Sierra Nevada Bioregion
JAN W. VAN WAGTE N D O N K AN D J O AN N F ITE S-KAU F MAN
In the main forest belt of California, ﬁres seldom or never sweep
from tree to tree in broad all-enveloping sheets . ... Here the ﬁres
creep from tree to tree, nibbling their way on the needle-strewn
ground, attacking the giant trees at the base, killing the young,
and consuming the fertilizing humus and leaves.
The Sierra Nevada is one of the most striking features of the The relatively moderate western slope of the Sierra Nevada
state of California, extending from the southern Cascade is incised with a series of steep river canyons from the Feather
Mountains in the north to the Tehachapi Mountains and River in the north to the Kern River in the south. As the moun-
Mojave Desert 700 km (435 mi) to the south (Map 12.1). tain block was uplifted, the rivers cut deeper and deeper into
The Central Valley forms the western boundary of the Sierra underlying rock (Huber 1987). The foothills are gently rolling
Nevada bioregion, and the Great Basin is on the east. The with both broad and narrow valleys. At the mid elevations,
bioregion includes the central mountains and foothills as landforms include canyons and broad ridges that run prima-
described by the Sierra Nevada Section and the Sierra rily from east-northeast to west-southwest. Rugged mountain-
Nevada Foothills Section of Miles and Goudey (1997). The ous terrain dominates the landscape at the higher elevations.
area of the bioregion is 69,560 km2 (26,442 mi2), approxi- The oldest rocks of the Sierra Nevada were metamor-
mately 17% of the state of California. Signiﬁcant features phosed from sediments deposited on the sea floor that
along the length of the range include Lake Tahoe, Yosemite collided with the continent during the early Paleozoic Era
Valley, and Mount Whitney. (Huber 1987). These rocks grade into early Mesozoic Era
metasediments and metavolcanics west of the crest of the
Sierra Nevada. Granites began to form 225 million years
Description of the Bioregion
ago, and pulses of liquid rocks continued for more than
The natural environment of the Sierra Nevada is a function 125 million years, forming the granite core of the range
of the physical factors of geomorphology, geology, and (Schweickert 1981). During the first half of the Tertiary
regional climate interacting with the available biota. These Period, mountains were uplifted and erosion stripped the
factors are inextricably linked to the abiotic and biotic metamorphic rocks from the granite and exposed large
ecosystem components including local climate, hydrol- expanses of the core throughout the range. Meandering
ogy, soils, plants, and animals. The distribution and abun- streams became deeply incised as gradients became steeper.
dance of the ecological zones of the Sierra Nevada are By the Eocene Epoch, about 55 million years ago, this high
directly influenced by these interactions. The ecological “proto-Sierra Nevada” had been eroded into an Appalachian-
role of fire in the bioregion varies with changes in the nat- like chain of low mountains. Violent volcanic eruptions
ural environment. during the second half of the Tertiary Period blanketed
much of the subdued landscape of the northern Sierra
Nevada and portions of the higher central Sierra Nevada
with ash that dammed streams, ﬁlled narrow valleys, and
covered passes (Hill 1975). Today, volcanic rocks occur pri-
The Sierra Nevada is a massive block mountain range that
marily in the northern and central Sierra Nevada, although
tilts slightly to the south of west and has a steep eastern
small outcrops can be seen throughout the range. The
escarpment that culminates in the highest peaks. This block
sharp relief and high altitude of the modern Sierra Nevada
of the Earth’s crust broke free along a bounding fault line and
are the products of recent uplift associated with extension
has been uplifted and tilted (Huber 1987). Elevations range
of the Great Basin. This uplift began 2 to 3 million years
from 150 m (492 ft) on the American River near Sacramento
ago and continues today.
to 4,418 m (14,495 ft) at Mount Whitney.
ba Blue Canyon
Yu Lake Tahoe
ne R Sonora Pass
lu m n e R .
uo Yosemite Valley
Sequoia/Kings Canyon NP
MAP 12.1. The Sierra Nevada bioregion. Locations mentioned in the
text are shown on the map.
TA B L E 12.1
Normal maxima, normal minima, record high, and record low temperatures at Blue
Canyon, elevation 1,609 m (5,391 ft), northern Sierra Nevada
Normal Daily Normal Daily
Maximum Minimum Record High Record Low
( C) ( C) ( C) ( C)
January 6.4 0.8 21.7 15.0
February 6.3 0.7 22.8 14.4
March 7.9 0.4 22.2 12.8
April 11.7 3.3 25.6 8.3
May 15.7 6.7 30.0 6.l
June 19.6 10.6 33.3 2.2
July 25.0 15.0 32.8 4.4
August 24.8 13.8 33.3 1.7
September 22.2 12.2 33.9 1.7
October 16.8 7.4 29.4 5.6
November 12.1 3.1 25.6 0.6
December 8.6 0.6 23.9 2.8
F I R E CLI MATE VAR IAB LE S
During the Pleistocene Epoch, snow and ice covered most
of the high country, and glaciers ﬁlled many of the river val-
The primary sources of precipitation are winter storms that
leys (Hill 1975). Several glaciations are recognized to have
move from the north Paciﬁc and cross the Coast Ranges and
occurred in the Sierra Nevada, but only two can be recon-
Central Valley before reaching the Sierra Nevada. The coastal
structed with conﬁdence (Huber 1987). The Tahoe glaciation
mountains catch some of the moisture, but the gap in the
reached its maximum extent about 60,000 to 75,000 years
mountains near San Francisco Bay allows storms to pass
ago, whereas the Tioga glaciation peaked about 15,000 to
through producing the heaviest precipitation to occur in the
20,000 years ago. These glaciers further deepened valleys and
Sierra Nevada in areas to the east and north. As the air masses
scoured ridges, leaving the exposed granite landscape so
move up the gentle western slope, precipitation increases
prevalent today. Modern glaciers are scattered on high peaks
and, at the higher elevations, falls as snow. Once across the
between Yosemite and Sequoia National Parks.
crest, most of the moisture has been driven from the air mass
Seven soil orders occur in the Sierra Nevada. Alﬁsols are
and precipitation decreases sharply. Precipitation also
formed under forest cover with the bulk of the annual pro-
decreases from north to south with nearly twice as much
duction of organic matter delivered above ground. Andisols
falling in the northern Sierra Nevada as does in the south.
most commonly occur on steep slopes formed by volcanic
Mean annual precipitation ranges from a low of 25 cm (10 in)
activity. Aridisols occur in semi-arid areas where local condi-
at the western edge of the foothills to more than 200 cm (79
tions impose aridity. Entisols and Inceptisols are found where
in) north of Lake Tahoe. More than half of the total precipi-
climate or bedrock limits soil development. Most Mollisols
tation falls in January, February, and March, much of it as
have formed under meadow or grassland vegetation. Deeply
snow. Summer precipitation is associated with afternoon
weathered Ultisols develop in moist, cold areas under acidic
thunderstorms and subtropical storms moving up from the
conditions. The different soil orders occur in combination
Gulf of California.
with wet, frigid or frozen soil temperature regimes and dry to
Sierra Nevada temperatures are generally warm in the sum-
aquatic soil moisture regimes.
mer and cool in the winter. Table 12.1 shows normal
monthly maxima and minima and highest and lowest tem-
peratures recorded for the Blue Canyon weather station at
1,609 m (5,391 ft) in the northern Sierra Nevada. Tempera-
The pattern of weather in the Sierra Nevada is inﬂuenced by tures decrease as latitude and elevation increase, with a tem-
its topography and geographic position relative to the Cen- perature lapse rate of approximately 6.5°C with each 1,000 m
tral Valley, the Coast Ranges, and the Paciﬁc Ocean. Winters of elevation (3.3°F in 1,000 ft). At Blue Canyon, normal
are dominated by low pressure in the northern Paciﬁc Ocean 10:00 am relative humidity is highest in January at 60% and
while summer weather is inﬂuenced by high pressure in the lowest in July at 30%. Extremely low relative humidity is
same area. common in the summer. Wind speeds are variable, averaging
266 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
W EATH E R SYSTE M S
Fires are associated with critical ﬁre weather patterns that
occur with regularity during the summer (Hull et al. 1966). For
California, there are four types of patterns: (1) the Paciﬁc
High–Post-Frontal, (2) the Great Basin High, (3) the Subtropical
High Aloft, and (4) the Meridional Ridge with Southwest Flow
Aloft. The Paciﬁc High–Post-Frontal type is a surface type where
air from the Paciﬁc moves in behind a cold front and causes
north to northwest winds in northern and central California
(Hull et al. 1966). A foehn effect is produced by steep pressure
gradients behind the front causing strong winds to blow down
slope. The Great Basin High type often follows the Paciﬁc
High–Post-Frontal type with air stagnating over the Great Basin.
Combined with a surface thermal trough off the California
coast, the Great Basin High creates strong pressure gradients and
easterly or northeasterly winds across the Sierra Nevada (Hull
et al. 1966). Although this type is often present during winter
months when ﬁres are not expected to occur, the Great Basin
High can produce extreme ﬁre weather during the summer.
During the Subtropical High Aloft type, the belt of westerly
winds is displaced northward and a stagnant air pattern effec-
tively blocks advection of moist air from the Gulf of Mexico.
High temperatures and low relative humidities are associated
with this type. The Meridional Ridge with Southwest Flow
pattern requires a ridge to the east and a trough to the west,
allowing marine air penetration in coastal and inland areas.
Above the marine layer in the Sierra Nevada, temperatures
are higher and relative humidities are lower as short wave
troughs and dry frontal systems pass over the area (Hull et al.
MAP 12.2. Spatial distribution of lightning strikes in the Sierra 1966). Table 12.3 shows the percentage of days each month
Nevada bioregion, 1985–2000. The density increases from west to
that would be expected to have each critical ﬁre weather pat-
east and reaches a maximum just east of the crest north of Sonora
tern based on records from the Blue Canyon station. During
June, July, and August, the maximum temperatures associ-
ated with each of these types range from 27°C to 33°C
(81°F–91°F) and the relative humidity from 8% to 21%.
up to 11 km hr 1 (7 mi hr 1) but have been recorded as high
as 113 km hr 1 (70 mi hr 1) out of the north at Blue Canyon
The vegetation of the Sierra Nevada is as variable as its topog-
Lightning is pervasive in the Sierra Nevada, occurring in
raphy and climate. In response to actual evapotranspiration
every month and on every square kilometer with over 210,000
and the available water budget, the vegetation forms six
strikes occurring from 1985 through 2000 (van Wagtendonk
broad ecological zones that roughly correspond with eleva-
and Cayan 2007). However, there are spatial and temporal
tion (Stephenson 1998). These zones include: (1) the foothill
patterns. Map 12.2 shows the spatial distribution of the aver-
shrubland and woodland zone, (2) the lower-montane forest
age annual number of lightning strikes for the 16-year period.
zone, (3) the upper-montane forest zone, (4) the subalpine
The highest concentration of lightning strikes occurs 15 km
forest zone, (5) the alpine meadow and shrubland zone, and
(9.3 mi) northeast of Sonora Pass. In the Sierra Nevada, there
(6) the eastside forest and woodland zone. These zones are
is a strong correlation between the number of lightning
arranged in elevation belts from the Central Valley up to the
strikes and elevation, with strikes increasing with elevation
Sierra Nevada crest and back down to the Great Basin (Fig.
(Fig. 12.1) (van Wagtendonk 1991a). Summer afternoon heat-
12.2). The ecological zones increase in elevation from the
ing of slopes causes uplift in the mountains and results in the
north to southern Sierra Nevada.
development of thunderstorms. Ridge tops receive more
strikes than valley bottoms, but there is no signiﬁcant rela-
FO OTH I LL S H R U B LAN D AN D WO ODLAN D
tionship between strikes and either slope steepness or aspect.
The foothill shrubland and woodland zone covers 15,777
The temporal distribution of lightning strikes is shown in
km2 (5,993 mi2) from the lowest foothills at 142 m (466 ft) to
Table 12.2. The greatest number of strikes occurs in the after-
occasional stands at 1,500 m (5,000 ft), reaching a maximum
noon in July and August.
S I E R R A N E VA D A B I O R E G I O N 267
F I G U R E 12.1. Lightning strikes by ele-
vation in the Sierra Nevada bioregion,
1985–2000. The density of strikes is
greatest at 3,000 m and decreases as ele-
vation increases above that point.
TA B L E 12.2
Temporal distribution of lightning strikes by 2-month and 4-hour periods for the Sierra Nevada, 1985–2000
Number of Strikes
Hour Jan–Feb Mar–Apr May–Jun Jul–Aug Sep–Oct Nov–Dec Total
0–4 88 159 1,661 3,645 1,505 156 7,214
4–8 61 111 858 6,402 1,919 39 9,390
8–l2 105 610 7,946 21,902 4,204 85 34,852
12–16 665 3,688 28,124 64,692 17,430 377 114,976
16–20 482 1810 10,025 15,344 6,685 762 35,110
20–24 162 434 3,344 2271 1723 801 8,735
Total 1,565 6,812 51,958 114,256 33,466 2,220 210,277
extent between 150 m and 300 m (1,000–1,500 ft). The mixed conifer, Douglas-ﬁr (Pseudotsuga menziesii var. men-
primary vegetation types in this zone are foothill pine– ziesii) mixed conifer, and mixed evergreen forests. Inter-
interior live oak (Pinus sabiniana-Quercus wislizenii) woodlands, spersed within the forests are chaparral stands, riparian
mixed hardwood woodlands, and chaparral shrublands. Blue forests, and meadows and seeps.
oak (Quercus douglasii) woodlands occur at the lower end of
the zone and are treated in Chapter 13 (Central Valley Biore- U P P E R MONTAN E FOR E ST
This ecological zone covers 11,383 km2 (4,324 mi2) and
extends from as low as 750 m (2,500 ft) to 3,450 m (11,500 ft).
LOW E R-MONTAN E FOR E ST
The upper-montane forest is most widely spread between
1,950 and 2,100 m (6,500–7,000 ft) where it covers 1,800 km2
The lower montane forest is the most prevalent zone in Cal-
(695 mi2). Forests within this zone include extensive stands
ifornia and in the Sierra Nevada bioregion, occupying 21,892
km2 (8,316 mi2) primarily on the west side of the range just of California red ﬁr (Abies magniﬁca var. magniﬁca) along
above the foothill zone. Ninety-ﬁve percent of the stands with occasional stands of western white pine (Pinus monti-
occur below 2,400 m (8,000 ft), and the greatest occupied cola). Woodlands with Jeffrey pine (Pinus jeffreyi) and Sierra
area is between 1,500 and 1,650 m (5,000–5,500 ft). Major juniper (Juniperus occidentalis ssp. australis) occupy exposed
vegetation types include California black oak (Quercus kelloggii), ridges, whereas meadows and quaking aspen (Populus tremu-
ponderosa pine (Pinus ponderosa), white ﬁr (Abies concolor) loides) stands occur in moist areas.
