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Wildlife, Animals, and Plants
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Introductory
SPECIES: Larix occidentalis | Western Larch
ABBREVIATION :
LAROCC
SYNONYMS :
Pinus nuttallii Parl.
SCS PLANT CODE :
LAOC
COMMON NAMES :
western larch
Montana larch
mountain larch
hackmatack
tamarack
western tamarack
TAXONOMY :
The currently accepted scientific name of western larch is Larix
occidentalis Nutt. [59]. All ten species of larch (Larix spp.) are
found in cool areas of the Northern Hemisphere [40]. Where the ranges
of western larch and alpine larch (L. lyallii) overlap, alpine larch
grows at higher elevations. Wherever these two larch species are
sympatric, natural hybrids occur [58,72,118]. Western larch has been
successfully crossed with Japanese larch (L. leptolepus) [118]. Western
larch has much genetic flexibility or variability within populations and
relatively little variation or differentiation between populations
[98,99].
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
COMPILED BY AND DATE :
M. F. Crane, January 1991
LAST REVISED BY AND DATE :
NO-ENTRY
AUTHORSHIP AND CITATION :
Crane, M. F. 1990. Larix occidentalis. In: Remainder of Citation
DISTRIBUTION AND OCCURRENCE
SPECIES: Larix occidentalis | Western Larch
GENERAL DISTRIBUTION :
Western larch grows in the Upper Columbia River Basin from southeastern
British Columbia to northwestern Montana, northern and west-central
Idaho, and northeastern Washington. Its range includes the Blue and
Wallowa mountains of southeastern Washington and northeastern Oregon and
the east slopes of the Cascade Mountains in Washington and northern
Oregon [58,116].
ECOSYSTEMS :
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce
FRES25 Larch
FRES26 Lodgepole pine
STATES :
ID MT OR WA BC
ADMINISTRATIVE UNITS :
CODA GLAC NOCA
BLM PHYSIOGRAPHIC REGIONS :
2 Cascade Mountains
8 Northern Rocky Mountains
KUCHLER PLANT ASSOCIATIONS :
K001 Spruce - cedar - hemlock forest
K008 Lodgepole pine - subalpine forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K015 Western spruce - fir forest
SAF COVER TYPES :
205 Mountain hemlock
206 Engelmann spruce - subalpine fir
210 Interior Douglas-fir
212 Western Larch
213 Grand fir
215 Western white pine
218 Lodgepole pine
220 Rocky Mountain juniper
224 Western hemlock
227 Western redcedar - western hemlock
228 Western redcedar
237 Interior ponderosa pine
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Since western larch is primarily a seral species on sites where western
hemlock (Tsuga heterophylla), mountain hemlock (T. mertensiana), Pacific
silver fir (Abies amabilis), subalpine fir (A. lasiocarpa), grand fir
(A. grandis), western redcedar (Thuja plicata), Douglas-fir (Pseudotsuga
menziesii), or Engelmann spruce (Picea engelmannii) are potential climax
dominants, it is not used as an indicator of climax vegetation in
habitat type classifications. It is a seral species in 13 habitat types
in eastern Washington and northern Idaho and a major seral species in 12
habitat types in Montana [117]. In the Pacific Northwest, western larch
serves as an indicator of previous severe fires on fairly good to good
sites [45]. Habitat type indicators can be used to make a general
determination of western larch productivity [104]. Published
classification schemes listing western larch as an indicator or dominant
in community types (cts) or dominance types (dts) are presented below:
Area Classification Authority
MT riparian dts Hansen and others 1988
WA, OR; Blue Mountains general veg. cts Hall 1973
VALUE AND USE
SPECIES: Larix occidentalis | Western Larch
WOOD PRODUCTS VALUE :
Western larch is primarily used for construction lumber because of its
strength and hardness. It makes excellent utility poles because of its
length, form, and strength. It is also used in plywood manufacture and
to make fine veneer [118]. In lower montane forests of Montana, western
larch is the preferred timber species because it grows larger and yields
more clear timber than Douglas-fir [96]. Wood anatomy has been examined
in detail [83,148]. Two other wood products obtained from western larch
are arabinogalactan, a water-soluble gum used industrially, and
oleoresin, used to produce turpentine and related products [118]. The
wood is excellent fuel. Wood from western larch snags can be made into
shakes [4].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Deer, elk, moose, black bear, grizzly bear, and many species of birds
and small mammals occur in seral western larch forests. Western larch
stands frequently occur in areas of heavy snowpack that are unsuitable
for critical winter range for big game animals [116,118]. When western
larch stands are thinned, they have good potential for livestock forage
production [150].
Western larch needles are a major food source for the blue grouse and
spruce grouse [4]. The red crossbill eats some western larch seed [75].
Seed-eating small rodents prefer larger Douglas-fir and pine seed but
consume some western larch seed [9,132]. Squirrels cut and cache
western larch cones in years when other conifers have poor crops
[116,118]. Western larch is browsed sparingly by elk, deer, and moose
during winter when other food is scarce [35,116,118]. Bears or
porcupines may eat the inner bark of western larch saplings and poles in
the spring [116,118].
PALATABILITY :
Western larch appears to be unpalatable to most big game animals, but it
is eaten as emergency food [116,118]. Its seeds are palatable to small
birds and mammals, although larger seeds are preferred [9,132,116].
