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Aspen/FACE - CO2 & Ozone Interaction

The Aspen FACE (Free-Air Carbon Dioxide Enrichment) Experiment is a multidisciplinary study to assess the effects of increasing tropospheric ozone and carbon dioxide levels on aspen forest ecosystems.

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FACE Investigators

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George Host and Judd Isebrands are the major contributing modellers to the Aspen/FACE project and details of the Ecophys model can be found at its home page.

George Host and Judd Isebrands are the major contributing modellers to the Aspen/FACE project and details of the Ecophys model can be found at its home page.

Global Change (IGBP)

The International Geosphere-Biosphere Programme (IGBP) is an interdisciplinary scientific activity established and sponsored by the International Council of Scientific Unions (ICSU). The Programme was instituted by ICSU in 1986, and the IGBP Secretariat was established at the Royal Swedish Academy of Sciences in 1987.

Free-Air Carbon Dioxide Enrichment (FACE) Experiment

Wheat crop on 11 May 1993 showing phenological differentiation. The different water treatments are separated by a small partly hidden walkway (leadiong from the middle of the left edge to the right upper corner of the figure). The DRY half plot (with 50% of the full water supply) is located in the left upper portion of the figure. The half plot visible in the foreground got fully water supply to meet evapotranspiration [WET]. The accelerating effects on phenology and senescence due to the drought (between the top and the bottom) and the CO2 enrichment (AMBIENT outside the ring, enriched CO2 [FACE] inside the ring) including their combined effects are clearly visible.


Trees Increase Their Rate of Photosynthesis Upton, NY - Scientists at the U.S. Department of Energy's Brookhaven National Laboratory and at Duke University report that loblolly pine trees grown in a 21st century atmosphere of increased carbon dioxide (CO2) show a marked increase in their rate of photosynthesis.

In a season-long experiment, the researchers found that the rate of photosynthesis in pines growing in elevated CO2 was 65 percent higher than in pines growing in the present CO2 environment. They also found that the trees' water consumption did not change in response to the elevated CO2, unlike the decrease typically seen in crops and herbaceous plants.

David Ellsworth, tree physiologist with Brookhaven Lab, said, "Ours is the only study of this sort that has ever been conducted in a forest, yet one-third of Earth's land mass is covered by forests. Up to now, we have not been able to study how an entire forest would respond to increased CO2."

Principal researchers in the study also include tree physiologist Ram Oren, of Duke University, and ecologist George Hendrey, also of Brookhaven. Their work is reported in a paper soon to be published in the journal Oecologia. Ellsworth is scheduled to present the findings on August 1, at the annual meeting of the Ecological Society of America in Snowbird, Utah.

About FACE The forest experiment was the first use of FACE technology in a forest environment. FACE, which stands for free-air carbon-dioxide enrichment, was developed by Dr. Hendrey and colleagues at Brookhaven to study effects of enhanced CO2 on plants in their natural environment. Only such experiments, conducted in open air rather than in greenhouses or any other types of enclosures, can mimic "real world" conditions in order to simulate how entire ecosystems will cope with the predicted higher-CO2 atmosphere of the next century.

Levels of CO2 in the atmosphere have risen from 280 parts per million (ppm) at the beginning of the Industrial Revolution in the late 18th century to 355 ppm today, an increase of over 25 percent, primarily because of increased fossil-fuel combustion. Scientists expect that the current level will double some time in the next century.

Dr. Hendrey and colleagues have previously used FACE to evaluate effects of increased CO2 on agricultural crops in Mississippi and Arizona, and on grassland in Switzerland.

In the FACE system, an array of vertical pipes encircling the test area releases CO2 in a computer-controlled mixture with ambient air. The computer measures wind direction, wind speed and the CO2 concentration in the center of the array, and uses this information to adjust the rate of gas to be released on a second-to-second basis. The resulting environment is as close as practical to the atmosphere expected to prevail in the middle of the 21st century.

In the Duke Forest The forest experiment was carried out on mature loblolly pine trees in North Carolina, in a forest owned by Duke. Used for timber, loblolly pines are the mainstay of the lumber industry in the Southeast. While increased photosynthesis may result in faster-growing trees and, hence, more wood, the researchers caution against viewing their results as entirely good news. It is not yet clear that the extra photosynthesis will be reflected in faster growth. Said Dr. Ellsworth, "These are early findings, and there are many questions still unanswered. What about competition from other trees? Will the forest outstrip the soil's capacity to support enhanced growth? Would faster-growing wood be more brittle? It's not so simple."

The Experiment Ahead Already begun is a much broader, multi-year experiment. Besides continuing the tree physiology work, this next experiment will include soil and atmospheric studies. Dozens of ecologists and plant biologists will work at the Duke forest site, collecting data not only on loblolly pines, but also on sweetgums, dogwoods, honeysuckle, junipers, and microbes and soils. Results from the study will be used in global computer models to predict the role of vegetation in future CO2 exchange with the atmosphere.

The FACE approach gives many scientists access to a large facility that encompasses hundreds of individual plants in an intact ecosystem. This reduces the cost per scientist dramatically. The net effect is an economical way to build an understanding of how a particular ecosystem will respond to rising levels of CO2.

FACE research is supported by the Department of Energy's Office of Health and Environmental Research, Ecological Research Division. Brookhaven National Laboratory carries out basic and applied research in the physical, biomedical and environmental sciences and in selected energy technologies. Brookhaven is operated by Associated Universities, Inc., a nonprofit research management organization, under contract to the Department of Energy.

Free-Air Co2 Enrichment Project (FACE)

"The Free-Air CO2 Enrichment (FACE) Project: Determination of the effects of elevated CO2 and interacting environmental variables on agronomic crops.

Numerous CO2-enrichment studies in greenhouses and growth chambers have suggested that growth of most plants should increase about 30% on the average with a projected doubling of the atmospheric CO2 concentration. However, the applicability of such work to the growth of plants outdoors under less ideal conditions has been seriously questioned. The only approach that can produce an environment as representative of future fields as possible today is the free-air CO2-enrichment (FACE) approach"

Free-Air Carbon Dioxide Enrichment (FACE) Experiment

The concentration of CO2 in the earth's atmosphere has increased continuously since the beginning of the industrial period, and will probably have doubled by the end of the 21st Century (Keeling and Whorf 1991, Schimel et al. 1995). Within the framework of a FACE experiment conducted by the U.S. Water Conservation Laboratory (USWCL), Phoenix, Arizona, in the Sonoran Desert, concentrations of CO2 as they may be expected within the coming 50 to 75 years were established and maintained for the first time under open-air conditions, and their impact on agricultural cultivated plants (cotton, wheat and barley) was investigated. For this purpose, the concentration of CO2 within the air is raised for the FACE plots in the experimental field to 550 ppm (FACE) as against 370 ppm (Control), under otherwise undisturbed atmospheric conditions (Lewin et al. 1993). Results achieved in previous experiments under laboratory conditions or in chambers concerning the effects of raised concentrations of CO2 are not representative of actual open-air conditions due to technically-conditioned disturbances of the atmospheric energy, water and CO2 exchange and the microclimatic and biological changes resulting therefrom. In the FACE experiment, the distinct effects for ambient and enriched atmospheric CO2 and for two steps of water supply (sufficient [WET], 50% [DRY]) were investigated in the runs for 1992-94. In the runs for 1995-97 similar studies will be realised with varying supplies of nitrogen.

Brookhaven National Laboratory U.S. Department of Energy

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Last modified: August 26, 1998