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Secrets of the soil: NSF Career award winner Heather Throop leads study of CO2

The steady increase in carbon dioxide in the atmosphere from human activities and natural biological processes has had a significant influence on climate patterns around the world. Improving predictions of how temperature, drought, or extreme rainfall might change in the future is becoming a major concern.

Biology professor Heather Throop demonstrates how to use a portable gas exchange system to measure CO2 (carbon dioxide) uptake in plants. (NMSU photo by Darren Philips)

To enhance understanding of the pat¬terns of carbon storage in desert soils, New Mexico State University Assistant Profes¬sor of Biology Heather Throop and her team of student researchers are conducting research on desert plants and soils.

"We're trying to understand how changes in desert vegetation affect the amount of CO2 taken up from the atmosphere by plants and stored in plants and soils," Throop said. "Each year, the amount of CO2 released into the atmosphere by soils is 10 times greater than the input from fossil fuels. Because of this, even tiny imbalances in the uptake and release of CO2 from natural systems can affect the amount of CO2 in the atmosphere. My lab group is trying to understand how des¬erts fit into the global picture."

A recent $859,000 National Science Foundation Early Career Development Grant to Throop will allow her group to expand this work. This is NSF's most prestigious award in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integra¬tion of education and research within the context of the mis-sion of their organizations.

Throop came to NMSU in 2006 after completing a prestigious National Oceanic and Atmospheric Ad¬ministration Climate and Global Change postdoctoral fellowship at the University of Arizona, where she first began studying relationships between desert soil, vegeta-tion and carbon cycling.

"I'm really interested in how individu¬al organisms influence large-scale processes such as the exchange of carbon between the earth and the atmosphere," Throop said.

During photosynthesis, plants take up CO2 from the atmosphere. When plants die or shed leaves, some of this carbon can become stored in soils for many years. Throop said there has been a worldwide shift in desert vegetation over the last 150 years, with a decrease in grasses and an in¬crease in shrubs. Scientists don't know how this shift will change the amount of carbon stored in desert plants and soils.

To study this, Throop and her team of 10 student researchers conduct fieldwork throughout the desert Southwest. They col¬lect plant and soil samples, and then analyze them for chemical composition in the labo¬ratory. This work has improved estimates on how changes in desert vegetation affect the amount of carbon in soils. Throop's Early Career grant will allow this work to be expanded to use new analytical techniques to trace the sources and residence time of carbon in desert soils.

"The information derived from this research will be crucial for improving predictive models of future atmospheric CO2 concentrations," Throop said.

In a related set of research projects, Throop and her team are looking at the breakdown of dead plant material and how it affects ecosystem carbon storage in deserts. Throop is the princi-pal investigator for more than $500,000 of active research funding for these projects, via grants from the NSF, Interna¬tional Arid Lands Consortium, and an NMSU/Los Alamos National Lab Memorandum of Understanding.

By carrying out this research, Throop and her team hope to both improve predictions of how vegetation change in deserts will affect future atmospheric CO2, and also inform land management strategies for enhancing carbon storage.