Construction and characteristics of a supply–demand network for forest ecosystem water-yield services in the Dongting Lake region, China

Water-yield services of forest ecosystems are essential for maintaining ecological stability and promoting regional sustainable development. However, because these services are transmitted along hydrological pathways, clear spatial mismatches often occur between supply and demand. Taking the Dongting Lake region as the study area, this study quantified forest water-yield supply and multiple types of water demand, and abstracted the supply–demand relationships of water-yield services into a network model to examine their spatial matching patterns. The results showed that supply–demand matching exhibited marked spatial heterogeneity and uneven distribution. Only Shimen County, Yiyang urban area, and Yueyang urban area showed water-supply deficits, whereas most other counties exhibited water-supply surpluses. Based on local hydrological connectivity, 49 effective supply–demand links were identified, and a weighted directed bipartite network (SDN) was constructed, revealing the multiscale characteristics of water-service supply and demand in forest ecosystems. The SDN exhibited relatively simple node-link structures and sparse connectivity. The supply–demand networks of different dominant tree species showed a certain degree of similarity, but their structural complexity was generally lower than that of the overall forest network. Under the constraints of topographic conditions and hydrological characteristics, the SDN topology characterizes the spatial matching of supply–demand relationships through uneven inter-county dependence and heterogeneous potential-association intensity. These findings contribute to a better understanding of the spatial matching of forest water-yield services and can support the spatial optimization and management of forest ecosystem services.