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

Field and laboratory research was conducted to measure changes in extr actable anions following wildfire in sagebrush (Artemisia tridentata N utt.)-grass communities. Two sites were studied along the eastern Sier ra Nevada front in northeastern California on coarse-textured Haploxer olls and Haplargids formed from granitic parent materials. Soils were extracted with 0.15% KCl and analyzed with high-performance anion exch ange chromatography. Compared with unburned soils, significant (P less -than-or-equal-to 0.05) decreases in NO3- and orthophosphate, and sign ificant increases in SO42-, acetate, formate, oxalate, and glycolate o ccurred immediately after wildfire in the surface 5 cm of under-shrub soil. Concentrations of organic acids in burned undershrub soils incre ased significantly (P less-than-or-equal-to 0.05) in the weeks followi ng a wildfire. In shrub interspaces, largely occupied by cheatgrass (B romus tectorum L.), concentrations of anions were similar in unburned and post-wildfire soils. Laboratory heating of under-shrub soil indica ted that maximum amounts of KCl-extractable organic anions are produce d at temperatures between 150 and 350-degrees-C, and that the length o f time (up to 30 min) the soil was exposed to a given temperature cons iderably affected these amounts. Elevated concentrations of organic ac ids may influence seed germination, plant establishment, and mineral n utrition.