河川水辺の国勢調査を活用した全国一級水系における外来植物の侵入要因に関する分析

抄録

Alien plants invasion in the river threatens river ecosystem. In addition some species negatively affect flood and water resources management. Therefore, it is significant to understand invasion factors of alien plants and to implement countermeasures against them. In this paper, we studied invasion factors of alien species by statistical model based on the national census of the river environment in Japan. Twenty-five significant invasive species were selected based on seven criteria such as invasiveness and influence on river native species in the 109 major rivers in Japan. Invasion factors such as climate features and river characteristics on each plant were analyzed by the generalized linear mixed model (GLMM) approach. Climate factors were selected to explain invasion. Flood frequency and flow regime range were also picked up as elements to illustrate over 1-ha plant community. This indicates frequency of the disturbance restrains invasive species expansion. River basin area and population also positively enhanced invasion. We compared the difference between the model results and the river census results and considered it as invasion potential. As a result Conyza sumatrensis, Eragrostis curvula, Sorghum halepense, Robinia pseudoacacia, and Ambrosia trifida were selected as the spices which might expand in the many watersheds in the future.