A Conversation About Fire and Water

Forest Service research fellow rides the Canadian airwaves during international conference

by Stephanie Worley Firley
A large part of the Douglas fir and larch forest outside the city of Kelowna, Canada, was burned in the 2003 Myra Canyon fire. Forest recovery in the Interior Plateau is slow due to low annual precipitation and nutrient-low soils, as seen in this photo from July 2015, 12 years after the wildfire. Photo by Dennis Hallema.

A large part of the Douglas fir and larch forest outside the city of Kelowna, Canada, was burned in the 2003 Myra Canyon fire. Forest recovery in the Interior Plateau is slow due to low annual precipitation and nutrient-low soils, as seen in this photo from July 2015, 12 years after the wildfire. Photo by Dennis Hallema.

For hydrologist Dennis Hallema, a recent conference presentation in Kelowna, British Columbia, turned into an opportunity to speak about an urgent research issue in front of an even larger audience. Following his talk at the 4th International Conference on Forests and Water in a Changing Environment, Hallema (an Oak Ridge Institute for Science and Education fellow working with the Eastern Forest Environmental Threat Assessment Center) was approached by a producer for CBC Radio One. The following morning, Hallema spoke live on air with CBC host Chris Walker about the effects of wildland fires on water supply in the United States. Their discussion focused on a collaborative study that began in October 2014 with funding from the Joint Fire Science Program. The interview, which was broadcast July 8 on CBC Radio One Daybreak South, is summarized below.

Have we seen more fires in recent years?

Our project funded by the Joint Fire Science Program focuses on the continental U.S., where, since 1984, we have regionally observed more stand-replacing fires in, for example, the Sierra Nevada, Southern Cascades, and Nevada. Burned area has increased in the Southern Rockies and Colorado Plateau. In the eastern U.S., on the other hand, fire severity often is lower due to a transition toward closed-canopy forests with more shade-tolerant and fire-adapted species, and fires are smaller due to stricter suppression requirements of the dense population living in this area.

What do forest fires have to do with water?

Approximately 50 percent of our fresh water comes from forests, so if wildfires impact water supply, we need to know. The persisting drought in the western states has added the question, how does drought affect the link between wildland fires and water supply?

So how do fires affect water? Were you able to identify a relationship between wildland fires and water supply?

One early study in the 1950s in a southern California watershed found a more than 100 percent increase in storm runoff in the year following the 1953 Barrett high-severity fire, and a number studies followed in different areas; however, there is no general picture of how this works and whether there are national patterns in fire effects on water. We know that fire removes the canopy and temporarily reduces forest transpiration. Normally trees use water and transpire water through their leaves, but fire largely eliminates these mechanisms so that more water runs off and increases streamflow for some time, and erosion and landslides may be the result. The situation is, however, more complex than that since high-intensity fires can render the upper part of the soil water-repellent, which can in turn lead to either more or less runoff depending on the conditions of the area. We have found different conclusions for different areas.

How are you studying these areas? What are some of the conclusions?

We used an approach in which we combined large-scale climate data, burn severity data, streamflow data and evapotranspiration data coming from satellites. First we identified candidate watersheds based on burned area and available stream flow data, and after that we analyzed more than 30 watersheds in different parts of the U.S. in more detail. It looks like streamflow was higher than expected based on precipitation and snowmelt in some 15 watersheds (13 of these have had wildfires, one had a prescribed burn, and another had both a wildfire and prescribed burns). In 12 watersheds, we found no change in streamflow, and streamflow was lower than predicted in nine watersheds. We are now using a computer model to explain the mechanisms that cause these differences.

What can British Columbia do to reduce fire impacts on water?

Our project aims to establish the long-term impact of fire on U.S. watersheds by using local observations and large-scale computer models, and this will eventually lead to a scientific report. Policy makers can use this report to decide what strategies to follow, while our team focuses on the scientific questions.

Read more about this study in a recent CompassLive post.

For more information, email Dennis Hallema at dwhallem@ncsu.edu.

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Posted in Fire, Forest Watersheds, Threats

Faces of the Forest Service: Bill Hargrove

Once a skeptic, a landscape ecologist is now a leader in his field

by Stephanie Worley Firley
Bill Hargrove is an entomologist by training, and now conducts ecological research at the landscape scale.

Bill Hargrove is an entomologist by training, and now conducts ecological research at the landscape scale.

