Evolution Of Ecosystem Services And Its Influencing Factors In The Upper Reach Of The Fenhe River Watershed

As the basis of human survival and development,ecosystem services not only provide human beings with the necessities of life,but also maintain the earth's life support system.Ecosystem service is of great significance to the sustainable development of regions,countries and even the world.However,excessive human interference has caused some ecosystem services to be degraded,regional and global ecological security is threatened due to insufficient understanding of ecosystem services and their relationships.As a relatively independent ecological and geographic unit in the fragile area of Loess Plateau,the upper reach of the Fenhe River watershed plays an important role in the security and development of the whole watershed with its water supply and ecological barriers.However,the ecological status of the watershed presents a complex spatial pattern due to its complicated geological environment and human activities.This article takes the upper reach of the Fenhe River watershed as the study area.We assess soil conservation,water yield,vegetation net primary production(net primary productivity,NPP),water conservation,and crop production services of 2000,2008 and 2015 based on models of In VEST(integrated valuation of ecosystem services and trade-offs),CASA(carnegie ames stanford approach),etc.,analize the spatiotemperal pattern of ecosystem services,identify their relation by using correlation analysis,radar mapping analysis and service bundles analysis.Finally,explore the influencing factors and extent of ecosystem services based on the geographical detector analyses.The main results are as follows,(1)The spatiotemporal changes in ecosystem services.Spatially,the high-value areas of soil conservation and NPP production in the three years were concentrated in the northern part of the watershed,while the low-value areas were distributed in the western part of the watershed.The spatial distribution of water yield was basically similar with water conservation,in which the high-value areas were concentrated in the north of the watershed,and the low-value areas were located in the southeast of the watershed.The high-value area of crop production was distributed in the west of the watershed,while the low value area was mainly distributed in the north of the watershed.Temporally,soil conservation service increased first and then decreased around 2008.Water yield service,NPP production service and water conservation service all gradually increased,and crop production showed a trend of first decrease and then increase with 2008 as the turning point.(2)Ecosystem service trade-offs and synergies.The relationship between crop production service and soil conservation service demonstrate a trade-off relation,water yield service was synergistic with NPP production and water conservation.The relationship between NPP production and crop production demonstrate a trade-off relation,a constant synergistic relationship between NPP production and soil conservation across the three years.Temporally,trade-off relations were identified between crop production service and the other four services in the first period(2000?2008).The crop production service and the other three services except soil conservation were synergistic in the second period(2008?2015).In addition,the relationships between ecosystem services showed difference at the bases of county or landscape.(3)Classification and spatial distribution of ecosystem service bundles.Based on the bundle concept,the ecosystem services of the study area in 2000,2008,and 2015 were divided into 4 categories.The first category was dominated by soil conservation service,water yield service and NPP production service,and the supply capacity of crop production service was the smallest.The second category was dominated by water yield service,the supply capacity of soil conservation service was the smallest,and the supply capacity of the remaining three services gradually increased.The third category was dominated by crop production service,and its supply capacity was the largest of the four categories.The fourth category was dominated by water yield service,NPP service and water conservation service,and its soil conservation service and crop production service had smaller supply capabilities.Spatially,the distribution of the four service bundles had some certain regularity and differences from 2008 to 2015.The first category was mainly concentrated in the northern part of the watershed,and its distribution area was gradually increasing in the southern part of the watershed.The second category had the largest number of towns and villages.The third category was distributed in the west and southeast of the watershed,while,the spatial distribution of the fourth category was relatively scattered.(4)Influencing factors of ecosystem services.The geographical detection analysis shows that,as a major meteorological factor,precipitation decided the spatiotemporal changes of soil conservation,water production and water conservation.And the influence of precipitation on each service varied along the time.NPP production was mainly affected by the sunshine hour,followed by human disturbance to a certain extent.Crop production was subject to a combination of meteorological factors and human activities,in which the area of farmland was its main influencing factor.In general,the study provids scientific guidance for the sustainable regional development by integrating ecosystem service bundles and influencing factors analysis.