Pinus ayacahuite

Ehrenberg ex Schlechtendahl 1838

Common names

Mexican white pine, Arizona white pine, Ayacahuite pine (Peattie 1950 [as P. reflexa]), pino (Gentry 1942 p.76).

Taxonomic notes

Section Strobus. Two varieties, ayacahuite and veitchii. The variety brachyptera recognized by Perry (1991) and certain earlier authors, is here placed in synonymy with P. strobiformis, in accordance with the analysis by Farjon and Styles (1997).

Description

This is a fairly typical white pine in most respects. It forms a large tree, to 45 m tall and 200 cm dbh, with a straight, round trunk and pyramidal to conical crown with regular branch whorls, becoming more irregular and open in old trees. Bark is thin, smooth, and ash-grey on young trees, with age becoming rough, gray-brown, divided into small rectangular plates. Branches are long, slender, spreading horizontally, lower branches often drooping. Twigs are slender, smooth and light grey with foliage grouped toward the end. Leaves are in fascicles of 5, 10-18 cm long, abaxial surface bright green, adaxial surface glaucous and the only surface bearing stomata, margins serrate with very small, widely spaced teeth, straight or slightly twisted, spreading at 60-80° from the shoot, flexible but not drooping, cross-section nearly an equilateral triangle, resin canals 2-4(-7), external; fascicle sheathes 15-20(-25) mm long with 5-7 loose, oblong, orange-brown or red-brown scales, soon deciduous. Cotyledons 11-13. Pollen cones crowded at ends of new shoots, ovoid to short cylindrical, 7-10 mm long, yellow, turning orange-brown. Seed cones borne near ends of main branches, usually in whorls of 2-4, with a peduncle to 25 mm long that falls with the cone, pendent, slightly curved, 15-40 cm × 7-15 cm when mature and open, soon deciduous. Seed scales 100-150, thin, flexible, 5-7 cm long, apophyses elongate with a rounded to obtuse apex, umbo terminal, resinous, and lacking a prickle. Seeds light brown with dark spots, with an adnate wing 30-40 mm long (Perry 1991, Farjon and Styles 1997). Seed size is unclear; 5-8 mm (Perry 1991) or 8-15 mm (Farjon and Styles 1997).

In habitat, it is difficult to confuse this species with any other. It occupies higher and drier sites, and has much longer cones, than Pinus chiapensis.

Distribution and Ecology

Mexico: Jalisco, Querétaro, Michoacán, Hidalgo, Distrito Federal, México, Guanajuato, Veracruz, Tlaxcala, Morelos, Puebla, Guerrero, Oaxaca and Chiapas; also Guatemala, El Salvador and Honduras (Perry 1991). See map at left. P. ayacahuite typically grows in mixed stands with other pines, and firs, at altitudes of (1,500-)2,000-3,200(-3,600) m. It grows best on well-drained moist loamy soils on relatively cool, moist sites (Perry 1991, Farjon and Styles 1997). In Los Altos de San Miguel Totonicapán park, Guatemala, it grows with Pinus montezumae, P. pseudostrobus, P. hartwegii, P. oocarpa, Abies guatemalensis, and Cupressus lusitanica (ParksWatch 2004).

Distribution data from USGS (1999).

Hardy to Zone 7 (cold hardiness limit between -17.7°C and -12.2°C) (Bannister and Neuner 2001). See also Thompson et al. (1999).

Big tree

The largest I have seen was a specimen of var. veitchii 137 cm dbh and 32 m tall, which we found on the NE slopes of Popocatepetl in 2005. Another tree in the same area was only 105 cm dbh, but 42.1 m tall. I have no other data on big trees.

Oldest

Dendrochronology

As of 2006, almost no work has been done with this species; it is mentioned in Heyerdahl and Alvarado (2003) but I don't know if it proved to be a useful species. One study performed in Oaxaca (Naylor 1971) found generally unsatisfactory results: all sampled trees were young, complacent, and could not be crossdated. This finding was attributed to an insufficiently seasonal climate. It was later used in a fire history study in Chihuahua, a more northerly and more seasonal climate (Fulé et al. 2005). For updated information, see the Bibliography of Dendrochronology.

Ethnobotany

This species provides one of the most important and sought-after softwoods of Mexico. Formerly very large trees were common, yielding large volumes of an attractive, easily worked timber that provided the raw material for furniture and finish carpentry throughout the country. Those great stands have been largely depleted now, especially in southern Mexico and Mesoamerica (Perry 1991, Farjon and Styles 1997).

Observations

See the variety descriptions.

Remarks

The hybrid between P. ayacahuite and P. wallichiana occurred naturally in 1904 at the Westonbirt Arboretum in Gloucestershire, England. This fertile hybrid is called Pinus × holfordiana.

Citations

Heyerdahl, E.K. and E. Alvarado. 2003. Influence of climate and land use on historical surface fires in pine-oak forests, Sierra Madre Occidental, Mexico. Pages 198-217 in T.T. Veblen, W.L. Baker, G. Montenegro, and T.W. Swetnam, eds., Fire and Climatic Change in Temperate Ecosystems of the Western Americas. New York: Springer-Verlag.

Naylor, T.H. 1971. Dendrochronology in Oaxaca, Mexico: a preliminary study. Tree-Ring Bulletin 31:25-29. Available online at www.treeringsociety.org/TRBTRR/TRBvol31_25-29.pdf (accessed 2006.06.14).

Schlechtendahl, D.F.L. von. 1838. Vorlaufige Nachricht uber die Mexicanischen Coniferen. Linnea: ein Journal für die Botanik in ihrem ganzen Unfange 12:486-496. Available: www.botanicus.org, accessed 2011.03.20.

See also

Farjon et al. 1997.

Wright, J.A., A. Marin V., and W.S. Dvorak. 1996. Ex situ gene conservation of Pinus ayacahuite, in Forest Genetic Resources No. 24. www.fao.org/docrep/008/w3354e/W3354E20.htm, accessed 2011.02.25.