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Background and aims: Fires can alter the elemental stoichiometry of ecosystems, reflecting altered patterns of biogeochemical cycling in the post-fire environment. However, elements other than carbon (C), nitrogen (N), and phosphorus (P) have rarely been studied in this context. Thus, we aimed to expand the understanding of fire's stoichiometric and biogeochemical effects to encompass a broader suite of biogenic elements. Methods: We compared the stoichiometric ratios of C, N, P, potassium (K), sodium (Na), magnesium (Mg), and sulfur (S) in soil, plant litter, and beetles (Thalycrodes pulchrum) between forest plots that have been burned biennially at low intensity since 1972 and plots that have remained unburned. Results: Multi-element stoichiometry differed strongly between the fire regimes. Low intensity biennial burning was associated with depletion of C, N, and S relative to P, K, and to a small extent Mg and Na, in soil and litter. The stoichiometry of T. pulchrum biomass was not significantly affected by fire regime, but fire regime-associated variation in the stoichiometry of T. pulchrum biomass was positively correlated with the fire-induced stoichiometric shifts in soil. Conclusions: The effects of low intensity prescribed fire on ecological stoichiometry extend to Na, K, Mg, and S in ways consistent with the respective potentials of these elements to volatilize during fire or accumulate in the absence of fire. These effects vary among ecosystem components in a manner that reveals the importance of biological processes and constraints as factors that determine the nature, magnitude, and potential consequences of the stoichiometric signatures of fire regimes. We conclude that long-term changes in fire regime can disrupt or even decouple the biogeochemical cycles of numerous biogenic elements in the soil–plant system. [ABSTRACT FROM AUTHOR]

Abstract: The biogeochemical and stoichiometric signature of vegetation fire may influence post‐fire ecosystem characteristics and the evolution of plant ‘fire traits’. Phosphorus (P), a potentially limiting nutrient in many fire‐prone environments, might be particularly important in this context; however, the effects of fire on P cycling often vary widely. We conducted a global‐scale meta‐analysis using data from 174 soil studies and 39 litter studies, and found that fire led to significantly higher concentrations of soil mineral P as well as significantly lower soil and litter carbon:P and nitrogen:P ratios. These results demonstrate that fire has a P‐rich signature in the soil–plant system that varies with vegetation type. Further, they suggest that burning can ease P limitation and decouple the biogeochemical cycling of P, carbon and nitrogen. These effects resemble a transient reversion to an earlier stage of ecosystem development, and likely underpin at least some of fire's impacts on ecosystems and organisms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background and aims: Changes to soil nutrient concentrations following vegetation fire may affect biogeochemical cycling and foliar stoichiometry. Phosphorus (P)-limited plant communities are widespread and may be particularly sensitive to fire, but have received relatively little research attention in this context. Methods: We measured soil nutrient concentrations, foliar carbon (C), nitrogen (N) and P stoichiometry of understorey plants in a recently, frequently burned eucalyptus forest area in south-east Queensland, Australia, and compared these properties to an adjacent unburned area. Results: Surface soils in the area subjected to relatively recent, frequent prescribed burning had higher P concentrations than those in the adjacent unburned area, although this did not include the 'available' forms of P. All plant species had high foliar N:P ratios, regardless of fire history, consistent with widespread P-limitation. Some species had lower foliar N:P ratios in the burned area, indicating interspecific variation in nutrient requirements and burning responses. The nutrient resorption proficiencies of a grasstree ( Xanthorrhoea johnsonii Lee) were lower in the burned area, suggesting that the nutrient cycling of this species was made less conservative by burning. Conclusions: The stoichiometric patterns observed in the responses of plants to prescribed burning highlight the significance of fire in this P-impoverished plant community, and suggest the potential value of stoichiometric approaches in fire ecology. [ABSTRACT FROM AUTHOR]

Fire is a major driver of ecosystem change and can disproportionately affect the cycling of different nutrients. Thus, a stoichiometric approach to investigate the relationships between nutrient availability and microbial resource use during decomposition is likely to provide insight into the effects of fire on ecosystem functioning. We conducted a field litter bag experiment to investigate the long-term impact of repeated fire on the stoichiometry of leaf litter C, N and P pools, and nutrient-acquiring enzyme activities during decomposition in a wet sclerophyll eucalypt forest in Queensland, Australia. Fire frequency treatments have been maintained since 1972, including burning every 2 years (2yrB), burning every 4 years (4yrB) and no burning (NB). C : N ratios in freshly fallen litter were 29-42% higher and C : P ratios were 6-25% lower for 2yrB than NB during decomposition, with correspondingly lower 2yrB N : P ratios (27-32) than for NB (34-49). Trends in litter soluble and microbial N : P ratios were similar to the overall litter N : P ratios across fire treatments. Consistent with these, the ratio of activities for N-acquiring to P-acquiring enzymes in litter was higher for 2yrB than NB, whereas 4yrB was generally intermediate between 2yrB and NB. Decomposition rates of freshly fallen litter were significantly lower for 2yrB (72 ± 2% mass remaining at the end of experiment) than for 4yrB (59 ± 3%) and NB (62 ± 3%), a difference that may be related to effects of N limitation, lower moisture content, and/or litter C quality. Results for older mixed-age litter were similar to those for freshly fallen litter although treatment differences were less pronounced. Overall, these findings show that frequent fire (2yrB) decoupled N and P cycling, as manifested in litter C : N : P stoichiometry and in microbial biomass N : P ratio and enzymatic activities. Furthermore, these data indicate that fire induced a transient shift to N-limited ecosystem conditions during the postfire recovery phase. [ABSTRACT FROM AUTHOR]

Decadal‐scale increases in fire frequency have the potential to deplete ecosystems of essential nutrients and consequently impede nutrient‐limited biological processes via stoichiometric imbalance. Decomposition, a fundamental ecosystem function and strong driver of future fire occurrence, is highly sensitive to nutrient availability and is, therefore, particularly important in this context. Here we show that 40 yr of quadrennial (4yB) and biennial (2yB) prescribed burning result in severely P‐ and N‐depleted litter stoichiometry, respectively, relative to fire exclusion. These effects exacerbated the nutrient limitation of microbial activities, constraining litter decomposition by 42.1% (4yB) and 23.6% (2yB) relative to unburned areas. However, invertebrate‐driven decomposition largely compensated for the diminished capacity of micro‐organisms under 4yB, suggesting that invertebrates could have an important stabilizing influence in fire‐affected ecosystems. This effect was strongly positively coupled with the strength of microbial P‐limitation and was not obviously or directly driven by fire regime‐induced changes in invertebrate community assemblage. Together, our results reveal that high‐frequency fire regimes promote nutrient‐poor, carbon‐rich ecosystem stoichiometry and, in doing so, disrupt ecosystem processes and modify the relative functionality of micro‐organisms and invertebrates. [ABSTRACT FROM AUTHOR]