Temporal and spatial evolution of ecosystem service value and topographic gradient effect in Northeast Chongqing

In order to study the temporal and spatial evolution of ecosystem service value（ESV） and its topographic gradient effect in hilly area,taking 11 districts and counties in Northeast Chongqing as the study area,the temporal and spatial evolution of ecosystem service value and the gradient effect of ecosystem service value of different topographic elements in the study area were comprehensively analyzed by using three periods of land cover data and relevant statistical data in 2000,2010 and 2020.The results showed that:（1）From 2000 to 2020,the land cover in the study area was mainly cultivated land and forest land,accounting for more than 89%.With the change of time,the area of forest land,water body and construction land increased,the area of cultivated land and grassland decreased,and the land cover had obvious spatial differences;（2）The forest ecosystem service value in the study area was dominant,accounting for more than 67%.With the change of time,the total value of ecosystem services gradually increased,of