NUTRITIONAL VALUE :
Western larch needles at two locations in eastern Washington contained
2.0 percent and 1.7 percent nitrogen, respectively [40]. Nutrient
values for western larch needles, twigs, and other tree parts have been
reported from two sites in western Montana [137]. Whole tree values
have also been published [136]. Green needles from Lubrecht
Experimental Forest, Montana had a mean ash content of 5.8 percent and a
range of 3.47 to 8.16 percent, while green needles from Coram
Experimental Forest, Montana had a mean ash content of 5.3 percent and a
range of 4.9 to 8.9 percent. Nutrient values for needles are summarized
below [137]:
Lubrecht Forest Coram Forest
- - - - - - - - micrograms per gram - - - - - - - -
Mean Range Mean Range
Calcium 3,031 2,000-4,800 2,213 1,980-2,390
Copper 8.3 5.0-15.2 15.5 10.7-35.2
Iron 86.8 41-173 126 109-218
Potassium 6,405 2,800-9,760 4,958 4,390-5,388
Magnesium 1,098 692-1,592 1,083 1,005-1,113
Manganese 216 81-405 181 160-239
Nitrogen 13,518 9,730-15,540 23,320 17,920-28,923
Sodium 61.4 24.4-123.0 56 45-125
Phosphorus 2,343 1,678-3,186 2,960 1,894-3,269
Zinc 15.8 6.0-35.6 24.6 21.1-27.7
COVER VALUE :
Western larch snags provide nesting areas for cavity-nesting songbirds,
woodpeckers, and owls [4,116,118]. Around 25 percent of the birds that
nest in the northern Rocky Mountains make or use tree cavities. Western
larch, with its decay-resistant sapwood, is a preferred species [77,78].
The holes are also used for protection during storms and as roosting
sites [78]. Both snags and live western larch are used by cavity
nesters [77]. Flying squirrels may nest in holes in western larch
snags. The osprey, bald eagle, and occasionally the Canada goose build
platformlike nests on top of western larch snags [4].
VALUE FOR REHABILITATION OF DISTURBED SITES :
Western larch's rapid early growth, fire resistance, and the litter
layer produced by its deciduous needles make it useful for
rehabilitation on well-drained moist sites within its range [145].
However, it does not compete well with grasses and shrubs [112]. Seed
collection, stratification treatments, germination tests, and seed
handling have been described in detail [71,106,125]. Spot seeding has
been discussed [118,132]. Direct seeding rates for British Columbia are
given [84]. Detailed information is available on the production and
handling of seedlings [15]. Container-grown seedlings have been
inoculated and successfully formed mycorrhizal root systems with two
fungi, Laccaria laccata and Cenococcum geophilum [86].
OTHER USES AND VALUES :
Northern Rocky Mountain Native Americans enjoyed a sweet syrup made by
allowing western larch sap to evaporate and concentrate. They also ate
the cambium layer under the bark in spring and chewed solidified pitch
for gum [51]. Tea made from the bark was used for colds, coughs, and
tuberculosis. Western larch sap was used for sore throat and gum was
applied to cuts and bruises [51]. In British Columbia decoctions made
from western larch boughs or bark were used as a general tonic, for
respiratory ailments, as a poultice or wash for wounds, as a
contraceptive, to wash babies, and was both drunk and used as a wash for
breast cancer [143]. Boughs were dried for winter use, and western
larch pitch was used on the chest for respiratory ailments and on wounds
[143]. Western larch wood was used to make bowls, as a fuel, and the
rotten wood was used to smoke buckskin. Kootenai Indians used larch for
the center pole during the religious Sundance [51].
Western larch is easily grown in gardens and parks, although it may
become too large for home gardens. Seedlings are easy to transplant in
the fall after an early rain and may be treated as bonsai [68].
MANAGEMENT CONSIDERATIONS :
Management systems: The ecological requirements of western larch are
best met by even-aged silviculture systems. It is particularly well
adapted to seed tree cuts and clearcuts [113,116,146]. Clearcutting is
most effective where the overstory trees are infected with dwarf
mistletoe and root rots and may be most practical if western larch
regeneration is desired in a stand with few old larch left [113]. In
British Columbia, western larch is favored by short-rotations because of
its rapid growth on favorable sites [65]. It is a poor option for
high-elevation sites where its reliability is low, productivity is
variable, and it is subject to severe stem sweep [111].
Vegetative and reproductive buds can be distinguished by early fall,
allowing prediction of the following year's cone crop. Descriptions of
the different types of buds and sampling procedures have been published
[25,93,103]. In British Columbia, cone collection is best in
mid-September [25]. In western Montana, the best time for cone
collection is late August to early September. The collection period may
be extended by storing the cones and extracting seeds in October [125].
Cone production may be increased by girdling the tree. Seeds produced
after girdling and/or fertilizing are heavier, although there may be
fewer per cone [41].
Mineral soil seedbeds may be prepared by prescribed burning or
scarification. These treatments also reduce or delay competition
[112,116,117,118]. Seedling growth is best on north slopes under either
an open canopy or no canopy [96]. On sites with snowbrush (Ceanothus
spp.), seedlings planted in the first or second year were able to grow
as fast as the snowbrush, while natural regeneration was overtopped by
the snowbrush before it became established [128]. Western larch
seedlings survive planting better when they are dormant or close to
dormancy [129].
Overstocking is common in young stands and affects both height and
diameter growth [116]. Thinning allows trees to grow to a larger size
earlier in young, even-aged stands of western larch [121]. Thinning
from below between 10 and 15 years of age is best; thinning does not
appreciably increase growth of crop trees after 50 years of age
[14,105,120]. Removing competition by slashing increased 25-year-old
western larch height and diameter growth [42]. Thinning western larch
creates favorable conditions for shade-tolerant conifers and further
cleaning will maintain a vigorous stand [112,121]. Tables showing
average site indices for several habitat types and relationships between
height, potential d.b.h., volume, spacings, site index, and age or
habitat type are given [116]. Snow damage is normally not a problem for
this deciduous tree, as young western larch are supple and able to
recover rapidly if a late, heavy snow does occur [115].
Habitat for cavity-nesting species: Management recommendations for
maintaining populations of cavity-nesting birds while utilizing timber
include retaining a significant number of well-scattered, old-growth
western larch, ponderosa pine (Pinus ponderosa), or black cottonwood
(Populus trichocarpa) trees [77,78]. Optimum habitat for pileated
woodpeckers seems to be a midsuccessional forest with large overstory
western larch or ponderosa pine and snags housing carpenter ants for
winter food [46].
Insects and Disease: Larch casebearer (Coleophora laricella) and
western spruce budworm (Choristoneura fumiferana) are the most
destructive defoliating insects that feed on western larch [21,118].
