27 森林土壤の微生物学的研究 : I.スギ人工林の土壤微生物相に就いて
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概要
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1. This article deals with the microbial population, together with the subaerial vegetation and the edaphic features, of plantation of Cryptomeria japonica D. Don in Iwate, one of the northernmost prefectures of the Main Island of Japan.2. This forest is comparable with th I_α type of natural forest. The field layer is dominated by Sasamorpha purpurascens. Shrubs, such as Marlea macrophylla var. trilobata, Kerria japonica, Aucuba japonica var. borealis, Acer mono var. eupictum, Callicarpa japonica, Lindera membranacea and Helwingia japonica, are constantly present.3. The soil of this forest consists of a kind of brown forest soil for the most part, while a minor area is covered with the volcanic Undo soil "black". It is weakly acid (close to pH 6), moderately moist and comparatively rich in nitrogen. These notable features of the soil are closely bound up with its characteristic micro-flora to be referred to below.4. In this forest there are protein-decomposing bacteria and actinomycetes abundant in comparison with those of most coniferous forests, but admittedly less than in neutral soils.5. The fungus population is predominated by Mucor and Penicillium, Trichoderma being by far fewer, while Aspergillus is nearly lacking. The number of moulds is far less than in loamy ones. There is no doubt that bacteria and actinomycetes do play an important role in the soil metabolism.6. Cellulose-decomposing bacteria, notably aerobic ones, are more or less plentiful, whereas fungal growths are hardly observed on the strips of filter paper partly immersed in the culture solulion. It follows from this that the decomposition of cellulose is very likely to be virtually performed by the bacterial agency.7. Nitrifying bacteria are present, and, in reality, a considerable nitrification is capable of taking place in this soil.8. Nitrate-reducing or denitrifying bacteria occur in abundance. It seems that their activity is very remarkable.9. This forest soil is free from Azotobacter but relatively rich in the Clostridium group.10. The F- and H-layers of soil interwoven with the rootlets of Cryptomeria japonica and other plants and containing a great deal of organic matter harbour the vast majority of common bacteria, actinomycetes and moulds, whilst a minority of them inhabits the A-layer, the B-layer supporting only a poor population of them. On the contrary, bacteria of specific physiological groups are found principally in the A-layer, partly in the F- and H-layers and rarely, if any, in the B-layer.
- 1952-05-25