Fire effects on belowground sustainability: a review and synthesis

The overall effects of fire on ecosystems are complex, ranging from the red uction or elimination of aboveground biomass to impacts on belowground phys ical, chemical and microbial mediated processes. Since a key component of o verall ecosystem sustainability occurs belowground, recovery is tied to the soil's physical, chemical, and biological functions and processes. Dependi ng on several fire severity measures, changes in belowground components can be either beneficial or deleterious to the entire ecosystem. Low-impact bu rning can promote a herbaoeous flora, increase plant available nutrients, a nd thin overcrowded forests, all of which can foster healthy systems. Sever e fires can often cause changes in successional rates, alter above- and bel owground species composition, generate volatilization of nutrients and ash entrainment in smoke columns, produce rapid or decreased mineralization rat es, alter C : N ratios, and result in subsequent nutrient losses through ac celerated erosion, leaching or denitrification. In addition, changes in soi l hydrologic functioning, degradation of soil physical properties, decrease s in micro- and macrofauna, and alterations in microbial populations and as sociated processes can occur. The direct effect of fire on belowground syst ems is a result of the burning severity, which integrates aboveground fuel loading (live and dead), soil moisture and subsequent soil temperatures, an d duration of the burn. The time for recovery of belowground systems will n ot only depend on the burning intensity and its effect on key ecosystem pro cesses and components, but also on the previous land-use practices. Thus, t he impacts of fire on belowground systems can be highly variable and may no t be predictable. Our paper is a general review of the effects of fire on b elowground systems with emphasis placed on the changes in physical. biogeoc hemical and biological properties of soils and the resulting consequences t hese changes have for ecosystem sustainability. Published by Elsevier Scien ce B.V. All rights reserved.