Abstract
Dam construction is a major threat to terrestrial ecological processes that exhibit spatial variation. As an effective indicator of species movements at large scales, the dynamics of forest landscape connectivity for the dispersal abilities of local species such as primates both upstream and downstream of the Manwan hydropower station were compared in three periods: before, during, and after dam construction (in 1974, 1988, and 2004, respectively). The equivalent connected area (ECA) index which was modified from the probability of connectivity (PC) index based on the graph theory was applied in this study. We used this method to analyze the spatial and temporal changes in the overall forest landscape connectivity due to dam construction. The results showed that forest connectivity decreased after dam construction. The forest connectivity upstream was much greater than that downstream in 1974 but was lower in 1988 and 2004. The importance of connectivity increased with increasing dispersal distance. Only 8, 12, and 18% of forest patches of small area exhibited changes in 1974, 1988, and 2004, respectively. Most of the large habitat patches (i.e., those with dECA values >50%) remained stable, and the greatest patch changes were found at a dispersal distance of 400 m in all three periods. These large forest patch changes often occurred near the boundary of the study area. The Betweenness Centrality indicator, which identifies patches as stepping stones while accounting for ecological processes and biological flows at a larger scale, indicated that some habitat patches near Manwan Dam acted as stepping stones in maintaining the forest connectivity. Furthermore, rank correlations between the forest patch area and the three dPC (intra, flux, connector) fractions indicated that the dPCflux indicator can be used to measure the prioritization of habitat patches.
Highlights
Dams are considered one of the most important human disturbances to river basins
Our results indicated that landscape dynamics and fragmented watersheds influenced the connectivity of the adjacent landscape, in 2004
Our results suggest that dECA(PC) may be an appropriate indicator for identifying critical priority habitat patches as connectivity providers in the areas upstream and downstream of Manwan Dam
Summary
Dams are considered one of the most important human disturbances to river basins. They provide many economic benefits, their negative effects on ecological processes and habitats cannot be ignored (Bombino et al, 2006). After the impoundment of a dam, spatial differences occur in landscape pattern and related connectivity between the upstream and downstream stretches of a Ecological Connectivity Affected by Dam river. The connectivity of natural habitat patches is disrupted and fragmented, and vegetation is submerged by the impounded water (Gordon and Meentemeyer, 2006). It is essential to measure the impacts of spatial changes of habitats and habitat connectivity to preserve biodiversity and understand the ecological effects of dam construction
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