Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

An exotic grass kills trees by hijacking their water

02.08.2004


Foothill palo verde trees at the University of Arizona’s Desert Laboratory surrounded by buffelgrass. Photo credit: J. Alex Eilts.


Buffelgrass snatches water away from nearby palo verde trees, ultimately killing them.

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 parts of the laboratory grounds, there were almost no palo verde trees within the patches of buffelgrass.

Historic photographs taken by Ray Turner of the U.S. Geological Survey showed foothill palo verde trees on the laboratory grounds in locations which now have only buffelgrass. Such trees can live more than 100 years, so Eilts suspected that buffelgrass had something to do with the palo verdes’ disappearance.

To study how buffelgrass affects the trees, Eilts used an instrument called a pressure chamber to find out how much water stress the trees were experiencing. First he tested foothill palo verde trees surrounded by buffelgrass. The next year, he removed the grass from under some of those trees and repeated the experiments. Removing the buffelgrass significantly reduced the trees’ water stress.

The grass is reducing the water available to the trees, he said. "This means that in any given year the water deficit experienced by the trees with grass at their bases is greater compared with those trees free of the influence of buffelgrass."

Eilts also measured how much of their branches the trees shed.

Palo verdes self-prune little during an non-drought year, said Huxman. But when times are tough, buffelgrass makes it tougher. Eilts found that in a drought year, trees surrounded by buffelgrass lost about 24 percent of their total branches, whereas trees free of buffelgrass shed only about 16 percent. Huxman said, "Buffelgrass takes the drought and accentuates it."

The ecologists’ findings contradict current hypotheses about the relationship between trees, grasses and water in arid climates. Eilts said, "One would predict that the presence of buffelgrass would have the least affect on the deep-rooted woody plants such as the palo verde trees."

Instead, the buffelgrass reduces water available to the trees’ deep roots. "Effectively, what is happening to the trees in the grass is that they are experiencing a biotically induced drought," he said. "They seem to be responding to this the same way they do to normal drought, by self-pruning." Eilts said there is no reason why the grass couldn’t affect other plant species in a similar manner. He said, "What makes buffelgrass a potential threat to the foothill palo verdes and other native plants is that it can move into undisturbed habitats and effectively compete for water."

Mari N. Jensen | EurekAlert!
Further information:
http://www.arizona.edu

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF

nachricht Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>