Plants shown to be genetically distinct from the type (differences in chemistry, form, foliage, cone orientation, and seeds) have been called Pinus balfouriana subsp. austrina R.Mastrogiuseppe & J.Mastrogiuseppe. As in several other species or species complexes in Pinus , however, there is a problem with a character gradient involving related taxa. The evidence presented by D.K. Bailey (1970) and later by R.J. Mastrogiuseppe and J.D. Mastrogiuseppe (1980) could as well be used to indicate that P . balfouriana (with its two infraspecific taxa) and P . longaeva represent a single species of three subspecies or three varieties. The more conservative view of Bailey is followed here.
Foxtail pine is a native conifer. It is a low-growing pine, generally 20 to 50 feet (6-15 m) tall, but occasionally reaching 72+ feet (22+ m) in height [39,77]. The champion tree is a northern foxtail pine on the Trinity National Forest that measures 76 feet (23 m) in height, 34 feet (10 m) in spread, and 26.3 feet (8 m) in circumference [2]. Foxtail pine's trunk is usually single-stemmed. Unlike other North American conifers, foxtail pine rarely assumes krummholz form at high elevations; instead, it retains a straight bole [8,10,83,84]. Bark of mature foxtail pine is "exceptionally thick" [8]: nearly as thick as that of ponderosa pine (Pinus ponderosa). Bark thickness measurements of 1.85 inches (4.70 cm) [46] and 2.4 to 3.1 inches (6-8 cm) [8] are reported for mature foxtail pines. Mature tree crowns are 8.5 feet (2.6 m) or less in diameter. Branches are short and thick in diameter [39,77]. Branching habit is sparse in southern foxtail pine [60]; southern foxtail pine also tends to be self-pruning. Northern foxtail pine branches tend to be thicker, and may extend to the ground [6,39,68] (the photos in the Introductory section illustrate this difference). Foxtail is a 5-needle pine. The Balfourianae complex is unique among pines in that about half of their branches originate from within the needle fascicles [24,60]. Needle clusters are thickly set toward the branch ends, resembling foxtails [59]. Needles persist for 5 to 7+ years [65,71]; trees at lower elevations tend to retain needles longer than trees at timberline [65]. Female cones are 2.4 to 7.5 inches (6-19 cm) long, dehiscent, and have tiny prickles. Seeds are small (~0.3 inch (8 mm) long), with detachable seed wings about 3 times longer than the seeds [39,77]. Northern foxtail pines tend to have heavier cones and larger seeds with longer seed wings than southern foxtail pines [67].
Morphological differences between southern foxtail pine, northern foxtail pine, and Great Basin bristlecone pine are slight. Southern foxtail pine has thinner bark that tends to grow in square plates (pictured above right) compared to northern foxtail pine, which has relatively thicker bark that tends to grow in narrow ridges. Southern foxtail pine retains its needles longer than northern foxtail pine [39]. Northern foxtail pine tends to have a fuller crown and suffer from less cambial die-back than southern foxtail pine [60]. Great Basin bristlecone pine is distinguished from foxtail pines by having relatively longer cone prickles (2-6 mm) compared to foxtail pines (<1mm). Distributions of Great Basin, southern foxtail, and northern foxtail pines do not overlap [39,62], so distinguishing among them in the field is easy.
Stand structure: Foxtail pine communities are typically open, with a sparse understory and scattered woody debris. Arid, high-elevation conditions allow woody debris to persist for many years without decaying [44]. In Sequoia-Kings Canyon National Park, southern foxtail pine grows in widely spaced woodlands in its upper elevational range and is often the only tree species. At lower elevations it forms a more dense forest, either in mixed or monospecific stands [10,12,82,83]. The foxtail pine-alpine ecotone is usually abrupt as a result of foxtail pine's inability to form krummholz [64]. Northern foxtail pine communities tend toward greater density then southern foxtail pine communities [83]. In the Klamath Ranges, stand densities of northern foxtail pine communities ranged from a minimum of 51 trees/ha in the Yolla Bolly Mountains to a maximum of 381 trees/ha in the Trinity Mountains [30]. Stand densities of southern foxtail pine communities in Sequoia-Kings Canyon National Park range from 50 trees/ha to 600 trees/ha [30,64,81,83]. Ryerson [83] found a mean stand density of 100 trees/ha on sites across southern foxtail pine's distribution.
