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Eastern Hemlock

Latin name:
Tsuga canadensis

Extracted from a waterfront pier near Wilmington, Delaware, the tree used to make this portion of the pier
actually came from a forest located in central Pennsylvania. The outermost tree ring dates to the late 1830s.

Giant Sequoia

Latin name:
Sequoiadendron giganteum

A close up of numerous fire scars on a giant sequoia cross section from Sequoia National Park in California, dating back well prior to A.D. 1000. Look closely! Can you find the sad bearded face cradled by his hands, as if he was crying?


Latin name:
Pseudotsuga menziesii

This photo shows the tree rings from a beam extracted many years ago from a pueblo in northeastern Arizona. The section shows many false rings and many micro-rings, suggesting this tree may have been growing in a marginal environment.

Ponderosa Pine

Latin name:
Pinus ponderosa

Close up of tree rings of a ponderosa pine collected at El Malpais National Monument in New Mexico, USA, showing tree rings centered around A.D. 1400. Notice the variability in ring widths indicative of sensitivity to year-to-year variation in precipitation.


Latin name:
Pseudotsuga menziesii

Perhaps my most requested image of tree rings, obtained from a small Douglas-fir growing in the Zuni Mountains of west-central New Mexico by my colleagues Rex Adams and Chris Baisan. Not very old, but has some of the most beautiful rings of all my displays!

White Oak

Latin name:
Quercus alba

Oak cores from the Hoskins House in Greensboro, North Carolina, site of a famous battle during the Revolutionary War. The house was built from trees cut in 1811 to 1813, not cut and built in the 1780s as the historical agency had hoped.

Ponderosa Pine

Latin name:
Pinus ponderosa

This ponderosa pine once grew at El Morro National Monument in New Mexico, USA, and was cut many years ago. Once you get up close to the stump, you can see a very old scar from a fire many hundreds of years ago that scarred the tree when it only about 12 years old!

Bahamian Pine

Latin name:
Pinus caribaea var. bahamensis

We collected many cross sections of Bahamian pines that had been cut for an industrial park on the island of Abaco, but the rings are very difficult to date! Many false rings, and the pine appears to terminate tree growth during the dry season.

Longleaf Pine

Latin name:
Pinus palustris

This cross section was one of many that came from an old crib dam across a creek that was exposed after a modern dam broke in Hope Mills, North Carolina in 2003. Such sections from old-growth longleaf pines are very rare and provide information on climate back to AD 1500!

White Oak

Latin name:
Quercus alba

Sometimes you don't have to look far to find beauty in wood, and sometimes it may not be a living tree! After an oak tree was cut a year or two before this section was obtained, decay fungi had already set in, beginning to break the wood down to its basic elements.

Southwestern White Pine

Latin name:
Pinus strobiformis

I collected this fire-scarred pine on Mt. Graham in southern Arizona in fall 1991, and it remains one of the best examples of how we can determine the season of fire by looking at the position of the scar within the ring.

Bristlecone Pine

Latin name:
Pinus longaeva

Bristlecone pines have become one of the best proxy records for those who study the history of volcanic eruptions because the cool temperatures caused by these eruptions create "frost rings" that form when the cells implode from the cold.

Eastern Redcedar

Latin name:
Juniperus virginiana

Many well-preserved eastern redcedar sections have been recovered from prehistoric sites in eastern Tennessee, and they have more than enough rings to date, but we don't have a long enough living-tree reference chronology to overlap with them!

Red Oak

Latin name:
Quercus rubra

Oak is by far the most common genus we find in the many historic structures we date using tree rings in the Southeastern U.S. The genus has good ring variability and rarely has problem rings. This section came from a historic tavern in Lexington, Virginia.

Sugar Maple

Latin name:
Acer saccharum

Maple, birch, beech, and basswood are all examples of hardwood species that form diffuse porous wood, meaning that the ring contains many small-diameter vessels all through the ring. Identifying the ring boundary on this wood type is a challenge to tree-ring scientists.

