Abstract
Fire may remove or create dead wood aboveground, but it is less clear how high severity burning of soils affects belowground microbial communities and soil processes, and for how long. In this study, we inves- tigated soil fungal and bacterial communities and biogeochemical responses of severely burned ‘‘red” soil and less severely burned ‘‘black” soil from a burned forest on the eastern slope of the Cascade Range in Oregon. Specifically, we examined the effects of burn severity on soil nutrients and microbial communi- ties for 1–4 years after wildfire. Soil nutrients were significantly reduced in red soils. Soil fungi and bac- teria, assessed with molecular methods, steadily colonized both burn severities and soil biodiversity increased throughout the study showing that microbial communities seem to have the capacity to quickly adjust to extreme disturbances. Although richness did not vary by soil type, the fungal and bac- terial community compositions varied with burn severity. This difference was greatest in the early time points following the fire and decreased with time. However, nutrient-limited conditions of red soils were detected for four years after the wildfire and raise concern about soil productivity at these sites.