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Wildlife, Animals, and Plants
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Introductory
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
ABBREVIATION :
PINPONP
SYNONYMS :
NO-ENTRY
SCS PLANT CODE :
PIPO
COMMON NAMES :
Pacific ponderosa pine
ponderosa pine
western yellowpine
bull pine
TAXONOMY :
The currently accepted scientific name of Pacific ponderosa pine is
Pinus ponderosa var. ponderosa Dougl. [28].
Three varieties of ponderosa pine are currently recognized and are
distinguished by morphological variations and geographical location
[7,48]:
var. arizonica (Engelm.) Shaw - Arizona pine. (classified as a
separate species, P. arizonica
Engelm.), by some authorities).
Occurs in the mountains of extreme
southwest New Mexico, southeast
Arizona, and northern Mexico. Has
shorter cones and narrower cone
scale prickles. Usually has
five-needle fascicles.
var. ponderosa - Pacific ponderosa pine. Extends from the
mountains of southern California northward along
the Sierra Nevada-Cascade Range to southern
British Columbia. Usually has three-needle
fascicles.
var. scopulorum (Engelm.) - Interior ponderosa pine. Extends from
west-central Montana, southward through
the mountains, plains, and basins of
Colorado, Arizona, and New Mexico. Has
a moderate to high proportion of
two-needle fascicles.
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
COMPILED BY AND DATE :
R. J. Habeck, March 1992
LAST REVISED BY AND DATE :
NO-ENTRY
AUTHORSHIP AND CITATION :
Habeck, R. J. 1992. Pinus ponderosa var. ponderosa. In: Remainder of Citation
DISTRIBUTION AND OCCURRENCE
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
GENERAL DISTRIBUTION :
Pacific ponderosa pine ranges from latitude 52 degrees N in the Fraser
River Drainage of southern British Columbia south through the mountains
of Washington, Oregon, and California to latitude 33 degrees N near San
Diego. In the northeastern part of its range it extends east of the
Continential Divide to longitude 110 degrees W in Montana and south to
the Snake River Plain in Idaho [48].
ECOSYSTEMS :
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES25 Larch
FRES26 Lodgepole pine
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub
FRES36 Mountain grasslands
STATES :
CA HI ID MT NV OR WA BC
ADMINISTRATIVE UNITS :
BIHO CRLA GLAC JODA KICA LAVO
LABE MORA NOCA SEQU WHIS YOSE
BLM PHYSIOGRAPHIC REGIONS :
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
7 Lower Basin and Range
8 Northern Rocky Mountains
KUCHLER PLANT ASSOCIATIONS :
K002 Cedar - hemlock - Douglas-fir forest
K005 Mixed conifer forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K034 Montane Chaparral
SAF COVER TYPES :
210 Interior Douglas-fir
211 White fir
212 Western white pine
213 Grand fir
215 Western white pine
217 Aspen
218 Lodgepole pine
228 Western redcedar
229 Pacific Douglas-fir
231 Port-Orford-cedar
233 Oregon white oak
234 Douglas-fir - tanoak - Pacific madrone
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine - Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
248 Knobcone pine
249 Canyon live oak
250 Blue oak - Digger pine
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Pacific ponderosa pine forms climax stands that border grasslands and is
also a common seral tree on many other forested sites [63]. Being
drought tolerant, it is usually occupies the transition zone between
grassland and forest. Climax stands are characteristically warm and
dry, and occupy lower elevations throughout their range. Key understory
associates in climax stands typically include grasses such as bluebunch
wheatgrass (Pseudoroegneria spicata) and Idaho fescue (Festuca
idahoensis), and shrubs such as bitterbrush (Purshia tridentata) and
common snowberry (Symphoricarpos albus). At higher elevations, Pacific
ponderosa pine is seral to trees that are more shade tolerant and
moisture demanding. In the Pacific Northwest this generally includes
Douglas-fir (Pseudotsuga menziesii), grand fir (Abies grandis), and
white fir (A. concolor) [8,18,49,63].
