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The International
Tree-Ring Data Bank
Introduction
to the ITRDB
Purpose
of the ITRDB
Requirements
of Tree-Ring Data Submitted to the ITRDB
Holdings
of the ITRDB
Administration
of the ITRDB
The
Future of the
ITRDB
Acknowledgements
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
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
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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.
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).
Recently,
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
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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.
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.
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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. |