268 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
TA B L E 12.3
Percent of days each month with critical ﬁre weather types for Blue Canyon, 1951–1960
Percentage of Days Per Month
Weather Type Mar Apr May Jun Jul Aug Sep Oct Nov Dec–Feb
Paciﬁc High, 6.8 8.0 5.2 7.0 3.2 4.5 5.7 7.4 5.3 4.9
Great Basin High 16.1 12.0 11.3 11.0 7.4 6.1 12.3 18.7 15.7 16.1
Subtropical 0.0 0.0 0.0 10.3 32.3 24.8 16.3 1.6 0.0 0.0
Meridional Ridge 3.9 6.3 11.6 17.0 16.5 27.4 17.3 9.0 7.7 1.9
SW Flow Aloft
F I G U R E 12.2. Area of ecological
zones by 500-m elevation bands. The
elevational distribution of ecological
zones is evident as area cover by each
zone increases and then decreases as
S U B A LP I N E FOR E ST zone extends from 2,000 m (7,000 ft) to 4,350 m (14,500 ft),
with the largest area between 3,300 m and 3,450 m
The subalpine forest zone ranges from 1,650 m (5,500 ft) to
(11,000–11,500 ft). Willow (Salix spp.) shrublands and alpine
3,450 m (11,500 ft) and reaches its maximum extent between
fell ﬁelds containing grasses, sedges, and herbs are the dom-
3,000 m to 3,450 m (9,500–10,000 ft). The subalpine zone
inant vegetation types.
encompasses 5,047 km2 (1,917 mi2) and consists of lodgepole
pine (Pinus contorta ssp. murrayana), mountain hemlock (Tsuga
mertensiana) forests and limber pine (Pinus ﬂexilis), foxtail EASTS I DE FOR E ST AN D WO ODLAN D
pine (Pinus balfouriana ssp. balfouriana), and whitebark pine
On the eastern side of the Sierra Nevada, forest and wood-
(Pinus albicaulis) woodlands, with numerous large meadow
lands cover a total of 3,907 km2 (1,484 mi2). The woodlands
are comprised of single-leaf pinyon pine (Pinus monophylla),
while the forests consist of Jeffrey pine, white ﬁr, and mixed
ALP I N E M EAD OW AN D S H R U B LAN D
white ﬁr and pine. The zone ranges in elevation from 1,050
Sitting astride the crest of the Sierra Nevada is the 4,423-km2 m to 2,850 m (3,500–9,500 ft) and is most prevalent between
(1680-mi2) alpine meadow and shrubland ecological zone. The 1500 m and 1,650 m (5,000–5,500 ft).
S I E R R A N E VA D A B I O R E G I O N 269
Overview of Historic Fire Occurrence Fire scar records from ﬁve giant sequoia (Sequoiadendron
giganteum) groves located from Yosemite to south of Sequoia
Fire has been an ecological force in the Sierra Nevada since
National Park conﬁrm the presence of ﬁre in the Sierra
the retreat of the Tioga glacier more than 10,000 years ago.
Nevada for the past 3,000 years with the earliest recorded ﬁre
Flammable fuels, abundant ignition sources, and hot, dry
occurring in 1125 B.C. (Swetnam 1993). Based on independ-
summers combine to produce conditions conducive to an
ent climate reconstructions, years with low precipitation
active ﬁre role. Whereas this role has varied over the millen-
amounts were likely to have ﬁres occur synchronously across
nia as climate has changed, ﬁre continues to shape vegetation
the region. The scars showed that extensive ﬁres burned
and other ecosystem components. Fire’s role is also inﬂu-
every 3.4 to 7.7 years during the cool period between A.D.
enced by the elevation gradient of the Sierra Nevada, which
500 and A.D. 800 and every 2.2 years to 3.7 years during the
affects fuels, ignition sources, and climate.
warm period from A.D. 1000 to A.D.1300. After 1300, ﬁre-
return intervals increased, except for short periods, during
the 1600s for one grove and during the 1700s for two other
groves (Swetnam 1993). Fire-free intervals ranged from 15 to
30 years during the long-interval period and were always less
The earliest evidence of the presence of ﬁre in the Sierra
than 13 years during the short-interval years.
Nevada can be seen in lake sediments more than 16,000
Although lightning would have been present for millennia
years old in Yosemite National Park (Smith and Anderson
prior to charcoal appearing in late sediments 16,000 years
1992). Charcoal does not appear in meadow sediments until
ago, ignitions by Native Americans probably did not occur
about 10,000 B.P. (Anderson and Smith 1997). Six separate
until 9,000 years ago (Hull and Moratto 1999). Their use of ﬁre
peaks in charcoal deposits were recorded between 8,700 and
was extensive and had speciﬁc cultural purposes (Anderson
800 years B.P. in seven meadows from Yosemite south to
1999). It is currently not possible to determine whether char-
Sequoia National Park. Such increases in charcoal abundance
coal deposits or ﬁre scars were caused by lightning ﬁres or by
above the background level indicate large individual ﬁres or
ﬁres ignited by Native Americans. However, Anderson and
ﬁre periods. With the exception of the peak between 8,700
Carpenter (1991) attributed a decline in pine pollen and an
and 9,500 years B.P., charcoal was less prevalent in the early
increase in oak pollen coupled with an increase in charcoal
Holocene Epoch than in the late Holocene, suggesting that
in sediments in Yosemite Valley to expanding populations of
the climate was drier during the earlier period (Anderson and
aboriginal inhabitants 650 years ago. Similarly, Anderson
and Smith (1997) could not rule out burning by aboriginals
Pollen and macrofossils in the sediments indicate that the
as the cause of the change in ﬁre regimes beginning 4,500
forests were more open during the early Holocene, possibly
years ago. It is reasonable to assume that the contribution of
producing less fuel and less extensive ﬁres. Anderson and
ignitions by Native Americans was signiﬁcant but varied over
Smith (1997) hypothesized that, during the late Holocene,
the spectrum of inhabited landscapes (Vale 2002).
climatic changes and possible increases in winter storms or
El Niño-like conditions led to denser forests with greater fuel
loads and more intense ﬁres. Pollen data from sediment cores
taken from subalpine lakes conﬁrmed the meadow data
The arrival of European Americans in the Sierra Nevada
showing open, dry vegetation consisting of pines and chap-
affected ﬁre regimes in several ways. Native Americans were
arral during the early Holocene and closed, wet forests of ﬁrs
often driven from their homeland, and diseases brought from
and hemlocks during the late Holocene (Anderson 1990).
Europe decimated their populations. As a result, use of ﬁre by
Fire scars are another source of information for docu-
Native Americans was greatly reduced. Settlers further exac-
menting the historical role of ﬁre. Wagener (1961b) reex-
erbated the situation by introducing cattle and sheep to the
amined ﬁre scar records from mixed conifer stands on the
Sierra Nevada, setting ﬁres in attempts to improve the range,
western slope of the Sierra Nevada between the Feather River
and excluding ﬁres from other areas to protect timber and
on the north and the San Joaquin River on the south.
watershed values. Extensive ﬁres occurred as a result of slash
Included in his analysis were ﬁve stands originally investi-
burning associated with logging activities and prospectors
gated by Boyce (1920) and two additional stands north and
who burned large areas to enhance the discovery of mineral
south of Yosemite. Based on all seven of those stands, ﬁre-
outcrops (Lieberg 1902).
return intervals ranged from seven to nine years. In a study
Evidence of the changed ﬁre regimes is found in charcoal
area 50 km (31 mi) west of Lake Tahoe, Stephens et al. (2004)
deposits and ﬁre scars. The meadow sediments examined by
recorded ﬁres between 1649 and 1921 with median ﬁre inter-
Anderson and Smith (1997) showed a drop in charcoal parti-
vals between 5 and 15 years. For the mountains just to the
cles during the most recent century, which they attributed to
southeast of Lake Tahoe, Taylor (2004) reported a mean pre-
ﬁre suppression. Giant sequoias also showed a reduction in
settlement ﬁre return interval of 10.4 years. Further south in
ﬁre scars after 1850, assumed by Swetnam (1993) to be the
Kings Canyon National Park, Kilgore and Taylor (1979) found
result of sheep grazing, elimination of ﬁres set by Native
that ﬁres scarred trees every 7 years on west-facing slopes and
Americans, and ﬁre suppression. Similar decreases in ﬁre scars
every 16 years on east-facing slopes.
270 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
Foothill Shrubland and Woodland
were noted by Wagener (1961b) throughout the Sierra
Nevada and by Kilgore and Taylor (1979) in the southern part
The foothill shrubland and woodland zone is the ﬁrst eco-
of the range.
logical zone above the Central Valley bioregion. It is bounded
Of all the activities affecting ﬁre regimes, the exclusion of
below by the valley grasslands and blue oak woodlands and
ﬁre by organized government suppression forces has had the
above by the montane, conifer-dominated zone. The terrain
greatest effect. Beginning in the late 1890s, the U.S. Army
is moderately steep with deep incised canyons. Sedimentary,
attempted to extinguish all ﬁres within the national parks in
metavolcanic, and granitic rocks form the substrate and soils
the Sierra Nevada (van Wagtendonk 1991b). When the Forest
are thin and well drained. The climate is subhumid with
Service was established in 1905, it developed both a theoreti-
hot, dry summers and cool, moist winters. Lightning is rela-
cal basis for systematic ﬁre protection and considerable expert-
tively infrequent, averaging only 8.25 strikes yr 1 100 km 2
ise to execute that theory on national forests (Show and Kotok
(75.9 strikes yr 1 100 mi 2).
1923). This expertise was expanded to the ﬂedgling National
The vegetation is a mix of large areas of chaparral, live oak
Park Service when it was established in 1916. Fire control
woodland with scattered or patchy foothill or ponderosa
remained the dominant management practice throughout the
pines (Fig. 12.3). These species form dense continuous stands
Sierra Nevada until the late 1960s. Fire exclusion resulted in an
of vegetation and fuels. Chamise (Adenostoma faciculatum),
increase in accumulated surface debris and density of shrubs
manzanita (Arctostaphylos spp.), and California-lilac (Cean-
and understory trees. Although the number of ﬁres and the
othus spp.) dominate the chaparral. Interior live oaks or
total area burned decreased between 1908 and 1968, the pro-
canyon live oaks (Quercus chrysolepis) are extensive on steep
portion of the yearly area burned by the largest ﬁre each year
slopes of large canyons. Tall deciduous shrubs or forests dom-
increased (McKelvey and Busse 1996). Suppression forces were
inate riparian areas with dense vertical layering and a cooler
able to extinguish most ﬁres while they were small but during
extreme weather conditions they were unable to control the
F I R E R E S P ON S E S OF I M P ORTANT S P ECI E S
Many foothill species of the Sierra Nevada have ﬁre responses
Current Period and characteristics that are similar to those of the interior
South Coast zone described in Chapter 15. Some species are
Based on early work by Biswell (1959) and Hartesvelt (1962),
dominant, such as chamise in extensive chaparral areas and
the National Park Service changed its ﬁre policy in 1968 to
stands of interior live oak. Chaparral includes many sprouting
allow the use of prescribed ﬁres deliberately set by managers
species but few that require heat for seed germination. The two
and to allow ﬁres of natural origin to burn under prescribed
live oaks are vigorous sprouters. The most prevalent conifers,
conditions (van Wagtendonk 1991b). The Forest Service fol-
such as ponderosa pine, are ﬁre resistant or have serotinous
lowed suit in 1974, changing from a policy of ﬁre control to
cones, such as gray pine and knobcone pine. There has been
one of ﬁre management (DeBruin 1974). As a result, ﬁre was
less research in Sierra Nevada chaparral than in southern Cal-
reintroduced to the Sierra Nevada landscape through programs
ifornia and the proportion of species with ﬁre-dependent
of prescribed burning and wildland ﬁre use (Kilgore and Briggs
characteristics is unknown. Establishment, survival, and abun-
1972, van Wagtendonk 1986). Giant sequoias recorded the
dance of many species are enhanced by ﬁre. The ﬁre responses
new program with ﬁre scars from two prescribed burns in 1969
for knobcone pine (Pinus attenuata), ponderosa pine, and
and 1971 and a wildﬁre in 1988 (Caprio and Swetman 1995).
chamise are covered in more detail in the North Coast (Chap-
For much of the Sierra Nevada, however, routine ﬁre sup-
ter 8), Northeastern Plateaus (Chapter 11), and South Coast
pression is still the rule. Fire regimes are altered with a shift
(Chapter 15) chapters, respectively. Table 12.4 lists the ﬁre
from frequent, low-intensity ﬁres to less frequent, large ﬁres
responses of the important species in the foothill zone.
(McKelvey and Busse 1996). Fuel accumulations, brush, small
Numerous chaparral shrubs sprout following ﬁre. These
trees, and dense forests produce very different conditions for
include chamise, ﬂannelbush (Fremontodendron californicum),
the inevitable ﬁre that occurs, whether from lightning or
poison oak (Toxicodendron diversilobum), coyote brush (Baccha-
from human sources. Some headway is being made in wilder-
ris pilularis), birch-leaf mountain-mahogany (Cercocarpus betu-
ness areas and areas where prescribed ﬁre can be applied
loides var. betuloides), redshank (Adenostoma sparsifolium), yerba
safely and effectively.
santa (Eriodictyon californicum), California coffeeberry (Rhamnus
californica), and Christmas berry (Heteromeles arbutifolia)
(Biswell 1974). Non-sprouting shrubs can be dominant as well,
Major Ecological Zones
with seeds that are heat resistant and have ﬁre-enhanced ger-
mination—such as whiteleaf manzanita (Arctostphylos viscida),
The six ecological zones of the Sierra Nevada are comprised
Mariposa manzanita (Arctostaphylos viscida spp. mariposa),
of different vegetation types and species. Each species has dif-
chapparal whitethrorn (Ceanothus leucodermis), and buck brush
ferent adaptations to ﬁre and varies in its dependency on ﬁre.
(Ceanothus cuneatus var. cuneatus). Exposure to heat can more
Similarly, the ﬁre regimes and plant community interactions
than double germination rates. Laurel sumac (Malosma laurina)
of the zones vary.
S I E R R A N E VA D A B I O R E G I O N 271
F I G U R E 12.3. Foothill shrub and
woodland. Foothill pine and interior
live oak are dominant overstory
species in this stand with non-native
grasses and species of manzanita and
California-lilac in the understory. Fire
is common and keeps the understory
seedlings that survive well on mineral soil. Pitch running
seed germination increased from 17% to more than 50% with
down the bole is common and increases crown torching
exposure to 100°C (212°F) (Wright 1931). Many chaparral
(Lawrence 1966). The tolerance of foothill pine for rocky,
species produce seed at an early age that can remain viable in
thin soils and drought conditions also enables it to avoid
the soil for decades or more. Buck brush produces seeds from
burning because fuels are scattered and ﬁre infrequent.
age 5 to 7 years. Growing in dominantly single-species patches,
Because foothill pine seeds are large and wingless, dispersal
buck brush resists burning until decadent or foliar moistures are
of seeds is dependent on seed caching by rodents and birds.
extremely low. Several crops of seed are often produced before
Native Americans maintained small patches of native grass-
ﬁre returns, enhancing post-ﬁre dominance.
lands such as deergrass (Muhlenbergia rigens), which is a large,
Sierra Nevada chaparral can be more productive than its
coarse-leaved perennial bunchgrass (Anderson 1996). It responds
southern California counterparts, with four times the bio-
to periodic burning with vigorous growth. Fires, particularly if
mass accumulation over 37 years (Rundel and Parsons 1979).
set in the fall, favored native species, including ﬁre-stimulated
As stands age, the proportion of dead biomass increases. By
ﬂowers of bulb-species like brodiaea (Brodiaea spp.) (York 1997).
the time chamise stands reach 16 years of age, the combination
of dead branches and live resinous foliage make them Fire exclusion has led to invasion of these patches by annual,
extremely ﬂammable. non-native grasses such as cheat grass (Bromus tectorum).