A southern foxtail pine-Sierra lodgepole pine woodland in the Golden Trout Wilderness. U.S. Forest ServiceAge class: Age class structure within foxtail pine stands appears mixed [30,69]. Few studies have been conducted on age class distributions in foxtail pine. In a study across the Klamath Ranges, Eckert and Sawyer [30] found northern foxtail pines less than 100 years of age were most common (>50% relative density). A few very old trees (around 1,000 years of age) were scattered within all the study sites. In a study across southern foxtail pine's distribution in the Sierra Nevada, Ryerson [83] found most trees were in the 350- to 500-year-old class, followed by trees less than 200 years old, and trees older than 800 years, respectively.
Foxtail pine is a very long-lived conifer, although it does not approach the extreme ages of Great Basin bristlecone pine. Foxtail pine occurs on wetter sites than bristlecones; consequently, foxtail pines show relatively faster growth, develop heart rot, and die more quickly than bristlecone pines [8]. Foxtail pine has advanced heart rot by 1,000 years of age. The oldest foxtail pine on record (as of 2004) is a 3,400-year-old southern foxtail pine [83]. Northern foxtail pines occur in wetter habitats then southern foxtail pines and are shorter lived, attaining maximum ages of about 1,600 years [30,69,83].
Physiology: Its relative inability to withstand cold may partially explain foxtail pine's narrow distribution compared to its more widely distributed high-elevation associate, whitebark pine. Poor ability to form krummholz limits foxtail pine's ability to withstand ice blasting [13]. Its seedlings are less resistant to freezing than whitebark pine seedlings [83].
Fire adaptations: Foxtail pine has many characteristics of a fire survivor [88]. Some of its morphological characteristics are similar to ponderosa pine, a highly fire-adapted species [4]. Like ponderosa pine, foxtail pine is a long-lived tree with a large-diameter bole, thick bark, and large-diameter branches [8,46]. Branches are generally sparse and self-pruning in southern foxtail pine, although thin branching and a self-pruning habit are less common in northern foxtail pine [39,60,68]. Few fire studies on foxtail pine have been conducted; however, Ryerson [83] found mature, fire-scarred southern foxtail pines throughout the tree's distribution. As further evidence of foxtail pine's ability to survive fire, Keifer [49] reported that in the Sierra lodgepole pine-southern foxtail pine ecotone in Sequoia-Kings Canyon National Park, foxtail pines were uneven-aged and showed multiple fire scars, while Sierra lodgepole pines were even-aged and showed no evidence of scarring. More fire history studies are needed on foxtail pine.
Foxtail pine seedlings pioneer on burned sites. The seeds are small, light, and have large wings [39,71,77], suggesting the possibility of foxtail pine seed dispersal onto burns from on- and off-site parent trees. In Sequoia-Kings Canyon National Park, Ryerson [83] found southern foxtail pine seedlings on 2 burned sites. On the 1st burn, seedlings established near 4 lightning-killed, mature trees. On the 2nd burn, foxtail pine seedlings grew in openings created when fire burned across a ridgetop. Further studies are needed on patterns of foxtail pine seed dispersal and seedling establishment after fire.
FIRE REGIMES: Fires are infrequent, and are generally of low severity, in subalpine regions of the southern Sierra Nevada. Scant litter production and discontinuous fuels do not promote fire spread in foxtail pine communities. Fire intensity tends to decrease when lower-elevation fires burn into southern foxtail pine. Fire spread slows; or, fires may extinguish due to lack of fuels [10,20,21,50,66]. Although foxtail pine sites receive more lightning strikes than lower-elevation forests, ignitions are uncommon [104,105]. Rocky, highly dissected foxtail pine habitats rarely sustain large fires. In a fire history study, Keifer [49] found frequent fire in Sierra lodgepole pine, but only occasional fires in southern foxtail pine sites. The National Park Service [103] classifies fire occurrence as "very low" in subalpine conifer zones of Sequoia-King Canyon National Park, with a mean fire-return interval of 187 years and a maximum recorded fire-return interval of 508 years. Caprio and Lineback [21] found southern foxtail and whitebark pine communities of Sequoia-Kings Canyon National Park had the longest return fire intervals of all plant communities in the Park. Estimated area burned in southern foxtail pine communities averaged 145 acres/year (168 ha/yr) with a mean fire-return interval of 187 years. Estimated burn area extended to 153 acres/year (62 ha/year) under the maximum mean fire-return interval of 508 years. Fire scar data from 2 watersheds show few fires in foxtail-whitebark pine communities of Sequoia-Kings Canyon National Park from 1700 to 2000: 7 on north aspects and 3 on south aspects [19]. Differences in fire-return intervals between aspects were not significant [18].
