CSU researchers study black carbon to learn environmental impact of wildfires

Anyone who drove through the Poudre Canyon after the devastating High Park Fire of summer 2012 saw alarming effects: 136 square miles of scorched landscape in the foothills northwest of Fort Collins, river banks lined with sooty muck from forest runoff, and blackened water in the Cache la Poudre River.

What could this charred terrain mean for forest recovery and for the river that is a vital municipal and agricultural water source across northern Colorado?

A team of Colorado State University environmental scientists has landed a $200,000 grant from the eminent National Science Foundation for a yearlong study of what happens to black carbon – the singed plant matter and sooty soil left from wildfire. They hope to better understand the effects of black carbon on the forest and watershed, and its implications for the planet’s carbon cycle.

“Black carbon is a hot topic because we don’t know much about its fate into the environment, and we have a poor understanding of its role in global carbon cycling,” said Francesca Cotrufo, a professor in the CSU Department of Soil and Crop Sciences who is leading the investigation.

Indeed, a comprehensive study of black carbon in the atmosphere, published in mid-January in the Journal of Geophysical Research: Atmospheres, grabbed global scientific attention. The study found that atmospheric black carbon, or soot, is the most damaging greenhouse agent behind carbon dioxide and has twice the power previously thought to spur global warming.
That’s the black carbon we know as air pollution. What about the role of black carbon that’s created during wildfire and left as residue?

Its impact on soil, water and the long-term carbon cycle are relatively unknown and also could be significant, especially because many scientists expect wildfires to become more frequent and intense in the face of climate change, said Keith Paustian, also professor in the CSU Department of Soil and Crop Sciences and a cooperator on the new study.

The soils researchers, like countless other northern Colorado residents, were stunned to see results of the lightning-sparked High Park Fire, which during June 2012 killed one person, destroyed 259 homes, and scorched more than 87,000 acres of public and private forest land. Cotrufo and Paustian, like some other CSU scientists, also realized the university’s burned back yard could provide an unparalleled case study of Western wildfire and its consequences in a time of drought and climate change.

Working with the soils duo is Mazdak Arabi, an assistant professor in the CSU Department of Civil and Environmental Engineering. The researchers also are collaborating with other CSU scientists studying the High Park Fire, and with experts from the Arapaho and Roosevelt National Forests.

The National Science Foundation awarded the group a special Rapid Response Research grant, called a RAPID grant, designed for studies that are urgent or represent quick scientific response to natural disaster.

“We really want to know what happens right after a fire, before effects of the disturbance have been altered, and our team had the ability to strike quickly,” said Gene Kelly, head of the Department of Soil and Crop Sciences. “This study is fundamental to understanding how carbon moves around the ecosystem, and the data can also be used to understand and assist in recovery.”

Cotrufo and her colleagues begin their investigation assuming that up to 10 percent of the carbon produced in a wildfire may be converted to black carbon and deposited in the soil. Now they want to know:

• What was the exact rate of black carbon production during the High Park Fire?
• What was its rate of deposition and accumulation deeper in soil?
• What about the rate of runoff, and deposition along Poudre River banks and in stream-bed sediments?
• What are the broader effects of these fates and fluxes on the global carbon cycle that supplies an essential element for all life – and also has the ability to protect or parch the planet, depending on its balance.

The team has actively sampled soil, sediment and water in the High Park burn area and will compare characteristics with those of samples collected before the fire. These data then may be used in models to better understand the broad environmental consequences of black carbon in fire zones and watersheds.

“This study will provide valuable measurements in support of a more mechanistic understanding and modeling of black carbon dynamics in mountain ecosystems increasingly prone to fires,” according to a summary of the CSU project. “After the many fires of 2012, the general public is more than ever interested in their causes and consequences.”

The CSU team will share its findings with the campus community through a public forum, and is assisting with a project for statewide schools to foster deeper understanding of wildfire.

Read about the study, “Full Accounting of Pyrogenic-C Dynamics at the Watershed Scale: A Unique Opportunity Offered by the High Park Fire” at www.nsf.gov/awardsearch/showAward?AWD_ID=1261383&HistoricalAwards=false

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