Study On Spatiotemporal Variation Of Ecosystem Functions Under The Influence Of Climate Change And Human Activities In The Cross-border Tumen River Basin

Under the comprehensive effect of climate change and human activities,the water ecological environment has undergone profound changes.Therefore,it is of great significance to study the changes of water quantity and quality under the influence of climate change and human activities,to clarify the driving force of water resources evolution,and to quantitatively evaluate the water yield function and water purification function of the watershed,so as to reasonably plan the land use pattern,adjust the agricultural planting structure,and alleviate the contradiction between supply and demand in the future.For cross-border basins,due to the confidentiality of hydrological and water resources data,the overall research is lagging behind.In order to effectively respond to climate change and rationally develop and utilize cross-border water resources,it is necessary to carry out research on cross-border basin climate change response,cross-border water pollution,cross-border ecosystem change impact and other key issues.Based on InVEST model,this study evaluated the ecosystem functions of the cross-border Tumen River Basin under the influence of climate change and human activities,simulated the water yield and water purification functions of the basin,and analyzed the spatiotemporal dynamic changes of the two functions.Through the comprehensive evaluation and analysis of the water yield function and water purification function of the cross-border Tumen River Basin,we can achieve the coordination and unification of the water ecological environment stability and social and economic development in the cross-border area,provide theoretical reference for the cross-border water resources management,and achieve the goal of sustainable development of the basin community.The main results of this study are as follows:(1)From 1977 to 2016,the precipitation in the cross-border Tumen River Basin showed a trend of first increasing,then decreasing,and then increasing,and its high value precipitation areas were mostly distributed in the northeast and southwest.The temperature in the north of the study area decreased,while the temperature in the South increased.The distribution of potential evapotranspiration in 1986(1977-1986),1996(1987-1996)is opposite to that in 2006(1997-2006)and 2016(2007-2016).(2)During the period of 2000-2020,the land use in the cross-border Tumen River Basin is covered with woodland and cultivated land,followed by grassland,artificial surface and water body,and bare land and wetland are relatively less.As time goes on,in general,the cultivated land in the cross-border Tumen River Basin has increased.The forest land has decreased in a large area.The grassland has increased.The wetland has decreased.The water body and artificial surface have increased.And the bare land has increased significantly.(3)Under the background of climate change,in the past 40 years(1977-2016),the annual volume water yield of the cross-border Tumen River Basin showed a trend of first increasing,then decreasing and then increasing.The water yield function of the study area showed a trend of first strengthening,then weakening and then strengthening.And the water purification function showed a trend of deterioration.With the change of precipitation,water yield and total output of nitrogen and phosphorus showed more in high precipitation area and less in low precipitation area.(4)Under the background of land use change,the average annual volume water yield of the cross-border Tumen River Basin showed an increasing trend,and the average annual total output of nitrogen and phosphorus showed a trend of first increasing and then decreasing.The results show that the change of nitrogen retention and land use change of different land uses in China and North Korea are consistent.The change of nitrogen retention and land use change of different land uses in China is consistent,while the change of phosphorus retention of different land uses in North Korea is consistent with that of cultivated land,grassland,water body,bare land,woodland and wetland,but not with that of artificial surface.The contribution of cultivated land to nitrogen and phosphorus retention was the largest.(5)This paper studies the contribution rate of climate change and human activities to ecosystem function in the cross-border Tumen River Basin.The impact of climate change on ecosystem water yield function is greater than that of human activities,and the impact of human activities on water purification function is more significant.