Ecological infrastructure planning of large river basin to promote nature conservation and ecosystem functions.

Ecological infrastructure (EI) planning can promote regional nature conservation efficiency and enhance ecosystem functions. Watershed-scale EI research is a research hotspot in landscape ecology. This study proposed a method framework to develop EI planning in large river basins based on the connectivity of ecological processes and the integrity of ecosystems in the whole basin, as well as the typical ecological problems in each sub-basin. The framework included three parts: determining the protective EI i.e. the spatial range of the watershed ecological networks; quantifying and mapping the functional EI i.e. the typical ecosystem functions within each sub-basin; and integrating ecological networks and key ecosystem function area into an EI planning based on their spatial overlap and functional synergy. The method framework was applied in the Yellow River Basin. Results showed that spatial range of ecological networks of the basin accounted for 35.8% of the study area. Key ecosystem function area including ecosystem function important area and ecosystem function improvement area accounted for 35.6%. Spatial overlay analysis of ecological networks and key ecosystem function areas showed that they overlap spatially and have synergistic effects functionally, but core habitats existed less human activities compared to key ecosystem function area. By integrating ecological networks and key ecosystem function areas, EI planning including four spatial types: water system, core habitat area, important area for ecological function maintenance, priority area for ecological function improvement. The corresponding protection and development measures were formulated. In addition, along with the improvement of ecosystem function in the basin, sediment content, sand transport and other indicators in Yellow River has been obviously improved. It indicated that the EI construction in the basin had positive significance for river governance. Results showed that the EI planning method could improve both the spatial accuracy of nature conservation in the watershed and promote the specific ecosystem functions. It is also applicable to river management and watershed territorial spatial planning in other large river basins.