Live Oak

Latin name:
Quercus virginiana

Live oak is an example of an evergreen oak, which is not common within this genus. As such, the wood is semi-ring porous and the rings are very difficult to see and date. Ring growth is also very erratic, not forming the concentric around the tree that we require.


Latin name:
Pseudotsuga menziesii

These cores were collected on Mt. Graham in southern Arizona and show a major suppression event beginning in 1685 when missing rings became evident, followed by many micro-rings. This suppression was caused by a major wildfire in 1685!

Ponderosa Pine

Latin name:
Pinus ponderosa

I find it amazing what trees can record in their tree rings! Here we see a cross section of a pine that was damaged by a major flood in the year 1945 in the Chiricahua Mountains of southern Arizona. Notice the reaction wood that formed afterward.

Pignut Hickory

Latin name:
Carya glabra

Sometimes gray-scale imagery helps define tree rings when measuring. Although classified as "ring porous" species, the rather ill-defined tree rings in hickory tree species form large earlywood vessels and smaller latewoood vessels.

Subalpine Fir

Latin name:
Abies lasiocarpa

Decay has set in on the tree rings of this dead and downed subalpine fir that once grew on Apex Mountain in British Columbia, Canada, but the tree rings can still be measured and crossdated despite this!

White Fir

Latin name:
Abies concolor

We found a beautiful fire scar on this white fir that was used to build a cabin in the Valles Caldera of New Mexico. Thought to have been built in the early 1900s, we instead found the cabin was built form white fir and Douglas-fir trees cut in 1941.

Overcup Oak

Latin name:
Quercus lyrata

These oak cores were collected in northeastern Arkansas to investigate a change in the hydrologic regime of a wildlife refuge beginning in the 1990s. We found that trees at this site experienced a major disturbance event in the 1960s.

Western Juniper

Latin name:
Juniperus occidentalis

Near Frederick Butte in central Oregon, we discovered an unusual stand of western junipers that had the most unusual lobate growth forms we had ever seen. This site yielded a drought-sensitive chronology dating back to the AD 800s!

West Indies Pine

Latin name:
Pinus occidentalis

Above 3000 meters on the highest peak in the Carribean, we found an entire forest of these pines, many with fire scars, living on a steep rocky slope. The forest looked more like the dry ponderosa pine forests of the western U.S.

Whitebark Pine

Latin name:
Pinus albicaulis

Whitebark pines growing in the northern Rockies of the western U.S. can grow to be over 1,000 years old, but the species is slowly being decimated by the introduced white pine blister rust. Many of these ancient trees are now dead with ghostly white trunks.

Shagbark Hickory

Latin name:
Carya ovata

Curiously, tree-ring scientists rarely analyze some of the more common hardwood species in the eastern U.S., such as this hickory, perhaps because such forest interior trees may contain a weak climate signal necessary for crossdating.

Virginia Pine

Latin name:
Pinus virginiana

Blue stain found in many sections of dead pines (both in the western and eastern U.S.) is caused by a fungus carried by a pine beetle. The fungus spreads into the phloem and sapwood of living and dead pines, sometimes creating stunning patterns!

Pinyon Pine

Latin name:
Pinus edulis

Burned sections of pinyon pine are commonly found in archaeological sites in the southwestern U.S. These sections can be carefully broken or surfaced with a razor to reveal the ring structure inside to assist in dating the years of construction of the site.

Red Spruce

Latin name:
Picea rubens

Conifers in the highest elevations of the Appalachians of the eastern U.S., such as this red spruce, don't experience wildfires very often, but when fires do occur, they can create numerous fire scars even in this fire-intolerant species. Notice the growth release!

White Spruce

Latin name:
Picea glauca

This tree was located in the Canadian Rockies on the toe slope of an active avalanche path. The scar was created by a debris flow or snow avalanche which struck the tree, killing a section of the living tissue. The avalanche can therefore be dated to its exact year!

Engelmann Spruce

Latin name:
Picea engelmannii

I worked considerably in the spruce-fir forests of southern Arizona in my earliest years in dendrochronology, and learned that trees with limited sensitivity can provide a vast amount of information on the history of these forests.

