Fire and water

By: Melissa Schneider / Published: Apr 28,  2009

Scientists study how fire may affect key functions in marshes


(MOSS POINT, Miss.) – Natural resource managers often use prescribed burns in forests to reduce fuels, improve habitat and prepare sites for seeding and planting. When it comes to black needlerush (Juncus roemerianus) marshes, less is known about the potential benefits or drawbacks of using fire for management purposes.

Coastal wetlands are important to communities because they lessen the strength of storms, reduce flooding and offer biodiversity for recreational activities and coastal economies.

In a research project funded by the Mississippi-Alabama Sea Grant Consortium, scientists are studying how fire affects water quality, plant production and soil accretion (the increase of land along the shoreline) at the Grand Bay National Estuarine Research Reserve in Moss Point, Miss.  

Julia Cherry, an assistant professor at the University of Alabama in the Department of Biological Sciences and New College, is co-leading the project with Christopher May of The Nature Conservancy.

While fire is not necessarily thought of as something that could affect elevation in marshes, it could, Cherry said.

“Prescribed burning may be a useful tool for enhancing elevation gain in marshes threatened by submergence due to sea-level rise,” she said. “We are trying to figure out what affects the ability of these marshes to persist in the long term. Some processes might be more important than others.”

The team of scientists, which includes Cherry and May, UA Graduate Student Anna Braswell, Grand Bay NERR Stewardship Coordinator Will Underwood and Stewardship Associate Jay McIlwain, is observing soil chemistry, plant production and accretion before and after controlled burns on test plots at the reserve.

The findings may determine if fire had a positive or negative effect on nutrient availability, accretion, plant mass and plant diversity.

To test soil accretion, the scientists use a probe to take soil samples and measure any gains or losses using a white marker layer in the soil. To estimate the amount of aboveground plant material, scientists collect plant stems in a specified area, dry them and weigh them. To quantify belowground plant material, they cored holes in each plot at the reserve and filled them with a root-free peat, which is very light in color compared to the existing soil. On return trips to the field, the holes are cored again to determine how many roots have grown into the peat over time.

To monitor water quality, the scientists withdraw water from the soil and sample it in a lab for acidity, salinity, sulfides, nitrogen and phosphorus. They also measure the extent of soil flooding using platinum electrodes.

The scope of the project, which originally included studying the affects of burning large piles of dead plant material and wood that washed up during Hurricane Katrina, has changed. The debris disappeared last year when Hurricanes Gustav and Ike raised waters and took it out to sea.

Braswell, however, is taking that issue into a greenhouse environment at the university, where she will measure variables and elevation change in response to burns and hurricanes.


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