Minimizing soil erosion speeds recovery after wildfire

The task is daunting – everywhere is chaos, disruption, charred trees, and scorched earth. Where do you begin? The most important task after a fire may be to understand the natural processes at work in the landscape. Nature has equipped many plants to recover quickly after fire, often the necessary ingredients for recovery are already at hand in the forest soils. Root systems, dormant seeds, nutrients released by the fire, and additional sunlight and warmth from opening the forest canopy, all contribute to restoration of the forest. That is why it is so important to stabilize the soil after a fire. The soil contains the keys to restoration, it is important to protect it from erosion during the critical period after a fire.

By Ellen Nelson
Larimer County Weed District

In the short term, before plants begin the recovery process, minimizing soil erosion is the most important thing a landowner can do to speed recovery after a wildfire. The burn severity determines how vulnerable to erosion an affected area is. High severity fires (slow-moving and very hot) consume all forest vegetation, trees, shrubs, grasses, duff on the forest floor and even shallow roots. All of this material formerly served to slow runoff, absorb water and protect the soil. Instead the soil may now have a hard, waxy coating, and actually repel water, a condition termed hydrophobicity. This water repellent layer will need to be broken up to increase water infiltration and facilitate successful plant reestablishment. Raking, harrowing and animal hoof action, all facilitate breaking the hydrophobic crust. Natural processes such as freezing and thawing and the re-establishment of the soil microbial community will serve the same purpose.

Additional immediate steps that can help to stabilize the soil include: constructing contour terraces using fallen trees or straw wattle barriers; reseeding; mulching with certified weed-free straw; installing silt fences or straw bale check dams in drainages; using water bars to slow and direct the flow of water off trails and roads. Technical fact sheets detailing how to efficiently and easily implement these practices, and more expert advice on fire rehabilitation are available online at http://www.co.nrcs.usda.gov/news/pas/2012_Fires/2012_Fires_High_Park.html and http://www.co.larimer.co.us/highparkfire or from the local Natural Resources Conservation Service, Fort Collins office at 2150 Centre Ave., Building A, Suite 116, 970-295-5655.

The root systems of many plants run deep and in many areas will have escaped fire temperatures sufficient to cause death. When the plant is burned, the roots may survive and be stimulated to send up new shoots. Soil that has not suffered severe temperatures will contain dormant seeds waiting for the right conditions to germinate and grow. Many trees are adapted to fire and rely on it to regenerate new stands. Some types of cones require fire to open and release their seed. The seeds of many shrubs and forbs can persist in the soil for years. Fire often opens an area to more sunlight and warmth resulting in germination with subsequent rains. Many grasses and shrubs will re-sprout within weeks of a wildfire.

Healthy forests are ecological life-support systems that we all benefit from. Forests are assets that we generally take for granted as “free” benefits for all of us: wildlife habitat, watersheds, water storage and carbon sequestration in addition to natural and scenic beauty. These natural assets are often undervalued, and when undervalued, our forests are increasingly susceptible to development, overuse and degradation. Healthier forests provide society with more of these intangible assets and in addition, recover more rapidly from natural stresses such as mountain pine beetle, and wildfire. These natural recovery processes are already at work in the burn areas, providing real-time demonstrations of the amazing resilience of natural systems.

These natural processes promoting re-growth and restoration also apply to weeds and other less desirable vegetation. Many Noxious Weeds are adapted to fire and may take advantage of the soil nutrients released by the fire and the additional sunlight in formerly forested areas. For more information on managing weeds after wildfire contact the Larimer County Weed District. The Larimer County Weed District provides advice to landowners on managing noxious weeds. The Weed District provides free site visits, plant identification, advice on controlling noxious weeds, and land and pasture management guidelines. Contact the Larimer County Weed District at 970-498-5768 or larimer.org/weeds/