May
2, 2007 Tropical forest,
often called
rainforest, conjures up images of verdant, evergreen landscapes.
Whereas
temperatures may be relatively constant in the tropics, rainfall and
water
availability often vary dramatically across small distances. "The Isthmus of
Panama is
the ideal place to test the idea that the distribution of plant species
is
influenced by their ability to tolerate a lack of water," said
researcher
and article author Bettina Engelbrecht of the After measuring the
drought
tolerance of 48 plant species experimentally, scientists looked at the
plants’
regional distributions across 122 tropical forest plots set up by the
Center
for Tropical Forest Science. The plots are distributed over a rainfall
gradient
from the wet "It was a surprise
that even
in humid tropical forests, traditionally viewed as water saturated,
plants
growing at dry sites were more drought-tolerant than plants growing at
wet
sites," Engelbrecht said. The team also
evaluated the local
distributions of both seedlings and older trees on STRI’s
50-hectare Forest
Dynamics plot on Researchers ruled
out several
other potential predictors of plant distribution that could be
associated with
drought tolerance, such as shade tolerance and nutrient availability. Identifying drought
tolerance as
a cause of plant distribution patterns significantly advances the
understanding
of tropical plant diversity and implies that changes in rainfall
patterns—a
predicted consequence of climate change in the tropics—may
give rise to
dramatic changes in tropical plant communities. "In the tropics,
climate
change does not just mean temperature change—dramatic shifts
in rainfall
patterns also are expected to occur," said Ben Turner, STRI staff
scientist and co-author. "Our research shows that changes in rainfall
patterns will have considerable consequences for tropical forests."
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