1. Fire History and Dendrochronology
Photo by Daniel Heffernan

2. Agenda: Last class of 2013  Notes on 4/26 Fire history lecture Break
Lab
Done!
Credits- Debra Kennard, Laboratory of Tree Ring Research, H. D. Grissino’s Ultimate Tree Ring website

3. The Importance of 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
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 3

4. Restoration- to what? Why?
These three ecosystems can all occur in the same place- at the same elevation, with the same climate drivers. But one thing differs amongst them- fire.
Why?

5. How do we know what the “natural” or historical fire regime is for a given ecosystem?

6. Fire Regime Attributes
Frequency
Severity
Area
Type
Intensity
Synergy

7. Distribution of ecosystems in S. Florida

8. From Fire Effects on Flora (Brown and Smith 2000).
A similar scenario used in the Rainbow series Fire Effects on Flora (Brown and Smith 2000).

9. How do we determine the attributes of a historical fire regime?

10. Gleaning Fire History Information
Depends on what is available:
Paleoecological: Analysis of stratified lake or bog/soil sediments for charcoal; pollen analysis

11. Gleaning Fire History Information
Historical records or folklore (natives, explorers, settlers)
Vegetation or stand age class distributions
Photographs, remote sensing: Chronosequence (e.g. LANDSAT)

12. Dendrochronology dendro: tree. chronology: study of time
“Dendrochronology examines events through time that are recorded in the tree‐ring structure or can be dated by tree rings.”
Speer, J Fundamentals of Tree‐Ring Research. The University of Arizona Press

14. 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
Fire history!

15. Dendrochonology for Fire History = Dendropyrochronology
Fires that damage cambium leave a 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)

20. 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).
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).
Close-up photographs of conifer tree rings showing different types and rates of tree growth (photo © LTRR).

22. What does dendropyrochronology tell you?
Frequency
Season
Areal extent?
Severity?
Years of fires?
Synergy with climate, other disturbances
Terms
Fire Return Interval: length of time between one fire and the next/previous fire
Mean FRI: avg. of above

25. Example application of fire history studies: climate relationships
PIPO Fire history reconstructions show that fires correlated with climate oscillations—wet/dry
Superposed Epoch Analysis (SEA) of fire years at Archuleta Mesa (Brown and Wu 2005)
Niño3 SST (ENSO)
A. SW Annual Precip.
SOI (ENSO)
B. Four Corners Drought Index
(PDSI)

26. Years of fires: Depends on knowing a date! Or does it?
Increment cores taken from Douglas-fir (Pseudotsuga menziesii) trees growing on Mt. Graham in southeastern Arizona (photo © H.D. Grissino-Mayer).

27. 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

28. 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)

30. 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

31. Group 1
Group 2
Example of Master Fire Chronology for ponderosa/Doug-fir forests of Boulder, CO

32. Limitations of tree-ring analysis for fire history
Cannot be used in areas without trees, or where trees are killed by fire (Pinyon-juniper 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).

33. Limitations, challenges, cont.
The record gets worse the further back in time you go
The next bunch of figures are from my MS work at Berkeley, done in the Front Range of Boulder Colorado in Ppine forests (Open Space and Mountain Parks)
And the larger the area sampled, the greater number of scars you’ll find (for a while)

34. Results depend on the factors that influence fire behavior– where & how you sample matters!
Y axis is percent of sites with fire scars (normalized for number of sites of particular topography searched)
…and does that mean that fires occurred there more frequently, or scarred trees there more often?

35. Some trees scar more easily than others…
…and evidence may be better preserved in certain microenvironments

36. Despite these limitations,
fire history data is widely used to characterize fire regimes, and provides the basis for many management frameworks.

37. Class Challenge:
Use what you know (fire behavior, fuels, plant ecology) to infer the fire regime of this forest

38. This is the Sierra San Pedro Martir in Baja CA around 6000’

41. What you will do Lab Exercise in pairs Hand-in by end of class
Have a look at the samples
Extra Credit-- Go to: (review the tutorial)
Do the Crossdating: Skeleton Plot for Yourself exercise