Tsuga Forest Research Articles

The Development of Momi and Tsuga Forest : The Influence of Broad-leaved Trees on the Growth of Two dominant Conifers, Momi and Tsuga Trees

The influence of broad-leaved trees on the growth of two conifers, Momi arid Tsuga trees was explained by the changes of individual ranking, including that of broad-leaved trees, from an early stage in the development of the community. 1) Judging from the age structure, it was considered that Momi and Tsuga trees, and broadleaved trees on the surveyed plots had developed in gaps or openings in the forest. 2) Momi and Tsuga individuals established earlier in gaps or openings in the forest were superior to broad-leaved trees in competition from an early time in the development of the community and became stable in a superior position. 3) 011 the other hand, most of the Momi and Tsuga trees established later stagnate in a subordinate position as a result of oppression from the upper trees. This phenomenon indicated that the occurrence period, i, e., the time of establishment, affected the growth of individuals. 4) Momi and Tsuga individuals were ranked in three classes-superior, medium and subordinate in a Momi and Tsuga forest, but when broad-leaved trees outnumbered Momi and Tsuga trees, those of the latter in the medium class were few. 5) Broad-leaved trees CO-existing with Momi and Tsuga trees were composed of a large number of middle-sized and small trees, and a small number of large trees. It was considered that the paucity of large broad.leaved trees also prolnoted the superiority of Momi and Tsuga trees in a natural forest.

The Development of Momi and Tsuga Forests on the Basis of Diameter Growth

The Development of Momi and Tsuga Forests on the Basis of Diameter Growth

Forest succession in the subalpine region of Mt. Fuji, Japan

Subalpine forest succession was studied on Mt. Fuji, Japan, where various types of forests in different successional phases occur owing to volcanic action. Ninety stands were subjected to ordination using an index (SI) defined by the relative basal area and the life span of component woody species, and the cover of canopy layer of the sample stands. Two different sequences of sample stands were found. One was from deciduous scrubs, through Larix kaempferi forests and Abies forests, to Tsuga diversifolia forests, and the other from Abies-Tsuga thickets to Abies forests. Through analyses of the forest structure and composition, soil survey and identification of fallen logs, the former sequence was recognized as the primary sere and the latter as a regeneration sere following gap formation. During forest succession, basal area reached a maximum in the seral phase with a multi-layered structure. The Tsuga forests, whose understory is restricted to a moss layer, were regarded as the climax. The death or fall of Tsuga stems resulted in gaps, which were subsequently occupied by Abies-Tsuga thickets. The second Abies forests were distinguished from the ones in the primary sere by the occurrence of Dryopteris and Cacalia and the lack of Rhododendron in the understorey. Both Abies forest types included Tsuga saplings. Thus, a cyclic relation is supposed between Abies and Tsuga.

Dynamics of Understory Biomass in Sitka Spruce-Western Hemlock Forests of Southeast Alaska

Understory vegetation undergoes successional stages during the 1st 300 yr after logging or fire disturbance in the coastal Picea—Tsuga forests of southeast Alaska. Residual shrubs and tree seedlings increase their growth within 5 yr after overstory removal. Understory biomass peaks at 5 Mg°ha — 1 °yr — 1 °15—25 yr after logging. Shrubs and herbs are virtually eliminated (<0.1 Mg/ha) from the understory after forest canopies close at stand ages of 25—35 yr. Bryophytes and ferns dominate understory biomass during the following century. An understory of deciduous shrubs and herbs is reestablished after 140—160 yr. Thereafter, biomass of the shrubs, herbs, and ferns continues to increase, while bryophyte biomass and tree productivity decline. Departures from this developmental sequence are related to unusual types of stand establishment, soil, microclimate, or disturbance. The development and duration of the depauperate understory that succeeds canopy closure in southeast Alaska is closely related to the canopy structure of shade—tolerant Tsuga forests with their high foliar biomass. In young—growth forests (<100 yr), the decline in understory development immediately after canopy closure is significantly associated with tree basal area and percentage of tree canopy cover. In old—growth forests, in contrast, understory biomass is correlated with mean tree diameter, age, and volume. It is hypothesized that understory development over the chronosequence responds primarily to changes induced in the light environment by developments in the forest canopy. Maintenance of the most productive forests in the aggradation stages of development (0—100 yr) through forest management will minimize the development of a productive vascular understory and thus deprive herbivores of forage during 70—80% of the forest rotation.