Spatiotemporal Change Of Ecosystem Services Based On InVEST Model In The Bailong River Watershed,Gansu

Bailong river watershed(BRW),located in the typical transitional ecotone among the Loess Plateau,Qinba Mountains and Tibetan Plateau,was well-known for not only its frequent natural disasters(such as landslide,debris flow and soil erosion)and the ecological barrier in the upper Yangtze River.Recently,with the development of local economic and industry,mining the increasing of human activities and the frequency of natural geohards,which all affected the change of local ecosystem services and the status of ecological security.How to assess ecosystem services appropriately? How was the ecosystem services changed at the spatial and temporal scales? How to trade off the different kinds of ecosystem services,especially with the consideration of different stakeholders? These themes and questions were becoming the research hotpots and difficulties of ecology economics,geography and sustainable development recently.In this paper,Gansu section of Bailong River Watershed(BRW)was selected as a case to study the spatiotemporal change of land use,to identify the main ecological risk sources at the watershed scale of 1990,2002 and 2010,respectively.Then,the spatiotemporal characteristics of ecosystem service were analyzed quantitatively and visualized with the parameters modification of Costanza model and InVEST model,which were the mainstream methods of regional ecosystem service recently.Moreover,the tradeoffs and management of ecosystem services were also discussed preliminarily.The main conclusions could be showed briefly as below:(1)The land use changed obviously from 1990 to 2010 in the Bailong river watershed.Cultivated land mainly distributed in the river valley and bank area of BRW,hill slope and low mountains area,which their slopes were less than 35°,and the area increased first and then decreased.The areal proportion of forest land was the highest(≥ 40%),with it shrinkage first and then increase gradually.Built-up land increased gradually while the grassland and unused land decreased.Overall,the change of land use reasonable index tended to rise gradually.(2)There were some obvious spatial differences of the main ecological risk sources in the watershed.High risk area of ecological risk sources was up to 33.31%,and its mainly concentrated in the valleys of the Bailong river between Zhouqu and Wenxian,while low risk areas most distributed in the national nature reserve and forest region.Moderate ecological risk areas distributed in Wudu district,Zhouqu county and Tanchang county,and its occupied 25% of the watershed.In different regions,the composition of main ecological risk source and the dominant source were different.More than 60% of the watershed were charactered with the main risk sources were debris flow,soil erosion and landslides,and mainly concentrated in the region with intensive human activitiesy.(3)In the Bailong river watershed,the ecosystem food production service increased obviously and its high-yield area mainly distributed in the valleys of BRW between Chengguan town of Zhouqu County and Ganji town of Wudu District,also the northwestern part of Tanchang County,where were also the high ecological risk area.The spatial distribution patterns of the total soil conservation,carbon storage,water yield and biodiversity changed similarly.High services of the total soil conservation,carbon storage volume,water yield and biodiversity mainly distributed in the national nature reserve and forest region.(4)In this study,the comprehensive ecosystem services tended to be polarity.Namely,the higher of comprehensive ecosystem services,the more kinds of ecosystem services provision,and vice versa.In the spatial distribution,high ecosystem services mainly distributed in the mountain forest regions,such as Baishuijiang National Nature Reserve,Dala-Axia-Duoer Nature Reserve,Dieshan Forest Zone.On the basis of the analysis of LUCC during the past 20 years in BRW and the reference of its possible future development,three different land-use scenarios: natural development priority scenario,urban-rural expansion priority scenario,ecological protection priority scenario,had been established to analyze the spatiotemporal change of ecosystem services in the future.The simulation results showed that the change of ecosystem services was smaller under natural development priority scenario.Urban-rural expansion scenario had the greatest influence on regional biodiversity.Under the ecological protection priority scenario,the ecosystem food production service will decrease greatly,while other ecosystem services will increase.For the purpose of geodisasters reduction and sustainability of ecosystem services,the ecological protection priority scenario fitted better for the sustainable development of BRW in Gansu.Thus,some management suggestions for environmental management were put forward on the basis of ecosystem services of Bailong river watershed.Firstly,the prevention and control of geological disasters was a priority work.Secondly,the ecological reconstruction(e.g.forests and grass restoration)and poverty alleviation should be focused and performed.At the same time,the government should also control population growth and urban expansion,weaken the GDP performance assessment.