Distribution

USA: mainly California, in two disjunct (sub)populations in northern (Klamath Mts.) and in southern (Sierra Nevada) California. One locality of the northern (sub)population is just across the state border in Oregon (Lanner 2007).

The total number of mature trees is not known, but the population is fragmented, first by a gap of nearly 500 km between the northern and southern (sub) populations, and second by the fact that individual stands are (widely) scattered within these two areas. Numbers of trees in each of these stands vary between a few score to many hundreds. Regeneration and growth to maturity are extremely slow in most stands and may be episodic; this means that if little or no regeneration is observed in a stand at present this will not be evidence of decline. A tree that lives for several millennia only needs to produce offspring a few times in that whole period to replace itself and maintain the population.

Habitat and Ecology

Pinus balfouriana occurs in the subalpine to alpine zones of the Klamath Mountains (the northern [sub]population) and of the southern Sierra Nevada (the southern [sub]population). In the north it is found at altitudes of between 1,600 m and 2,400 m a.s.l., in the south between 2,900 m and 3,700 m. Stands of this pine are very open and occur on dry, rocky, exposed high slopes and ridges, usually devoid of other significant vegetation. Southern high elevation stands may be pure or mixed with P. albicaulis and sometimes Juniperus occidentalis. At lower elevations it may be less common and associated with California red fir (Abies magnifica var. magnifica), Sierra juniper (Juniperus occidentalis ssp. australis), Sierra lodgepole pine (Pinus contorta var. murrayana), Jeffrey pine (P. jeffreyi) and limber pine (P. flexilis).

Northern foxtail pine generally dominates on subalpine serpentine soils. Whitebark pine or mountain hemlock (Tsuga mertensiana) may associate on upper-elevation sites, although they are more common on nonserpentine soils. Northern foxtail pine communities on serpentine, other ultramafic or dry soils often form a mosaic with whitebark pine-mountain hemlock or mountain hemlock-Brewer spruce (Picea breweriana) communities that occur on nonserpentine or wetter,
north-slope soils. Jeffrey pine and Sierra lodgepole pine may associate on dry (south and west aspects), mid-subalpine sites (<2,200 m), while Shasta red fir (Abies magnifica var. shastensis) and western white pine may associate on wetter, mid-subalpine sites. Western white pine or white fir (A. concolor) associate on lowest-elevation subalpine sites. Incense-cedar (Calocedrus decurrens) and coast Douglas-fir (Pseudotsuga menziesii var. menziesii) may be occasional associates at these lower elevations. Northern foxtail pine communities merge with coast Douglas-fir, Sierra lodgepole pine, or mixed-conifer forest communities at their lowest elevations and with alpine fell-field or alpine meadow communities at highest elevations (Fryer 2004 and references within).

Regeneration and growth are extremely slow and stands commonly look as if entirely composed of veteran trees of great age. Regeneration is probably episodal and may be linked with climatic cycles. The oldest known Foxtail pine is estimated to be 3,400 years. This species does not have the longevity of the closely related P. longaeva, as it grow on wetter sites, has a faster growth rate and develops heart rot sooner. Southern Foxtail pines are longer lived than those in the north (Fryer 2004 and references within).

Conservation Status

Global Status

Near Threatened

Global Rationale

Based on comprehensive sampling of specimens held in herbaria in California and elsewhere, and the fact that very few if any stands of this species would have an area of occupancy (AOO) larger than 4 km² an AOO of only 136 km² was calculated. There are two main areas, separated by nearly 500 km, but the northern area has two locations, one with a much smaller subpopulation than the other. Fragmentation and number of locations therefore also fall within the threshold for Endangered; however, the population appears to be stable at present and there is no evidence of past decline within the last few hundred years. Climate change, white pine blister rust and air pollution (the latter most relevant to the southern subpopulation) are potential threats. It is therefore appropriate to list this species as Near Threatened (almost qualifies for listing under criterion B2ab).

Climate change is likely to impact the northern stands more than the southern as they already occupy the relatively few high elevation peaks leaving little room for upward expansion. In the south there are 'ghost' forests of dead Foxtail pines that are interpreted to have existed during previous periods of global warming. As such they inidcate potential room for upslope expansion.

Foxtail pines are very susceptible to White Pine Blister Rust and several stands in its northern distribution have been impacted (Kleijunas and Dunlap 2006). The southern stands have yet to show signs of infection (Maloney 2011). Both areas are affected by Mountain Pine Beetle although Foxtail pines shows relatively higher resistance than other high altitude white pines (Bentz et al. 2016)

Conservation Actions

This species is mostly present within protected areas, including famous national parks like Kings Canyon and Sequoia N.P. Programmes to identify trees resistant to White pine blister rust are being undertaken and range wide cone collections have been made to initiate ex-situ conservation.