Under drought conditions, tropical forests can be as efficient at using water as desert ecosystems, researchers report
When push comes to shove, all ecosystems have the same maximum rain-use efficiency, a measure of total plant growth per unit of precipitation.
The finding indicates theres an upper limit to ecosystems productivity, said Travis E. Huxman, a plant physiological ecologist at the University of Arizona in Tucson. He and a team of researchers calculated the upper limit, which they call RUEmax (maximum rain-use efficiency).
Life depends on the productivity of plants, Huxman pointed out, adding, "RUEmax defines the limits of that production."
However, the research indicates that under drought conditions, high-productivity systems like grasslands and forests grow even less than expected. Most of the climate-change scenarios for the next century predict an increase in extreme events, including more droughts.
Huxman said, "We originally expected drought to impact grasslands to some degree, but this finding says that if we get extreme variability, there will be even less plant growth than we originally thought."
Huxman, first author of the research report, led the research team along with Melinda D. Smith of Yale University. The teams article, "Convergence across biomes to a common rain-use efficiency," will be published in the June 10 issue of the journal Nature. A complete list of authors and their affiliations is at the end of this article.
The work sheds light on what Huxman called "one of the oldest ecological questions on the face of the planet: how does water affect how an ecosystem works?"
Although it seems a simple question, it turns out to be a toughie, he said. "My wife can answer it for her garden, but you cant take the information that my wife knows for her garden and apply it to many different biomes around the world."
In the early 1970s, ecologists tried to answer the question by fanning out over the globe and by taking lots and lots of ecological measurements in a variety of ecosystems during a single year. The project, called the International Biological Program (IBP), couldnt answer that fundamental question: ecologists realized that they needed data collected in many different ecosystems over many years.
But one outcome of IBP was the establishment of many long-term study sites, including the network of Long-Term Ecological Research sites maintained by the National Science Foundation.The study sites represent a range of the worlds biomes, from the Mojave desert in Nevada to the wet tropical forest of Panamas Barro Colorado Island to cold grass-shrub steppe of Patagonia in Argentina. Year after year, researchers at those sites collect data on the annual precipitation and annual total plant growth.
Fourteen of the sites had at least six years of such growth and precipitation data. So Huxman and his colleagues finally had the information needed to answer the question of how water affects various ecosystems.
Team member Michael Loik of the University of California, Santa Cruz, spearheaded the effort to win the funding for a series of workshops held at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.
At the workshops, the scientists studied and analyzed the data.
What they found surprised them.
One hypothesis was that ecosystems that have great variabilty in precipitation, such as grasslands, would be the most responsive to rainfall. More predictable regions, such as deserts or wet tropical forests, would not respond much to variations in precipitation.
Not so. The low-precipitation regions such as deserts were much more sensitive to changes in precipitation than the group expected.
Moreover, the team found that in drought conditions, all ecosystems were equally productive.
"Thats kind of shocking," Huxman said. "In a drought year, Harvard Forest is as efficient at using water as the most arid desert is all the time."
The finding has implications for how various ecosystems will behave under future climate change, he said.
Huxman said, "For any ecosystem, if rain falls below historical minimums, our model predicts pretty substantial reductions in productivity."
Plants wont buffer the effect of climate change on ecosystems, but rather exacerbate it, making the world a more uncertain place, he said.
"Theres enhanced variability in ecosystem processes with increased variability in precipitation," Huxman said.
He said the finding suggests that ecologists should be doing experiments to see how various types of ecosystems respond to different levels of precipitation. Huxman is doing so by simulating different-sized rain events on sites in southern Arizona and seeing how grassland and mesquite savanna ecosystems respond.
Huxmans coauthors on the June 10 Nature paper are Melinda D. Smith of Yale University; 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.; Michael E. Loik of the University of California, Santa Cruz; 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 the University of California, Santa Cruz; John Harte of the University of California, 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 Park Service.
Scientists team up on study to save endangered African penguins
16.11.2017 | Florida Atlantic University
Climate change: Urban trees are growing faster worldwide
13.11.2017 | Technische Universität München
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses