Ecosystem Services Assessment And Its Driving Forces In The Bailongjiang Watershed Of Gansu

Bailongjiang watershed is a typical transitional ecotone, which stretches from Tibetan Plateau to the Loess Plateau and the western Qinling mountainous area. It,s not only the water source conservation area, but also the important ecological barrier in the upper Yangtze River. Recently, with the development of the regional economy and the rapid growth of population, many environmental problems, such as, overexploitation of the forest and grassland resources, aggravated mining, and frequency occurrences of natural disasters, had profoundly affected the provisioning services and the human welfare. Ecosystem service is the benefits that people obtain from the ecosystem. Moreover, the global climate change, landuse, natural disasters and human activities, would inordinately affect regional ecosystem services. It is important to analyse the spatiotemporal patterns of ecosystem services, to analyse the variation of ecosystem services under the various interferences like climate change, landuse and human activities, for the maintenance and conservation the regional ecosystem and sustainable development of human welfare. For this purpose, based on “3S” techniques, combined In VEST model with statistical data and field investigation, in this study, Bailongjiang watershed was selected as a case to analyse the spatial and temporal variation characteristics of ecosystem service and its driving forces. The preliminary conclusions are listed as below:(1) From 1977 a to 2014 a, the total number of soil retention, carbon storage and habitat quality was decreasing first, and then increasing. However, the total number of water yield coverage showed a decrease after the first increase and then increased. The higher value subregion of these four ecosystem services mostly centered on the nature reserves and forestry management area charactered with the lower intensity of human activity and lower risk of natural disasters. On the contrary, the lower value regions were scattered in the valley along the river bank, farming areas, urban and rural settlements in the Bailongjiang watershed. The crop production function increased gradually, and the higher value subregions distributed at Tanchang country and Wudu district.(2) In the study period, the cultivated land area climbed up and then declined. Conversely, the forest land coverage decreased at the beginning and then increased. The area of construction land continued to increase. As to the different land use types, forest land played the most significant role in promoting regulating services and supporting services. Meanwhile, the increase of forest land and grass were the main reason to improve the ecosystem function of carbon storage, soil retention, water yield, and maintaining habitat quality. At the same time, the crop supply service was increased with the improvement of the ecological environment and the adjustment of the agricultural planting structure.(3) In Bailongjiang watershed, the higher value subarea of intensive human activity distributed like a stipe along the valley of main stream. The lower value subarea principally distributed in the nature reserves and forestry management areas. The correlation analysis showed that the human activity was the main driving factor for the decrease of water yield, regulation and supporting services. In particular, the change of human activity intensity had a remarkable effect on habitat quality.(4) As to the spatial pattern of natural disasters, extremely high risk area mainly concentrated in the valley of the Bailongjiang watershed among Zhouqu, Wudu and Wen country. The lower risk area primarily spread over the stony hilly land with less surface disturbance, especially like nature reserves and forestry management areas. The correlation analysis indicated that the occurrence of natural disasters was the main driving force for the declining of the function of ecosystem services.(5) From 1977 a to 2014 a, the climate in Bailongjiang watershed showed widespread warming. The rise of temperature will increase the production function of the farmland ecosystem, however, the soil conservation function was not affected apparently by the temperature. The effect of the temperature on the water supply function was related to the climate change pattern of Bailongjiang watershed. The increasing of precipitation was good for the maintenance and improvement of ecosystem service functions.(6) Based on the typical topographic characterics and the main ecosytem service types, Bailongjiang watershed can be divided into 7 ecological function subregions. Namely, Minjiang mountainou agriculture ecological function subarea, Baishui- jiang watershed ecological conservation subarea, Upper Bailongjiang watershed carbon storage and biodiversity protection subarea, Lower Bailongjiang watershed soil conservation ecological function subarea, Bailongjiang watershed valley agriculture ecological function subarea, Bailongjiang watershed valley with geo- hazards prevention ecological function subarea, and Bailongjiang watershed water supply ecological function area.