Wildfire Effects on Nutrient Distribution and Leaching in a Coniferous Ecosystem

Distribution of nutrients after the Entiat fire in north central Washington was examined. This intense fire produced an average ash weight on the soil surface of 2900 kg/ha. The ash layer contained 23 kg/ha N, 314 kg/ha Ca, 54 kg/ha Mg, 70 kg/ha K, and 22 kg/ha Na. Nutrient losses during the fire as a result of combined volatilization and ash convection were 855 kg/ha N, 75 kg/ha Ca, 33 kg/ha Mg, 282 kg/ha K, and 698 kg/ha Na. Nitrogen loss apparently was proportional to fuel dry weight loss.Leaching of the ash layer in the 1st year after burning transferred a trace of N, 149 kg/ha Ca, 50 kg/ha Mg, 92 kg/ha K, and 33 kg/ha Na from the ash layer to the soil. Of the amounts leached from the ash, 134 kg/ha Ca, 48 kg/ha Mg, and 84 kg/ha K were retained in the 0-to 19-cm layer of soil. In the same interval a net loss of 29 kg/ha Na was observed from the 0-to 19-cm layer of soil.Cation leaching from ash layers was primarily related to water percolation through the ash. Equations are given that describe leaching of Ca, Mg, K, and Na from an average ash layer of the Entiat fire.