Effects of broadcast slash burning on fuels and soil chemical properties in the Sub-boreal Spruce Zone of central British Columbia

Soil samples were taken before and 9 and 21 months after the operational broadcast burning of logging slash in two clear-cuts in the Sub-boreal Spruce Zone of central British Columbia. Average slash consumption on the two clear-cuts was estimated from line intersect samples at 20 and 24 t/ha and forest floor depth was reduced by 28 and 36%. Nine months after burning, soil N had decreased by 376 kg/ha (18% of preburn levels) while available P had increased by 37-157 kg/ha. Burning resulted in substantial increases in forest floor base saturation, pH, exchangeable Ca and Mg, and available P. Changes within the 0-15 and 15-30 cm mineral soil layers were variable and in general less pronounced. Significant positive correlations were observed between the consumption of large fuels and postburn changes in forest floor pH and exchangeable Ca and Mg. Changes in forest floor N were negatively correlated with amounts of fine slash consumed. A strongly negative correlation was observed between forest floor depth of burn and changes in forest floor exchangeable K concentrations.