The Study On The Waterfowl Diversity And Habitat Conservation In Xianghai Wetland

The biodiversity on the earth has been decreased greatly with the increasing of global population since the 20th century. This condition is still more serious since the《Convention on Biological Diversity》which was signed in 1992. Therefore, the conservation of biodiversity is becoming an all-important problem which should be solved firstly. Habitat destruction was thought to be the most important reason for biodiversity decreasing, therefore, the study on the habitat conservation will be the most important for the conservation of biodiversity.All the life comes from water, therefore, the wetland becomes the most important ecosystem where all kinds of the life cluster due to the existence of water. Wetland was called the"Gene pool of species"because it can provide the habitat for all the waterfowl. The conservation and ecology of waterfowl has been paid more attention then before since the《Convention on Wetlands of International Importance Especially as Waterfowl Habitat》which was signed in 1971. The diversity of waterfowl has become an important part of wetland biodiversity, and one of the crucial standards which the international important wetland is classified. However, the ecological environment of wetland is deteriorating more serious due to the unwise used wetland resource, e.g. reclamation, over grazing, and pollution, etc. Especially, the over using of water resource for economic development resulted in decreasing of the water quantity in wetland. The dried wetland has threatened the survival of waterfowl, especially those rare and endangered species with big body, which are in the high position of the ecosystem.Aiming at the status of the waterfowl diversity in wetland decreasing greatly, the Xianghai National Nature Reserve, one of the international important wetlands which locates in the Songnen Plain of Northeast China, was selected as the study area for studying the conservation of waterfowl diversity based on the investigation and remote sensing data analysis. The result of this study could serve as scientific instruction for the conservation of waterfowl diversity in Songnen plain and other area of China.The scenario of this research is as follows:①Investigation of the waterfowl species and breeding information of Red-crowned crane, a kind of endangered species which breed in Xianghai wetland. And the nesting number of Red-crowned crane could serve as an important index of the waterfowl diversity, then analyzed the characteristic of the nesting habitat of Red-crowned crane;②finding the dependency of their habitat on the hydrological condition in Xianghai with the analysis of Landsat-TM data;③159 scene of"Quick-look"images were analyzed for studying the long-term dynamic of water area in Xianghai, and then constructing some experiential models for predicting the change of water area;④ Constructing a strategy to get the utilization of water resources in local community together with the conservation of the habitat of the Red-crown cranes and other waterfowl based on the thinking of integrated river basin management.The result of field research showed that the diversity of waterfowl in Xianghai wetland changed greatly among different year, but the one of non-waterfowl species changed not so much. The change of waterfowl diversity has significant positive relationship with the nest number of Red-crowned crane, which proved a common parlance that this species is the"index species"of wetland ecological environment quality. So if we can protect the habitat of Red-crowned crane well, the waterfowl diversity in Xianghai area will be rich. The statistic analysis of the field data showed that the Red-crowned crane selects the reed communities with shallow water as their favorite nesting habitat because it can not only provide the food and nesting material, but also the hiding place from the disturbance of other animal and human. Therefore the protection of reed communities with shallow water is the key for conserving the Red-crowned and other waterfowl.The distribution of"reed communities with shallow water area"was investigated by analyzing twelve scenes of Landsat-TM data for the period of seven years when the field observations were conducted in Xianghai. A new index named Water Index (WI) was proposed in order to identify the water area by using Band-6 and Band-7 data. Its availability was proved for the seasonal variation of the water area of Xianghai Reservoir which the Xianghai Management Bureau reported. On the other hand, NDVI is employed to identify the vegetation in Xianghai. NDVI cannot distinguish reed from other species, but because reed is only one species in the water area in Xianghai, so the"reed communities with shallow water"was successfully identified by overlaying the maps of WI and NDVI. The results agreed very well with the facts that were obtained in the field study in Xianghai.The area of"reed communities in water"is naturally controlled by the variation of the total water area. Then, its long-term change was investigated by utilizing Quick-look image data, which we can download freely through the Internet, while the Landsat-TM data is expensive and we cannot afford to buy many. From the analysis of 159 scenes of Quick-look images, we found that the water area in Xianghai has a large seasonal variation, taking a maximum in late summer and a minimum in early spring. A change of the characteristics around the year of 1994 was also found, before then, the water area had rather stable periodicity between 20 km2 and 60 km2, but after 1995, it became unstable and sometimes there was no water in Xianghai. The change was probably caused by the expansion of global climate change and the propagation of water intake for irrigation from the Huolin River.Considering the seasonal variation of climate in Xianghai, Multiregression analysis was tried by separating the time for analysis into the term of water area expansion (from April to September) and the term of shrink (from October to next March). The first analysis showed that the water area in September is controlled by the cumulative flow rate of Huolin River and the cumulative rainfall in Xianghai area during the six months. An empirical relation among them was found, and the correlation coefficient between the predicted values and the measured was 0.927. On the other hand, the second analysis showed that the water area at the end of March, when Red-crowned cranes visit Xianghai, depends on a single factor that is the water area at the end of last September, because the river flow rate as well as the rainfall in the area are usually very small in winter. The correlation of the measured values with the predicted values by the regression analysis was 0.942.Comparison of the change of water area with the number of cranes'nest that was observed before at the site suggested the existence of"a critical water area"for the cranes'nesting in early spring: If the water area at the end of March is larger than 11 km2, the number of observed nests is stably larger than ten. If it is smaller than the critical value, the number of nest drops sharply. The corresponding water area in September is estimated as 16.2 km2 from the empirical formula that was deduced before. The other empirical formula was constructed from the regression analysis for the water area in September showed that the critical hydrological condition for the nesting habitat of Red-crowned crane, which will give much scientific help for further analysis on the water regulation in Xianghai.A series of approach and technique were supposed for the conservation of waterfowl habitat from the scale of Huolin River based on the thinking of integrated river basin management, which including: wisely use of the flood resource, promoting the harmony of wetland conservation and local economic development, designing the ecoregion in Huolin River roughly, and a level of river flow rate was proposed for conservation of Xianghai wetland from the scale of Huolin River. If the extremely season occurred in Xianghai( the rainfall is only 200mm from April to September), the flow rate of Huolin River necessary to keep the water area of Xianghai to the critical level is 13 m3/s, as a monthly averaged value from April to September. Consideration of the actual rainfall in Xianghai and the monthly averaged river flow rate in Tuliemao, if the rainfall is 250mm from April to September, the river flow rate should be 5m3/s, which will be enough for the conservation of cranes'nesting habitat in Xianghai wetland theoretic. However, we must regulate the intension of water use between the area of Tuliemaodu and Xianghai, which should be controlled at some level.