Fire History and Dendrochronology
Photo by Daniel Heffernan
Photo by P. M. Brown
Agenda: April Fool’s Day 2011
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Notes on burn plans
Fire history lecture
Break
Lab
Done
Credits- Debra Kennard,
Laboratory of Tree Ring
Research, H. D. Grissino’s
Ultimate Tree Ring webiste
How do we
know what
the “natural”
or historical
fire regime
is for a
given
ecosystem?
Fire history
Fire history is the study of the chronology of
fire events over time, providing detailed
information about a forest’s historical fire
regime
Why is determining historical fire regimes
important?
• Provides a benchmark by which we can measure
change (e.g. estimating the effects of past fire
exclusion helps us predict the future)
• Can serve as a guide for determining appropriate
burn intervals for management plans
• Informs designation of desired future conditions,
or references for restoration
Fire regime classification
•
The fire regime is a useful concept because it brings
a degree of order to a complicated body of
knowledge.
– Allows for comparisons amongst sites and over time
•
The science of classifying fire regimes is young
(started ~1970s).
•
There are many ways to define a fire regime; not all
systems are consistent with each other.
•
Descriptions of fire regimes are very general
because of fire’s variability over time and space.
From Fire Effects on Flora (Brown and Smith 2000).
Fire Regime Condition Classes (FRCC)
Class
Challenge:
Use what you
know (fire
behavior,
fuels, plant
ecology) to
infer the fire
regime of this
forest
How do
we
determine
the details
of a
historical
fire regime
?
Gleaning Fire History Information
• Historical records or folklore (natives, explorers,
settlers)
• Photographs, remote sensing
– Chronosequence (e.g. LANDSAT)
• Paleoecological: Analyzing stratified lake or
bog/soil sediments for charcoal; pollen analysis
• Vegetation or stand age class distributions
(increment cores)
• Tree ring records
– Dendrochronology
Dendrochonology for Fire History
• Fires that damage cambium
leave a “fire scar”
• Fire occurrence is determined
by estimating the year of fires
based on tree rings and location
fire scars.
• Can also be used to determine
fire intensity, fire seasonality,
extent, and associated climatic
patterns.
• Takes advantage of variability in
annual growth rings (complacent
vs. sensitive species)
•
A close-up 
photograph of an
individual tree ring
showing the
earlywood (larger
cells) and latewood
(smaller cells), as
well as a resin duct
(growth is from
bottom to top)
(photo © LTRR).
A diagram showing the tree rings of a
"ring porous" tree species, such as oak
(Quercus spp.) and elm (Ulmus spp.)
(growth is to the right) (photo © LTRR).
Close-up photographs of conifer tree
rings showing different types and
rates of tree growth (photo © LTRR).
Fire-scarred incense cedar
(Calocedrus decurrens) in
Yosemite National Park, CA
Fire-scarred ponderosa pine tree
(Pinus ponderosa) in the Santa
Catalina Mountains north of
Tucson, Arizona
(photo © H.D. Grissino-Mayer).
Seasonality- longleaf pine scar
• Sample form
Henri
GrissinoMayer, Lake
Louise, GA
What if the tree is dead?
Increment cores taken from Douglas-fir (Pseudotsuga menziesii) trees growing on Mt.
Graham in southeastern Arizona (photo © H.D. Grissino-Mayer).
Cross-Dating
• Matching of ring width patterns between specimens used to
identify the exact year in which a ring was formed
• Useful when no known date is available; ring width patterns in
a dead wood sample can be “overlapped” on (live) samples
with known dates
• Accounts for tree ring anomalies
• Extends fire histories back into the past, much further than
even the oldest living tree
But trees grow at different rates,
even in the same stand!
• Skeleton Plotting: accounts for the fact “trees in a homogenous
stand or forest usually exhibit the same relative pattern of growth
variation through time, BUT
• Often have absolute growth rates that differ substantially due to living in
different microsites” (Laboratory of Tree Ring Research, T. Veblen, AZ)
Skeleton Plotting
General Procedures
• Mark relatively narrow rings on graph paper– the
narrower the ring, the taller the line
• Match these patterns between samples
• Account for missing or false rings
• Date your sample
• Identify fire years
• Create Master Fire Chronology
Group 1
Group 2
Example of Master Fire Chronology for ponderosa/Doug-fir forests of Boulder, CO
Example application of fire history
studies: climate relationships
• PIPO Fire history reconstructions show that fires
correlated with climate oscillations—wet/dry
Niño3 SST (ENSO)
A. SW
Annual
Precip.
Superposed Epoch
Analysis
(SEA) of fire years
at Archuleta Mesa
SOI (ENSO)
B. Four
Corners
Drought
Index
(PDSI)
(Brown and Wu 2005)
Limitations of tree-ring analysis
for fire history
• Cannot be used in areas
without trees, or where trees
are killed by fire (Pinyonjuniper woodlands, sand pine
scrub)- it will only provide date
of last fire
• Conservative estimate: Fire
scars may be healed-over,
some trees might not record a
given fire
• A large number of samples is
required for cross-dating
• Sampling is destructive
Set of fire scars shown in a section taken from a sugar
pine (Pinus lambertiana) growing in California (photo ©
A.C. Caprio).
Limitations, challenges, cont.
• The record gets worse the further back in
time you go
Percent of Trees Scarred
(%)
Number of Trees
120
100
80
60
40
20
0
1813
1865
1913
1946
% Trees scarred
No. of trees
1986
• And the larger the area sampled, the greater
number of scars you’ll find (for a while)
Results depend on the factors that
influence fire behavior– where & how you
sample matters!
Fire and Lightning Scars Across Topography
80
70
60
50
40
30
Fire Scars
Lightning Scars
20
10
0
Ravine
Hilltop
Knoll
Lower
Slope
Mid Slope
Upper
Slope
Ridgetop
• …and does that mean that fires occurred there more
frequently, or scarred trees there more often?
Some trees scar more easily than others…
60
No. Scars
50
40
PSME
30
PIPO
20
10
0
N
E
S
W
…and evidence may be better
preserved in certain microenvironments
Despite these limitations,
fire history data is widely used to
characterize fire regimes, and provides
the basis for many management
frameworks.
Additional Applications of
Dendrochronology
• Ecology: insect outbreaks, forest
demographics and growth patterns
• Climatology: past droughts or cold periods
• Geology: past earthquakes, volcanic
eruptions
• Anthropology: past construction, habitation,
and abandonment of societies
• More at the Laboratory of Tree Ring
Research, AZ
What you will do
• Lab Exercise individually
• Hand-in by end of class
• Extra Credit-- Go to:
http://www.ltrr.arizona.edu/skeletonplot/Sk
eletonPlot19.htm (review the tutorial)
• Do the Crossdating: Skeleton Plot for
Yourself exercise
CBI- class results 3/25/11