The influence of wildfire on aqueous-extractable soil solutes in forested and wet meadow ecosystems along the eastern front of the Sierra-Nevada range, California

Information is lacking regarding the influence of pre-fire microsite conditions on post-wildfire soil chemical properties. Following a 1994 wildfire along the eastern front of the Sierra Nevada range, California, high performance ion exchange chromatography was used to quantify anions and cations in aqueous soil extracts by plant microsite (Pinus jeffreyi subcanopy, Calocedrus decurrens subcanopy, Carer microptera meadow, Salix scouleriana subcanopy), by depth (ash or litter, mineral soil horizon 0-5 cm), and by treatment (unburned, burned). As compared to the unburned treatment, post-wildfire ash and surface mineral horizons had significantly (P less than or equal to 0.05) higher concentrations of sodium, magnesium, formate, and chloride. Plant microsite interacted significantly with treatment for ammonium; all plant microsites had significantly higher ammonium in burned treatments and burned S. scouleriana and C. microptera microsites had significantly more ammonium than the C. decurrens or P. jeffreyi microsites. For pH and acetate there was a significant treatment x depth interaction in which concentrations were highest in burned ash layers. For sulfate, ortho-phosphate, and calcium, there was a significant plant microsite x treatment x depth interaction. In general, post-wildfire ash and soil mineral layers had significantly more sulfate and calcium than the unburned controls; ash layers contained significantly less ortho-phosphate than unburned litter layers. There was a significant treatment x depth interaction for magnesium, chloride, formate, acetate, potassium, and nitrate. Initial post-wildfire levels of short-chained aliphatic carboxylic acids were very high, especially in ash layers, and did not decline to preburn values by the following summer.