Scientists thought deep-rooted plants such as desert trees did not compete with grasses for water.

Now researchers from the University of Arizona in Tucson report that buffelgrass, an invasive non-native species, grabs water before foothill palo verde trees can.

The situation does not bode well for the trees, said J. Alex Eilts, a doctoral candidate in UA's department of ecology and evolutionary biology. Native to the Sonoran desert, foothill palo verde trees, or Cercidium microphyllum, cope with drought by shedding branches to reduce the amount of water needed to survive.

"It's as if the trees are self-pruning themselves to death," he said.

Eilts will give his presentation, "Effects of a non-native grass on a dominant woody Sonoran desert tree," at 9:50 a.m. on Thursday, Aug. 5 in the Oregon Convention Center in Portland, Ore., at the annual meeting of the Ecological Society of America. His coauthor, Travis Huxman, is an assistant professor in UA's department of ecology and evolutionary biology.

Buffelgrass, or Pennisetum ciliare, thrives in arid and semi-arid climates. Ecologists are increasingly concerned about buffelgrass, a native of Africa often introduced for livestock grazing or to control erosion, because it spreads quickly and outcompetes native species. Buffelgrass now is found in Texas, New Mexico, Arizona, Mexico, Venezuela, Argentina, Hawaii and Australia.

First planted in the Tucson area shortly before 1940, the exotic grass now is found in the Tucson Mountains, on A Mountain and on nearby Tumamoc Hill, home of UA's century-old Desert Laboratory. Researchers believe that buffelgrass first invaded the laboratory grounds in the mid-1980s.

One focus of the laboratory is long-term research on the ecology of Sonoran desert plants. While working on a class project, Eilts noticed that, unlike other par
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Contact: Mari N. Jensen, UA News Services
mnjensen@email.arizona.edu
520-626-9635
University of Arizona
1-Aug-2004