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 Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)

nachricht Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>