Welcome to the website for the University of Minnesota's Center for Dendrochronology. We are based in the Department of Geography, and are located in the Social Sciences building on the West Bank of the UMN’s Twin Cities campus.

Our research uses information encoded into tree rings to address questions related to climate, water resources, ecology and natural history.

Public lecture on global warming and future drought

posted Feb 3, 2014, 5:41 PM by Scott St. George   [ updated Feb 23, 2014, 8:37 AM ]

We're pleased to announce Dr. Ben Cook will deliver a public lecture on global warming and twenty-first century drought at the University of Minnesota on March 7. 

Ben is a climate scientist at NASA's Goddard Institute for Space Studies in New York City. He's also affiliated with Columbia's Lamont Doherty Earth Observatory in Palisades, New York. Ben has published extensively on the causes and consequences of drought in North America, as well as the projected response of moisture-delivery systems to anthropogenic climate change. He also has first-hand experience developing paleoclimatic records and has used proxies to evaluate the performance of general circulation models. 

If you'd like to meet with Ben during his visit, please contact Scott St. George (stgeorge@umn.edu).

What: The Department of Geography's 'Coffee Hour' lecture series
When: 445 Blegen Hall on the University of Minnesota's West Bank campus
Where: 3:30PM on March 7, 2014

Global warming and 21st century drying
Global warming is expected to increase the frequency and intensity of droughts in the 21st century, but the relative contributions from changes in moisture supply (precipitation) versus evaporative demand (potential evapotranspiration; PET) have not been comprehensively assessed. Using output from a suite of general circulation model (GCM) simulations from version 5 of the Coupled Model Intercomparison Project, projected 21st-century drying and wetting trends are investigated using two offline indices of surface moisture balance: the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Evapotranspiration Index (SPEI). PDSI and SPEI projections using precipitation and Penman-Monteith based PET changes from the GCMs generally agree, showing robust cross-model drying in western North America, Central America, the Mediterranean, southern Africa, and the Amazon and robust wetting occurring in the Northern Hemisphere high latitudes and east Africa (PDSI only). The SPEI is more sensitive to PET changes than the PDSI, especially in arid regions such as the Sahara and Middle East. Regional drying and wetting patterns largely mirror the spatially heterogeneous response of precipitation in the models, although drying in the PDSI and SPEI calculations extends beyond the regions of reduced precipitation. This expansion of drying areas is attributed to globally widespread increases in PET, caused by increases in surface net radiation and the vapor pressure deficit. Increased PET not only intensifies drying in areas where precipitation is already reduced, it also drives areas into drought that would otherwise experience little drying or even wetting from precipitation trends alone. This PET amplification effect is largest in the Northern Hemisphere mid-latitudes, and is especially pronounced in western North America, Europe, and southeast China. Compared to PDSI projections using precipitation changes only, the projections incorporating both precipitation and PET changes increase the percentage of global land area projected to experience at least moderate drying (PDSI standard deviation of ≦ -1) by the end of the 21st-century from 12% to 30%. PET induced moderate drying is even more severe in the SPEI projections (SPEI standard deviation of ≦ -1; 11% to 44%), although this is likely less meaningful because much of the PET induced drying in the SPEI occurs in the aforementioned arid regions. Integrated accounting of both the supply and demand sides of the surface moisture balance is therefore critical for characterizing the full range of projected drought risks tied to increasing greenhouse gases and associated warming of the climate system.

Torbenson Thesis Defense, December 5

posted Dec 2, 2013, 7:57 AM by Scott St. George

It's my pleasure to invite you to attend the public defense of Max Torbenson's Master's thesis on Thursday, December 5 at 9:30AM. The defense will be held in Room 614 in the Social Sciences Tower and should be conducted over roughly one hour.

Max's research has focused on the growth dynamics of red fir (Abies magnifica) in the Klamath Network Parks. In his presentation, Max will describe his efforts building a network of new tree-ring width records from this species, and describe how climate influences the growth of this tree within northeastern California and southeastern Oregon's high-elevation forests.

I hope you can join us!

Grad seminar: Become a presentation superstar!

posted Nov 6, 2013, 3:56 PM by Scott St. George

This spring, I'll be offering my graduate seminar on scientific presentations again (for the first time in two years). The course will run for half the semester (7 weeks) and be offered twice (back-to-back), so people will have two chances to fit it into their schedule.

