a.e. araiza / arizona daily star

More Photos (5):

Other articles by Eric Swedlund:

Pecan exec dies in plane crash Manager of Green Valley pecan farm killed in plane crash Police chief eyes new policy on entrant reports Desert yields body of smuggler Marijuana smuggler killed by bandits south of Tucson, authorities say Monsoon's not over yet, thunderstorm shows Mexican man is suspect in S. Side killing Man arrested in death of his girlfriend in OV Boy, 11, locked in 'reeking' room; 2 held Tucson boy, 11, locked in 'reeking' room, detectives say

Health Care
Dependable Health Services
Physical Therapists Health Care
CENTRAL ARIZONA COLLEGE
DIRECTOR OF HEALTH INFORMATION MANAGEMENT Administrative & Professional
Jorgensen Brooks Group
Counselor Health Care
Sierra Tucson
Eating Disorders Program Coordinator Mechanical
Komatsu Equipment Co
Resident Field Mechanic Administrative & Professional
Tucson Urban League
CEO/President Sales and Marketing
Everready Glass
Sales Reps

The UA's first experiments are under way inside the newly acquired Biosphere 2, with two doctoral students leading studies on the impact of drought on piñon pines and how plant density affects water levels in soil.

Both experiments depend on the large scale and high level of control afforded by the 3.14-acre miniworld, and both are thematically linked to the UA's centerpiece study, a 10-year, multifaceted effort to understand how water interacts with simulated hillsides populated with a variety of desert and savannah plant life.

B2 Earthscience, the UA initiative leading the Biosphere experiments, is broadly seeking to understand how water behaves in different ecosystems and how climate change and drought affect the interactions between soils, plants, water and the atmosphere.

"We hope we can focus a question in here and work on the instrumentation and then we can go ask better questions in the field," said Travis Huxman, director of Biosphere 2 and a UA associate professor of ecology and evolutionary biology.

The early experiments are crucial for the UA to demonstrate the scientific value of the Biosphere, an often-maligned facility initially built as a prototype of a self- contained environment that humans might live in on another planet.

Biosphere 2 founder Ed Bass has given the UA $30 million over 10 years, to be split evenly between operating costs and research funding.

But to make the facility viable as a long-term laboratory, the UA must demonstrate it can generate its own outside research funding, primarily through highly competitive federal grants.

Such progress is necessary if the UA is to successfully manage the Biosphere beyond its initial three-year lease, or potentially one day acquire the facility, which costs about $1.5 million a year to operate.

"In the long run, we have to make this facility sustainable," Huxman said.

The UA's centerpiece experiment will take about 20 months to prepare, with three complex hillsides to be built in the Biosphere's former farm area.

The hillsides will start out bare, and researchers will simulate rainfall, measuring the hydrology in the absence of vegetation. Then grass will be added to two slopes and finally shrubs added to one slope.

The experiment will measure the water, from rainfall to runoff, evaporation and absorption by both the ground and water, and compare it to water behavior on hillsides replicated outside the Biosphere. Leading up to that study are the two experiments that have just begun.

Henry Adams, an ecology and evolutionary biology doctoral student, is leading the research that will force piñon pines through simulated drought conditions, with one group of trees at normal temperature and another group in the Biosphere's hotter desert region.

"No one knows exactly what it takes to kill a tree with drought," said Adams, who set up the experiment to isolate the effects of drought, which is typically entangled with bark beetles and harmful pathogens in the natural world.

The piñon pines are from northern New Mexico, between 30 and 50 years old and about 4 to 8 feet in height. Two groups of 14 trees, half to be watered and half left to "drought," will be inside the Biosphere, and two other groups will be placed in mountains near Tucson.

During the 18-month experiment, researchers will measure photosynthesis and respiration and continually monitor soil moisture.

They'll also test the water potential, which creates more tension in a tree as the drought goes on. A healthy tree has the ability to transport water to its leaves easily, but a stressed tree is under tension to perform the same act.

"We can compare and experimentally test the effect of increases in temperature on the trees, how they respond to drought and how fast they die," Adams said.

Huxman said the research will advance scientists' understanding of how trees behave under drought conditions and could have big implications on land-use decisions.

"We know that if you withhold water, eventually metabolism stops, but we lack a physiological model for predictive science," he said. "If we can describe this physiological mechanism well, we can start to predict these massive die-offs before they happen."

In the second experiment, watershed management doctoral student Juan Camilo Villegas is studying how plants change their environment, particularly in regard to how water evaporates.

In arid regions, about 85 percent of precipitation evaporates, but what isn't known is how much of that water evaporates directly and how much is lost through transpiration, the process of water passing through plants into the atmosphere.

Villegas is trying to disentangle the two components of the overall evaporation process.

Using mesquite trees in boxes, Villegas will populate a specific area with more and more trees, from zero coverage to a full tree canopy.

The trees will be subjected to rain at each stage and then Villegas will measure the patterns of water loss, both through evaporation and transpiration.

The experiment will track how the evaporation-transpiration ratio changes as the amount of vegetation changes, with the under-the-dome setup duplicated at two places right outside the Biosphere.

Like Adams' experiment, Villegas' work is tied into current field research projects as scientists push for a better understanding of what type of insights and breakthroughs can be found at the scale the Biosphere offers. It can validate models of research or lead to improved research protocol to use in the field.

"This large-scale Earth science needs a model that we can tweak," Huxman said.

Read in-depth coverage of environmental issues, learn what you can do to conserve resources and find information about recycling at azstarnet.com/environment