Effects of Drainage on Open-Water Mire Pools: Open Water Shrinkage and Vegetation Change of Pool Plant Communities

Abstract

Open-water mire pools play an important role in sustaining biodiversity. However, many mire pools have disappeared by artificial drainage all over the world. This study aimed at exploring how mire pools are changed by artificial drainage in terms of open water area and vegetation in Shizukari Mire, Hokkaido. We analyzed the changes of drainage ditches and open water of mire pools using multi-temporal aerial photographs. In order to elucidate how pool plant communities change by drainage, we analyzed the vegetation on the persisting pools and drained area of former pools. Our results indicated that most pools were lost soon after digging of ditches, and the remaining pools have shrunk by more diffuse, continued drainage effect. Due to open water loss, pool plant communities were considered to change towards the plant communities of drier conditions, comprising woody plants and non-wetland plant species. If the drainage continues, the remaining mire pools will ultimately disappear and the species composition of the mire could become more homogenous, being dominated by few species with high coverage.