A preliminary study on oribatid mite communities in the cool temperate forest soils developed on a slope

Abstract

ササラダニ (ダニ目隠気門類, Acari : Cryptostigmata) の斜面における個体数と積の分布を京都大学芦生演習林の冷温帯林で調査した。ササラダニ成虫の個体数密度は, 斜面上部で29, 600/m_2, 斜面下部で14, 400/m_2を示した。A_o層量も斜面上部の方が下部より多く, ササラダニの密度はA_o層量と対応していた。優占種のうちEpilohmannoides esulcatus はF-H層のある斜面上部にのみ出現し, Archoplophora villosa, Eohypochthonius magnus は下部にのみ出現した。ササラダニの種の分布は斜面における土壌の環境条件を反映していた。この調査地より採集されたササラダニの種リストを作製した。8ヶ月の調査期間中, 斜面上部からは88種, 下部からは91種, あわせて108種が記録され, うち71種が上下に共通して出現した。KOBAYASHI (1974) の提案した種数―面積関係を斜面におけるササラダニ群集にあてはめたところ, 種数一面積関係による多様性はどの群集でもあまり差はみられなかった。この種数 - 面積関係は, サンプル数がことなる生物群集の調査データを用いて多様性を比較する際に有効である。

Abundances and species distributions of oribatid mites (Acari: Cryptostigmata) were investigated in a cool temperate forest developed on a slope in the Ashiu Experimental Forest of Kyoto University. Total adult oribatids density was 29, 600 per m2 in the ridge and 14, 400 per m2 in the bottom of the slope respectively. The abundances were higher in the upper than in the lower part of the slope and were related to the amounts of A0 layer. Distribution of Epilohmannoides esulcatus was restricted to the plots where F-H layer was present, while Archoplophora villosa and Eohypochthonius magnus were found only in the lower part of the slope. The distribution of each species was related to the gradient of soil conditions along the slope. The species list of oribatid mites in this study area was presented in this paper. Through the study period of 8 months, a total of 88 and 91 species was recorded in the ridge and the bottom plots respectively. Among the total of 108 species, 71 species were common to the both plots. The species-area relation model proposed by KOBAYASHI (1974) was applied to compare the diversities of different oribatid communities along the slope. The diversity was expressed by a parameter of the species-area relation and was not so different among the communities. The species-area relations model is useful for a comparison of species diversity between different communities sampled with unequal sample numbers.