| Ed--
Here are a couple pictures and some materials that ENTS members
may be interested in... These pictures were taken on January 21,
2005 at the Cross Timbers Research Natural Area of the LBJ
National Grassland just north of Decatur, Texas. Most of the RNA
is encompass by a small valley with an intermittent stream
carving a narrow gorge through the weakly cemented sandstone and
conglomerates common to the area. The site is relatively
atypical for older Cross Timbers sites, as the deep sands that
cover the uplands are level and rarely rocky. The area
receives approximately 28 inches of precipitation per year, and
high evapotranspiration makes the site droughthier than it may
otherwise seem.
Vegetation
is dominated in the higher, drier portions of the RNA by mature
post oaks with a scattering of blackjack oak and several other
hardwood species. Eastern redcedar is becoming invasive
over much of the area, and is starting to dominate in the lower,
moister slopes currently occupied by a mixture of elm, Nuttall
oak, and post oak. Most of the area has been cutover and
grazed, and the Forest Service is attempting to reintroduce fire
to the stands. A scattering of old, gnarly post oaks 150
to 300 years old can still be found.
The first
picture is of Dan Griffin, a student working for Dr. David
Stahle of the University of Arkansas, coring one of the old post
oaks (probably a 300+ year old tree).
The second image is
of a younger post oak (probably ~ 150 years old) more commonly
found in the RNA. These old post oaks, while relatively short
(less than 60 feet tall) and not very large in diameter (1 to 2
feet DBH) are often impressively old, with some individuals
exceeding 300 years old.
Dr. Stahle has found other post
oaks in other Cross Timbers stands that exceed 400 years, and
eastern redcedars on some protected bluff sites have exceeded
600 years old.
Don
**************************************************************
Don C. Bragg, Ph.D. Research Forester
USDA Forest Service,
Southern Research Station
P.O. Box 3516 UAM
Monticello, AR 71656
http://www.srs.fs.fed.us/4106/
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