FIRE CASE STUDIES
SPECIES: Sequoia sempervirens | Redwood 



CASE NAME : 
Prescribed underburning in young-growth redwood forests.


REFERENCES : 
Finney, M. A. 1991 [14]
Finney, M. A.; Martin, R. E. 1991 [16]


SEASON/SEVERITY CLASSIFICATION : 
May     1989  Low consumption burn
June    1990  Low consumption burn
October 1989  High consumption burn


STUDY LOCATION : 
The study took place in two of California's state parks, Annadel State
Park and Humboldt Redwoods State Park.  Each area had 16 plots.  Annadel
State Park is located approximately 5 kilometers (3 mi) east of Santa
Rosa, California.  The cordinates are 38 degrees 25 minutes North
latitude, 122 degrees 35 minutes West longitude, and the legal
description is T7N R7W SW1/4 of section 25.

Humboldt State Park is located approximately 320 kilometers (192 mi)
north of Annadel State Park near Weott, California.  The coordinates are
39 degrees 16 minutes North latitude, 123 degrees 45 minutes West
longitude, and the legal description is T1S R2E S1/2 NW1/4 of section
20.


PREFIRE VEGETATIVE COMMUNITY : 
At the Annadel site the forest was young growth with diameters between 5
and 40 centimeters (2-16 in).  The age of the stand was between 120 and
140 years.  Evidence on the site suggests that the stand developed from
sprouts after fire exclusion in brush fields began in the mid-1800s.
The fire regime in the area prior to exclusion was every 2 to 6 years.

The Humboldt site was also a young growth forest with diameters between
5 and 40 centimeters (2-16 in).  This stand developed from natural
regeneration after logging approximately 60 to 80 years prior to the
study.  The past fire regime in the Humboldt area was every 5 to 25
years. 


TARGET SPECIES PHENOLOGICAL STATE : 
The prescribed burns took place when the trees were actively growing;
the burn in October occurred at the onset of seed dispersal.


SITE DESCRIPTION : 
On the Annadel site the plots were located on a northern aspect with a
slopes ranging from 30 to 40 percent.  The elevation of the plots ranged
from 240 to 350 meters (792-1,155 ft).

On the Humboldt site the plots were located on a southern exposure with
slopes ranging from 10 to 40 percent.  The elevation of the plots ranged
from 350 to 450 meters (1,155-1,485 ft). 


FIRE DESCRIPTION : 
To achieve different burn severities on the plots a variety of firing
techniques were used.  To achieve low fireline intensities, backing and
flanking fires were used, and to obtain higher fireline intensities,
strip head fires were used, with the strips ranging from 3 to 6 meters
(10-20 ft) wide to regulate fuel availability and build-up of fireline
intensity.

On the Annadel site, two plots were burned on May 17, 1989; one plot on
May 25, 1989; five plots were burned on May 30, 1989; and 8 plots were
burned on October 17, 1989.  Conditions were as follows:

                        Annadel Site

Date          Air           Rel.       Wind
              Temp.         Humd.      Speed
              (C)           (%)        (m/s)
 
5/17/89       16-18         55-70       0-2.2
5/25/89       18            38-45       0-1.3
5/30/89       18-21         40-45       0-2.2
10/17/89      17-24         35-52       0

On the Humboldt site, seven plots were burned on October 10, 1989; one
plot was burned on October 11, 1989; and eight plots were burned on June
27, 1990.  Conditions were as follows:

                         Humboldt Site

Date          Air           Rel.        Wind
              Temp.         Humd.       Speed
              (C)           (%)         (m/s)

10/10/89      13-24         48-75       0-2.4
10/11/89      16-22         60-72       0-1.3
6/27/90       20            56          0-1.3

For more specific information on burn conditions and ingition pattern
for each of the 16 plots on the two sites, see Finney 1990.

The fuel loading on both sites ranged from 29 to 55 tonnes per hectare
(32-61 tn/a) of litter and duff.  The small woody fuels (0-7.62 cm in
diameter) ranged from 9 to 20 tonnes per hectare with the large woody
fuels (> 7.62 cm) being highly variable.

The flame length ranged from 0.27 to 2.07 meters (0.9-6.8 ft) which
relates to a fireline intensity of 40 to 1833 kilowatts per meter
second.   

The fuel consumption varied from 15 to 68 tonnes per hectare.  The
percentage of fuel consumed ranged from 23 to 100 percent.  Fuel
consumption was found to be positively related to fuel loading.

Finney provides in-depth information on these parameters.


FIRE EFFECTS ON TARGET SPECIES : 
Most redwoods greater than 15 to 20 centimeters d.b.h. survived the most
severe prescribed fire with 100 percent surface fuel consumption and 100
percent crown scorch.

Redwoods originating from stump sprouts after logging were found to have
higher rates of top-kill than those originating from seedlings.  This
was linked to higher fuel concentrations (2 to 5 times that between
clumps), the stump, and heat convection currents drafting inward and
around the circular clump of trees.

As redwoods achieve greater d.b.h. the probability of top-kill
decreases.


FIRE MANAGEMENT IMPLICATIONS : 
Flame length and fuel consumption were found to be the most important
parameters in determining top-kill and basal sprouting.  These
parameters can be easily controlled by use of different firing patterns
and fuel moisture to achieve the desired effects from a prescribed fire.

A regime of periodic prescribed fire would elevate the probability of
sprout regeneration being top-killed by preventing large fuel
accumulations. 

Related categories for Species: Sequoia sempervirens | Redwood