Common Names

Sierra Juárez pinyon, nut pine, piñon (Perry 1991).

Taxonomic notes

Subsection Cembroides. Lanner (Lanner 1974a, 1974b, 1981) regards the P. quadrifolia populations described for the Sierra Juárez as P. juarezensis-P. monophylla hybrids and segregates P. juarezensis as a 5-needle piñon endemic to the Sierra Juárez of Baja California Norte and extreme S CA, reducing P. quadrifolia to hybrid status as P. × quadrifolia Parl. Farjon and Styles (1997) regard P. juarezensis as a synonym for P. quadrifolia, discounting the idea that because P. quadrifolia displays characters intermediate between P. monophylla and P. juarezensis it must then be a hybrid. I must disagree. Lanner describes some populations of P. juarezensis -- such as that atop the Laguna Mountains in California -- that do not display hybrid characters. I have seen this species on the southern Mt. San Jacinto massif (March 2004), on the Laguna Mountains of California, at the type locality in northern Baja California, and in many areas from there south to the Laguna Hanson area of Baja California Norte (March 2001). I had the opportunity to examine trees in many ecological settings, some of which were shared by P. monophylla and others not. I found fascicles of fewer than 5 needles in all settings, but in many cases these seemed to reflect stress, as shown by the fact that fascicles with fewer needles often had shorter needles and a lower density of fascicles on the branchlet, and often were growing in the shade (i.e. the lower crown). Fully developed sun foliage had fewer than 5 needles per fascicle primarily at sites where P. monophylla was also present. A particularly good example was found on the southern Mt. San Jacinto massif, along CA highway 371 about 1 mile south of its junction with CA highway 74, where I found a large pine with almost all 2-needle fascicles, showing leaf and cone characters intermediate between P. juarezensis and P. monophylla, both of which were growing in the vicinity. Details and photos appear HERE. Also, at its type locality near La Rumorosa in Baja California, P. juarezensis grows in a mixed stand with P. monophylla, and many of the trees have a high density of fascicles with fewer than 5 needles. The type locality stand is much drier and more open than the species' usual habitat.

P. quadrifolia was widely regarded as a good species when a stand of it was planted in the native plant garden at the Rancho Santa Ana Botanical Garden in Claremont, California. I wondered how diligently they must have searched to find so many 4-needle trees. The trees have done very well in Claremont, so much so that they now form a stand as dense and dark as any thicket, virtually devoid of an understory. The offspring of these trees, if they all bore 4-needled fascicles, could deny the hybrid origin of the species; but though I searched, I could find no seedlings or saplings, nor any evidence of viable seed.

Description

"A small pine up to 15 m tall. In mature trees the crown is irregularly rounded; in young trees it is thicker and narrowly pyramidal. [Bark is] in old trees, thick, scaly, divided by longitudinal and horizontal furrows; in young trees thin and smooth. [Branchlets] light gray, rough, pubescent; bases of the leaf bracts are not decurrent. [Leaves] in fascicles of 5, rarely 4, slightly curved, 1.5-4.0 cm long, 0.5-1.5 mm thick; margins entire, stomata primarily on the ventral surfaces with an occasional row on the dorsal surface; resin canals 2, rarely 1 or 3, dorsal; fibrovascular bundle single; the leaves bright green on the dorsal surface and silver-colored (lines of stomata) on the ventral surfaces; connate (united) during the first year. Sheaths of the leaves 5-9 mm long, curled into persistent rosettes, later deciduous. [Conelets] borne singly and in pairs on slender, short peduncles; globose with thick, transversely keeled scales. [Cones] subglobose; symmetrical; 3.5-5.0 cm long, 4.5-7.0 cm wide when open; yellow to ochre colored; dehiscent; deciduous when mature, the peduncle very small and falling with the cone. [Cone scales] few; the apophysis rhomboidal, transversely keeled; the umbo dorsal, flat to depressed, bearing a minute early deciduous prickle. Only the central scales are seed-bearing. [Seeds] brown; wingless; 14-17 mm long, 6-8 mm wide; the seed coat very thin, 0.2-0.3 mm thick; the endosperm white" (Perry 1991).

Range

US: S California and Mexico: Baja California Norte. "Its principal range lies in the Sierra de Juárez and Sierra de San Pedro Mártir in Baja California Norte. [Habitat is] semi-arid to arid foothills and mesas at altitudes ranging from 1,100 to 2,000 m. Rainfall at the lower elevations generally does not exceed 500 mm annually and temperatures may drop to freezing during the winter months. At the higher altitudes (1,600-2,000 m) frosts often occur during the winter and annual rainfall may reach 600 mm with about 30% occurring in the form of snow and sleet" (Perry 1991). My field observations suggest that P. juarezensis grows in a variety of forest formations depending on available moisture. At the mesic end of the scale, it occurs as an understory tree and on locally droughty sites within Pinus jeffreyi forests having canopy closure less than 67%. As site moisture decreases, P. jeffreyi is increasingly restricted to riparian areas and then is excluded completely. At these moisture levels, P. juarezensis forms continuous stands of tens to thousands of individuals, sometimes with crown closure as high as 90%. On still more xeric sites, crown closure is lost and P. monophylla becomes an increasingly important component of the stand, as does Juniperus californica and various nonconiferous chaparral shrubs such as manzanitas (Arctostaphylos sp.). On the driest sites, P. juarezensis disappears, leaving a P. monophylla--J. californica stand. I suspect that fire is an important determinant of stand dynamics on sites with potentially high canopy closure, simply because such settings develop fuel loadings sufficient to carry a fire and the nonconiferous component is dominated by chaparral, a characteristic fire-dominated community. Within the historical era, stand dynamics are also modified by forest clearing to increase available forage for cattle.

Big Tree

No data. Trees more than 10 m tall and 30 cm dbh are unusual.

Oldest

No data, except that I have counted rings on a few stumps and found nothing exceeding 200 years. Twice that age would not be surprising.

Dendrochronology

Ethnobotany

The seeds are "sold on the market as pine nuts along with the seeds of P. edulis and P. monophylla ... Like most of the nut pines, the trunk is short and small in diameter and thus hardly useful for sawn lumber. However, it is used locally for posts and firewood" (Perry 1991).

Observations

This is an extremely common pine in the Sierra Juárez of Baja California Norte. A drive south from Mexico Highway 2 to the Parque Nacional Constitución de 1857 will take you through many kilometers of groves, and it is a common understory species at the park. It can also be seen in a pure stand near the radio transmitters at the summit of the Laguna Mountains east of San Diego. You may find these locations useful:

Nice mixed stand (with P. monophylla) at 32° 18.107' N, 115° 56.223' W, UTM = 11S 0600072E 3574382N.

Growing with a minor component of P. jeffreyi at 32° 12.158' N, 115° 56.159' W, UTM = 11S 0600281E 3563394N.

Dense single-species stand with lots of seedlings at 32° 11.298' N, 115° 55.662' W, UTM = 11S 0601080E 3561811N.

Remarks

"The rather large, thin-shelled seeds are gathered for food by birds and rodents" (Perry 1991).

See Also