Publications listing Pacific ponderosa pine as an indicator or dominant
species in habitat types (hts), community types (cts), and plant
associations (pas) are as follows:
Area Classification Authority
---- -------------- -------------------------
CA forest (pas) Atzet & Wheeler 1984
CA forest (cts) Erhard 1979
CA forest (hts) Horton 1960
ID forest (pas) Schlatterer 1972
ID forest (cts) Tuhy & Jensen 1982
c ID forest (hts) Steele & others 1981
n ID forest (hts) Cooper & others 1991
MT forest (hts) Pfister & others 1977
OR forest (pas) Kovalchik 1987
OR forest (pas) Hopkins 1979b
OR forest (pas) Hopkins & Kovalchik 1983
OR forest (pas) Johnson & Simon 1987
c OR forest (pas) Volland 1985
e OR se WA forest (cts) Hall 1973
WA forest (pas) Williams & Lillybridge 1983
e WA n ID forest (hts) Daubenmire & Daubenmire 1968
VALUE AND USE
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
WOOD PRODUCTS VALUE :
Pacific ponderosa pine is a valuable lumber species in the Inland West,
with 1986 sales exceeding 1.4 billion dollars in wholesale value [4].
Old-growth Pacific ponderosa pine produces clear, high-grade lumber,
although young trees are typically limby because natural pruning
develops slowly. An average clear length of only 11.5 feet (3.5 m) was
recorded in 250 year-old stands in central Idaho [48]. Consumption of
Pacific ponderosa pine wood products is primarily limited to the United
States, with some export to Canada. A large percentage of small,
low-grade trees are processed into dimensional lumber and other products
for the construction market. High-grade lumber is an important raw
material for molding, mill work, cabinets, doors, and windows [4].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Food: Pacific ponderosa pine needles, cones, buds, pollen, twigs,
seeds, and associated fungi and insects provide food for many species of
birds and mammals [13]. Small mammals that eat stems and roots include
deer mice, chipmunks, shrews, voles, and tree and ground squirrels.
Large browse mammals include elk, deer, porcupines, hares, rabbits,
cattle, sheep, and occasionally horses, goats, and feral hogs
[6,13,29,41]. Many bird species eat Pacific ponderosa pine seeds.
These include the junco, Cassin's finch, pine siskin, evening grosbeak,
varied thrush, Clark's nutcracker, and a host of sparrows, chickadees,
and other passerines [13,21,49].
Shelter: At each morphological stage, Pacific ponderosa pine provides
numerous species of birds and mammals with shelter. As seedlings they
provide low ground cover for small birds and mammals. Upon reaching
pole size, stands provide good windbreaks and thickets important as
hiding cover for larger mammals such as elk and deer. Mature trees and
standing snags house arboreal species, while fallen logs and stumps
provide many cavity-dwelling species with adequate shelter [27,49].
PALATABILITY :
In Montana, Pacific ponderosa pine is considered low in palatability for
cattle, horses, and sheep [11]. Elk in northwestern Montana also find
it unpalatable. Elk, along with deer and bighorn sheep, occasionally
browse on stems and bark during times of food or water scarcity [19,74].
NUTRITIONAL VALUE :
Nutrient means for Pacific ponderosa pine structural components from Lubrecht
Experimental Forest, western Montana, are as follows [61]:
Green Needles Twigs Wood Sound Wood
(1 Year) (0.64-2.5 cm)* (2.5-7.6 cm) ( >7.6 cm)
------------------------------------------------------------------------
Ca 3,069.0** 2,029.0 1,013.0 659.0
Cu 5.4 6.3 7.0 4.8
Fe 118.0 59.6 23.3 28.5
K 4,952.0 1,627.0 741.0 395.0
Mg 1,036.0 627.0 336.0 250.0
Mn 205.0 75.0 65.0 62.2
N 10,455.0 2,857.0 1,012.0 692.0
Na 32.0 31.0 22.8 31.4
P 1,329.0 367.0 200.0 387.0
Zn 34.3 27.1 16.9 5.8
Percent
ash 3.4 0.99 0.78 0.33
* Measurement in diameter.
** All values are express in micrograms per gram.
COVER VALUE :
Pacific ponderosa pine is important in providing wildlife cover.
Species using this tree for cover include the bald eagle, wild turkey,
and band-tailed pigeon for roosts; and squirrels, hawks, and owls for
nest trees. Primary and secondary cavity-nesting birds such as the
acorn woodpecker and mountain chickadee use both live and dead pine
trees. Pacific ponderosa pine provides thermal and escape cover for
mule deer and elk. Fallen logs and stumps are used as cover by
cottontails, small rodents, and reptiles [27,49].
