摘要:

In this study, I defined a gap as a small opening formed in a forest canopy (area < 0.1 ha) and tried to synthesize gap-disturbance regimes of primary mature stands in different forest types of Japan, such as warm temperate evergreen broad-leaved (4 stands in 3 localities), cool temperate deciduous broad-leaved (10 in 5) and subalpine evergreen coniferous (3 in 1) forests. Mean percentage of the total gap area within the total forested area (percentage gap area) in each forest type was 17.0% in warm temperate (number of surveyed gaps was 161), 13.8% in cool temperate (278 gaps), and 8.0% in subalpine (100 gaps) forests. Mean gap density (ha-1) and mean gap size (m2) were 19.5 and 77.1 in warm temperate, 16.4 and 92.0 in cool temperate, and 19.1 and 41.9 in subalpine forests, respectively. These figures indicate that gap density is not substantially different among the forest types, but the mean gap size of subalpine forests is smaller than the other two, resulting in lower percentage gap area of this forest type. The gap size distributions were similar among the forest types; smaller gaps were much more frequent than larger ones, and gaps > 400 rrr were rare in warm temperate and cool temperate forests. In subalpine forests gaps > 200 m2were rare. Gaps formed by multiple gapmakers comprised 19.9% of all gaps in warm temperate, 9.9% in cool temperate, and 44.9% in subalpine forests, which implies that gap formation by simultaneous tree fall or gap enlargement is more frequent in subalpine forests. Canopy trees died less often by uprooting in every forest type; dominant mode for the death of canopy trees was by leaving standing-dead or with broken trunks in every forest type. Since typhoons are obviously a chief agent of forest disturbance in Japan, frequency or magnitude of typhoon disturbance may influence these differences in the gap-disturbance regimes. In addition to the disturbance, tree architectures seem to affect some of these differences; narrower crown size of conifers compared with broad-leaved trees is considered one major cause for smaller gap size of the conifer forest.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_01

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Processes and mechanisms of large-gap creation in an old-growth beech forest on Mt. Garyu in southwestern Japan by Typhoon 9119 are discussed. In the large gap of 4,100 m2, damaged trees were mostlyFagus crenataand the main cause of gap creation was uprooting of tall, large diameter, canopy trees. Also in the other parts of the beech forest, the main cause of gap creation was uprooting of canopy trees. The large gap was created by the sequential and domino-like fall of multiple canopy trees blown down by windstorms that followed the passage of the typhoon itself. In the large gap, it is possible that the windstorm which attacked and moved over the slope was strengthened by topography. In addition, the risk of gap enlargement will increase on steep slopes more than on gentle slopes when the up-slope is on the leeward of the wind. The large-scale disturbance caused by Typhoon 9119 as a catastrophic windstorm may influence the pattern and process in forest regeneration.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_02

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Magnolia obovataThunb. is generally scattered through the forest in small patches, but occasionally forms large patches. The size and age distributions and spatial dispersions ofM. obovataindividuals are investigated in the large patches belonging to different developmental stages. The results of field investigations suggest that: (1) most seedlings appear quickly and simultaneously from buried seeds under the original positions of the crown of fallen trees, and sprouts from stumps begin to grow when disturbances occur; (2) more than 60% of seedlings and sprouts die before the young stage; and (3) the individuals form a patch if such events repeat. A Monte Carlo simulation model is constructed for understanding the relationships between disturbance replication and the probability of large patch formation quantitatively. The model implies that more than four disturbance replications are necessary for forming large patches of canopyM. obovatatrees, and the sprouting ability from the stump has the role of maintaining the probability of patch formation when the conditions are unfavorable to its formation. The structures of patches ofM. obovataare affected by the proportion of patch formation strategies, and the strategies are strongly related to disturbance regimes.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_03

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The relationship between stand dynamics and the local wind climate was analyzed in two natural beech(Fagusspp.) forests in Takahara and Kayanodaira, Japan. The stand dynamics of the most recent 100 years were analyzed using tree-ring chronologies. An index for growth-rate increase(GI)was calculated. Site specific curves of annual averages ofGIfor all sample trees(GIA-curves) were compared. Peaks in theGIA-curves coincided with typhoons which hit the region and may have caused major releases. Takahara had higher peaks in the GA4-curve and an average higher level of the curve, which suggested that the site was more dynamic and experienced more and stronger releases. The local wind climate was analyzed using data from nearby meteorological stations. The wind climate near the more dynamic Takahara had higher extremes in daily maximum wind speeds. In this way, the wind climate data support the interpretation of stand dynamics from tree-ring chronologies.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_04

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A disturbance to a stand is often part of larger event which impacts a large landscape area. Across a landscape, a disturbance event leaves a mosaic of” conditions. The event can miss some Stands, kill all trees in other stands, and kill only some trees in other stands. Stands regrow through certain processes and create certain structures after a disturbance; time at which each structure is achieved varies with specific stand and disturbance conditions. Each structure is utilized by certain plant and animal species, but not others. A disturbance leaves many openings across the landscape and allows species which utilize these openings to expand their populations. At the same time, “closed forest” species become extirpated or confined to isolated “refugia” missed by the disturbance. With regrowth the “open” species become confined to small, isolated “refugia” and the closed forest species increase in number. Landscape areas have probably always had various fluctuations in plant and animal populations.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_05

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In 250 20 m X 20 m permanent plots in the Craigie-burn Range, Canterbury, New Zealand, 1970 stem density was 2,191/ha, basal area was 52.4 m2/ha, and stem biomass was 178.1 Mg/ha. Net production of stemwood (1974-1987) was 2.0 Mg/ha/yr; mortality was 3.5 Mg/ha/yr. By 1987 density had decreased by 30%, basal area by 12%, and stem biomass by 13%.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_06

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Structural changes over time in forests of shade-tolerant species are difficult to study because these stands are often broadly uneven-aged and not suitable for traditional chronosequence analysis. Yet because of past disturbances of variable intensity and frequency, there is often substantial structural variation among stands of a given site quality class. In this study, diameter distributions from 70 primary northern hardwood stands were analyzed to determine if certain structural indices might allow placement of stands in a developmental sequence.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_07

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In 1954,Picea-Abiesforests of central Hokkaido were leveled by a windstorm caused by a typhoon. Successional dynamics following disturbance on several forest habitats were monitored over a thirty-four year period. Differences in site conditions, such as soil, topography, and forest floor vegetation, influenced the direction of succession, but some patterns prevailing in this area were discernible. In the early stage of succession (up to year 10), all sites were immediately occupied byRubus idaeusvar.aculeatissi-muswhich was an inconspicuous component of the stands before disturbance. Plants which dominated the understory of stands before disturbance mostly disappeared during secondary succession except forSasa senanensis.Residual conifers also survived except for those at a moss-floor site.Betulaspp. andSalixspp. invaded within 6-8 years. At year 10-18,R. idaeussuddenly decreased in canopy cover, whileS. senanensisreplacedR. idaeusas the dominant component. Trees, both residuals and invaders, were successful in growing over the shrub layer during this period and species diversity reached a peak. These observations suggest that the timing of tree establishment occurs during the transition fromR. idaeuscommunity toS. senanensiscommunity in the shrub-layer, as a deterministic process founded in the life history traits of species.

ISSN:1054-9811    

DOI:10.1300/J091v06n03_08

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor