Tree-Ring TimesNewsletter of the University of Arizona Laboratory of Tree-Ring Research Fall 2001

Bristleconework raiseschances ofbridging gapBy Christina Jarvis

In an otherworldly landscape,scientists and students from the Univer-sity of Arizona�s Laboratory of Tree-RingResearch in Tucson are advancingknowledge of timescales and climate onPlanet Earth.

For the past two years, a renewedBristlecone Pine Project, directed byThomas P. Harlan, has consolidatedprevious research and successfullyextended the Campito Mountainchronology by 1,800 years, to about7,200 years in length. In the future,Harlan hopes to bridge a gap betweenthe 8,700-year Methuselah chronologyrooted in the present to a 3,000-year�floating� chronology based on olderwood samples. This could extend thelongest tree-ring chronology for NorthAmerica back into the last Ice Age.

This effort was made possible by ananonymous donor wishing to contributeto a project unique to LTRR for whichsuccess was possible but not guaranteed.Harlan had been working on thebristlecone project unofficially for manyyears but said the funding allowed himto expand his efforts. He was able topurchase a Global Positioning System(GPS) and laptop computer, equipmenthe uses to identify the location ofsampled trees and stumps in the fieldand then plot them on a computerized

topographic map. The funding alsocovers field expenses for Harlanand some trained assistants forseveral summers.

�I would have done thisresearch anyway, but not at thisscale,� Harlan said. �Because ofthe new funding, 20 other people,most of them volunteers, were ableto contribute their time, labor andmoney. Much, much more wasaccomplished than would havebeen possible otherwise. I deeplyappreciate all their hard work andthe financial assistance that madethis synergy possible.�

The Bristlecone Pine Project atLTRR has a multi-generationalhistory. Edmund Schulman beganbristlecone work in the WhiteMountains of California in the 1950s.He died at age 49 in 1958, two weeksbefore Thomas Harlan arrived atLTRR. C. Wesley Ferguson carried on,working primarily with specimens fromthe area dubbed �Methuselah Walk�

because of the many ancient bristleconepines lining the path.

Whereas Schulman sampled livingtrees, Ferguson and others sampleddead wood also, and reported longchronologies exceeding any in NorthAmerica � an 8,701-year record goingall the way back to 6700 B.C. Somewere skeptical and doubted that such oldwood could remain on the groundsurface without rotting away. Becausethe tree-ring data was pieced togetherfrom many samples, one bit of woodplugged into the wrong place couldaffect the whole chronology. The resultshad to be crosschecked.

In 1970, geologist Valmore LaMarcheobtained a grant to investigate bristle-cones on Campito Mountain, also in theWhites. Interested in geological timechanges, he had noted that in mountainranges across the United States wherebristlecone pines were present, deadwood lay 500 feet above the present treeline.

Please see BCP on page 3

Dating of some bristlecone remnants can pinpoint the time frame whentreeline used to be higher than it is now in the White Mountains of California.

Photo by Tom Harlan

LTRR

DendrochronologyDirector�s note

We wish you Happy Holidays with this second issue of LTRR�s Tree-Ring Times! Our continued efforts to carry out world-class teaching,research, and service continue, and in this issue you will see that our work isgreatly aided by generous help from our friends. The oldest living trees inthe world - bristlecone pines - were discovered by LTRR�s EdmundSchulman, and his legacy of work on bristlecone pine (and that of manyother LTRR scientists) is continued today with the help of an anonymous giftto LTRR. Our lead story in Tree-Ring Times highlights the work of TomHarlan and associates on bristlecone pine, which has been made possible bythis generous gift. The help of our friends and alumni are all the moreimportant these days, as state-wide cuts in the budget reduce ourability to support �seed� research, such as examples of potentialprojects in the tropics and in northern Mexico described on the backpage of this issue. In future issues of Tree-Ring Times we will describeother examples of how gifts and endowments have assisted us in thepast, and how help from you could aid us in the future.

Happy New Year! (and New Ring!)

A 35-room cliff dwelling in Cueva Bringas, shown above, remains undated,as do dozens of others in this region of eastern Sonora, Mexico. LTRRadjunct assistant professor Ron Towner would like to change that. See moredetails on the back page of this issue.

Tree-Ring Times Production Team Fall 2001Editor Thomas W. Swetnam

Managing Editor Melanie Lenart

Technical Support Martin Munro Volume 1, Issue 2

Photo by Ron Towner

Recognitionand awards

Katherine K Hirschboeck,Associate Professor, first recipientof the Editor�s Award from the Journalof Hydrometeorology for �exceptionallythorough review of papers submittedduring the journal�s inaugural year,�2001.

Thomas W. Swetnam,Director and Professor, 2001 W.S.Cooper Award from the EcologicalSociety of America for an outstandingpaper in geobotany and physiographicecology, with Julio L. Betancourt inthe Journal of Climate 11:3128-3147,1998.

Donald Falk, GraduateAssociate. Recipient of 2001 RobertHoshaw Award from the Departmentof Ecology and Evolutionary Biologyfor outstanding graduate student, andof a National Science Foundationdissertation improvement grant.

Ana S. Martinez,Administrative Assistant, 2001 CoSStaff Recognition Award.

Kurt F. Kipfmueller,Graduate Associate, UA Foundationaward for �Meritorious Performance asa Graduate Teaching Assistant,�Spring 2001.

Theodore Turley, StudentAssistant, graduated, (Dean�s list),December 2001, Eller College ofBusiness and Public Administration,B.S. in business administration.

William �Ed� Wright,Graduate Associate, graduated May2001, Ph.D., UA Department ofGeosciences.

Christine Hallman, GraduateAssociate. Graduated December2001, M.S., UA Department ofGeosciences.

BristleconeBCP, continued from page 1

Please see BCP on page 10

Thomas Harlan enters GPSinformation -- gathered via satellite --about the location of wood samples inthe field. This way he and others canretrace their steps to track downsamples that upon analysis turn out tocover pertinent time frames.

3

Photo courtesy of Tom Harlan

His investigation on Campito hadtwo goals: to discover when the treeline moved down and to create anindependent bristlecone pine chronol-ogy to validate the one for MethuselahWalk.

He asked Thomas Harlan tooversee a crew based at the CrookedCreek Research Station. Within anarea laid out by LaMarche, they madea topographical map of Campito,surveying, sampling and tagging mostof the bristlecone pine wood they couldfind�chunks large and small, deadtrees, logs, and uppermost living trees.

Harlan took the Campito Moun-tain samples back to LTRR and,without looking at any other chronolo-gies, crossdated the dead wood withliving trees. He produced a 5,300-year chronology that verified that ofthe Methuselah Walk. Although theMethuselah Walk set remains thelongest North American tree-ringchronology, Campito is the secondlongest record.

�The Campito chronology is thelongest in the world for altitudes above11,000 feet,� Harlan noted.

The 1970s effort on CampitoMountain was successful, but therewas more work to be done. Somepieces of wood were even older thanthe existing Campito chronology, socollection was required to fill in thegaps. LaMarche apparently suggestedto his colleagues that he had devised amethod for high quality reconstructionof temperature over a long time scale.He wanted to return to Campito tocollect more samples, but he died in1988 at age 50 without having sharedhis temperature reconstruction methodwith colleagues. Wes Ferguson haddied two years before, at age 64.

Donald A. Graybill then obtaineda grant for bristlecone pine research inthe western U.S. to develop new areasand chronologies for the reconstruc-tion of temperature and precipitation.He soon became ill and, unable to dothe fieldwork himself, sent Harlan inhis stead. Graybill died in his earlyfifties in 1993.

The irony of the short lives ofscientists who study the world�s oldesttrees is not lost on Harlan, but this hasnot slowed his drive to continuebuilding on the work of his predeces-sors. He and associate Greg Lazearcompiled a computer program to keeptrack of and date samples. Their firsttask was to consolidate all datacollected in previous projects andboxed separately upon the deaths ofSchulman, LaMarche, Ferguson andGraybill. Harlan is entering thisinformation into a computer database.

So far he has incorporated 1,000 pagesof field notes, not including data fromwork this past summer.

After preliminary sorting, it wastime for fieldwork. Teams of students,volunteers from as far away as Englandand paid assistants have spent up to sixweeks per summer working on thisproject. They have been taking newsamples, locating samples using GPSand plotting them on the computerizedmap, relocating tagged specimens andlooking for new sites with promise.

Many tags were gone, cartedaway by birds or pried off by theincessant wind that rattled aluminumtags until the nails pulled out. On someCampito wood above timberline, thesurface that had been protected by thetag was about 3 mm higher than theunprotected surface, showing theeffects of erosion by weathering.

The group experienced the usualhardships of fieldwork � softened byassistance from the U.S. ForestService, which provided a trailer withoffice space and the use of another forcooking and bathroom facilities. Theassembled company was soaked by rainfor the first two weeks. Incrementborers got stuck in trees. On steepmountain roads, their wheel edgescame within inches of open mine shaftsand steep drop-offs. And they workedhard.

There were some fringe benefits.They enjoyed camaraderie aroundcampfires. And they saw wild horses,blue grouse, hares, and elk.

In addition to Campito Mountain,teams obtained further informationfrom Wheeler Peak, Indian Garden,and Ward Mountain in Nevada andPine Peak, Swazey Mountain, and the

Dendroarchaeology

Professor JeffreyDean stands outsidethe Laboratory ofTree-Ring Research,housed under thefootball stadium onthe UA campus.

�Great house�spruce and firsborn on distantmountain topsBy Melanie Lenart

Tree-ring analyses of the beams inancient structures have been crucial inadvancing understanding of the ChacoCanyon civilization that thrived aroundthe turn of the last millennium in NewMexico. But sometimes researchers haveto read between the lines to get theanswers, as a team of scientists thatincluded the LTRR�s Jeffrey Dean foundout this year.

The scientists used strontiumisotopes in ground-up wood to pinpointthe source of some of the spruce and firtrees used to construct the multi-storystructures built by the apparentancestors of today�s Puebloans, knownas the Anasazi. Combining the informa-tion with earlier work using the trees�annual growth rings to date the beamsprovided additional insight into thisancient culture.

�What they were doing wasactually thinning the forest rather thaneradicating it,� Dean said of the Anasazipeople who inhabited New Mexico�sChaco Canyon from at least 900 to about1150 A.D.

The team included RenewableNatural Resources research specialistNathan English, Julio Betancourt of theU.S. Geological Survey and University ofArizona geologist Jay Quade as well asDean. Their findings were published inthe Sept. 25 issue of the Proceedings ofthe National Academy of Science.

The study buildsupon research done in the1980s by Betancourt andDean, who used scanningelectron microscopes toidentify about a quarter ofthe dated beams in one ofthe structures as spruceand fir trees.

�Spruce and firshave not grown in the SanJuan Basin for the last10,000 years, since thePleistocene,� Dean noted.�Now they only grow on mountaintops.�

The isotope study matched someof these beams with trees from theChuska Mountains to the west and theSan Mateos (popularly known as MountTaylor) to the southeast. The research-ers ruled out the San Pedro Mountainsto the east as a source of the spruce andfir logs used in Chaco Canyon struc-tures. All three mountains are 50 milesor more from the site.

�One of the reasons they probablydidn�t get logs from the San Pedro wasthey didn�t go to the east. They simplyweren�t interested in it,� Dean theo-rized. For instance, few of the roads inthe widespread prehistoric system headeast.

The study found that trees in thethree mountaintops contained distinc-

tively different ratios of a heavierstrontium isotope compared to the morecommon strontium isotope, which islighter by one neutron. English refined alaboratory technique to reveal theisotopic �signatures� in trees living nowin the mountains, which allowed theteam to match ancient wood sampleswith their source and create a �timberledger.�

�That gives us the ability to assessthe cost to this society of harvesting andtransporting these trees,� English said.

English noted that the studyindicates widespread cooperation amongthese ancient people. For one thing,trees from the same year and samesource were placed into different �greathouses;� for another, individual housescontain trees from the same year anddifferent sources. The Chaco Canyon sitehas a dozen �great houses,� with thelargest containing about 600 rooms infive stories.

Betancourt and Dean had figuredthat the Anasazi carried the spruce andfir logs down from the distantmountaintops. In addition to offeringproof of this, the latest study seems todispute a theory that the long-distancetrips for construction materials � whichinvolved hoisting these logs on foot �evolved in response to a depletion ofresources.

Photo by Melanie Lenart

Chaco Canyon

Pueblo Bonito, above, was constructed more than 1,000 years ago in Chaco Canyon, New Mexico.

�It�s much like we harvest timber today� we find the richest, most appropriatestands and log them rather than movingoutward in distance from the lumbermill,� English said.

In their paper, the researcherstheorize that the Anasazi architectsheaded for the summits to seek saplingsof specific dimensions, typically less than9 inches in diameter. The easier-to-reachponderosa forests on the mountainsideprobably lacked a suitable array ofsaplings, judging from dendroecologystudies by LTRR Director ThomasSwetnam and others that indicate thatprehistoric ponderosa forests weretypically dominated by large trees.

A variety of other studies byLTRR faculty have contributed to thecurrent understanding of Chacoanculture. In 1929, LTRR founderAndrew E. Douglass used charcoal fromArizona to �bridge the gap� between twosouthwestern chronologies, one based inthe present and the other dangling intime, and thereby establish the generaltiming of occupation of Chaco Canyon.

Bryant Bannister, a longtimeLTRR researcher who directed the lab

from 1964 to 1982, based his 1959dissertation on expanding Chaco Canyoncrossdating efforts. He identified lower-elevation species, but the wood helabeled �species X� turned out to be thehigh-elevation spruce and fir lateridentified by Dean and Betancourt.

Dean, who has been adendroarchaeologist with the Laboratoryof Tree-Ring Research for 39 years, hasbeen involved in other projects to datesome of the 200,000 logs used in theconstruction of Chaco Canyon�smonumental structures. The tree-ringcrossdating of beams demonstratedconstruction occurred between 900 andabout 1150 A.D., although recentevidence indicates the Pueblo Bonitostructure dates back to the 800s, henoted.

The dendroarchaeologist contin-ues to work with the others from thelatest study to expand their provenancestudies. Dean is particularly excitedabout their plans to apply strontiumisotopes to determining the source ofcorn cobs and other food remainspreserved for 1,000 years in Anasazitrash piles.

Evidence indicates that 3,000 to4,000 people lived in this civilizationcenter during its heyday, Dean said, soit�s likely that food needs exceeded thecanyon�s agricultural capacity � evenconsidering the Anasazi�s irrigationsystem using side canyons to collectrunoff from precipitation.

�One of the theories is peoplewere importing food into Chaco Can-yon,� he explained. �They also importedpottery, probably because they ran outof fuelwood. They imported turquoise aswell, and chert for making stone tools.Yet there is no evidence that much ofanything went out. It�s like a blackhole.�

Perhaps future provenance studieswill shed some light on this question aswell. In the meantime, efforts continueto learn more about this ancient culture.

�It�s an ongoing project,� Deansaid. �We get new tree-ring samplesevery year from Chaco Canyon.�

For more information, contact Dr. Deanat 520-621-2320 orjdean@LTRR.arizona.edu.

5

Photo by Jeffrey Dean

Dendroclimatology

Tree rings tellof climate inTurkey, JordanBy Melanie Lenart

After putting the finishing toucheson a 660-year climatic reconstruction forTurkey, LTRR research specialist RamziTouchan moved one step closer to hisdream of creating a long-term climatechronology for the Middle East region.

Touchan, a researcher with thelab since 1991, previously completed a396-year climatic reconstruction forsouthern Jordan with LTRR colleagues,research specialist David Meko andprofessor Malcolm Hughes. Now he willturn his attention to the samplescollected in Turkey, Syria and Lebanonthis past summer.

The results from Turkey showedspring droughts tend to be short-lived, atleast relative to North American dryspells that tree rings indicate can lastdecades. It�s rare for a drought to lastmore than five years in southwestTurkey, judging from Touchan�spreliminary results.

Drought durations appear similarto results for Jordan, which show winter-spring droughts rarely last more thanfive years. These proxy records ofdrought, revealed through the pattern ofsmall annual growth rings in trees, canprove especially important in the MiddleEast because continuous instrumentalclimate records for these desert ecosys-tems generally go back only about 50years.

�Water is the main issue for all ofthe countries in the Middle East,�Touchan noted. �For the local people,the issue is one of understandingdrought patterns.�

The project to expand knowledgeof regional drought regimes and fit theMiddle East into long-term regionalclimate patterns has taken Touchan tothe Middle East for the past twosummers. He hopes to continue theresearch for at least another five years,working to train local foresters andeducators in the science of dendrochro-nology.

Touchan�s vision also calls fordeveloping a university-based tree-ringlaboratory that will be affiliated with theUniversity of Arizona, at least to start.Already officials in Turkey, Jordan,Lebanon and Syria are vying for theopportunity to provide buildings andfaculty support for this purpose, hesaid.

Touchan hopes U.S. fundingagencies and private philanthropists willrecognize the value of furthering theongoing collaboration he has initiatedwith support from the National ScienceFoundation�s Earth Systems Historysection.

The education effort is alreadypaying off. Touchan was assisted in thefield this past summer by two overseascolleagues � Adib Rahme, College of

Agriculture dean at the University ofAleppo in Syria, and Nesat Erkan of theSouthwest Anatolia Forest ResearchInstitute in Turkey � who learned abouttree-ring techniques during a one-monthvisit to the LTRR earlier this year. Inthe coming year, Touchan plans to traina scientist from Lebanon�s Ministry ofAgriculture.

�My strategy is to depend more onlocal people once we train them,� hesaid. �We�re trying to get a mixture ofcollaborators of scientists in thoseregions.�

UA geosciences undergraduateBrian Wallin also joined Touchan onboth sample-gathering trips. Wallin tookthe field work in stride and found peoplefrom the different cultures fascinatingand friendly.

