The Change of Butterfly Assemblages after Artificial Gap Formation in an Urban Park

Abstract

We studied the effect of artificial gap formation on butterfly assemblages of urban forests in Expo commemorative park of Osaka which was established in 1970 and made large scale reclamation for the enhancement of biodiversity in urban area. However the biodiversity in the reclaimed forest has not increased and was lower than secondary forests in Osaka, because the uniformly grown evergreen trees made dark interior where few harbecous layer has been formed. Four gaps (15mx15m) were cleared in 2001 and other four were cleared in 2002. Butterflies were recorded in these gaps and adjacent four plots of forest interior for 10 minutes from May to September 2004. Both of the number of species and individuals were 19 and 142, respectively in 2001 gaps, 14 and 56 in 2001 gaps and 9 and 11 in the interior plots. We discussed the succession of butterfly assemblage by comparing the present study to the results of previous study in 2001. Species depending on grasslands decreased and those on shrubs increased with years after the gap formation.