VALUE FOR REHABILITATION OF DISTURBED SITES :
Pacific ponderosa pine is widely used for soil stabilization and
watershed protection in the Rocky Mountain region [67]. Bareroot stock
is used occasionally for planting on mine-spoils in the West [72].
OTHER USES AND VALUES :
Pacific ponderosa pine stands offer year-round recreation and aesthetic
scenery [48]. Native Americans in the Pacific Northwest used the inner
cambial layer as food. They also converted the resin into medicinal salve
for rheumatism, backaches, and dandruff [24,41].
MANAGEMENT CONSIDERATIONS :
Insects: Approximately 200 insect species may affect Pacific ponderosa
pine from its cone stage to maturity [58]. The effects of insect damage
are: decreased seed and seedling production, reforestation failures or
delays, and reduction of potential timber productivity [13,58]. Several
insect species destroy seeds before they germinate, the most damaging
being the ponderosa pine cone beetle (Conophthorus ponderosae) and the
pine seed chalcid (Megastigmus albifrons). Seedlings and saplings are
deformed by tip moths (Rhyacionia bushnelli), shoot borers (Eucosma
sonomana), and budworms (Choristoneura lambertiana). Two major
lepidopteran pests, the pine butterfly (Neophasia menapia) and pandora
moth (Coloradia pandora), severely defoliate their hosts causing growth
reductions. Extensive mortality in defoliated stands usually results
from simultaneous infestations by bark beetles. Bark beetles, primarily
of the genus Dendroctonus and Ips, kill thousands of pines annually and
are the major mortality factor in commercial sawtimber stands. These
insects can be managed through the use of insecticides, pheromones, or
by stand improvement techniques [58].
Disease: Pacific ponderosa pine is affected by many diseases.
Parasites, root diseases, rusts, trunk decays, and needle and twig
blights cause significant damage. Dwarf mistletoe (Arceuthobium
campylopodum) causes the most damage. A major root disease of pine is
caused by white stringy root rot (Fomes annosus) and is often found in
concert with bark beetle infestations. Western gall rust
(Endocronartium harknessii), limb rust (Peridermium filamentosum), and
comandra blister rust (Cronartium comandrae) cause damage only in
localized areas. Various silvicultural treatments can minimize damage
caused by dwarf mistletoe. Clear-cutting is used only if regeneration
is not a problem. The pruning of branches and witches brooms,
fertilization, watering, and the planting of nonsusceptible species also
aid in combating dwarf mistletoe. Spraying with the growth regulator
Ethephon also temporarily limits mistletoe spread [25].
Chemical control: Limiting the invasion of Pacific ponderosa pine onto
valuable grazing land or for stand management has been achieved through
the use of chemical control [15]. Tordon 101 and 22K applied in July is
effective [34], although Cacodylic acid has been shown to consistently
kill this tree [47].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
GENERAL BOTANICAL CHARACTERISTICS :
Pacific ponderosa pine has the potential for achieving large dimensions.
Stems of 103.5 inches (263 cm) in d.b.h. and 232 feet (70.7 m) in height
have been recorded. Diameters at breast height of 30 to 50 inches
(76-127 cm) and heights of 90 to 130 feet (27.4-39.6 m) are common
throughout its range [5]. Trees often reach ages of 300 to 600 years
[48]. Needles are typically in bundles of three. They are 5 to 10
inches (12.5-25.0 cm) long and form tufts at the end of each branch.
Cones are oval and 3 to 6 inches (7.5-15.0 cm) long. The bole is
typically straight and at maturity is clear of lower branches. The bark
of mature trees is composed of broad, irregular scaly-plates that fit
together like jigsaw puzzle pieces. The crown is conical and composed
of stout branches [38,48].
RAUNKIAER LIFE FORM :
Phanerophyte
REGENERATION PROCESSES :
Pacific ponderosa pine reproduces sexually. It does not regenerate
naturally by vegetative methods. It can be propagated by rooting and
grafting, but success decreases rapidly when scions are taken from trees
older than 5 years [48].
Seedling development: Successful natural regeneration of Pacific
ponderosa pine is accomplished by a combination of heavy seed crops,
favorable weather during the growing season, soil texture, low
competition, and exposed mineral seedbeds [26,39]. Moisture-stress
reduces seed germination as well as initial seedling survival and
development. Pacific ponderosa pine has the capacity for root growth in
relatively dry soil. Nursery stock removed in January from California
had appreciable root elongation even when planted in soil with very low
water potential. Shrub competition reduces the height and diameter
growth of seedlings planted in northern California and Oregon. On the
western slopes of the Sierra Nevada, growth starts noticeably later with
each 2,000 foot (610 m) increase in elevation. Rates of height and
radial growth do not vary with elevation during the growing season [48].
