Scientific name: Pinus culminicola Andresen & J. Beaman 1961
Synonyms: -
Common names: Potosí pinyon (English), Potosí piñon, Pino piñonero enano, Piñón amarillo (Spanish)
Description
Low, multitrunked shrub, or tree to 10 m tall, with trunk to 0.5 m in diameter. Bark dark grayish brown, scaly and broken up into irregular, small plates by shallow furrows. Crown spreading rounded or flat-topped, often dense, with numerous slender, horizontal or upwardly angled branches densely clothed with foliage at the tips. Twigs light brown at first, becoming gray, hairless, generally stiff and roughened with scale leaves. Buds 5-10 mm long, not resinous. Needles in bundles of two to five (or six), sticking together during the first year, each needle (2-)3-5(-6) cm long, stiff and curved, lasting 2-5(-7) years, bluish green to grayish green. Individual needles with lines of stomates only on the inner faces, an undivided midvein, and two or three (to five) resin canals inside the epidermis of the outer face. Sheath 4-8 mm long, the scales separating or curling back and usually persisting the first year. Pollen cones 4-8 mm long, light purplish yellow. Seed cones (2-)2.5-4.5 cm long, spherical to somewhat flattened, with 20-30(-40) seed scales, purplish green before maturity, ripening yellowish brown to reddish brown, opening widely to release the seeds and then falling with the 3-8(-10) mm long, curved stalk. Seed scales paddle-shaped, the deep pockets for the seeds just reaching the diamond-shaped exposed portion that rises in a low pyramid on the face and ends in a large diamond-shaped umbo sometimes bearing a small, fragile prickle. Seed body 5-16 mm long, the shell (0.1-)0.3-1(-1.3) mm thick, the rudimentary wing remaining attached to the seed scale.
The scientific name, Latin for “peak dweller or growing on the summit (of mountains)”, refers particularly to variety culminicola, which reaches the highest elevations of any pinyon and experiences the most humid environment among them.
Southeastern Arizona to the Edwards Plateau of Texas south through the Sierra Madre Occidental and Sierra Madre Oriental and interior ranges of Mexico to southern Zacatecas and southern San Luis Potosí. Woodlands and thickets, generally on dry soils over limestone; (450-)1,200-3,700 m.
Conservation Status
Red List Category & Criteria: Endangered
Pinus culminicola is only known from a few mountain tops. The largest and best known subpopulation on Cerro Potosí covered several km² but they have been substantially reduced by fires in recent years. Most other subpopulations (9-10) are much smaller in extent. The area of occupancy, derived from mapping herbarium specimens, is between 10 and 20 km². The actual area of occupancy is much less. The population is severely fragmented as it is restricted to mountain summits and does not occur in the intervening valleys. There has been a recent decline due to fire and a decline is predicted to continue in future unless adequate counter measures are taken. Consequently, this species is assessed as Endangered.
The altitudinal range of Pinus culminicola is 3,000-3,700 m a.s.l., which includes the highest ridges of these mountains. Its habit is very similar to other mountain 'dwarf pines', e.g. Pinus mugo in Europe and Pinus pumila in NE Asia. Adaptation to blasting, ice- or sand-laden winds and a short growing season is responsible for this habit. Soils are mostly rocky and calcareous. Climatic conditions are not well known due to a lack of weather stations at these summits, but precipitation, some of it as snow, is probably abundant. On Cerro Potosí, the species forms extensive monocultures of close-packed individuals. It occurs there with scattered, stunted Pinus hartwegii, which indicates that the climatic tree line is not reached there at around 3,700 m. Somewhat lower, on the Sierra La Marta, Coahuila, Pinus culminicola has been found in a scrub-community with Quercus spp., Arctostaphylos, Ceanothus, Agave and grasses; on the Cerro La Viega and the Sierra de Arteaga, Coahuila, a similar vegetation, but also with Abies and Pseudotsuga, are reported growing scattered with Pinus culminicola. Pollen dispersal has been reported on Cerro Potosí to occur in late July, at 3,690 m, which indicates a late fertilization and short growing season.
This species is vulnerable to fire during long dry periods. In recent years, devastating fires have destroyed large parts of the population on Cerro Potosí and regeneration is very slow. Grazing and trampling also inhibit regeneration. Fires may increase in other localities when they become more frequently visited by campers, etc., being in the vicinity of two major population centres. As this species has a very narrow ecological niche within the summit area it may be vulnerable to the potential effects of climate change.
This species is not used commercially, although locally it may be used for firewood. It should be suitable as a low bushy pine for large rockeries, has attractive foliage, and deserves to be taken into cultivation for horticulture.
Protection against man-made fires and the management of grazing is essential especially within protected areas such as on Cerro Potosí, a national park. Tourism and outdoor camping, picnicking, etc. need to carefully managed. Restoration programmes at the Cerro Potosi site have been initiated. On a recent visit to the summit of Cerro El Potosi (April 2012), a slow recovery of populations devastated by fires was apparent (J. Perez de la Rossa unpubl. data).
Cultivars
Not known
References
- Farjon, A. (2010). A Handbook of the World's Conifers. Koninklijke Brill, Leiden.
- Eckenwalder, J.E. (2009) Conifers of the World: The Complete Reference. Timber Press, Portland.
- IUCN Red List of Threatened Species, International Union for Conservation of Nature and Natural Resources. Cambridge, UK /Gland, Switzerland
Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.