Fire mosaics in south-west Australian forest landscapes

Abstract

In fire-prone environments, prescribed burning is important for achieving many public land management objectives including protecting communities and the environment from damaging bushfires. There is evidence that in some biomes, reducing the size of burnt patches and creating a fine-scale mosaic of vegetation at different times since last fire (seral stages) may benefit biodiversity. However, planning and implementing an ongoing burning program to achieve this is problematic. To advance an understanding of the factors affecting burn patch size and seral diversity metrics, a novel experimental management trial that aimed to create and quantify a fine-scale fire mosaic was implemented in a south-west Australian forest landscape. The 10-year trial demonstrated that the fire mosaic characteristics, including diversity of seral stages, burnt patch size, patch distribution and patch connectedness, can be managed to a large extent by ignition frequency, which affects landscape fuel flammability, and the timing of the introduction of fire with respect to weather conditions. In this trial, the frequent introduction of fire under low to moderate Forest Fire Danger Indices resulted in a landscape comprising a quantifiably higher diversity of seral stages and smaller burnt patches than adjacent areas treated by fuel reduction prescribed burns and by a high intensity bushfire.

Fire shapes fungal guild diversity and composition through direct and indirect pathways

“…In contrast to our hypotheses, total fungal richness declined with time‐since‐fire because elevated dead cover increased with increasing time‐since‐fire and total fungal richness declined with increasing elevated cover. The response of increasing elevated dead cover to time‐since‐fire aligns with other studies, as vegetation complexity increases along the post‐fire succession axis (Burrows et al, 2021; Gosper et al, 2012). Conversely, lower fungal richness under elevated dead cover could reflect competition between species as substrates build up (Bödeker et al, 2016; Künzler, 2018), although diverse and dense covers of substrates can support diverse fungal communities (Yang, Limpens, et al, 2021; Yang, Tedersoo, et al, 2021).…”

“…The build-up of both elevated dead (Burrows et al, 2021;Gosper et al, 2012) and coarse woody debris (Haslem et al, 2010) as vegetation complexity increases along the post-fire successional axis aligns with other studies. However, decreases in coarse woody debris under frequent fires contrast our assumption.…”

“…In contrast to our hypotheses, total fungal richness declined with time-since-fire because elevated dead cover increased with increasing time-since-fire and total fungal richness declined with increasing elevated cover. The response of increasing elevated dead cover to time-since-fire aligns with other studies, as vegetation complexity increases along the post-fire succession axis (Burrows et al, 2021;Gosper et al, 2012). Conversely, lower fungal richness under elevated dead cover could reflect competition between species as substrates build up (Bödeker et al, 2016;Künzler, 2018), Note: F: variance between groups, R 2 : amount of dissimilarity between pair, p-value: significance (p ≤ .05 deemed significant), recently burnt: 0-2.5 years post-fire, mid-succession: 2.5-8.5 years post-fire, late-succession: 8.5-33.5 years post-fire, long unburnt: 33.5+ years post-fire, low fire frequency: burnt ≤2 times over 29-year period, high fire frequency: burnt 3-5 times over 29-year period.…”

“…For example, the fungi in our study decompose dung, nectar, pollen, litter, soil and wood, which can be entirely consumed or altered by fires (Haslem et al, 2010). The build‐up of both elevated dead (Burrows et al, 2021; Gosper et al, 2012) and coarse woody debris (Haslem et al, 2010) as vegetation complexity increases along the post‐fire successional axis aligns with other studies. However, decreases in coarse woody debris under frequent fires contrast our assumption.…”

Evidence for lack of a fuel effect on forest and shrubland fire rates of spread under elevated fire danger conditions: implications for modelling and management

“…Less fuel available to burn potentially lowers the impacts on soils, vegetation and associated ecosystem services (e.g. carbon storage), thereby modulating post-fire response, and thus minimising post-fire restoration needs (Burrows et al 2021).…”