| Dongting Lake is an important ecological barrier of the Yangtze River for social and economic sustainable development. Ecosystem services assessment of Dongting Lake shows that flood storage function of the Dongting Lake is the most important ecological function. However, it is mostly regarded as a non-organism in the current research of hydrological situation and storage of Dongting Lake area, lacks the analysis landscape structure, flood storage procession and other aspects, in particular, its lacks of analysis for procession and mechanism of interaction. Wetland landscape is the final result of various natural and human factors at different spatial and temporal scales. It has a profound influence and determines the hydrological procession of wetlands storage capacity. It is an important method to explore the changes between the structure-procession-function of the research combing landscape patterns with specific ecological functions. In this study,it based on the landscape ecology, hydrology and soil science. We analysis the influence and mechanism for the landscape pattern and structure with the flood storge function at the regional, landscape and typical ecological system three levels. The results are expected for providing a scientific basis and data management support. The followings are the main conclusions:(1) The landscape pattern in Dongting Lake area changed significantly,and the landscape types converted frequently from 1980 to 2005. Among them the paddy field, dry land, settlement area changed the most dramaticly, the beach changed less, and forest, grassland and water changed the lest. Numbers of patches of each land type and shape index have similar trends, showing surge in 1980 and 1990, unchanged from 1990 to 2000, decreased from 2000 to 2005. The Connectivity of the various land types and the largest patch index changed differently, the connectivity index and the largest patch the paddy fields, forest and the water of index changed similarly, they reduced gradually between 1980 and 2000, and then increased from 2000 to 2005. The connectivity of the Drylands, grasslands, beaches and villages, and other types have contrast changes with the paddy fields, increased from 1980 to 2000 and then decreased from 2000 to 2005.(2) Flood storage function of the Dongting Lake area decreased firstly and then increased, it corresponded to the landscape pattern changes. Results showed that the relation exist between the landscape pattern index and the flood storage function of the Dongting Lake area through gray analysis.The relation between the largest patch index and connectivity index with the flood Storage Function is the lagest (0.77 and 0.75). It shows that there were great impact between the size of the dominant patch and the connectivity of the homogeneous patch with the flood storage function. The greater connectivity, the greater flood storage function. Numbers of patches, shape index, diversity index and evenness index of landscape indices have significantly correlation with rate of sedimentation, the correlation rate changes from 0.7 to 0.78. It shows that landscape fragmentation, diversity and landscape shape complexity and sedimentation rate were positively correlated.There are no obvious impact with the others landscape index with the diversion of flow and sediment of Jingjiang three outfalls except the the largest patch index.(3) The analysis between different types of landscape changes with flood storage function showed that the largest patch index and connectivity index of paddy fields, woodland, grassland and beach landscapes the flood storage function related most closely,the relation rate are 0.73,0.84 and 0.66. It showed that the flood storage function increase with the paddy fields, forest and water increase, it also showed paddy fields, forest and water body contributed the best for the correlation between the largest patch index and the flood storage function of all the area. There were significant correlations between the landscape index dry land, settlement and other human landscape with the flood storage function. So, returning the farmland to forests and grasslands improved the flood storage function(4) It had a positive association between the numbers of patches of each land type and shape index with the rate of sediment deposition, particularly drylands, beaches, villages and other types, the correlation changes between 0.7-0.74. So the increasing of these types of landscape fragmentation pattern and shape will increase the complexity of lake sediment deposition, particularly the areas and fragmentation increasing of drylands, beaches and other types of settlement. The correlation between connectivity index and sediment deposition rate is generally small (except dryland of 0.78), all other types were less than 0.6. It showed that the rate of lake sedimentation would enhanced aggregated with the connectivity of the dryland landscape increasing.(5) There were less correlations between the landscape index and diversion of flow and sediment of Jingjiang river of the three outfalls, except the largest patch index and connectivity index water, forest and beaches. So the large connected area of woodland and beaches would improve diversion of flow and sediment of Jingjiang three outfalls. The correlations between manmade landscape (such as drylands and settlements) and diversion of flow and sediment of Jingjiang three outfalls were very small. So the drylands and settlements were not good for the diversion of flow and sediment of Jingjiang three outfalls, so these landscape should be reduced to enhance the Flood storage function for the Yangtse River.(6) Researches on the ecosystems level showed that, clear correlations between soil environmental conditions and the processes of ecosystem restoration and succession were found. The soil environment of the aquiculture ecosystem was very similar to that of the Carex marsh, indicating that natural restoration is the best approach to wetland restoration among the three types of "converting farmland to lake" (CFTL) project. The soil environment of the poplar plantation was significantly different from that of the natural marsh. However, the poplar plantation performed better in improving the ecosystem function of soil organic matter (SOM) accumulation and clay particle formation than did the reed plantation. The soil environment of the paddy was very similar to that of the aquiculture ecosystem and the Carex marsh, but the soil of the dryland was different from that of the natural wetland, suggesting that the hydrological regime is the most important factor affecting restoration of the soil environment, and that human disturbance is of lesser importance. Importance analysis and one-way analysis of variance based on factor scores both showed that accumulation of clay, total phosphorous (TP), total potassium (TK), and SOM in the topsoil were the most important processes separating the group of relatively dry systems (dryland, poplar and reed plantations, and the reed marsh ecosystem) and the group of submersed ecosystems (Carex marsh, aquiculture and paddy ecosystems). This suggests that submersion can improve the capacity of the soil environment to accumulate clay, SOM, P, and K. However, ecosystems with fertilizer input (dryland, and the poplar and reed plantations) possess higher N accumulation and urease enzyme activity, implying that fertilization can help to maintain the supply of N, but on the other hand may increase the risk of N contamination.
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