by Fariss Samarrai
27, 2003 -- What most people call a tree, Dan Druckenbrod calls
stands in the forest below Monticello, the home of Thomas Jefferson,
looking for old trees.
because a tree is big, it doesnt mean its as old as
a smaller tree nearby," he said. "White oaks grow slow,
so they can be much older than the faster-growing red oaks."
spots a white oak that looks like it has seen some years, with missing
and gnarled branches near its canopy. He begins coring the tree,
seeking its center with a hand-cranked boring device. Soon, he will
know how old the tree is and where its place is in the land-use
history of a famous Americans property.
trees have different climate responses," Druckenbrod said.
"They have different life spans and growth rates. They are
affected by the amount of light and moisture they get. Reconstructing
their life history is somewhat of an art, but its rationale-based."
a University of Virginia doctoral student in environmental
sciences who will be graduating in May, has been comparing the
weather records kept by James Madison and Thomas Jefferson with
the climate history stored in the trees surrounding the old plantations
at Montpelier and Monticello. Hes curious about the history
of the forest, how old the trees are, what the climate has been
like during the lives of the trees and how the land has been used
whether the forest has been logged and replanted, or if it
came back naturally.
is 300 years of land use at Madisons Montpelier," he
said. "Im interested in how the use of the land there
has impacted the environment. Im looking for lessons in land
use from the past."
28, recently published his first scientific paper in the
Bulletin of the American Meteorological Society detailing
his reconstructions of precipitation patterns at Montpelier in the
late 18th century. The first chapter of his doctoral dissertation
on forest responses to climate, the paper is eloquently written,
a fascinating combination of human and natural history.
more than a year Druckenbrod and colleagues cored dead trees in
the old growth forest around Montpelier and analyzed the long, thin
plugs for climate history in the time of Madison.
kept extensive weather diaries for seven years while living on the
property, and Druckenbrod has compared the natural archive from
the trees with Madisons carefully logged observations.
agree well," he said.
Madison saw heavy rainfall, Druckenbrod found accelerated tree growth,
a "signal" of moisture. Where Madison recorded drought,
Druckenbrod found indications of slow growth, a sign of low moisture.
What he found that surprised him, though, was that over a trees
long life, 200 or more years in some cases, the moisture signal
shifted from May in Madisons time, to June in succeeding decades.
may be a physiological response to climate by the tree as it ages.
It may be because of a shift in land use patterns, such as land
clearing which may have impacted the seasonal precipitation in the
area. Or it may be that the summer peak of rainfall has actually
shifted one month later," Druckenbrod said.
also found that a drought Madison recorded in 1792 shows up in the
tree rings from the Montpelier forest and corresponds with an El
Nino event now known to have occurred at the time. El Nino, a periodic
warming of surface water in the tropical-Pacific Ocean, often causes
a lowering of precipitation in the eastern United States.
has now turned his attention to the forest below Jeffersons
at Monticello are interested in reconstructing the forest history
there, and they hope to determine the age of timbers from a log
cabin that existed during Jeffersons lifetime.
information can provide a clearer picture of how the plantation
operated and how the land was used. Druckenbrod is again comparing
the history he finds in the trees and timbers with the detailed
weather diaries kept by Jefferson.
also is, as a matter of curiosity, trying to determine the age of
his parents farm home in rural Pennsylvania, the house where
he grew up. A large timber from the house rests on a table in his
lab along with cores and the cross-sections of trees from Montpelier
spent a lot of time in the woods growing up," he said. "I
grew up in a house that dates back to the 1780s, and my parents
always collected antiques. Im interested in both natural and
co-authors include U.Va. environmental sciences professors Michael
Mann and Hank Shugart, and University of Arkansas researchers David
Stahle, Malcolm Cleaveland and Matthew Therrell. The paper can be