|Southern foxtail pine.|
|Northern foxtail pine. Photos © 1998. Charles Webber, California Academy of Sciences.|
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 [83,109]. 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 [93,109]. 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 × Great Basin bristlecone pine hybrids have not been found in the field [8,60].LIFE FORM:
In Sequoia-King Canyon National Park, Vankat  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 . 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 . At their highest elevations, southern foxtail pine communities merge into alpine meadows and fell-fields .
The Klamath Ranges support some of the most diverse plant communities in North America , and northern foxtail pine contributes to this diversity. Northern foxtail communities are typically more diverse compared to southern foxtail pine communities . Eckert and Sawyer  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 [30,82]. 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 [30,44,54,63]. 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 [30,38,44,54,67]. Western white pine or white fir (A. concolor) associate on lowest-elevation subalpine sites [23,86]. Incense-cedar (Calocedrus decurrens) and coast Douglas-fir (Pseudotsuga menziesii var. menziesii) may be occasional associates at these lower elevations [67,82]. 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 [44,63].
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) [23,86]. 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 .Holland , Rundel and others , and Sawyer and Thornburgh  provide vegetation typings describing foxtail pine communities.
|Southern foxtail. © 1998. Charles Webber , California Academy of Sciences||Southern foxtail. © 1995. Br. Alfred Brousseau , St. Mary's College|
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 . Northern foxtail pine tends to have a fuller crown and suffer from less cambial die-back than southern foxtail pine . 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 [39,61], 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 . 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 [10,12,81,82]. The foxtail pine-alpine ecotone is usually abrupt as a result of foxtail pine's inability to form krummholz . Northern foxtail pine communities tend toward greater density then southern foxtail pine communities . 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 . Stand densities of southern foxtail pine communities in Sequoia-Kings Canyon National Park range from 50 trees/ha to 600 trees/ha [30,63,80,82]. Ryerson  found a mean stand density of 100 trees/ha on sites across southern foxtail pine's distribution.
Age class: Age class structure within foxtail pine stands appears mixed [30,68]. Few studies have been conducted on age class distributions in foxtail pine. In a study across the Klamath Ranges, Eckert and Sawyer  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  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 bristlecone pines. 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 . 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 . Northern foxtail pines occur in wetter habitats then southern foxtail pines and are shorter lived, attaining maximum ages of about 1,600 years [30,68,82].
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 . Its seedlings are less resistant to freezing than whitebark pine seedlings .RAUNKIAER  LIFE FORM:
Barriers to regeneration: Domestic livestock grazing may adversely affect foxtail pine regeneration in areas where grazing is still practiced. Vankat  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 .
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 .
Pollination: Foxtail pine is wind pollinated .
Seed production: Foxtail pine 1st produces cones at 20 to 50 years of age [52,82]. The cone cycle (development through maturity) takes 5 to 6 years . There is usually a 5- to 6-year interval between large cone crops . Environmental conditions promoting large crops are undocumented (as of 2004).
Seed dispersal: Foxtail pine seed is dispersed by wind [58,59]. 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 birds dispersing the smaller seeds of foxtail pine [60,70]. Trees growing from Clark's nutcracker caches often have multiple, genetically distinct stems [58,59]. The typical single-stemmed habit [8,10,82] of foxtail pine suggests that Clark's nutcracker dispersal and caching is unusual. Ryerson , 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. Genetic identities of multiple-stemmed foxtail pine "individuals" have not been determined. Further investigation is needed on mechanisms of seed dispersal for foxtail pine.
Seed 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 .
Seedling establishment/growth: Based on limited information, foxtail pine seedling establishment appears to be episodic, occurring during periods of mild, wet winters [62,82].
Foxtail pine is a slow-growing conifer [59,70]. Best growth of southern foxtail pine occurs in years with relatively warm, wet winters and cool summers [33,36,37,62]. 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 . 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 .SITE CHARACTERISTICS:
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 [51,54,82]. It is more common on the drier, eastern side of the Sierra Nevada, while whitebark pine is more common on the west slope [10,82]. Climate in the southern Sierra Nevada is mediterranean, with cold winters and warm, dry summers [67,86]. Annual precipitation on the east slope ranges from 20 to 30 inches (500-750 mm) . Southern foxtail pine occurs from 8,900 to 12,000 feet (2,700-3,700 m) elevation . Tree damage from ice- and sandstorms is common . 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% .
