ESPM 181: Fire History Labs: Fire-Scar Dendrochronology

1. ESPM 181:Fire History Labs:Fire-ScarDendrochronology 27 February & 6 March 2007 Powerpoint version (posted on the ‘readings’ page of the course website: this supersedes previous versions) Rick Everett Wildland Fire Lab, ESPM UC Berkeley everett@nature.berkeley.edu

2. Importance of Fire History • Helps us to understand fire regimes and systems so we can mimic process and manage in the contemporary environment • A “benchmark” - important base of information by which we can measure change • Remember that a fire history is a tool for making management decisions, not the solution

3. Sources of Fire History Information: • Fire scars • The most common technique (more below…) • Age class distributions • Use stand age data to reconstruct extent of past fires • Fit stand age data to a mathematical model & derive fire frequency characteristics • Paleoecological techniques • Examining charcoal and other elements in stratified soil sediments (e.g. lake cores, alluvium, mudslides, debris flows). • Pollen analysis, • Fossil records. • Historic records • Supplement other data. Helps evaluate both natural and cultural causes of variability in ecosystems. See Swetnam, et al. Applied Historical Ecology: Using the Past to Manage For the Future. Ecological Applications, 9(4). 1999. pp. 1189-1206. • Ethnographic accounts • Verbal Histories • Photographs and Remote Sensing • Can be used as a chronosequence for the period of record of the images • Detailed fire history for Chaparral developed by Minnich using LANDSAT for No. Baja and So. California.

4. Data Types • Point Frequency • How often fire is scarring a single individual, or a small group of geographically limited individuals (<0.1 ha) • Area Frequency • Larger groups of samples: • Stand level • Compartment • Landscape

5. Fire Scars as Records of Fire History • Fire Scars at base of tree (catface) created due to cambial injury and tree response – healing over

6. Value of Fire Scars: • Using dendrochronological techniques, we can accurately date fire events to their year of formation. • Sometimes we can date to the season of formation. • Important clues to characteristics of fire regimes – • fire return intervals, • fire seasonality, • range of ‘historical’ variability • Samples over large areas can lend clues to scale of fire events. • Dates of fire events for each sample recorded in a sample fire chronology. • Samples compiled into a master fire chronology. • Synchrony or asynchrony of fires can be seen in master fire chronology.

7. Limitations of Fire Scars as a source for Fire History • A conservative history • Captures low to moderate intensity fires. • High intensity fires trend towards stand replacement. • Fire history studies focus on external visual cues that a record is present: • Cat faces – i.e. visible fire scars. • Scars, can, and do, completely heal over – • These aren’t seen until processing • Disadvantage = destructive type sampling.

8. Dendrochronology and Dating Fire Scars • Dendrochronology definitions: • The study of chronological sequences and patterns of annual growth in rings (Stokes, 1968) • The science that uses tree rings dated to their exact year of formation to analyze temporal and spatial patterns of processes in the physical and cultural sciences. (Grissino-Mayer)

9. Selected Principles of Dendrochronology (Fritts, 1976) • Sensitivity • Variability in ring widths caused by limiting environmental factors • Complacency = lack of width variability • It is sensitivity in ring series that allow us to match patterns between samples • Cross Dating • Matching of ring patterns in one specimen with corresponding patterns in another (Stokes, 1968) • The procedure of matching ring width variations and other structural characteristics among trees that have grown in nearby areas, allowing the identification of the exact year in which each ring was formed (Argent, 1998)

10. Why not just count rings? • Tree ring anomalies: • Missing, locally absent, and micro rings (easily missed with increment coring) • False rings (often discerned by diffuse ring boundaries) • Inaccurate bark death date – cut date (less-than-optimal field info) • Inaccurate pith date (less-than-optimal field info) • Cross dating allows us to date samples for which we have no known date: • Bark Death Date (?) • Cut Date (?) • Pith Date (?) • Ring width patterns in remnant wood (from trees that died long ago) can be dated by matching ring patterns with dated samples (chronosequence). • Doing this, you can overlap trees, and extend the record forward or backward in time: • In this way we can extend our fire history back much farther than even the oldest living tree.

