Measuring a Fire. The Story of the January 2019 Fire Told from Measurements at the Warra Supersite, Tasmania

Tim Wardlaw

doi:10.3390/fire4020015

Abstract

Non-stand-replacing wildfires are the most common natural disturbance in the tall eucalypt forests of Tasmania, yet little is known about the conditions under which these fires burn and the effects they have on the forest. A dry lightning storm in January 2019 initiated the Riveaux Road fire. This fire burnt nearly 64,000 ha of land, including tall eucalypt forests at the Warra Supersite. At the Supersite, the passage of the fire was recorded by a suite of instruments measuring weather conditions and fluxes (carbon, water and energy), while a network of permanent plots measured vegetation change. Weather conditions in the lead-up and during the passage of the fire through the Supersite were mild—a moderate forest fire danger index. The passage of the fire through the Supersite caused a short peak in air temperature coinciding with a sharp rise in CO2 emissions. Fine fuels and ground vegetation were consumed but the low intensity fire only scorched the understorey trees, which subsequently died and left the Eucalyptus obliqua canopy largely intact. In the aftermath of the fire, there was prolific seedling regeneration, a sustained reduction in leaf area index, and the forest switched from being a carbon sink before the fire to becoming a carbon source during the first post-fire growing season.

Highlights

Under natural conditions, the tall eucalypt forests of south-eastern Australia depend on periodic burning to persist [1,2]
The Warra Supersite recorded weather conditions during the fire from the 15th January to the 28th January when the fire burnt through the site and power was lost
Between 20th December 2018 and 7th February 2019, the soil dryness index steadily increased and had reached 55 mm by the time the fires started on 15th January and peaked at 99 mm on 6th February—the day before significant rainfall

Summary

Introduction

The tall eucalypt forests of south-eastern Australia depend on periodic burning to persist [1,2] These forests are situated in one of the most fire-prone regions in the world [3] and accumulate biomass to levels that are among the highest globally [4,5,6,7]. This high biomass coupled with periodic severe fire weather conditions can result in catastrophic wildfire [8,9,10]. Characteristics of intense, stand-replacing wildfires in eucalypt forests of south-eastern Australia are well documented [9,15,16], but there are few reports documenting the characteristics of non-stand-replacing fires, their fire histories and post-fire regeneration have been documented [12,17]

Methods

Results

Conclusion