�It was my first time out of thecountry, except for Mexico. I have toadmit I was a bit nervous. But everyonewas very friendly,� Wallin said. �Thisyear, going back to Turkey was like goingback to see old friends.�

Touchan and Wallin were inDamascus, Syria, when they heard thenews of the Sept. 11 tragedy.

Researchers led bythe LTRR�s RamziTouchan havecollected tree-ringsamples from theMiddle East sitesshown on the map atleft. Diamondsindicate analyses arealready underway,while triangles showsites of collectionsthat have not yetbeen analyzed.

Map created by Ramzi Touchan

Ramzi Touchan, center, prepares to sample trees in a cedar forest in Lebanonwith help from UA geosciences major Brian Wallin, right, and Abedllah Khatib,a graduate student with the University of Aleppo in Syria. A sculpture, in back,adorns the visitor�s area.

Although saddened, they werealso touched by the sympathy expressedby colleagues and even people they hadnever met.

�People over there were shockedand saddened by the tragedy and theloss of innocent American civilians,�Touchan reported. �When they knew wewere from the U.S., they came up to us

and offered their condolences. On theway to my sister�s house in Syria, thecab driver expressed sorrow and didn�twant to charge me for the ride.�

The two returned withoutincident. Since then, they�ve been hardat work crossdating tree cores bymatching the patterns of narrow andwide rings in a variety of trees to the

actual year.

Although Touchan plans toanalyze the tree-ring data from manyother sites before reaching any conclu-sions, he has high hopes that a regionalsignal will emerge from the collections.Previous research by others usinginstrumental records (1930-1991)indicates that Turkey�s winter rainfall isinfluenced by the North AtlanticOscillation (NAO), a pattern of global aircirculation known to affect wintertemperatures in western Greenland andnorthwestern Europe.

In addition to helping to refineunderstanding of how the NAO affectsthe Middle East, Touchan plans to applythe research to learn more about theSiberian High and other atmosphericcirculation patterns. The Jordan resultsindicate a strong correlation between drywinters and the western extension of theSiberian High, for instance.

As part of a future five-year plan,Touchan and dendroclimatologist MaryGlueck would like to extend the collec-tion efforts and analysis to countries inNorth Africa, such as Tunisia andAlgeria. They also want to update andexpand the tree-ring chronologydeveloped for Morocco by CharlesStockton, a retired LTRR professor.Eventually he plans to apply theanalytical techniques to defining long-term streamflow of the Euphrates. Theunderlying goal for all this research wasdescribed succinctly in the summary ofpurpose written by Touchan:

�The Mediterranean is a water-deficit region and in parts of the regionthere is a history of conflict over naturalresources. This information will aid inanticipating and, it is hoped, lesseningthe likelihood of conflict over scarcewater resources.�

Dr. Touchan can be contacted at 520-621-2992 orrtouchan@LTRR.arizona.edu.

Middle East 7

Photo by Jean Estephan of Lebanon

Graduate Work: Rockies

Fire, climateinteractions inRocky Mountainwilderness areaBy Kurt F. Kipfmueller

Forest fires have long beenrecognized as an important componentshaping forest composition andstructure over long periods of time.In upper elevation forests neartimberline, fires are relatively infre-quent, occurring at intervals ofperhaps 100 years or more at anygiven place on the landscape.

While infrequent (temporally),these fires often reach large propor-tions and often completely kill mostoverstory trees. While the results ofthese fires are often dramatic, leavingbehind charred trees over thousandsof hectares, they are an integral partof a natural system where vegetationhas uniquely adapted to the fireregime over long periods of time.Climate has long been recognized as animportant agent controlling theoccurrence of large fires in manyforest landscapes.

In southwestern forests andlower elevation forests, there existimportant interactions betweenoscillating wet and dry conditionsleading to large fire events. Wet yearsare responsible for abundant vegeta-tion that (once dead) provides animportant fuel source during subse-quent dry periods.

The role of climate in influencinglarge fire events in upper elevations,however, is not well understood. Dryconditions during the summer clearly

Kurt F. Kipfmueller, right, takes a wedge from a tree in the Selway-BitterrootWilderness Area on the border between Idaho and Montana. He has developed1,200-year chronologies for two species to look at long-term interactionsbetween fire and climate.

play some role in large fire eventinitiation and propagation. However,little quantitative evidence hasaccumulated to identify interannualrelationships that may also be impor-tant, such as protracted droughtperiods.

