| Dongting Lake is located in the southern bank of the middle reach of Yangtze River, and Three Gorges Project(TGP) is the largest water conservancy project of Yangtze River. Based on the use of methods and technology of Landscape Ecology, Remote Sensing, Management Science, Mathematics and Computer Science, this paper aimed to compare the characteristics of landscape pattern changes of Dongting Lake Wetland before and after the operation of TGP, and tried to evaluate establish evaluation index system of the wetlands ecosystem health from the view of Landscape Ecology, furthermore, evaluated the health of Dongting Lake Wetland from the perspective of temporal and spatial variation. The content and major conclusions in this paper included:(1)The changes of landscape pattern in Dongting Lake wetland before and after the operation of TGP.Based on the six periods remote sensing data in the studied area (1987-2008), this paper analyzed the characteristic changes of landscape pattern of Dongting Lake Wetland by employing Markov, and the three main periods divided by before construction of TGP (1987-1998), under constructing of TGP (1998-2003), after operation of TGP (2003-2008). It turned out that degree of fragmentation of landscape increased significantly in research area, presented as the number of plaque had increased and the density of plaque had risen. During1987-2008, the number of plaque had increased from0.61to0.76per square kilometers, the average plaque area had decreased from163.28to162.26per hectare, landscape diversity index had increased from1.36to1.91, evenness index had increased from0.68to0.87, shape index had increased from43.07to62.84. The level change of each landscape type had its characteristics. The shape index of water had decreased from27.23to27.02since1987to1993, then risen to27.78in1998, and decreased from31.72to29since2003to2008. During1987-1998the plaque number of sediment had increased significantly, and decreased during2003-2008, and the largest plaque area had increased. The degree of landscape fragmentation of sedge bottomland and reed bottomland had increased from the year of1987to1998during the construction of TGP, decreased during1998-2004, and increased again during2004-2008after the operation of TGP. The degree of landscape fragmentation of shelter forest had experienced from decrease to increase to increase again, its area had experienced from increase to decrease to increase again, and its shape index had experienced from decrease to increase. The area of cultivated land and forest land had experienced from increase to decrease, and the average plaque area decreased significantly before and after the construction of TGP. In1987-2008, the number of construction land plaque had increased from3686to5028.(2) An analysis on the duration of Dongting Lake wetland ecosystem health before and after the operation of TGP.This study evaluated the ecosystem health condition of Dongting Lake Wetland on a temporal series by employing single-factor and multi-factor comprehensive evaluation methods. The result showed that the Composite Evaluation Index (CEI) of the ecosystem health condition of Dongting Lake Wetland during1987-1998(before the construction of TGP) was0.2806, and the CEI was0.2744during the construction period of1998-2003, and0.2806in the period of2003-2008(after the TGP was finished). Based on the classification of wetland ecosystem health condition cited in this paper, the health condition of Dongting Lake wetland ecosystem was all sickness (CEI:0.2-0.4), the ecosystem had low dynamism, suffered from great pressure, and leading to a degradation of the ecosystem. The degree of the degradation of Dongting Lake Wetland was not severe, and the speed of degradation was slowing down.(3) An analysis on the spacial variation of Dongting Lake Wetland ecosystem health after the operation of TGP.Analyzed the spacial variation by employing analytic hierarchy process and fuzzy comprehensive evaluation method, this study compared the wetland ecosystem health condition among the East, South and West Dongting Lake after the operation of TGP in2008. The result showed:the wetland ecosystem health index of the East Dongting Lake was0.2515, the West Dongting Lake0.2478, and the South Dongting Lake0.2208. All of these three members indicated in heath condition Level III (0.2-0.4), and the ecosystem health condition of the East Dongting Lake wetland was the best, and the ecosystem health condition of the West Dongting Lake wetland was a little worse.(4) The influences of TGP on Dongting Lake wetland landscape pattern and ecological health.The influences of TGP on Dongting Lake wetland landscape pattern attribute to mainly sediment process, the succession of wetland hydrology, sediment deposition, and land use change. The main changes of Dongting lake wetland ecosystem health after the operation of TGP presented as: the cutoff time of three water entries of Jingjiang reach extended, the transfer environment of aquatic organisms interferenced, wetland ecological environment vulnerabled, biodiversity decreased, floods frequent in wet season increased, drought in dry season spreaded, water surface area of Dongting Lake decreased, aquatic shipping function degradated. |
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