GEOG8260: The Art of Scientific Presentations (two credits)

The ability to deliver effective and engaging oral presentations is a critical skill for scholars in all disciplines. Unfortunately, despite the importance of clear communication, professional presentations about research are too often confusing, abstract and boring. In this seminar, you'll be introduced to a diverse set of presentation methods and use exercises to apply these techniques to your own work and ideas. By the end of the semester, you will have experimented with a broad range of presentation styles and identified the method or methods that best suits your own style and research subject. More generally, you will have become a more effective communicator, improved your ability to discuss your research with non-specialists, and be better representatives for your discipline, your institution, and your ideas.

Which section should I choose?
In both sections, the contents and goals of the course will be exactly the same, but they will differ in location and thematic focus. Section 001 will be held on Thursdays from 9:30AM to 12:30PM and will run between Jan 22 and Mar 12 (inclusive). This section will meet on the St. Paul campus and will emphasize the challenges of communicating physical science. Section 002 will also be held on Wednesdays from 2:30PM to 5:30PM, but will convene during the second half of the semester (Mar 26 to Apr 7). This section will meet on the West Bank of the Twin Cities campus and is intended primarily for scholars in the social sciences and the humanities.
    Depending on the section, we'll have a different mix of guests visiting the course, but the content and exercises will be the same, so students are welcome to join either one, regardless of their own background.

What have students said about this course?
If you're thinking about joining us, I'd encourage you to look over the written feedback provided by students enrolled in previous years. I've posted their comments (complete and without any editing) here.

Webinar: Five Things You Can Do Right Now to Make Your Presentations a Little Bit Better
If you'd like to get a short preview of some of the ideas and approaches we'll review in this course, watch this short webinar I delivered in April to IRIS (a seismology research group based in DC). It's available here.

If you have any questions about this class, please send an email to stgeorge@umn.edu.

Dan Griffin will join the Dendro Center next summer

posted Nov 4, 2013, 11:50 AM by Scott St. George   [ updated Nov 4, 2013, 11:50 AM ]

On behalf of the Dendro Center, I'm happy to announce that Dan Griffin will join the faculty in Department of Geography, Environment and Society next summer. Dan obtained his doctorate in Geography at the University of Arizona earlier this year, and currently holds a post-doctoral research position at Woods Hole Oceanographic Institution in Massachusetts, where he's investigating past and future climate change in Central America.

Dan is an extremely accomplished young scientist. At Arizona, he held a Graduate Research Fellowship from the US Environmental Protection Agency's STAR Program. He's also led or contributed to over a dozen scientific papers on paleoclimatology, water resources, old-growth forests, and several other topics.

We're all very excited that Dan will be joining the Dendro Center in August 2014, and look forward to Minnesota having one of the largest research groups specializing in dendrochronology anywhere in the nation!

The Dendro Center goes to Tucson for AmeriDendro '13

posted May 1, 2013, 1:52 PM by Scott St. George

Two weeks from now, several members of our research group will be traveling down to sunny Tucson Arizona to attend the Second American Dendrochronology conference (known as 'AmeriDendro'). If you'll be attending the meeting and are able to attend one of our talks or posters, please wander over and say 'hi'!

Tuesday May 14
3:30 PM
Chris Crawford
Frost-ring formation in Douglas-fir at the lower forest border in central Idaho
Salon B

Wednesday May 15
6:00 to 9:00PM
Salon E

Max Torbenson
Traumatic resin ducts in Abies magnifica at interior sites along the central Pacific Coast of the United States

Sarah Appleton
Dating the Mid-Holocene History and Glacial Stratigraphy of Wachusett Inlet, Glacier Bay National Park and Preserve, Southeast Alaska

Thursday, May 16
9:20 AM
Salon D
Kurt Kipfmueller
Fire history along a historic travel corridor in Minnesota's Boundary Waters Canoe Area Wilderness

10:40 AM
Salon B
Scott St. George
Widespread absent rings have not occurred in boreal and temperate trees outside the American Southwest

Ancient trees and past climates from Craters of the Moon, Idaho

posted Feb 3, 2013, 7:17 PM by Scott St. George   [ updated Feb 3, 2013, 7:18 PM ]

This Wednesday (February 6), Chris Crawford from the Dendro Center will give the first Quaternary Paleoecology seminar of the Spring 2013 semester. The QP seminars are open to the public and refreshments are available for purchase.

