Management Guidelines for Reducing Fire Effects on Soil Erosion and Water

Although large soil losses following fires is not as common in the South as in western areas, land managers should still assess the susceptibility of their particular site to soil damage and erosion and follow guidelines below for mitigating these potential effects. These guidelines primarily list steps that can be taken before before planned burns. For information on steps that can be taken after wildfires to minimize soil erosion, see Burned Area Emergency Rehabilitation.

Guidelines for Controlling Soil Heating and Loss of Organic Soil

Fire may cause erosion by removing protective coverings of vegetation, surface litter, duff, and/or root mats. Ensuring that some ground cover remains following fire is one of the most important precautions managers can take to reduce the susceptibility of a burned area to erosion. Fires also contribute to erosion by heat-induced changes to soil physical properties; therefore controlling the amount of soil heating can also mitigate fires’ effects on erosion. The amount of soil heating and/or loss of organic matter caused by prescribed fires can be reduced by controlling the following factors:

• Burning while the moisture content of large diameter fuels, lower duff, and soil is high limits the amount of heat penetration into lower soil surfaces. Moisture not only protects the duff layer adjacent to the soil, but also prevents the fire from consuming soil humus and prevents heat damage to soil.
• Pile burns or windrow burns cause more intense soil heating in localized areas than broadcast burns. Also hand piles tend to burn more quickly than machine piles.
• Burning slash while it is still green with cause less soil heating than burning cured slash.
• Utilizing or yarding more material in areas with heavy dead and down fuel loads can decrease the potential amount of soil heating.
• Rapid ignition techniques (aerial drip torch, for example) can sometimes be used to shorten the duration of the burn and the amount of soil heating.

For guidelines on how to minimize damage to organic soils during burns, see Organic Soils: Management Concerns for Prescribed Burners.

Guidelines for Protecting Riparian Areas during and after Fires

The following precautions should be taken when burning riparian areas near waterways to help to reduce sedimentation and contamination:

• Buffer strips along riparian areas should be left to stabilize slopes and decrease the potential for stream sedimentation. Width of buffer strips should follow applicable agency policy.
• Riparian areas can be burned in spring when conditions are favorable for rapid vegetation recovery.
• Fire retardant chemicals should not be used in or near waterways. Fire retardant has the greatest impact on small or slow moving bodies of water.
• Restrict the location of firelines to gentle slopes along the contour. Avoid firelines that lead directly into watercourses on erosive soils and or steep slopes. If this is unavoidable, install water bars and leadoff ditches at regular intervals.
• Rehabilitate any firelines that were constructed as soon as possible. Replacement of soil and plant material removed during construction is an effective method of fireline rehabilitation.
• Leaving large woody debris and duff can help to protect soil from erosion, and aid nutrient cycling and mycorrihzal function following burns.
• Take extreme precaution when logging slash is burned on steep slopes. Surface runoff and soil erosion may occur before vegetation colonizes sites.