Seed production and dissemination: Seed production varies with
geographic distribution. There are generally 6,900 to 23,000 clean
ponderosa pine seed per pound (6,210-20,700 per kg) [36]. In California
west of the Sierra Nevada, medium seed crops are borne on an average of
every 2 to 3 years. The average interval between heavy cone crops is 8
years; in the Pacific Northwest it is every 4 to 5 years. Twenty-three
years of data show Pacific ponderosa pine to be a poor seeder in western
Montana. It bears cones as early as 7 years and continues to produce
good cone crops up to at least 350 years. Optimum seed viability is
produced by trees 60 to 160 years old. In California, trees greater
than 25 inches (64 cm) d.b.h. were the most dependable seed producers.
Recommended cold stratification period is 30 to 60 days for stored seeds
at 33 to 41 degrees F (1-5 deg C). Pacific ponderosa pine seeds do not
naturally disseminate beyond about 100 feet (31 m) from the seed source.
In central Oregon, the amount of seeds reaching the ground at 132 feet
(40 m) into a clear-cut was only 22 percent that of those measured at
the timber's edge. At 528 feet (161 m) it was only 8 percent. Nearly
all seeds are disseminated by early November. In a good seed year, as
many as 345,080 seeds per acre (852,050 seeds per hectare) may reach the
ground [48,79].
Seedling mortality and predation: Many variables are responsible for
seedling mortality. Seedlings younger than 36 days old are more
susceptible to minimum night temperatures cooler than 23 degrees F (-5
deg C) than are lodepole pine (Pinus contorta) seedlings. During
winters with little snowcover, 1- and 2-year-old seedlings may suffer
damage and frost kill. Also, 1- to 3-month-old seedlings are killed by
stem temperatures of 130 degrees F (54 deg C) and higher. Pacific
ponderosa pine seeds are consumed by a number of birds and small
mammals. Squirrels and porcupines clip many of the cone-bearing twigs,
hence destroying flowers and conelets. Rabbits and hares injure or kill
many seedlings by nibbling young stems, while pocket gophers may
decimate an entire population of seedlings. Repeated browsing by deer
may stunt seedling growth for up to 50 years [13]. Livestock also
damage seedlings and saplings by trampling, bedding, and browsing. Many
species of insects and disease affect Pacific ponderosa pine. See
MANAGEMENT CONSIDERATIONS for futher discussion [48].
SITE CHARACTERISTICS :
Throughout its range, Pacific ponderosa pine is dependent upon several
site variables such as soils, elevation, and climate [68]. Soil
moisture is the variable most often limiting growth, especially in the
summer months when rainfall is deficient [48].
Climate: Pacific ponderosa pine is typically found on warm, dry sites.
The climate is characterized by a short growing season and minimal
summer precipitation. The mean annual precipitation ranges from 11 to
17 inches (28-43 cm), with summer precipitation averaging 5 to 10 inches
(13-25 cm). Average annual precipitation ranges from about 14 to 30
inches (35-75 cm) on Pacific ponderosa pine sites in Oregon and
Washington, and is typically in the form of snow [18]. The western
slope of California's northern Sierra Nevada may be the wettest area
supporting Pacific ponderosa pine, with an annual rainfall reaching 69
inches (173 cm). In contrast, this species occupies areas in California
where extreme rainfall deficiencies occur [July and August precipitation
about 1 inch (2.5 cm) or less] [48].
Soil and topography: Pacific ponderosa pine occurs on a wide variety of
soils ranging from glacial till, glacio-fluvial sand and gravel, dune,
basaltic rubble, colluvium, to deep loess or volcanic ash. This pine
develops best on wet, deep, sandy gravel and clay loams with pH between
6.0 and 7.0. Throughout its extensive range, however, it will most
often be found on a variety of loams, loamy sand, and gravel; with a pH
from 4.9 to 9.1 [68,74]. Many studies have shown better survival and
growth rates on coarse-textured clayey soils where extensive root
proliferation is possible [18]. In Oregon, Pacific ponderosa pine soils
are typically less than 40 inches (100 cm) deep and formed from loess
and basalt colluvium and bedrock materials. Surface layers have silt
loam to silty clay loam textures with greater than 35 percent rock
fragments by volume. Surface rocks usually exceed 10 percent cover
[33]. Pacific ponderosa pine has been found on a variety of sites from
steep slopes in the plateau region of northern Idaho and Oregon to the
flat coastal plains of California [7,48].
