森林植生型の造林學的研究

Abstract

1. The forest vegetation type (forest type) has a significance in its application to silviculture by indicating the growth of trees and the site quality by means of the indicator plants peculiar to the area. 2. In the northern primeval forests (Saghalien) there are three principal forest types: a) Dryopteris type (Dryopteris amurensis Takeda) b) Myrtillus type (Vaccinuim myrtillus Koch) c) Osmunda type (Osmunda cinnamomea L.) There are, however, intermediate types between each type and they show their features according to the extent of mixture of indicator plants. The same can be said in th South. For Picea jezoensis Carr and Abies sachalinensis Mast, the Dryopteris type indicates the best growth of trees and the best site quality, Myrtillus type a little poorer and Osmunda type the poorest. 3. The principal forest type in the southern primeval forests (Formosa) is the Pellionia-Diplazium type, which indicates a good growth of trees (trees are generally large) and superior site quality. The important and most widely distributed forest types of the afforested areas in the same region are: a) Pellionia-Diplazium type. (Pellionia scabra Benth, Diplazium esculentum Sw.) b) Pellionia-Diplazium-Polygonum type. (Pellionia scabra Benth, Diplazium esculentum Sw. and Polygonum chinense L.) c) Paspalum type. (Paspalum vaginatum Sw.) For Cinchona, a) and b) types are good for growth of trees while c) type is poor. 4. The forest types in the afforested areas are not always stable, and they change according to the variation of environmental factors. In the northern forests, for instance, Dryopteris type changes to Rubus type, and Myrtillus type to Calamagrostis type, and in the southern mountain forests, Pellionia-Diplazinm type changes to Polygonum type or Paspalum type. Thus both the growth of trees and the site qulity are deteriorated by overthinning or the change of the nature of soil, etc. 5. The peculiarities of the forest types, common in the North and the South are as follows: a) The ground vegetation in the forest type which indicates good site quality and good growth of trees consists almost entirely of shade grasses, while that in the forest type which indicates poor growing condition are almost entirely of heliophilous plants. b) In the primeval forests, the annual growth (+) and the volume of dead trees (-) are almost equal and there are no changes in the growing stock. There are no changes in the rate of mixture of the number of tree species. Therefore, the characteristic features of the forest types will remain unchanged. c) In the primeval forests, the trees of that forest type which indicates the good site quality are more short lived than those of a forest type which indicates poor site quality. The former type has more dead trees than the latter. d) The root systeme of indicator plants in the forest type which indicates good growth of trees are narrow and monotonous. In the vegetation which indicates poor growth of trees, the roots of the indicator plants are wide spread and they hinder the development of the roots of trees. e) The factors of the site that seem to be closely connected with the forest type are the light intensities, qualities of the ground and the quantities of nitrogen in the soil, etc. The forest type which indicates a good site quality has more shade on the surface of the ground and is rich in nitrogen. However for the soil water that good forest type is poor in the northern forests and rich in the southern forests in the dry season. 6. In the primeval forests the Dryopteris type in the North and Pellionia-Dipiazium type in the South are the best in site quality and the growing stock of stand per ha. are almost equal. It is, however, a remarkable phenomenon that, the former is rich in humus and nitrogen in the soil, while the latter is favoured with sunlight. 7. As to the application of forest type to silviculture, we must notice the following: a) In case of afforestation we should choose an area of that forest type which indicates good site quality, and always strive to maintain and tend that forest type. It is also desirable to keep the shade grasses. b) The violent changes in environmental factors become the causes of the change of forest type. If an area is bare, the forest type tends to change. It also causes deterioration of site quality. c) The forest type shows the site quality in the present state. Therefore, we must pay attention to the change of the ground vegetation.