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Fire regimes and woody biomass dynamics in Australian savannas

Murphy, Brett P., Lehmann, Caroline E. R., Russell-Smith, Jeremy and Lawes, Michael J. (2014). Fire regimes and woody biomass dynamics in Australian savannas. Journal of Biogeography,41(1):133-144.

Document type: Journal Article
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IRMA ID 82057923xPUB566
Title Fire regimes and woody biomass dynamics in Australian savannas
Author Murphy, Brett P.
Lehmann, Caroline E. R.
Russell-Smith, Jeremy
Lawes, Michael J.
Journal Name Journal of Biogeography
Publication Date 2014
Volume Number 41
Issue Number 1
ISSN 0305-0270   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84890312873
Start Page 133
End Page 144
Total Pages 12
Place of Publication United Kingdom
Publisher Wiley-Blackwell Publishing Ltd.
HERDC Category C1 - Journal Article (DIISR)
Abstract Aim
Many tropical savannas are undergoing a trend of increasing woody biomass, or ‘woody thickening’. Management to reduce fire frequency and intensity in savannas could substantially increase the amount of carbon stored in woody biomass. We addressed two questions: (1) are northern Australian savannas thickening; and (2) to what extent, and by what demographic processes, does fire affect woody biomass accumulation?


Three large national parks, covering 24,000 km2, in monsoonal northern Australia.


We examined changes in woody biomass carbon stocks – inferred from tree basal area and the density of woody understorey plants – over a 10-year period in 136 savanna monitoring plots. We statistically assessed these changes in relation to fire frequency and severity. We used a meta-analysis to identify general trends in woody cover in Australian savannas over the last half-century.


Woody biomass carbon stocks were relatively stable across the three national parks, but rates of change were statistically indistinguishable from earlier findings of a weak thickening trend. Change was negatively correlated with fire frequency, particularly the frequency of severe fires. High frequencies of severe fires decreased rates of accumulation of biomass by existing trees (through reductions in tree growth and death of individual stems), rather than whole-tree mortality and suppression of recruitment. However, across northern Australia, our meta-analysis identified a general, albeit weak, trend of woody thickening.

Main conclusions

The drivers of northern Australia's weak thickening trend are uncertain, but likely candidates include increasing atmospheric CO2 concentration and water availability, and pastoral intensification. We demonstrate that changes to fire management have the potential to either increase or decrease rates of woody thickening relative to any underlying trend. Understanding how savanna fires affect woody biomass, and how fire effects are mediated by climate and CO2, are essential research priorities to predict the fate of savannas.
Keywords C4 grasses
carbon storage
CO 2
fire management
fire regimes
global change
northern Australia
tree demography
tropical savanna
woody thickening
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Created: Wed, 19 Aug 2015, 12:03:29 CST