ANALYSIS OF IMPACT FACTORS ON REPRODUCTION FROM FRAGMENTS OF INVASIVE ALIAN SPECIES Ludwigia grandiflora

Abstract

 A main objective of this study is to know impact factors on reproduction of an invasive alian species Ludwigia grandiflora. Vegetation surveys with portable point positioning GPS devices were carried out for Ludwigia grandiflora at Yabase district on Lake Biwa shore. Area where the species grew well was 49,569 m² winter 2014, then extermination by heavy machines was conducted, however the area had expanded to 136,198 m² winter 2015. Furthermore, as a result of 240 samples reproduction experiments from fragments of the species in a laboratory, it was found that presence or absence of nodes is the main factor of reproduction. Three-way layout (nutrients, length, and diameter) analysis of variance was carried out for growth rates of the species with nodes after 10 days elapsed showed that contribution of diameter was 37.7%. It was a significant impact factor of reproduction of the species. Three-way layout ANOVA was carried out for the growth rates with nodes after 2 days, 4 days, 6 days, and 8 days elapsed, respectively. As the results, the growth rates at 2nd day with nutrients tended to be higher than that without nutrients significantly. It was found that nutrients contribute in the early stages of their reproduction.