Land use/land cover changes and its impact on ecosystem services in ecologically fragile zone: A case study of Zhangjiakou City, Hebei Province, China

Land use/land cover (LULC) changes are likely to become more frequent and intense as a result of anthropogenic activities and may significantly affect human welfare by modifying ecosystem services (ESs). Understanding the impact of LULC changes on ESs value and the interactions among ESs could result in improvements in current land use policies and provide a scientific basis for the formulation of new policies in ecologically fragile zones. A case study was conducted in Zhangjiakou City, which is considered a typical ecologically fragile mountainous area in China, to examine the effects of LULC changes on ESs value and the interactions among ESs, including carbon sequestration and oxygen production (CSOP), water yield (WY), soil conservation (SC), sand-fixing (SF), and agricultural production (AP) from 2000 to 2015. Our results showed that ESs in Zhangjiakou City benefited substantially from existing land use policies and their "win-win expectations." There were dramatic changes in the LULC types over the study period, especially in forestland, grassland, and arable land, with a significant impact on ESs value. LULC changes resulted in a significant increase in ESs value (US$ 3147.44 million), with the maximum increase occurring in AP (US$ 2255.19 million). However, LULC significantly decreased the value of the WY by $61.91 million, which mainly resulted from the degradation of arable land, forestland, and grassland. Strong trade-off relationships between WY and SC, CSOP and SC, SC and SF, and SC and AP were observed in 2000. Trade-off relationships were markedly weaken by LULCCs but increased by human activities when related to AP. Finally, a new spatialization approach of AP was designed and quantitative method of trade-off index was improved based on economic value. These results could offer some suggestions for land space optimization and ecological construction in Zhangjiakou City as well as in the similar regions in China, and provide some scientifically basis on the research area of coordination development of multi-functions of land use or geographical functions.