fire history from tree rings. justification: wildfires in montana and idaho …
TRANSCRIPT
Fire History from Tree RingsFire History from Tree Rings
Justification: Wildfires in Montana and Idaho …
Justification: Wildfires in Florida and Georgia …
Justification: Wildfires in California …
Justification: Wildfires in Arizona …
Justification: Wildfires in Arizona …
Fire exclusion – the most successful ad campaign ever…
Low severity wildfires …
… versus high severity wildfires.
The fire-scar record from tree rings.
Southwestern white pine and ponderosa pine, Mt. Graham, Arizona
ponderosa pine, El Malpais National Monument, New Mexico
The fire-scar record from tree rings.
Giant sequoia stump, Sequoia National Park, California
The fire-scar record from tree rings.
Table Mountain pine snag, Brush Mountain, Virginia
The fire-scar record from tree rings.
Catface on Table Mountain pine log, Reddish Knob, Virginia
The fire-scar record from tree rings.
Fire scars on freshly-cut Table Mountain pine, Brush Mountain, Virginia
The fire-scar record from tree rings.
Fire scars on ponderosa pine, El Malpais National Monument, New Mexico
The fire-scar record from tree rings.
Fire scars on sugar pine, Sequoia National Park,
California
The fire-scar record from tree rings.
Fire scars on giant sequoia, Sequoia National Park, California
Seasonality of past fires from tree rings.
Fire scar on southwestern white
pine, Mt. Graham, Arizona
Seasonality of past fires from tree rings.
Detail of fire scar on ponderosa pine, El Malpais National Monument, New Mexico
Fire regimes:• Fire frequency: how often
• Mean Fire Return Interval, Weibull Median Probability Interval
• Fire seasonality: when fires occur throughout the year
• Early season versus late season
• Fire severity: effects on forests
• Age structure, stand composition, stand structure
• Fire extent: spatial aspects
• Patchy fires versus landscape level fires
• Fire variability: changes in fire over time and space
• Climatic or human-driven?
Interpreting Fire History Charts
Years on x-axis
Period of Reliability: 1896 to 1944
Each line = 1 tree Sample IDs
Composite axis
Solid lines = recorder years
Each tic = fire scar
Dash lines = non-recorder years
Begin/end symbology
Temporal
Spatial
The Fire Chart
The Fire Chart
The Fire Chart
The Fire Chart
• Standard 50 x 20 m plot but greater spatial coverageis available using numerous smaller circular plots
• Inventory all tree species, measure dbh• Core, crossdate/age all trees ≥ 5 cm dbh• Inventory all saplings < 5 cm dbh,
> 50 cm ht• Inventory seedlings in 10 x 20 m
subplot• Collect sections from 20 mountain
laurel stems• Measure depth to mineral soil at
20 random locations
Pines Oaks
Mountain Otherlaurel hardwoods
20 m
50 m
Stand Age, Structure, and Composition
Brush Mountain Fire History
Period of Reliability: 1758–1934
All fires:
MEI: 3 yrs; LEI: 1 yr; UEI: 8 yrs
Widespread fires:
MEI: 8 yrs; LEI: 2 yrs; UEI: 19 yrs
90% early, 10% late season
Cohort establishment with surviving trees, then little fire for 30 years = possible moderate severity fire in 1853
Cohort establishment with surviving trees, then little fire for 30 years = possible moderate severity fire in 1853
Fires abruptly terminate after the 1926 and 1932 fires with establishment of the Jefferson National Forest in 1934.
Fires abruptly terminate after the 1926 and 1932 fires with establishment of the Jefferson National Forest in 1934.
Gold Mine Trail Fire HistoryPeriod of Reliability: 1850–1929All fires: MEI: 2 yrs; LEI: 1 yr; UEI: 4 yrsWidespread fires:MEI: 5 yrs; LEI: 2 yrs; UEI: 9 yrs60% early, 40% late season
Oak and yellow pine decline, replacement by fire intolerant species: eastern white pine, eastern hemlock, red maple
Oak and yellow pine decline, replacement by fire intolerant species: eastern white pine, eastern hemlock, red maple
Fires abruptly terminate after the 1929 fire with establishment of Great Smoky Mountains National Park in 1934.
Fires abruptly terminate after the 1929 fire with establishment of Great Smoky Mountains National Park in 1934.
All Sites, 1825–1934All fires:WMPI = 2 yrs, range 1 to 3 yrsWidespread fires:WMPI = 8 yrs, range 2 to 17 yrsSeasonality:73% dormant, early season
All Sites, 1935–2006All fires:WMPI = 4 yrs, range 1 to 6 yrsWidespread fires:No area wide fires post 1934Seasonality:50% dormant, early season
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Basically, tree-ring based fire history studies can be performed in nearly all
forested temperate environments, even in subtropical environments and at higher
elevations (despite fire being uncommon).
BYR
NNK
Big Pine Key
No Name Key
MFI WMPI Range SDBPK (n = 36) All scarred> 10%> 25%
NNK (n = 32)All scarred> 10%> 25%
6.556.868.47
9.799.79
10.94
5.836.157.91
9.149.14
10.32
2–262–262–26
2–242–242–24
4.684.754.88
5.565.565.91
MFI = mean fire interval; WMPI = Weibull median probability interval; SD = standard deviation
Analyzing the Climate/Wildfire Relationship:
• Done using Superposed Epoch Analysis
• Originally developed to study the preconditioning controls of natural events. Examples?
• First “stacks” all fire events one on top of the other.
• Then takes climate prior to, during, and after fire events, averages them together. For example: 5 years before event, the event year itself, and then 5 years after = 11 year window.
• Where does climate information come from before climate records were kept?
• Then uses bootstrapping methods to develop robust confidence intervals to determine which years in the window of years are statistically significant.
• The years after the event have nothing to do with the fire event itself, but help establish if a pattern exists in climate.
Superposed Epoch Analysis
Superposed Epoch Analysis
Changing fire regimes?• Relationship between drought and fire activity deteriorates between 1775 and 1825
during major climate transition in the Southwest.
Changing fire seasonality?• Related to climate change!
• Late season monsoon was non-existent prior to 1800 allowing July and August fires.
• After 1800, monsoon kicks in, shifting fires to earlier in the season.
Synthesis!