Ponderosa Pine

Latin name:
Pinus ponderosa

The lava flows of El Malpais National Monument in New Mexico contain vast amounts of remnant wood, mostly ponderosa pines such as this sample, and the tree rings on these samples go back nearly 2000 years! Notice the year AD 1400 on this section.

Chestnut Oak

Latin name:
Quercus montana

In the southeastern U.S., hardwood species are often scarred by wildfire. Most often, this also will cause considerable decay in the sample, but this oak had several well preserved fire scars, suggesting fire was common in these drier, lower elevation sites.

Ponderosa Pine

Latin name:
Pinus ponderosa

I originally sampled this stump in 1991 for its fire scars, located in El Malpais National Monument of New Mexico. I found it again 20 years later and was happy you could still see the tree rings and fire scars clearly! It had originally been logged in the 1930s!

Lodgepole Pine

Latin name:
Pinus contorta

This pine is found at higher elevations in the Rocky Mountains of the western U.S. At this site in Montana, we had thought we found fire scars on these pines, but it turns out that these are scars caused by bark beetles stripping away portions of the bark.


Latin name:
Pseudotsuga menziesii

These cores illustrate the level of sensitivity to climate fluctuations in Douglas-fir trees growing in El Malpais National Monument in New Mexico. These rings show the common pattern of narrow marker rings between 1800 (on the left) and 1860 (on the right).


Latin name:
Pseudotsuga menziesii

This photo shows a close-up of the rings in the previous image. The very wide tree ring is the year 1816, the "Year Without a Summer." Cooler temperatures meant more soil water for the malpais Douglas-firs, causing a wide ring for that year!

Ponderosa Pine

Latin name:
Pinus ponderosa

Dating fire scars found in the annual rings is a major application of tree-ring dating. This photo shows two scars. Notice the wider rings that formed after the upper scar, perhaps caused by removal of competing vegetation or added nutrients.

Longleaf Pine

Latin name:
Pinus palustris

Longleaf pines have the greatest ages of all the eastern pines. They grow slowly in sandy soils of the Atlantic Coastal Plain, and have proven ideal for learning about past climate and disturbance events, if old-growth stands can be located!

Rocky Mountain Juniper

Latin name:
Juniperus scopulorum

The juniper species of the western U.S. have proven a challenge in tree-ring dating, but Rocky Mountain juniper has tree rings that are easily identified and can be crossdated. Just watch out for false rings and expanded latewood!


Latin name:
Pseudotsuga menziesii

A close-up photo of tree rings in Douglas-fir reveals the individual wood cells that make up the xylem. These are called "tracheids." Notice the change in cell wall thickness from the earlywood cells to the latewood cells along a radial file of cells.


Latin name:
Pseudotsuga menziesii

The best trees for learning about past climate will be those that grow to great ages and are particularly sensitive to year to year changes in climate. This Douglas-fir began growing around the year 200 BC and lived for nearly 1000 years!


Latin name:
Prosopis glandulosa

Some desert species from the mid-latitudes do form annual rings, but these diffuse-porous species have rings that are difficult to see. You can use black marker and white chalk dust to help bring out the rings! The dust fills the small vessels and the rings appear!

Norway Spruce

Latin name:
Picea abies

Spruce is the preferred genus for making high-quality wooden bodies on musical instruments. This photo shows the tree rings on the outer edge of the "Messiah" violin. Analysis of its tree rings helped show that the violin was contemporary with Stradivari!

Black Locust

Latin name:
Robinia pseudoacacia

In the eastern U.S., this common hardwood species has beautiful tree rings that demonstrate the ring porous wood type. The tree species, however, has some of the densest wood found in North America and is extremely difficult to core!

White Oak

Latin name:
Quercus alba

Oak is a major genus used to build log structures in the eastern U.S. Sometimes, however, we find that the individual trees experienced some major disturbances that caused very aberrant rings, making crossdating all but impossible.

