About FACE:

This photograph shows two of the elevated CO2 study plots at the FACE Facility. Photo by Travis Huxman.

Around the globe, atmospheric carbon dioxide (CO2) levels have skyrocketed. The evidence points to rapid industrialization as the culprit, causing a 25 percent increase in CO2 since the late 1950s. Various scientific entities are studying what the effects of much larger amounts of CO2 in our atmosphere may mean, now and in the future. The Desert Research Institute (DRI) along with the University of Nevada, Las Vegas (UNLV) and University of Nevada, Reno (UNR) is one of only seven groups in the United States studying the effects of elevated CO2 with state-of-the-art technology.

Ninety miles northwest of Las Vegas, an experiment of global proportions began in April 1997. Researchers at the Nevada Desert FACE (Free-Air-Carbon dioxide-Enrichment) Facility, located at the Nevada Test Site (NTS), are conducting a 20-year study of the effects of elevated CO2 on the Mojave Desert's ecosystem. This is the only research being done in a natural desert environment. The project is steered by four principal investigators: UNR's Dr. Jeff Seemann leads the project's molecular and cellular component; Dr. Stan Smith, UNLV, drives the above-ground ecosystem studies; Dr. Bob Nowak, UNR, focuses on the underground examination of roots; and Dr. Jim Coleman, DRI's vice president for research and business development, is leading the study of carbon and nitrogen cycles.

Dr. Jim Coleman, DRI's Vice President for Research and Business Development (front), UNLV professor of biology Dr. Stan Smith, and DRI remote sensing scientist Lynn Fenstermaker at the Nevada Desert FACE Facility at the Nevada Test Site. Photo by Lori Cain, courtesy of Las Vegas Sun.

DRI, UNR, and UNLV are collaborating with the U.S. Department of Energy (DOE) and Brookhaven National Laboratory, to answer questions about the effects of the Earth's rapidly rising CO2 level on plant and animal life, and water balance, in an untouched desert landscape.

"The Nevada Test Site is a perfect environment for examining how the desert ecosystem responds to elevated CO2," reports project director Lynn Fenstermaker (DRI), "because it has large tracts of pristine desert that are off limits to the public, and the roads and power necessary for our studies are already in place." Fenstermaker says strict security at the NTS provides researchers the freedom to run expensive, highly sensitive equipment round-the-clock without risk of vandalism or theft.

While the study's overall design is fairly simple, it uses sophisticated technology developed by DOE's Brookhaven National Laboratory in nine, 23-meter-diameter test areas known as plots.

Set 100 meters apart, the plots are connected by access paths containing underground power, CO2 and fiber-optic lines. All of the plots have elevated walkways and mechanical platforms, which allow scientists access to any location within each plot without disturbing the desert's microbiotic crust. Three plots are continually treated with air containing 550 ppm (parts per million) CO2, which is blown across the plot. This concentration of CO2 is the anticipated atmospheric concentration by the year 2070. Another three plots have ambient air (CO2 concentration is approximately 360 ppm) blown across each plot. These plots are called blower controls. The final three plots are non-blower controls, which means that they are not exposed to forced air. The purpose of the two sets of control plots is to determine if the blower fans have any effect on plant and animal life. So far, the researchers have not been able to measure any effects of the blowers, so the differences they are seeing are due solely to the elevated CO2.

Each test plot that uses air blowers with CO2 is surrounded by standing vent pipes with several holes facing the inside of the plot. The vent pipes are attached to control valves that are all connected to a large pipe called a plenum. The plenum connects to a fan and instrument shelter. For most of the year, 24 hours a day, the treatment plots receive pure, food-grade CO2 mixed by the fan with ambient air. The fan forces the mixture into the plenum. As the plenum circulates the mixture, computer-regulated control valves provide continual, upwind distribution across each plot. Constantly monitoring and adjusting the mix, the computer maintains a CO2 concentration at 550 ppm. In addition to ambient and elevated CO2 levels, minute-by-minute computer monitoring of all nine plots includes wind speed and direction, air temperature, and incoming solar radiation.

"We fumigate the elevated CO2 rings 24 hours, seven days a week," says Fenstermaker. "The only time we stop is in high winds-because the carbon dioxide dissipates too quickly-and when the temperature drops below freezing, when the plants are not functioning." Fenstermaker adds that the CO2 comes from a nearby 50-ton, 40-foot-high tank that is filled weekly in winter and every other day during the summer months.

In addition to the CO2 distribution system, the study plots include a variety of devices to collect data about how CO2 affects plants, soils, and insect life. Mini-rhizotron tubes-sub-surface plexiglass tubes-allow a special video camera to monitor root growth and structure. During the growing season, leaf litter trays collect airborne plant debris for sorting and analysis. A soil respiration chamber provides information about how CO2 alters soil carbon and water exchange.

"Another important focus of our study is nitrogen cycling," notes Fenstermaker. Since nitrogen in soil is a limiting factor for desert plants, the study seeks information about how elevated atmospheric CO2 affects the availability of nitrogen for plant growth. "We're also looking at the number and variety of plants within the plots, and physiological data such as the rate of photosynthesis and water loss (evapotranspiration)."

"We're examining whether plants will increase in size and number in the elevated atmospheric CO2 plots," she says. "We've already seen increased biomass and plant numbers in the enhanced CO2 plots during the El Ni_o of 1998, because the increased CO2 allows plants to reduce the size of their pores, or stomata. Smaller stomata mean less water loss, so plants can photosynthesize-produce "food" for growth-longer throughout each day."

Fenstermaker with the FACE facility computer that monitors and controls the distribution of CO2 into the elevated CO2 plots. Photo by Lori Cain, courtesy of Las Vegas Sun.

As Fenstermaker explains, the results from the elevated CO2 plots for the 1998 growing season indicate increased overall plant production, biomass, and a much higher number of seeds from annual plants. These results support the idea that desert landscapes may respond better than other climates to elevated atmospheric CO2.

"Desert plants grow slowly," Fenstermaker says. "So the study's 20-year time frame should give us the data we need to evaluate the effects of CO2." She notes that El Ni_o conditions, occurring approximately every seven years, are important because the increased rainfall to desert ecosystems provides an opportunity for more plant growth. While studying the effects of elevated CO2 during wet years is vital, equally important is determining how higher CO2 affects flora and fauna during average or lower rainfall years.

The Mojave Desert-the driest area in North America-provides FACE researchers with an ideal location for monitoring how future levels of atmospheric CO2 will change desert ecosystems. While long-term results will take time, early results indicate that deserts will produce more than two times as much plant material during wet years with elevated CO2. Of particular importance is the fact that a non-native invasive grass (red brome, a relative of cheatgrass) responds to CO2 such that it is far more productive than native plants during wet years. Bromus invasions (e.g., cheatgrass invasions in the Great Basin region) are known to increase the frequency of fires from a 75- to 100-year cycle to a four- to seven-year cycle. These fires are far more intense than those in native vegetation, and usually result in a loss of native shrubs. A change from shrubs to grasses would have a dramatic effect on desert water cycles and wildlife habitat, as well as socioeconomic factors.

Research will continue at the Nevada Desert FACE Facility to determine if these early results are true indicators of long-term change in the Mojave Desert, and what other surprises may be in store for desert ecosystems with a future of elevated CO2 levels.

Lynn Taylor

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