great moments in dendrochronology paul sheppard. forestry major humboldt state university,...
TRANSCRIPT
Great Momentsin
Dendrochronology
Paul Sheppard
Forestry Major
Humboldt State University, California
Forestry Major
• Tree identification
• Forest ecology/biogeography
• Silviculture
• Production
• Dendrochronology
Dendrochronology = tree-ring science
UA Tree Rings
Dating
Climate
Fire
Geology
Water
Chemistry
• Eternal question
– Why do you do what you do?
• Eternal question
– Why do you do what you do?
• Eternal answer
– Put modern times in context of deep past
• Eternal come back
– Yea, yea, but give examples!
– Great Moments in Dendro
Bridging the Gap
AndrewEllicott
Douglass
2014
1050
The Gap
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0 100 200 300 400 500
Floating Ruins Chronology
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1300 1400 1500 1600 1700 1800 1900
Dated Tree Chronology
Show Low
• Buried log
Universal Accolades
• “most valuable contribution ever made to American archaeology”
• “most important thing ... thus far in American prehistory”
• “your contribution … is singularly outstanding”
• “tree-ring approach has been the single greatest contribution ever made to American archaeology”
Bridging the Gap
• Interesting, hard problem
• Huge data set
– Thousands living trees, Sky Islands
– Hundreds beams, dead trees
• Took 20+ years of work
• Multidisciplinary
– Dendro, archaeo, geogr
• First great moment
Radiocarbon Date Check
14N
14C
14N
into plants, animals
they die half-life =5730 yrs
Obvious Experiment
• Try C14 dating of wood already dated by dendrochronology
• Should result in a 1:1 line in a scatter plot
• If not … ?
0
5
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25
0 5 10 15 20 25
C1
4 D
ate
Tree-Ring Date
• Irish oak: 9,000 years
• US bristlecone pine: 8,700 years
• German oak-pine: 12,500 years
6000 BC AD 2000
800 years!!!C14 vs dendro
of wood
Electromagnetic strength
Radiocarbon Date Check
• Interesting, hard problem
• Huge data set
– Hundreds of trees, living dead
• Took tens of years of work
• Multidisciplinary
– Dendro, phys, chem, astro
• Spectacular moment!
Colorado River
Colorado River Compact, 1922
• 4th from left?
• WY, CO, UT, NM – Upper Basin
• AZ, NV, CA – Lower Basin
• 7.5 maf for each basin per year
• Extra 1 maf for Lower Basin (CA)
• Total: 16 maf every year
Colorado River Compact
Colorado River Watershed
• Abundant, long-lived trees, Sky Islands
• Statistical relationship ring width and gauge record river flow
• Past 450 years:
– Average: 13.5 maf
– Range: 4.4 – 22 maf
– 1922 was high!
Reality Check
Updated recently•15 maf•1920s still high•1100s?
Testimony to State Govt.(March 3, 2003, AZDS,
Drought in West may last decades)
• Expert: The current drought in Arizona could conceivably last for 20-30 years.
• Agency official: “We hope all this stuff about the ocean [and our rainfall] turns out to be wrong.”
Colorado River
• Interesting, hard problem
• Huge data set
– Thousands of living trees
• Took tens of years of work
• Multidisciplinary
– Dendro, hydro, geogr, stats
• Compelling great moment
Other Great Moments
• Forest fire history
– Profound ecological change, Sky Islands
• Drought atlases
– North America, Asia, Europe
• Dating, discovering past earthquakes
– San Andreas fault
• Dating past volcanic eruptions
– Sunset Crater, Arizona
Potential GM: Global Warming
Global Warming?
• Instrumental record shows warming
• Ocean or land
• Now: warmest years are 1.8 °F above coolest years
• Is this unusual in the long term?
Paleo Temperature
• Worldwide temperature reconstruction
• Tree rings, ice,pollen, corals
• Last 1300 years: Current warming is unusual
Paleo Temperature
Potential GM: Global Warming
• Interesting, hard problem
• Huge data set
– Thousands of trees, living & dead
– Ice, pollen, corals, sediments
– Weather data worldwide
• So far: decades of work
• Multidisciplinary
– Dendro, ocean, neo-paleoclime, policy
• Tree rings on global warming: Great?
Questions, comments?