|Abstract or Summary
- 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
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.