Numerous geophytes, or bulb-bearing plants, that show an
increased ﬂowering and growth response following ﬁre are
F I R E R E G I M E–P LANT C OM M U N IT Y I NTE RACTION S
scattered in chaparral. Common examples are soap plant
(Chlorogalum pomeridianum), death camas (Zigadenus spp.), Fire regimes in the foothill zone vary with topography and
and mariposa lilies (Calochortus spp.). Annual plants respond vegetation. In the lower portions with more gentle topogra-
to ﬁre by proliﬁc seeding. phy, the oak grassland savannah areas burned frequently and
Interior and canyon live oaks sprout both from root and with low to moderate intensity as described in the Central
canopy crowns following ﬁre and their seedlings develop Valley chapter (Chapter 11). Fire season would have begun in
burls early. Canyon live oak bark resists low-intensity ﬁres early summer extending to fall. Steeper areas dominated by
(Paysen and Narog 1993), whereas the relatively thin bark of chaparral and scattered trees or pockets of conifers burned less
interior live oak results in top-kill with all but lowest-inten- frequently and with higher-intensity crown ﬁres, resulting in
sity ﬁres (Plumb 1980). Both species can also sprout new highly severe effects to vegetation (Table 12.5). These are
branches from epicormic buds on the stem. among the driest areas in the bioregion, with less than 62.5
Foothill pines persist after high-intensity ﬁres in sur- cm (25 in) average annual precipitation being characteristic.
rounding chaparral by developing cones and seeds at an Fire season is long and begins in early summer. Given the high
early age, producing plentiful seeds (Fowells 1979), and by numbers of species with ﬁre-enhanced responses, the vegeta-
having cones that are opened by heat (Sudworth 1908) and tion overall is resilient to high-severity ﬁres. Where severe ﬁres
272 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
TA B L E 12.4
Fire response types for important species in the foothill shrub and woodland ecological zone
Type of Fire Response
Lifeform Sprouting Seeding Individual Species
Conifer None None Resistant, killed Ponderosa pine
None Fire stimulated Resistant, killed Foothill pine, knobcone pine
Hardwood Fire stimulated None Top-killed or Blue oak, interior live oak,
branch killed canyon live oak
Shrub Fire stimulated None or Top-killed Poison oak, ﬂannelbush,
unknown coyote bush, birch-leaf
redshank, yerba santa,
Fire stimulated Fire stimulated Top-killed Chamise, redbud
None Fire stimulated Killed Whiteleaf manzanita, chaparral
whitethorn, buck brush
None None Killed
Forb Fire stimulated None Top-killed Soap plant, death camas,
Grass Fire stimulated None Top-killed Deergrass
None None Killed Cheat grass
have occurred at the upper end of the foothill shrubland Frequent ﬁre in the grasslands of the foothills, in part from
zone, the boundary between the shrublands and the lower- burning by Native Americans, reduced encroachment by chap-
montane forest has shifted. Reestablishment of the conifers in arral. With ﬁre suppression and elimination burning by Native
those areas could take decades to centuries, and frequent Americans, chaparral has increased in extent. Chaparral has
recurring ﬁres may perpetuate the shrub species. also increased on sites where it previously co-occurred with
Little direct information exists on the patterns of historic ponderosa pine. Ponderosa pine remains in the foothills in
vegetation shaped by ﬁre. Biswell (1974) described three dif- limited patches on more mesic north-facing slopes. It has a
ferent kinds of California chaparral, of which two occur in reduced distribution due to preferential logging during Euro-
the Sierra Nevada foothills. One is on shallow soils and steep pean settlement. Natural re-establishment of ponderosa pine
slopes with chamise, California-lilac, manzanita, and scrub in the foothills is limited by the reduction in ﬁres, which pro-
oaks; and the second is on deeper productive soils, often vided canopy openings and mineral soil for successful survival.
developed from grasslands when ﬁres become less frequent. In some locations, the boundary for conifer communities is ris-
Other species occur such as ﬂannelbush and coyote brush. ing in elevation due, in part, to current patterns of ﬁre. In the
This type of chaparral has increased with ﬁre suppression and foothills to the west of Yosemite National Park, recurrent,
development in the foothills. large, high-intensity ﬁres have resulted in establishment of
Recurrent ﬁre and dominance by sprouters tend to per- vast shrub ﬁelds and annual grasslands. Ponderosa pine is at
petuate large patches of single-species dominated chaparral its lower limit in the foothills as moisture becomes less avail-
or oak forest. Chamise dominates large areas, particularly on able, especially in large open areas. Establishment of pon-
dry, shallow soil sites with both post-ﬁre sprouting and heat- derosa pine is difﬁcult since seed sources are somewhat distant.
enhanced germination. But not all chamise plants resprout, Foothill pine stands respond to the ﬁre regimes of the sur-
and these openings allow California-lilac to germinate and rounding chaparral and live oak stands, surviving those of
persist in mixed chamise patches. Similarly, live oak often low severity and succumbing to moderate- to high-severity
dominates large areas and sprouts vigorously with rapid ﬁres. Partial serotiny allows reestablishment after stand-replac-
growth following ﬁre (Biswell 1974). ing ﬁres. Woody and duff fuel loads are among the lowest of
S I E R R A N E VA D A B I O R E G I O N 273
TA B L E 12.5
Fire regime attributes for vegetation types of the foothill shrub and
woodland ecological zone
Chaparral Oak woodlands/ Conifer forest
Seasonality Summer–fall Summer–fall Summer–fall
Fire-return interval Medium Short Medium
Size Large Large Small
Complexity Low Low Low
Intensity High Low High
Severity High Low High
Fire type Crown Surface Crown
Fire regime terms used in this table are deﬁned in Chapter 4.
any Sierra Nevada conifer and do not contribute signiﬁcantly a stand of ponderosa pines, incense-cedars, and sugar pines
to ﬁre spread and intensity (van Wagtendonk et al. 1998). with an understory of mountain misery (Chamaebatia foli-
Although relatively uncommon, patches of knobcone pine olosa). Giant sequoia–mixed conifer forests are concentrated
exist in the Sierra Nevada foothills surrounded by chaparral. in several river basins in the central and southern Sierra
Locations are typically steep on large canyon walls. These Nevada, occupying sites where soils are wet. At the highest
patches are dependent on high-intensity ﬁre because of their elevation, at the boundary with upper montane forests, white
serotinous cones. Current practices of ﬁre exclusion may ﬁr often becomes dominant on all aspects except where soils
reduce the persistence of some knobcone pine patches. are shallow or very rocky. Here, pine or shrub communities
Throughout the zone, riparian plant communities char-
acterized by deciduous trees, shrubs, large herbs, and grasses
The lower-montane forest ecological zone is the ﬁrst con- occur with varied proportions of intermixed conifers. White
tinuous zone of conifers as one ascends the Sierra Nevada. alder (Alnus rhombifolia), gray alder (Alnus incana), or black
The foothills are below with the upper montane forest cottonwood (Populus balsamifera ssp. trichocarpa) dominate
above. The relatively gentle western slope consists of ridges larger streams or wetter sites. Bigleaf maple (Acer macrophyllum)
and river canyons. Metavolcanic, metasedimentary, and and mountain dogwood (Cornus nuttallii) occur along
granitic rocks form the majority of the geologic substrates smaller or intermittent streams. Small patches of quaking
and soils are relatively deep and well drained. Summers are aspen occur in the higher-elevation white-ﬁr–dominated
hot and dry, and winters are cold and wet. Lightning is forests but are more prevalent in the upper-montane zone.
moderately frequent, averaging 15.6 strikes yr 1 100 km 2 Meadows and seeps tend to be small and scattered.
(40.3 strikes yr 1 100 mi 2). Partly due to increasing precipitation, Douglas-ﬁr becomes
Vegetation and ﬁre within the lower-montane zone vary important from the Mokelumne River basin to the north.
with elevation, landscape position, and latitude. At the low- Mixed-evergreen forests comprised of tanoak (Lithocarpus den-
est elevations, California black oak and ponderosa pine dom- siﬂorus), Paciﬁc madrone (Arbutus menziesii), and other mon-
inate large areas, particularly in the southern Sierra Nevada. tane hardwoods and conifers occupy large areas in the western
Intermixed with the oak-pine forests are various-sized patches Yuba and Feather River basins further north where precipita-
of chaparral and canyon live oak—extensions of foothill tion exceeds 152 cm (60 in) annually.
types. Manzanita and California-lilac species dominate chap-
arral, whereas canyon live oak is extensive on steep slopes of
F I R E R E S P ON S E S OF I M P ORTANT S P ECI E S
large canyons. With increasing elevation, the proportion of
white ﬁr or Douglas-ﬁr increases on mesic slopes they can The majority of lower-montane species have characteristics
dominate. Incense-cedar (Calocedrus decurrens) and sugar pine resulting in resistance to ﬁre and often have favorable
(Pinus lambertiana) are found throughout. Figure 12.4 shows responses to ﬁre. Sprouting hardwood trees, shrubs, vines,
274 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
F I G U R E 12.4. Lower-montane forest. This open stand of ponderosa pine, incense-cedar, and sugar pine with mountain misery in the under-
story burned in 1978 and in 1996.
herbs, and grasses are common and mostly ﬁre enhanced; more information about responses of this species to ﬁre.
conifers have at least some ﬁre-resistant characteristics. Paciﬁc yew (Taxus brevifolia) and California nutmeg (Torreya
Giant sequoia, ponderosa pine, sugar pine, Douglas-ﬁr, californica) are uncommon, relict conifers that have thin
and white ﬁr have thick bark when mature (Table 12.6). The bark. They have survived in the ﬁre-prone landscape by
trees vary in their level of resistance to low- and moderate- their restricted habitats in wet, mostly riparian areas and
intensity ﬁres. Ponderosa pine has a thicker bark as a seedling can apparently survive low-intensity ﬁre as evidenced by
and is more resistant to ﬁre than the other lower-montane observed ﬁre scars and sprouting (Fites-Kaufman 1997).
conifers. As ponderosa pine grows older, its high crowns and The montane hardwoods, including tanoak, Pacific
large, protected buds provide additional ﬁre resistance. Rapid madrone, California black oak, canyon live oak, California
growth of giant sequoia seedlings produces early ﬁre resist- bay (Umbellularia californica), mountain dogwood, bigleaf
ance. Douglas-ﬁr, white ﬁr, and incense-cedar have thick maple, white alder, and black cottonwood, all sprout from
bark when mature, but are killed by ﬁre when young because basal burls or root crowns following ﬁre. Sprouting can be
of thin bark, low, ﬂammable crowns, and small, unprotected vigorous with up to 100 sprouts produced on individual
buds. Sugar pine is intermediate in ﬁre resistance with thick California black oak stumps (McDonald 1981). Sprouting
bark and high crowns but potentially more susceptible to can also can change with tree size. Tanoak sprouts are
cambial or root damage from heat (Haase and Sackett 1998). smaller when originating from smaller trees (Tappenier et al.
All conifers show improved establishment with mineral 1984). Epicormic sprouting from the stem following low-
soil. Giant sequoias have serotinous cones that are exposed intensity ﬁre was observed in California black oak, tan oak,
by heat or by small mammals and show increased seedling and mountain dogwood (Kauffman and Martin 1990). Cal-
density with higher-intensity ﬁre (Kilgore and Biswell 1971). ifornia black oak is the only species that develops bark suf-
Giant sequoia is the only Sierra Nevada conifer that sprouts, ﬁciently thick to resist low- to moderate-intensity ﬁre in
but this response is apparently limited to younger trees larger trees ( 16 cm [6.3 in] dbh) (Plumb 1980). Riparian
(Weatherspoon 1986). See sidebar on giant sequoias for hardwoods all sprout following fire. Native Americans
S I E R R A N E VA D A B I O R E G I O N 275
TA B L E 12.6
Fire response types for important species in the lower montane ecological zone
Type of Fire Response
Lifeform Sprouting Seeding Individual Species
Conifer None None Resistant, killed Ponderosa pine, Douglas-ﬁr, white
ﬁr, sugar pine, incense-cedar
None Fire stimulated Resistant, killed Giant sequoia
(seed release) except sprouts
None None Low resistance, Paciﬁc yew
Hardwood Fire stimulated None Top-killed Black oak, tan oak, canyon
live oak, big-leaf maple,
Paciﬁc madrone, white alder
Shrub Fire stimulated None Top-killed Mountain misery, greenleaf
manzanita, poison oak,
Fire stimulated Fire Stimulated Top-killed Deer brush, Scotch broom
None Fire stimulated Killed Whiteleaf manzanita
Forb Fire stimulated None Top-killed Penstemon, many lilies,
iris, Paciﬁc starﬂower, trail plant,
sanicle, mountain lady’s slipper
Grass None None
Fire stimulated None Top-killed Red fescue, melic, sedges
None None Killed Cheat grass
burned riparian areas to enhance shoot production of bigleaf protected from heat more than 20 cm (8 in) below the soil sur-
maple and hazelnut (Coylus cornuta) shrubs (Anderson 1999). face. With highly ﬂammable foliage containing volatile oils
Many shrubs have ﬁre-enhanced regeneration with both and with highly dissected leaves, mountain misery promotes
sprouting and heat-stimulated seeds (Kauffman and Martin burning. Rundel et al. (1981) found that regrowth was stimu-
1990) (Table 12.6). Sprouters include mountain misery, deer lated by spring and fall burns but that summer burns inhibited
brush (Ceanothus intergerrimus), greenleaf manzanita (Arc- resprouting for at least two years. Further enhancing its com-
tostaphylos patula), bush chinquapin (Chrysolepis sempervirens), petitive advantage, mountain misery is able to ﬁx nitrogen
mountain whitethorn (Ceanothus cordulatus), and riparian from nodules that develop after burning (Heisey et al.1980).
shrubs hazelnut, thimbleberry (Rubus parviﬂorus), and gray alder. Some shrubs, particularly California-lilac, have heat-stim-
The burning season can affect sprouting response. Bush chin- ulated seed germination. Heat-stimulated seed of deer brush
quapin, Sierra gooseberry (Ribes roezlii), deer brush, greenleaf can produce extensive seedling patches, as dense as 15,800
seedlings ha 1 (6,500 seedlings ac 1) after burning (Kilgore
manzanita, and thimbleberry all showed greater sprouting fol-
lowing early spring burns than fall or late spring burns (Kauff- and Biswell 1971). Mountain whitethorn also produces
man and Martin 1990). But mountain whitethorn showed the many seeds that can persist in the soil for decades or cen-
greatest post-ﬁre sprouting after higher-intensity fall burns. turies. The dual ﬁre-enhanced sprouting and seed germina-
Sprouting occurs from burls, root crowns, and rhizomes. tion responses of the native deer brush and non-native
Shrubs sprouting from deeply buried rhizomes, such as Scotch broom (Cytisus scoparius) make them particularly suc-
mountain misery, can readily dominate sites with frequent cessful in rapidly colonizing burned sites. Scotch broom is an
and intense ﬁre. Mountain misery occupies extensive areas, 4 aggressive, non-native shrub that has animal-dispersed and
to 40 ha (10–100 ac), through extensive networks of rhizomes fire-stimulated seed, vigorous sprouting, and rapid early
276 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
S I DE BAR 12.1. G IANT S E Q U O IAS AN D F I R E
One is in no danger of being hemmed in by sequoia ﬁres, because they never run fast, the speeding
winds ﬂowing only across the treetops, leaving the deeps below calm, like the bottom of the sea. Fur-
thermore, there is no generally distributed ﬁre food in sequoia forests on which ﬁres can move rap-
idly. Fire can only creep on the dead leaves and burrs, because they are solidly packed.