Palo Verde

Latin name:
Parkinsonia florida

A common tree species in the American Southwest, palo verde is a diffuse porous species that forms very indistinct tree rings. As a result, little tree-ring research has been performed on this genus. Best to use complete cross sections, when available.

Ponderosa Pine

Latin name:
Pinus ponderosa

A major application of tree-ring research is learning about insect populations. For example, pandora moth defoliated the needles on this tree, causing some narrow rings to be produced. We can use this pattern to learn about insect populations over many centuries!

Table Mountain Pine

Latin name:
Pinus pungens

The analysis of fire scars in tree rings can also be applied to pine species growing in the eastern U.S. Table Mountain pine has proven to be the best species in the Appalachian Mountains for learning about past wildfires!

Subalpine Fir

Latin name:
Abies lasiocarpa

Subalpine fir grows in the highest elevations of the southern Rocky Mountains and forms fairly compacent ring series. Sometime between 1979 and 1980, this tree was stripped almost completely of its bark by a black bear, but it still survived in one small area!

Florida Torreya

Latin name:
Torreya taxifolia

Perhaps the rarest conifer in the U.S., this species is on the brink of extinction because its habitat is facing mounting pressure from rapid changes in its native environment. It forms very nice tree rings, but few adult individuals are left to analyze.

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get in touch

Henri's Page


July 2015. I'm sawing into an ancient log in the Beartooth Mountains of northwestern Wyoming. This whitebark pine likely began growing well prior to AD 1000, thrived during the Medieval Climatic Optimum (AD 1100 to 1400), but then succumbed to intense cold temperatures and snow and ice build-up in the middle 1700s during the Little Ice Age (AD 1400 to 1800). Notice no other such large trees exist there today, only smaller and younger whitebark pine trees that established after the snow and ice had completely receded from the area in the last 300 years. Using dendrochronology, not only can we learn what climate was like for this area over the past 1300 years, but we can also gain some insights on how climate affected the history of the forests that once lived here.

My Curriculum Vitae


How to contact me:

Henri D. Grissino-Mayer
Department of Geography
417 Burchfiel Geography Building
The University of Tennessee
Knoxville, Tennessee 37996-0925 U.S.A.
865 974-6029 (office)
865 974-6025 (fax)
grissino [at] utk [dot] edu

Personal Stuff

Place/date of birth: Monterey, California, December 24, 1954
Home Address: Knoxville, Tennessee, U.S.A.
Hobbies: Hiking and backpacking, camping, collecting old and rare books, trees, rescuing cats
Family: In July 2011, I married Brandi Boggs and we share a beautiful house with her three children (Maya, Zaen, and Alex), our new son Noah, along with our 11 cats and ___ dogs (you get to fill in the blank).

Teaching Interests

After eight long years as an Assistant Professor and six years as an Associate Professor, I was finally promoted to Full Professor in August 2011 at the University of Tennessee in Knoxville. My expertise focuses on and dendrochronology, paleoclimatology, and fire ecology, but I also have a fair background in quantitative methods, biogeography, geomorphology, natural and human hazards, soil science and soil geography, and geographic thought. I strongly believe that the primary purpose of a university is to educate, and that through research we become better educators. I also believe in the use of new technologies in the classroom, and I am a strong advocate of the use of the Internet and worldwide web to enhance the learning experience.

Teaching Philosophies

  • I believe in collaborative learning that provides ample opportunity for students to become involved in the educational and research processes.

  • I believe that the educational experience should be an enjoyable one.

  • I do not believe in standing in front of a class for one hour and regurgitating material from a textbook.

  • I do not believe in complete isolation during education.

  • I believe in a reasonable student/teacher ratio to ensure individual attention is given to all students.

  • I believe a student should receive the highest quality education in an environment that best suits the student and not the administration.

Research Interests

I remember when I saw my first tree ring - I was a young laddie of but two, and my papa took me to the arboretum. When I saw my first signature pattern, I said "Papa, when I grow up, I want to study forensics and carve up dead bodies." But my wise papa said, "Become a dendrochronologist instead..." My background as a climatologist introduced me to tree-ring research way back in 1985, when I was a masters student at the University of Georgia. My own research concentrates on several areas, listed below. I've been fortunate that my research has been featured in thousands of newspapers worldwide and my students and I have been featured in several television documentaries. Be sure to check out these online published news articles which describe my research!