Bill Hargrove likes to wear “loud” shirts, as he describes them—playful prints that reflect the colors and shapes of the natural world as well as a sense of humor that’s hard to match. But it isn’t just his shirts that cause Hargrove to stand out in a crowd. His big ideas and passion for taking them to the next level have made Hargrove a prominent researcher in the field of landscape ecology—a broad discipline that examines patterns and processes across large areas. That wasn’t necessarily his plan, though.

When he was pursuing a Master’s degree in entomology, he worked at the Coweeta Hydrologic Laboratory in North Carolina. When he first heard some researchers talking about landscape ecology (a new idea at the time), he was skeptical. “My fellow graduate students and I weren’t sure what to think about that, because we were ecosystem-level ecologists doing watershed-scale work, and we thought that was the largest scale anybody could ever manage! How could one ever hope to study ecology at the landscape scale?!” he says. But as technology began to explode, so did the possibilities.

“Two things happened that changed my mind about landscape ecology: the maturation of Geographic Information Systems (GIS) and remote sensing technologies, and the explosion of desktop workstation computers. Suddenly I realized that there really was a way to study ecology at scales larger than ecosystems. So I pursued a PhD in ecology—large-scale ecology.”

Now, Hargrove applies landscape ecology every day as a scientist with the Eastern Forest Environmental Threat Assessment Center in Asheville, North Carolina, a position he has held since 2006. He is the lead researcher for ForWarn, an online system based on NASA satellite imagery that recognizes and tracks vegetation change across the United States. ForWarn provides land managers and other users with weekly GIS maps showing the effects of disturbances such as wildfires, wind, insects, diseases, and year-to-year variations in climate as well as post-disturbance recovery. “It’s a customized tool that helps managers address the problem of monitoring lands at a large scale,” explains Hargrove.

Developing the ForWarn system has been an exercise in creative thinking—something that Hargrove relishes. “I feel like I’m searching for the missing pieces to bridge between research and the applied community of forestry practitioners,” he says. “Dac Crossley, my former professor and mentor, had a saying: ‘Have fun, do science.’ I think the order is important. There’s a big creative aspect to science. In fact, I think there’s just as much creativity in science as there is in art. I strongly believe that there is a vast, fertile plain between what is possible and what is routinely done. And I never know where this endeavor will take me next.”

Hargrove and the Eastern Threat Center will welcome hundreds of landscape ecologists to Asheville in April 2016 as hosts of the annual meeting of the US Regional Association of the International Association for Landscape Ecology (US-IALE).

For more information, email Bill Hargrove at whargrove@fs.fed.us .

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American Chestnut, Past and Future

by Sarah Farmer, SRS Science Delivery Group

American chestnut catkins starting to bloom. Photo by Keith Kanoti, courtesy of Bugwood.org.

The Silvics of American Chestnut , a general technical report (GTR) available from the U.S. Forest Service Southern Research Station (SRS), describes the habitat, life history, special uses, genetics, and restoration of the American chestnut (Castanea dentata).

The publication is the result of collaboration between G. Geoff Wang, the lead author, his colleagues at Clemson University, and Stacy Clark, a research forester with the SRS Upland Hardwood Ecology and Management unit.

Until the early 20th century, American chestnut was one of the most ecologically, culturally, and economically significant trees of the eastern United States. However, the accidental introduction of an exotic pathogen, the chestnut blight (Cryphonectria parasitica), devastated the chestnut population, causing the species to become functionally extinct.

Because of American chestnut’s long absence from the landscape, standard silvicultural handbooks such as the USDA Woody Plant Seed Manual have not included complete information about the species’ life history and growth habits. This publication supplements silvicultural handbooks by summarizing information about American chestnut that will be important to future restoration efforts.

The GTR’s authors point out that restoring chestnut on most sites requires artificial regeneration — growing the blight-resistant trees recently developed in a greenhouse or nursery and planting them as seedlings — rather than starting from seed. They also caution that even if the chestnut trees prove to be blight-resistant, the effects of damaging agents other than blight, including root rot disease and insects that defoliate leaves or damage roots, may represent real barriers to restoration.

American chestnut was once a dominant and widespread canopy tree through many parts of the country, its range stretching from Mississippi to Maine. Its nuts were consumed by animals and people alike, and it was widely used as timber. “Chestnut’s demise is regarded as the most tragic ecological event in the post-glacial history of eastern North American forests,” says Clark. “Its return from the brink of extinction would be one of the greatest success stories in the history of forest management.”

For more information, email Stacy Clark at stacyclark@fs.fed.us

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Posted in Genetics, Insects and Diseases, Restoration, Upland Hardwoods