SOIL MICROBIAL-POPULATIONS AFTER WILDFIRE

Population fluctuations were increased by burning, which also modified the incubation patterns and the densities of several microbial groups , although without changing the order of their population sizes. In th e short term, fire produced a sharp increase in microbes but affected the groups studied differently. Aerobic heterotrophic bacteria, includ ing the acidophilic and sporulating ones, were stimulated by fire whil e cyanobacteria, algae and fungi (propagules as well as hyphae length) were clearly depressed. In the long term, the positive effect of fire on bacteria was nullified except on the sporulating ones; fungal prop agules, but not mycelium, reached the unburned soil values, cyanobacte ria and algae also increased. Soil incubation both improved the benefi cial and diminished the negative fire effect on the microbiota.