Great Moments in 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

Andrew Ellicott Douglass

The Gap

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

14 N 14 C 14 N into plants, animals they diehalf-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 … ?

Irish oak: 9,000 years US bristlecone pine: 8,700 years German oak-pine: 12,500 years

6000 BCAD 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, th 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 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?