The zone from the treetops to the bottom of the groundwater table has been dubbed the "Critical Zone" because of its key role in processing and cycling water, carbon, and nutrients necessary for life.

Now an interdisciplinary team of researchers will establish a "Critical Zone Observatory" in the Southwest with the help of a five-year, $4.35 million grant to the University of Arizona (UA) from the National Science Foundation (NSF).

"We think of the critical zone as being a living filter for the hydrological cycle," said principal investigator Jon Chorover, UA professor of soil, water, and environmental science.

"We know a lot about geology and rocks, and we know a lot about communities of plants that exist in different climatic zones, and we know a lot about fertility of soil. However, we don't understand how the components all interact to create this filter at the surface of the earth that helps to clean and store our water," Chorover said.

To figure out how the ecological, geological and hydrological components of the critical zone interact, he and his colleagues will study two different mountain-and-basin areas in the desert Southwest — the Santa Catalina Mountains outside Tucson, Ariz., and the Valles Caldera National Preserve near Los Alamos, N.M.

"In the arid Southwest, a lot of the water we all depend on is derived from relatively local high-rainfall environments," Chorover said. "Mountains in the Southwest are areas that suck water out of the sky and bring it down into our basin aquifers."

The UA-led effort is called the Jemez River Basin-Santa Catalina Mountains Critical Zone Observatory. The Valles Caldera drains into the Jemez River basin. The NSF has funded four such CZOs in different climatic zones throughout the U.S.

For more information, go online to: http://uanews.org/node/27571.