Pinus nelsonii
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Branches with needles and seed cones |
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| Shaw |
Pinus nelsonii is an evergreen conifer from the genus of the pines ( Pinus ) with usually three to three, 4 to 8 centimeter long needles that have grown together for one to two years and only separate on the tree in the last year. The seed cones reach a length of 7 to 12 centimeters. The natural range extends to the foothills of the Sierra Madre Oriental in a few states of Mexico. With less than 10,000 adult specimens, it is classified as endangered inthe IUCN Red List .
description
Appearance
Pinus nelsonii grows as an evergreen , 5 to 10 meter high tree or less often as a shrub. The trunk is usually straight and reaches a diameter of 15 to 30 centimeters at chest height . In some trees it branches out near the bottom. The trunk bark is ash gray with darker, brownish banded areas, thin and smooth. Only the lower area of larger trees becomes scaly. The branches are arranged in an ascending or irregular manner and form a conical crown in young trees and a broad, very open and irregular crown in older trees. The branches elongate significantly before they stiffen and bear needles. They are hairless, white-gray and sometimes covered by a thin layer of wax ( glauk ).
Buds and needles
The lower leaves are 5 to 8 millimeters long, awl-shaped , brittle, dark brown and have an irregularly jagged edge. The vegetative buds are egg-shaped-pointed to oval and resinous. Terminal buds are up to 10 millimeters long, lateral buds are shorter. The needles grow in threes, rarely in groups of four, in a needle sheath that is initially 7 to 9 millimeters long and remains dark brown or gray when exposed to the weather. The needles have grown together in the first few years and thus appear as a single needle. They stay on the tree for two to three years and only separate in the last year. They are dark green or gray-green covered with wax, stiff, straight or slightly curved, twisted around the longitudinal axis, 4 to 8 rarely up to 10 centimeters long and 0.7 to 0.8 millimeters thick. The edge of the needle is finely sawn, the end pointed. There are stomata lines on all needle sides . Two large resin channels are formed near the surface of the needle.
Cones and seeds
The pollen cones are initially pink and later brown, oval-oblong to cylindrical and 7 to 9 millimeters long with a diameter of 3.0 to 3.5 millimeters. The seed cones grow individually or in pairs on 2.5 to 6.5 centimeters long, 7 to 10 millimeters thick, curved stems. In contrast to other pine species, the stems sometimes have bundles of needles, which, however, fall off until the cones are ripe. Mature cones are irregularly cylindrical, rarely from 5, mostly 7 to 12 inches long and 4.0 to 5.5 inches wide when opened. They usually fall off without a stem, the stem remains on the tree. The 50 to 100 short and 20 to 25 millimeter wide seed scales are green, later purple and reddish brown when ripe, thick and irregularly shaped. They have one or two cup-shaped depressions in which the seeds develop. The scales open only a little and usually not far enough to release the seeds; however, with their wedge-shaped base they are easily detached from the thick pin axis. The apophysis is reddish brown to dark brown, clearly raised, irregular in outline, keeled transversely and wrinkled. The umbo is dorsal. It is keeled across, blunt, 10 to 15 millimeters wide, 3 to 4 millimeters high and reinforced with a small, triangular spine . In contrast to all other pine trees, the cones do not grow for several months, which means that the umbo is only indistinctly different from the apophysis. The cones ripen in November 18 to 19 months after pollination .
The seeds are pale to dark brown, obliquely obovate, 12 to 15 millimeters long, 8 to 10 millimeters wide and about 1 millimeter thick. They have a thick and very hard shell. The seed wings are only rudimentary and mostly remain on the cone scales.
Distribution, ecology and endangerment
The natural range of Pinus nelsonii is in Mexico in the states of Coahuila , Nuevo León , San Luis Potosí and Tamaulipas .
Pinus nelsonii grows in the semi-arid climate of the foothills of the Sierra Madre Oriental . The largest stocks can be found around the Sierra Peña Nevada in Nuevo León and Tamaulipas. It grows exclusively on flat ground over rocky limestone at altitudes of 1600 to 2300 meters, rarely up to 2450 meters. The distribution area is assigned to winter hardiness zone 9 with mean annual minimum temperatures between −6.6 and −1.2 ° Celsius (20 to 30 ° Fahrenheit ). The annual rainfall ranges from 300 to 600 millimeters and falls mainly in summer in short thunderstorms.
