A laboratory study of postfire nutrient redistribution in subarctic spruce–lichen woodlands

Abstract

The redistribution of nutrients after fire was examined by igniting samples of spruce needles, birch leaves, and lichen and leaching the ash through a soil column, under laboratory conditions. Nitrogen was lost from the tissue samples at temperatures above 200 °C. Up to 40 kg/ha can be lost from the woodlands during a fire. Leaching of the plant tissue ignited at 500 °C for 2 min removed about a third of the cations, as well as 10% of the phosphorus, but very little ammonium or nitrate. The cations were adsorbed by the organic and subsoil horizons, so that losses from the soil column were small (10–15 kg/ha). Ninety percent of the phosphorus removed from the ash and the organic horizons was absorbed by the subsoil horizons. The leachates of the lichen ash were acid and low in nutrients, promoting nutrient removal from, or redistribution within, the soil column. The nutrient flush from subarctic woodland fires is small compared with the flush from other ecosystems.