See Henri featured in video news stories:

UT professor on Chimney Tops 2 report: Residents should be prepared for fires -- WATE-TV, Knoxville, Tennessee
Henri Grissino-Mayer discusses the 2016 Chimney Tops 2 fire -- The University of Tennessee
'Gatlinburg Wildfire Survivors' group demand change at city meeting -- WBIR-TV, Knoxville, Tennessee
UT Professor using award money to warn of wildfires -- WBIR-TV, Knoxville, Tennessee
Gatlinburg fires were "catastrophe waiting to happen" -- WVLT-TV, Knoxville, Tennessee
UT professor warns about fire dangers -- WATE-TV, Knoxville, Tennessee
Fire on the Mountain -- NewsChannel 5, Nashville, Tennessee
Professor predicted Gatlinburg wildfire -- WATE-TV, Knoxville, Tennessee
Tennessee This Week -- WATE-TV, Knoxville, Tennessee
Gatlinburg was made to burn -- CNN International
Knoxville Air Quality -- WBIR-TV, Knoxville, Tennessee
The Stradivarius Mystery -- Weather Channel
The Scream -- Weather Channel
The Year Without a Summer -- Weather Channel
Weather Time Travelers -- Weather Channel
Fredericksburg Crib Dam -- Fredericksburg Free-Lance Star

News stories about Henri and his students:

Wildfire professor bristles at officials' resistance to safety programs  -- Knoxville News Sentinel
Commentary: Act now to prevent another tragedy like Gatlinburg  -- TreeSource
Great Smoky Mountains National Park is 520,000 acres of tinderbox -- Knoxville News Sentinel
South Carolina fire handled much differently than Chimney Tops 2 -- Knoxville News Sentinel
Tennessee schools need to teach geography better  -- The Tennessean
The Brilliance of a Stradivari Violin Might Rest Within Its Wood -- New York Times
After the flames, ‘mountain tough’ Gatlinburg looks to the future -- Washington Post
Gatlinburg’s Inferno: Why It Started, How It Spread, and What Needs to Happen Next -- Knoxville Mercury
'Gatlinburg was made to burn,' professor says -- CNN International
Tennessee college professor predicted Gatlinburg wildfire: Town was ‘made to burn’  -- WNCN
UT Geography Expert: Though Tragic, Gatlinburg Fire was ‘A Safe Prediction’ -- Winchester Herald Chronicle
University Professor Predicted Gatlinburg Wildfire for Years -- FireFighter Nation
Gatlinburg Wildfires Cause 3 Deaths, Hundreds Displaced -- Daily Beacon
University of Tennessee Professor Predicted Gatlinburg Fire for Years  -- Knoxville News Sentinel
Maps at McClung Museum Offer Glimpse into History -- Knoxville News Sentinel
Researchers Use Tree-Ring Science To Study Area Log Cabins -- Watauga Online
Lord of the Rings -- Low Country Weekly
The Bell Tolls for a Tough Old Tree -- Albuquerque Journal
Death of Yoda the 650-Year-Old Tree Tells Tale of Southwest Drought -- NBC News
Shortleaf pine declining without fire in the Smokies -- Knoxville News Sentinel
Without fire, No Name Key could lose its pine forests -- Keynews.com
Dendroarchaeology Expert to Talk Tree-Ring Dating and Historic Structures -- University of Wisconsin-Platteville, University News
The Longest Measure of Drought: 21 Centuries of Rainfall in New Mexico -- NYTimes.com
Timbers from Dam Hold Record of Past -- Fredericksburg Free-Lance Star
Dire Drought Ahead, May Lead to Massive Tree Death -- AAAS EurekAlert
Trees Tell the History of Fire -- National Park Service
Reading history - one ring at a time -- Indiana State University Newsroom
UF, UT Researchers Join Forces to Bring Tree-Ring Dating Technology to Heart of Southeast -- University of Florida News
Dr. Grissino-Mayer to Speak -- Historic City News
UT Pre-Game Faculty Showcase Focuses on Tree Ring Science, Wildfire Predictions in Smokies
UT researchers' work reveals 220-year hurricane history -- Tennessee Today
Tree rings provide a 200-year-old hurricane record -- NSF News
Tree rings could settle global warming hurricane debate -- MongaBay.com
Every tree has a story to tell -- Christian Science Monitor
Did "Little Ice Age" Create Stradivarius Violins' Famous Tone? -- National Geographic News
Does climate explain prized violins' tone? -- MSNBC
£10m violin 'the real thing' -- BBC News
Secret ingredient in Stradivari may be heaven sent -- USA Today
Chill might be Stradivarius secret -- London Free Press
Validity of Stradivari examined -- University of Tennessee Daily Beacon
Climatologist: Georgia unprepared for drought -- Augusta Chronicle
Specialist pushing deliberate burning -- Augusta Chronicle


