| As the source of water for the Middle Route Project (MRP) under South-to-North Water Transfer Scheme (SNWT), Danjiangkou reservoir area is the most sensitive area for the protection of water resource. The quality of ecological environment of this area is directly related to the safety of water in North China. Biodiversity is an important indicator and evaluation criteria of the ecological environment. The implementation of MRP will change the ecological environment of the reservoir area in a certain extent, and have a certain impact on biodiversity.By summarizing previous studies and field investigation, biodiversity resources of the Danjiangkou Reservoir area were counted and analyzed. There are189families,189genera,2574species of vascular plants (including part of the cultivated species and exotic species);4classes,28ordos,96families,306species of terrestrial vertebrates;8phyla,53genera,88species of phytoplankton;43species of zooplankton;10families,27phyla,59species of macro fauna;8ordos,59genera,81species of fish;31families,66genera,111species of aquatic vascular plant.In this paper, the variation trend of plants, animals and aquatic organisms of the Danjiangkou reservoir in the past60years was studied for the first time, through the collection and analysis of-previous studies and the application of remote sensing technology. The present study provided an important basis for biodiversity conservation in this area.Remote sensing satellite images during five periods after the Danjiangkou reservoir constructed, which were in1976,1983,1993,2003and2013, respectively, were selected, then the land use types and vegetation types of each period were interpretated. The resulsts showed that in the past forty years, the cultivated area decreased by almost half, and it accounted for only31.59%of the total study area in present; the forestry area increased by nearly four times, and it accounted for32.99%of the study area, which had become the dominant land use type in the study area. The forest coverage rate showed a rising trend, in which the area of broad-leaved forest and brush incresed significantly, but the area of coniferous forest changed slightly. If the storage level of the reservoir rises from157m to170m, we predicted that the area of coniferous forest, broad-leaved forest, shrubs, grass and crops will reduce927.21hm2,1905.36hm2,11735.4hm2,289.33hm2,21136.08hm2respectively, where the submerged area of crops is the biggest, followed by the broad-leaved forest and grass.With the variations of land use types of the reservoir area, the terrestrial animals’habitats also changed, which had a. certain of effects on land animals. Although as a whole,changes of the populations varied in different animal groups and in different ecological types, the animal diversity and the quantitiy increased significantly as a whole.Through the comparison and analysis of the data of aquatic organisms before and after the impoundment of the Danjiangkou reservoir, the results showed that the species composition of phytoplankton continually changed as time passed and it presented lake type species composition; the standing crop after the reservoir built was obviously higher than that before. The species composition of zooplankton changed from that sarcodina was in the majority, and rotifers and crustaceans were rare, to that ciliate became in the majority, and rotifers in the open water and crustaceans lived in planktonic life were also in a large quantity. There was an increasing number of zooplankton, especially protozoa. The biomass of zooplankton had a dramatic rise in the1990s, especially cladocerans and copepoda. The dominant species of zoobenthos were Limnodrilus hoffmeisteri, Tubifex tubifex, etc, and other common species were Branchiura sowerbyi and some species of tubifex, etc. By40-years’succession after the reservoir built, the community structure of zoobenthos had been stabilization, with small interannual variations. From when the reservoir was built to1990s, the populations of torrential water ecological fish in Danjiangkou reservoir decreased, and the populations of static water ecological fish increased but still did not became the dominant fishery resources. Due to the interference of human activities during the late1980s and early1990s, such as large-scale grazing, some changes had taken place in fish resources. The significant increase of economic fish sunch as silver carps and bighead carp, and exotic species such as whitebait in quantity had a significant influence on natural fish, but in recent years the natural fish resources recovered in a certain degree because of the ban fishing in spring.According to the distribution and habits of different taxa and related to the construction methods, scale and sequence in time of MRP, this research focused on predicting and evaluating the impact of resettlement and reservoir inundation on biodiversity of Danjiangkou Reservoir.(1) The vegetation distributed in the elevation of157-170m in Danjiangkou reservoir area will be reduced due to the inundation. But the plant species and vegetation types affected are widely distributed in nearby areas. Therefore, the impoundment will not change the floristic composition significantly and will not cause the loss of species, but it may change the plant distribution patterns in the Danjiangkou Reservoir area.(2) The implementation of the project will have negative effects on some animals because it will occupy and change their habitats, and human activities will interfere with their lives. But with the end of the construction, the animals will migrate to similar habitats nearby, and this impact will be gradually reduced. However, it will have positive effects on some amphibious and reptiles which live in static water and grallatores, because the increased water areas are beneficial for their inhabitation and foraging. Consequently, the project will change the distribution patterns of terrestrial animals in some extent.(3) After the implementation of the project, the water flow in the reservoir will be slowed, and the nutrients of the newly flooded area will be released to the reservoir. These factors will cause eutrophication within a short period of time, and it will threaten the water quality of the reservoir. The impoundment will further submerge the spawning grounds of fish and it may change the fish resources. The increase of the area of the reservoir and the water nutrients will conducive to the growth of phytoplankton and zooplankton, and then will enrich the food for fish and provide favorable conditions for fish overwintering.Reasonable protection measures were proposed to provide theoretical guidance for the protection of biodiversity in the Danjiangkou reservoir area, based on the impacts caused by the project.Although the project will certainly have adverse impact on the biodiversity in the reservoir area, by taking reasonable protection measures through the construction process and recovery measures after the construction, this impact can be minimized, so as to protect the ecological environment of the reservoir area better. |
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