This foxtail pine stand in the John Muir Wilderness lacks sufficient fuels to carry a surface fire. U.S. Forest ServiceThe fire ecology of upper subalpine zones of California is poorly understood [103]. This is particularly true for northern foxtail pine, for which fire ecology and fire regime information are nearly absent. Thornburgh [96] found white fir-mountain hemlock communities of the Marble Mountains, where northern foxtail pine is an associate, experience a regime of mixed low- and moderate-severity fires. Fire effects and postfire recruitment of foxtail pine were not reported. Further documentation and research are needed on the fire ecology of foxtail pine and other subalpine communities of California.
Occasionally, large, stand-replacing fires occur in southern foxtail pine [92]. For example, The 1949 Kern Canyon 2 Fire burned 1,100 acres (445 ha) of southern foxtail and Jeffrey pine habitat in Sequoia-Kings Canyon National Park. Ignited by lightning on 13 July, it was controlled by 31 July. Southwesterly winds up to 40 mph (64 km/hr) caused crowning and spotting. Steep, rugged terrain contributed to fast fire spread and resistance to control [10].
Fuels: Foxtail pine snags and woody debris are highly resinous, and are slow to decay in high-elevation habitats. In Sequoia-Kings Canyon National Park, downed foxtail pines that have been dead for over 1,000 years still retain medium-sized (>0.8-inch (2-cm) diameter) or larger branches [63]. Foxtail pine communities are not typically highly flammable though, because woody fuels are limited and discontinuous [66,92], and litter is sparse [82]. Live fuels are also scant. A 1978 fuel inventory in Sequoia-Kings Canyon National Park showed a mean of 10 tons/acre in foxtail and other subalpine types [10]. Basal area and litter quantity decreased with elevation, although litter quality (N:C ratio) increased with elevation [65]. The live understory is typically sparse in foxtail pine communities. Lloyd and Graumlich [64] found less than 1 plant/m² in southern foxtail pine understories in Sequoia-Kings Canyon National Park. Van Wagtendonk and others [107] reported the following fuelbed characteristics for southern foxtail pine:
Woody fuel depth Litter depth Duff depth Litter & duff depth 1.24 cm 0.19 cm 1.60 cm 1.79 cmQuantitative measures of physical fuel properties such as surface-to-volume ratios are used in fuel models. By fuel size class, van Wagtendonk and others [106] provide mean surface-to-volume ratio, diameter and squared quadratic mean diameter, and angles of inclination tables for southern foxtail pine and other Sierra Nevada conifers.
The following table provides fire-return intervals for plant communities where foxtail pine occurs. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Community or Ecosystem Dominant Species Fire-Return Interval Range (years) whitebark pine Pinus albicaulis 50-200 [1,3] Sierra lodgepole pine Pinus contorta var. murrayana 35-200 [5] mountain hemlock Tsuga mertensiana 35 to > 200 [5] Fire-return intervals for these species vary widely; trends in variation are noted in the species reviews.Foxtail pine is adapted to harsh environmental conditions [60,71]. Its long life span, slow growth, and persistent needles are typical of conifer species adapted to stressful habitats [71]. Foxtail pine holds an ecological position between whitebark pine and limber pine: it is less tolerant of cool, short growing seasons than whitebark pine and less tolerant of warm, arid growing conditions than limber pine [44,87]. North of southern foxtail pine's distribution in the Sierra, freezing temperatures occur all year long [83]. Foxtail pine communities are most common on "safe sites," such as ultramafic soils and dry granite fields, that few other conifer species can tolerate [30,60]. Slope varies from gentle to as much as 55% [83,84].
