Colorado State University soil scientists are investigating the 2002 Hayman fire site for the first signs of life – microbial life – and testing strategies that will help prevent erosion and test tools that help future fire sites recover more quickly.
The team consists of Mary Schutter, soil microbiology assistant professor; Troy Bauder, Colorado State University Cooperative Extension water expert, and Greg Butters, soil hydrologist associate professor; and faculty affiliate Robert Brobst, science coordinator of the Hayman Fire.
The group began looking a how the site was recovering as soon as they could step foot on the 137,000-acre, moon-like landscape, where experts say fire temperatures reached in excess of 400 degrees Celsius – that’s a balmy 752 degrees F – and at least one area reached more than 650 degrees C, more than 1,200 degrees F. At a mere 50 degrees C, soil life – the small single-cell organisms that live in the soil – begin to die. At 300 degrees C, organic matter including grass, trees and mulch are destroyed.
Together, the group is looking for the first signs of life and investigating treatments that will prevent erosion, such as those that cause soil to clump into larger pieces that are not as likely to be carried off by water.
"The regeneration of soil life, such as fungi, is the first step to soil recovery after a fire," said Schutter. "We hope that some fungal spores are heat resistant so that they can survive fires and regenerate themselves. Otherwise, we have to wait for them to grow back from the outside fringes of a fire."
In some areas, where the fire did not reach the most extreme temperatures, soil life survived. Schutter will continue to test soil samples into next fall and winter to measure the rate at which the fire site is regenerating and also will measure whether or not soil treatments such as hydromulch, a foamy man-made material that is commonly applied to areas burned by wildfire, speed up vegetation growth.
While Schutter focuses on discovering the first signs of regenerating life on the burn site, Bauder and Butters look for clues and tools that will help prevent erosion. When organic matter burns in a hot forest fire, it forms a waxy layer on the ground. This layer makes the soil hydrophobic, which means that water beads up on the surface of dirt instead of soaking into the ground, like water on a freshly waxed car.
"The waxy layer is fickle – if water sits on the surface long enough, it begins to soak into the first few millimeters," said Butters. "But as soon as the water dries up, the waxy layer returns. Because the ground is not able to soak up water very efficiently, water begins to run on the surface and eventually erodes the soil." The waxy layer is perhaps one of the more damaging aspects of forest fires because it increases the probability of severe erosion, floods and surface water pollution to nearby rivers, lakes and reservoirs.
Soil can remain hydrophobic for two to three years, depending upon several factors including the original conditions of the fire that initially caused the waxy layer as well as the soil and vegetation in the area at the time of the fire, said Butters. Hydromulch may speed up the destruction of the wax, which disintegrates naturally over time. But no one really knows why hydromulch works or how it works. Butters will focus on understanding why these treatments work, why microbrials in the soil respond well to them and possibly unlock the secrets that other research should focus on to improve the use of the mulch in future applications.
During heavy rains, the waxy layers act as pavement and causes runoff, which can cause flooding. This runoff causes erosion as it picks up ash and other fine soil particles and carries them to streams and lakes, which might affect drinking water sources and water quality. Bauder, a water quality expert, has been evaluating a tactic that has reduced erosion on farms. Adding polyacrylamides, an environmentally friendly, water-soluble substance, to the topsoil helps soil bind into particles that are too large to be carried away by typical runoff. The polyacrylamides, called PAM, binds particles of silt and clay together, making them more resistant to erosion.
"In irrigation tests, PAM increases sediment by up to 90 percent," said Bauder. "It’s fairly cheap and it breaks down in sunlight so it doesn’t stay in the environment long. I’m trying it on soil from the Hayman fire site to see if fire-damaged soils are fundamentally changed so that PAM won’t help binding. If it works, I’d like to find out why."
Brobst oversees the project, which is funded with a $40,000 EPA grant. He specializes in looking at changes in soil over a period of time on burn sites, concentrating on soil and water quality issues.