—JOHN MUIR, 1878
Probably better than any other species, giant sequoia exempliﬁes a truly ﬁre-adapted species. Not only
does it have thick bark that protects it from periodic surface ﬁres, but also its cones are opened by heat
and its regeneration is dependent on exposed mineral soil, such as occurs after a moderately severe
ﬁre. Biswell (1961) was one of the ﬁrst scientists to explore the relationships between giant sequoias
and ﬁre. He reported ﬁre scar dates in the Mariposa Grove in Yosemite National Park from as early as
A.D. 450 with periods between ﬁre scars averaging 18 years. He also looked at the number of light-
(36-mi 2) areas surrounding sequoia groves and found that during the years from
ning ﬁres in 93-km
1950 through 1959, 36 ﬁres had been suppressed in the Mariposa Grove and 39 in the Tuolumne
Grove. These data along with observations of dense thickets of white ﬁrs and incense-cedars and large
increases in forest ﬂoor debris led him to conclude the groves should be managed with ﬁre as part of
Hartesveldt (1962) conducted the ﬁrst detailed scientiﬁc study of giant sequoias and ﬁre in the Mariposa
Grove and concluded that the greatest threat to the survival of the big trees was catastrophic ﬁre burn-
ing through accumulated surface and understory fuels as a result of decades of ﬁre exclusion. His rec-
ommendation was to reintroduce ﬁre to the giant sequoia ecosystem through the use of prescribed
burning (Hartesveldt 1964).
Subsequently, Hartesveldt and Harvey (1967) and Harvey et al. (1980) studied factors associated with
giant sequoia reproduction in the Redwood Mountain Grove of Kings Canyon National Park. Using exper-
imental ﬁres and mechanical manipulations, they measured seedling survival and growth and investi-
gated the role of vertebrate animals and arthropods in giant sequoia reproduction. Seedlings established
on the hottest areas burned survived at a higher rate than those on other soils. Fire did not greatly affect
vertebrate populations, and only one species had a signiﬁcant effect on sequoia reproduction. The Dou-
glas squirrel feeds on the scales of two- to ﬁve-year-old giant sequoia cones and cuts and caches thou-
sands of cones each year. This greatly aids the distribution of cones and, subsequently, seedlings because
the squirrels could not relocate most cached cones. Although more than 150 arthropods were found to
be associated with giant sequoias, only two signiﬁcantly affected regeneration. The gelechiid moth
(Gelechia spp.) feeds on one-year-old cones, while the small long-horned beetle mines the main axis of
cones older than ﬁve years, which causes them to dry and drop their seeds.
Based on these ﬁndings, the national Park Service began a program of prescribed burning and research
in giant sequoia groves in Yosemite, Sequoia, and Kings Canyon National Parks (Kilgore 1972). Detailed
information on ﬁres and minerals (St. John and Rundel 1976), fuel accumulation (Parsons 1978), and ﬁre
history (Kilgore and Taylor 1979) added to the knowledge about the role of ﬁre in these forests.
Burning in sequoia groves was not without controversy, however. Charred bark from a prescribed burn
in Sequoia National Park prompted an investigation and a report on the burning programs in the groves
(Cotton and McBride 1987). As a result, additional research was conducted to reﬁne the scientiﬁc basis
for the programs (Parsons 1994). Fire history studies extended the ﬁre scar record back to 1125 B.C., with
an average interval between ﬁres from 2 to 30 years (Swetnam 1993). Pollen and charcoal in sediments
cores taken in the groves indicated that giant sequoias became more prevalent about 5,000 years ago and
that ﬁres occurred throughout the record (Anderson 1994, Anderson and Smith 1997).
Studies on the effects of ﬁre on fungi and insect relationships with giant sequoias led Piirto (1994) to
conclude that ﬁre does inﬂuence the types and population levels of numerous organisms but that their
interactions are not well understood. Other studies looked at the role of ﬁre severity in establishing and
maintaining giant sequoia groves. Of particular interest was the ﬁnding that patchy, intense ﬁres existed
in presettlement times and that these ﬁres were important determinants of grove structure and compo-
sition (Stephenson et al. 1991). Leading to these intense ﬁres in giant sequoia groves are the heaviest
woody fuel loads found for any Sierra Nevada conifer species (van Wagtendonk et al. 1998).
All the research to date indicates that ﬁres have always played an important role in giant sequoia ecol-
ogy and that the survival of the species depends on the continued presence of ﬁre. Management programs
must recognize this fact and must be designed to include ﬁre in as natural a role as practicable. Restora-
tion targets must include process goals as well as structural goals based on sound science (Stephenson
1999). Only through such a program can we ensure the survival of this magniﬁcent ﬁre species.
F I R E R E G I M E–P LANT C OM M U N IT Y I NTE RACTION S
growth and seed production. It is taller than mountain mis-
ery and can out-compete deer brush and even mountain
misery at times. Fire regime attributes for major vegetation types of the lower
Deer brush is one of the most ubiquitous shrubs throughout montane ecological zone are shown in Table 12.7. Fire was
the lower montane zone. Germination with wet seed can be generally frequent in the lower-montane zone, ranging from
greater than from dry heat (Kauffman and Martin 1990). This 2 to 20 years on average at the stand or landscape scale
could explain its greater prevalence, especially after ﬁres on (Wagener 1961b, Skinner and Chang 1996). There was
moister portions of the landscape, such as north and east aspects noticeable variation in ﬁre pattern with latitude and eleva-
or lower slopes. It gains height rapidly but can be limited by deer tion related to shifts in ﬁre season and in precipitation. Drier
browsing (Kilgore and Biswell 1971). It persists under shaded areas with longer ﬁre seasons experienced the most frequent
canopies, but in a decadent, highly ﬂammable state. and regular ﬁres. These areas are most prevalent in the south-
Little formal research has been conducted on fire ern and central Sierra Nevada and throughout the range on
response of herbs and grasses in the Sierra Nevada. But south aspects, ridges, and lower elevations. These areas tend
observations of morphology and fire responses indicate to be dominated or co-dominated by ponderosa pine and
many understory species are enhanced by ﬁre. Numerous California black oak. Throughout the zone, relatively cooler
perennial plants with sprouting structures including rhi- and wetter sites have had frequent but less regular ﬁre and are
zomes, corymbs, or stolons exist and have been observed more likely to have a presence or dominance of Douglas-ﬁr
sprouting following ﬁre. These include Paciﬁc starﬂower and white ﬁr. Fire patterns and vegetation interactions also
(Trientalis latifolia), trail plant (Adenocaulon bicolor), western varied at ﬁne-spatial scales for all portions of this zone.
blue ﬂag (Iris missouriensis), Bolander’s bedstraw (Galium The interrelationships between vegetation and fire
bolanderi), bear-grass (Xerophyllum tenax), sanicles (Sanicula regimes make it difﬁcult to distinguish which pattern drives
spp.), many-stemmed sedge (Carex multicaulis), Ross’ sedge the other. Fire-return interval estimates for this zone vary by
(Carex rossii), needlegrasses (Achnantherum spp.), oniongrass the size of area examined. Average fire-return intervals
(Melica bulbosa), and red fescue (Festuca rubra). On the other reported for larger sample areas (more than 50 ha [122 ac])
hand, some species like the Mountain lady’s slipper (Cypri- generally fall under 10 years and are often as short as 4 years
pedium montanum) are killed outright by ﬁre. Other plants (Caprio and Swetnam 1995). Fire-return intervals for smaller
exhibit sprouting or enhanced flowering following fire. areas (fewer than several ha) are more variable, ranging
Mariposa lilies and penstemons (Penstemon spp.) are two from 5 to more than 30 years (Kilgore and Taylor 1979,
examples. Fites-Kaufman 1997).
278 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
TA B L E 12.7
Fire regime attributes for major vegetation types of the lower montane ecological zone
Ponderosa pine/ Douglas-ﬁr/ Tanoak-mixed
black oak white ﬁr evergreen
Seasonality Summer–fall Summer–fall Summer-fall
Fire-return interval Short (regular) Short (variable) Medium (variable)
Size Large Large Medium
Complexity Low Multiple Multiple
Intensity Low Low–moderate Multiple
Severity Low–moderate Low–moderate Multiple
Fire type Surface Surface–multiple Multiple
Fire regime terms used in this table are deﬁned in Chapter 4.
F I G U R E 12.5. Distribution of ﬁre-
return intervals from small sample
areas (1–3 ha, 2.5–7.5 ac) showing
variation between moist and dry sites.
Return intervals for dry sites peak at
50 years, whereas moist sites can have
intervals of more than 100 years.
(Adapted from Fites Kaufman 1996.)
North–south gradients in climate and vegetation parallel composition. The distribution of return intervals for xeric
changes in ﬁre patterns. Fire seasons are longer and precipi- sites is more skewed toward small return intervals than for
tation lower in the southern portions of the westside lower mesic sites. The more frequent, regular ﬁre pattern is more
montane zone. In ponderosa pine–California black oak often associated with ponderosa pine-dominated sites. Pon-
forests of the southern Sierra Nevada, ﬁre-return intervals derosa pine develops resistance to ﬁre at a young age and can
increased with increasing elevation (Caprio and Swetnam best tolerate frequent, regular ﬁre. The less regular ﬁre pattern
1995). In the northern Sierra Nevada, mean ﬁre-return inter- is more often associated with the presence of Douglas-ﬁr or
vals were shorter (5–15 years) on drier, south- and west-fac- white ﬁr. These latter species require more time for young
ing upper slopes than on mesic, north- and east-facing lower trees to develop ﬁre resistance. Spatial complexity of vegeta-
slopes (15–25 years) (Fites-Kaufman 1997). More important tion within forest stands has been linked to ﬁre (Bonnickson
than the average ﬁre-return intervals, the distribution of ﬁre- and Stone 1982, Fites-Kaufman 1997, Knight 1997).
return intervals can vary substantially among locations in the Diverse and variable species in both the tree and shrub lay-
landscape (Fig. 12.5), with associated differences in forest ers resulted in variable fuel and ﬁre patterns. For example,
S I E R R A N E VA D A B I O R E G I O N 279
drought cycles, which would create larger areas of highly
ponderosa pine fuels are more loosely packed than those of
ﬂammable vegetation. It is also possible that locations in the
white ﬁr, allowing the pine fuels to burn more readily (van
northern Sierra Nevada with high average annual rainfall
Wagtendonk et al. 1998). High levels of contrasting ﬁre envi-
(more than 203 cm [80 in] mean annual precipitation) and
ronments, such as varying slope, aspect, elevation, and
continuous fuels (conifer and tan oak) would have a higher
weather, as well as topographically controlled diurnal changes
proportion of high-severity ﬁres (Fites-Kaufman 1997).
in ﬁre behavior, overlap with variable fuel patterns to create
Moister conditions and higher foliar water content reduce
ﬁne-scale patterns of variation in forest density, height, tree
ﬁre in many years but allow more fuels to accumulate. These
sizes, and understory vegetation. With fire suppression,
locations also overlap with steep terrain. When the canyons
density and uniformity in structure and composition have
are aligned with prevailing southwest winds, the likelihood
increased. Across many sites in the mid-elevations of the
of larger, severe ﬁre increases.
central and southern Sierra Nevada, white ﬁr and incense
Currently, most of the area burned does so with ﬁres of
cedar have increased, shifting composition away from pon-
high intensity and severity. The Sierra Nevada contains some
derosa pine and creating more uniformly dense forests
of the most productive ﬁre-prone areas in the western United
(Vankat and Major 1978, Parsons and deBenedetti 1979, Min-
States (Franklin and Agee 2003). The increased stand densi-
nich et al.1995, Bouldin 2000). Douglas-ﬁr responds similarly
ties and reduced decomposition rates result in accumulated
in the northern Sierra Nevada (Fites-Kaufman 1997). At lower
fuels (Kilgore 1973, Vankat and Major 1978, Agee et al. 2000).
elevations, bordering the foothills, these shade-tolerant
This increases the tendency for high-intensity and high-
species are scarce or absent but ponderosa pine has increased
severity ﬁre through both increased fuels and increased sus-
in density (Parsons and deBenedetti 1979, Fites-Kaufman
ceptibility of dense smaller vegetation. It is unknown if cur-
1997). Similarly, at higher elevations, white ﬁr dominates but
rent ﬁres are larger but the extent of high-severity ﬁre has
with increased uniformity and density attributed to lack of
certainly increased (Skinner and Chang 1996).
ﬁre (Parsons and deBenedetti 1979).
Most ﬁres occur between mid-summer and early fall. The
Historically, open or more variable forest structure
ﬁre season is longer in the southern portion of the Sierra
occurred as a result of more frequent ﬁre (Gruell 2001). Not
Nevada because of drier conditions. Some ﬁres have always
only did ﬁre favor different species with different return
occurred in the spring and early summer and occasionally in
interval patterns, but also it affected forest structure by
the winter. Historic ﬁre patterns in lower-elevation and drier
thinning the young trees, leaving a patchier or more open
landscapes maintained open pine and California black oak
forest, and selectively retaining larger, ﬁre-resistant trees
woodlands with resprouting shrubs and perennial grasses
(Bonnickson and Stone 1982, van Wagtendonk 1985).
and herbs. Suppression of ﬁre in combination with harvest
Exactly what the landscape was like overall and what pro-
patterns has resulted in an increase in the density of these
portion was low density are unknown. Early observers
forests (Parsons and deBenedetti 1979) but not always in
emphasized open, park-like pine-dominated forests (Muir
changes of pine dominance (Parsons and deBenedetti 1979,
1895, Jepson 1921) but also noted dense patches (Sudworth
Fites-Kaufman 1997). At higher elevations, trees with greater
1900, Leiburg 1902). Gruell (2001) chronicled the ecologi-
shade tolerance and less fire-resistant seedlings such as
cal changes since 1849 through a series of repeat photo-
white ﬁr, Douglas-ﬁr, and incense-cedar, have become estab-
graphs. Portions of the landscape that exhibited more vari-
lished and form dense understories (Parsons and deBenedetti
able fires included north and east aspects and higher
1979, van Wagtendonk 1985, Vale 1987,). Lower light levels
elevations. These areas had greater portions of the land-
and possibly lack of ﬁre have resulted in sparse shrub and
scape with moderate to high cover forests, evidenced by the
herb presence. On more mesic north or east slopes at mid-
historic prevalence of shade-tolerant white ﬁr and Douglas-
elevations, white ﬁr and Douglas-ﬁr were historically present
ﬁr (Fites-Kaufman 1997).
but have also increased in density (Fites-Kaufman 1997). High-
Questions remain concerning the intensity and severity of
elevation white ﬁr–mixed conifer forests have often retained
presettlement ﬁres. All sites in the lower-montane zone expe-
similar composition but increased in density (Parsons and
rienced ﬁre frequently enough to reduce fuel accumulations
and vegetation density, and, as a result, these ﬁres were pri-
Historically, Sierra Nevada lower-montane forests were
marily of low to moderate intensity and severity. Long-term
more heterogeneous with clumps or patches of shrubs pres-
evidence in giant sequoia suggests that high-severity ﬁres
ent in varying amounts. Fire promoted a greater distribution
occurred in small patches (Stephenson et al. 1991). Large
of younger, more vigorous sprouting shrubs. Deer brush is
patches of California black oak or chaparral persist, evidently
able to persist in the forest through changes in density until
the result of large, severe ﬁres. Some patches may have orig-
ﬁre or some other activity opens the overstory and heats the
inated or expanded during the last century of suppression
soil, stimulating germination or sprouting. Current low lev-
(Vankat and Major 1978), but others were apparently from
els of ﬁre have resulted in increasingly tall and decadent
earlier ﬁres (Leiburg 1902).
deer brush, slowly being shaded out under dense forest cover.