Elevation: Elevational ranges of Pacific ponderosa pine are as follows
[68]:
State Mean ft (m) Range ft (m)
----- ------------- -----------------------------
California 3,242 (988) 348 to 6,520 (106-1,987 m)
Oregon (eastern) 5,400 (1,646) 1,800 to 9,000 (549-2,743 m)
Oregon (western) 2,800 (853) 2,200 to 3,400 (670-1,036 m)
Washington 2,625 (800) 330 to 4,950 (100-1,510 m)
Associated forest cover: Pacific ponderosa pine is associated with a
rich variety of tree species. Only five of these, however, western
juniper (Juniperus occidentalis), Rocky Mountain juniper (J. scoparium),
quaking aspen (Populus tremuloides), lodgepole pine, and Oregon white
oak (Quercus garryana), are common associates in climax stands [18].
Understory associates can be catagorized into two groups: a shrub- and
forb-rich group and a drier bunchgrass-dominated group. The climax
shrub-dominated undergrowth generally includes ninebark (Physocarpus
malvaceus), common snowberry, and bitterbrush. Seral site shrubs
generally include blue huckleberry (Vaccinium globulare) and bearberry
(Arctostaphylos uva-ursi) [9,49,63].
SUCCESSIONAL STATUS :
Historically, fire has played the greatest role in the successional
status of Pacific ponderosa pine. See FIRE ECOLOGY for further
discussion.
In many areas of the Pacific Northwest, the first zone above the
grasslands is the Pacific ponderosa pine climax. This tree species is
shade intolerant and grows most rapidly in near full sunlight [18,74].
There is a strong tendancy for climax pine stands to be even-aged in
small groups rather than being truly uneven-aged. Heavy grazing induces
effects opposite those of fire. Removal of the grass cover by grazing
tends to favor shrub communities. Logging is usually done by a
selection-cut method. Older trees are taken first, leaving younger,
more vigorous trees as growing stock. This method substantially
accelerates the successional trend toward a more climax dominant tree
species. Logging also impacts understory species by machine trampling
or burial by slash. Clear-cutting generally results in dominance by
understory species present before logging, with invading species playing
only a minor role in postlogging succession [18,39].
The successional status of Pacific ponderosa pine can be expressed in
terms of its successional role, which ranges from seral to climax
depending on specific site conditions. It plays a climax role on sites
toward the extreme limits of its environmental range and becomes
increasingly seral with more favorable conditions. On sites with more
favorable moisture, pine encounters greater competition and must
establish itself opportunistically. On moist sites it is usually seral
to Douglas-fir and the true firs (mainly grand fir and white fir). On
severe sites it is climax by default because other species cannot
establish. On such sites, establishment is likely to be highly
dependent upon the cyclical nature of large seed crops and favorable
weather conditions [62].
SEASONAL DEVELOPMENT :
In California, Pacific ponderosa pine flowers from April to June; cone
ripening and seed dispersal occur from August to September [48].
FIRE ECOLOGY
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
FIRE ECOLOGY OR ADAPTATIONS :
Fire is an integral part of the ecology of Pacific ponderosa pine.
Studies have shown that prior to 1900, most stands experienced
low-severity surface fires at intervals ranging from 1 to 30 years.
Fire scars and pollen analysis trace this phenomena back to at least
A.D. 1500. Fire has allowed Pacific ponderosa pine to dominate sites
where it is the potential climax as well as sites where it is seral to
more shade-tolerant tree species [2,22,26,39].
Pacific ponderosa pine has evolved with a thick bark and open crown
structure that allows it to survive most fires. Mature trees will
self-prune, leaving a smooth bole which reduces aerial fire spread.
Other fire adaptations include deep roots, high foliar moisture content,
insulated bud scales, and medium to light lichen growth [16,17,54].
Seedlings prefer the mineral-soil seedbeds created by fire [42].
