We only have a fragmented understanding of the complex interactions that go on in the dirt as water flows past soil and microbes. To gain fresh insight into the hydrologic processes that make life on land possible, the University of Arizona has built a trio of massive, man-made hillside labs.
Just recently, the $US200 million Biosphere 2 project in Oracle, AZ, was on its last legs. Both of its high-profile habitation experiments in the 1990s had ended in failure, and the facility was slated for demolition to make way for a resort. Then, in 2011, the University of Arizona purchased it for use as a massive laboratory dedicated to studying climate change. As part of the project's decade-long plan to study how a warming atmosphere affects the movement of water, UA has constructed the world's largest (well, only) artificial water shed.
Dubbed the Landscape Evolution Observatory (LEO), this facility consists of three 100-foot long, 40-foot wide troughs tilted at a 10-degree angle, housed within a 53,000 square foot sealed greenhouse. This allows researchers to precisely control environmental variables in ways not possible in conventional large-scale observational studies.
Each trough is filled with three feet of finely-crushed volcanic rock, a 600-ton layer that mimics Arizona's local geologic conditions in antiquity. As the crushed rock slowly converts into soil, more than 1800 sensors in each slope accurately measure soil moisture, chemistry, temperature, and the types and quantities of gases emitted. Load cells have also been installed at the base of these 1100-ton structures to monitor changes in their total weight.
"It's the first time anyone has built an instrument like that," Biosphere 2 Science Director Peter Troch said in a press statement. "LEO provides the scientific community with a tool to learn about the landscape in ways we haven't been able to before. It will help us to really understand Earth's surface processes."
The first three years of this experiment will study abiotic processes — how rainfall and overland flows reshape the ground's surface, how long it takes water to flow through various soil densities, and how moisture is distributed through them. After the first 36 months, researchers plan to install heat- and drought-tolerant vascular plants into the landscapes and observe how they affect these abiotic processes along with the rest of the system.
"In a laboratory, you can really control an experiment and understand everything that goes in and out, but it doesn't really tell you much about how big systems interact," said Stephen DeLong, the project's lead scientist said. "Here we can see how big systems interact."
Image: UA School of Architecture