Pinus lumholtzii

B.L. Robinson et Fernald 1894

Common names

Pino triste ("sad pine" due to its "weeping" foliage) (Farjon and Styles 1997); sa wá in the local Rarámuri language (Sierra Madre Alliance 2007).

Taxonomic notes

Syn.: Pinus patula B.C. Seemann 1856 non Schlechtendahl et Chamisso 1831. This is another of the 23 species in the large and largely undifferentiated subsection Australes. Discovered near Tutuaca, directly west of the city of Chihuahua; type specimen, Hartman 541, was collected near Coloradas, Chihuahua during an expedition led by archeologist Carl Lumholtz (Shaw 1909, Farjon and Styles 1997). Coloradas represents the approximate northern range limit of the species.

Description

This is one of those species that elicits the first impression, "what is THAT?" The long needles, hanging absolutely lax and pendulous from the branchlets, readily distinguish it from any other pine. It also has one of the smallest cones found on Mexican pines. A more complete description follows:

Trees to 20 m tall and 50-70 cm dbh. Trunk usually round, straight, erect, with a broad, rounded, open crown. Bark scaly, flaking, red-brown on young trees, later becoming thick, scaly, rough, divided into irregular elonated plates divided by deep, broad longitudinal fissures, grey-brown to grey. Primary branches long, spreading, ascendent; higher order branches flexible, drooping. Shoots ridged between decurrent pulvini, first glaucous, later red-brown, turning grey. Fascicle sheaths (20-)25-35 mm long at first, soon coming apart to form a tuft of curling scales at the base of the fascicle, which is later deciduous. Needles in fascicles of 3 (rarely 2 or 4), extremely pendulous, persisting two years, lax but not thin, (15-)20-30(-40+) cm × (1-)1.2-1.5 mm, light green, acute with serrulate margins. Stomata on all leaf faces, conspicuous. Resin ducts 4-10 medial, sometimes 1-4 internal. Pollen cones sparsely clustered near the proximal end of new shoots, cylindrical, 20-30 × 5  mm at maturity, pinkish turning yellow at maturity. Seed cones subterminal or lateral, solitary (occasional whorls of 2, rarely 3) on 10-15 mm long curved peduncles that fall with the soon-deciduous cones. Young cones broad-ovoid to subglobose with curved spines, maturing in 2 seasons. Mature cones ovoid; when open, (3-)3.5-5.5(-7) × (2.5-)3-4.5 cm. Seed scales ca. 70-90, spreading wide, thick woody, adaxial surface dark brown with light brown marks of seed wings. Apophysis slightly raised, distally thickened, obscurely transversely keeled, rhombic to pentagonal in outline, ochre to red-brown. Umbo dorsal, flat or slightly raised, up to 5 mm wide, with a minute, soon-deciduous prickle. Seeds obovoid, slightly flattened, 3-5  mm long, dark brown. Seed wings articulate, effective, (8-)10-14 × 4-6 mm, light yellow- or grey-brown (Farjon and Styles 1997).

On two occasions, at a site in Jalisco and near Tepehuanes in Durango, trees have been found that had stiff, spreading leaves 14-15 cm long (Perry 1991, Farjon and Styles 1997).

Distribution and Ecology

Mexico: Aguascalientes, Chihuahua, Durango, Guanajuato, Jalisco, Nayarit, Sinaloa, Sonora, Zacatecas; throughout, in the Sierra Madre Occidental. It occurs at elevations of (1500-)1700-2600(-2900) m, which corresponds to the lower and middle slopes of the Sierra Madre. The climate is summer-wet with 500-600 mm precipitation (Farjon and Styles 1997). Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001). See also Thompson et al. (1999).

Pinus lumholtzii usually grows with several species of (predominantly evergreen) Quercus and assorted pines that may include P. leiophylla (both subspecies), P. arizonica, P. douglasiana, P. durangensis, P. herrerae, P. pseudostrobus, P. teocote, P. oocarpa and, on the driest sites, P. cembroides. On the wetter western slopes of the Sierra Madre it can be found in mixed pine forest with P. ayacahuite, P. maximinoi, P. montezumae, and sometimes Pseudotsuga menziesii subsp. glauca. (personal observations, Durango and Sinaloa, 2007.02 and Farjon and Styles 1997).

Remarkable Specimens

Ethnobotany

Indigenous people use the trunk and branches to make tools (Sierra Madre Alliance 2007). Although some populations have been overexploited for timber production, it is generally not an economically significant species (Farjon and Styles 1997).

It has seen limited, recent use in developing dendroclimatic reconstructions of drought. I can only find a record of one chronology, developed at Bolaños, Jalisco (Luckman 2005, Villanueva-Diaz et al. 2006).

Observations

I have seen this tree at several locations along the highway from Durango to Mazatlan. I saw a few trees at kilometer 51 out of Durango, which is a very dry site dominated by P. leiophylla subsp. chihuahuana and P. pseudostrobus; there may have been a few P. cembroides there as well. The tree is much more common and better developed on the wetter western slopes between Espinoza del Diablo and the Durango/Sinaloa border, where it occurs with more mesic pines such as P. herrerae and P. maximinoi, and this is where the photos shown here were taken. It is a singularly graceful tree, in my opinion perhaps the most attractive of all the Mexican pines, and it is surprising that it is not more common in cultivation.

Remarks

P. lumholtzii is parasitized by the mistletoe Cladocolea cupulata Kuijt (Loranthaceae) (Kenaley and Mathiasen 2006) and the dwarf mistletoes Arceuthobium gillii and A. nigrum (Hawksworth and Wiens 1996).

Citations

Luckman, B.H. 2005. Assessment of Present, Past and Future Climate Variability in the Americas from Treeline Environments. IAI CRN03 Final Report 2005. http://www.cricyt.edu.ar/iai/IAICRN03Finalcomplete.pdf, accessed 2007.04.25, now defunct.

Robinson, B.L. and M. L. Fernald. 1894. New plants collected by Messrs. C. V. Hartman and C. E. Lloyd upon an archeological expedition to northwestern Mexico under the direction of Dr. Carl Lumholtz. Proc. Amer. Acad. Arts 30:114-123 (p. 122).

Villanueva-Diaz, J., J. Cerano-Paredes, D.W. Stahle, B.H. Luckman, M.D. Therrell, and M.K. Cleaveland. 2006. The climatic response of tree-ring chronologies in the Sierra Madre Occidental, Mexico. Pp. 91-92 in Symposium on Climate Change: Organizing the Science in the American Cordillera. ABSTRACTS. http://www.sacc.org.uy/saccdocs/CONCORDAbstMendoza2006.pdf, accessed 2007.04.25, now defunct.

See also

Carvajal, S., and R. McVaugh. 1992. Pinus L. Pp. 32-100 in R. McVaugh, Flora Novo-Galiciana 17. Ann Arbor: University of Michigan Herbarium.