There is a lack of historical information on the size or dis-
Thick patches of mountain misery decrease ponderosa
tribution of high-severity ﬁres in the lower-montane zone. It
pine regeneration, precluding dense stands of pines from
is likely that they occurred infrequently and were related to
280 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
F I G U R E 12.6. Upper-montane forest.
This stand is characterized by large
red ﬁr, western white pine, and Jeffrey
pine in the overstory with an under-
story of prostrate and erect manzanita
and California-lilac species. Fire is
infrequent but can burn extensive
developing. This has resulted in the maintenance of relatively shows a stand of California red ﬁr and western white pine
open pine stands over mountain misery, even with ﬁre sup- with a sparse understory of montane chaparral. Other
pression. Fire restoration in these settings has been achieved alliances include western white pine, quaking aspen, western
in only two applications in Yosemite National Park. juniper, Jeffrey pine, and tufted hairgrass (Deschampsia cespi-
tosa ssp. holciformus). Interspersed in the forests are wet mead-
ows and stands of montane chaparral.
The upper-montane forest is located just above the lower-
F I R E R E S P ON S E S OF I M P ORTANT S P ECI E S
montane forest and occurs on both sides of the crest of the
Sierra Nevada. The forest ranges in elevation with latitude. Many upper-montane species have ﬁre-resistant characteris-
On the west side of the crest, elevations are generally lower tics and respond favorably to ﬁre (Table 12.8). Shrubs and
than on the east side, with the differences greater in the hardwood trees typically sprout, whereas herbs and grasses
south than in the north (Potter 1998). The terrain is relatively either reseed or regrow quickly after ﬁre. Conifers are pro-
moderate on the west side but drops precipitously on the tected from the heat from ﬁre by thick bark layers.
east. The geology underlying this zone is primarily volcanic The conifers in the upper-montane ecological zone vary in
in the north and granitic in the south. Soils are weakly devel- their resistance to ﬁre. California red ﬁr has thin bark when
oped and are typically medium to coarse textured and often it is young, making it susceptible to ﬁre. As California red ﬁr
lack a clay zone (Potter 1998). matures, its bark becomes thicker and it is able to survive
The climate of the upper-montane forest is moderate with most ﬁres (Kilgore 1971). Similarly, mature Jeffrey pines have
warm summers and cold winters. Total annual precipitation, thick bark, and a slightly thicker bark when young that
although less than that which occurs in the lower montane allows them to survive low-intensity ﬁres. Western white
forest, is still relatively high with 65% to 90% falling as snow pine and western juniper are more susceptible to ﬁre at a
(Major 1988). Barbour et al. (1991) propose that the ecotone young age than California red ﬁr or Jeffrey pine. The per-
between the lower and upper-montane zones is determined centage of crown scorch that a species can sustain is also vari-
by the winter-long snowpack. The upper-montane forest able. Like ponderosa pine, up to 50% of the buds of a Jeffrey
zone receives as many lightning strikes as might be expected pine can be killed and it can still survive (Wagener 1961a).
by chance (van Wagtendonk 1991a). The average number of The other upper-montane conifers can sustain only 30% to
lightning strikes that occurred in the zone between 1985 40% scorch (Kilgore 1971).
and 2000 was 29.3 strikes yr 1 100 km 2 (75.9 strikes yr 1 100 Quaking aspen is the primary hardwood species in the
mi 2) (van Wagtendonk and Cayan 2007). upper montane forest and occurs in small stands where mois-
The vegetation of the upper-montane forest is characterized ture is available. It is a vigorous and a profuse sprouter after
by the presence of California red ﬁr (Potter 1998). Figure 12.6 ﬁre (DeByle 1985). It becomes increasingly resistant to ﬁre as
S I E R R A N E VA D A B I O R E G I O N 281
TA B L E 12.8
Fire-response types for important species in the upper-montane forest ecological zone
Type of Fire Response
Lifeform Sprouting Seeding Individual Species
Conifer None None Resistant, killed Red ﬁr, Jeffrey pine, western
white pine, western juniper
Hardwood Fire stimulated None Resistant, top-killed Quaking aspen
Shrub Fire stimulated Abundant seed Top-killed Bush chinquapin, mountain
production whitethorn, huckleberry oak
None Fire stimulated Killed Whiteleaf manzanita, pinemat
Forb Fire stimulated None Top-killed Woolly mule’s ears
None None Top-killed Corn lily
Grass Fire stimulated Off-site Top-killed Tufted hairgrass
Tillers Off-site Top-killed Western needlegrass
F I R E R E G I M E–P LANT C OM M U N IT Y I NTE RACTION S
its diameter increases beyond 15 cm (6 in) (Brown and
Although the upper-montane forest receives a proportionally
Bush chinquapin, mountain whitehorn, and huckleberry
higher number of lightning strikes on a per area basis than
oak (Quercus vaccinifolia) form extensive stands in the open
the lower montane forest, fewer ﬁres result (van Wagtendonk
and underneath conifers. They are all sprouters and are top-
1994). Lightning is often accompanied with rain, and the
killed by ﬁre (Biswell 1974, Conard et al.1985). Mountain
compact fuel beds are not easily ignited. Those ﬁres that do
whitethorn is also a relatively proliﬁc seeder after ﬁre. Pine-
occur are usually of low intensity and spread slowly through
mat manzanita (Arctostaphylos nevadensis) and greenleaf
the landscape except under extreme weather conditions. Nat-
manzanita are usually found in the understory. Although
ural fuel breaks such as rock outcrops and moist meadows
these non-sprouting manzanitas are killed by intense heat,
prevent extensive ﬁres from occurring (Kilgore 1971).
they are able to reestablish by seed the ﬁrst year after ﬁre. Both
California red ﬁr fuel beds are among some of the heavi-
species may be obligate seeders, requiring ﬁre and/or charred
est and most compact found for conifers in the Sierra Nevada.
wood leachate to break seed dormancy (Kruckeberg 1977).
Although duff weight was just above average, woody fuel
Woolly mule’s ears (Wyethia mollis) apparently resprouts
weight was surpassed only by giant sequoia (van Wagten-
after ﬁre but the sprouting might not be ﬁre dependent
donk et al. 1998). The bulk density of California red ﬁr duff
(Mueggler and Blaisdell 1951). The density of mule’s ears has
fuels was above average, and the fuel bed bulk density,
been noted to increase after ﬁre (Young and Evans 1978).
including woody and litter fuels, was only exceeded by lim-
Corn lily (Veratrum californicum) grows in wet meadows and
ber pine. Such dense fuels ignite and carry ﬁre only under
is not usually affected by ﬁre. Based on its ability to resprout
extremely dry and windy conditions.
each year after being top-killed by frost, it is reasonable to
Fire regimes tend to be more variable in frequency and
assume that corn lily would sprout the year after being
severity than those in the lower montane forest (Table 12.9)
(Skinner and Chang 1996). Median ﬁre-return interval esti-
Western needlegrass (Achnantherum occidentalis) occurs in
mates from ﬁre scars range from 12 to 69 years (Skinner and
the understory of the conifer forests and is a tussock-forming
Chang 1996). Based on lightning ﬁres that were allowed to
grass that seeds into burns from off-site (Brown and Smith
burn under prescribed conditions in Yosemite National Park,
2000). The above-ground biomass is consumed, and intense
van Wagtendonk (1995) calculated the ﬁre rotation in Cali-
ﬁres can kill the rootstock. Tufted hairgrass is one of many
fornia red ﬁr to be 163 years. Occasional crown ﬁres occur in
grass and sedge species common in wet meadows. Although
California red ﬁr stands, but normally ﬁres spread slowly
it burns infrequently, tufted hairgrass generally survives all
because of compact surface fuels and the prevalence of natu-
but the most intense ﬁres and sprouts from the root crown,
ral terrain breaks.
as do most sedges.
282 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
TA B L E 12.9
Fire regime attributes for major vegetation types of the upper montane forest ecological zone
Red ﬁr Jeffrey pine, Tufted hairgrass
western white pine,
Seasonality Late summer–fall Summer–fall Late summer–fall
Fire-return interval Medium Medium Long
Size Medium Truncated small Small
Complexity Multiple Low Low
Intensity Multiple Low Low
Severity Multiple Low Low
Fire type Multiple Surface Surface
Fire regime terms used in this table are deﬁned in Chapter 4.
regimes (Lorentzen 2004). Quaking aspen stands burn in late
At the higher elevations in the upper-montane zone, ﬁre has
summer when the herbaceous plants underneath the quak-
an important role in the successional relationship between
ing aspens have dried sufﬁciently to carry ﬁre. Because quak-
California red ﬁr and lodgepole pine (Kilgore 1971). Fire cre-
ing aspen is a vigorous sprouter, it is able to recolonize burns
ates canopy openings by killing mature lodgepole pine and
immediately at the expense of non-sprouting conifers. Sim-
some mature California red ﬁr. Where lodgepole pine occurs
ilarly, meadows consisting primarily of tufted hairgrass burn
under a California red ﬁr canopy, it is eventually succeeded by
if ﬁres in adjacent forests occur during the late summer.
California red ﬁr. Pitcher (1987) concluded that ﬁre was nec-
Occasional ﬁres reduce encroachment into the meadows by
essary for creating openings where young California red ﬁr
conifers (deBennedetti and Parsons 1979).
trees could get established. In areas where crown ﬁres have
burned through California red ﬁr forests, montane chaparral
species such as mountain whitethorn and bush chinquapin
become established. Within a few years, however, California
red ﬁr and Jeffrey pine begin to overtop the chaparral. The subalpine forest lies between the upper-montane forest
Fires in Jeffrey pine, western juniper, and western white and the alpine meadows and shrublands. Extensive stands of
pine stands are usually moderate in intensity, burning subalpine forest occur on the west side of the Sierra Nevada
through litter and duff or, if present, through huckleberry and a thin band exists on the east side of the range. Like the
oak or greenleaf manzanita. Older trees survive these ﬁres, upper-montane zone below, the terrain is moderate on the
although occasionally an intense ﬁre may produce enough west side and steep on the east. Volcanic rocks are prevalent
heat to kill an individual tree (Wagener 1961a). Fuel bed in the north and granitic rocks occur throughout the zone.
bulk density and woody fuels weights are comparable for Soils are poorly developed.
the three species, but Jeffrey pine has three times as much The climate of the subalpine forest is moderate with cool
litter and twice as much duff (van Wagtendonk et al. 1998). summers and extremely cold winters. Other than occasional
As a result, surface ﬁres tend to be more intense in Jeffrey thundershowers, precipitation falls as snow. The snow-free
pine stands. Jeffrey pine will be replaced by huckleberry oak period is short, from mid June to late October. Lightning is
and greenleaf manzanita if ﬁres of high severity occur fre- pervasive in the subalpine forest with many more lightning
quently, or by California red ﬁr if the period between ﬁres strikes than might be expected by chance (van Wagtendonk
is sufﬁciently long (Bock and Bock 1977). Western juniper 1991a). Between 1985 and 2000, the average number of
strikes was 33.6 strikes yr 1 100 k 2 (87.1 strikes yr 1 100 mi 2)
is slow to return to burned areas and, like Jeffrey pine and
western white pine, will seed in from adjacent stands. (van Wagtendonk and Cayan 2007).
Although quaking aspen stands in the Sierra Nevada usually The vegetation of the subalpine forest is dominated by
burn only if a ﬁre from adjacent vegetation occurs at a time lodgepole pine (Fig. 12.7). As tree line is approached, lodge-
when the stands are ﬂammable, the decline of quaking aspen pole pine is replaced by mountain hemlock and whitebark
stands has been attributed to the absence of natural ﬁre pine. On the east side of the Sierra Nevada, limber pine
S I E R R A N E VA D A B I O R E G I O N 283
F I G U R E 12.7. Subalpine forest.
Lodgepole pine forms extensive
stands in this zone. Fire is infrequent
but when it occurs it burns from log
to log or creeps through the sparse
understory vegetation and litter.
occurs with whitebark pine, and in Sequoia National Park, plemented those created by tree-falls. When surface ﬁres
foxtail pine is found at tree line. Extensive meadows of short- occur in lodgepole pine forests, individual trees are killed
hair sedge (Carex ﬁlifolia var. erostrata) and Brewer’s reedgrass (deBennedetti and Parsons 1984). Occasional crown ﬁres can
(Calamagrostis breweri) are mixed within the forest. consume entire stands, which are quickly recolonized by
The combination of thin bark, ﬂammable foliage, low-
F I R E R E S P ON S E S OF I M P ORTANT S P ECI E S
hanging branches, and growth in dense groups make moun-
Subalpine trees are easily killed by ﬁre at a young age but tain hemlocks susceptible to ﬁre (Fischer and Bradley 1987).
increase their resistance as they grow older (Table 12.10). As the trees mature, the bark thickens giving them some
Clements (1916) was one of the ﬁrst ecologists to consider protection. Whitebark pine survives ﬁres because large refu-
lodgepole pine to be a ﬁre type. Its thin bark, ﬂammable gia trees are scattered in areas of patchy fuels (Keane and
foliage, and serotinous cones all ﬁt into the classical deﬁnition Arno 2001). Clark’s nutcrackers (Nucifraga columbiana) facil-
of a ﬁre-adapted species. The cones of the Sierra Nevada sub- itate post-ﬁre seedling establishment (Tomback 1986). Bark
species, however, are not fully serotinous, open at maturity, thickness is moderate and mature trees usually survive low-
and are dispersed over a two-year period (Lotan 1975). Parker and sometimes moderate-intensity surface ﬁres, whereas
(1986) concluded that ﬁre was not necessary for the perpetu- smaller trees do not. Limber pines also have moderately
ation of lodgepole pine, but ﬁre-induced openings sup- thin bark, and young trees often do not survive surface ﬁres
284 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
TA B L E 12.10
Fire response types for important species in the subalpine forest ecological zone
Type of Fire Response
Lifeform Sprouting Seeding Individual Species
Conifer None Fire stimulated Killed Lodgepole pine
None None Resistant, killed Mountain hemlock
None None Resistant, killed Whitebark pine, limber pine,
Grass Fire stimulated None Top-killed Brewer’s reedgrass
TA B L E 12.11
Fire regime attributes for vegetation types of the subalpine forest ecological zone
Lodgepole pine Mountain Whitebark pine,
hemlock limber pine,
Seasonality Late summer–fall Late summer–fall Late summer–fall
Fire-return interval Long Long Truncated long
Size Small Small Small
Complexity Low Low Low
Intensity Multiple Low Low
Severity Multiple Low Low
Fire type Multiple Surface Surface
Fire regime terms used in this table are deﬁned in Chapter 4.
(Keeley and Zedler 1998). Terminal buds are protected from Lodgepole pine fuel beds are relatively shallow and com-
the heat associated with crown scorch by the tight clusters pact (van Wagtendonk et al. 1998). Often herbaceous plants
of needles around them. Foxtail pine occurs where fuels to occur in the understory, precluding ﬁre spread except under
carry ﬁres are practically nonexistent (Parsons 1981). The extremely dry conditions. When ﬁres do occur, encroaching
charred remains of trees struck by lightning are evidence California red ﬁrs and mountain hemlocks are replaced by
that periodic ﬁres do occur, although they seldom spread the more proliﬁc–seeding lodgepole pines. In areas where
over large areas. lodgepole pines have invaded meadows, ﬁres will kill back
the trees (deBennedetti and Parsons 1984). Stand-replacing
ﬁres are rare, but when they do occur, lodgepole pines
F I R E R E G I M E–P LANT C OM M U N IT Y I NTE RACTION S
become reestablished from the released seeds.
