Hydrologic Response and Nutrient Concentrations Following Spring Burns in an Oak-hickory Forest1
- M. Dean Knighton2
Annual spring burns were applied for 1 to 3 years on a 25 to 50% slope in an oak-hickory forest (Quercus—Carya) in southwestern Wisconsin. Overland flow and sedimentation did not increase, although no severe storms occurred during the study.
Fires of light to moderate intensities, consumed most of the fresh litter and sometimes all of the fermentation layer. Mean weight of litter plus fermentation layers were significantly reduced (α = 0.05) from 15,800 kg/ha to 10,100 kg/ha by three annual burns. Bulk density, total pore volume, organic carbon content, and water permeability of the mineral soil were unaltered. Stems <5 cm in diameter at breast height were killed, but shrubs sprouted vigorously and herbaceous vegetation was not altered.
Mean concentrations of both anions [PO4-P and (NO3 + NO2)-N)] and cations (Ca, Mg, K) in the soil leachate collected at 15-cm depth appeared to increase after burning although the differences were small and highly variable. Significant changes (α = 0.05) in the concentration of both anions were measured through the growing season. Concentrations of (NO3 + NO2)-N peaked 6 weeks after the mid-April fires, which reflects increased nitrification following burning. Sodium concentrations were not affected by burning. Although it was increased by burning nutrient loss to deep leaching appeared to be approximately equivalent to, or less than, estimated annual input from precipation.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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