|
 Contributed
by Jason Grogan, Research
Technician, Measurements Team, Forest
Resources Institute
Arthur
Temple College of Forestry, Stephen
F. Austin State University
Reprinted from The
Monitor, Winter 2002
 An
increment core is a small-diameter (0.17 to 0.5 inch) tree
cross section bored from the lower trunk (see photos). These
cores can tell many "stories"; to those willing to "listen."
Each year's growth is represented by the combination of a
light (early wood) and dark (late wood) ring. Tree growth
begins relatively rapidly in the spring, resulting in the
light colored early wood; dark colored late wood results as
growth decreases later in the year. The most common information
obtained from tree cores is tree age and rate of growth. Forest
managers often use these data for decision-making. Decreased
growth rates, evident by narrower growth rings, indicate reduced
vigor resulting from environmental factors such as overcrowding,
pest damage or drought. Informed decisions on when and how
to harvest timber or to conduct other forest improvement operations
may be made using tree rings as an indicator of management
needs.
 Other
information such as wood quality, past climatic conditions,
as well as past fire frequency also may be determined. Wood
quality is assessed by measuring the bulk density of the core.
Bulk density simply is the weight of a set volume of wood.
Higher bulk densities generally indicate increased strength
properties.
The most specialized use of tree cores is dendrochronology,
which is the dating of past events, such as drought and wildfire,
through the study of tree ring growth. Historic climatic conditions
may be indicated by the percentages of early to late wood.
Poor growing conditions are indicated by narrow growth rings
and a greater percentage of late wood . Frequency of wildfires
also may be determined by examining cores for fire scars.
For more information on dendrochronology visit
www.sonic.net/bristlecone/dendro.html.
Holes drilled to remove cores generally heal over rapidly
and do not harm or reduce the wood quality of healthy softwood
trees. High-quality hardwood trees, such as black walnut,
should not be cored. If you are interested in what cores from
your trees can tell you, contact your local consulting
forester, Texas
Forest Service Office, Texas
Cooperative Extension Service, or the Forest
Resources Institute
Find out more...
The Ultimate Tree Ring Pages! (Henri
D. Grissino-Mayer's Science of Dendrochronology Hough's
American Woods) ~ illustrations of 275 species of wood
Native
Pines of Eastern North America ~ An interactive tutorial
Dendro
Network WSL (Switzerland) ~ international research
in dendrochronology |