Although lightning strikes are plentiful in the subalpine for- Keeley (1981) estimated the ﬁre-return interval in lodgepole
est zone, ignitions are infrequent. Between 1930 and 1993, pine to be several hundred years. Data from ﬁres that have
lightning caused only 341 ﬁres in the zone in Yosemite burned in the wildland ﬁre-use zone in Yosemite suggest a ﬁre
National Park, (van Wagtendonk 1994). Those ﬁres burned rotation of 579 years (van Wagtendonk 1995). Caprio (2002),
only 2,448 ha (5,953 ac), primarily in the lodgepole forest. however, found that prior to 1860, widespread ﬁres were
During the period between 1972 and 1993 when lightning recorded in 1751, 1815, and 1846 in lodgepole pine stands in
ﬁres were allowed to burn under prescribed conditions, only Sequoia National Park. In any case, ﬁres are relatively rare and
six ﬁres in lodgepole pine grew larger than 123 ha (300 ac). usually light to moderately severe. (Table 12.11)
S I E R R A N E VA D A B I O R E G I O N 285
Eastside Forest and Woodland
Little information exists for the role of ﬁre in mountain
hemlock forests in the Sierra Nevada. In Montana, however,
The width of the eastside montane zone of the Sierra
ﬁres in the cool, wet mountain hemlock forests generally
Nevada varies from north to south. In the north, the width
occur as infrequent, severe stand-replacing crown ﬁres (Fis-
of the zone is more than 12.5 km (20 mi), but to the south
cher and Bradley 1987). Fire-return intervals are estimated to
it quickly becomes less than 1 km (0.6 mi) due to the high
be between 400 and 800 years (Habeck 1985). During the
elevation of the crest, increased importance of the rain
28-year period prior to 1972, no ﬁres burned in hemlock
shadow effect, and the sharp gradient from upper montane
forests in the wildland ﬁre-use zone of Yosemite National
to Great Basin vegetation. In the northern Sierra Nevada,
Park (van Wagtendonk et al. 2002). Litter and duff fuels of
the eastside montane zone increases in width, as the crest
mountain hemlocks were some of the deepest, heaviest, and
of the Sierra Nevada becomes lower and less distinct. The
most compact of any Sierra Nevada conifer, indicating long
area to the north and east of Lake Tahoe basin comprises
periods between ﬁres (van Wagtendonk et al. 1998). Moun-
large expanses of eastside forest and woodland vegetation.
tain hemlock is replaced by lodgepole pine in areas where
Some of the species, such as Jeffrey pine, are at the eastern
both are present before a ﬁre. Seeding from adjacent areas is
edge of their distribution. Others, such as pinyon pine and
possible but can take several years to be successful.
sagebrush, are at their western edge of distribution (Fig.
Fire seldom burns in the pine stands that occur at tree line.
12.8). Small climatic shifts may have resulted in dramatic
There have been only 25 lightning ﬁres in whitebark pine dur-
shifts in vegetation, ﬁre, and plant community–ﬁre inter-
ing the past 70 years in Yosemite (van Wagtendonk 1994).
actions. Lightning is common in the eastside zone with
Only four of these ﬁres grew larger than 0.1 ha (0.25 ac), and
28.9 strikes yr–1 100 k 2 (74.8 strikes yr 1 100 mi 2) for the
they burned a total of 4 ha (9 ac). Based on the area burned
period between 1985 and 2000 (van Wagtendonk and
in the type, van Wagtendonk (1995) calculated a ﬁre rotation
Cayan 2007). Proportionally more lightning strikes occur in
of more than 23,000 years. Although no records exist show-
the northern part of the zone than in any other zone in the
ing ﬁres in limber pine stands in the Sierra Nevada, it is rea-
sonable to assume equally long ﬁre-return intervals for that
The vegetation of the eastside of the Sierra Nevada is
species as well. Scattered pockets of fuel beneath both white-
often transitional between upper montane and lower-ele-
bark pine and limber pine attest to the long period between
vation Great Basin species. A variable, but often coarse-
ﬁres. Limber pine recorded the heaviest litter and duff load of
scale mosaic of open woodlands or forests and shrublands
any Sierra Nevada conifer (van Wagtendonk et al. 1998). On
or grasslands, is characteristic. This is similar to the east side
the other hand, foxtail pine had hardly any fuel beneath it.
of the Cascades or northeastern California. The most preva-
Keifer (1991) found only occasional evidence of past ﬁres in
lent tree-dominated types include Jeffrey pine or mixed Jef-
foxtail stands. She noted sporadic recruitment in those stands
frey and ponderosa pine woodlands, mixed white ﬁr and
that did not appear to be related to ﬁre and suggested that the
pine forests, white ﬁr, and quaking aspen groves. In some
thick bark on the mature trees protected them from low-
locations, particularly in the central and southern portions,
pinyon pine occurs. Typically, westside species (i.e., Dou-
Little is known about ﬁre in subalpine meadows. These
glas-ﬁr and black oak) occur in small amounts in the north-
meadows are sometimes ignited when adjacent forests are
ern Sierra Nevada. The shrublands can be extensive and
burning. Brewer’s reedgrass can become re-established after
variable, ranging from typical Great Basin species of sage-
ﬁre from seeds and rhizomes. Meadow edges are maintained
brush (Atemisia spp.) and bitterbrush (Purshia spp.) to chap-
by ﬁre as invading lodgepole pines are killed (deBenndetti
arral comprised of tobacco brush (Ceanothus velutinus var.
and Parsons 1984, Vale 1987).
velutinus), greenleaf manzanita, bearbrush (Garrya fremon-
tia), and bush chinquapin. Curl-leaf mountain-mahogany
Alpine Meadow and Shrubland
(Cercocarpus ledifolia) occurs in patches on rocky and par-
ticularly dry sites. Riparian and wetland areas occur
The alpine meadow and shrubland zone consists of fell ﬁelds
throughout, and, although this is the most xeric portion of
and willows along riparian areas. The short growing season
the Sierra Nevada, meadows can be extensive. Quaking
produces little biomass and fuels are sparse. Lighting strikes
aspen, black cottonwood, and various willow species dom-
occur regularly in the alpine zone but result in few ﬁres (van
inate the overstory of riparian communities of larger
Wagtendonk and Cayan 2007). The 16-year average number
of strikes in the Sierra Nevada is 32.2 yr 1 100 k 2 (83.5 streams. Lodgepole pine is also common in riparian areas or
strikes yr 1 100 mi 2). Weather, coincident with lightning, localized areas with cold air drainage.
Because of the Sierra Nevada bioregion’s similarities with
is usually not conducive to ﬁre ignition or spread. Fires are
the Northeastern Plateaus (Chapter 11) and Southern Cas-
so infrequent that they probably did not play a role in the
cades (Chapter 10) bioregions, the focus of this chapter is on
evolutionary development of the plants that occur in the
the Jeffrey pine woodlands, mixed Jeffrey pine–white ﬁr
alpine zone. The 70-year record of lightning ﬁres in Yosemite
forests, and montane chaparral. Additional information on
includes only eight ﬁres, burning a total of 12 ha (28 ac), pri-
communities dominated by Great Basin or desert species
marily in a single ﬁre (van Wagtendonk 1994).
286 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
F I G U R E 12.8. Eastside forest and
woodland. This stand of Jeffrey pine
and red ﬁr was recently burned and
shows evidence of manzanita
such as juniper, pine, and sagebrush or bitterbrush, can be dency to have pitchy bark, branches, and foliage, making it
found in the Northeastern Plateaus chapter (Chapter 11) and ﬂammable. In this zone, pinyon pine often occupies rocky
Southeastern Deserts chapter (Chapter 16). sites with sparse vegetation and fuels that decrease the like-
lihood of frequent ﬁre. Seeds of both ponderosa pine and
lodgepole pine show a high tolerance to heat, showing ger-
F I R E R E S P ON S E S OF I M P ORTANT S P ECI E S
mination over 50% after 5-minute exposures to heat as high
Some of the dominant species in this zone are also prevalent as 930°C (200°F) (Wright 1931).
in the upper montane or adjacent lower montane zones and Shrub species vary from those that have enhanced
are only described as they co-occur in this zone. Species in sprouting or seed germination following ﬁre to those that
this zone tend to be a mixture of those with ﬁre-resistant or have little ﬁre resistance. Greenleaf manzanita, bearbrush,
ﬁre-enhanced characteristics and those that are ﬁre inhibited bush chinquapin, and tobacco brush all sprout from basal
(Table 12.12). Jeffrey pine has thick, ﬁre-resistant bark; large, burls following ﬁre. Where branches are pressed against the
well-protected buds; and self-pruning that often results in soil from snow, layering results in sprouting; however,
high crowns. Pinyon pine is not very ﬁre resistant, with these sprouts can be more susceptible to fire mortality.
crowns low to the ground; relatively thin bark; and a ten- Tobacco brush also has enhanced germination from ﬁre.
S I E R R A N E VA D A B I O R E G I O N 287
TA B L E 12.12
Fire response types for important species in the eastside forest and woodland ecological zone
Type of Fire Response
Lifeform Sprouting Seeding Individual Species
Conifer None None Resistant, killed Jeffrey pine, ponderosa pine
None None Low resistance, killed Pinyon pine
Hardwood Fire stimulated None Top-killed Quaking aspen, black
Shrub Fire stimulated None Top-killed Bush chinquapin, greenleaf
manzanita, huckleberry oak,
Fire stimulated Fire stimulated Top-killed Tobacco brush
None None Killed
Herb Fire stimulated None Top-killed Woolly mule’s ears
Grass Fire stimulated None Top-killed Sedges
Killed Cheat grass
Bitterbrush has a variable sprouting response to ﬁre.
TA B L E 12.13
Fire regime attributes for vegetation types of the eastside forest and woodland ecological zone
Jeffrey pine, White ﬁr and Chaparral
ponderosa pine mixed conifer
Seasonality Summer–fall Summer–fall Summer–fall
Fire-return interval Short Medium Medium
Size Small–Medium Medium Medium
Complexity Multiple Multiple Low
Intensity Low Multiple High
Severity Low Multiple High
Fire type Surface Multiple Crown
Fire regime terms used in this table are deﬁned in Chapter 4.
F I R E R E G I M E–P LANT C OM M U N IT Y I NTE RACTION S white pine. Taylor’s (2004) work southeast of Lake Tahoe
showed a mean ﬁre return interval of 11.4 years for presettle-
ment mixed Jeffrey pine and white ﬁr stands. As recent, severe
Only a few ﬁre history studies have been conducted in the east-
ﬁres have burned on the lower slopes of the eastside forests, the
ern montane zone. In an area east of the crest near Yosemite,
boundary between forests and sagebrush has retreated up slope.
Stephens (2001) found median ﬁre-return intervals of 9 years
Fire regimes vary with both vegetation type and landscape
for Jeffrey pine and 24 years for adjacent upper-montane for-
location (Table 12.13). The most-frequent ﬁres and lowest-
est consisting of California red ﬁr, lodgepole pine, and western
288 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
intensity ﬁres occurred in the lower elevation, open pine- are two contrasting ﬁre management conditions in the mon-
dominated areas of this zone, with responses similar to that tane and eastern portions of the Sierra Nevada: one where
described in the Northeastern Plateaus (Chapter 11). On less communities are adjacent to and mixed with wildlands; the
productive or more southern portions, Jeffrey pine wood- second where vast areas are undeveloped, often bordering
lands likely had a ﬁre regime similar to those described for higher-elevation wilderness. The former creates conditions in
upper montane Jeffrey pine woodlands, with a range of inter- which intensive and frequent fuel-reduction treatments around
vals from 5 to 47 years (Taylor 2004). White ﬁr forests communities are important because of the frequent occurrence
occurred in a mosaic with chaparral on the more mesic sites of ﬁre in this area. The latter is well suited for wildland ﬁre use,
on north slopes and at higher elevations. The ﬁre regimes a program that restores naturally occurring ﬁres through less
included a greater variety of severities, due, in part, to less- intensive and expensive means. The situation in the intermix
consistent ﬁre intervals and patterns. The ﬁre season was pri- areas has serious ramiﬁcations for ﬁre management. Property
marily from summer through fall, with longer seasons at owners demand that ﬁre suppression forces protect their homes
lowest elevations in open pine forests. ﬁrst, thus diverting them from protecting resources.
The ﬁre regime for the white ﬁr–chaparral type apparently
F I R E AN D F U E LS MANAG E M E NT
included some high-severity ﬁres in the past (Russell et al.
1998), although the importance of settlement activities on Each new catastrophic ﬁre increases the clamor to do some-
contributing to these types of ﬁres is unclear. The structure thing about fuels. Homeowners expect ﬁre and land man-
of white ﬁr forests leads to higher crown-ﬁre potential agement agencies to act, yet are often unwilling to accept
(Conard and Radosevich 1982). Branch retention, high stand some of the responsibility themselves. The most immediate
densities, and low and uniform crowns are all common. problem exists around developments and other areas of high
Regeneration of white ﬁr is continuous (Bock et al.1978, societal values. Mechanical removal of understory trees fol-
Conard and Radosevich 1982) until a ﬁre occurs. Subse- lowed by prescribed burning is the most likely treatment to
quently, portions of the forest are converted to chaparral succeed in these areas. Where houses have encroached into
dominated by sprouting greenleaf manzanita and both shrublands, removal of shrubs up to 30 m (100 ft) may be nec-
sprouting and heat-stimulated germination of tobacco brush essary. Less compelling are treatments in remote areas where
(Conard and Radosevich 1982). The duration of this ﬁre-gen- there is less development and access is difﬁcult. Prescribed
erated chaparral can last for more than 50 years (Russell et al. burning and the use of naturally occurring ﬁres are more
1998). The relative amounts of pine and white ﬁr regeneration appropriate in areas beyond the urban-wildland interface.
are affected by ﬁre. Pine regeneration can increase from 25% The call to thin forests to prevent catastrophic ﬁres has
in forests with no ﬁre to greater than 93% in forests with ﬁre confused the issue. As we have learned in Chapter 3, only in
(Bock and Bock 1969). Fire can also serve as a control over rare occasions can a ﬁre move independently through the
regeneration by limiting the density of white ﬁre recruitment crowns of trees without a surface ﬁre to feed it. Thinning
(Bock et al. 1976), but white ﬁr can also regenerate well under forests to prevent crown ﬁres without treating surface fuels
the shade of chaparral (Conard and Radosevich 1982). is ecologically inappropriate and economically unjustiﬁable.
A combination of treatments including understory thinning
and prescribed ﬁre will probably be most productive.
