Reflected-Light Image Analysis in Dendrochronology
The basis for applying reflected-light image analysis to measurement of
conifer tree rings is as follows: surface brightness is directly related
to the cell lumen:wall ratio, which is inversely related to ring density,
which is then inversely related to surface brightness. Thus, ring
brightness variables may be easily measured and then analyzed dendrochronologically
as ring density.
Image-Analysis System: Here are the components, which are all standard
off-the-shelf items, of my reflected-light image analysis system.
The tree-ring sample is an increment core or cross-section as used normally
in dendrochronology. The sample is illuminated with plain white light,
which is reflected diffusely back to the microscope, which focusses the
image to the ccd video camera. Commercial software on the computer
processes the image, which is displayed on a monitor for the user to see
and measure. Other specialized software converts images to data files
typically used by other dendrochronological programs.
with Brightness Scan: The brightness scan (top) is a composite of all
radial files within each ring (below) without effects of blemishes such
as resin ducts. Ring boundaries and earlywood-latewood boundaries
are determined computationally and verifiable by the system user.
Ring 1 has dark (dense) latewood and a low minimum latewood brightness
value, while Ring 2 has lighter (less dense) latewood and a higher minimum
latewood brightness value. This approach also provides other brightness
variables (marked on scan for Ring 2) and the usual width variables, as
well as odder variables such as area beneath the scan (marked for Ring
Sheppard, P.R. and L.J. Graumlich. 1996. A reflected-light video imaging
system for tree-ring analysis of conifers. Pp. 879-889 in Proceedings of
the 1994 International Conference on Tree Rings, Environment, and Humanity
(Tucson, AZ), J.S. Dean, D.M. Meko, and T.W. Swetnam, editors. Tucson:
Radiocarbon, Department of Geosciences, The University of Arizona.
Sheppard, P.R., L.J. Graumlich, and L.E. Conkey. 1996. Reflected-light
image analysis of conifer rings for reconstructing climate. The Holocene
Revised -- October 1, 1997; Copyright © ±1997, Paul
Lab. of Tree-Ring
Research Info Page