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Scientific name: Picea chihuahuana M.Martínez 1942
Synonyms: Picea martinezii T.F.Patt.
Common names: Chihuahua spruce (English), Pinabete, Cahuite, Cahuite Espinoso, Cahuite bravo (Spanish)
Tree to 30(-45) m tall, with trunk to 0.7(-1.2) m in diameter. Bark gray, flaky, with small checkers separated by shallow, narrow grooves. Crown broadly conical, with gracefully arched branches of very different lengths at a given level, bearing horizontal or slightly drooping side branches. New branchlets pale yellowish brown, hairless. Buds (4-)7-8(-10) mm long, resinous. Needles grayish green with wax, (1.2-)1.5-2(-2.5) cm long, straight or gently curved forward, diamond-shaped, with three to six lines of stomates in a band along the center of each of the four faces, very prickly. Pollen cones (1-)2-3 cm long, reddish. Seed cones (8.5-)10-14(-16) cm long, green before maturity, ripening chestnut brown. Seed scales egg-shaped, thin and flexible. Seed body (3-)4-6(-8) mm long, the wing 7-13 mm longer.
Sierra Madre Occidental in southwestern Chihuahua and western Durango and Sierra Madre Oriental in Nuevo León (Mexico). Usually mixed with other conifers and a few hardwoods along streams in montane forest; (2,150-)2,300-2,700(-3,400) m.
Red List Category & Criteria: Endangered
The area of occupancy of 275 km² is well within the threshold for Endangered, subpopulations are severely fragmented and there is an ongoing decline due to fires, logging and grazing. On this basis alone Picea chihuahuana meets the B2 criteria for Endangered. The number of mature individuals is uncertain but could be less than 2,500.
The population of mature individuals may not exceed 2,500 to 3,000 mature trees with a total population including seedlings and saplinds estimated to be about 43,000 in 38 stands. Subpopulations are usually smaller than 350 trees, show significant levels of inbreeding and a lack of geneflow.
Picea chihuahuana occurs in scattered relict populations on N-facing high mountain sides, often in canyons, at elevations between 2,150 m and 3,200(-3,400) m a.s.l. It grows in poor, barren, but always moist mountain soils of alluvial origin, usually near permanent streams, but in the Sierra Madre Oriental also on calcareous lithosols. The climate is cool and moist, with annual precipitation between 800 mm and 1,300 mm, mostly as summer showers, but in the western part of the range also in winter; snow only at the highest elevations. It is mainly associated with Pinus strobiformis, Pinus pseudostrobus, Pinus ayacahuite. Some other pines, Pseudotsuga menziesii var. glauca, Abies durangensis, Abies vejarii (in Sierra Madre Oriental), Cupressus lindleyi (= Cupressus lusitanica Mill.), and Cupressus arizonica may also occur. Broad-leaved trees are e.g. Quercus castanea, Quercus rugosa and Prunus serotina.
The subpopulations of Picea chihuahuana are widely scattered and very small, with a total of fewer than 100 to about 350 mature trees in each of the ca. 25 localities known. It is possible that other relict populations are hidden among the pine forests of the Sierra Madres of northern Mexico, yet its total area of occupancy (AOO) is unlikely to exceed 500 km² and is by all accounts much less than this (here calculated to be 275 km² with a 5x5 km grid); in addition, it is severely fragmented. Unaware of its botanical significance, loggers have exploited this species where they have encountered it, reducing the number of mature individuals. In many stands natural regeneration has been observed to be poor or at best slow. Awareness of its significance for conservation of biodiversity is now increasing, but few subpopulations are as yet under any effective protection.
The rarity of this species renders it economically unimportant as a timber tree. However, its potential size in old-growth stands has made it a valuable resource of good timber when encountered by loggers, and trees have been logged to be processed in local sawmills. The species is still uncommon in cultivation.
More subpopulations or localities with this species are in need of being put into protected areas, as only a few are at present within such areas. According to the Secretaría de Medio Ambiente y Recursos Naturales (2010), Norma Oficial Mexicana, this species is in danger of extinction.
Copyright © Aljos Farjon, James E. Eckenwalder, IUCN, Conifers Garden. All rights reserved.
