Woody encroachment, fire severity and fire history as compositional determinants of soil bacterial and fungal communities in a tallgrass prairie system

Fire changes abiotic and biotic attributes in terrestrial ecosystems. Short fire intervals maintain grasslands and communities adapted to frequent, low-severity fires. Shrub encroachment that follows longer fire intervals accumulates fuel and can increase fire severity. The patchily distributed biomass creates mosaics of different fire severities in the landscape. Afforded by a scheduled burn of a watershed protected from fires for 27 years, we investigated the effects of woody encroachment and fire severity on soil-inhabiting bacteria and fungi. High severity fire in the fire-protected watershed led to a novel soil system state distinct from non-encroached and encroached soil systems. Low severity fires also altered system attributes but to much lesser degree.