福岡市におけるチョウ類のモニタリング : 1992〜95年

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From 1991 to 1995, aiming at conserving butterflies and their habitats, we conducted monitoring surveys in Fukuoka City with the cooperation of many volunteers. In these surveys, we used the method of transect recording. This method consisted of walking along predetermined routes (about 1-2 km) at approximate the same time zone (between 9:30AM and 2:00PM on days with particular weather conditions (sunny, a slight wind, more than 170C) and at the same frequency (once per two weeks) and recording the species name and the abundance of each species seen in the range of 5 meters on either side and forward during walks. Using data from 10 sites in Fukuoka City with different degree of nature conservation including natural park, urban park, residential area, etc. (Mt. Sefuri, Aburayama, Konosuyama, Nishikoen, Ohorikoen, Kyudai, Hirao, Tashima and Isl. Noko), the following indices were analyzed and compared: number of butterflies (abundance),number of species, con3position of species, species diversity and degree of occupancy. From an overall assessment by giving weight to the species diversity (H') and occupation (proportion of 5 species ranked the highest), the 10 sites were divided into three groups: natural park, urban park and residential area. In order to evaluate the effects of environmental changes in local habitats, the transect routes were divided into sections and the data from each section compared. The comparisons revealed that forest species were dominant (high degree of occupancy) on woody sections. Even in similarly woody environments, however, differences were noted： while sections of somber forest bed inclining toward climax had low butterfly counts, more butterflies were seen and the degree of species diversity (H') was higher on relatively bright ones with forest edge or gaps. When the data from Aburayama, Minamikoen and Tashima were examined for changes of the above-mentioned indices during the four years from 1992 to 1995, in spite of absence of marked changes for the abundance, both the species diversity (H') and the degree of occupancy kept on decreasing at all the three sites. Potanthus fravum and Lethe diana, for example, showed a decrease in number at all sites and, moreover, there have been no records of Eurema laeta for the last several years. Although the factors controlling the decrease/increase in number of butterflies are no more than conjecture, the effects of climate, particularly an unusual weather in 1994, as well as changes in habitat conditions are discussed. In any case, the continuation of monitoring can provide the data essential to know how each species stands and to decide on measures or actions for their conservation.

福岡市におけるチョウ類のモニタリング : 1992〜95年

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