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Scientific name: Cupressus gigantea W.C.Cheng & L.K.Fu 1975
Synonyms: Cupressus flagelliformis Knight, Cupressus torulosa var. gigantea (W.C.Cheng & L.K.Fu) Farjon
Common names: Tsangpo cypress, Tsangpo River cypress, Tibetan cypress (English), Ju bai (Chinese)
Tree to 45 m tall, with trunk to 3(-6) m in diameter. Bark bright reddish brown to grayish brown, fibrous, peeling in long thin strips to form furrows and ridges. Crown dense, conical, with short horizontal branches, flattening and thinning with age. Branchlets roundly four-angled, (1-)1.5-2 mm in diameter, branching from all four rows of leaves. Scale leaves on branchlets about 1 mm long, dark green or often bluish green with wax, the back often with an inconspicuous, inactive gland. Pollen cones 3-6(-8) mm long, about 2.5 mm wide, with (4-)6-8(-10) pairs of pollen scales, each scale with three to five pollen sacs. Seed cones slightly oblong, 1.5-2 cm long, dark brown with a grayish waxy coating, usually with six pairs of seed scales, each with a well-developed central, conical point on the face, the surface otherwise warty. Seeds four to eight per scale, 4-6 mm long, light brown, the wings very narrow. Cotyledons two.
This was previously treated as a variety of Cupressus torulosa, but is now considered to be a good species. The morphological differences between both species are small. Cupressus gigantea has thicker (1.5-2 mm) ultimate branchlets with closely appressed, rhombic-gibbous leaves. Tree size is a very doubtful taxonomic character and pollen and seed cones of both taxa are similar. It is possible that Cupressus gigantea is merely a xeromorphic variant of Cupressus torulosa.
Tsangpo cypress earns its scientific name gigantea as one of the tallest species in the genus as well as the largest tree of the arid valleys of the Tibetan Plateau.
Southeastern Xizang (Tibet), along the Brahmaputra (Yarlung Zangbo) River and its tributaries. Forming groves of large trees in a general matrix of shrubby vegetation along streamsides and on gentle slopes; 3,000-3,400(-3,650) m.
Red List Category & Criteria: Vulnerable
The historic loss of up to 50% of mature individuals in the last three generations (60 to 115 years) places this taxon in the Vulnerable category under criterion A.
Wang et al. (2010) surveyed 13 quadrants within the area 28 59’ 22” to 28 59’ 49” N and 93 16’ 52” – 93 18’ 57” E (3,120 m to 3,210 m a.s.l.) each covering an area of 1 km² which between them contained ca 366 mature individuals. Regeneration throughout this area was poor. In one location, near Linzhi, an estimated 300-500 mature individuals were directly observed in 2007 but with no regeneration. The species is common along the Yarlung Tsangpo valley from Nang for about 30-40 km with more scattered trees at higher elevations along the same stretch. An estimated 2000 mature individuals occur in this area, and “copious regeneration” has been observed. It is estimated that the number of mature individuals throughout the range do not total more than 5000 trees. Since 1998 the extant population of mature individuals is believed to have stabilized.
This species is found in scattered stands or groves, with few other large shrubs, surrounded by open dry scrubland; usually on east-facing slopes, often seasonally grazed. It occurs in sandy or stony fluvio-glacial sediments or on slopes over limestone. The climate is seasonal (east monsoon, dry winds from the Tibetan Plateau in the west), with cold winters and with an annual precipitation of less than 500 mm; rainfall is from June-September.
Due to the scarcity of timber in the region there is continuous pressure for exploitation. Regeneration is often poor due to grazing of livestock. Extensive logging (estimated at around 50% of mature individuals) took place between the 1960s and 1980s. Wang et al. (2010) found regeneration to be poor throughout their entire study area, and further direct observations support this for the area around Linzhi. A decline in the quality of habitat around Linzhi has been observed, and is a result of deforestation and subsequent soil erosion.
Timber and firewood are locally taken. Large trees are often venerated in local traditions and religion.
Several groves are protected as 'sacred forest' by Buddhist monks and some of the largest trees are on grounds used as a cemetery, where any cutting is prohibited. Other locations have also been designated as a National Park and protected by local government. The taxon is cultivated in botanic gardens both within China and in the UK where conservation collections of known wild origin are maintained.
Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.
