Chamaecyparis obtusa var obtusa (Siebold & Zucc.) Endl.
This species has two varieties that occur in Japan (var. obtusa) and Taiwan (var. formosana). Throughout its range it has been heavily exploited in the past for its valuable durable timber.
Description
Taxonomic notes
The Taiwanese variety is sometimes recognised as a distinct species: C. taiwanensis Masam & S.Suzuki. Biogeographic and phylogenetic studies do not support its distinction (Little 2004; Wang et al. 2003).
Distribution
In Japan, the natural populations of the typical variety occur in southern Honshu, Shikoku and Kyushu with the most northern population in Fukushima Prefecture and the most southern on Yakushima Island. Its altitudinal range is from 100m to 2200m above sea level. Natrual forests range in size from less than one hectare to approximately 2000 hectares. Genetic studies indicate that there have been genetic bottlenecks in the past and that there has been some loss of diversity due to fragmentation and overexploitation (Matsumoto et al. 2010). Artifical plantations of this variety make up almost 10% of the total forest area in Japan.
The Taiwanese variety has a smaller distribution and is restricted to montane areas in north and central Taiwan at altitudes ranging from 1800m to 3000m above sea level.
Habitat and Ecology
The two varieties of this species occur in different microhabitats: C. obtusa var. obtusa is generally occupying more xeric sites on ridges or slopes; C. obtusa var. formosana
can form extensive forests in atmospherically damp and often edaphically wet sites. Both occur in mixed conifer/angioserm forests, in which the conifers are mostly emergents and the angiosperms form lower layers of canopy.
Human Uses
The wood of Chamaecyparis obtusa has been used for centuries in construction of temples and other traditional buildings because of its fine quality and high durability in outdoor conditions. The Japanese have largely turned to sources outside Japan to obtain timber of related species, especially those occurring on the Pacific coast of North America. This species is among the most widely used in horticulture and numerous cultivars are in the trade
Conservation Status
Global Status & Rationale
Near Threatened
The individual varieties of Chamaecyparis obtusa's have been assessed as Near Threatened in Japan (var. obtusa) and Vulnerable in Taiwan (var. formosana). The Japanese variety is the more widespread and numerous so the species as a whole is also assessed as Near Threatened, on the basis of a population decline which may approach 30%.
Global Threats
The overall conservation status of the species is determined by that of its main variety in Japan. Uncertainty about the extent and timing of its past exploitation in Japan has resulted in an assessment of Near Threatened. The Taiwanese variety is currently assessed as Vulnerable as there is more certainty about past exploitation .
Conservation Actions
In both Japan and Taiwan the remaining old growth and natural forests are protected from logging and many are in nature reserves or national parks
Little, D. (2004) The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). American Journal of Botany 91(11):1872-1881.
Matsumoto, A., K. Uchida, Y. Taguchi, N. Tani & Y. Tsumura (2010) Genetic diversity and structure of natural fragmented Chamaecyparis obtusa populations as revealed by microsatellite markers. Journal of Plant Research 123(5):689-699.
Wang, W.P., C.Y. Hwang, T.P. Lin, S.Y. Hwang (2003) Historical biogeography and phylogenetic relationships of the genus Chamaecyparis (Cupressaceae) inferred from chloroplast DNA polymorphism. Plant Systematics and Evolution 241:13-28.
Yamamoto, S.I. 1998. Regeneration ecology of Chamaecyparis obtusa and C. pisifera (Hinoki and Sawara Cypress), Japan. In: A.D. Ladermann (ed.), Coastally restricted forests, Oxford University Press, Oxford, New York.