While mortality due to larch casebearer is low, repeated defoliations
slow growth and may leave trees unable to maintain the dominance needed
to compete in a mixed stand. Defoliation also increases susceptibility
to other insects and diseases [116,118,121]. The biology of and
biological controls for larch casebearer have been studied in detail
[21,22]. Biological controls and adverse weather appear to be reducing
larch casebearer populations [116]. Western spruce budworm damages
cone-bearing twigs, cones, and seeds on western larch [12,106,126]. It
also reduces height growth and damages the form of young trees by
severing terminal and lateral shoots [27,118]. Because western larch is
not a preferred species, it may gain a competitive edge during severe
spruce budworm outbreaks [79]. A number of other insects cause lesser
amounts of damage to western larch foliage and seed crops [116,118,130].
Quinine fungus (Fomitopsis officinalis) and red ring rot (Phellinus
pini) frequently cause rot in western larch [4,116,118]. Annosus root
disease (Heterobasidion annosum) is rare on western larch but has been
observed in Idaho [151]. In British Columbia, western larch is very
susceptible to laminated root rot (Phellinus weirii var. pseudotsugae)
and a shoot blight disease (Encoeliopsis laricina). It is somewhat
susceptible to Armillaria root rot (Armillaria ostoyae) [141]. Larch
needle cast (Hypodermella laricis) and larch needle blight (Meria
laricis) both infect western larch in spring but apparently are most
severe in nurseries [36]. Many less common fungi infect western larch
[116,118].
Mistletoe: Western larch is susceptible to larch dwarf mistletoe
(Arceuthobium laricis) but immune to other dwarf mistletoes [56,56].
This mistletoe can cause serious problems, and in eastern Oregon and
eastern Washington, 84 percent of trees are infested with dwarf
mistletoe [10,116,118]. Dwarf mistletoe increases susceptibility to
other diseases [28]. Infested trees may die following thinning [28].
The use of thinning to control dwarf mistletoe in stands with western
larch has been described [28,107].
Herbicides: Use of mixtures of Esteron Brush Killer and diesel to
control shrubs causes t0p-kill in western larch [81]. Western larch is
susceptible to bromacil. It is resistant to 2,4-D and 2,4,5-T when
applied as a foliar spray but susceptible to both herbicides when
applied as a basal spray [11]. Procedures for the use of maleic
hydrazide and picloram to control larch are available [49].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Larix occidentalis | Western Larch
GENERAL BOTANICAL CHARACTERISTICS :
Western larch is a rapidly growing, deciduous, coniferous tree which may
live for more than 700 years [34]. Evidence provided by stumps in
Montana indicates that early cutting included western larch older than
900 years [30,66]. Trees may reach 260 feet (80 m) in height [58]. In
the Pacific Northwest a typical mature western larch is 164 feet (50 m)
tall and 55 inches (140 cm) d.b.h. [34].
Western larch has a deep and extensive root system that provides
moderate to high resistance to windthrow [118]. Short roots are
ectomycorrhizal [55]. The ectomycorrhizal root tips are found in
mineral soil more often than those of other conifers, although some are
also found in decayed wood and humus [52,53,54].
The thick bark of western larch is furrowed into large plates from which
cinnamon-colored scales may flake off [58]. The crown is relatively
short, narrow, and less dense than most conifers [82]. Young twigs are
glabrous or pubescent rather than tomentose like alpine larch [4,58].
The thin, light green, deciduous needles occur at the tips of short
lateral spur shoots in a whorl of 15 to 30 needles on a spur. Needles
on seedlings and leaders of older plants are decurrent and arranged in
spirals along the stem [4,58]. The deciduous habit allows larches to
avoid winter desiccation. Western larch can withstand defoliation by
insects or disease better than evergreen conifers and competes well with
them because its needles require less carbon to construct; it
efficiently relocates nitrogen before needlefall. Its photosynthetic
capacity is high, and its needles receive ample light through the open
crown [4,40].
RAUNKIAER LIFE FORM :
Undisturbed State: Megaphanerophyte
Disturbed State: Megaphanerophyte
Disturbed State: Therophyte
REGENERATION PROCESSES :
Cones: Although trees may produce some cones when 8 or 10 years old,
cone production is infrequent before the age of 25, and abundant
production does not begin until trees are 40 to 50 years old [116].
Good cone crops are produced irregularly but average 1 every 5 years
[116,118,131]. Cones are born on short spur branches; more female cones
occur the upper crown and more male cones in the central and lower crown
[25,58,106,116]. Since cones are produced throughout the crown, larger
trees produce most of the cone crop [116,131]. Details of pollination
and early seed development within western larch cones have been
described [92,93]. When mature, the reddish-brown to brown cones are
between 1 and 1.5 inches (2.5-4 cm) long and have thin, papery scales
and small, pointed bracts extending beyond each scale [4].
Seed: Western larch seeds are small, averaging 137,000 per pound
(302,000/kg), and light with a large wing [106]. It requires more
filled seed to establish a seedling when the seeds are light than when
they are heavy, as are the seeds of some other conifers [127]. In one
study it took an average of 53 filled seeds to produce a live western
larch seedling [127]. Western larch may form normal appearing but
inviable seeds if pollination does not occur or the embryo aborts [93].
Seeds are stratified naturally over winter and should be stratified for
prompt germination in nursery planting [71,106,133]. Seed treatments
are discussed by various authorities [132,133].
Seed dispersal: Cones open when they have dried to a moisture content
of 35 to 40 percent [91,116,125]. Generally over 80 percent of the
cones open by mid-October, although seed dispersal may extend into
winter [48,116]. The light seeds are dispersed by wind. Frequently,
they are carried 800 feet (250 m) and sometimes over 984 feet (300 m)
[33,76]. Patterns of dispersal in clearcuts show the amount of seed
decreases rapidly for the first 400 feet (122 m), then remains at a low
level. Thermal upslope winds aid dispersal at mid to low elevations,
but on upper slopes, where seed fall is later, storm fronts aid
dispersal [76].
Seedling establishment: Western larch seed germinates about the time of
snowmelt [116,133]. Normal first year growth is about 2 inches (5 cm),
but seedlings may grow to 5 inches (13 cm) in the Blue Mountains of
Oregon [85,116]. Germination is good on a variety of materials,
including duff, rotten wood, and mineral soil [31,73]. However,
survival is poor on undisturbed litter, humus, sod, and in areas with
heavy root competition. Survival is usually best in mineral soil.