I am conducting research thatinvestigates the interactions betweenfire and climate at long timescales.This research involves a three-pronged approach whereby tree-ringsare used to date fire events andreconstruct climate.

This research also investigatesthe patterns of forest recoveryfollowing fire events by using tree-rings to estimate establishment datesfor forest species. This research isbeing undertaken in the Selway-Bitterroot Wilderness Area located onthe border between Idaho andMontana.

The Selway-Bitterroot Wilder-ness Area is the third largest wilder-ness area in the coterminous UnitedStates and shares a border with theFrank Church River of No ReturnWilderness area, the largest wilder-

ness area in the lower 48 states.As part of the project, fire

history and age structure relationshipsare being reconstructed in foursubalpine watersheds within thewilderness area. I am determining thetemporal patterns of fire occurrence aswell as the patterns of forest recoveryfollowing large, destructive, fireevents.

The occurrence of large fireevents is being compared withreconstructed summer temperature toidentify the relationship betweenclimate and fire occurrence in theregion.

Climate is being reconstructedusing tree-rings collected fromsubalpine larch and whitebark pinecollected near the upper treeline.These tree-ring chronologies currentlyspan more than 1,200 years, from 721to 1998 A.D. They are among thelongest records of tree growth in theregion.

Kurt F. Kipfmueller can be contactedat 520-621-7681 orkurt@LTRR.arizona.edu.

Photo courtesy of Kurt F. Kipfmueller

Graduate Work: Frost rings

Frost rings inbristlecone andfoxtail pinesBy Christine Hallman

It is difficult to imagine a volcaniceruption in Indonesia affecting trees onthe other side of the Pacific Ocean. Yetlarge volcanic eruptions around the globesometimes leave their mark on trees inthe western United States in the form offrost rings. My thesis work involveslocating these tell-tale frost rings andthus helping to pinpoint dates ofpotential previous volcanic eruptions orlocations of anomalous circulationpatterns.

Through a systematic identificationof frost rings, climatic variations andspatial patterns in high-elevation pineslocated in the western U.S. can beidentified. Previous research suggeststhat climatically effective volcaniceruptions can disturb atmosphericcirculation patterns and cool tempera-tures globally. This sudden cooling canlead to frost formation in temperaturesensitive tree species. My researchincludes 14 bristlecone pine and twofoxtail pine sites located in the GreatBasin, Front Range of the ColoradoRockies, Arizona, and the SierraNevadas.

Since bristlecone and foxtail pinesare long-lived, they provide potential forthe documentation and/or discovery ofunusually low temperatures that may belinked to explosive volcanic eruptionsthrough notable frost events. My tree-ring samples date from 1692 BC to AD2000 with the majority of them datingafter AD 800. The oldest livingbristlecone is about 4800 years old. As

Christine Hallman inspects a tree-ring core under the microscope.

you can imagine, some of their rings arevery narrow. For example, a bristle-cone may have over 3000 rings in thespace of 2 feet.

My thesis research involves aregional frost-ring investigation of high-elevation pines in the western U.S. Thiswork builds on previous studies andcollections from a variety of researchersfrom LTRR as well as recently collecteddata. Specifically, my research isbased on the 1984 Nature article by thelate Dr. Valmore LaMarche, Jr. and Dr.Katie Hirschboeck. I�m working withDr. Hirschboeck to extend temporallyand spatially the findings in the 1984paper.

After identifying and categorizingfrost rings from over 900 tree-ringsamples, I compiled the frequency offrost-ring years for each sample fromeach site was compiled. The mostfrequent and widespread frost rings or�notable frost events� were determined.seventeen notable frost events wereidentified with 9 of them covering largeportions of the western US. Forexample, a widespread frost eventoccurs in AD 1453. This frost event isassociated with a 1452 eruption in theSouthwest Pacific and a 1451 eruptionin Java. The �notable frost event�

suggests subfreezing temperaturescovered large portions of the westernU.S. during the 1453 growing season.Some of the 17 notable frost events arerestricted to a given region (e.g., FrontRange of the Colorado Rockies) thus,implying that regional climatic variationsdo exist.

Eleven of my 17 notable frostevents match LaMarche andHirschboeck�s 1984 results. Theydefine a �notable frost event� as anevent that occurs in at least 50% of treesin a site or in two sites. My criteria for a�notable frost event� is that the frost ringoccur in at least 25% of the trees in asite and occur in two or more sites.