Southern foxtail pine grows on well-drained, decomposed granite and granite boulder fields. Southern foxtail pine does not occur on serpentine or other ultramafic soils, which are rare in the high Sierra Nevada [52,55,83]. It is more common on the drier, eastern side of the Sierra Nevada, while whitebark pine is more common on the west slope [10,83]. Climate in the southern Sierra Nevada is mediterranean, with cold winters and warm, dry summers [68,87]. Annual precipitation on the east slope ranges from 20 to 30 inches (500-750 mm) [13]. Southern foxtail pine occurs from 8,900 to 12,000 feet (2,700-3,700 m) elevation [39]. Tree damage from ice- and sandstorms is common [68]. Highest density of southern foxtail pine occurs on north-facing slopes; least density is on south slopes. Percent slope across southern foxtail pine's range averages less than 33% [83].
Habitat of northern foxtail pine is even more restricted than that of southern foxtail pine. The Klamath Ranges are geologically complex, consisting of steep elevational gradients and a variety of parent rock materials that strongly influence plant community boundaries [52]. Climate is mediterranean, but is strongly moderated by the maritime influence of the nearby Pacific Ocean [68]. Annual precipitation averages from 49 to 60 inches (1,250-1,750 mm) [13]. Northern foxtail pine occurs from 6,900 to 8,200 feet (2,100-2,500 m) elevation [39]. There are relatively few high-elevation peaks in the Klamath Ranges; therefore, northern foxtail pine tends to segregate into small populations on isolated "sky islands" [78]. Substrates on which northern foxtail pine grows include gabbro, granodiorite, limestone, schist, and most commonly, serpentine [52,55,60,87]. Because most associated conifers (except Jeffrey pine) are less tolerant to them, serpentine soils can partially ameliorate the elevational restriction and lower northern foxtail pine's elevational distribution. Northern foxtail pine tends to grow in large, monospecific stands when on serpentine soils. On other substrates it is generally found in small stands (a few hundred trees) on ridge crests, mountain tops, and steep, south- or west-facing slopes [30,69,78,87]. Populations on serpentine soils are more likely to occur on all aspects, including valley bottoms and lake shores [78]. Percent slope ranged from 15-32% on 4 sites in the Klamath Ranges [83].
Southern foxtail pine is the dominant conifer in upper-elevation
subalpine communities of the south-central Sierra Nevada [12,81,108]. It is the
most abundant subalpine conifer in Sequoia-Kings Canyon National Park
[10]. Southern foxtail pine often occurs in pure
stands [64]. 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) may associate on low-elevation foxtail pine sites, while whitebark pine
(P. albicaulis) may associate on high-elevation sites [82,83,108]. The most common
shrub associates in
southern foxtail pine communities are bush chinquapin (Chrysolepis sempervirens),
oceanspray (Holodiscus discolor), wax currant (Ribes cereum), gooseberry currant (R. montigenum),
Parish's snowberry
(Symphoricarpos rotundifolius var. parishii), and curlleaf mountain-mahogany
(Cercocarpus ledifolius) [83,84]. Pinemat manzanita (Arctostaphylos nevadensis),
green manzanita (A. patula), and bitter cherry (Prunus emarginata) may also be present [10,83].
In Sequoia-King Canyon National Park, Vankat [108] found less than one-fourth of southern foxtail pine communities
contained shrubs. Herbaceous cover averaged around 10%, although some stands showed
as much as 65% herbaceous cover. Tree cover was almost entirely foxtail pine; a few stands also had Sierra lodgepole pine.
Bush chinquapin and
oceanspray were the most common shrubs. Shrub associates are more common on marginal foxtail pine
sites than in Sequoia-Kings Canyon, which is prime foxtail habitat. Southern monardella (Monardella australis)
is the most consistent herbaceous associate across southern foxtail pine's range [83]. At their lowest elevations,
southern foxtail pine communities merge with upper-elevation Sierra lodgepole pine or, more rarely,
east-slope Jeffrey pine
communities. Southern foxtail pine communities often
form a mosaic with subalpine meadows [15]. At their highest elevations, southern foxtail pine communities merge into
alpine meadows and fell-fields [44].
