铁杉 tieshan [Chinese] (Wu and Raven (1999).
Tsuga chinensis is the nexus of a Chinese hemlock species complex that has not yet been satisfactorily resolved by either morphological or molecular means, as shown by the lack of consensus between recent authorities who have addressed the problem. The list of players is reasonably clear, though:
The most detailed molecular analysis of Tsuga to date, by Havill et al. (2008), supports the hypothesis that T. formosana is a good species; their analysis placed it as sister to T. dumosa, a distinctive species of western China, and instead found that T. chinensis shares a clade with the southern Japanese hemlock T. sieboldii. The same analysis supported a close relationship between T. forrestii and T. chinensis, and did not support a hypothesis that T. forrestii may have arisen by hybridization between T. chinensis and T. dumosa. The molecular analysis did not attempt to elucidate the status of T. chinensis varieties oblongisquamata and robusta.
Based on the above, I have chosen to demarcate the Chinese hemlock species complex as follows:
The interested reader is referred to Wu and Raven (1999) for online information that includes a key to the taxa named above.
Trees to 50 m tall and 200 cm DBH, usually with a single trunk, often forked in the crown. Bark rough, scaly, comprised of blackish brown plates, with irregular longitudinal fissures; lenticels inconspicuous; outer bark about 6 mm thick, with alternate tiered layers of pale yellowish brown corky layers and brown lignified fibrous layers; newly formed periderm purplish red; inner bark about 4-5 mm thick, pale reddish brown, fibrous; cambium and newly formed phloem almost inconspicuous. Freshly cut sapwood pale yellowish white, wood rays inconspicuous. Crown broad, becoming irregular or flat-topped with age. Twigs pale yellow-brown, finely grooved between decurrent pulvini; minute pubescence in grooves, soon glabrous. Buds ovoid-globose, 1-4 mm diameter, not resinous, dark or red-brown. Leaves mostly pectinate, 10-20×1.8-3 mm, linear, flattened, grooved above; a midrib separates two stomatal bands below; apex emarginate. Pollen cones crowded near ends of branches, 3-5 mm long, yellow with purple tinge. Seed cones numerous, short-pedunculate, ovoid-oblong when closed, 15-40×10-22 mm, light green ripening light brown. Seed scales nearly circular, 10 mm diameter, lower surface striated. Bracts rhombic with denticulate upper margin, 1-2 mm long. Seeds ovoid-oblong, 3-4×2 mm, light brown, with 6-7×3.5 mm transparent wings (Liu 1970, Farjon 2010).
Var. chinensis differs in that the seed cones are only 15-25×13-22 mm and the cone scale base is short-pedicellate (Farjon 2010).
Var. oblongisquamata differs in that the seed cones are 18-28×10-15 mm and the cone scale base is distinctly petiolate (Farjon 2010).
Var. robusta differs in that the seed cones are up to 40 mm long and the cone scales are proportionally robust and thick (Farjon 2010).
Var. tchekiangensis differs in that the twigs are stout (up to 2 mm thick) and reddish-brown rather than pale yellow-brown (Debreczy and Racz 2011).
The species as a whole is found in Tibet; China (Anhui, Fujian, S Gansu, Guangdong, Guangxi, N Guizhou, W Henan, W Hubei, Hunan, Jiangxi, S Shaanxi, Sichuan, Taiwan, Xizang, Yunnan, and Zhejiang); and northern Vietnam. It occurs at elevations of 600 to 3500 m in a wide variety of mixed forests (Wu and Raven 1999, Debreczy and Racz 2011), and dominates a widespread forest altitudinal belt in the mountains of SW China at 2200-2700 m (Liu 1971).
Var. chinensis has the same general range, except that it is not reported for Vietnam. It occurs on varied soils, in a cool temperate climate with 1000-2000 mm of annual precipitation (Farjon 2010).
Var. oblongisquamata has similar ecological tolerances, but is limited to Zhouqu Xian in Gansu, W Hubei, and Sichuan (Farjon 2010).
Var. robusta also has similar ecological tolerances, but is limited to Hubei and the Yalong Valley in Sichuan (Farjon 2010).
Var. tchekiangensis occurs at 600-2100 m elevation in SE Yunnan, Guizhou, Hunan, Jiangxi, Zhejiang, N Guangxi, and northern Vietnam. It mainly occurs on karst limestone soils, often in evergreen forest with Amentotaxus yunnanensis, Pinus wangii, and Taxus; also with evergreen species of Quercus (Debreczy and Racz 2011).
T. chinensis is described as hardy to Zone 6 (cold hardiness limit between -23.2°C and -17.8°C) (Bannister and Neuner 2001), though that likely depends upon its provenance.
Often attains a diameter of 200 cm (Liu 1971).
Age often exceeds 400 years (Liu 1971).
I took some exploratory cores from the Hailuogou Glacier Park in Sichuan. The species has seen some limited application in stable carbon isotope studies (Leavitt et al. 1995) and a study of climate variation (Wu 1995).
I have seen it at Hailuogou Glacier Park in Sichuan.
The epithet chinensis refers to China.
This species is extraordinarily resistant to hemlock woolly adelgid, an introduced pest that is currently ravaging T. canadensis throughout most of its native range. In an effort to acquire a genetically diverse record and investigate this resistance, collections were made throughout the range of T. chinensis in 1994-1996 and this material was brought to the United States for further study. Growing with native T. canadensis, the species shows comparable growth rates and comparable phenology, with growth both beginning and ending about two weeks earlier in the year, compared to T. canadansis.
del Tredici, Peter. 2010. Chinese hemlock Tsuga chinensis. Arnoldia 68(2):65-67. Available, accessed 2016.02.14.
Havill, Nathan P., Christopher S. Campbell, Thomas F. Vining, Ben LePage, Randall J. Bayer, and Michael J. Donoghue. 2008. Phylogeny and biogeography of Tsuga (Pinaceae) inferred from nuclear ribosomal ITS and chloroplast DNA sequence data. Systematic Botany 33(3):478–489.
Leavitt, S.W., Malcolm K. Hughes, Liu Y. and An Z. 1995. Stable-carbon isotope tree-ring chronologies from Xian, China. In S. Ohta, T. Fujii, N. Okada, M.K. Hughes and D. Eckstein, eds., Tree Rings: From the Past to the Future. Proceedings of the International Workshop on Asian and Pacific Dendrochronology. Forestry and Forest Products Research Institute Scientific Meeting Report 1: 182-186.
Wu Xiangding. 1995. Tree-ring width chronologies and their response to climate in the Qinling Mountains, China. In Sheu D.D., R.S. Bradley and Wang W.-C., eds., High Resolution Records of Past Climate from Monsoon Asia: The Last 2000 Years and Beyond. Terrestrial, Atmospheric and Oceanic Sciences 5(3): 365-372.
Luu and Thomas 2004 provide a description, range map, conservation status, drawings and photos, and a wealth of additional information.
Last Modified 2016-02-15