Seedling roots are not able to penetrate layers of duff rapidly enough
to obtain sufficient water [126,127]. In central Idaho, the best growth
of 3- to 5-year-old western larch seedlings occurred on moss mats and
next best on bare mineral soil [38]. During early development, seedling
mortality is often caused by fungi, rodents, birds, and insects [116].
In the summer, most seedling mortality is caused by the physical factors
of excess heat (from insolation) or drought and is highest on south- and
west-facing slopes [122,132].
Vegetative reproduction: Western larch does not sprout. Researchers
have rooted cuttings and grafted western larch [116].
SITE CHARACTERISTICS :
Western larch is not as tolerant of summer drought as many other
conifers and is generally found on north- or east-facing slopes and
other relatively moist sites [2,33,82]. On drier sites at western
larch's lower elevation or southern range limits, it is frequently
unable to establish seedlings on south- or west-facing slopes, but in
moist areas in the middle and northern portion of its range, it grows on
all exposures [116]. Height growth is most rapid in valley bottoms and
on lower north and east slopes and poor on upper south- and west-facing
slopes [116].
Western larch in southwestern British Columbia is common in the interior
Douglas-fir zone, frequent in the interior cedar-hemlock and montane
spruce zones, and less frequent in the ponderosa pine zone [65,67]. In
mountain hemlock stands in northern Idaho and western Montana, it does
best below 5,600 feet (1,707 m) [43]. In the same region, it grows in
western redcedar, western hemlock, grand fir, moist subalpine fir, and
Douglas-fir habitat types [30,44,95]. In the Cascade Mountains of
northern Oregon, western larch is very frost tolerant and grows with
Pacific silver fir, mountain hemlock, fool's huckleberry (Menziesia
ferruginea), beargrass (Xerophyllum tenax), blue huckleberry (Vaccinium
membranaceum), grouse whortleberry (V. scoparium), bunchberry dogwood
(Cornus canadensis), and dwarf Oregon grape (Mahonia nervosa) [57].
Soil and soil nutrients: Usually western larch grows on soils
classified as Inceptisols and Alfisols and occasionally on Spodosols
[116]. Most of the soils supporting western larch developed in glacial
till or colluvium containing argillite, quartzite, and limestone
bedrock, and are deep and well drained [116]. Results of one study
indicate that trees growing on sites with compacted subsoil and thus
slow drainage grow well as juveniles, but growth slows when root growth
becomes restricted and nutrients in the rooting zone are depleted. In
contrast, trees on rapidly draining sites grow slower initially, but
subsequent productivity is higher [134].
In British Columbia, western larch grows on moderately dry to moist,
medium-nutrient-rich to very-nutrient-rich soils [65]. It needs high
levels of calcium and magnesium in the soil [67]. In many areas,
including western Montana, western larch is associated with moist soils
containing volcanic ash [87,116]. Western larch retranslocates 87
percent of foliage nitrogen before needle fall, possibly due to poor
soil availability and uptake of nitrogen [40,39].
Elevation: Elevational ranges in some western regions are [4,23]:
Minimum Maximum
feet meters feet meters
British Columbia 2,000 610 5,500 1,676
Montana 3,200 975 8,100 2,469
Oregon 3,000 930 7,000 2,134
Washington 2,000 610 5,500 1,676
SUCCESSIONAL STATUS :
Western larch is a long-lived and highly shade-intolerant seral species
[116]. It can tolerate partial shading only as a seedling. If it is
overtopped later, its crown deteriorates and it loses vigor and dies
[116,117]. For the first 100 years of life, larch grows faster in
height than any other conifer in the northern Rocky Mountains [116,118].
Since it is shade intolerant, it grows in even-aged stands, although
other tree species may appear younger because they are smaller. As
these stands mature, shade-tolerant conifers continue to establish and
form younger understories [116]. In the western redcedar-western
hemlock zone of northern Idaho and western Montana, western larch is
frequently a close associate of lodgepole pine (Pinus contorta) in
pioneer communities. It may be a minor element in these communities
initially, but fire recurrence during early succession can greatly
increase the proportion of western larch [44]. In the Garnet Mountains
of western Montana, western larch seems less able than lodgepole pine to
establish under an open canopy, and thus less shade tolerant [142].
SEASONAL DEVELOPMENT :
Leaves of western larch begin to develop early in spring before the
cambium becomes active. Spring growth appears to be controlled by
photoperiod rather than temperature [16]. The buds of western larch
flowers (conelets) are initiated in early spring, develop during the
summer, and remain dormant during fall and winter [91]. The following
spring, pollen and seed cones open before leaf buds, usually between
mid-April and mid-May. Pollination occurs in late May and early June
[116]. Cones ripen in August and seeds are dispersed in September and
October. At high elevations ripening and dispersal may occur 2 to 4
weeks later [76]. In October the needles turn from green to a golden
yellow before falling [2]. Results of an Idaho study indicate that the
time of leaf fall may be correlated with soil moisture [24].
Phenological observations of western larch made over a 10-year period in
northern Idaho and western Montana are summarized below [114]:
Earliest Average Latest
Date Date Date
Buds burst March 20 April 30 June 11
Terminal shoot
growth begins April 10 May 14 July 2
Pollen begins April 26 May 20 June 29
Pollen ends May 10 June 3 July 14
Shoot growth ends June 18 Aug. 1 Sept. 6
Winter buds formed July 11 Aug. 22 Oct. 11
Cones full size July 2 Aug. 6 Sep. 11
Cones open July 31 Sep. 4 Sep. 30
FIRE ECOLOGY
SPECIES: Larix occidentalis | Western Larch
FIRE ECOLOGY OR ADAPTATIONS :
Adaptations to Fire: Western larch is the most fire-resistant tree
species in the northern Rocky Mountains and interior Pacific Northwest.
