The role of river confluences and meanderings in preserving local hot spots for threatened plant species in riparian ecosystems
2011
Ōsawa, Takeshi | Mitsuhashi, Hiromune | Niwa, Hideyuki | Ushimaru, Atushi
While flooding creates diverse habitats for plants and animals in riparian ecosystems, it presents a nuisance to human settlement. Thus, such areas that are frequently disturbed by flooding are more likely to experience strong artificial control measures. This hypothesis was tested and a method was developed to identify these areas using river maps. The effects of two terrain components that could potentially influence flooding frequency (the number of confluences and the degree of meandering per unit area) on both the distribution of threatened species and the degree of artificial modification were examined at two different scales (grid sizes) using two riparian data sources. The numbers of threatened plant species and artificial constructions increased with the number of confluences and the degree of meandering per unit area. The number of threatened plant species was not correlated with the number of artificial constructions. In addition, the results suggest that confluences and meanderings provide different habitat conditions for threatened plant species. Confluences may provide more frequently disturbed habitats, whereas meanderings may provide relatively stable habitats. Based on these results, through flooding, both confluences and meanderings are important for creating and maintaining the diverse habitats used by threatened species, but these habitats are also currently threatened by artificial controls. We suggest that a per-unit-area confluence density and river length map is a helpful tool for locating local biodiversity hot spots. The identification of major reservoirs of biodiversity that are currently threatened can improve conservation and management planning.
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