植生史研究
Online ISSN : 2435-9238
Print ISSN : 0915-003X
07 巻
選択された号の論文の2件中1~2を表示しています
  • 中村 俊彦
    1991 年 07 巻 p. 3-14
    発行日: 1991年
    公開日: 2021/07/28
    ジャーナル オープンアクセス
    The subalpine forests of Central Japan dominated by Tsuga diversifolia, Abies vcitchii, A. mariesii and Betula ermanii are similar in structure and composition to the boreal forests prevaling at high latitudes of the Northern Hemisphere. Tsuga diversifolia is abundant at lower elevations, and Abies spp. are dominant at higher elevations. Among Abies species, Abies veitchii is abundant on the Pacific Ocean side, and A. mariesii on the Japan Sea side. Betula ermanii is prevalent around the forest line or on sites after forest destruction by forest fire and tree fellings. The primary succession of subalpine forests was studied on Mt. Fuji and the other volcanic mountains. The pioneer communities on the volcanic desert consist mainly of lichens and mosses. After a stage dominated by herbs, communities of deciduous scrubs, e. g., Salix, Alnus, Betula and Larix develop. The scrubs are followed by Larix forests, which are in turn replaced by Abies forests. Finally, the forests climax with closed canopy Tsuga forests. Tsuga forests are recognized as one of the most typical climax communities in the subalpine region. However, at higher elevations or along ridges, other types of climax communities, either Betula and Abies forests, occur. Patterns of forest regeneration in subalpine regions were classified into five types based on the following criteria : upgrowth juvenile, substrate for upgrowth, upgrowth species and size of the regeneration unit. 1. Gap type : Endogenous agencies such as death or fall of senescent stems result in scattered gaps in climax forests. They were subsequently occupied by young stands, consisting of Abies and Tsuga. The young stands develop into Abies dominated stands due to the rapid growth of Abies saplings in open habitats. The stands usually include well -growing saplings of Tsuga. Because of Tsuga's greater longevity it gradually succeeds the Abies dominated stands. 2. Open-area type : Exogenous agencies to forests, such as typhoons, forest fires and clear cutting result in large open areas. In the open areas with least damaged soil, Betula ermanii and other deciduous trees invade and grow rapidly, so deciduous forests develop. Eventually, deciduous forests are dominated by Betula ermanii. But, saplings of Abies and Tsuga are well represented in the subtree and shrub layers, respectively. The deciduous forests are then replaced by Abies forests and Tsuga forests successively. 3. Wave type : Wave type forest regeneration occurs in Abies dominated forests only on south facing slopes on the upper parts of mountains. The wave results from the sequential arrangement of different aged Abies and creates a gradient developmental stages. It moves upwards at the speed of 1.0 to l.3m/year. The successive regeneration of the Abies forests is thought to be caused by prevailing winds and shallow soil conditions. 4. Nursery-log type: In coniferous forests with undergrowths of dwarf-bamboo, regen-eration of tree species is restricted to decaying logs, as it is hard for seedlings of tree species to settle and grow under dwarf-bamboo cover. As a result, the forests have low densities of both mature trees and juveniles, compared with other forest communities in the subalpine region. Many seedlings are observed in bryophyte communities on decaying logs, and some of them steadily grow up. 5. Sprout type : Most tree species in subalpine region produce sprouts. Active production is observed when trees are injured by storm-winds, snowslides etc. Betula dominated stands located close to the forest-line at higher elevations frequently produce sprouts, and regeneration of these stands seems to be accomplished by sprouts.
  • 叶内 敦子
    1991 年 07 巻 p. 15-23
    発行日: 1991年
    公開日: 2021/07/28
    ジャーナル オープンアクセス
    Many bogs distributed in the mountains of Japan are characterized by their own vegetation. They are usually high-moors built up only by rain fall, and were formed by climatic changes during the Last Glacial Age. In this paper, climatic change was considered the key to the manner of the formation of montane bog, it was studied using borings and pollen analysis. Study areas were from the northern part of the Kanto district to the southern part of the Tohoku district, where many montane bogs are distributed. These bogs were formed in two short periods. One was after the Holocene warm period, namely hypsithermal, and the other was from the Last Glacial Age to the Holocene. The origin of some bogs was not lakes or ponds but the over-humidization of the ground. These bogs were formed when the climate became relatively more humid. The humidization at that time was caused by an increase in snowfall and also by changes in seasonal rainfall patterns.
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