It has very thick bark containing little resin, a high and open
branching habit, deep roots, and low-flammability foliage
[32,33,82,139]. At ground level the bark is often 6 inches (15.2 cm)
thick on mature trees [4]. The tendency of western larch to self-prune
lower branches and its tolerance of defoliation add to its fire
tolerance [30,19]. Fire favors the establishment of western larch
because it quickly invades openings, grows rapidly, and needs full
sunlight [152,113]. Western larch is very long-lived and able to
survive until fire creates a suitable seedbed [5,30].
Fire Regimes: In the northern Rocky Mountains, the results of a number
of studies suggest two distinct fire regimes for stands with western
larch as a seral dominant [6]. On relatively dry sites, usually with
Douglas-fir or Engelmann spruce as potential climax dominants, the
natural fire regime was one of fairly short mean fire intervals of 20 to
75 years. These intervals were shortened by recurring low- to
medium-intensity surface fires. On moist sites that included grand fir,
western hemlock, and western redcedar as potential climax species, fires
were severe stand-replacing burns at 120- to 350-year intervals
[2,3,6,18]. The interval between stand-replacing fires was over 100
years under both of these fire regimes [6].
In lower and drier mixed conifer communities in the Blue Mountains of
Oregon, the mean fire frequency of low surface fires before protection
was about every 10 years [46]. In the same area in drier Douglas-fir
and grand fir habitat types, the mean fire frequency of underburns was
20 to 30 years [116]. In higher elevation communities in this region,
severe crown fires occurred at 100- to 300-year intervals, allowing
western larch, lodgepole pine, and western white pine (Pinus monticola)
to dominate large stands [121].
Fuels: In the larch-Douglas-fir type of western Montana, fuel loading
ranges from 1.4 tons per acre (3.1 MT/ha) to 73.9 tons per acre (165.7
MT/ha) [29]. The following mean fuel loads were described for a study
in the western larch cover type in western Montana [119]:
Tons per Acre Metric Tons per Hectare
Total fuels 22.5 50.4
Small fuels (0.25-3 3.6 8.1
inches [0.6-7.6 cm])
Large fuels (>3 inches 17.7 39.7
[.7.6 cm])
Duff 1.2 2.7
POSTFIRE REGENERATION STRATEGY :
crown-stored residual colonizer; short-viability seed in on-site cones
off-site colonizer; seed carried by wind; postfire years one and two
FIRE EFFECTS
SPECIES: Larix occidentalis | Western Larch
IMMEDIATE FIRE EFFECT ON PLANT :
Mature western larch are able to withstand most fires; poles may survive
low to moderate fires [30,116]. Although young trees may survive high
temperatures for a short time, thin-barked seedlings and saplings are
readily killed by fire [19,33,116,117,118]. Bark thickness, crown
function, and tree vigor, as well as the characteristics of the fire,
are major factors that determine tree damage or death [110]. Trees that
are damaged by fire frequently succumb to insect attack or disease later
[110].
Mature western larch are most likely to be killed by fire after long
fire-free intervals in moist habitat types where true firs, western
hemlock, or western redcedar are potential climax. These dense stands
include low-branching conifers and tall shrubs or ladder fuels that can
carry fire into the crowns of western larch [19]. When ground fires
smolder in deep, dry duff, they can girdle even thick-barked trees
[110].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
Several factors are considered when predicting and modeling mortality of
western larch [110]. Cambial mortality depends on the duration of the
fire and thickness of the bark, which can be estimated by an equation
using tree diameter [108,109]. Crown damage depends on the amount of
bud kill, which may be observed with binoculars. Another indication of
crown kill is that a dead branch tends to retain the scorched needles
until they are removed by weather, while a live branch will drop the
dead needles promptly [109]. Nomograms have been developed that predict
mortality based on the bark thickness and crown scorch. These nomograms
and others showing scorch height, flame length, and fire intensity can
be used to help plan prescribed fires [100,102].
PLANT RESPONSE TO FIRE :
Even after large severe fires, scattered mature western larch survive
[147]. These survivers become seed trees for rapid restocking [2,70].
Fires that precede a good cone crop tend to favor western larch [63].
Western larch initiates new foliage growth shortly after being scorched
[110].
Western larch seedlings grow best on burned seedbeds [117,118]. Results
of a Montana study show numerous 3-year-old western larch seedlings
following a hot fire but very few on lightly burned areas [138].
Western larch seedlings and saplings have been found to grow one-third
faster on burned seedbeds than on bare mineral soil or duff-covered soil
[116]. This height increase might be due to changes in nutrients, water
infiltration, or competing vegetation. Increases in manganese,
magnesium, nitrogen, phosphorus, and calcium in upper soil layers have
been observed after fire [116].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
NO-ENTRY
FIRE MANAGEMENT CONSIDERATIONS :
When prescribed fire is used, western larch makes a good shelterwood
candidate in the Blue Mountains of Oregon [85]. Prescribed fire is
practical under a western larch shelterwood since the trees can
withstand normal prescribed fire intensities [113]. Planning such fires
is described in detail [64,85]. Such planning should recognize that
western larch needles have few surface deposits to slow moisture
movement and thus fuel moisture response times are shorter than those
for other conifer needles [1]. Near its southern limit in central
Idaho, western larch stands reflect past severe disturbance from
wildfire. At present, however, it is not regenerating well following
broadcast burns or scarification. Reasons for this may include
insufficient seed trees and marginal conditions for seedling
establishment [140].
Several researchers have modeled forest succession following fire,
including the life history and response of western larch [13,30,62].
Such information can be useful in setting management objectives. The
response of western larch and other conifers following repeated fires at
10-, 20-, and 50-year intervals, a simulated natural fire frequency, or
fire supression has been described by a computer model [60].
