Oribatid Mite Populations in Soils of Pinus pumila Scrubs on Four Mountains in Honshu, Japan with Reference to the Total Mite Abundance and Distribution Patterns of Phthiracarus japonicus and Atropacarus striculus

Abstract

Oribatid mite populations in soils of Pinus pumila scrubs, a predominant vegetation type in alpine zones in Japan, were studied on two mountains on the Japan Sea side, Mt. Hakusan and Mt. Chokai, and on another two mountains on the Pacific side, Mt. Shogigashira and Mt. Tengu. Among sites on the same mountain significant differences in the density of the oribatid populations were detected in many cases, but the range of variation was small. The mean densities for each mountain showed similar values except for the significantly higher value for Mt. Hakusan, while the masses of organic matter on the soil surface averaged for each mountain were practically the same. Endosaprophagous species which are able to develop inside the pine needles, were represented by Phthiracarus japonicus and Atropacarus striculus, and dominated at all sites except one. P. japonicus occurred on all mountains, whereas A. striculus only on the two mountains on the Japan Sea side. Factors causing the higher density of the oribatid population on Mt. Hakusan and the distribution patterns of the two representative endosaprophagous mites are discussed.