11. Sampling and Sample Preparation • Slab Sections • Minimum number of scars visible to obtain maximum amount of data • Usually try to obtain several samples in close proximity, and several groups across area • Trees at limits of their range or with limiting factors provide “sensitive” ring series • Use of systematic sampling increasing • What you cut you must carry out! • Preparation • Cut to size with band saw, mount • Sand surface to a polished finish

12. Cross Dating Procedures • Methods of Cross Dating (Argent, 1998) • Directly from wood - Professional expertise, local knowledge, "marker years" • Skeleton plotting - hand made tree ring "indices" for a sample/time series in which particularly narrow rings are marked as long lines. • Computer aided cross-dating (Densiometry)- Using ring widths scanned into a discretionary program (like WinDendro).

13. Skeleton Plot Basics: • General Procedure: • Mark arbitrary 10 year ring counts on sample and graph paper – inner ring = year 0. • Use “moving window” to find rings that are narrow relative to adjacent rings • Relatively narrow rings are marked on graph paper – narrow rings get proportionally taller lines. • Match ring patterns between two samples • Account for missing or false rings • With a known date on one sample, (such as formation of the last ring) other samples can be dated. • Create composite of individual sample plots • Compare composite skeleton plot or individual sample plots to established references (tree ring chronologies, climate data, etc.

14. For a detailed description of skeleton plotting techniques, see: Swetnam, Thomas W., Marna Ares Thompson, and Elaine Kennedy Sutherland. 1985. Spruce Budworm Handbook: Using Dendrochronology to Measure Radial Growth of Defoliated Trees. USDA Forest Service, Agriculture Handbook 639.

15. Lab targets for today: • Independently perform the skeleton plotting exercise • SIGN UP FOR A TIMESLOT FOR NEXT WEEKS LAB!!! • -Sign up sheet will remain on the door at 360 Mulford (0700-1700 daily) • Times: 1300-1700 Tuesday and Thursday, 06 and 08 March 2007 (additional hours depend on demand)

16. ESPM 181 Fire History Lab 2007 Assignment THIS WEEKS AND NEXT WEEKS LABS WILL BE COMBINED INTO 1 REPORT THIS WEEK: 1) Read through the first 11 portions "Crossdating Tree Rings Using Skeleton Plotting" located at: http://www.ltrr.arizona.edu/skeletonplot/introcrossdate.htm 2) The twelfth portion allows you to "Try skeleton plotting for yourself." This interactive web based program will give you some practice skeleton plotting. Your assignment: a. To get the hang of the program, try skeleton plotting several cores with the following settings: Sensitivity: 1 # Rings: 51 No false rings No absent rings Print out your one of your properly dated cores (turn in with your lab report). Be sure to show the answer and master chronology b. Now make things a bit more challenging. Date a core with the following settings: Sensitivity: 3 # Rings: 71 False rings possible No absent rings Print out your properly dated core (turn in with your lab report). Be sure to show the answer and master chronology. c. Step it up again. Date a core using the following settings: Sensitivity: 4 # Rings: 101 No false rings. Absent rings possible. Print out your properly dated core (turn in with your lab report). Be sure to show the answer and master chronology. 3) Now get close to the real thing. Choose 3 "Pseudo-bristlecone pine cores" from the handout. Skeleton plot each of these cores on a strip of graph paper. Once done, use the "Melthusian Walk Bristlecone Pine Master Chronology" to date your cores. This chronossequence is posted outside of 360 mulford on the bulletin boards, and is available for viewing from 0700 to 1800 weekdays. Once you have dated each core, mark the date of the first and last ring on your graph paper. Turn these in with your lab report. NEXT WEEK 4) Date an actual tree cross section, complete with fire scars. This and next weeks' exercises should be combined into one lab report, which will be worth double the normal amount of points. In your writeup, you should consider the following questions from today: a. Describe the process of skeleton plotting in your "methods" section. b. For the discussion section, What did you observe from each of the following exercises: - Web based skeleton plotting - Bristlecone pine activity - What are possible sources of error in any of these protocols? DUE: 13 March 2007