FIRE CASE STUDIES
SPECIES: Larix occidentalis | Western Larch
1. Lubrecht Experimental Forest: larch/Douglas-fir prescribed fire
2. Miller Creek-Newman Ridge: larch/Douglas-fir prescribed- and wildfire
1st CASE NAME :
Lubrecht Experimental Forest: larch/Douglas-fir prescribed fire
REFERENCES :
Norum, R. A. 1975 [88]
Norum, R. A. 1976 [89]
Norum, R. A. 1977 [90]
Reinhardt, E. D.; Ryan, K. C. 1988 [100]
Stark, N. 1977 [135]
Stark, N.; Steele, R. 1977 [138]
SEASON/SEVERITY CLASSIFICATION :
Spring and fall/low to moderate severity
STUDY LOCATION :
The study site is on the University of Montana Lubrecht Experimental
Forest located 41 miles (66 km) east of Missoula in the Garnet Mountains
(north half of Section 3, T. 13 N, R. 15 W, Principal Meridian,
Montana).
PREFIRE VEGETATIVE COMMUNITY :
Study plots were in a Douglas-fir/globe huckleberry (Pseudotsuga
menziesii/Vaccinium globulare) habitat type, bearberry (Arctostaphylos
uva-ursi) phase as described by Pfister and others [95]. Overstory
trees ranged in age from 50 to 300 years with an average diameter of
about 8.6 inches (22 cm). This stand was not vigorous and was composed
primarily of Douglas-fir and western larch (Larix occidentalis) with
small amounts of lodgepole pine (Pinus contorta) and ponderosa pine (P.
ponderosa). The largest and best trees had been selectively logged
about 50 years earlier. Subsequently, an uneven understory of dense
Douglas-fir had developed. There were a large number of widely spaced,
large-diameter western larch stumps to indicate preharvest conditions.
In addition to conifers and bearberry, huckleberries (Vaccinium spp.),
birchleaf spirea (Spiraea betulifolia), and heartleaf arnica (Arnica
cordifolia) were common in the understory.
TARGET SPECIES PHENOLOGICAL STATE :
NO-ENTRY
SITE DESCRIPTION :
The site is located at about 4,800 feet (1,464 m) with east to northeast
exposures and slopes of 20 to 50 percent. The area has warm summers and
cold winters with annual precipitation of about 18 inches (47 cm), most
of which falls as winter snow. Soils in the area are thin, poorly
developed sandy loams in the Holloway Series. They formed in residuum
weathered from quartzite, argillite and, on these sites, contain
sufficient rock to be considered talus slopes. Calcium and phosphate
are limited in these soils. The site had a substantial complex fuel
load including many dead small trees in understory thickets. Total dead
fuel loadings ranged from 5.5 to 50 tons per acre (12.3-112.1 metric
tons/ha). Over 100 parameters were measured in connection with these
fires.
FIRE DESCRIPTION :
Out of the 20 test plots broadcast burned during 1973, nine were burned
from early May to the first of July. The rest were burned from early
September to mid-October. The average dead fuel moisture contents
ranged from 8.5 to 35 percent and windspeeds were from 0 to 15 miles per
hour (0-24 km/hr). Strip ignition horizontally across plots was used
for most plots, and fire intensity on each strip was allowed to drop
before the next strip was ignited.
FIRE EFFECTS ON TARGET SPECIES :
Three years after the fires the average cover of western larch seedlings
on lightly burned plots was 0.27 percent; on moderately burned plots was
0.23 percent; on hotly burned sites was 2.4 percent; and no western
larch seedlings had established on control plots. Nutrient analyses
were done on prefire and postfire soil, soil water and plants. Results
of comparison of nutrients from aboveground samples of western larch
seedlings from burned and control plots were:
micrograms/gram
Control Hot burn
Calcium 4,805 3,000
Copper 37 18
Iron 162 280a
Potassium 6,864 16,000a
Magnesium 967 1,300a
Manganese 343 198
Sodium 114 95
Phosphorus 4,457 7,190a
Zinc 28 37a
(a) indicates a significant difference at the 5 percent level.
Eight years after the fires a tree growth analysis was performed limited
to radial and basal area growth. Western larch's relative radial
increment on burned plots was less than on unburned plots in the first
year and greater on burned plots thereafter. The difference in growth
of trees on burned plots compared to trees on control plots increased
each year for the first 4 years. Western larch's response was more
positive than that of Douglas-fir and from the fourth to the eighth year
the average relative radial increment was 60 to 80 percent greater on
burned plots than on unburned plots. The average unadjusted radial
growth increment of trees on burned and unburned plots for the first 8
years after treatment is given below:
Year Burned Unburned
inches cm inches cm
1 0.044 .114 0.048 .121
2 0.059 .150 0.054 .136
3 0.076 .193 0.055 .139
4 0.069 .175 0.036 .091
5 0.068 .173 0.037 .093
6 0.056 .143 0.034 .087
7 0.067 .171 0.037 .093
8 0.071 .181 0.042 .106
FIRE MANAGEMENT IMPLICATIONS :
Underburning in similar western larch/Douglas-fir forests is feasible.
An average of 15 percent of the overstory trees were killed in the
plots. Within the range of fuel loadings in this study, fires were most
manageable and still effective when the moisture content of 0 to 1 inch
(0-2.5 cm) dead fuels was around 15 percent. Strip ignition helped
overcome control and ignition problems caused by discontinuous
concentrations of heavy fuels. Underburning requires attention to the
form, moisture status, and amount of living vegetation. Detailed
prescriptions for underburning are given in Norum [1976 and 1977].
Western larch seedlings established best on sites burned by the hottest
fires. Prescribed underburns in western larch stands can result in an
increase in individual tree relative radial increment. However, growth
of western larch in these poorly growing stands continued to be slow.
Growth, even in trees with fire damage, was not reduced by the fire, and
fire may be a useful tool for fuel reduction or other purposes in such
stands.
FIRE CASE STUDIES
SPECIES: Larix occidentalis | Western Larch
2nd CASE NAME :
Miller Creek-Newman Ridge: larch/Douglas-fir prescribed- and wildfire
REFERENCES :
Beaufait, W. R.; Hardy, C. E.; Fischer, W. C. 1977 [7]
DeByle, N. V. 1981 [20]
Shearer, R. C. 1975 [123]
Shearer, R. C. 1976 [124]
Shearer, R. C. 1982 [128]
Shearer, R. C. 1984 [129]
Shearer, R. C. 1989 [153]
SEASON/SEVERITY CLASSIFICATION :
May through October/low to very severe
STUDY LOCATION :
Two study locations were used. The first contained 641 acres in the
Miller Creek and Martin Creek drainages of the Flathead National Forest
of northwestern Montana. This is referred to as the Miller Creek area.
