Taxus contorta
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Taxus contorta ( synonym : Taxus fuana ) is a conifer from the genus of the yew trees ( Taxus ). The natural range of the species is in China, Nepal, India, Pakistan and Afghanistan. It is listed as endangered onthe IUCN Red List . The representatives of this species are oftenassigned to Taxus wallichiana or referred to with the synonym Taxus fuana .
description
Appearance
Taxus contorta grows as an evergreen tree or shrub , usually up to 15, sometimes up to 20 meters high . The trunk of the trees is short or multiple trunks are formed. It reaches a diameter of up to 3 meters ( diameter at chest height ), but the trunks are then hollow. At the base of the stem is coppice often. The trunk bark is reddish brown, thin and flakes off in large, irregularly shaped layers. The numerous branches are ascending or erect and spread out further outwards and form a rounded or pyramidal crown. The needled twigs grow irregularly, alternating, they are thin, stem-round and have narrow grooves next to the descending needle bases. They are initially green, later yellowish brown and then gray.
Buds and needles
The terminal, vegetative buds are small, egg-shaped and have brown, roof-tile-like, firmly pressed, pointed bud scales. Lateral buds are common and dormant.
The needles grow on lateral shoots in a more or less V-shape on a short, only slightly twisted stem. They are linear, 1.5 to 4, rarely up to 4.5 centimeters long, 1.5 to 2.5 millimeters wide, straight or almost straight, have parallel, downwardly curved leaf edges and a sharply pointed tip. The middle rib on the top of the needle is raised, about 0.2 millimeters wide and extends almost all the way to the tip of the needle. It is flat on the underside, 0.4 millimeters wide and extends to the tip of the needle. The top of the needle is glossy dark green, the bottom shows two pale, yellowish green stomata with stomata and irregularly distributed stomata.
Cones and seeds
The pollen cones stand individually in the axils of the needles and form rows on both sides of the branches. They are egg-shaped, 6 to 8 millimeters long, with short stems and have dry, yellowish green or brown scales at the base. The six to 14 initially reddish and later brown microsporophylls are shield-shaped and have four to nine partially fused pollen sacs on their underside .
The structures that carry the seeds (seed cones) grow individually in the axils of the needles. They are seated and have small, triangular scales that surround a small short shoot with the terminal ovule . The aril is initially green and covers the lower half of the seed. It later swells, grows cup-like over the seed, but the tip of the seed remains free and turns red. It is then 9 to 12 millimeters long and 7 to 9 millimeters wide. The seeds are elongated, slightly flattened, blunt-toothed on two sides near the tip and have a small spiked tip. They are initially green and when ripe brown or black, 6 to 7 millimeters long and 4 to 5 millimeters wide.
The pollen is released in April, the seeds ripen from September to November.
Distribution and ecology
The natural range of Taxus contorta is in China in the southwest of the Tibet Autonomous Region , it includes central and western Nepal and the Indian states of Himachal Pradesh , Jammu and Kashmir and Uttar Pradesh , northern Pakistan and, as the only yew species, Afghanistan. The distribution area is assigned to winter hardiness zone 8 with mean annual minimum temperatures between −12.2 and −6.7 ° C (10 to 20 ° F ). In Tibet, the species is found in pine forests and mixed forests, mostly below the crown layer with heights of growth of up to 12 meters at altitudes of 2500 to 3100, rarely up to 3400 meters above sea level. In Afghanistan they are found as a less important part of the coniferous forests at altitudes of 2400 to 2900 meters in the northeast of the Hindu Kush . In Pakistan it grows in the province of Khyber Pakhtunkhwa , in the tribal areas under federal administration and in the semi-autonomous region of Asad Kashmir, mostly on northern slopes at altitudes of 2000 to 3100 meters in mixed coniferous forests together with the Himalayan cedar ( Cedrus deodara ), the Pindrow fir ( Abies pindrow ), the Himalayan spruce ( Picea smithiana ) and the teardrop pine ( Pinus wallichiana ). The higher altitudes seem to be determined by precipitation in the direction of lower altitudes and by temperature at higher altitudes. In north-west India and Nepal, smaller stands are scattered in coniferous forests along rivers at altitudes of 1700 to 2600 meters, i.e. at lower altitudes than in Pakistan, probably due to the higher rainfall.