Trees at higher latitudes andhigher elevations tend to have a higherfrequency of frost events. Recentlycollected tree-ring samples do not show awidespread frost event in years followingthe 1982 eruption of El Chichon,Mexico, or the 1991 eruption ofPinatubo, Philippines, but more samplesneed to be collected. Although notwidespread, I have found frost rings in1982 and 1992 in younger trees.

Christine Hallman can be contacted at520-621-9731 orchallman@geo.arizona.edu.

9

Photo by Melanie Lenart

Bristlecone

BCP, continued from page 3

Wah Wah Mountains in Utah, the lattertwo being entirely new sites. An �i-button� temperature recorder wasattached to a timberline tree on Campito,where it collects temperature dataseveral times a day throughout the year.

�Once someone figures out what ValLaMarche had in mind, they�ll havetemperature readings from right on-site,rather than from the airport in Bishop,California,� Harlan said.

The funding will allow similarexpeditions for the next two summers.The project also furthers the research ofUA students. Linah Ababneh, an EmilHaury Scholar from Jordan who isworking on her Ph.D., is seeking todetect the effect of increased carbondioxide and nitrogen on subalpine forestecosystems, comparing bristlecone pinein the White Mountains with foxtail pinein the Sierra Nevadas in California.

Ababneh is testing a LaMarchehypothesis that greater atmosphericcarbon dioxide levels can have an effecton growth that goes beyond temperatureand precipitation. The bristlecone pinesamples show wider rings since aboutthe mid-1970s, which a ground-breakingand still-controversial 1984 paper byLaMarche and colleagues attributed tocarbon dioxide fertilization. Ababnehplans to use stable isotopes of carbonand nitrogen to consider the respectiveinfluence of their atmospheric counter-parts. She is excited about her work.

�I am building upon Dr. Haury�slegacy. He said that the science ofdendroarchaeology might have contrib-uted the most significant advances in thearchaeology of the Southwest,� she said.�I follow in his footsteps, and suggestthat tree rings and dendrochronology willprovide the most significant advances inunderstanding greenhouses gases inforest ecosystems.�

Extension of thebristlecone pinechronology will be animportant contributionto current efforts atcalibrating the carbon-14 dating technique inthe period immediatelyafter the last Ice Age.

Greg Lazear�s tree-ring computer datingprogram, refined andfield-tested, may proveto be another one ofthe project�s contribu-tions to the tree-ringscience community,Harlan believes.

The programautomates crossdatingof �skeleton plots� �the graphical repre-sentation of thepattern of narrowringsfound in a piece ofwood � thus allowingcomputerized matchingwith existing chronologies.

This will helpdendro-chronologiststo more efficientlydevelop skeleton plotsand to date exceptionallylong chronologies like those frombristlecone.

Thanks to a generous donor, Harlanand others will have more opportunity toexpand a grand scientific endeavor.

�The White Mountains are ex-tremely large and we have worked inonly a small part of them,� Harlannoted. �There�s always the next ridgeover.�

For more information, contact TomHarlan at 520-885-4194 orstrider@throneworld.com.

LTRR researchers Rex Adams, second from left,Thomas Harlan, fourth from left, and Linah Ababneh,third from right, take a lunch break with some of thevolunteers and USFS rangers who worked on thebristlecone project this past summer.

NOVA features

bristlecone pinesA NOVA program on the

Methuselah Tree bristlecone isshowing nationally in December.Schulman�s discovery is highlightedand Tom Harlan is interviewed inthe program. Tucson�s KUAT(Channel 6) will air this program at 9p.m. on Feb. 26.

For more information on theprogram and on bristlecone pines ingeneral, go to the following web site:http://www.pbs.org/wgbh/nova/methuselah/textindex.html

Photo courtesy of Tom Harlan

Behind the woodshedAn irreverentmicroanatomicalview of life atthe LTRRBy Steve Leavitt

With a department that promi-nently displays the word �Research�in its title, one might think the role ofteaching is secondary. However,even from its inception, the labora-tory has maintained a prominentpedagogic profile through courseofferings related to dendrochronologyand through mentoring graduatestudents and guiding their tree-ring-related thesis projects.

The decade of the 1990sushered in a new era of expandedteaching by Laboratory of Tree-RingResearch faculty in the university�slower division general educationprogram and first-year colloquiumcourses.

One of the most interesting andfulfilling aspects of teaching is that welearn as well from our students.Amazingly, in the freshman-sopho-more classes largely comprised ofnon-science majors, these lessons aresometimes contrary to what we havebeen led to believe are currentscientific facts and paradigms.

Sometimes our lessons in �newscience� (maybe akin to �new math,�but without the grounding in reality)are administered with a healthy doseof �new writing,� which makes theexperience even more holistic andexciting.

