INTRODUCTION TO DENDROCHRONOLOGY
Dendrochronology is the science that uses tree rings dated to their exact year of formation to analyze temporal and spatial patterns of various processes (biological, physical, or cultural).
Etymology: dendron = tree, chronos = time, logos = the study of
Dendrochronology is a rapidly growing field with many sub-DIsciplines. The two we are primarily interested in include dendroclimatology and dendroecology.
Like any discipline, dendrochronology is governed by a set of fundamental PRINCIPLES. Dr. Henri D. Grissino-Mayer has compiled the principles on his Ultimate Tree Ring Web Pages (NOTE: Use your BACK button to return to this window):
Most of the principles are of course controlled largely by the biology of tree growth and the ecological processes that control that growth (see primer on secondary growth in plants).
BOTANY PRIMER: SECONDARY GROWTH IN PLANTS
Please consult the Primer on Secondary Growth in Woody Plants to refresh yourself on the details of how trees grow, how wood is formed, and basic aspects of tree morphology and wood anatomy.
STATISTICS PRIMER: CORRELATION & REGRESSION
Please consult the Primer on Statistics to refresh yourself on the basic principles of correlation and regression that may be used to analyze tree growth patterns and the relationship of climatic variables to annual growth.
The purpose of this lab is to learn the basic field, lab, and computational procedures necessary to conduct dendrochronological research. In this particular exercise, we wish to examine whether there is a relationship between local climate (precipitation) and tree rings using white oak (Quercus alba) in southeastern Ohio.
Each field team should obtain the appropriate field supplies from their instructor and obtain 3 increment cores from white oak trees at the chosen field site. Please consult Field Methods for a detailed description of the field equipment, including its use and care, and the actual methods of core collection and preservation.
Return your increment cores to the laboratory. The cores should next be mounted and glued in to increment core holders and then the surface prepared for study following the protocols outlined in Lab Methods. Following surface preparation, you can begin the process of crossdating. This is probably the most fundamental and important aspect of tree ring research. In essence, crossdating involves a form of pattern matching. For each core that we have, we need to gain a high confidence in the actual date that we assign to each ring. Unfortunately, any given tree may sometimes have a missing ring or a false ring present and therefore every ring we count thereafter is thrown off by one or two years. However, we can look for certain years that offer good "signals" (very thin or very wide rings) and identify them in each core and confirm they occur at the year they should in each core. The skeleton plot is the tool used to discover these "signal years" and subsequently cross-validate each core for exact dates. Skeleton plotting is a bit of an acquired skill, and there is certainly some art to it. Fortunately, Paul Sheppard has produced an awesome web site that explains the concept of crossdating tree rings and provides an inter-active tutorial for you to practice on to learn the skill. I strongly suggest you follow all the steps at this site and then practice using the tutorial at step 12.
At this point, all of the increment cores have been crossdated and verified and you should have a ring width measurement for every ring in every core that you collected. These data should be entered in to an Excel (or equivalent) spreadsheet for subsequent analysis. Within the file, I suggest forming a separate worksheet for each core. Analysis Methods details the computational steps required to address our question regarding the relationship between climate and ring widths.
The
Ultimate Tree-Ring Web Pages
The name says it all, if you are looking for something
tree-ring related, start here first!
Crossdating
Tree Rings Using Skeleton Plotting
A detailed explanation of the most fundamental aspect
of tree-ring science & excellent interactive tutorial.
Tree-Ring
FAQ
Look here for answers to Frequently Asked Questions.
Pretty comprehensive & excellent info. source.
NCDC
Climate Data Online (pka CLIMVIS)
A NOAA site designed to search for and download
local climate data for your region.
International
Tree-Ring Data Bank
A huge data bank to contribute or retrieve
tree-ring chronologies.
The Laboratory of Tree-Ring Research
This laboratory originated from a paper presented in the Education Section at the Annual Meeting of The Ecological Society of America, Snowbird, Utah, 6-August-2000. The title of the paper was "Dendropedagogy: teaching basic ecological and statistical principles through tree-ring studies" by Brian C. McCarthy and Darrin L. Rubino. With two exceptions, all photographs appearing on this site were taken by Darrin L. Rubino and are copyrighted by him. This site was designed for the immediate use of the Plant Ecology class of Ohio University, but we welcome its use by other students and teachers wishing to learn or communicate the basics of dendrochronology. We welcome your comments and suggestions; please contact Brian C. McCarthy.