Biomass consumption by surface fires across Earth's most fire prone continent

Area of Science:

• Ecology
• Global Carbon Cycle
• Fire Ecology

Background:

• Landscape fire is a critical, yet understudied, element of the global carbon cycle.
• Accurate prediction of biomass consumption by fire is vital for understanding carbon dynamics and informing fire management strategies to mitigate greenhouse gas emissions and enhance ecosystem carbon storage.

Purpose of the Study:

• To estimate the impact of biomass combustion by surface fires on continental carbon budgets across Australia.
• To investigate the relationship between fire frequency, severity, and biomass consumption across diverse Australian landscapes.

Main Methods:

• Conducted a nationwide field survey at 113 locations, encompassing broad macroecological gradients (climate, productivity, fire regimes).
• Analyzed biomass consumption by surface fires and related it to annual carbon consumption and net primary production (NPP).

Main Results:

• A trade-off exists between fire frequency and severity: less frequent, more severe fires in southern Australia consumed more biomass per event, while frequent, less severe fires in northern savannas consumed less per event.
• Annual biomass consumption was substantially higher in tropical savannas (over 20 times southern Australia).
• Annual carbon consumption by fire averaged 11% of NPP nationally, with significant regional differences (6% in temperate south, 46% in tropical north).

Conclusions:

• Tropical savanna landscapes account for the majority of global biomass consumption by fire and are the priority for fire management aimed at reducing greenhouse gas emissions.
• In tropical savannas, grass biomass is a primary determinant of fire characteristics (frequency, intensity, completeness of combustion).
• Management actions increasing grass biomass in savannas may inadvertently increase greenhouse gas emissions from fires.