How could I forget such essayclassics as �the higher amounts of

carbon dioxide found in the futurewill be circulated through volcanicactivity which could have its ownharmful effects on those areas,� orthe riveting �(photosynthesis is) theprocess in which plants turn their�energy� into oxygen in which we useto breathe,� or the scintillating�millions of years ago the Earth wasnot nearly as hot as it is now. That isbecause of high fertility birth rate inwoman. The more people you haveon Earth, the hotter it will become.�?

Now, let�s suspend disbeliefeven further and imagine that A.E.Douglass had been enlisted intoteaching general education classes(of which I expect he would do a finejob). He had dutifully taken alongthe final exam papers to readbetween field activities of the SecondBeam Expedition near the Whippleruin.

Through four days he had readthe first 38 essays about �how treerings could be a research tool inunderstanding wide-scale (read

�global�) change.� In the evening ofthat fateful 5th day of excavations onJune 22, 1929, with his head alreadybeginning to throb from the cumula-tive effects of grading, he pulled outan unassuming exam, no. 39.

Under the flickering kerosenelamp he read the following propheticpassage from a student identified 70years later only by the initials�SWL�

�There are vegetarions calledtrees that grow in many places suchas forests and Canada. Inside thetrees are circles like the hard waterdeposits in a flea market sink. Theseare called tree rings and according toold wives� tales say they show howold the tree is when they are counted.They form from bark, and theyexpand and contract to different sizeslike the �one-size-fits-all� second-handcummerbunds at a flea markettuxedo stand. As they shrink andswell, the volume of the atmospherechanges and more ozone layerreaches the surface and changestemperatures.�

Of course, there is a remotepossibility this student was not inclass the day that subject wascovered, or perhaps was distracted inclass (read �sleeping�).

Either way, dare I sayDouglass� headache may havebecome chronic, he may have beenunable to look at the Whipple tree-ring samples du jour (perhaps evenchanging profession on June 23rd toselling maps to the stars� [homes] inHollywood), and the tree-ringuniverse as we know it might neverhave evolved.

To coin a phrase for the bravenew lexicon, this would have been�tragidipitous,� a descriptor unintelli-gible but oddly familiar � well, likethe interminable banter of a fleamarket time-share salesman.

Steve W. Leavitt, professor ofdendrochronology, scouts loftytimber that needs to be taken down apeg (provided he doesn�t have to goto PC re-education camp as a resultof what he writes).

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Photo by Melanie Lenart

Wish ListMexico cliff dwellings

The little-known cliff dwellings of northernMexico have tremendous potential for the developmentof dendrochronology in Mexico. Quite similar to thefamous cliff dwellings of Mesa Verde, these structuresare located in remote areas of the Sierra MadreOccidental and have received very little archaeologicalor dendrochronological attention, yet they containrelatively undisturbed roof timbers amenable todendroarchaeological research. These sites cancontribute important data for developing centuries-longtree-ring chronologies in the area and region.

LTRR adjunct assistant professor Ron Townerhopes to expand archaeological tree-ring dating intonorthern Mexico via projects focused on these cliffdwellings. The amount needed for a small pilot project($10,000 to 15,000) would facilitate sample collectionand analysis for some of the more accessible sites inthe area and would help attract additional funds forfuture large-scale projects.

Dr. Towner can be contacted at 520-621-6465 orrtowner@LTRR.arizonza.edu.

Tree rings in the tropicsTree-ring work in the tropics is very difficult because

many tropical tree species do not develop clearly visibleannual rings. Nevertheless large, old tropical trees do existand they may be a valuable resource for paleoclimatology �especially the study of El Niño behavior before and after theIndustrial Revolution, when atmospheric greenhouse gasconcentrations began their current and rapid rise.

Our recent pilot project shows that the seasonal cyclecan be resolved using measurements of stable isotopes intropical trees � even those that completely lack rings. Hencea group led by the LTRR�s new assistant professor, MichaelN. Evans, is seeking funding (~$5,000) for an expedition tocollect samples from the lowland forests of western equatorialSouth America � a region where rainfall varies almost solelywith El Niño activity.

Data developed may provide important evidence forwhether recent El Niño behavior is part of the norm, orinstead is another component of the increasingly clearfingerprint of global warming.

Dr. Evans can be reached at 520-626-2897 ormevans@LTRR.arizona.edu.

To see the Tree-Ring Times in full color, go to the LTRR�s home page at http://www.ltrr.arizona.edu/

Laboratory of Tree-Ring ResearchP.O. Box 210058Tucson, AZ 85721-0058

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