樹上節足動物の組成と樹上・地表の往復

Abstract

In Japan, arboreal arthropod densities have been estimated in various forest types using the insecticide fogging method. In addition, aerial spraying of insecticides has been practiced on a large scale in western Japan since the early 1970›s to control pine-wilt disease caused by the pine-wood nematode. Using these occasions, many estimations of the density of arboreal arthropods in different pine stands have been done. The densities of arboreal arthropods in pine stands varied greatly ranging from 36.2 to 1,467/m2. Densities of arthropods were usually high in evergreen coniferous forests than deciduous broad-leaved forests, probably due to lack of food and shelter in winter on the trees. Densities of arthropods in a dry (seasonal) evergreen forest in northeast Thailand were estimated at 256.4 and 140.4 in the dry season, and 195.2 and 123.1/m2 in the rainy season by fogging method. No distinct differences are recognized between the seasons. In any case, major components are Collembola and Acari(Oribatei), regardless of the forest type. Many of them evidently go up and come down along the tree trunk between soil surface and canopy.