Private property owners, land managers, and the public in
Species at Risk
the Sierra Nevada face many issues as a result of changed ﬁre
Several species at risk occur in the Sierra Nevada, and many of
regimes and population growth. Primary among the issues is
these, including the Paciﬁc ﬁsher (Martes pennanti paciﬁca),
the accumulation of fuels both on the ground and in tree
American marten (Martes americana), and California spotted
canopies. Dealing with these fuels has become more compli-
owl (Strix occidentalis occidentalis), evolved in ﬁre-dependent or
cated by increased urbanization, at-risk species, and air qual-
ﬁre-maintained habitats. Concurrent changes in ﬁre regimes
and vegetation in the lower-elevation portions of the Sierra
Nevada foothill and lower montane zones have resulted in
region-wide changes in vegetation and wildlife habitats,
The population of the Sierra Nevada more than doubled including the stability of those habitats. Low-severity ﬁre
between 1970 and 1990 (Duane 1996). Much of this growth regimes made low-contrast changes to previous regional pat-
has occurred in the foothills of the Sierra Nevada. In particu- terns of vegetation and habitat. Today, moderate- to high-
lar, the central Sierra Nevada contains one of the largest areas severity ﬁres produce high-contrast changes. These changes
of intermixed urban and wildlands in California. This creates have implications for wildlife habitat that varies with vegeta-
changes in ﬁre patterns and restricts restoration or fuels reduc- tion. Habitat with denser forests was more distributed and less
tion. The relatively higher productivity chaparral of the Sierra widespread. Currently, however, denser forests dominate but
Nevada foothills means that growth rates are higher and main- are punctuated with large, non-forest openings created by
tenance of fuel-reduction areas more frequent and costly. There severe ﬁres.
S I E R R A N E VA D A B I O R E G I O N 289
Presettlement Forest Conditions
The question becomes how to restore natural ﬁre regimes
without adversely affecting at-risk species and their habitats. To
Researchers have been uncertain about the vegetation con-
do nothing only makes the situation worse, predisposing the
ditions of the Sierra Nevada in presettlement times. Under-
species and habitats to destruction by catastrophic ﬁre. These
standing those conditions and the factors that led to them
species evolved with ﬁre and the answer must include ﬁre. Care
gives insights into possible management targets and meth-
must be taken, however, to ensure that fragmented populations
ods to reach those targets. Comparative photos have proven
are not adversely affected by ﬁre treatment activities.
useful, but detailed re-measurement of historic vegetation
surveys holds the greatest promise. Several of these surveys
were conducted in the late 1800s and early 1900s in many
One of the biggest impediments to conducting prescribed parts of the Sierra Nevada and should prove productive if
burns or using wildland ﬁres to achieve resource beneﬁts in the they can be relocated. Information derived from resurveys
Sierra Nevada is restrictions on air quality. Smoke is a byprod- would give the best estimate of what have been called “old
uct of burning, whether it comes from a prescribed ﬁre, a forest” or “late successional” conditions because the original
wildland ﬁre burning under prescribed conditions, or a wild- surveys included the effects of naturally occurring ecologi-
ﬁre. Catastrophic wildland ﬁres produce extreme concentra- cal processes such as ﬁre.
tions of smoke that exceed public health standards (see
Chapter 21 for additional information). Society is faced with
Effects of Fire on Ecosystem Properties
deciding to accept periodic episodes of low concentrations of
smoke from managed ﬁres or heavy doses from wildﬁres.
Although it will never be possible to know all of the effects
Either reduced emission restrictions for wildland management
of ﬁre, investigators should continue to determine those
activities or exemptions for federal agencies from the local air
effects of greatest importance to society and to ecosystem
pollution control district regulations will be necessary if ﬁre is
function. These include the effects of ﬁre on coarse woody
to be allowed to play its natural role in the Sierra Nevada.
debris including logs and snags. The role ﬁre plays in the
dynamics of these structural habitat components is not well
Research Needs understood.
Smoke is another ecosystem process that warrants addi-
Skinner and Chang (1996) developed a comprehensive list of
tional study. Some preliminary investigations have looked at
research needs during the Sierra Nevada Ecosystem Project.
the interactions of smoke with fungi and bacteria in forested
They identiﬁed six research topics, which we have grouped
ecosystems. Attempts need to be made to determine the pre-
into three general areas: (1) spatial and temporal dynamics
settlement air quality conditions for comparison to those
of ﬁre, (2) presettlement forest conditions, and (3) effects of
now experienced with wildland ﬁre use, suppressed wild-
ﬁre on ecosystem processes.
land ﬁres, and prescribed ﬁres.
Spatial and Temporal Dynamics of Fire
Although much has already been learned about the dynam-
John Muir named the Sierra Nevada the Range of Light; an
ics of ﬁre and Sierra Nevada ecosystems, several speciﬁc top-
even better name might have been the Range of Fire. Fires have
ics still need to be addressed. Fire history data are sparse
been a part of the Sierra Nevada for millennia and will continue
through much of the Sierra Nevada. Isolated studies are the
to be so in the future. This chapter has looked at the factors that
rule, although comprehensive data sets exist for the
have contributed to make ﬁre an important process in the eco-
national parks and the area around Lake Tahoe. Complete
logical zones of the range and how ﬁre has interacted with veg-
fire histories would elucidate the spatial and temporal
etation in each zone. The success of our management of the
aspects of landscape-level ﬁre interactions. Related studies on
Sierra Nevada is contingent on our ability and willingness to
the spatial and temporal interactions of climate, vegetation,
keep ﬁre an integral part of these ecosystems. To not do so is
and ﬁre are needed.
to doom ourselves to failure; ﬁre is inevitable and we must try
There is also a need for more information about the effects
to manage only in harmony with ﬁre.
of frequent low- to moderate-severity ﬁres on vegetation pat-
terns. Most information available today is on low-severity
prescribed ﬁre or high-severity wildﬁres. Naturally occurring
low- to moderate-intensity ﬁres were probably the norm,
Agee, J.K., B. Bahro, M.A. Finney, P.N. Omi, D. B. Sapsis, C. N.
and their ecological role is not well understood. Similarly, lit-
Skinner, J.W. van Wagtendonk, and C.P. Weatherspoon. 2000.
tle is known about the interaction of ﬁre with some of the The use of fuel breaks in landscape ﬁre management. Forest
other dynamic ecosystem processes, such as insect and fungi Ecology and Management 127:55–66.
population ﬂuctuations. These processes combine to affect Anderson, M.K. 1996. The ethnobotany of deergrass, Muhlenber-
ﬁre behavior and subsequent ﬁre effects and vegetation gia rigens (Poaceae): its uses and ﬁre management by Califor-
responses. nia Indian tribes. Econ. Bot. 50:409–422.
290 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
Anderson, M.K. 1999. The ﬁre, pruning, and coppice manage- Caprio, A.C. 2002. Fire history of lodgepole pine on Chagoopa
ment of temperate ecosystems for basketry material by Plateau, Sequoia and Kings Canyon National Parks. P. 38 in
California Indian tribes. Human Ecology 27:79–113. Abstracts 2002 ﬁre conference, managing ﬁre and fuels in the
Anderson, R.S. 1990. Holocene forest development and paleo- remaining wildlands and open spaces of the southwestern
climates within central Sierra Nevada, California. J. Ecology United States. Association for Fire Ecology. 98 p.
78:470–489. Caprio, A. C., and T. W. Swetnam. 1995. Historic ﬁre regimes
Anderson, R.S. 1994. Paleohistory of a giant sequoia grove: the along an elevational gradient on the western slope of the
record from Log Meadow, Sequoia National Park. P. 49–55 in Sierra Nevada, California. P. 173–179 in J. K. Brown, R. W.
P.S. Aune (tech. coord.), Proceedings of symposium on giant Mutch, C. W. Spoon, and R. H. Wakimoto (tech. coords.), Pro-
sequoias: their place in ecosystem and society. USDA For. Serv. ceedings symposium on ﬁre in wilderness and park manage-
Gen. Tech. Rep. PSW-151. 170 p. ment. USDA Forest Service Gen. Tech. Rep. INT-GTR 320.
Anderson, R.S., and S.L. Carpenter. 1991. Vegetation changes in Christensen, N., L. Cotton, T. Harvey, R. Martin, J. McBride, P.
Yosemite Valley, Yosemite National Park, California, during the Rundel, and R. Wakimoto. 1987. Review of ﬁre management
protohistoric period. Madrono 38:1–13. programs for sequoia–mixed conifer forests of Yosemite,
Anderson, R. S., and S. J. Smith. 1997. The sedimentary record of Sequoia, and Kings Canyon national parks. Unpub. Report,
ﬁre in montane meadows, Sierra Nevada, California, USA: a National Park Service, Western Region, San Francisco.
preliminary assessment. P. 313–327 in J. S. Clark, H. Cachier, Clements, F.E. 1916. Plant succession. Carnegie Inst. Washington
J. G. Goldammer, and B. J. Stocks (eds.), Sediment records of Pub. 242. 512 p.
biomass burning and global change. NATO ASI Series 51. Conard, S.G., A.E. Jaramillo, K. Cromack, and S. Rose. 1985. The
Barbour, M.G., N.H. Berg, T.G.F. Kittel, and M. E. Kunz. 1991. Snow- role of the genus Ceanothus in western forest ecosystems.
pack and the distribution of a major vegetation ecotone in the USDA For. Serv. Gen. Tech. Rep. PNW-182. 72 p.
Sierra Nevada of California. Journal of Biogeography 18:141–149. Conard, S.G., and S.R. Radosevich. 1982. Post-ﬁre succession in
Biswell, H.H. 1959. Man and ﬁre in ponderosa pine in the Sierra white ﬁr (Abies concolor) vegetation of the northern Sierra
Nevada of California. Sierra Club. Bul. 44:44–53. Nevada. Madrono 29:42–56.
Biswell, H.H. 1961. The big trees and ﬁre. National Parks Maga- deBennedetti, S.H., and D.J. Parsons. 1979. Natural ﬁre in sub-
zine 35:11–14. alpine meadows: a case description from the Sierra Nevada.
Biswell, H.H. 1972. Fire ecology in ponderosa pine-grassland. Journal of Forestry 77:477–479.
Proceedings Tall Timbers Fire Ecology Conference 12:69–96. deBennedetti, S.H., and D.J. Parsons. 1984. Post-ﬁre succession
Biswell, H.H. 1974. Effects of ﬁre on chaparral. P. 321–364 in T.T. in a Sierran subalpine meadow. American Midland Naturalist
Kozlowski and C.E. Ahlgren (eds.), Fire and ecosystems. Aca- 111:118–125.
demic Press, New York. 542 p. DeBruin. H. W. 1974. From ﬁre control to ﬁre management: a
Bock, C.E., and J.H. Bock. 1977. Patterns of post-ﬁre succession major policy change in the Forest Service. Proceedings of the
on the Donner Ridge burn, Sierra Nevada. P. 464–469 in H.A. Tall Timbers Fire Ecology Conference 14:11–17.
Mooney and C.E. Conrad (tech. coords.), Proceedings sympo- DeByle, N.V. 1985. The role of ﬁre in aspen ecology. In J. E. Lotan,
sium, environmental consequences of ﬁre and fuel manage- B. M. Kilgore, W.C. Fischer, and R.W. Mutch (tech. coords),
ment in mediterranean ecosystems. USDA, For. Serv. Gen. Proceedings—Symposium and workshop on wilderness ﬁre.
Tech. Rep. WO-3. 498 p. USDA For. Serv. Gen. Tech. Rep. INT-182. 326 p.
Bock, J. H., and C. E. Bock. 1969. Natural reforestation in the Duane, T. P. 1996. Human settlement, 1850–2040. In Sierra
northern Sierra Nevada-Donner Ridge burn. Proceedings Tall Nevada Ecosystem Project: Final report to Congress, Volume II,
Timbers Fire Ecology Conference 9:119–126. Chapter 11. University of California, Davis, Wildland
Bock, J.H., C.E. Bock, and V.M. Hawthorne. 1976. Further stud- Resources Center Rep. 37. 1528 p.
ies of natural reforestation in the Donner Ridge burn. Pro- Fischer, W.C., and A.F. Bradley. 1987. Fire ecology of western
ceedings of the Annual Tall Timbers Fire Ecology Conference Montana forest habitat types. USDA For. Serv.Gen. Tech. Rep.
14:195–200. INT-223. 95 p.
Bock, J.H., M. Raphael, and C.E. Bock. 1978. A comparison of Fites-Kaufman, J. 1997. Historic landscape pattern and process:
planting and natural succession after a forest ﬁre in the north- ﬁre, vegetation, and environment interactions in the northern
ern Sierra Nevada. Journal of Applied Ecology 15:597–602. Sierra Nevada. Unpub. PhD Dissertation, University of Wash-
Bonnickson, T.M., and E.P. Stone. 1982. Reconstruction of a pre- ington. 175 p.
settlement giant sequoia–mixed conifer forest community Fowells, 1979. Silvics of forest trees of the United States. USDA
using the aggregation approach. Ecology: 63:1134–1168. Agric. Handbook 271. 761 p.
Bouldin, J.R. 2000. Twentieth century changes in forests of the Franklin, J.F., and J.K. Agee. 2003. Foraging a science-based
Sierra Nevada, California. Unpub. PhD diss. University of Cal- national forest ﬁre policy. Issues in Science and Tech. Fall 2003.
ifornia, Davis. 219 p. Gruell, G.E. 2001. Fire in Sierra Nevada forests: a photographic
Boyce, J. S. 1920. The dry rot of incense cedar. USDA Bul. 871. interpretation of ecological change since 1849. Mountain
58 p. Press, Missoula, MT. 238 p.
Brown, J.K., and N.V. DeByle. 1987. Fire damage, mortality, and Haase, S.M., and S.S. Sackett. 1998. Effects of prescribed ﬁre in
suckering in aspen. Canadian Journal of Forest Research 17: giant sequoia–mixed conifer stands in Sequoia and Kings
1100–1109. Canyon National Parks. Proceedings Tall Timbers Fire Ecology
Brown, J. K., and J.K. Smith. 2000. Wildland ﬁre in ecosystems: Conference 20:236–243.
effects of ﬁre on ﬂora. USDA For. Serv. Gen. Tech. Rep. RMRS- Habeck, J.R. 1985. Impact of ﬁre suppression on forest succession
GTR-42-vol. 2. 257 p. and fuel accumulations in long-ﬁre-interval wilderness habitat
S I E R R A N E VA D A B I O R E G I O N 291
types. P. 110–118 in J.E. Lotan, B. M. Kilgore, W.C. Fischer, and Kilgore, B.M., and H.H. Biswell. 1971. Seedling germination after
R. W. Mutch (tech. coords.), Proceedings symposium and prescribed ﬁre. California Agriculture 25:163–169.
workshop on wilderness ﬁre. USDA Forest. Serv. Gen. Tech. Kilgore, B.M., and G.M. Briggs. 1972. Restoring ﬁre to high ele-
Rep. INT-182. 434 p. vation forests in California. Journal of Forestry 70:266–271.
Hartesveldt, R.J. 1962. Effects of human impact on Sequoia gigan- Kilgore, B. M., and D. Taylor. 1979. Fire history of a sequoia
tean and its environment in the Mariposa Grove, Yosemite mixed-conifer forest. Ecology 60:129–142.
National Park, California. Unpub. PhD diss. University of Knight, R. 1997. A spatial analysis of a Sierra Nevada old-growth
Michigan, Ann Arbor. 310 p. mixed-conifer forest. Masters Thesis, University of Washing-
Hartesveldt, R.J. 1964. Fire ecology of the giant sequoias: con- ton. 84 p.
trolled ﬁre may be one solution to survival of the species. Kruckeberg, A.R. 1977. Manzanita (Arctostaphylos) hybrids in the
National History Magazine 73:12–19. Paciﬁc Northwest: effects of human and natural disturbance.
Hartesveldt, R. J., and H. T. Harvey. 1967. The ﬁre ecology of Systematic Botany 2:233–250.
sequoia regeneration. Proceedings of the Annual Tall Timbers Lawrence, G.E. 1966. Ecology of vertebrate animals in relation to
Fire Ecology Conference 7:65–77. chaparral ﬁre in the Sierra Nevada foothills. Ecol. 47:278–291.
