Forest study news: New laser technique
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Web page: HTTP://www.eurekalert.org:80/E-lert/current/public_releases/deposit/forestlaser.html
New Laser Technique Will Help Scientists Learn More About Forest
Changes
CHARLOTTESVILLE, Va., Nov. 16 -- A new technique for gaining a three-dimensiona
picture of forest canopies may help answer both practical needs of forest
managers and basic questions about the relationship between forests and global
climate change.
The system, developed by University of Virginia environmental sciences graduate
student Michael Lefsky and scientists from NASA and the Smithsonian
Environmental Research Center, employs laser radars (lidar) suspended from
low-flying airplanes to rapidly and accurately assess the trees' shapes. It is
called Scanning Lidar Imager of Canopies by Echo Recovery (SLICER).
"Large scale surveys using SLICER could, for the first time, accurately predict
the current storage of carbon in forest stands and their capacity to act a
source and sink for carbon dioxide," says Lefsky, whose research concerns the
physiological ecology of plants with emphasis on landscape-scale processes.
SLICER works like this: A plane flies over a forest at a height of five
kilometers, sending out laser pulses; the beams bounce off layers of foliage and
the ground and then return to the plane's bottom-mounted telescopes. The
reflected light returns to the telescopes at slightly differing times, depending
on the distance it transversed. Lefsky developed the mathematical algorithm
that turns this raw laser data into an estimate of the canopy's shape.
According to its developers, SLICER is as accurate as the standard field method
of gathering similar data, which takes many hours to perform. In contrast,
SLICER can take up to 100 measurements per second to yield a three-dimensional
picture of the canopy, and could be used even in dense and remote forests.
Moveover, SLICER can predict other forest characteristics, such as the total
number and size of the trees.
Information about forest structure is valuable both to forest managers, who may
wish to know when the trees reach a marketable size, and to global-change
scientists, who study the flow of carbon through the global ecosystem. Carbon,
predominantly in the form of gaseous carbon monoxide and carbon dioxide, is one
of the elements that contributes to world-wide atmospheric warming. The two
principal causes of increased atmospheric carbon dioxide are fossil fuel
burning and changes in land use (typically, replacing trees with cropland).
Trees bind carbon dioxide in their tissues as they grow. Thus, the numerous
rapidly growing trees in a young forest store more carbon that the few, mature
trees in an older forest. At present, there is little quantitative
understanding of precisely how much young and old forests differ in their
capacities to store carbon. SLICER could help answer this question.
Lefsky's partners in this research are Geoffrey Parker, of the Smithsonian
Environmental Research Center, and David Harding and J. Brian Blair, of NASA
Goddard Space Flight Center. Results of initial experiments carried out at
sites in North Carolina and Maryland were presented at a meeting of the
Ecological Society of America in August.
November 15, 1996
REPORTERS AND EDITORS:
For more information, contact Michael Lefsky at (804) 982-2333 or
mal3p@virginia.edu
David Harding may be reached at (301) 286-4894 or harding@denali.gsfc.nasa.gov
Geoffrey Parker may be reached at (301) 261-4190 x210 or parker@serc.si.edu
Television reporters should call our TV News Office at (804) 924-7550.
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