Responses of soil conservation function to ecosystem changes: an assessment based on RS and GIS in Changting County, Fujian Province

Soil conservation is one of the most important eco-services. Human activities which contain soil erosion control affect ecosystem changes,and ecosystem changes are also closely related to soil conservation. By comparative study of the changes of ecosystem and soil conservation,we can find out the interaction mechanism between them,understand the gain and loss of soil and water conservation work in the past,and provide guidance for further treatments. In the paper,theLandsat images are used to explain the ecosystem types of Changting County in 2000,2010 and 2016,the whole study is based on the e Cognition platform. Then a quantitative evaluation of soil conservation is conducted through the RULSE( Revised Universal Soil Loss Equation) model,in which,the quantity of soil conservation is the difference between the potential of soil erosion and the reality of soil erosion. Further,a statistical analysis is performed to explore deep reasons of soil conservation function changes from the perspective of ecosystem changes. Results show that there are mainly two characteristics of ecosystem changes during 2000 and 2016 in the county. One is the change from low cover types to high cover types,characterized by large quantity of sparse forest turning into evergreen broad-leaved forest and evergreen coniferous forest. During the years,the area of sparse forest decreased by 14729.38 hm~2(-56.75%),and evergreen broadleaved forest and evergreen coniferous forest increased by 6791. 50 hm~2( 23. 21%) and 10228. 07 hm~2( 5. 80%),respectively. The other is that a large number of cultivated lands,grasslands and evergreen coniferous forest,driven by economic interests,were turned into towns and tea orchards. During the study period,towns and tea orchard increased by4469.14 hm~2( 85.43%) and 1949.32 hm~2( 69.38%),respectively,paddy field and dryland decreased by 707.85 hm~2(-2.65%) and 344.31 hm~2(-13.66%) respectively. Soil conservation quantity in the county increased significantly during the study period,and soil conservation quantity per unit area is 217.32 t hm~(-2)a~(-1)in 2000 and 246.02 t hm~(-2)a~(-1)in 2016,respectively. Among all the eco-systems,the evergreen broad-leaf shrub and evergreen broad-leaved forest soil possess the greatest soil conservation quantity,which are more than 277 t hm~(-2)a~(-1)per unit area,but the quantity per unit area of soil conservation of urban is the smallest,below 65 t hm~(-2)a~(-1). Soil conservation per unit area of most of the ecologi