Tibetan juniper, 大果圆柏 da guo yuan bai [Chinese].
Synonymy (Adams 2008):
Type: Tibet, Jinsha River, in forest near temple, V. F. Ladygin 25 (holotype SBT, isotype PE). The cladistic analysis by Mao et al. (2010) placed J. tibetica in a clade sister to 8 other morphologically similar central Asian junipers: J. convallium, J. indica, J. komarovii, J. pingii, J. przewalskii, J. recurva var. coxii, J. saltuaria, and J. squamata.
Dioecious or monoecious shrubs or trees to 30 m tall. Bark brown, exfoliating in longitudinal strips. Twigs mostly straight, round to 4-angled, 1-2 mm diameter. Leaves both whip-like and scale-like. Whip leaves in whorls of 3, 4-8 mm long, only found on young plants. Scale leaves in whorls of 3 or 4, ovate-rhombic, obtuse, 1-3 mm long, with a central, conspicuous, slightly depressed, linear-elliptic gland. Seed cones erect, maturing brown-black in 2 years, turbinate, 9-16 × 7-13 mm, each bearing 1 ovoid seed, 7-11 × 6-8 mm, bearing deep resin pits. Pollen shed in March to April (Adams 2008).
China: S Gansu, SE Qinghai, Sichuan, S and E Xizang (Tibet). Climate continental; grows at elevations of 2600 to 4900 m on rocky and gravelly (both siliceous and calcareous) soils, on mountain slopes or in valleys. Often grows with J. convallium in yak-grazed woodlands with Cyperaceae mats, Berberis scrub, or Artemisia steppe. At relatively low elevations it also occurs in south-facing clearings in Picea forests, and at the highest elevations it is also restricted to south aspects. Locally, occurs in groves of Cupressus gigantea. (Adams 2008, Farjon 2005, Farjon 2013). Hardy to Zone 6 (cold hardiness limit between -23.2°C and -17.8°C) (Bannister and Neuner 2001).
The species is classed "vulnerable" due to increasing development pressure that leads to habitat loss and exploitation of the trees, chiefly for firewood; regrowth is very slow. Yak grazing likely limits regeneration. The population is severely fragmented, with an estimated area of occupancy of only 1,175 km2 within an extent of occurrence of 1,044,420 km2, and the population trend is declining (Farjon 2013).
He et al. (2018) present a tree-ring chronology covering the period 1067 to 2010. They don't say if their sampling methodology only sampled living trees, but it seems likely, in which case they found at least one tree that was at least 943 years old.
Has been used in dendroclimatic work, especially, a study of long-term early summer drought severity covering 821 years (He et al. 2018).
This is the principal high altitude tree within most of its range, and consequently is the principal source of forest products to native people within that area. It is exploited mainly for firewood, and is also used for incense in Buddhist rituals (there are many Internet sources of such incense, but I have doubts about how much of it is J. tibetica; many other junipers also provide Buddhist incense). It is rarely seen in plantings outside of Tibet (Farjon 2013).
The epithet refers to the species' native range, Tibet.
Farjon, A. 2013. Juniperus tibetica. The IUCN Red List of Threatened Species 2013. http://www.iucnredlist.org/details/42256/0, accessed 2018.02.09.
He Minhui, Achim Bräuning, Jussi Grießinger, Philipp Hochreuther, and Jakob Wernicke. 2018. May–June drought reconstruction over the past 821 years on the south-central Tibetan Plateau derived from tree-ring width series. Dendrochronologia 47:48-57.
Komarov. 1924. Bot. Mater. Gerb. Glavn. Bot. Sada RSFSR 5:27.
Farjon (2005) provides a detailed account, with illustrations.
The species account at Threatened Conifers of the World.
Last Modified 2018-02-09