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A comparative study of temperate Chamaecyparis forests Public Deposited

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  • The objectives of this study include: (1) analysis of Chamaecyparis lawsoniana, C. taiwanensis, and C. formosensis forests including the structure, composition, and dynamics of plant communities and their environmental relationships; and (2) comparison of the temperate Chamaecyparis forests of Taiwan and the Pacific Northwest with emphasis on structural and successional characteristics. One vegetation zone with four communities in Taiwan and three zones with eight communities in the Pacific Northwest are described. All communities are defined on the basis of their vegetative differences which arise primarily in response to changes in climate and/or soils. The Chamaecyparis communities show varying degrees of site specificity. The two Taiwan species are sympatric over most of their ranges. Chamaecyparis taiwanensis occurs on high elevation, well drained landforms and on many aspects. The soils are typically podzolized or undifferentiated. Most vigorous forests tend to be in northwestern portions of the generic range. Chamaecyparis formosensis is found at lower elevations, on less well drained and more commonly podzolized soils, and is more restricted to north and northwestern aspects. The most vigorous stands are in the southeastern portion of Its range. Climatic variation is more pronounced in the Pacific Northwest, and Chamaecyparis lawsoniana communities reflect this. In the north, middle and low elevations are occupied by the Tsuga heterophylla-Chamaecyparis lawsoniana/Polystichum munitum-Oxalis oregana community on more mesic areas and by the Tsuga heterophyIh-Chamaecyparls lawsoniana/Rhododendron macrophyllum-Gaultheria shallon community on better drained sites. Both communities occur on sedimentary parent materials within the Tsuga heterophylla Zone. On ultramafic parent material in this zone the Chamaecyparis lawsoniana-Tsuga heterophylla/Xerophyllum tenax community occurs. South and east of the range of Tsuga heterophylla, mixed soils support the Chamaecyparis lawsoniana/Lithocarpus densiflora community as a closed forest, while pure ultramafic substrates are occupied by the open Pinus-Chamaecyparis lawsoniana/Quercus vaccinifolia/Xerophyllum tenax community (both in the Mixed EvergreenZone). At the transition of the Tsuga heterophylla and Abies concolor Zones is the Abies concolor- Tsuga heterophylla-Chamaecyparis lawsoniana community, the lower member of the Abies concolor Zone. South and inland from this transition area and at higher elevations, are the other Abies concolor Zone communities, Abies concolor-Chamaecyparis lawsoniana/herb and mixed Abies-Chamaecyparis lawsoniana/herb. The first of these occurs on mixed soils which include some ultramafics, while the second is primarily on granitic parent materials. Chamaecyparis taiwanensis reproduces well in mature forests, although with much less success in the bamboo community than in the shrub community. Chamaecyparis formosensis reproduces poorly in all mature forests. Hardwoods and bamboo are strong competitors with Chamaecyparis formosensis, which is also less shade tolerant than Chamaecyparis taiwanensis. Chamaecyparis lawsoniana reproduces better than either Taiwan species, in all zones, and in all communities studied. Chamaecyparis lawsoniana density in most size classes is significantly different among communities. Chamaecyparis lawsoniana appears to be relatively better adapted to sub-mesic sites on mixed ultramafic soils than to more mesic sites on other substrates. Chamaecyparis taiwanensis and C. formosensis are interpreted as being quasi-climax species which persist because of their longevity and ability to colonize disturbed areas. Chamaecyparis lawsoniana is interpreted as being a climax species in mesic communities on sedimentary and granitic substrates along with Tsuga heterophylla or Abies concolor, and as a climax dominant on ultramafic substrates where other tree species are relatively more inhibited than Chamaecyparis lawsoniana.
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