My Research Reconstructing Climate

First, I use tree rings to reconstruct past climates, accomplished by developing site master tree-ring chronologies, then calibrating recent tree-ring widths with historic climate records. I've concentrated mainly in the southwestern United States, but began my career by reconstructing climate in northeastern Georgia under the direction of Dave Butler.

Some years ago, I developed a 2,129 year long reconstruction of rainfall for northwestern New Mexico. This reconstruction was based on a master chronology developed from some extremely old living trees and remnant wood found in El Malpais National Monument, just south of Grants, New Mexico. The graph below shows a 100-year spline (much like a moving average) fit to the reconstruction to accentuate the century-scale trends in past rainfall. Note, however, that the graph above does not depict decadal scale trends very well...

The graph below, however, was designed to depict shorter-term, decadal-scale trends by using a 25-year spline. Notice that droughts and wet periods that last many years are now shown, such as the drought of the 1950s, which was one of the worst in the last 2,100 years.


My Research on Fire History

Second, I use tree rings to reconstruct past fire regimes by analyzing the fire-scar record contained in many ponderosa pine trees. I was initially involved in fire history research as part of Tom Swetnam's Fire History and Ecology Workgroup at the University of Arizona since about 1989 when I collected my first fire-scarred specimens up on Mt. Graham in the Pinaleño Mountains of southeastern Arizona. A good portion of my dissertation research involved developing chronologies of past fire for several sites at El Malpais National Monument. I found that temporal changes in past fires were linked to global-scale changes in atmospheric circulations patterns that resulted in shifts in the summer monsoon component of Southwestern precipitation. Human-related factors, such as grazing and fire suppression, also had significant impacts on fire regimes, especially ca. 1870-1900.


The Dendrochronology Bibliographic Database

Screen shot of the Bibliography Entry FieldsSince 1986, I've been collecting references about dendrochronology. I now have over 15,000 of these in a computerized bibliographic database that is now searchable via the worldwide web. The database is alphabetically arranged by author, and contains the year of publication, title, source (journal, book, proceedings, etc.), and language information, and also lists keywords that include site information and species used. I have about 13,000 of these in my actual possession, and the collection has been used by researchers from all over the world. I have many rare references as well. If you'd like more information, or you have references you'd like to add, please contact me at my e-mail address below. Also, please send me any reprints of articles related to tree-ring research that you publish so that I may enter these into the database!


Software for Dendrochronology

On the side, I also enjoy programming to make all our lives a little easier. I became involved with the International Tree-Ring Data Bank (ITRDB) in 1988 through Hal Fritts, with whom I continue to work. Since 1991, I've headed the development of the ITRDB Program Library, which has been distributed to over 100 institutes around the world. I've also written FHX2, software for the analysis of fire history from tree-ring data. This software allows researchers to easily enter fire history data, analyze it statistically, graph it, and even plot it. This software has also been distributed widely, and is in use by the USDA Forest Service, the National Park Service, the National Biological Survey, over 50 academic institutions, and in many countries around the world.

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