Fire also shapes the composition of Pacific ponderosa pine stands. In
the late 1800's stands exhibited open parklike appearances with
well-stocked overstories and relatively few understory trees. Fire
suppression, however, has allowed the unnatural buildup of forest fuels
which has increased the occurrence of stand-replacing fires. Over the
last 100 years of fire suppression, seral Pacific ponderosa pine stands
have been replaced by shade-tolerant climax stands [2,22,26].
POSTFIRE REGENERATION STRATEGY :
Crown-stored residual colonizer; short-viability seed in on-site cones
Off-site colonizer; seed carried by wind; postfire years 1 and 2
Off-site colonizer; seed carried by animals or water; postfire yr 1&2
FIRE EFFECTS
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
IMMEDIATE FIRE EFFECT ON PLANT :
Fire has a wide variety of potential effects on Pacific ponderosa pine.
These effects vary according to size, configuration, and density of the
stand, in addition to fire severity. Generally, well-spaced seedlings
and saplings are able to withstand low-severity fires, as are pole-sized
and mature trees. Moderate- to high-severity fires, however, will kill
trees pole-sized and smaller. Mature Pacific ponderosa pines have a
higher survival rate than younger trees due to their enhanced
adaptations to fire [16,39,77].
The principal cause of mortality following fire is crown scorch rather
than damage to the cambium or roots. The size of tree determines its
ability to withstand scorch. A model has been developed to predict
mortality using tree d.b.h. and scorch heights as independent variables.
Fire effects are also dependent upon other factors such as season, site
condition, tree age and vigor, available moisture, and occurrences of
insect and disease attack [39,56].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
If fire consumes any part of tree canopy, the total leaf area is
reduced, thus decreasing photosynthesis. If burning results in damage
to the bole or roots, nutrient and water transport is impaired. Heat
from fire may kill living tissue and result in a certain amount of
stress [26,39,55].
Crown damage: Crown scorch appears to be the leading factor in the
majority of damage to Pacific ponderosa pine. Estimation of percent
crown volume scorch has been proven to be the best predictor of tree
mortality following fire. Crown damage is most severe in spring and
early summer due to low foliar moisture content and the succulent nature
of the buds and twigs [39,55]. Survival of buds is also crucial to
postburn survival of Pacific ponderosa pine. Buds can tolerate
temperatures 68 degrees F (20 deg C) higher than the needles can due to
their protective outer scales. Therefore, large trees can sometimes
survive a 100 percent crown scorch provided not all the buds are heat
killed [26,39,44,55].
Root damage: Following prescribed burning of old-growth Pacific
ponderosa stands in Crater Lake National Park, Oregon, mortality was
higher in burned areas (19.5 percent) than in unburned areas (6.6
percent). A major factor contributing to postfire mortality was the
reduction of fine roots. Burning reduced fine-root dry weight 50 to 75
percent from 1 to 5 months after burning [64].
Bole damage: This pine is fire tolerant because it has a fire-resistant
bark containing a 1/8- to 1/4-inch (0.3-0.6 cm) thick layer at 2 inches
(5 cm) diameter [77]. It also has a very moist core of high density
wood that dissipates the heat energy it receives, thus protecting the
bole from lethal heat levels [55]. Ryan and Frandsen [53], however,
found that mature Pacific ponderosa pine trees suffered more basal
injuries from smoldering fires than did immature trees because of the
greater quantities of accumulated duff surrounding their boles. Cambium
damage most often occurs after the passing of high-severity fires.
Young trees are most susceptible to cambium damage as a result of
thinner bark and a higher occurrence of girdling [26,78]. Partially
girdled trees may survive up to 25 percent basal loss if root and crown
damage is minimal [71].
Season of burn: Pacific ponderosa pine can withstand low-severity fires
which generally occur during the wet months of early spring or late
fall. A dry spring fire may occur when trees are in stress during leaf
and bud burst, resulting in higher mortality rates. Trees become
dormant toward fall and thus are more fire resistant. In fall, Pacific
ponderosa pine can withstand up to 50 percent crown scorch, while in
spring only 30 percent [26,45].
PLANT RESPONSE TO FIRE :
Pacific ponderosa pine's response to fire will vary according to fire
severity, tree age, and season. High-severity fires that occur during
periods of high stress will generally result in death. Low- to
medium-severity fires will generally restrict the growth and
regeneration of the tree, but recovery is usually evident the following
year [39]. Immediately following fire, Pacific ponderosa pine may
experience a large needle drop as a reaction to hot convectional air
movement through the canopy [55].
