June 7, 2004
Plants adapt to drought by becoming more water
efficient, Nature study shows
Changes occur from desert to tropical forest
By Jennifer McNulty
Plants in wet tropical forests adapt to changes in precipitation and
become as efficient in their water use during droughts as plants in
arid deserts, according to a study to be published in the June 10 issue
It isn't just plants in arid areas that become more water-efficient
during droughts, researchers found. Water is plentiful for these
plants in Plitvice Lakes National Park, Croatia. Photo
by Kolby Kirk
While scientists have known for a long time that desert plants are
efficient with water use, they were surprised to find that plants in
grasslands and forest ecosystems demonstrate the same ability to acclimate.
The study also suggests that there is a point beyond which plants may
not be able to acclimate to precipitation changes.
Understanding the ability of plants to adapt to precipitation
changes has important implications for agriculture, forestry, and grazing,
said study coauthor Michael Loik, an assistant professor of environmental
studies at UCSC. If global climate change causes precipitation
levels to drop below historic levels, some plants will be unable to
grow, which could result in dramatic changes in the species composition
Precipitation patterns are expected to change as part of other global
climate changes, but researchers predict effects that vary from an 80
percent reduction in precipitation to an increase of more than 100 percent.
The next step in understanding the ecosystem effects of precipitation
is for researchers to conduct a broad study in which they manipulate
precipitation levels--both increasing and decreasing amounts--in multiple
locations, said Loik.
Loik founded PrecipNet, an international consortium of researchers
focusing on the precipitation and ecosystem aspects of climate change,
and was a catalyst behind the Nature study. The lead authors
of the Nature study are Travis E. Huxman of the University of
Arizona, Tucson, and Melinda D. Smith of UC Santa Barbara and Yale University;
the complete list of authors can be found below.
Loik secured funding to bring together the team of researchers who
conceived of the study and conducted the research.
During a series of workshops held at the National Center for Ecological
Analysis and Synthesis at UC Santa Barbara, the researchers analyzed
precipitation and growth data collected at 14 long-term research sites
in nine regions throughout North and South America. The sites represent
a range of ecosystems, from the arid Mojave Desert to Panamas
wet tropical forest and the vast, cold, treeless landscape of Patagonia
in Argentina. Each site had at least six years of growth and precipitation
In addition to finding that all ecosystems were equally productive
in drought conditions, researchers found that low-precipitation regions
were much more sensitive to changes in precipitation than theyd
expected. It appears that there may be a certain threshhold of
precipitation change that plants may be able to tolerate, at least in
the decreasing direction, said Loik.
Researchers at 40 sites around the globe are engaged in long-term monitoring
of precipitation and plant interactions, said Loik. Understanding the
interaction of climate and precipitation changes on ecosystems will
help land-use managers and water-resource specialists make informed
policy decisions about irrigation for agriculture and the productivity
of forests and grazing land, added Loik. It comes down to our
ability to produce food, fiber, and fuel, he said.
In addition to Loik, Huxman, and Smith, coauthors of the Nature
Philip A. Fay of the Natural Resources Research Institute, Duluth, Minn.;
Alan K. Knapp of Colorado State University in Fort Collins; M. Rebecca
Shaw of the Carnegie Institution of Washington in Stanford, Calif.;
Stanley D. Smith of the University of Nevada, Las Vegas; David T. Tissue
and John C. Zak of Texas Tech University in Lubbock; Jake F. Weltzin
of the University of Tennessee in Knoxville; William T. Pockman of the
University of New Mexico in Albuquerque; Osvaldo E. Sala of the University
of Buenos Aires in Argentina; Brent M. Haddad of UCSC; John Harte of
UC Berkeley; George W. Koch of Northern Arizona University in Flagstaff;
Susan Schwinning of Biosphere 2 Center, Columbia University, Oracle,
Ariz.; Eric E. Small of the University of Colorado at Boulder; and David
G. Williams of the University of Wyoming in Laramie.
The research was funded by the National Science Foundation, the U.S.
Department of Agriculture, the U.S. Department of Energy, and the National
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