Mapping lateral and longitudinal hydrological connectivity to identify conservation priority areas in the water-holding forest in Honghe Hani Rice Terraces World Heritage Site

Context Hydrological connectivity (HC) reflects the flow processes of water and sediment thus affects hydrological services at different scales. Water retaining forest plays an important role in the sustainability of water regulation and provision. Objectives Used the water-holding forest area of the Honghe Hani Rice Terraces World Heritage Site as the study area and, with a modified HC, to calculate and analyze the lateral and longitudinal HC and to identify the conservation priority areas. Methods We modified the popular Borselli's index of connectivity (IC) into MIC by introducing soil factors with 81 samples, analyzed the HC characteristics by sampling belts, identified the conservation priority area by hotspots analysis at watershed and sub-watershed scales, and verified the MIC with field-measured water level and FIC index. Results The HC value follows a normal distribution with the average value of 8.03. Its lateral characteristics decrease from river valleys to mountain ridges, whereas its longitudinal characteristics decrease from lower to higher rainfall; this result reflects an obvious spatial gradient distribution of water-holding functions along elevation. Hotspot analysis shows that subwatersheds F and G are the conservation priority region for water-holding. The precision of the MIC is better than Borselli's IC because of the addition of soil factors. Conclusions The MIC is an effective index to reflect the spatial gradient or patchy pattern of hydrological services. Its patterns can be identified by their lateral and longitudinal directions or by the hotspots of spatially clustered yet connected areas of high water-holding capacity.