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

在北海道的东京大学森林里建立了两个研究地块。一块地是健康的云杉林，另一块地是有害的林。比较了两个试验区的土壤条件、土壤微生物区系和土壤动物区系。通过田间试验分析了酸雨对土壤动物的影响，并对健康林和衰退林的云杉根部分离的微生物进行了比较。总体来说，衰退林的根部细菌总数和放线菌数量均高于健康林，而固氮菌数量远低于健康林。从琼脂平板上随机分离出细菌，并对其生理特性进行了检测。健康林细菌区系多样，衰退林分细菌群以限制性群为主，衰退林分土壤动物数量和多样性高于健康林分。衰退林分土壤表面阳光充足，被草本植物覆盖。这些草本植物的存在似乎有助于支持更多的土壤动物处于下降的地位。通过田间试验分析了酸雨对土壤动物的影响。在一些土壤动物身上也发现了不良反应，其中以波塞利奥最为明显。

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.