Declining of Yezo-spruce and the ecology of root-soil area

在北海道的东京大学森林中建立了两个研究地块。一个地块位于健康的野云杉林内，另一个地块位于有害林内。比较了两个样地的土壤条件、土壤微生物区系和动物群。通过田间试验分析了酸雨对土壤动物的影响。比较了从凋落林分和健康林分中分离出的野云杉根系微生物。总体而言，衰败林分根系总细菌和放线菌数量大于健康林分，固氮细菌数量远小于健康林分。随机从琼脂平板上分离细菌，并检测每个分离菌的生理特性。健康林分菌群多样，衰退林分菌群以限制性菌群为主。退化林分土壤动物数量和多样性均高于健康林分。凋落林分土壤表层日照充足，植被覆盖。这些草本植物的存在似乎有助于在退化林分中支持更多的土壤动物。通过田间试验分析了酸雨对土壤动物的影响。对部分土壤动物有不良影响，以坡瓷动物最为显著。

Two study plots were established in the Tokyo University forest in Hokkaido. One plot was in a healthy Yezo-spruce stand and the other was in a deleterious stand. Soil conditions, microflora and fauna on soil were compared between the two study plots. Effects of acid rain on soil animals were analyzed experimentally in the field.Comparison of microorganisms isolated from the Yezo-spruce roots from declining and healthy stands was done. In general, the number of total bacteria and actinomycetes of the roots from from the declining stands was larger, while the number of nitrogen-fixing bacteria was much smaller than healthy stands. Bacteria were randomly isolated from the agar plates, and the physiological characteristics of each isdolates were examined. Bacterial flora from the healthy stand was diverse, while rather restricted groups were majorities in the isolates from the declining stand.More soil animals and the higher diversity were found in the declining stands than in the healthy stands. Soil surface of declining stands received much sunshine and was covered with herbs. Existence of these herbs seemed to have contributed to support more soil animals in the declining stand.Effects of acid rain on soil animals were analyzed experimentally in the field. Adverse effects were found on some soil animals and was most remarkable in Porcellio.