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 . Climate is mediterranean, but is strongly moderated by the maritime influence of the nearby Pacific Ocean . Annual precipitation averages from 49 to 60 inches (1,250-1,750 mm) . Northern foxtail pine occurs from 6,900 to 8,200 feet (2,100-2,500 m) elevation . 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" . Substrates on which northern foxtail pine grows include gabbro, granodiorite, limestone, schist, and most commonly, serpentine [51,54,59,86]. 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 [30,68,77,86]. Populations on serpentine soils are more likely to occur on all aspects, including valley bottoms and lake shores . Percent slope ranged from 15-32% on 4 sites in the Klamath Ranges .SUCCESSIONAL STATUS:
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 . 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.SEASONAL DEVELOPMENT:
Foxtail pine seedlings pioneer on burned sites. The seeds are small, light, and have large wings [39,70,76], suggesting the possibility of foxtail pine seed dispersal onto burns from on- and off-site parent trees. In Sequoia-Kings Canyon National Park, Ryerson  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 [10,20,21,49,65]. Although foxtail pine sites receive more lightning strikes than lower-elevation forests, ignitions are uncommon [102,103]. Rocky, highly dissected foxtail pine habitats rarely sustain large fires. In a fire history study, Keifer  found frequent fire in Sierra lodgepole pine, but only occasional fires in southern foxtail pine sites. The National Park Service  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  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 . Differences in fire-return intervals between aspects were not significant .
The fire ecology of upper subalpine zones of California is poorly understood . This is particularly true for northern foxtail pine, for which fire ecology and fire regime information are nearly absent. Thornburgh  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 . 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 .
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 . Foxtail pine communities are not typically highly flammable though, because woody fuels are limited and discontinuous [65,91], and litter is sparse . 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 . Basal area and litter quantity decreased with elevation, although litter quality (N:C ratio) increased with elevation . The live understory is typically sparse in foxtail pine communities. Lloyd and Graumlich  found less than 1 plant/m² in southern foxtail pine understories in Sequoia-Kings Canyon National Park. Van Wagtendonk and others  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 cm|
Quantitative measures of physical fuel properties such as surface-to-volume ratios are used in fuel models. By fuel size class, van Wagtendonk and others  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. For further information, see the FEIS summary on the dominant species listed below.
|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 |
|mountain hemlock||Tsuga mertensiana||35 to > 200 |
Kiefer  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.
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
No additional information is available on this topic.
FIRE MANAGEMENT CONSIDERATIONS:
Southern foxtail pine communities are managed with prescribed natural fire (wildland fire for resource benefit) . Fire may extend foxtail pine's distribution downslope on some sites , although the postfire interactions of California subalpine conifers have had too little study to predict postfire results with confidence. Fire may encourage foxtail pine recruitment and growth on existing foxtail pine sites by releasing nutrients from slow-decaying woody debris. On those relatively rare foxtail pine sites with closed canopies, fire would encourage foxtail pine recruitment by creating an open mineral seedbed.
Palatability/nutritional value: Foxtail pine seeds are palatable and nutritious, but they are not large compared to most 5-needle pines :
|Species||Mean seed weight|
|Great Basin bristlecone pine||25 mg|
|foxtail pine||27 mg|
|limber pine||93 mg|
|whitebark pine||175 mg|
Cover value: No information is available on this topic.VALUE FOR REHABILITATION OF DISTURBED SITES:
As a long-lived conifer, foxtail pine is a valuable species for dendrochronological and related climate studies [33,36,37,88,89].
Wood Products: Foxtail pine is rarely harvested  and is not commercially important .OTHER MANAGEMENT CONSIDERATIONS:
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  and McDonald and Hoff  provide details of the rust's life history and ecology. Hoff  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 . Fungicide application, pruning infected tree branches, and/or removing Ribes spp. have neither eliminated nor controlled white pine blister rust [22,71], and such treatments have undesirable ecological effects . For further information on management of white pine blister rust, see Samman and others .
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 [40,71,84]. Breeding programs for blister rust-resistant foxtail pines are being implemented .
Other damaging bioagents: Foxtail pines are susceptible to mountain pine beetle attacks . Two rare species of Pityophthorus bark beetles may feed primarily on foxtail pine . 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 [50,69,73]. A fungal needle cast (Lophodermium durilabrum) has caused minor damage to northern foxtail pines in the Marble Mountains .
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 [62,63]. For example, Vankat  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 . Lloyd and Graumlich  documented 3 episodes where southern foxtail pine expanded upslope. Although the data are somewhat unclear [55,89], 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 [62,64], 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 [68,82,88].Northern foxtail pine is threatened by global warming. Already restricted to a relatively few high-elevation peaks, there are no higher-elevation refugia for the Klamath Mountains subspecies to migrate to. Many northern foxtail pine populations are being "squeezed off the tops of mountains that are insufficiently high to provide suitable habitat" .
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