EXTRACTABLE ANIONS IN SOILS FOLLOWING WILDFIRE IN A SAGEBRUSH-GRASS COMMUNITY

Field and laboratory research was conducted to measure changes in extractable anions following wildfire in sagebrush (Artemisia tridentata Nutt.)-grass communities. Two sites were studied along the eastern Sierra Nevada front in northeastern California on coarse-textured Haploxerolls and Haplargids formed from granitic parent materials. Soils were extracted with 0.15% KCl and analyzed with high-performance anion exchange chromatography. Compared with unburned soils, significant (P less-than-or-equal-to 0.05) decreases in NO3- and orthophosphate, and significant increases in SO42-, acetate, formate, oxalate, and glycolate occurred immediately after wildfire in the surface 5 cm of under-shrub soil. Concentrations of organic acids in burned undershrub soils increased significantly (P less-than-or-equal-to 0.05) in the weeks following a wildfire. In shrub interspaces, largely occupied by cheatgrass (Bromus tectorum L.), concentrations of anions were similar in unburned and post-wildfire soils. Laboratory heating of under-shrub soil indicated that maximum amounts of KCl-extractable organic anions are produced at temperatures between 150 and 350-degrees-C, and that the length of time (up to 30 min) the soil was exposed to a given temperature considerably affected these amounts. Elevated concentrations of organic acids may influence seed germination, plant establishment, and mineral nutrition.