One finds Pinus nelsonii together with other conifers like Pinus cembroides , Pinus remota and different kinds of juniper ( Juniperus spp.). In the scrubland it grows together with deciduous species of the oak ( Quercus ), Mahonia , Comarostaphylis , Brahea and Sophora and monocotyledonous plants such as representatives of the palm lily ( Yucca ) and the genus Dasilyrion . In higher-lying areas it grows in dry semi-deserts, which are often dominated by cacti (Cactaceae) and palm lilies, at even higher altitudes in forests made of pine and juniper.
The seeds usually do not fall out of the cones themselves, but are spread by birds such as the gray breasted jay ( Aphelocoma ultramarina ).
In the Red List of the IUCN is Pinus nelsonii as endangered ( "Endangered") classified. Pinus nelsonii is a rare species with scattered populations that usually cover less than a square kilometer. The total distribution area is estimated - possibly optimistically - at around 84 square kilometers. The population is declining and consists of less than 10,000 fully grown trees, mostly in groups of a few hundred specimens. They are endangered by human interference, especially by the expansion of cattle pastures and the associated devastating fires. Some holdings for which there are records in the literature and from herbaria were no longer found and probably no longer exist.
Systematics and research history
Pinus nelsonii is a species from the genus of the pines ( Pinus ), in which it is assigned to the subgenus Strobus , section Parrya and subsection Nelsoniae . The species was formerly assigned to the sub-section Cembroides and has several morphological similarities with basic representatives of this group, for example with Pinus pinceana , Pinus rzedowskii and Pinus maximartinezii . Genetic studies show, however, a closer relationship with representatives of the sub-section Balfourianae , but the differences to this group are so great that it was the only species to be placed in the sub-section Nelsoniae .
The species was first scientifically described by George Russell Shaw in 1904 in The Gardeners' Chronicle as Pinus nelsonii . The generic name Pinus was already used by the Romans for several types of pine. The specific epithet nelsonii honors Edward William Nelson (1855-1934), who, in addition to many other Mexican plants, also collected the type specimen of Pinus nelsonii for the US Department of Agriculture in 1898 .
No synonym of the species is known.
use
Due to its rarity and small size, Pinus nelsonii is not used as a supplier of wood. The seeds are similar to those of the subsection Cembroides and are edible, but the quantities of seeds are small. Except in a few botanical gardens and arboretums, the species is not used for horticulture.
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literature
- Aljos Farjon: A Handbook of the World's Conifers . tape 2 . Brill, Leiden-Boston 2010, ISBN 90-04-17718-3 , pp. 720-721 .
- James E. Eckenwalder: Conifers of the World. The Complete Reference . Timber Press, Portland, OR / London 2009, ISBN 978-0-88192-974-4 , pp. 454-455 .
- Helmut Genaust: Etymological dictionary of botanical plant names. 3rd, completely revised and expanded edition. Nikol, Hamburg 2005, ISBN 3-937872-16-7 , p. 487 (reprint from 1996).
Individual evidence
- ↑ a b c d e Aljos Farjon: A Handbook of the World's Conifers , Volume 2, p. 720
- ↑ a b c d e f James E. Eckenwalder: Conifers of the World , p. 455
- ↑ a b Christopher J. Earle: Pinus nelsonii. In: The Gymnosperm Database. www.conifers.org, November 23, 2012, accessed on July 21, 2013 .
- ↑ a b c d Aljos Farjon: A Handbook of the World's Conifers , Volume 2, p. 721
- ↑ Pinus nelsonii in the endangered Red List species the IUCN 2013. Posted by: A. Farjon, 2011. Accessed July 21, 2013.
- ↑ James E. Eckenwalder: Conifers of the World , p. 454
- ↑ Pinus nelsonii. In: The International Plant Name Index. Retrieved July 21, 2013 .
- ↑ Exactly: Etymological Dictionary of Botanical Plant Names , p. 487
- ↑ Pinus nelsonii. In: The Plant List. Retrieved July 21, 2013 .
Web links
- Pinus nelsonii at Tropicos.org. Missouri Botanical Garden, St. Louis, accessed July 21, 2013.