The second location consisted of 526 acres on Newman Ridge located
between Two Mile Creek and Ward Creek on the Lolo National Forest near
the border of western Montana and Idaho.
PREFIRE VEGETATIVE COMMUNITY :
Most of Miller Creek was considered to be in one of three phases of the
subalpine fir/queencup beadlily (Abies lasiocarpa/Clintonia uniflora)
habitat type. The fool's huckleberry (Menziesia ferruginea) phase was
found on higher middle and upper north- and east-facing slopes. The
beargrass (Xerophyllum tenax) phase was on drier south and west aspects
and the queencup beadlily phase on most other sites. Stream bottoms
belonged to the western redcedar(Thuja plicata)/queencup beadlily
habitat type. The dominant conifers were western larch (Larix
occidentalis), Douglas-fir (Pseudotsuga menziesii), and Engelmann spruce
(Picea engelmannii), with some lodgepole pine (Pinus contorta), grand
fir (Abies grandis), and subalpine fir. The larch/Douglas-fir cover
type occupied over 50 percent of the area.
On Newman Ridge seven habitat types were identified. The warmest and
driest was the Douglas-fir/ninebark (Physocarpus malvaceus) habitat type
on convex southwest slopes. Other habitat types included grand
fir/queencup beadlily on concave east, northwest, and protected
south-facing slopes; grand fir/beargrass on upper west-facing slopes;
western redcedar/queencup beadlily h.t., fool's huckleberry phase on
concave north- and northeast-facing slopes; Douglas-fir/globe
huckleberry (Vaccinium globulare) h.t. beargrass phase on upper
south-facing slopes; subalpine fir/queencup beadlily h.t., fool's
huckleberry phase on north slopes along the ridge; and subalpine
fir/beargrass h.t., globe huckleberry phase on south slopes near the
ridge. Dominant conifers were Douglas-fir, larch and lodgepole pine
with some ponderosa pine (Pinus ponderosa), grand fir, subalpine fir,
western white pine (Pinus monticola), Engelmann spruce and western
redcedar. Prefire stands at Newman Ridge were 26 percent western larch.
TARGET SPECIES PHENOLOGICAL STATE :
NO-ENTRY
SITE DESCRIPTION :
Elevation at Miller Creek ranges from 4,200 to 5,000 feet (1,280-1,524
m) with slopes averaging 24 percent and ranging from 9 to 35 percent.
Soils are Andic Cryoboralfs that developed in glacial till from the
argillites and quartzites of the Wallace (Belt) formation. Average
precipitation is about 25 inches (64 cm) annually; approximately
two-thirds falls as snow during the long cool winter. Elevation at
Newman Ridge ranges from 4,400 to 5,400 feet (1,341-1,646 m) with slopes
averaging 55 percent and ranging from 44 to 76 percent. Soils are Andic
Cryochrepts that have developed in place or in colluvium from argillites
and quartzites of the Belt formation. There is a surface loess deposit
containing ash from the Mt. Mazama and Glacier Peak volcanic eruptions
at both sites which is 0.5 to 2.5 inches (1-6 cm) thick at Miller Creek
and 2 to 3 inches (5-8 cm) thick at Newman Ridge. Average precipitation
is nearly 40 inches (102 cm) at Newman Ridge of which two-thirds falls
as snow.
Sixty 10-acre (4-ha) treatment units were established at Miller Creek
and 16 units, ranging in size from 20 to 58 acres (8-24 ha), were
established at Newman Ridge. One-fourth of the units at each site
generally faced each of the four cardinal directions. The units were
clearcut, slashed and burned. Fuel loads after clearcutting and before
fire, excluding duff, ranged from 60 to 165 tons per acre (135-370
metric tons/ha). Average fuel loads are described below:
Average Miller Creek Newman Ridge
Weight tons/acre kg/square m tons/acre kg/square m
Duff 26.3 59.1 22.9 51.3
Needles 1.5 3.5 1.4 3.1
0 to 1 cm 1.3 2.9 1.1 2.5
1 to 10 cm 9.8 22.1 10.7 24.0
> 10 cm 101.3 227.0 90.5 202.8
Total 140.3 314.5 126.5 283.7
FIRE DESCRIPTION :
Slash fuels were allowed to cure for an average of 9 months before
burning (2 to 18 months range). Fuel moisture of 0 to 0.4 inch (0-1 cm)
branchwood ranged from 5 to 21 percent. Burning patterns and fire
severity varied among the plots burned. After broadcast burns at Miller
Creek, 75 percent of the fuels less than 3.9 inches (10 cm) burned and
60 percent of the larger fuels burned. At Newman Ridge 89 percent of
the fuels less than 3.9 inches (10 cm) burned and 55 percent of the
larger fuels burned. Greater surface soil heating occurred at Newman
Ridge than at Miller Creek because the duff layer was shallower and
water content of both duff and soil was lower. The average duff
reduction ranged from 36 to 70 percent at Miller Creek and 44 to 99
percent at Newman Ridge. In 1967 a wildfire burned five units that had
been clearcut and four units that were uncut forest at Miller Creek.
Average duff reduction from the wildfire was 93 percent with a range of
84 to 100 percent.
FIRE EFFECTS ON TARGET SPECIES :
Seedbeds were varied. Early 1967 and most 1968 fires did not completely
burn litter and duff or expose much mineral soil. The 1967 wildfire
consumed most of the duff and killed most roots of sprouting species.
Other fires were spotty and exposed some mineral soil. Very few western
larch seedlings established on unburned duff. Unburned duff continued
to decrease for several years exposing bare soil on areas where the fire
had left charred duff. The reasons for this decrease may include:
increased decomposition stimulated by warmer surface temperature during
May and June where adequate moisture was present; redistribution by
precipitation, runoff or wind; and oxidation. However, since western
larch needs to establish quickly and become dominant, this may benefit
other conifer species more. In addition to natural seeding, seeds were
sown in 1967 on test plots, and bareroot seedlings were planted on
Newman Ridge from 1970 through 1975 and on four clearcuts at Miller
Creek from 1970 through 1973.
