The hypothesis that stressed loblolly pine (Pinus taeda L.) could
be distinguished from non-stressed loblolly pine by increased foliage
temperatures was tested. The foliage temperatures of seedlings and
trees were measured with an AGA Thermovision 680 system, imported by the
AGA Corporation, Secaucus, New Jersey. The AGA Thermovision 680 system
is a simple, easily transported remote sensing system for detecting
relative apparent temperatures of plant foliage without direct contact
with the leaves. This system is sensitive to infrared wavelengths in
the 2-5.6 micron region of the electro-magnetic spectrum.
Foliage temperatures in loblolly pine seedlings increased within one
week of stress induced by drought, flooding, or severing. Increased
temperatures of stressed seedlings were associated with reduced needle
moisture content prior to visual symptoms of stress.
Foliage temperatures of loblolly pine trees stressed by severing
the bole were warmer relative to neighboring control trees. Increased
temperatures were detected within one week after severing.
Previsual detection of stress can be achieved by measuring foliage
temperatures of loblolly pine. The AGA Thermovision should prove
to be a useful tool for non-destructive sampling of plant stress, for
locating stressed trees, and potential bark beetle infestations.
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