Characteristics of prescribed burns and resultant short-term environmental changes in Populus tremuloides woodland in southern Ontario

Abstract

In a series of prescribed burns of low intensity and short duration in southern Ontario, wind speed, amount of fuel, and fuel moisture were important environmental controls of fire severity. A heterogenous pattern of burning, related to clumping in the vegetation and to a hummock–hollow microtopography presumably affected and was perpetuated in the reestablishing postfire vegetation.Removal of vegetation cover and surface litter plus surface albedo changes resulted in increased soil temperature 2 months after burning. These increases were short-lived and soil temperatures were close to those of unburned areas 4 months after the prescribed fires. Despite their small magnitude and short duration, the soil temperature increases could have an important stimulatory effect on regenerating vegetation.Significant increases in levels of readily available forms of phosphorus, potassium, calcium, and magnesium at surface soil depths immediately after burning could have been depleted through uptake by vegetation and microorganisms. Portions of the nutrients were removed, also, by erosion of fly ash during burning, leaching to subsurface depths, and through fixation in unavailable form.