Postfire seedling establishment: Fire creates favorable seedbeds for
seedling establishment. The soil is often rich in available inorganic
nitrogen that benefits tree growth [52]. Postfire stocking rates depend
upon site characterisitcs, fire severity, and weather. The potential
for regeneration after fire is generally considered good [39]. On the
Eldorado Natinal Forest, California,a low-severity burn resulted in
20,000 seedlings per acre (49,400/ha) on burned sites and no seedling
establishment on unburned sites [39]. In a western Montana study,
Pacific ponderosa pine produced 12 percent of the total number of sound
seeds found on a burned clear-cut site over a 5-year period [64]. A
postburn study in the Plumas National Forest, California, found that
Pacific ponderosa pine had the highest postburn percent increase of all
other associated species [39]. Postfire stocking rates depend upon site
characterisitcs, fire severity, and weather. The potential for
regeneration after fire is generally considered good [39]. In a western
Montana study, Pacific ponderosa pine produced 12 percent of the total
number of sound seeds found on a burned clear-cut site over a 5-year
period [64]. A postburn study in the Plumas National Forest,
California, found that Pacific ponderosa pine had the highest postburn
percent increase of all other associated species [39].
Postfire growth and recovery: Information concerning Pacific ponderosa
pine's response after fire is variable. This may be attributable to the
beneficial effects of reduced competition and increased nutrient
availability, along with the detrimental effects of damage to the crown,
cambium, and roots. Some studies found reductions in diameter and height
growth [46,76], while others reported increases in postfire growth
[8,46,69,73].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
NO-ENTRY
FIRE MANAGEMENT CONSIDERATIONS :
The last 100 years has produced unplanned, radical changes in stand
structure, fuel loadings, and role of fire in Pacific ponderosa pine
ecosystems [2]. Postsettlement fire suppression has resulted in dense
stockings of shade-tolerant species and the increase of insects and
disease. These results have led to other concerns such as loss of
timber productivity, loss of natural diversity and aesthetic values, and
the increased risk of severe fire damage to homes and harvestable timber
[26].
Prescribed fire: Reduction of fuel loads beneath existing stands of
Pacific ponderosa pine by the use of prescribed fire has proven useful
in reducing the potential threat of wildfires, while also favoring
natural regeneration of seral species through site preparation. In
western Montana, prescribed burning on an interval of 20 to 25 years is
suggested to maintain seral species and open stocking. This would also
prune lower branches thus increasing timber values, while also lowering
the risk of wildfire [2,22,26,39].
Nutrient depletion: Prescribed fire often leads to the loss of volatile
nutrients from the site, especially nitrogen (N). Following a
prescribed fire on a Pacific ponderosa pine site in Oregon, all periodic
annual growth increments were reduced in surviving trees four growing
seasons later. Foliar N concentration was not affected by the fire;
however, total foliar N content was reduced immediately after burning.
Foliar N content was significantly correlated with the observed
reductions in periodic annual increments [39,40].
FIRE CASE STUDIES
SPECIES: Pinus ponderosa var. ponderosa | Pacific Ponderosa Pine
CASE NAME :
Impact of prescribed burning on a sequoia-mixed conifer forest
REFERENCE :
Kilgore, B. M. 1072 [80]
SEASON/SEVERITY CLASSIFICATION :
Fall burn / Low- to Moderate-severity
STUDY LOCATION :
The study site was located on the ridge of Redwood Mountain which runs
north and south within the 3,100-acre Redwood Mountain Grove of giant
sequoia (Sequoiadendron giganteum) in Kings Canyon National Park, Three
Rivers, California.
PREFIRE VEGETATIVE COMMUNITY :
Giant sequoia, white fir (Abies concolor), and sugar pine (Pinus
lambertiana) dominate the forest, with incense-cedar (Libocedrus
decurrens), Pacific ponderosa pine, and California black oak (Quercus
kelloggii) represented except in the extreme southern plots. Shrubs and
herbs are present but rare, and grasses are almost absent. Major shrub
species include Sierra mountain misery (Chamaebatia foliolosa) and
Sierra gooseberry (Ribes roezlii). Graminoids include sedges (Carex
spp.).
TARGET SPECIES PHENOLOGICAL STATE :
The target phenological states were not recorded.
