Tsuga chinensis

Chinese hemlock
Conservation status
Least Concern(IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Pinaceae
Genus:	Tsuga
Species:	T. chinensis
Binomial name
Tsuga chinensis (Franch.) Pritzel exDiels.

Tsuga chinensis,commonly referred to as theTaiwanorChinese hemlock,is aconiferoustree species native to China, Taiwan, and Vietnam. The tree is quite variable and has many recognised varieties, though some are also maintained to be separate species by certain authorities. The tree was recently discovered in the mountains of northern Vietnam, making that the southernmost extension of its range.

Description

Tsuga chinensisis a large tree withbarkthat is a blackish brown in colour. The scaly bark has irregular longitudinal breaks, andlenticelsthat are very inconspicuous. The outer bark is about 6 mm thick with alternating tiered layers of pale yellowish brown corky bark, and brown lignified fibrous bark. The newly formedperidermis a purplish red. The inner bark is about 4 to 5 mm (0.16 to 0.20 inches) thick and pale reddish brown in colour. It is fibrous in texture with minute, almost inconspicuous sclereid, or stone cell groups. Thecambiumas well as the newly formedphloemare nearly inconspicuous. Freshly cut wood is a pale yellowish white with inconspicuous wood rays.

Thebranchletsthat have leaf-cushions. Theleavesare arranged spirally in a manner more or less 2-ranked. They are linear and flat in shape and olive green in colour. The upper side of the leaf is grooved and keeled, while the underside has 2 whitestomaticbands. The apex of the leaves are emerginate and they measure 16 to 20 mm (0.63 to 0.79 inches) long. Thepetiolesare crooked. The foliage is very similar to that ofT. heterophylla,butT. chinensishas nodding shoots and the stomatic bands are paler and more sparse. Also the colour above is a paler yellowish-green.The stamenateflowersappear singly on one-year-old shoots, or in groups of 1 to 5 on two-year-old shoots. They are a dull purple in colour and measure about 8 mm (0.31 inches). The pistillate flowers are terminal on a very short shoot. They nod, are rosy-purple and are about 6 mm (0.24 inches) in length. The mature cones are green, later turning to red-brown, long-ovoid in shape and measure 2 to 2.5 mm (0.079 to 0.098 inches) long by about 1 cm (0.39 inches) wide. They are pendulous and the cone scales are large and suborbicular with longitudinal streaks. Thebractsare small and 2 lobed at the apex. The seeds are winged and measure about 7 mm (0.28 inches) long with the wing included.

Range and habitat

T. chinensisis found in Taiwan, China (fromTibetto southernShanxiprovince andGuangdongprovince), and northernHa Giangprovince in Vietnam. In the very south of their range they are only found high in the mountains. For example, in Vietnam the tree is only found in mountains 1,300 to 1,700 m (4,300 to 5,600 feet) above sea level.In China it is present at altitudes of 1,000 to 3,500 m (3,300 to 11,500 feet) in the following provinces:Anhui,Fujian,southernGansu,Guangdong,Guangxi,northernGuizhou,westernHenan,westernHubei,Hunan,Jiangxi,southernShaanxi,Sichuan,Xizang,Yunnan,andZhejiang.This comprises the southern half of the country with a few population farther north. It is found primarily in mixed forests near river basins and in mountains and valleys.In Taiwan it is found mainly inNantou CountyandTaoyuan Cityat heights of 1,700 to 3,500 m (5,600 to 11,500 feet) in mixed broadleaf forests. It can be found in Taiwans'sYushan National Parkand Lalashan Preserve, as well as in China'sHailuogouGlacier Park inSichuanprovince.

Taxonomy

There are a number of varieties ofT. chinensis,though there is much dispute over which are valid and whether some constitute distinct species or not. All in all there are six varieties, though not all are accepted universally. These are:

• T. c.var.chinensisis the type variety and occurs across most of the range inmainland ChinaandTibet.Its seed scales are pentagonal-ovate, subsquare, or suborbicular, while its branchlets are 1 mm (0.039 inches) in diameter and grey to yellow-grey in colour. The cones are ovoid and 1.5 to 2.5 cm (0.59 to 0.98 inches) tall by 1.2 to 1.6 cm (0.47 to 0.63 inches) wide.
• T. c.var.formosanais the variety that occurs exclusively inTaiwan.Aljos Farjon, a conifer expert from theRoyal Botanic GardensatKew,considers this variety identical with the type, but according to Raven and Wu it differs from the type by having seed scales which are compressed orbicular to nearly semiorbicular. Otherwise, however, it is like the type.
• T. c.var.patensis found only in westernHubeiprovince on Changyang Xian. It differs in having brownish yellow to brown branchlets, which are between to 0.5 to 1 mm (0.020 to 0.039 inches) longer in diameter than the type. The seed cones also differ in being slightly larger, ovoid-globose in shape, and with seed scales that are smooth, shiny and almost square. This variety is recognized by Raven and Wu.
• T. c.var.forrestiiis treated as a separate species, namelyTsuga forrestii,by some authorities. The cones are larger, more slender and narrow-ovoid to ovoid-cylindric. The branchlets are slightly thicker, while the seed scales are narrowly ovate or oblong with the exposed part striate and glabrous with a thickened margin. Regardless of its taxonomic status, it is considered threatened by theIUCN.It occurs only in northeastGuizhou,southwestSichuanand northwestYunnan.
• T. c.var.robustais probably the most universally recognised of the varieties. It is present in westernHubeiand westernSichuan.It again exhibits the thicker branchlets and larger cones, but the cones are stout and shortly cylindric. Also, the seed scales are square-orbicular with the exposed part being pubescent and the margin not thickened. In addition, thebractsare cuspidate at the apex.
• T. c.var.oblongisquamatais considered a separate species by Raven and Wu, namelyT. oblongisquamata,but as a variety by Farjon. It occurs in the northern part of the range, namely in southernGansu,western Hubei and northwest Sichuan. It differs most sharply in lacking visiblestomaticbands beneath the leaves. Otherwise the seed scales are more loosely arranged and loosely elliptic in shape, being nearly twice as long as they are wide.

Uses

The timber obtained fromT. chinensisis used in construction,furnituremaking, and as a support inmines.The bark is high intannins,which is often extracted and used as adye.Thetrunkis used as a source ofresin.In addition, the roots, trunk, and branches are all used in the production of aromatic oils due to their pleasing scent.