The Klamath Ranges support some of the most diverse plant communities in North
America [87], and northern foxtail pine contributes to this diversity. Northern foxtail communities are
typically more diverse compared to southern foxtail pine communities [68]. Eckert and Sawyer [30] found that
along a latitudinal gradient, diversity of northern foxtail pine communities increased
to the north. Lowest diversity occurred in the southern Yolla Bolly Mountains, the
southernmost of the Klamath ranges, while highest diversity occurred in the
Trinity and Marble mountains, the northernmost of the Klamath ranges.
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 [30,83]. 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 [30,44,55,64]. 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 [30,38,44,55,68].
Western white pine or white fir (A. concolor) associate on lowest-elevation
subalpine sites [23,87]. Incense-cedar (Calocedrus decurrens) and
coast Douglas-fir (Pseudotsuga menziesii var. menziesii) may be
occasional associates at these lower elevations [68,83]. 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 [44,64].
In the Trinity Mountains on the Siskiyou-Trinity county line, northern foxtail pine occurs
in pure stands at timberline.
Shasta red fir, western white pine, and Jeffrey pine associate on mid-subalpine
sites. Trinity
buckwheat (Eriogonum alpinum), pinemat manzanita, big sagebrush (Artemisia tridentata), and
huckleberry oak (Quercus
vaccinifolia) occur in the understory. Ground-layer associates include cobwebby paintbrush (Castilleja arachnoidea),
Cascade aster (Eucephalus
ledophyllus), spreading phlox (Phlox diffusa), and bottlebrush
squirrel (Elymus elymoides) [23,87]. Unusually diverse northern foxtail
communities exist on China and Russian peaks, where northern foxtail pine
associates with Jeffrey pine, incense-cedar, and Pacific Douglas-fir [86].
Damaging bioagents:
Foxtail pine is highly susceptible to white pine blister rust,
a usually fatal fungal disease that affects 5-needle pines [40,72,85].
In the greenhouse, Hoff and others [40] inoculated 18 species of Eurasian and
North American 5-needle pine seedlings with blister rust. Of the 18 species,
foxtail and southwestern white pine (Pinus strobiformis) showed least
resistance to blister rust. All of the 92 inoculated foxtail pines became
infected. Other studies show a 75-100% seedling infection rate [94]. Although the
mediterranean climate of California once protected all but the northernmost populations of 5-needle pines from blister
rust, that is no longer true. Some northern foxtail pines on the Scott River
District of the Klamath National Forest have blister rust [97,99,101].
As of this writing (2004), blister rust has not been detected in southern
foxtail pine, although western white pine and sugar pine (P. lambertiana)
in Sequoia-Kings Canyon National Park are infected [85,101].
Blister rust-infected trees may take from 2 years to decades to succumb, but
infection is always fatal [41,42].
Gooseberries and currants (Ribes spp.) are the primary host of white
pine blister rust. Life cycle of white pine blister rust is complex.
Gitzendanner and others [35]
and McDonald and Hoff [72]
provide details of the rust's life history and ecology. Hoff [41]
provides a diagnostic guide to aid managers in recognizing symptoms of blister
rust infection in white pines. There are no known methods of controlling blister
rust [48]. Fungicide application, pruning infected tree branches, and/or
removing Ribes spp. have neither eliminated nor controlled white pine
blister rust [22,72], and such treatments have undesirable ecological effects
[48]. For further information on management of white pine blister rust, see Samman and
others [85].
Some northern foxtail pines on the Scott River District show phenological
resistance to blister rust. Identification and breeding programs for these
genetically valuable, blister-rust resistant individuals are crucial to an
integrated strategy for protecting and restoring foxtail and other white pines
[40,72,85]. Breeding programs for blister rust-resistant foxtail pines
are being implemented [101].
