Can precipitation influence landscape controls on wildfire severity? A case study within temperate eucalypt forests of south-eastern Australia

Abstract

Abstract. The environmental, economic and social impacts of wildfires depend on spatial patterns of fire severity. An understanding as to how drivers of fire severity vary across broad vegetation communities exists. However, examination of variation within communities in response to gradients of moisture has received little attention so far. This study examined whether relationships between environmental variables (i.e. fire weather, topography and fuel age) and fire severity were modified by increasing mean annual precipitation. Understorey fires were more likely to occur in young fuels (i.e. ,5 years since fire) in drier sites, although this effect diminished as precipitation increased. The probability of occurrence of understorey fires under non-extreme weather and on steep slopes was reduced in wetter areas. Relationships between crown fire and weather, topography and fuel age were largely unaltered by the precipitation gradient, with only a marginally significant interaction occurring between weather and mean annual precipitation. Greater fine fuel accumulation associated with increased precipitation presumably reduced fuel limitations imposed by environmental factors (i.e. fire weather, slope, fuel age), altering their relative control on the probability of understorey fire. The probability of crown fires is predominantly driven by fire weather and is consequently less sensitive to precipitation gradients. Consideration of precipitation gradients will be necessary when identifying controls of fire severity and devising effective fire management strategies.

Is there an inherent conflict in managing fire for people and conservation?

“…Fuel loads, topography and fire weather resulted in predicted flame lengths greater than 20 m in koala zones under all treatments. Similar high severity fires have been reported in nearby forests by Collins et al (2014). Overall, our results are consistent with other studies that show the placement of treatments nearest to assets provides the greatest reduction in risk (Safford et al 2009;Ager et al 2010;Penman et al 2014).…”

“…This result was due to the fact that the koala population area was larger than the fuel treatments within koala habitat. While treatment of larger areas can reduce the likelihood of a fire spreading, under more severe fire weather conditions the amount of fuels becomes less important than weather, as wildfires can still spread through areas with low fuel loads (Cary et al 2009;Bradstock et al 2010;Collins et al 2014). While the probability of fire is reduced for property and koalas, the impact from exposure to fire remains high for both koalas and property.…”

Impacts of Frequent Burning on Live Tree Carbon Biomass and Demography in Post-Harvest Regrowth Forest

“…Infrequent high severity fire is known to cause up to ~5% tree mortality in resprouting eucalypts, but such mortality may be halved in response to low-moderate intensity fires [54]. Weather is the dominant driver of fire severity, which may also be positively related to fuel age or time since last fire [52,55,56]. High severity fires also stimulate considerable tree recruitment from seed [54], which has the capacity to fill gaps created by mortality in the medium term.…”

“…Fire behaviour is not spatially homogeneous, with considerable variation in patchiness and intensity being observed within the perimeters of both prescribed burns and wildfires [52,55,56,59]. While prescribed fire may be applied at short rotations, the interval at which a point in the landscape burns may be much greater [59].…”

Improving Fire Behaviour Data Obtained from Wildfires

“…In small fires, agencies may record simple details such as ignition location [23][24][25][26], final fire perimeter and fire area [27]. For large fires that have substantial impacts, data may be extended to include fire severity [28][29][30][31], fire progression [32,33] and impact [34][35][36]. However, much of this information is collected and collated post event.…”