Pinus leiophylla description

Cone about 5 cm long on a tree of var. chihuahuana in Chiricahua National Monument, Arizona [C.J. Earle, 1989].

Distribution of P. leiophylla. The red bars mark the zone of overlap between var. leiophylla to the south and var. chihuahuana to the north. Map based on Critchfield and Little (1966) with varieties demarcated on the basis of Farjon and Styles (1997).

Pinus leiophylla Schiede ex Schlechtendal et Chamisso 1831

Common Names

Taxonomic notes

Two varieties, P. leiophylla var. leiophylla and P. leiophylla var. chihuahuana (Engelm.) Shaw 1909. The var. chihuahuana was separately described by Engelmann in Wislizenius 1848 as Pinus chihuahuana, and the relationship between that taxon and Pinus leiophylla was discerned by Shaw (1909). Some authors (e.g. Martínez 1948) continue to discriminate the two species, but both taxa share several highly distinctive features while differing almost solely in minor foliage characters (chiefly number of needles per fascicle), suggesting that these taxa are appropriately discriminated at the varietal rank. The distinctive features include a three-year cone maturation, unique in Latin American pines (but also seen in Pinus pinea); the ability to coppice (resprout from a cut stump), shared with Pinus rigida; and the common production of adventitious shoots, shared with a variety of species (photo on the Pinus canariensis page). However, it is curious that the two varieties maintain their distinctive properties despite being sympatric over large areas, which suggests that further study of their relationship is warranted (Farjon and Styles 1997).

Typical of early-collected pines (this species was described in 1831, along with Pinus patula), the holotype consists of a single sheet with two sterile branchlets.

Description

Tree, 15-35 m tall and 20-85 cm dbh, usually with a single round trunk often clear of branches for 60% of height, and an open, rounded crown. Bark dark grey-brown, very thick, rough, scaly, divided into elongate irregular scaly plates with deep longitudinal fissures; on young trees and branches scaly, flaking, red-brown to grey-brown. Branches long, slender, spreading or ascending, the lower ones curved downwards. Shoots scaly with short, decurrent pulvini, red-brown or glaucous turning grey-brown. Fascicle sheaths 12-20 mm long with 5-6 early-deciduous scales, so that mature fascicles have no sheath. Leaves in fascicles of (2-)3-5(-6), spreading in lax or rigid tufts near the ends of branches, persisting 2-3 years, (4-)6-15(-17) cm × 0.5-1.3(-1.5) mm, margins minutely serrulate, light green, stomata on all faces in 4-8 lines on the convex abaxial face, 3-4 lines on the adaxial faces. Resin ducts 2-6, medial, sometimes 1-2 internal, stele round with 2 vascular bundles. Pollen cones crowded near end of shoots in a short dense cluster, cylindrical, 10-15(-20) × 4-6 mm, yellow-pink maturing light brown. Seed cones subterminal, solitary or in whorls of 2-5 on stout peduncles 10-20 mm long, persisting several years after opening. Immature cones ovoid to subglobose, pink turning purple-green to purple-brown, maturing in three seasons. Mature cones ovoid, nearly symmetrical, (4-)5-7(-8) × (3-)4-5.5 cm when open. Seed scales 50-70, straight or recurved near base of cone, on abaxial side dark purple-brown turning grey, on adaxial side purple-brown with lighter grey marks of seed wings. Apophysis raised, transversely keeled, with the second season's growth showing as a narrow band around the umbo; rhombic, up to 15 mm wide, brown. Umbo dorsal, pyramidal, with a blunt prickle, darker than the apophysis. Seeds ovoid, 3-4(-5) mm long, dark grey-brown with black spots. Seed wings articulate, oval, 10-18 × 4-8 mm, yellow-brown, translucent. Adventitious shoots may sprout after fire or cutting (Farjon and Styles 1997).

Var. leiophylla has leaves chiefly in fascicles of 5, 0.5-0.9 mm wide, with 4-6 lines of stomata on the abaxial face and 2-3 resin ducts. Var. chihuahuana has leaves chiefly in fascicles of 3, 0.9-1.3 mm wide, with 5-8 lines of stomata on the abaxial face and 4-6 resin ducts (Farjon and Styles 1997).

The early-deciduous fascicle sheaths on a hard pine represent a simple, reliable character that makes it easy to identify this species in the field.

Range

Mexico: Sonora, Chihuahua, Durango, Nayarit, Zacatecas, Jalisco, Michoacán, México, Distrito Federal, Hidalgo, Morelos, Tlaxcala, Puebla, Veracruz, Guerrero, and Oaxaca; USA: Arizona and New Mexico; at 1500-3300 m elevation. From Zacatecas northward var. leiophylla is gradually replaced by var. chihuahuana, with which it is sometimes grows (Farjon and Styles 1997). See also Thompson et al. (1999).

Big Tree

I only have data for variety chihuahuana, which see.

Oldest

Dendrochronology

There is no record of dendrochronological use of this species (as of May 2005).

Ethnobotany

I have no data on its aboriginal uses. Since the mid-20th Century, exploitation of this species has increased throughout much of its range, particularly in the Sierra Madre Occidental. It is tapped for resin and cut for timber, although the resinous wood is of limited utility. Var. chihuahuana is particularly exploited for resin production (Farjon and Styles 1997).

Observations

See the pages for each variety.