EFFECTS OF SPECIFIC ALIEN PLANT LUDWIGIA GRANDIFLORA ON ENDIMIC VEGETATION IN HARIE WETLAND, LAKE BIWA

This study aims at applying a survey method to offer the presence and coverage of each plant species in field area, so as to develop quantitative evaluation procedure for vegetation structure and diversity. Long-term monitoring surveys and vegetation surveys have been implemented in Harie wetland which is a habitat supporting a large number of rare plant species in Japan from 2011 to 2019. Main results are as follows: 1) vegetation surveys with portable point positioning GPS devices were able to provide the presence and proportion of each species in communities, along with the expansion of Ludwigia grandiflora. 2) Shannon-Wiener diversity index H without distinguishing species categories, did not reflect the real abundance change. 3) the evaluation method with periodization presented vegetation diversity with emphasis on various significance is suitable to evaluate the effects of Ludwigia grandiflora on rare species and endemic species.