Fire alters soil labile stoichiometry and litter nutrients in Australian eucalypt forests

Abstract

Ecological stoichiometry may be used to investigate the impacts of fire regime, as fire regime can influence the cycling and balance of elements within forest ecosystems. We investigated the effects of fire history on soil and litter stoichiometry in four forest sites in Queensland, Australia. Soil and litter in recently burned areas were compared with those in areas with no recent fire. Effects of burning on concentrations and ratios of multiple pools of carbon (C), nitrogen (N) and phosphorus (P) in soil varied between sites, indicating that site and fire regime characteristics regulate these responses. Labile pools of soil C, N and P were more responsive to burning than total pools, and labile soil C : P and N : P ratios tended to be lower in recently burned areas, consistent with our expectations. These changes suggest that the disparate volatilisation temperatures of these elements influence post-fire soil stoichiometry, and that P cycling may be enhanced in some post-fire environments. Fire-induced changes to litter chemistry were not consistent with soil effects, although litter was generally nutrient-enriched in recently burned areas. Our results reveal the potential for fire to alter elemental balances and thus modify C and nutrient cycling in the plant–soil system.