UNIVERSITY
GRADUATE SCHOOL BULLETIN
ANNOUNCEMENT
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Florida International
University |
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University Graduate School |
Doctoral Dissertation
Defense
Abstract
The Effects of Climate on
the Growth and Physiology of Tropical Rainforest Canopy Trees
by
Joseph John
O’Brien
Tropical
rainforests account for more than a third of global net primary production and
contain more than half of the global forest carbon. Understanding the link
between current climate and rainforest tree growth, a major component of forest
productivity, will be crucial to efforts at modeling future climate and
rainforest response to climate change. Studies of yearly tree growth find
similar variation across several species suggesting a climatic cause, but
attempts at linking the annual variation of rainforest tree growth and weather
have been unsuccessful. Possible causes of this failure include important
sub-annual variation in tree responses or other previously unmeasured
variables.
This
work reports the physiological and growth responses to micrometeorological and
phenological states of ten species of canopy trees in a Costa Rican wet
tropical forest at sub-annual time intervals. I measured tree growth using band
dendrometers and estimated leaf and reproductive phenological states monthly.
Electronic data loggers recorded xylem sap flow (an indicator of photosynthetic
rate) and weather at half-hour intervals.
My analysis of xylem sap flow showed that
physiological responses were independent of species, which allowed me to construct
a general model of weather driven sap flow rates. Leaf phenology was linked to
growth in four of the ten species, with two of these species showing a link
between leaf phenology and weather. Combining the results of the sap flow
model, growth and the climate measures showed variable correlations between
weather and growth among the species. Rainfall and nighttime temperatures were
the best predictors of growth.
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Date: November 7, 2001 |
Department: Biological Sciences |
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Time: 9:30 A.M. |
Major Professor: Steven F. Oberbauer, Ph.D |
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Location: ECS 138 |
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