Hazard and protection
In the Red List of the IUCN is Taxus contorta as endangered ( "Vulnerable") out. The extent of occurrence covers more than 20,000 square kilometers, but the populations themselves are mostly small, so that the actually overgrown areas (“area of occupancy”) are only estimated at 2000 square kilometers. The stocks have declined by 50 to 80 percent, the reasons for this are the overuse to use parts of the trees as medicinal products, but also to use the wood and as fodder for farm animals. There are no exact figures for Afghanistan, but in the last 25 years (as of 2010) the coniferous forests in general have declined by up to 50 percent due to the war and the unregulated felling of the trees, while Pakistan has declined by up to 80 percent reported, and Northwest India and Nepal have depleted stocks by 90 percent, mainly due to drug mining. It is known from China that stocks are also falling, but it is unclear to what extent.
Systematics and Etymology
Taxus contorta is a species from the genus of the yew trees ( Taxus ). It was first described in 1854 by William Griffith in the Notulae ad Plantas Asiaticas . For a long time all yew trees growing in the Himalayas were assigned to the species Taxus wallichiana , a taxon also known as the subspecies Taxus baccata subsp. wallichiana of the European yew tree ( Taxus baccata ) was seen. Later, the populations west of central Nepal were assigned to the species Taxus fuana Nan Li & RRMill , which was established in 1997 and was described on specimens from southwest Tibet. In his book Conifers of the World , published in 2009, James E. Eckenwalder continues to assign all yew trees growing in the Himalayas to Taxus wallichiana , but points out that this is more of a conservative classification. However, the distinction between the two species has been confirmed by further research, this distinction and the name Taxus fuana is also used in the Flora of China . The trees and shrubs that were assigned to Taxus fuana , however, correspond to the description of the much earlier established species Taxus contorta , a name that therefore has priority, Taxus fuana is therefore only a synonym for Taxus contorta .
The generic name Taxus is the classic Latin name of the "yew". The specific epithet contorta means "entwined" or "twisted", but it is unclear why William Griffith chose this name.
use
The ingredients of the leaves and bark of Taxus contorta and other species of yew are used as a cure for cancer . However, harvesting these parts usually leads to the death of the trees and bushes.
swell
literature
- Aljos Farjon: A Handbook of the World's Conifers . tape 2 . Brill, Leiden-Boston 2010, ISBN 978-90-04-17718-5 , pp. 976, 977 .
- James E. Eckenwalder: Conifers of the World. The Complete Reference . Timber Press, Portland, OR / London 2009, ISBN 978-0-88192-974-4 , pp. 601 .
- Wu Zheng-yi, Peter H. Raven (Ed.): Flora of China . Volume 4: Cycadaceae through Fagaceae . Science Press / Missouri Botanical Garden Press, Beijing / St. Louis 1999, ISBN 0-915279-70-3 , pp. 90 (English).
- Helmut Genaust: Etymological dictionary of botanical plant names. 3rd, completely revised and expanded edition. Nikol, Hamburg 2005, ISBN 3-937872-16-7 , pp. 174, 631-632 (reprint from 1996).
Individual evidence
- ↑ a b c d e f g h i j Aljos Farjon: A Handbook of the World's Conifers. Volume 2, p. 976
- ^ A b Liguo Fu, Nan Li, Robert R. Mill: Taxus fuana , in Flora of China , Volume 4, p. 90
- ↑ a b c d e Taxus contorta in the Red List of Threatened Species of the IUCN 2013. Posted by: P. Thomas, 2010. Retrieved on January 12, 2014.
- ↑ a b James E. Eckenwalder: Conifers of the World , p. 601
- ^ Taxus contorta. In: The International Plant Name Index. Retrieved January 12, 2014 .
- ↑ Michael Möller, Lian-Ming Gao, Robert R. Mill, De-Zhu Li, Michelle L. Hollingsworth, Mary Gibby: Morphometric analysis of the Taxus wallichiana complex (Taxaceae) based on herbarium material . In: Botanical Journal of the Linnean Society . No. 155 , 2007, p. 307-335 ( online [PDF]).
- ↑ Exactly: Etymological Dictionary of Botanical Plant Names, pp. 631–632
- ↑ Exactly: Etymological Dictionary of Botanical Plant Names , p. 174
- ^ Aljos Farjon: A Handbook of the World's Conifers. Volume 2, p. 977
Web links
- Taxus contorta at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed January 12, 2014.
- Taxus contorta in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland.