For the next four years, DRI ecologist Jay Arnone will watch the grass grow. And not just any grass. Dr. Arnone will be watching genuine Oklahoma prairie grass grow in Reno in genuine red prairie soil under carefully duplicated prairie climate conditions. The goal is to develop a model for understanding how abnormal increases in temperature will influence the natural movement of carbon dioxide in and out of ecosystems, using the prairie grassland as a test bed.
In the third week of November, a dozen flatbed freight trucks, each transporting a "monolith" of pure prairie dirt weighing between 16 and 18 tons will arrive at the Desert Research Institute's Frits Went Laboratory in Reno. Each block of Oklahoma soil, in 4'10" x 8'10" x 5'7" pots, will be carefully lifted by a 120-ton capacity crane and deposited into four specially designed experimental chambers called EcoCELLs in the laboratory, an advanced research greenhouse. Three monoliths will go into each EcoCELL.
The EcoCELL chambers are extensively instrumented during research operations, with all the data collected in real time in computer databases. The pots also sit on extremely sensitive scales that reveal changes in weight due to water vapor loss or gains from simulated rainfall.
Temperatures in the chambers will duplicate the average daily and seasonal variations of the monoliths' Oklahoma origins. In the second year of the study, the temperature in two EcoCELLs will be increased above the average by 4 degrees centigrade for one year. The other chambers will remain at average Oklahoma temperatures. The final two years will be a comparative analysis of how this one-year increase temperature affected the movement of carbon in the atmosphere, soil and plant material to provide important clues for improving computer models used to predict future responses of terrestrial ecosystems to global change.
"Because grasslands comprise such a large area of the Earth's surface and because of their responsiveness to change and the biological diversity they exhibit, they are a good place to start with this kind of experiment," Arnone said. "Another advantage is that these ecosystems have already been extensively studied, so we have good basic understanding of their processes."
Arnone is the lead scientist in the $3 million study funded by the National Science Foundation, which also includes the University of Oklahoma and the Max Planck Institute in Germany. Many scientists from other organizations have also indicated their interest in observing the project.
Arnone says there are several hypotheses about how ecosystems will respond to an unusually warm year.
"Some statistical analyses of global CO2 and temperature data have shown that the rate of increase of CO2 in our atmosphere, due to fossil fuel combustion, is faster in warm years than in average or cooler-than-average years. These analyses have further suggested that the rate of CO2 increase slows in the year, or perhaps even in the two years, following the unusually warm year.
"The first goal of our study is to see if this pattern occurs following a warm year under the more controlled conditions that we can deliberately impose in our unique DRI facility. A more important aim for us, though, is to understand to what extent the temperature-induced changes in plant processes and the rate of soil organic matter breakdown-such as what occurs in your compost pile-reflect the patterns that have been observed at the global scale.
"In other words, can we discover the mechanisms that may underlie the observed global patterns?"
The Went Laboratory permits exacting analyses of every aspect of intact ecosystems operating under precisely controlled conditions. The EcoCELLs permit scientists to observe how processes that occur on the level of an individual organism over the course of a few seconds or minutes, scale up to processes that occur over entire ecosystems over the course of days, months, or years.
Researchers can adjust environmental conditions inside the EcoCELLs to simulate actual or projected conditions, i.e., future levels of atmospheric CO2, and track the response of individual plants, plant communities, the interaction of various species and the changes in soil chemistry and root zone characteristics.
To get the soil monoliths into the Frits Went Lab, contractors had to cut 40-foot long transparent greenhouse roof sections into two pieces and restructure the metal superstructure supporting the roof prior to the arrival of the soil. Special precautions, approved by the Nevada Department of Agriculture, were taken to prevent the introduction of potentially invasive plant and insect species into Nevada's rangeland ecosystem.