Elevated tree mortality and reduced recruitment of new trees linked to drought and fires has been reported across a range of forests over the last few decades. Forests that resprout new foliage epicormically from buds beneath the bark are considered highly resilient to disturbance, but are potentially at risk of elevated mortality, demographic shifts and changes to species composition due to synergistic effects of drought and fire. Despite this, the effects of drought-fire interactions on such forests remain largely unknown. We assessed the effects of drought severity and fire frequency on juvenile mortality, post-fire seedling recruitment and replacement of juvenile trees (balance of recruitment minus mortality) following fire. We compared dry ridgetops and wet gullies (i.e. two forest types that inhabit different topographic positions in the landscape) across a temperate forest in southern Australia. Both forest types experienced higher rates of fire-induced juvenile mortality in are
Aim: To estimate loss of above-ground carbon (AGC) and conversion of live carbon to dead carbon following understorey and canopy fire. Location: South-eastern Australia. Time period: 2019–2020. Major taxa studied: Four widespread resprouting eucalypt forests. Methods: Above-ground carbon was measured in 15 plots in each of four forest types one-year post-fire. We also assessed topkill, that is, trees subject to canopy loss that failed to resprout epicormically. Results: While canopy fire was associated with greater declines in AGC than understorey fire, this was only statistically significant for only one forest type, where AGC declined from 154 to 85 Mg C ha−1 following canopy fire. Significant post-fire increases in dead AGC were observed in one forest type, where dead carbon increased from 22 to 60% after canopy fire. Topkill of trees following canopy fire (48–78% of stems) was higher than topkill after understorey fire (36–53% of stems) and in unburnt forest (12–55%). Top
Increases in tree mortality linked to drought and fires have been reported across a range of forests globally over the last few decades. Forests that resprout epicormically/aerially should be the most resistant and resilient to changes in fire regime, yet they may be at risk of increased mortality, demographic shifts and changes to species composition due to the compounding effects of drought and fire. Despite this, the synergistic effects of drought and fire frequency on resprouters has received less attention than for obligate seeder tree species. Our study examined the effects of drought severity and fire frequency on the fire resistance of eucalypts (i.e., including Eucalyptus, Angophora and Corymbia) that can resprout epicormically. Following large-scale wildfires and drought in 2013, we conducted field surveys of temperate eucalypt forests in the Sydney Basin Bioregion, focusing on two major Eucalyptus forest assemblages: dry ridgetops and wet gullies. We measured tree size, prev