FIRE CASE STUDIES
SPECIES: Sequoiadendron giganteum | Giant Sequoia 



CASE NAME : 
Impact of prescribed burning on a sequoia-mixed conifer forest


REFERENCE : 
Kilgore, B. M. 1973 [30]


SEASON/SEVERITY CLASSIFICATION : 
Fall burn / low- to moderate-severity


STUDY LOCATION : 
The study site was located on the ridge of Redwood Mountain which runs
north and south within the 3,100 acre Redwood Mountain Grove of giant
sequoias in Kings Canyon National Park, Three Rivers, California.


PREFIRE VEGETATIVE COMMUNITY : 
Giant sequoia, white fir, and sugar pine dominate the forest, with
incense-cedar, Pacific ponderosa pine, and California black oak well
represented except in the extreme southern plots.  Shrubs and herbs are
present, but rare, and grasses are almost absent.  Major shrub species
include Sierra mountain misery (Chamaebatia foliolosa) and Sierra
gooseberry (Ribes roezlii).  Graminoids include Carex spp.


TARGET SPECIES PHENOLOGICAL STATE : 
The target phenological states were not recorded.


SITE DESCRIPTION : 
The elevation along the ridge ranges from 6,400 feet (1,950 m) at the
saddle to nearly 7,000 feet (2,134 m).  Hygrothermograph records show a
yearly low of 17 degrees Fahrenheit (-8.4 deg C) and a high of 82
degrees Fahrenheit (28 deg C).  Temperatures in November just before the
burn ranged from 32 to 58 degrees Fahrenheit (0-15 deg C).  Relative
humidity fluctuated between 30 and 80 percent.  Winds in and near the
study plots were moderate when present, varying from 0 to 5 mph (0.3
kmh).  Average slope was 35 percent.  Large portions of this study area
were found on soils derived from metamorphic schists.

Burn day conditions were as follows:

        Temperature: 59 deg F (15 deg C)
        Humidity: 20 percent
        10-hour fuel sticks: 10 grams
        Wind speed: 0 mph



FIRE DESCRIPTION : 
Twelve 60- by 100-foot (18 x 30 m) study plots were laid out about 600
feet (183 m) east of the ridge of Redwood Mountains at an elevation of
6,300 feet (1,920 m).  Two additional plots were established just below
the saddle parking area as demonstration plots.  These were selected as
being represenative of the range of vegetative and fuel conditions on
this east-facing slope of the mountain.  Seven of the 12 plots and 1
demonstration plot were burned, while the remaining plots were retained
as controls.  For each plot, the following information was measured
before and after ignition:

1. Species, diameter, height class > 6 inches dbh (15 cm) or 4.5 feet
   (1.4 m) tall.
2. Number of white fir and sugar pine saplings per acre in four height
   classes.
3. Extent and approximate height of white fir sapling thickets.
4. Coverage and frequency values.
5. Litter and duff weights.
6. Length and diameter of down trees.
7. Chemical light meter indices for light reaching the forest floor.
8. Vegetation appearance recorded by black and white/color photographs
   from 102 permanent photo points.

After all pre-burn measurements were made, a 2-foot (0.6 m) wide
fire-line was built along the 2 sides and the bottom of the proposed
5-acre (2 ha) burn area.  The burning indices for the burn day were as
follows:
                     Forecast    Actual    Prescription (range)
                     --------    ------    --------------------
Fine Fuel Moisture      6          5              7-10
Spread Index            8          8              5-12
Intensity Index        59         56             37-49
Timber Burning Index    5          5              3-5
Ignition Index         45         55             15-49  

All test plots were ignited at 0900 by drip torch along the upper
boundary of the burn area.  A strip-head fire method of ignition was
used and it burned briskly from 0900 to 1200.



FIRE EFFECTS ON TARGET SPECIES : 
Ninty-four percent of the 210 2- by 3-foot (0.6 x 0.9 m) sample plots
showed evidence of fire impact.  Eighty percent burned almost
completely, while 14 percent burned partially or lightly.  Only 6
percent of the sample plots remained unburned.  Both before and after
the burn, about 55 percent of the trees more than 12 inches dbh were
white fir, while 29 percent were sequoia and only 8 percent were sugar
pine.  More than 84 percent of the trees in the 6 to 12 inch d.b.h class
were white fir, with the remainder being sugar pine.  About 38 percent
of this class was killed during the burn, but the proportion of white
fir to sugar pine remained nearly the same.

Essentially no tree seedlings of any species were found during the first
year following this November 1970 burn.  This is in sharp contrast with
the nearly 22,000 sequoia seedlings per acre found on a previous, more
intense August-September 1969 burn on the ridge itself.



FIRE MANAGEMENT IMPLICATIONS : 
This study investigated methods by which the impacts of prescribed fire
on certain biotic and abiotic elements of the sequoia-mixed conifer
forest ecosystem could be measured.  Giant sequoia was present as a
co-dominant species with an estimated 11.4 trees per acre (28.2/ha).  A 
comparison of results was detailed from previous high-severity 1969 burn
to the lower-severity 1970 burn reported here.  In summary, a high-severity
burn followed by another moderate-severity burn 7 to 10 years later is
an option for obtaining management objectives on a mixed sequoia stand;
or, alternatively, implement two low-severity burns in closer sequence
in order to gradually kill young seedlings and cleanup heavy fuels.
Both strategies would allow for more natural regeneration of seral species, 
while reducing the potential threat of hazardous wildfires. 

Related categories for Species: Sequoiadendron giganteum | Giant Sequoia