ELUCIDATION OF ENVIRONMENTAL FACTORS AFFECTING THE SETTLEMENT OF EGERIA DENSA IN THE DOWNSTREAM SEGMENT OF THE HAJI DAM

Abstract

 The overgrowth of Egeria densa, invasive aquatic plant, is a major issue in the upstream of the Gonokawa River. It is necessary to develop the efficient method for eradicating the nonnative aquatic plant. In this study, we quantified the coverage of E. densa with UAV on the three seasons (dormant, post-flood, and senescence seasons) and analyzed the relationships between the coverage of E. densa inhibiting throughout the seasons (source patches) and environmental factors using generalized linear models. Our results indicated that the source patches tended to exist in the upstream of the survey segment. In addition, the presence of source patches had the highest negative correlation with the fluctuations of the river discharge, suggesting that the river discharge fluctuations could suppress the overgrowth of E. densa in the river segment by preventing the formation of the source patches.