Harvey, H.T., H.S. Shellhammer, and R.E. Stecker. 1980. Giant Leiburg, J. B. 1902. Forest conditions in the northern Sierra
sequoia ecology. National Park Service Sci. Monog. 12. 182 p. Nevada, California. USGS Prof. Pap. 8. U.S. Government Print-
Heisey, R. M., C. C. Delwiche, R. A. Virginia, A. F. Wrona, and ing Ofﬁce, Washington, DC. 194 p.
B.A. Bryan. 1980. A new nitrogen-ﬁxing non-legume: Chamae- Lorentzen, E. 2004. Aspen delineation project. Bureau of Land
batia foliolosa (Rosaceae). Amer. J. Botany 67(3):429–431. Manage., California State Ofﬁce, Resource Note 72. 2 p.
Hill, M. 1975. Geology of the Sierra Nevada. University of Cali- Lotan, J. E. 1975. Cone serotiny—ﬁre relationships in lodgepole
fornia Press, Berkeley. 232 p. pine. Proceedings Tall Timbers Fire Ecology Conference
Huber, N.K. 1987. The geologic story of Yosemite National Park. 14:267–278.
U. S. Geol. Surv. Bul. 1595. 64 p. Major, J. 1988. California climate in relation to elevation.
Hull, K.L., and M.J. Moratto. 1999. Archeological synthesis and P. 11–74 in M. C. Barbour and J. Major. Terrestrial vegetation
research design, Yosemite National Park, California. Yosemite of California. Wiley-Interscience, New York. 1002 p.
Research Center Publications in Anthropology No. 21. McDonald, P.M. 1981. Adapatations of woody shrubs. P. 21–29
Yosemite National Park. in S. D. Hobbs and O. T. Helgerson (eds.), Reforestation of
Hull, M. K., C.A. O’Dell, and M. K. Schroeder. 1966. Critical ﬁre skeletal soils: proceedings of a workshop. Oregon State Uni-
weather patterns—their frequency and levels of ﬁre danger. versity, Forest Research Laboratory.
USDA For. Serv. Paciﬁc Southwest Forest and Range Expt. Sta., McKelvey, K.S., and K.L. Busse. 1996. Twentieth century ﬁre pat-
Berkeley. 40 p. terns on Forest Service lands. In Sierra Nevada Ecosystem Pro-
Jepson, W.L. 1921. The ﬁre type of forest of the Sierra Nevada. ject: Final report to Congress, Volume II, Chapter 41. Univer-
The Intercollegiate Forestry Club Annual 1:7–10. sity California, Davis, Wildland Resources Center Rep. 37.
Kauffman, J.B., and R.E. Martin. 1990. Sprouting shrub response to 1528 p.
different seasons and fuel consumption levels of prescribed ﬁre Minnich, R.A., M.G. Barbour, J. H. Burk, and R.F. Fernau. 1995.
in Sierra Nevada mixed conifer ecosystems. Forest Science Sixty years of change in California conifer forests of the San
36:748–764. Bernadino Mountains. Conservation Biology 9:902–914.
Keane, R. E., and S.F. Arno. 2001. Restoration concepts and tech- Miles, S.R., and C.B. Goudy (comps.). 1997. Ecological subre-
niques. P. 367–400 in D. Tomback, S.F. Arno, and R.E. Keane gions of California. USDA For. Serv. RM-EM-TP-005. 216 p.
(eds.), Whitebark pine communities: ecology and restoration. Muir, J. 1895. Thoughts upon national parks. P. 350–354 in L. M.
Island Press, Washington, DC. 328 p. Wolfe (ed.), 1979. John of the mountains: the unpublished
Keeley, J.E. 1981. Reproductive cycles and ﬁre regimes. P. 231–277 journals of John Muir. University of Wisconsin Press, Madison.
in H. A. Mooney, T. M. Bonnicksen, N. L. Christensen, J. E. 459 p.
Lotan, and W.A. Reiners (tech. coords.), Proceedings—confer- Mueggler, W.F., and J.P. Blaisdell. 1951. Replacing wyethia with
ence on ﬁre regimes and ecosystem properties. USDA For. Serv. desirable forage species. Journal of Range Management 4:
Gen. Tech. Rep. WO-26. 594 p. 143–150.
Keeley, J. E., and P. H. Zedler. 1998. Evolution of life histories in Parker, Albert J. 1986. Persistence of lodgepole pine forests in the
Pinus. P. 219–250 in D. M. Richardson (ed.), Ecology and bio- central Sierra Nevada. Ecology 67:1560–1567.
geography of Pinus. Cambridge University Press, Boston. Parsons, D.J. 1978. Fire and fuel accumulation in a giant sequoia
527 p. forest. Journal of Forestry 76:104–105.
Keifer, M.B. 1991. Age structure and ﬁre disturbance in southern Parsons, D. J. 1981. The role of ﬁre management in maintaining
Sierra Nevada subalpine forests. Unpub. MS Thesis, University natural ecosystems. 1981 P. 469–488 in H. A. Mooney, T. M.
of Arizona. 111 p. Bonnicksen, N. L. Christensen, J. E. Lotan, and W. A. Reiners
Kilgore, B.M. 1971. The role of ﬁre in managing red ﬁr forests. (tech. coords.), Proceedings conference fire regimes and
Transactions North American wildlife and natural resources ecosystem properties. USDA For. Serv. Gen. Tech. Rep. WO-26.
conference 36:405–416. 594.
Kilgore, B. M. 1972. Fire’s role in a sequoia forest. Naturalist Parsons, D.J. 1994. Objects or ecosystems: giant sequoia man-
23:26–37. agement in national parks. P. 109–115 in P. S. Aune (tech.
Kilgore, B. M. 1973. The ecological role of ﬁre in Sierran conifer coord.), Proceedings—symposium on giant sequoias: their
forests: its application to national park management. Quart- place in ecosystem and society. USDA For. Serv. Gen. Tech. Rep.
nary Research 3:496–513. PSW-151. 170 p.
292 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S
Parsons, D.J., and S.H. deBennedetti. 1979. Impact of ﬁre sup- Stephenson, N. L. 1998. Actual evapotranspiration and deficit:
pression on a mixed-conifer forest. Forest Ecology and Man- biologically meaningful correlates of vegetation distribu-
agement 2:21–33. tion across spatial scales. Journal of Biogeography 25:
Payson, T.E., and M.G. Narog. 1993. Tree mortality 6 years after 855–870.
burning a thinned Quercus chrysolepis stand. Canadian Journal Stephenson, N.L. 1999. Reference conditions for giant sequoia
of Forest Research 23:2236–2241. forest restoration: structure, process and precision. Ecol. Appl.
Piirto, D. D. 1994. Giant sequoia insect dsease, and ecosystem 9:1253–1265.
interactions. P. 82–89 in P. S. Aune (tech. coord.), Proceed- Stephenson, N.L., D.J. Parsons, and T.W. Swetnam. 1991. Restor-
ings—symposium on giant sequoias: their place in ecosys- ing natural ﬁre to the sequoia–mixed conifer forest: should
tem and society. USDA For. Serv. Gen. Tech. Rep. PSW-151. intense ﬁre play a role? Proceedings Tall Timbers Fire Ecology
170 p. Conference 17:321–337.
Pitcher, D.C. 1987. Fire history and age structure of red ﬁr forests Sudworth, G.B. 1900. Stanislaus and Lake Tahoe Forest Reserves,
of Sequoia National Park, California. Canadian Journal of Forest California, and adjacent territory. In annual reports of the
Research 17:582–587. Department of Interior, 21st annual report of the U.S. Geo-
Plumb, T.R. 1980. Response of oaks to ﬁre. P. 202–215 in T. R. logical Survey, part 5, 505–561.
Plumb (tech. coord.), Proceedings of symposium on ecological Sudworth, G. B. 1908. Forest trees of the Paciﬁc Slope. USDA
management and utilization of California Oaks. USDA Forest Government Printing Ofﬁce, Washington, DC. 441 p.
Service, PSW-GTR-44: 202–215. 368 p. Swetnam, T.W. 1993. Fire history and climate change in giant
Potter, D.A. 1998. Forested communities of the upper montane sequoia groves. Science 262:885–889.
in the central and southern Sierra Nevada. USDA For. Serv. Tappeiner, J.C., T.B. Harrington, and J.D. Walstad.1984. Predict-
Gen. Tech. Rep. PSW-169. 319 p. ing recovery of tanoak (Lithocarpus densiﬂorus) and paciﬁc
Rundel, P. W., G. A. Baker, and D. J. Parsons. 1981. Productivity madrone (Arbutus menziesii) after cutting or burning. Weed Sci-
and nutritional response of Chamaebatia foliolosa (Rosaceae) to ence 32:413–417.
seasonal burning. P. 191–196 in N. S. Margaris and H. A. Taylor, A. H. 2004. Identifying forest reference conditions on
Mooney (eds.), Components of productivity of mediter- early cut-over lands, Lake Tahoe basin, USA. Ecological Appli-
ranean-climate regions. Dr. W. Junk, The Hague, Netherlands. cations 14(6): 1903–1920.
279 p. Tomback, D.F. 1986. Post-ﬁre regeneration of krummholz white-
Rundel, P. W., and D. J. Parsons. 1979. Structural changes in bark pine: a consequence of nutcracker seed caching. Madrono
chamise (Adenostoma fasciculatum) along a ﬁre-induced age 33:100–110.
gradient. J. Range Manage. 32:462–466. Vale, T. R. 1987. Vegetation change and park purposes in the
Russell, W.H., J. McBride, and R. Rowntree. 1998. Revegetation high elevations of Yosemite National Park. Annals of the Assoc.
after four stand-replacing ﬁres in the Lake Tahoe Basin. American Geographer 77:1–18.
Madrono 45:40–46. Vale, T.R. 2002. Fire, native peoples, and the natural landscape.
St. John, T.V., and P.W. Rundel. 1976. The role of ﬁre as a min- Island Press, Washington, DC. 238 p.
eralizing agent in a Sierran coniferous forest. Oecologia Vankat, J. L. 1985. General patterns of lightning ignitions in
25:35–45. Sequoia National Park, California. P. 408–411 in J. E. Lotan,
Schweickert, R.A. 1981. Tectonic evolution of the Sierra Nevada B.M. Kilgore, W.C. Fischer, and R.W. Mutch (tech. coords.),
range. P. 87–131 in W.G. Ernst (ed.), The geotectonic devel- Proceedings—symposium and workshop on wilderness ﬁre.
opment of California, Rubey Vol 1. Prentice-Hall, Englewood USDA For. Serv. Gen. Tech. Rep. INT-182. 434 p.
Cliffs, NJ. 706 p. Vankat, J.L., and J. Major. 1987. Vegetation changes in Sequoia
Show, S.B., and E. I. Kotok. 1923. Forest ﬁres in California. USDS National Park. Journal of Biogeography 5:377–402.
Cir 243. 80 p. van Wagtendonk, J. W. 1985. Fire suppression effects on fuels and
Skinner, C.N., and C. Chang. 1996. Fire regimes, past and pres- succession in short-ﬁre-return interval wilderness ecosystems.
ent. In: Sierra Nevada Ecosystem Project: Final report to Con- P. 119–126 in J. E. Lotan, B.M. Kilgore, W.C. Fischer, and R.W.
gress, Volume II, Chapter 38. University of California, Davis, Mutch (tech. coords.), Proceedings—symposium and work-
Wildland Resources Center Rep. 37. 1528 p. shop on wilderness ﬁre. USDA Forest. Serv. Gen. Tech. Rep.
Smith, S.J., and R.S. Anderson. 1992. Late Wisconsin paleoeco- INT-182. 434 p.
logic record from Swamp Lake, Yosemite National Park, Cali- van Wagtendonk, J.W. 1986. The role of ﬁre in the Yosemite
fornia. Quaternary Research 38:91–102. Wilderness. P. 2–9 in Proceedings national wilderness research
Stephens, S. L. 2001. Fire history of adjacent Jeffrey pine and conference: currentresearch USDA For. Serv. Gen. Tech. Rep.
upper Montane forests in the eastern Sierra Nevada. Interna- INT-212. 553 p.
tional Journal of Wildland Fire 10:161–167. van Wagtendonk, J. W. 1991a. Spatial analysis of lightning strikes
Stephens, S. L., F. A. Finney, and H. Schantz, H. 2004. Bulk den- in Yosemite National Park. Proceedings 11th conference on ﬁre
sity and fuel loads of ponderosa pine and white ﬁr forest and forest meteorology 11:605–611.
floors: impacts of leaf morphology. Northwest Science van Wagtendonk, J. W. 1991b. The evolution of National Park
78:93–100. Service ﬁre policy. Fire Management Notes 52:10–15.
Stephenson, N. L.1994. Long-term dynamics of giant sequoia van Wagtendonk, J. W. 1994. Spatial patterns of lightning strikes
populations: implications for managing a pioneer species. P. and ﬁres in Yosemite National Park. Proceedings 12th confer-
56–63 in P. S. Aune (tech. coord.), Proceedings symposium on ence on ﬁre and forest meteorology 12:223–231.
giant sequoias: their place in ecosystem and society. USDA For. van Wagtendonk, J.W. 1995. Large ﬁres in wilderness areas. P.
Serv. Gen. Tech. Rep. PSW-151. 170 p. 113–116 in J.K. Brown, R.W. Mutch, C.W. Spoon, and R.H.
S I E R R A N E VA D A B I O R E G I O N 293
Wakimoto (tech. coords.), Proceedings—symposium on ﬁre in USDA, For. Serv. Paciﬁc Southwest Forest and Range Exp. Sta.
wilderness and park management. USDA Forest Service Gen. Misc. Pap. 60. 11 p.
Tech. Rep. INT-GTR 320. 283 p. Wagener, W. W. 1961b. Past ﬁre incidence in Sierra Nevada
van Wagtendonk, J.W., J.M. Benedict, and W.M. Sydoriak. 1998. forests. Journal of Forestry 59:739–748.
Fuel bed characteristics of Sierra Nevada conifers. Western Weatherspoon, C.P. 1986. Silvics of giant sequoia. P. 4–10 in C.
Journal of Applied Forestry 13:73–84. P. Weatherspooon, Y.R. Iwamoto, and D. Piirto (tech. coords.),
van Wagtendonk, J. W., and D. Cayan. 2007. Temporal and Proceedings of the workshop on management of giant sequoia,
spatial distribution of lightning strikes in California in rela- Reedly, California. USDA Forest Service, PSW Research Station
tionship to large-scale weather patterns. Fire Ecology (in PSW-GTR-9. 170 p.
Press). Wright, E. 1931. The effect of high temperatures on seed germi-
van Wagtendonk, J.W., K.A. van Wagtendonk, J. B. Meyer, and nation. Journal of Forestry 29:679–687.
K.J. Paintner. 2002. The use of geographic information for ﬁre York, D. 1997. A ﬁre ecology study of a Sierra Nevada foothill
management planning in Yosemite National Park. The George basaltic mesa grassland. Madrono 44:374–383.
Wright Forum 19(1): 19–39. Young, J.A., R.A. Evans. 1978. Population dynamics after wild-
Wagener, W.W. 1961a. Guidelines for estimating the survival of ﬁres in sagebrush grasslands. Journal of Range Management
ﬁre-damaged trees in California. Misc. Paper 60. Berkeley, CA: 31:283–289.
294 F I R E I N C A L I F O R N I A’ S B I O R E G I O N S