Postfire seed dispersal into the clearcuts from western larch in the
timber around clearcut areas was good. The best seed year for all
conifers was 1971; however, heavy frost in May of that year decreased
the potential western larch seed crop. The cumulative average number of
sound seed of western larch from 1969 through 1974 on eight clearcuts on
Newman Ridge by distance from the source is listed below:
Within Distance from timber edge within clearcut
Timber 0-200 ft 200-400 ft 400-600 ft 600-800 ft
(0-61 m) (61-122 m) (122-183 m) (183-244 m)
/acre 53,200 7,500 3,700 2,000 800
/ha 131,500 18,600 9,200 4,900 1,900
Germination of western larch began before the snow completely melted and
was greater on mineral soil than on unburned duff more than 0.5 inch (13
mm). Seed and seedling losses were caused by rodents, drought, frost
heaving, high temperatures at the soil surface, and migrating juncos
that ate emerging seedlings in 1968. Drought was the leading cause of
death on south-facing slopes and second highest on other aspects.
Natural regeneration was lowest on south-facing slopes. In 1978 at
Miller Creek, stocking of western larch seedlings averaged 54 percent on
burned units and 5 percent on unburned clearcuts. By 1984 at Miller
Creek, stocking of established seedlings of western larch averaged 71
percent on burned units and 1 percent on unburned clearcuts. In 1979 at
Newman Ridge, stocking of established western larch seedlings averaged
10 percent (6%-16%) on burned clearcuts. The average number of
established (>1 foot (30.5 cm) in height) western larch seedlings per
acre (hectare) in 1979 and 1984 and the range in 1984 on 37 burned units
at Miller Creek and 7 burned clearcuts at Newman Ridge are given below:
1979 1984 1984
Average Average Range
Miller Creek
/acre 610 931 92-4,003
/hectare 1,507 2,301 227-9,892
Newman Ridge
/acre 30 91 10-228
/hectare 74 225 25-563
At Miller Creek in 1978, the tallest western larch seedlings averaged
8.5 feet (2.6 m) on uncut plots burned by the wildfire, 5.3 feet (1.6 m)
on clearcuts that were burned by the wildfire, and 3.7 feet (1.1 m) on
clearcuts that were burned by prescribed fire in 1967. This sequence
may be because a greater proportion of the western larch were older on
the uncut units burned by wildfire or because the evapotranspiration was
lower and the number of growing days greater on those units. Height was
also related to habitat type and phase with the tallest trees on the
warmer and drier beargrass phase of the subalpine fir/queencup beadlily
habitat type and shorter trees on the cooler and moister fool's
huckleberry phase. Evidently, soil moisture is not as limiting in early
stand development as it is later; also, trees on the warmer sites began
growth earlier in the spring and may have benefited from extra nitrogen
contributed by snowbrush ceanothus (Ceanothus velutinus). At Newman
Ridge in 1979, the tallest western larch seedlings averaged 3.0 feet
(0.9 m). Natural regeneration of western larch at Newman Ridge was
lower than at Miller Creek due to harsh site conditions, larger
clearcuts, and poor seed production which resulted in less stocking than
expected from the previous stand composition.
FIRE MANAGEMENT IMPLICATIONS :
During late spring and early summer, duff is usually wet and fires do
not expose much mineral soil. Late summer or early fall fires are more
effective at removing duff and exposing mineral soil for western larch
regeneration. However, if precipitation occurs, fuels and duff need to
dry for several days. At Newman Ridge, moderate intensity fires removed
most of the duff and prepared an adequate seedbed. At Miller Creek, the
same intensity fire exposed less mineral soil because the duff was
thicker and wetter. Habitat type and site conditions alter the amount
of duff removal needed. On mesic habitat types hot fires that expose a
high proportion of mineral soil, followed by good seed years, lead to
overstocking. On steeper slopes with drier conditions, such as at
Newman Ridge, residual duff layers have more adverse impact on the
survival of seedlings.
Seed dispersal should be taken into account when deciding the time of
fall fires. In a good seed year, dispersed seed could be destroyed by
fires after early September at lower elevations and a few weeks later at
higher elevations. The light seeds of western larch enable it to
establish a high proportion of the seedlings in the center of larger
clearcuts such as those on Newman Ridge. Planting may be necessary on
steep, harsher sites. Expected survival for planted western larch on
such sites at Newman Ridge was high in the western redcedar/queencup
beadlily habitat type; moderate in the grand fir/queencup beadlily,
grand fir/beargrass, and Douglas-fir/globe huckleberry habitat types;
and low in the Douglas-fir/ninebark habitat type. Actual survival by
1979 was lower than expected, only 38 percent for western larch overall.
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150. Willard, E. Earl; Bedunah, Donald J.; Hann, Wendell. 1983. Forage and livestock in western Montana. In: O'Loughlin, Jennifer; Pfister, Robert D., eds. Management of second-growth forests, the state of knowledge and research needs: Proceedings of a symposium; 1982 May 14; Missoula, MT. Missoula, MT: University of Montana, School of Forestry, Montana Forest and Conservation Experiment Station: 187-208. [7101]
151. Williams, Ralph E. 1989. Distribution and impacts of annosus root disease in forests of the northern Rocky Mountains. In: Otrosina, William J.; Scharpf, Robert F., technical coordinators. Proceedings of the symposium on research and management of annosus root disease (Heterobasidion annosum) in western North America; 1989 April 18-21; Monterey, CA. Gen. Tech. Rep. PSW-116. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station: 51-56. [11322]
152. Arno, Stephen F. 1985. Ecological effects and management implications of Indian fires. In: Lotan, James E.; Kilgore, Bruce M.; Fisher, William C.; Mutch, Robert W., technical coordinators. Proceedings--Symposium and workshop on wilderness fire; 1983 November 15-18; Missoula, MT. Gen. Tech. Rep. INT-182. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station: 81-86. [7357]
[7357] Index
Related categories for Species: Larix occidentalis
| Western Larch
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