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 would be 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 is well cured.

Previous work conducted during a high rainfall year found that winter burning reduced the fuel load and increased the fuel moisture content in treated Phalaris fuels compared to untreated fuels. However the 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 four Phalaris-dominated paddocks on the Canberra urban-rural interface and in one large native grass reserve within the Canberra urban area. Fuel load, fuel moisture content, grass cover, grass height and grass curing were assessed at all plots before burning. Hazard reduction burns were completed in late winter (Phalaris) and early spring (Themeda) leaving control sectors unburnt for later comparison. The grass was monitored in October and December 2012 and re-measured in February 2013.

In February 2013, the fuel load in treated Phalaris and Themeda grassland was significantly lower than in the untreated grassland (Phalaris = 3.0t/ha vs 13t/ha; Themeda = 2.4t/ha vs 11.3t/ha). In addition, the treated grass in both fuel types was within ACT fuel management standards.  It therefore appears that winter burning has good potential as a grass fuel management tool in the ACT.