Distribution

China: S Xizang [Tibet] (Zangbo River Valley, from ca. 93° to ca. 96° E); and possibly extreme NW Yunnan (vicinity of Dêqên on the Langcang [Mekong] River), based on a specimen collected in 1992 which is deposited at RBG Edinburgh ( E) .

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 (3120–3210 metres above sea-level) each covering an area of 1km² which 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. This taxon is common along the Yarlung Tsangpo valley from Nang for about 30–40km 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 (Rushforth, pers. obs., 1995-1999). It is estimated that the number of mature individuals throughout the range do not total more than 5000 trees and since 1998 the extant population of mature individuals is believed to have stabilized.

Habitat and Ecology

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 500mm; rainfall is from June-September.

Conservation Status

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.

Conservation Actions

Global status and rationale

Vulnerable A2cd

The historic loss of up to 50% of mature individuals in the last three generations places this taxon into VU under criterion A.

Global threats

Due to the scarcity of timber in the region where scattered groves of this taxon occur, 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.