Winter Hazard Reduction Burning Reduces the Fuel Load in Themeda and Phalaris during Summer

This is a paper presented at the 2013 Bushfire CRC Research Forum.

Hazard-reduction burning is an important component of the bushfire mitigation program in the Australian Capital Territory (ACT). Burning is particularly important in grass fuels at locations that are unsuitable for slashing/mowing or grazing. Ideally grass fuels are burnt in spring however this work is constrained by weather, resource availability and ecological considerations. It would therefore be helpful if the burning season could begin on sunny winter days when grass fuels are well cured.

Previous work conducted during a high rainfall year found that winter burning reduced the fuel load and increased fuel moisture content in treated Phalaris fuels compared to untreated fuels. However treated fuels did not comply with ACT fuel management standards because by summer the grass was too high. In this study we expand on that work by:

1. testing across a broader geographic area;
2. testing under different rainfall conditions; and
3. including warm-season Themeda-dominated native grasses in the study.

We conducted a Before-After-Control-Impact study in a Phalaris-dominated site on the Canberra urban-rural interface and in one large native grass reserve within the Canberra urban area. Fuel load, grass cover and grass height were assessed before burning. Hazard reduction burns were completed in late winter (Phalaris) and early spring (Themeda) leaving control sectors unburnt for later comparison. All plots were re-measured in February 2013. The fuel load in treated Phalaris and Themeda grassland was lower than in the untreated grassland in summer following fire. In addition, the treated plots were within ACT fuel management standards. Our results suggest that winter burning has good potential as a grass fuel management tool in the ACT.