Dendrochronology:

1
Dendrochronology A fusion of science and history.
Jason S. Chambers, Senior Biology Major, Dr.
Daniel Druckenbrod, Assistant Professor, Longwood
University, Farmville, Virginia
Skeleton Plotting and Measuring
Study Site
Introduction
This study utilized the foundations of
dendrochronology in order to date the
construction of a supposed pre-Civil War
structure. Core samples and cross-sections were
obtained from Oak, genera Quercus, building logs
and analyzed to either confirm or refute the date
of construction.
The structure under scrutiny is located on a farm
purchased in 2003 by Doctors Clifford and Rebecca
Ambers located in Amherst County, Virginia. A
deed search on the property can trace ownership
back to the year 1770 however it is unclear as
to the exact date the structure was built on the
property (See Fig 2).
(Fig.5)A skeleton plot of a core sample
The next step was skeleton plotting. In this
process a core or a cross-section is viewed
through and microscope and each ring is evaluated
on its width relative to rings located around ten
rings away. A skeleton plot is made by marking a
longer vertical line for more narrow rings and a
B for very wide rings on the corresponding year
on the plot (See Fig.5). Once several samples
have been plotted the plots can be aligned in
hopes of creating a master chronology for the
sample site. Once several cores and
cross-sections were plotted using this method,
the samples were then measured using a Velmex
measuring station, to an accuracy of 1000ths of a
millimeter. The ring width indices were then
loaded into statistical programs in order to
verify that the skeleton plots were correctly
crossdated.
According to Dr. Neiman, an architectural
archeologist at Monticello, structures such as
these that dot rural landscapes in this state are
difficult to impossible to date using building
style alone. This is due to the simplicity of one
building style and availability of supplies
during pre and post Civil War rural America.
Thus, this is why dendrochronology is
Definitions

• Following are several definitions that are
  pertinent not only to our study but to the field
  of dendrochronology itself as defined by Fritts
  (2001).
• Dendrochronolgy The science that deals with the
  dating and study of annual growth layers in wood
• Ring-width chronology The averaged
  standardized ring-width indices from a number of
  trees sampled from a particular site which can be
  used for cross-dating and deducing past climate.
• Crossdating The procedure of matching
  ring-width variations and other structural
  characteristics among trees that have grown in
  nearby areas, allowing the identification of the
  exact year in which each ring was formed.
• Signal A detectable quality, pattern or
  variation in a time series such as ring widths
  which can be attributed to meaningful information
  on climate, environment, or biological conditions
  of trees, as opposed to the background variations
  or noise which provide no information about the
  trees and their environment.
• Earlywood The wood produced in the annual
  ring during the early part of the growing season,
  characterized by large thin-walled cells.
  Earlywood is more porous the latewood and often
  lighter in color. Sometimes referred to as
  springwood. (See Fig. 1)
• Latewood Dense and often dark wood produced
  in the annual ring during the later part of the
  growing season, characterized by small,
  thick-walled cells. Also referred to as
  summerwood. (See Fig. 1)

(Fig 2)Back of structure in Amherst County,
Virginia
the dating method of choice, for structures such
as these. The structure has undergone several
additions and modifications over the generations.
Samples then were taken only from foundation and
primary construction logs, to limit erroneous
dating.
Results
Coring and Sample Preparation
The first process that was performed at the site
was the identification of ideal sample logs.
Questions that were assessed include 1) is the
log part of the primary structure, 2) is the end
of the log visible to obtain the orientation of
the log and its center, and 3) is there bark on
the outside of the log or does the
outer surface appear intact (or does it appear to
have been split). Once an ideal sample log was
identified the next step was coring. Core
samples were obtained by using a power drill and
a specialized hollow bit. The drill bit allowed
for much more efficient sampling than hand corers
would due to the hard dried wood of the structure
(See Fig.3).
(Fig.6)Ring width indices showing sensitivity and
crossdating
(Fig.3)Core sampling using a drill and
specialized bit
Acknowledgments
Cross-sections were obtained using a chainsaw.
Once back in the lab the samples were mounted and
then sanded extensively. Sanding was done in a
stepwise fashion down to a grit size of nine
microns (See Fig.4)
The authors of this poster would like to thank
the following people and departments for all of
their help and support Clifford and Rebecca
Ambers, The Longwood University Faculty Research
Grant, Dr. Neiman, and the Department of Natural
Sciences at Longwood University.
Fritts, H.C. (2001). Tree Rings and Climate. The
Blackburn Press. Caldwell, New Jersey.
(Fig.4)A mounted and sanded core sample
(Fig. 1)Cross-section of an oak log under a
microscope early and late wood labeled