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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?

Douglas-fir

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.

Douglas-fir

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.

Douglas-fir

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!

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The International Tree-Ring Data Bank 

Access the Search Engine for the ITRDB

 

Introduction

Dendrochronology and its related subfields (e.g., dendroecology and dendroclimatology) have proven invaluable disciplines for investigating spatial and temporal aspects of processes in the earth sciences that operate at annual to centennial time scales. Dendrochronology is currently practiced worldwide in laboratories at academic, government-funded, and private institutions by nearly one thousand practitioners, which has resulted in the development of thousands of tree-ring chronologies from sites around the world. These data sets are increasingly being used to assess past changes in Holocene climate to place the global dynamics of present and future climate change in historical context. Recent, intensive efforts have focused on the development of millennium-length tree-ring chronologies to investigate not only short-term, intradecadal (<10 years) trends in past climate, but also longer-term, centennial scale (>100 years) secular trends. Spatial networks or grids of tree-ring chronologies have been or are currently being developed to provide information about past climate on regional and global spatial scales. These efforts allow researchers to (1) develop and test new hypotheses that investigate the effects changes in regional and global-scale atmospheric circulation processes could have on human behavior, pattern, adaptation, and response, and (2) place current changes in global climate processes, often attributed to anthropogenic influences, in context with previous changes in past climate.

The Search Engine Page of the ITRDB

The rapid development of large numbers of tree-ring chronologies across the globe was addressed by dendrochronologists attending a workshop in 1974, who subsequently established the International Tree-Ring Data Bank (ITRDB), a professional organization that provides the only central repository for all types of dendrochronological data from around the world. For years, the ITRDB operated exclusively as a "grass roots" organization, largely dependent on the time and efforts of volunteers. Modest funding was supplied by the United States National Science Foundation as a supplement to research support for Dr. Harold C. Fritts, the founder of the ITRDB, at the Laboratory of Tree-Ring Research, The University of Arizona. In 1990, the Paleoclimatology Program of the National Oceanic and Atmospheric Administration (NOAA) took over the operation of the ITRDB with the establishment of the World Data Center - A for Paleoclimatology at the National Geophysical Data Center (NGDC) in Boulder, Colorado, USA. This center houses many different types of paleoclimatic data, such as ice core, sedimentary, tree-ring, palaeobiological, pollen, and documentary data. With continued support from the Paleoclimatology Program, the ITRDB has established itself firmly in the scientific community as one of the premier paleoclimatic databases.

 

Purpose

The primary purpose for the ITRDB is to provide a permanent location for the storage of well-dated, high-quality dendrochronological data from around the world. This central repository protects data from loss due to: (1) mishandling of tree-ring data, (2) the relocation or termination of laboratories, (3) scientists who move to other projects or retire, or (4) the death of scientists. Besides providing secure storage of the original basic tree-ring information (the actual dated measurements and derived chronologies), the ITRDB is also an increasingly valuable archive of well-dated baseline information on the world's oldest trees, thus providing environmental information before anthropogenic changes became pervasive. As more forests are harvested or restructured due to human intervention, the information in such a database could provide the only surviving long-term record from some of the world's more threatened regions. Such information may be critical for evaluating anthropogenically-induced climatic change, its magnitude, and extent, as well as for reconstructing past climates. Thus, expansion and maintenance of the basic tree-ring data housed in the ITRDB could well assume a greater importance in the coming years.

Results from an ITRDB Search

 

Requirements

Tree-ring data submitted to the ITRDB must meet certain requirements before assimilation into the holdings. First, each tree-ring chronology must have been developed from at least 10 trees. Second, the minimum length of the final chronology should be at least 100 years. Third, the ITRDB requests contributions of the original tree-ring measurements used to develop the final master chronologies. We make this request to ensure that original measurements are available in the future should new methods and techniques be developed. Fourth, it is expected that the series have undergone intense scrutiny by the principal investigator to ensure all individual series are correctly crossdated, and that errors during measurement have been minimized. Finally, all necessary documentation must be delivered to the ITRDB (for example, all site data or information on publications that used the data) to ensure as much information is archived as possible. Under special circumstances, these requirements can be waived when samples are too few and scarce (as, for example, with archaeological tree-ring material), or when the data were developed for extremely detailed analyses (as, for example, in stem growth analyses).

In the mid- to late 1990s, the ITRDB completed a massive, two-year quality control assessment of its holdings of raw measurement data sets for nearly 1,300 sites. This assessment was necessary to ensure that (1) all data files were completely and accurately documented, (2) all data files were in standard Decadal (measurement) and Index (chronology) formats, and (3) all individual series were accurately crossdated. Using a modified version of the computer program COFECHA (Holmes 1983), results of the crossdating accuracy tests were output to separate text files that will provide non-dendrochronologists with an impartial assessment of the quality of the data sets. These text files are now included in the holdings of the ITRDB. The ITRDB is currently developing guidelines for crossdating accuracy to be used by NOAA personnel, and will soon be confirming the accuracy of crossdating for all new contributions.

