Study On Spatiotemporal Variation Of Ecosystem Service Functions Based On InVEST And CA-Markov Mode

With the rapid development of Kunming’s social economy and urban construction,the demand for water resources for the people of Kunming has also increased.Changes in the ecological environment of the water source will have a direct impact on whether the Yunlong Reservoir can provide safe,green,environmentally friendly,efficient and sustainable drinking water for the city of Kunming.In this paper,Yunlong Reservoir Basin is taken as the research area,and three representative years of land use in 2000,2010 and 2020 are selected as the research period.Based on the data of DEM,meteorology and soil in Yunlong Reservoir Basin,Arc GIS geographic information system software and In VEST ecosystem service function evaluation model are used to simulate and evaluate the three ecosystem service functions of water yield,water quality purification and soil and water conservation in Yunlong Reservoir Basin.The evaluation results are analyzed from the aspects of normalization,land use dynamic degree and coordination degree.Finally,the CA-Markov model is used to predict the future land use,and the relationship between land use change and ecosystem service function in the future is further analyzed.The main research results are as follows:(1)Simulation evaluation results of water yield service function.From 2000 to2020,the water yield service capacity of Yunlong Reservoir Basin decreased first and then increased.The average water yield in 2000,2010 and 2020 was 324 mm,253 mm and 332 mm,respectively.The overall performance is gradually increasing from southwest to northeast;the different land use types in the basin are sorted by water production capacity as urban and rural land > cultivated land > grassland > forest land.(2)Water purification service function simulation evaluation results.The trend of water purification service capacity in Yunlong Reservoir Basin from 2000 to 2020 is gradually increasing.The nitrogen output in 2000,2010 and 2020 is 103.11 t,92.79 t and 81.76 t respectively,and the phosphorus output is 6.92 t,6.19 t and 5.41 t respectively.The distribution pattern of nitrogen and phosphorus output in the three periods was high in the middle and low in the surrounding areas.The overall performance was decreasing from the middle to the surrounding areas,and the output decreased with the increase of altitude in the study area.The order of different land types in the basin according to water purification capacity is water area > forest land >grassland > urban and rural land > cultivated land.(3)Soil and water conservation service function simulation evaluation results.From 2000 to 2020,the soil and water conservation service capacity of Yunlong Reservoir Basin gradually increased,and the soil retention increased,the three periods of 2000,2010 and 2020 soil conservation amount of 2.7316 million t,2.9719 million t,3.6749 million t respectively;each area in the watershed The soil conservation amount in each region is relatively evenly distributed,among which the areas with strong soil conservation capacity are mostly in the northeastern mountains,valleys and near water systems;different land use types are ranked by soil conservation capacity as arable land > watershed > forest land > grassland > urban and rural land.(4)Results of comprehensive assessment of ecosystem service functions.Through the assessment of the comprehensive ecosystem service capacity of the Yunlong Reservoir watershed from 2000 to 2020,it shows that the ecosystem service capacity is higher in the northwestern and northeastern areas of the watershed,while it is lower in the central reservoir area,valleys and near the water system;the percentage of the area in the watershed in 2020 where the ecosystem services are of four grades of general importance,moderate importance,important and very important are in the following order 24.09%,22.88%,25.21% and 27.82%,with the generally important areas mainly located in the reservoir area,the river and the low altitude areas in the northeast of the basin,while the extremely important areas are mainly located in the northwestern and northeastern areas of the basin,and the transformation of land use types and various ecosystem services in the basin are basically at a harmonious development level during the 20 years.(5)The simulation results of ecosystem service function under land use scenarios in 2030.The land use scenario in 2030 is predicted.Under the predicted scenario,the two ecosystem service capabilities of water yield and soil and water conservation are improved,but the water purification service capability is greatly reduced,and the overall ecosystem service capability is reduced.The decrease of forest land area and the increase of cultivated land area in the basin will greatly increase the potential soil erosion,resulting in increased risk of soil erosion.The results of the study show that,compared to 2000,the three ecosystem service capacities of water production,water purification and soil conservation in the Yunlong Reservoir watershed in 2020 have all increased,and the overall level of comprehensive ecosystem service capacity has improved.In the process of future economic and social development,land use planning and water source protection in the basin,the ecological protection policy for water sources should continue to be improved,water source protection should be increased,the industrial structure of the basin should be optimised,farmers should be encouraged to develop ecological agriculture,and the coordinated development of the rural economy and ecological environmental protection should be promoted.