When: 7:30PM, Wednesday February 6, 2013
Where: 1426 North Hythe Street, St. Paul, Minnesota

Annual and sub-annual precipitation reconstructions for the Craters of the Moon lava complex, eastern Snake River Plain, USA.
Christopher J. Crawford, University of Minnesota Center for Dendrochronology

Abstract: The Craters of the Moon (COM) National Monument is a basaltic-lava complex on the eastern Snake River Plain (SRP) in south central Idaho, USA. COM has formed over eight separate eruptions during the Holocene and since the last eruption ~ 2,000 years ago, ancient limber pine (Pinus flexlis) and Douglas fir (Pseudotsuga menziesii) trees have sought refuge on lava flows and weathered cinder cones. Tree-ring widths from these ancient trees provide unique high-resolution paleoclimate archives that can be used to examine past and present climate changes on the eastern SRP. Using instrumental precipitation records, tree-ring widths were transformed into annual and sub-annual precipitation estimates spanning the past 500 years. COM precipitation reconstructions show well known drought and pluvial episodes documented elsewhere with tree-rings across the western US. More importantly, these reconstructions suggest that droughts (pluvials) on the eastern SRP are frequency-dependent, and that prolonged dry (wet) conditions over multiple decades cannot occur without summer-winter precipitation deficits (surpluses).

Feb 1: Public lecture by Neil Pederson (Columbia U)

posted Jan 25, 2013, 7:57 AM by Scott St. George

The Center for Dendrochronology, The Silviculture and Applied Forest Ecology Lab and the Center for Forest Ecology are pleased to present a public lecture by Dr. Neil Pederson (Lamont-Doherty Earth Observatory)

3:30 PM
Friday, February 1
203 Green Hall, St. Paul Campus

Regional-scale dynamics in a gap-dominated forest
Dr. Neil Pederson, Lamont-Doherty Earth Observatory, Columbia University

In this lecture, Dr. Pederson will review hydroclimatic changes over the eastern United States and present evidence of regional scale forest dynamics in forest dominated by deciduous species and gap dynamics.  Results indicate that climate has a long-term legacy in the Eastern Deciduous Forest not only at millennial time scales, but at decadal to centennial scales. These findings provide one of the first bridges between plot-level studies and paleoecological studies of forest history and development of broadleaf-dominated forests in a humid region.

Please visit Dr. Pederson's website at http://www.ldeo.columbia.edu/~adk/ for more information about his research on tree rings, forest ecology and Central Asia.

This Friday (August 17), learn about both the art and science of trees

posted Aug 13, 2012, 10:32 AM by Scott St. George

Minneapolis artists, Wilber H “Chip” Schilling (2010 Minnesota Book Artist of the Year Award Recipient) and David Pitman (co-founder of Art Shanty Projects), have collaborated on an exhibition and artists’ book.Please join them for an evening to celebration the closing of Cull.arbor.ation: Culling the Urban Forest and the publication of the artists’ book, created as part of the exhibition, Agents of Change; What Goes Around Comes Around.

WHAT: Book signing, publication party and closing night celebration
GUEST TALK: Scott St. George is an Assistant Professor of Geography at the University of Minnesota. He is an earth scientist who specializes in dendrochronology. He will do a short 15 minute talk on tree ring dating and what it means with samples.
WHEN: August 17, 2012, 5:30pm – 8:30pm (Talk at 7pm), this event is free and open to the public
WHERE: Traffic Zone Center for Visual Art Gallery, 250 Third Avenue North, Minneapolis, MN  55401
INFO: info@indulgencepress.com / 612-803-6769

Agents of Change: What Goes Around Comes Around
By Wilber H. “Chip” Schilling and David Pitman
©2012 Indulgence Press, Minneapolis
Edition size: 50
Size: 8.25 x 7.5 x .75 inches (closed) / 8.25 x 194 x .75 inches (opened)
Medium: Artist Book (letterpress, digital/offset, hardcover, cloth-bound, accordion structure)
Price: $60.00

Agents of Change is an artists’ book, produced in the spirit of the exhibition catalog, as part of Cull.arbor.ation: Culling the Urban Forest. It explores urban forestry practices, environmental policymaking, and the parasitic diseases and non-parasitic disorders that destroy trees. Agents of Change is printed two-sided and grows to 194 inches when fully open. It contains observances by the artists and a 7” vinyl record with tracks containing chainsaw and wood chipping sound art. Photographic images in the book represent a timeline of important political changes and speak to the loss of trees in the urban forest.

Cull.arbor.ation: Culling the Urban Forest
is a record of urban deforestation. It discusses urban forest management, in particular the management of blight stricken trees. Through the documentation of tree stumps and through repurposing them as artifacts, the idea of recorded information is explored. Re-imagining time and space based on what is left behind—tree stumps, wood pulp, recycling, the remembrance of trees no longer there—Cull.arbor.ation chronicles the urban forest in a gallery space that is both real and imagined. Cull.arbor.ation asks the viewer to see the forest for the removed trees, to engage in the stewardship of this forest, and to be drawn into and out to the managed forest (www.cullarboration.wordpress.com).