SITE DESCRIPTION :
The elevation along the ridge ranges from 6,400 feet (1,950 m) at the
saddle to nearly 7,000 feet (2,134 m). Hygrothermograph records show a
yearly low of 17 degrees F (-8.4 deg C) and a high of 82 degrees F (28
deg C). Temperatures in November just before the burn ranged from 32 to
58 degrees F (0-15 deg C). Relative humidity fluctuated between 30 and
80 percent. Winds in and near the study plots were moderate when
present, varying from 0 to 5 mph (0.3 kmh). Average slope was 35
percent. Large portions of this study area are found on soils derived
from metamorphic schists.
Burn day conditions were as follows:
Temperature: 59 degrees F (15 deg C)
Humidity: 20 percent
10-hour fuel sticks: 10 grams
Wind speed: 0 mph
FIRE DESCRIPTION :
Twelve 60- by 100-foot (18x30 m) study plots were laid out about 600
feet (183 m) east of the ridge of Redwood Mountain at an elevation of
6,300 feet (1,920 m). Two additional plots were established just below
the saddle parking area as demonstration plots. These were selected as
being represenative of the range of vegetative and fuel conditions found
on this east-facing slope of the mountain. Seven of the 12 plots and
one demonstration plot were burned, while the remaining plots were
retained as controls. For each plot, the following information was
measured before and after ignition:
1. Species, diameter, height class > 6 inches d.b.h. (15 cm) or 4.5 feet
(1.4 m) tall.
2. Number of white fir and sugar pine saplings per acre in four height
classes.
3. Extent and approximate height of white fir sapling thickets.
4. Coverage and frequency values.
5. Litter and duff weights.
6. Length and diameter of down trees.
7. Chemical light meter indices for light reaching the forest floor.
8. Vegetation appearance recorded by black and white/color photographs
from 102 permanent photo points.
After all preburn measurements were made, a 2-foot (0.6 m) wide
fire-line was built along the two sides and the bottom of the proposed
5-acre (2 ha) burn area. The burning indices for the burn day were as
follows:
Forecast Actual Prescription (range)
-------- ------ --------------------
Fine Fuel Moisture 6 5 7-10
Spread Index 8 8 5-12
Intensity Index 59 56 37-49
Timber Burning Index 5 5 3-5
Ignition Index 45 55 15-49
All test plots were ignited at 0900 by drip torch along the upper
boundary of the burn area. A strip-head fire method of ignition was
used and it burned briskly from 0900 to 1200.
FIRE EFFECTS ON TARGET SPECIES :
Ninty-four percent of the 210 2- by 3-foot (0.6x0.9 m) sample plots
showed evidence of fire impact. Eighty percent burned almost
completely, while 14 percent burned partially or lightly. Only 6
percent of the sample plots remained unburned. Pacific ponderosa pine
trees greater than 12 inches (0.3 m) d.b.h. showed an increase in
relative density from 7.9 percent to 8.2 percent. This increase may be
attributable to the reduction in white fir density. Overall, Pacific
ponderosa pine cover percent increased 0.9 percent for all size classes.
This suggests that it is relatively resistant to low- to
moderate-severity fires under these burn conditions.
Preburn measurement of litter and duff was 50 tons/acre (124 tons/ha).
Following burning, litter fuels were reduced by more than 75 percent and
duff fuels by more than 85 percent, resulting in a postburn measurement
of 7.7 tons/acre (19 tons/ha).
FIRE MANAGEMENT IMPLICATIONS :
This study investigated methods by which the impacts of prescribed fire
on certain biotic and abiotic elements of the sequoia-mixed conifer
forest ecosystem could be measured. Pacific ponderosa pine was present
as a codominant species with an estimated 3.1 trees per acre (7.6/ha).
Different fire severities were found to produced different results. In
an earlier study, a high-severity fire created more canopy openings,
prepared better seedbeds, dispersed smoke more effectively, and consumed
surface fuels more completely than this low- to moderate-severity fire.
Options for fire management in this type of stand include a
high-severity fire followed by another moderate-severity fire 7 to 10
years later; or, alternatively implement two low-severity fires in
closer sequence in order to gradually kill young seedlings and cleanup
heavy fuels. Both strategies would allow for more natural regeneration
of seral species, while reducing the potential threat of hazardous
wildfires.
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Index
Related categories for Species: Pinus ponderosa var. ponderosa
| Pacific Ponderosa Pine
|
 |
