mean NDVI had positive significance correlation with temperature change (P<0.1), and no significant correlation with precipitation change. Estimated by seasons, the vegetation NDVI change had large sensitive to temperature change in spring and winter, and had small sensitive in summer and autumn. Estimated by monthly NDVI change, the vegetation NDVI in March and April had close connection with temperature, the vegetation NDVI in October had negative significance correlation with precipitation (P<0.1). The vegetation NDVI in different region with sensitivity of temperature and precipitation change was highly variable, and the vegetation NDVI in the same region responds differently with temperature and precipitation change in different seasons. Furthermore, vegetation growth has no significant correlation with contemporary temperature and precipitation change in most regions. Time-lag analysis indicated that the respondence of vegetation NDVI to temperature and precipitation had certain time-lag in TGRA, but the time-lag is variable at different growth stages.(5) Based on the systematic review of the soil erosion factors, RUSLE factors algorithms were first selected for TGRA. Algorithms were then improved according to environmental characteristics and data availability of the area. In this paper, the K-factor, R-factor, C-factor, LS-factor and P-factor were calculated by revised geometric mean particle model, R-value estimation model based on daily rainfall, NDVI power model, non-cumulative flow algorithm and Wener empirical formula, respectively. Compared with previous research, the results were reliable, and applicable to rapid extraction of soil erosion factors in the TGRA.(6) Based on the Revised Universal Soil Loss Equation, the terrain gradient, spatial center of gravity transfer model and fractal model, the variation of spatiotemporal distribution characteristics of soil erosion risk was evaluated in Three Gorges Reservoir using geographic information system in 1999 and 2009. Results showed that the risk of soil erosion has significantly decreased in the past 11 years. The area of higher than medium soil erosion intensity descreased from 3.22×104 to 2.44×104km2, and soil erosion modulus descreased from 4528.42 to 3986.97 t·km-2·a-1, the amount of soil loss decreased by 73.92×106 t. The topographic factors play the key role in spatial and temporal distribution of soil erosion in Three Gorges Reservoir Area, the spatial pattern of erosion intensity has significant difference in the terrain gradient. During 1999-2009, medium soil erosion intensity have expansion trend in the different terrain gradient, while the very high and extreme erosion intensity were squeezed. The eastern region of TGRA will be the key area for erosion control, because of the center of gravity transfer. In addition, the fractal dimension of soil erosion intensity below moderately has increased, while the fractal dimension values of soil erosion intensity upwards has moderately decreased. The results revealed that the soil erosion risk has been effectively controlled after comprehensive vegetation recovery at large area in past 11 years.(7) According to the secondary forest inventory data of TGRA and the data of social commonality, the economic values of forest ecosystem service functions, including the water conservation, soil conservation, carbon sequestration and oxygen emission were calculated by the Specifications for Assessment of Forest Ecosystem Services in China. Results showed that the forest ecosystem as a barrier of ecological safety in TGRA, plays an important role in regulating climate, soil conservation, water resources conservancy. The water conservation amount of forest ecosystem in TGRA was 2.36×1010 t·a-1. Correspondingly, the economic values were 1.44×1011 and 4.94×1010 Yuan·a-1 in water conservation and purification of water quality, respectively. The soil conservation amount of forest ecosystem was 9.9×107 t·a-1, and the economic values were 9.27×108 and 6.73×1011 Yuan·a-1 in soil conservation and nutrient conservation, respectively. The carbon sequestration amount of forest ecosystem was 9.68×106 t·a-1, whose economic values was 1.16×1010 Yuan·a-1. The oxygen emission amount of forest ecosystem was 2.13×107 t·a-1, whose the economic values was 3.27×1010 Yuan·a-1. The integrated economic value of forest ecosystem service functions amounts to 2.34×1011 Yuan·a-1 which is about 4.0 times greater than GDP in TGRA. The ecological service value per unit area of forest vegetation types showed as evergreen broadleaved forest>Chinese Fir Plantation>bamboo>temperate pine forest>mixed conifer and broadleaved forest>economic forest>deciduous broadleaf forest>mixed coniferous forest>pine forest>Cupressus funebris forest>shrub forest.In conclusion, climate shows obvious trend to become warming since the 21st century, but the feature of climate desiccation is uncertain in TGRA. The relationships between vegetation growth and climate factors are very complicated. As a whole, climate change correlates weakly positive effect to vegetation growth in recent 11 years. With the further increasing of vegetation cover, the soil erosion has shown an obvious downtrend. The forest ecosystem of TGRA plays an important role in remission of climate change, conservation of soil and water. It is also an important infrastructure for ecological security in TGRA. In recent years, vegetation cover has improved greatly based on a series of ecological projects construction.
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