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Survival of Damaged
Singleleaf Pinyon One Year
After Wildfire 1
David R. Weise2
Pinyon-juniper woodland occupies 2.7 million acres in California
(Bolsinger 1980). Singleleaf pinyon
(Pinus monophylla Torr. & Frem.) is a
common species of this type. Approximately 160,000 acres (or 20%) of
the San Bernardino National Forest
(SBNF) in southern California is covered by singleleaf pinyon. The type is
heavily used for recreation on the
SBNF and needs to be maintained.
Most of the large fires in singleleaf
pinyon on the SBNF have been human-caused (Doherty, pers. comm.).
Prescribed fire may be a method to
maintain singleleaf pinyon stands by
reducing fire hazard or preparing
seedbeds (by reducing competition).
This use is a departure from traditional use of fire in this type which
has been eradicating the pinyon-juniper type throughout most of its range
to improve forage production for
livestock (Arnold et al. 1964, Wright
et al. 1979).
The major factor governing the
use of prescribed fire in singleleaf
pinyon is the species' ability to withstand the damaging effects of fire.
No information concerning survival
of singleleaf pinyon after fire was
found in the literature. One study
(Dwyer and Pieper 1967) reported
1Poster paper presented
at the conference. Effects of Rre in Management of
Southwestern Natural Resources (Tucson,
AZ, November 14-17, 1988).
2
Forester, Forest Rre Laboratory, Pacific
Southwest Forest and Range Experiment
Station. Forest Service, U.S. Department of
Agriculture, Riverside. CA.
13.5 percent mortality of common
pinyon (Pinus edulis Engelm.) 1 year
after a damaging wildfire. A pilot
study to document postfire survival
of singleleaf pinyon was established
on the SBNF in 1987. This paper reports first year results of the study.
Study Sites
Two wildfires occurred in pure
singleleaf pinyon stands on the SBNF
in 1987. One fire (Nelson), located at
7000 ft elevation, burned approximately 40 acres in early July. The
other (Jeep Trail) is located at 4800 ft
elevation and burned 1600 acres in
September. Both sites receive precipitation in the form of snow and
occasional summer thunderstorms.
The fuels adjacent to both wildfire
sites are similar-light, patchy
grasses and small, scattered brush.
The Jeep Trail site has some heavier
brush such as manzanita in scattered
areas, primarily on lower slopes
along intermittent drainages.
Methods
A total of 244 trees were tagged
and measured at the study sites in
October 1987. Trees were assumed to
be living at the time of the wildfires.
Diameter at breast height (dbh), total
height, and crown damage class were
assessed for each tree (table 1). Time
constraints did not permit equal rep229
lication of all damage categories.
Control trees (damage category 1)
were located in unburned areas
within 50 ft of the wildfires' boundaries. The sites were revisited in September 1988 and survival of each tree
was assessed. Trees were placed into
l-inch dbh classes. Survival by dbh
class and damage category was summarized by individual site.
Results
Tree size differed considerably between the two sites: trees sel~cted at
Nelson were smaller (table 2). The
two sites differed greatly in first year
postfire survival (table 3). A greater
percentage of trees were still alive at
the Nelson site. Survival does not
appear to be a function of only dbh
class (table 3)-the 24 inch tree that
died at Jeep Trail was a damage category 2 tree.
Similarly, postfire survival differed by damage category at each
location (table 4). All trees in categories 1 and 2, and 96% of trees in categories 1, 2, and 3 survived at Nelson.
In contrast, only 36% of the trees in
categories 1 and 2, and 28% of trees
in categories 1, 2, and 3 survived at
Jeep Trail. Twenty-five percent of the
category 1 trees at Jeep Trail died
during the first year. Survival response was similar at both sites in
damage categories 4-7. Only two of
the 158 trees in these categories survived.
Discussion
The differences in first year
postfire survival are of interest. Mortality of the undamaged and slightly
damaged trees appears to differ between the sites. Since fire behavior
on either fire is not adequately documented, determination of the factors
causing the difference may be difficult. This is often the case when
trying to link wildfire behavior to fire
effects.
Tree size does not appear to be a
factor in initial survival. However,
tree size may prove to be critical in
long term survival. Mortality of
Douglas-fir (Pseudotsuga menziesii
(Mirb.) Franco) and ponderosa pine
(Pinus ponderosa Dougl. ex Laws.)
nearly doubled between 10 and 22
months after a prescribed fire (Wyant
et al. 1986). Postfire mortality of
singleleaf pinyon may change considerably over the second year also.
Attributing mortality to only fire
damage may not be possible. Since
25% of the undamaged trees at Jeep
Trail died during the first year, other
factors may be contributing to mortality. The species is known for cold
hardiness (Hepting 1971), but the
interaction of fire damage with low
winter temperatures may have contributed to mortality. Singleleaf
pinyon may achieve longevity of 225
years and diameters of 12 inches are
unusual (Hepting 1971). The Jeep
Trail trees, with mean diameter of
approximately 12 inches, may have
reached maturity and trees have begun to die naturally. The fungus Verticicladiella wagenerii is also known to
occur on the SBNF. The factors of
age, cold, and root rot may have contributed to mortality of the undamaged trees.
A relationship between percent of
crown scorch and singleleaf pinyon
survival may exist. The species appears to be able to tolerate a small
portion of crown scorch resulting
from fire (less than 33 percent). It
230
may be possible to burn a stand with
a low intensity prescribed fire and
keep crown damage to a minimum.
Additional measurements planned
within the next year should clarify
this relationship.
Uterature Cited
Arnold, Joseph F.; Jameson, Donald
A.; Reid, Elbert H. 1964. The
pinyon-juniper type of Arizona:
effects of grazing, fire, and tree
control. Production Res. Rep. 84.
Washington, D.C.: U.S. Department of Agriculture, Forest Service. 28 p.
Bolsinger, Charles L. 1980. California
forests: trends, problems, and opportunities. Resource Bull. PNW80. Portland, OR: U.S. Department
of Agriculture, Forest Service, Pacific Northwest Forest and Range
Experiment Station. 138 p.
Doherty,~. 1988.Personalcommunication, Oct. 28, 1988- Fire ~an­
agement Officer, Arrowhead and
Big Bear Ranger Districts, San Bernardino National Forest.
Dwyer, Don D.; Pieper, Rex D. 1967.
Fire effects on blue grama-pinyonjuniper rangeland in New ~exico.
Journal of Range ~anagement
20(6):359-362.
Hepting, George H. 1971. Diseases of
forest and shade trees of the
United States. Agric. Handb. 386.
Washington, D.C.: U.S. Department of Agriculture, Forest Service. 658 p.
Wright, Henry A.; Neuenschwander,
Leon F.; Britton, Charles~- 1979.
The role and use of fire in sagebrush-grass and pinyon-juniper
plant communities: a state-of-theart review. Gen. Tech. Rep. INT58. Ogden, UT: U.S. Department
of Agriculture, Forest Service,
Intermountain Forest and Range
Experiment Station. 48 p.
Wyant, James G.; Omi, Philip N.;
Laven, R.D. 1986. Fire induced
tree mortality in a Colorado ponderosa pine/ Douglas-fir stand.
Forest Science. 32(1): 49-59.
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