 

Holdings of the ITRDB

Currently, the ITRDB contains over 6,000 data sets, including 2,804 raw measurement files, 3,275 tree-ring chronologies, and numerous climate reconstructions derived from these tree-ring data. These data were collected from over 1,500 sites around the world representing over 100 tree and shrub species. All final chronology files contain necessary site information and documentation, such as location (site name, state/province, country, latitude and longitude), elevation, species analyzed, specific site characteristics, source of materials (living trees, historical sites), number of trees sampled, type of samples (cores, cross-sections), type and unit of measurement, general chronology statistics (if submitted), and names of the principal investigators. The contribution of separate text files containing even more detailed information is especially encouraged. The tree-ring measurements represent mostly total ring widths, but numerous data sets consist of earlywood and latewood widths, as well as minimum earlywood and maximum latewood densities, and new ring characteristics have been contributed derived from digital image analyses.

As part of the World Data Center system, the ITRDB makes its holdings freely available to any and all researchers. It is more important to stress that the collective data are shared around the world when they are submitted to the ITRDB. All newly-contributed tree-ring data are archived by personnel at the National Geophysical Data Center in Boulder, Colorado. Membership in the ITRDB is automatic for those individuals and institutions that contribute dendrochronological data. Currently, the ITRDB has 139 members from 21 countries: Argentina, Australia, Belgium, Canada, The Czech Republic, Finland, France, Germany, Italy, Japan, Lithuania, Mexico, The Netherlands, New Zealand, Poland, Russia, Slovenia, Sweden, Switzerland, the United Kingdom, and the United States.

 

Administration of the ITRDB

An Advisory Committee of dendrochronologists administers the ITRDB and consists of a chairperson and individuals selected from its members. In 1994, committee membership was expanded to provide a wider geographic coverage among dendrochronologists, and to also provide representation for the numerous subdisciplines within the science. This Advisory Committee assures that the ITRDB keeps pace with new developments in dendrochronology, and has the special function of reporting annually to NOAA on the functioning of the organization.

Drought: A Paleo Perspective

The Future of the ITRDB

The primary purpose of the ITRDB is to assimilate tree-ring measurement and chronology data into a central location for permanent archiving. In the past, solicitation efforts concentrated on tree-ring data useful for climate reconstruction purposes. As scientists applied tree-ring data to more and more different types of studies, however, the ITRDB realized this view was too narrow - tree-ring data developed for non-climatic purposes were being overlooked. The ITRDB has since relaxed this requirement to allow contributions of all types of tree-ring data. New data types that have been or will be assimilated include: (1) isotopic measurements of hydrogen, carbon, and oxygen, (2) information on cellular structure (e.g., cell wall thickness and cell wall area measurements), (3) data from stem analyses, (4) data gathered from image analyses, and (5) data from event chronologies (e.g., frost ring chronologies). Tree-ring chronologies developed for reconstructions of disturbance regimes (for example, spruce budworm outbreaks) will also be included in the holdings of the ITRDB. These data files should have special text files included that discuss the unique nature of the study for which these data were developed. The ITRDB will also increase its solicitation for actual climate reconstructions developed from tree-ring data.

Another major goal of the ITRDB is to increase awareness among dendrochronologists concerning the role of the ITRDB in its relationship with the World Data Center system and the International Council of Scientific Unions (ICSU). We would like to clarify to the worldwide dendrochronological community the guidelines established for the WDCs, and how these guidelines apply to the ITRDB and to the availability of tree-ring data. In the coming years, the Advisory Committee of the ITRDB will begin developing preliminary guidelines for the ITRDB that clearly state its mission and purpose, responsibilities, requirements, and policies regarding data submission and distribution. Hopefully, these guidelines will be published in a future edition of the Guide to the World Data Center System by the ICSU. We feel this is a critically important step to facilitating the steady flow of tree-ring data to the ITRDB and the WDC-A for Paleoclimatology. The proposed improvements to the ITRDB will initiate and facilitate processes that will lead to mutually agreeable guidelines representing the consensus of dendrochronologists worldwide.

 

Acknowledgements

The ITRDB graciously thanks those who, over the years, provided continuous support for our efforts by contributing their valuable tree-ring data, which will serve generations of future researchers in years to come. We especially thank Richard Holmes for his continuous involvement with development of the ITRDB Program Library, often on his own time, and for his steadfast support for the ITRDB mission. Special thanks to Mariette Seklecki who laboriously executed nearly two thousand runs of COFECHA, and prepared all documentation and computer files during the quality control assessment. Generous support for the ITRDB database efforts was supplied for many years by the Paleoclimatology Program of the National Oceanic and Atmospheric Administration, and to them we are very grateful. Finally, we would be remiss if we did not acknowledge the long standing and continued support of the Laboratory of Tree-Ring Research, The University of Arizona, since the inception of the ITRDB. The ITRDB would not have survived these many years without this backing, and the Laboratory has and continues to play a significant part through supporting facilities, faculty salaries, and other personnel time for many different aspects of this undertaking.

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