Fall 2012 graduate seminar in decadal climate and ecology

posted May 12, 2012, 3:58 PM by Scott St. George   [ updated May 12, 2012, 7:38 PM ]

Graduate seminar, Fall 2012
GEOG8280: The impact of decadal climate variability on terrestrial ecosystems
Instructor: Scott St. George
Wed, 2 to 5PM

The field of decadal prediction has emerged as a priority area for climate research, largely because the upcoming ten to thirty years are often a critical period for planning, resource management and public policy. The oceans are the main source of low-frequency behavior in the global climate system, and a growing body of evidence suggests that such long-memory behavior has a discernible influence on the hydroclimate of North America and the frequency and spatial pattern of drought across the continent. Several recent studies have further argued that low-frequency behavior in the climate system, through its influence on drought, acts to synchronize the behavior of wildfire, insect outbreaks and other aspects of terrestrial ecology on timescales that range from one to several decades. Despite the potential utility of this behavior to long-term planning and management, the specific physical mechanisms that allow decadal signals produced by the surface oceans to be transmitted remotely through the atmosphere to influence landscape-scale processes are often poorly understood.

This course will examine decadal and multidecadal variability in the global climate system and investigate how this behavior might plausibly influence the dynamics of terrestrial ecology and landscape-scale disturbances. Weekly readings and discussions will review the physical processes believed to give rise to decadal climate variability, the empirical evidence for interconnections between low-frequency aspects of the surface ocean and terrestrial systems, and potential solutions to the 'decadal problem' that afflicts observational, paleoclimate and modeling studies alike. Students will be challenged to conduct their own analysis of decadal variability in climate or ecology through the semester, either working on their own or as part of a small team.

This course may appeal to students interested in climate dynamics, disturbance ecology, statistical climatology, paleoclimatology/paleoecology, or hydrology. Prior coursework in one or more of these topics at the graduate or senior undergraduate level would be very helpful. For more information, please contact Scott St. George at stgeorge@umn.edu.

Representative readings
Hessl, A. E., D. E. McKenzie, and R. Schellhaas (2004), Drought and Pacific Decadal Oscillation linked to fire occurrence in the inland Pacific Northwest, Ecol. Appl., 14(2), 425–442.
Huybers, P., and W. Curry, 2006: Links between annual, Milakonvitch and continuum temperature variability. Nature, 441, 329–332.
Kipfmueller, K.F., Larson, E. R and St. George, S. 2012. Does uncertainty in proxy reconstructions affect the relations inferred between the Pacific Decadal Oscillation and wildfire activity in the western United States? Geophysical Research Letters. 39, L04703, doi:10.1029/2011GL05064.
Kitzberger, T., P. M. Brown, E. K. Heyerdahl, T. W. Swetnam, and T. T. Veblen (2007), Contingent Pacific-Atlantic Ocean influence on multicentury wildfire synchrony over western North America, Proc. Natl. Acad. Sci. U. S. A., 104(2), 543–548, doi:10.1073/pnas.0606078104.
Klemes, V., 2000: Drought prediction: A hydrological perspective. Common Sense and Other Heresies: Selected Papers on Hydrology and Water Resources Engineering, Canadian Water Resources Association, 163–176.
MacDonald, G. M., and R. A. Case (2005), Variations in the Pacific Decadal Oscillation over the past millennium, Geophys. Res. Lett., 32, L08703, doi:10.1029/2005GL022478.
Manabe, S., and T. Delworth (1990), The temporal variability of soil wetness and its impact on climate, Clim. Change, 16, 185–192.
McCabe, G. J., M. A. Palecki, and J. L. Betancourt (2004), Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States, Proc. Natl. Acad. Sci. U. S. A., 101(12), 4136–4141.
Meehl, M. A., et al. (2009), Decadal prediction: Can it be skillful?, Bull. Ame. Meteorol. Soc., 90, 1467–1485.
Newman, M., G. P. Compo, and M. A. Alexander (2003), ENSO‐forced variability of the Pacific Decadal Oscillation, J. Clim., 16, 3853–3857.
St. George, S., and Ault, T. R. 2011. Is energetic decadal variability a stable feature of the central Pacific Coast’s winter climate? Journal of Geophysical Research - Atmospheres 116, D12102, doi:10.1029/2010JD015325.

Chris Crawford Wins Publication Award

posted May 4, 2012, 7:50 AM by Kurt Kipfmueller

Congratulations to Chris Crawford for winning the Department of Geography's Best Graduate Student Publication Award-The Ralph Hall Brown Prize for his article 'Do high-elevation northern red oak tree-rings share a common climate-driven growth signal?' published by Arctic, Antarctic, and Alpine Research.

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