Ecosystem service flows in Karst area of China based on the relationship between supply and demand

The continuous supply of ecosystem services is the basis of social and natural sustainable development. Human meet their demand and improve well-being through consuming ecosystem services. Research on ecosystem service flows contributes to our understanding of the completed delivery processes of ecosystem services and the relationship between ecosystem services supply and demand. It has great significance for achieving regionally sustainable development and improving human well-being. A variety of models and methods such as RUSLE, InVEST, CASA were used to calculate the supply and demand of soil conservation, water yield and carbon storage. The supply-demand balance and ecosystem services flow were analyzed and mapped. The results showed that:(1) the supply and demand of soil conservation, water yield and carbon storage showed an increasing trend during 2000-2015, with supply increasing by 679.52 t/hm~2, 2.2×10~5 m~3/km~2, 72.91 t/km~2, while demand increasing by 298.6 t/hm~2, 0.04×10~5 m~3/km~2, 168.36 t/km~2, respectively.(2) In the whole study area, the supply of three ecosystem services is able to meet the demand. The supply-demand ratio of soil conservation and carbon storage was decreasing, while water yield was increasing.(3) Soil conservation high service flows were mainly distributed in Heishui River Basin in Yunnan, Yalong River Basin in Sichuan, and Beijiang and Dongjiang River Basin in Guangdong. The Hongshui River Basin in Guangxi was the demand area of water yield in 2000, and transferred into high service flow in 2015. Carbon storage high service flow was mainly distributed in the southwest of Yunnan, and the direction is from the southwest to the northeast.