Other damaging bioagents:
Foxtail pines are susceptible to
mountain pine beetle attacks [109]. Two rare species of Pityophthorus
bark beetles may feed primarily on foxtail pine [17]. While contributing to
biodiversity, little is known of the impacts of these Pityophthorus bark beetles to foxtail
pine. Limber pine dwarf-mistletoe (Arceuthobium cyanocarpum) occasionally
infects foxtail pine [51,70,74]. A fungal needle cast (Lophodermium
durilabrum) has caused minor damage to northern foxtail pines in the
Marble Mountains [73].
Climate
affects foxtail pine's elevational range. For most of the period for
which tree records are available (~3,500 years), southern foxtail pine
has existed above present treeline [63,64]. For example, Vankat
[108] found dead stands of foxtail pine above present timberline (10,800-
11,200 feet (3,300-3,400 m))
on the Kern River Watershed in Sequoia-Kings Canyon National Park. These "ghost
forests" may be relicts of foxtail pines that died during a period of global
warming [57]. Lloyd
and Graumlich [64] documented 3 episodes where southern foxtail pine expanded
upslope. Although the data are somewhat unclear [56,90], these
expansions appear to have occurred during relatively warm, wet periods. Presently, southern foxtail pine is expanding its
range both upslope and laterally into subalpine meadows and previously untreed
east slopes. This expansion has been explained as a response to global
warming [63,65], or due to a combination of factors including global warming, low conifer
diversity (and consequent lack of growth interference for foxtail pine in the upper elevations
of the southern Sierra Nevada), and stochasticity [69,83,89].
Foxtail pine is an ecologically important species. The open structure of foxtail pine stands slows snowmelt and helps retain snowpack. Foxtail pine also helps stabilize soil on steep subalpine slopes [85,93].
As a long-lived conifer, foxtail pine is a valuable species for dendrochronological and related climate studies [33,36,37,89,90].
Wood Products: Foxtail pine is rarely harvested [83] and is not commercially important [93].
Foxtail pine's thick bark helps protect it from damage from surface fires. Sparse, large-diameter branches discourage torching and fire spread. Little is known about foxtail pine's response after the fire has passed. In the 1979 Fire Management Plant for Sequoia-Kings Canyon National Park, Bancroft [10] wrote "Very little research has been conducted on the effect of fire on natural regeneration in subalpine forests." This remains true of foxtail pine and other subalpine forests today. Research is needed on the fire ecology of foxtail pine.
Kiefer [49] found foxtail pine recruitment in Sequoia-Kings Canyon National Park was uneven-aged and did not appear to be correlated with fire history. This was in sharp contrast to associated Sierra lodgepole pine, whose recruitment dated from past fires. Kiefer suggested that climate may play a more important role in foxtail pine recruitment than fire.
Environmental interactions that foster foxtail pine recruitment are poorly understood. Climate and water balance may be the primary factors driving foxtail pine establishment, with best recruitment during periods of warm, wet winters and cool summer temperatures [33,36,37,63]. Dendrochronologists studying a 3,500-year history of southern foxtail pine recruitment and death rates in Sequoia-Kings Canyon National Park found 2 periods of poor southern foxtail pine recruitment. The 1st was during a drought lasting decades (950-550 years BP); the other was an extended period of below-average temperatures (450-50 years BP). Death rate was relatively stable over the last 1,000 years, averaging about 0.05% per capita. Death appeared to be due to local or endogenous factors except during periods of extreme climate fluctuation. Mortality spiked during the periods of extended drought and extended cold. Overall recruitment rate was slightly higher than death rate, averaging around 0.06% per capita [63,64]. As of this writing (2004), field studies on the seed germination and seedling establishment stages of foxtail pine's life cycle are lacking. Further studies are needed on the regeneration requirements and life cycle of foxtail pine.
Barriers to regeneration: Domestic livestock grazing may adversely affect foxtail pine regeneration in areas where grazing is still practiced. Vankat [108] found southern foxtail pine in Sequoia-Kings Canyon National Park showed a pulse of recruitment from 1890-1895. That period coincides with a period of reduced domestic sheep grazing in the southern Sierra Nevada.
White pine blister rust (Cronartium ribicola) affects the ability of 5-needle pines to reproduce by killing cone-bearing branch tips. An infected northern foxtail pine population on the Klamath National Forest (see Other Management Considerations) shows poor recruitment, although it is uncertain at this time if blister rust is responsible. Levels of blister rust infection in foxtail pine are being monitored [101].
