BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pinus balfouriana | Foxtail Pine 



GENERAL BOTANICAL CHARACTERISTICS : 
Even at upper treeline, the typical growth habit of mature foxtail pines
is erect and straight with a largely intact cambium, full crown, and
retained leader.  The sparse crowns of contorted trees are often only
supported by a narrow strip of cambium, the living tissue of a tree.
The effects of sand and ice-blasting by wind are seen in older trees
with double "pick-a-back" growth form.  The windward trunk is dead, but
a narrow strip of cambium supports branches on the leeward side of the
tree, the "piggy back" [12].

Trees of the northern foxtail pine, ssp. balfouriana grow erect or with
an uphill lean.  Individuals are commonly 30 to 60 feet (100-200 m)
high.  The tallest is recorded at 98 feet (32 m).  One large relict of
the southern foxtail pine, ssp. austrina, growing at 10,540 feet (3,200
m) on Alta Peak, Tulare County, California, is 6.7 feet (2 m) in d.b.h.
and 78.5 feet (24 m) in height [3].  Trees retain needles 10 to 15
years.  Although the southern Sierra Nevada foxtail pine usually grows
erect, it is more often twisted.  Trees retain needles 20 to 30 years
[12].

Foxtail pines have deep and spreading root systems which probably occupy
the openings between trees [2].  Since they grow as widely spaced
individuals, the density of associated plants is low, with an absence of
associated plant competition [13].

Foxtail pines and bristlecone pines (Pinus longaeva and P. aristata)
share numerous interesting characteristics [13]:

   (1)  occurrence at the upper limits of tree growth and a reduced 
        rate of growth
   (2)  a capacity for long life
   (3)  continued growth after loss of large areas of tissue 
        from drought, stress, wind injury, and soil erosion
   (4)  heavy, dense, resin-impregnated wood with small, 
        closely arranged water-conducting cells (tracheids) which
        provide resistance to moisture and decay
   (5)  survival in an environment of drought, low temperatures, 
        short growing season, daily temperature extremes, and poor 
        soils
   (6)  retention of needles for several years, which reduces their 
        need for moisture and nutrients, as well as helps to carry a
        tree over several years of stress
   (7)  relative safety from ground fire due to sparse ground cover 
        and litter scarcity

The longevity of foxtail pine is of interest because of the long life
spans reported for its close relatives the bristlecone pines.  In
general, trees of northern foxtail pine do not live as long as those of
southern foxtail pine.  The greatest known age of the northern foxtail
pine is 364 years.  In comparison, the greatest known age of a southern
foxtail pine is 682 years.  Northern foxtail pine, growing in the moist
Klammath Mountains, has a greater frequency of heartwood decay than
southern foxtail, which grows in the drier Sierra Nevada [13].

It is often difficult to determine the exact age and growth rates of
these trees because of asymmetric growth and heartwood decay.  Tree ages
can be estimated with increment bores.  Based on ring counts and growth
rates, the maximum attainable age for northern foxtail pine is estimated
to be 1,300 to 1,500 years, while that of southern foxtail pine is 2,500
to 3,000 years [12,13].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
The environmental and physiological factors contributing to the longevity of
foxtail pines also work to lower their regeneration potential.  Seedlings are
slow growing [3].  With the caching of foxtail pine seeds by seed-eaters,
seedlings often occur in dense clusters.  The effects of this caching in the
regeneration of foxtail pine appears beneficial, since there is a high
frequency of clumped trees [6].


SITE CHARACTERISTICS : 
Subspecies balfouriana occurs as several scattered stands in the Marble,
Scott, and Yolla Bolly mountains, as well as the Trinity Alps from 6,700
to 9,000 feet (2,000-2,400 m).  Occasional individuals grow in mountain
valleys as low as 6,400 feet (1,950 m).  This Klammath Mountain
subspecies is found on ridges, as well as upper southern and western
slopes where trees form open stands at elevations over 7,200 feet (2,200
m).  Northern foxtail pine occurs on several parent material types but
is especially common on ultrabasic serpentine, schist, and granodiorite
[2,5,12,13].

Subspecies austrina ranges from 8,500 to 12,000 feet (2,600-3,650 m) in
elevation on the upper South Fork of the Kern River drainage and is
characteristic of treeline.  Occasional individuals are found as low as
7,700 feet (2,350 m).  Trees grow in open stands on dry sunny ridges.
The most commobn parent material is decomposed granite, which gives rise
to shallow, coarse-textured soils, usually with boulders [2,5,12,13].

At its lower elevational limits, foxtail pine grows in pure stands or
mixed with whitebark pine, lodgepole pine, Jeffrey pine, and western
white pine (Pinus monticola).  At higher elevations trees usually grow
as widely spaced individuals in pure stands.  Plants are intolerant of
shade at all stages of growth.  Ground cover under these trees is
characterized by bare earth and rock with a few scattered herbs [3].

The growing conditions of ssp. balifouriana in the Klammath Mountains
are less extreme than those of subsp. austrina in the southern Sierra
Nevada.  With average annual precipitation in the Klammath Mountains
ranging from 50 to 60 inches (125-175 cm), subspecies balfouriana is
found in the wettest habitat of any of the bristlecone or foxtail pines.
In contrast, annual precipitation in the southern Sierra Nevada averages
20 to 30 inches (50-75 cm).  Temperature extremes are great and winds
severe.  In both areas most of the precipitation occurs as winter snow.
Summers are dry with low relative humidity [12,13].


SUCCESSIONAL STATUS : 
Foxtail pine is a climax species and persists at treeline for hundreds
to thousands of years in the absence of disturbance and competition.  It
is highly adapted to its habitat of very shallow soils, slow primary
succession, short growing season, and avalanches [2,13].


SEASONAL DEVELOPMENT : 
Foxtail pines flower from July to August.  The period of flowering and
coneopening is uniform for foxtail pine, and the two bristlecone pines.
Ssp. balifouriana flowers somewhat later than than ssp. austrina [5,9].

Cones ripen from September to October with seed dispersal at this time.
The minimum seed-bearing age for trees is 20 years with 5 to 6 years
between large seed crops [9].

Related categories for Species: Pinus balfouriana | Foxtail Pine