CHAPTER 12



                      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.
                                                1895
                                         JOHN MUIR,




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
Physical Geography
                                   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.



264
              R.
            er
           ath
          Fe

                .
                R
             ba       Blue Canyon
           Yu                    Lake Tahoe
                  R.
                can
              eri
             Am




                          .
                        ne R         Sonora Pass
                       lum
                     ke
                   Mo
                                      Yosemite NP


                          lu m n e R .
                        uo         Yosemite Valley
                      T




                           Merced R.




                                                Sequoia/Kings Canyon NP

                                                Mount Whitney




                                              .
                                            R
                                          rn
                                         Ke
N




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
Climatic Patterns
                                     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
Pass.
                                  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
                                  Ecological Zones
during October.
                                  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
gion).
                                     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
Post-frontal

Great Basin High             16.1  12.0  11.3   11.0    7.4   6.1    12.3    18.7    15.7      16.1
(Pacific)

Subtropical                0.0  0.0   0.0   10.3   32.3   24.8    16.3     1.6    0.0       0.0
High Aloft

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
                                                   elevation increases.




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
complexes.
                                  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
Prehistoric Period
                                 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
Smith 1997).
                                 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
                                 Historic Period
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
                                  microclimate.
extreme weather conditions they were unable to control the
large ones.
                                  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
relatively clear.




                                  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
                         (seed release)

  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
                                               mountain-mahogany,
                                               redshank, yerba santa,
                                               California coffeeberry,
                                               Christmas berry
              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,
                                               mariposa lilies
              None         None

  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

           Vegetation type
                                   Chaparral       Oak woodlands/       Conifer forest
                                              grasslands         patches

           Temporal
            Seasonality                 Summer–fall      Summer–fall        Summer–fall
            Fire-return interval             Medium        Short           Medium

           Spatial
            Size                     Large         Large           Small
            Complexity                  Low          Low            Low

           Magnitude
            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.
             NOTE:




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
                                        often dominate.
                                         Throughout the zone, riparian plant communities char-
Lower-Montane Forest
                                        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
                                          when young

                 None           None          Low resistance,   Pacific yew
                                          killed

  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,
                                                    hazelnut, willow

                 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-
           2
             (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
the environment.
 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

       Vegetation type
                              Ponderosa pine/     Douglas-fir/      Tanoak-mixed
                              black oak        white fir        evergreen

       Temporal
        Seasonality                Summer–fall       Summer–fall      Summer-fall
        Fire-return interval            Short (regular)     Short (variable)    Medium (variable)

       Spatial
        Size                    Large          Large         Medium
        Complexity                 Low           Multiple        Multiple

       Magnitude
        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.
        NOTE:




                                                     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
                                  deBennedetti 1979).
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
                                                   areas.




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.
Upper-Montane Forest
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
                                                           manzanita

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
DeByle 1987).
                                          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)
burned.
                                          (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

       Vegetation type
                           Red fir            Jeffrey pine,        Tufted hairgrass
                                          western white pine,
                                          mountain juniper

       Temporal
        Seasonality              Late summer–fall       Summer–fall         Late summer–fall
        Fire-return interval          Medium            Medium           Long

       Spatial
        Size                  Medium            Truncated small       Small
        Complexity               Multiple           Low             Low

       Magnitude
       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.
        NOTE:




                                      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
                                      Subalpine Forest
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
                                  released seed.
                                    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,
                                                         foxtail 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

        Vegetation type
                               Lodgepole pine        Mountain        Whitebark pine,
                                              hemlock        limber pine,
                                                         foxtail pine

        Temporal
         Seasonality                 Late summer–fall       Late summer–fall    Late summer–fall
         Fire-return interval            Long             Long          Truncated long

        Spatial
         Size                    Small            Small         Small
         Complexity                 Low             Low          Low

        Magnitude
         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.
          NOTE:




(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-
                                  Sierra Nevada.
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,
intensity fires.
                                  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
                                                mortality.




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
                                                            cottonwood, willow

Shrub              Fire stimulated       None            Top-killed          Bush chinquapin, greenleaf
                                                            manzanita, huckleberry oak,
                                                            snowberry, willow,
                                                            bitterbrusha

                Fire stimulated       Fire stimulated       Top-killed          Tobacco brush
                                                           Sagebrush, bitterbrusha
                None             None            Killed

Herb              Fire stimulated       None            Top-killed          Woolly mule’s ears
                None             None

Grass              Fire stimulated       None            Top-killed          Sedges
                                             Killed            Cheat grass

 a
   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

         Vegetation type
                                     Jeffrey pine,        White fir and     Chaparral
                                     ponderosa pine       mixed conifer

         Temporal
          Seasonality                     Summer–fall         Summer–fall     Summer–fall
          Fire-return interval                 Short            Medium        Medium

         Spatial
          Size                         Small–Medium         Medium        Medium
          Complexity                      Multiple           Multiple       Low

         Magnitude
          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.
           NOTE:




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.
Management Issues
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
ity considerations.
                                  and vegetation in the lower-elevation portions of the Sierra
                                  Nevada foothill and lower montane zones have resulted in
Urbanization
                                  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
Air Quality
                                   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
                                   Summary
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
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