Breeding system: Allozyme surveys show that genetic diversity is low in foxtail pine compared to other pine species. There is more genetic differentiation among than within populations. Interpopulation genetic diversity is particularly pronounced in northern foxtail pine, which tends to have small (300-600 individuals), isolated populations, and restricted between-population gene flow. Natural selection for serpentine tolerance, global warming (see Other Management Considerations, Climate), and genetic drift have likely contributed to northern foxtail pine's low genetic diversity [78].
Pollination: Foxtail pine is wind pollinated [60].
Seed production: Foxtail pine 1st produces cones at 20 to 50 years of age [53,83]. The cone cycle (development through maturity) takes 5 to 6 years [28]. There is usually a 5- to 6-year interval between large cone crops [53]. Environmental conditions promoting large crops are undocumented (as of 2004).
Seed dispersal: Foxtail pine seed is dispersed by wind [59,60]. How long seed is retained in the cone, and whether it survives fire and disperses from cones onto burns, is poorly documented (as of 2004). Likewise, average range of dispersal for wind-blown foxtail pine seed is unknown, making it difficult to predict the potential for long-range foxtail pine seed dispersal onto burns or other open seedbeds.
Although Clark's nutcrackers disperse bristlecone pine seeds, there have been no sightings of the Clark's nutcrackers dispersing foxtail pine seeds [61,71]. Trees growing from Clark's nutcracker caches often have multiple, genetically distinct stems [59,60]. The typical single-stemmed habit [8,10,83] of foxtail pine suggests that Clark's nutcracker dispersal and caching is unusual. Ryerson [84], however, noted the presence of a few multiple-stemmed trees throughout foxtail pine's distribution, suggesting the possibility of Clark's nutcracker seed dispersal and caching. Tomback and others [98] suggested that Clark's nutcrackers may disperse some foxtail pine seed, and that rodents may act as secondary dispersers. Fryer observed Clark's nutcrackers collecting seed in the John Muir Wilderness (see photo below). Genetic identities of multiple-stemmed foxtail pine "individuals" had not been determined as of 2004. Further investigation is needed on mechanisms of seed dispersal for foxtail pine.
Clark's nutcrackers in a southern foxtail pine in the John Muir Wilderness. U.S. Forest ServiceSeed banking: No information is available on this topic.
Germination: Seeds require stratification [25,28]. Fresh, stratified southern foxtail pine seed collected in Sequoia-Kings Canyon National Park showed 86% germination. After 9.4 years in cold storage, the same seed lot showed 72% germination [76].
Seedling establishment/growth: Based on limited information, foxtail pine seedling establishment appears to be episodic, occurring during periods of mild, wet winters [63,83].
Southern foxtail seedlings, saplings, and mature trees in the John Muir Wilderness. U.S. Forest ServiceFoxtail pine is a slow-growing conifer [60,71]. Best growth of southern foxtail pine occurs in years with relatively warm, wet winters and cool summers [33,36,37,63]. Studies on growth rates of foxtail pine are limited. One study found relative height growth rates of 0.2 to 0.9 inch (0.5-2.3 cm) per year for seedlings in Sequoia-Kings Canyon National Park. Seedlings in open, high-elevation sites tended to grow taller than seedlings in lower-elevation, forested areas [93]. For mature trees, another Sequoia-Kings Canyon study found trees at lower elevations (<8,200 feet (2,500 m)) had greater relative growth rates compared to trees at high elevations (>9,800 feet (3,000 m)). Relative growth rates were 6.7-9.1 inches/100 years compared to 2.4-3.1 inches/100 years (17-23 cm/100 yrs vs. 6-8 cm/100 yrs), at low and high elevations, respectively [83].
Foxtail pine is shade intolerant, requiring open, sunny locations throughout its life cycle [8,9,83,87]. Foxtail pine pioneers on serpentine and high-elevation subalpine sites [30]. It competes poorly on nutrient-rich, mesic, and low-subalpine sites [78,87]. Foxtail pine is generally noninvasive [80]; however, it has extended its distribution into the California red fir zone in times of global cooling [83]. On high-elevation, ultramafic or dry granitic sites, foxtail pine is not threatened by successional replacement by shade-tolerant conifers such as California red fir and mountain hemlock because no other tree is as well adapted to the harsh sites that foxtail pine occupies [14,30]. On more favorable sites, successional replacement of foxtail pine by mountain hemlock and firs may be occurring. Research is needed on successional patterns in foxtail pine communities on mesic, nonserpentine sites.
A resurvey in Sequoia-Kings Canyon National Park showed that in 27 years, southern foxtail pine basal area and cover increased 8% and 16%, respectively. The changes were entirely due to foxtail pine diameter growth; in 27 years there had been no foxtail pine mortality, and no ingrowth of foxtail pine or other tree species, on the study plots [81]. To date (2004), there are no studies of succession in foxtail pine communities following fire, avalanche, or other disturbances. Studies documenting postdisturbance recruitment and succession in foxtail pine communities are needed.
The scientific name of foxtail pine is Pinus balfouriana Grev. & Balf.
(Pinaceae). There are 2 subspecies [8,32,39,47,68]:
Pinus balfouriana subsp. austrina R.J. & J.D. Mastrogiuseppe
southern foxtail pine
Pinus balfouriana subsp. balfouriana northern foxtail pine
Foxtail pine, Great Basin bristlecone pine (P. longaeva), and Rocky Mountain bristlecone pine (P. aristata)
share a common ancestor [83,110]. Taxa within the foxtail-bristlecone pine
complex (Pinus, subgenus Strobus, section
Parrya Mayr, subsection Balfourianae Englm.) are distinguished by growth
form, bark, and differences in chemical composition
[8,25,68,76]; however,
these characters intergrade [32,39,68].
Foxtail and bristlecone pines readily produce fertile hybrids in the laboratory [93,110].
Disjunct distributions, and possibly other factors, prevent natural hybridization among the 4 taxa. Southern
foxtail and Great Basin bristlecone pine populations seem geographically close enough for
limited pollen dispersal
(see General Distribution); yet to
date (2004), southern foxtail ÃÂ
Great Basin bristlecone pine hybrids have not been found in the field
[8,60].
Pinus balfouriana, the foxtail pine, is a rare high-elevation pine that is endemic to California, United States. It is closely related to the Great Basin and Rocky Mountain bristlecone pines, in the subsection Balfourianae.
P. balfouriana is a tree to 10–20 m (30–70 ft) tall, exceptionally 35 m (115 ft), with a trunk up to 2 m (7 ft) across. Its leaves are needle-like, in bundles of five (or sometimes four, in the southern Sierra) with a semi-persistent basal sheath, and 2–4 cm (1–1+1⁄2 in) long, deep glossy green on the outer face, and white on the inner faces; they persist for 10–15 years. The cones are 6–11 cm (2+1⁄2–4+1⁄2 in) long, dark purple ripening red-brown, with soft, flexible scales each with a 1-millimeter (1⁄16-inch) central prickle.
P. balfouriana occurs in the subalpine forest at an elevation of 1,950–2,750 m (6,400–9,020 ft) in the Klamath Mountains, and at 2,300–3,500 m (7,500–11,500 ft) in the Sierra Nevada. In the Sierra Nevada, Foxtail pines are limited to the area around Sequoia and Kings Canyon National Parks. In both areas, it is often a tree line species.
There are two disjunct populations:
A small outlying population was reported in southern Oregon, but was proven to have been misidentified.[3]
It is thought that P. balfouriana can live up to 3000 years in the Sierra Nevada, although the highest currently proven age is 2110 years. In the Klamath Mountains, ages are only known to about 1000 years.
P. balfouriana is closely related to the bristlecone pines, being classified in the same subsection Balfourianae; it has been hybridised with the Great Basin Bristlecone Pine in cultivation, though no hybrids have ever been found in the wild.
Pinus balfouriana, the foxtail pine, is a rare high-elevation pine that is endemic to California, United States. It is closely related to the Great Basin and Rocky Mountain bristlecone pines, in the subsection Balfourianae.
