Abstract
AbstractAimMany species are adapted to a particular fire regime and major deviations from that regime may lead to localized extinction. Here, we quantify immaturity risks to an obligate‐seeder forest tree using an objectively designed climate model ensemble and a probabilistic fire regime simulator to predict future fire regimes.LocationAlpine ash (Eucalyptus delegatensis) distribution, Victoria, south‐eastern Australia.MethodsWe used a fire regime model (FROST) with six climate projections from a climate model ensemble across 3.7 million hectares of native forest and non‐native vegetation to examine immaturity risks to obligate‐seeder forests dominated by alpine ash (Eucalyptus delegatensis), which has a primary juvenile period of approximately 20 years. Our models incorporated current and future projected climate including fuel feedbacks to simulate fire regimes over 100 years. We then used Random Forest modelling to evaluate which spatial characteristics of the landscape were associated with high immaturity risks to alpine ash forest patches.ResultsSignificant shifts to the fire regime were predicted under all six future climate projections. Increases in both wildfire extent (total area burnt, area burnt at high intensity) and frequency were predicted with an average increase of up to 110 hectares burnt annually by short‐interval fires (i.e., within the expected minimum time to reproductive maturity). The immaturity risk posed by short‐interval fires to alpine ash forest patches was well explained by Random Forest models and varied with both location and environmental variables.Main conclusionsAlpine ash forests are predicted to be burned at greater intensities and shorter intervals under future fire regimes. About 67% of the current alpine ash distribution was predicted to be at some level of immaturity risk over the 100‐year modelling period, with the greatest risks to those patches located on the periphery of the current distribution, closer to roads or surrounded by a drier landscape at lower elevations.
Highlights
| METHODSOur study focussed on the distribution of eucalypt forests dominated by alpine ash (Eucalyptus delegatensis) on public land in the state of Victoria, south-eastern Australia, which equates to approximately 283,000 hectares
We aimed to provide a stronger basis for identifying those alpine ash forests most at risk under future fire regimes so that they can be prioritized for active management
Our study focussed on the distribution of eucalypt forests dominated by alpine ash (Eucalyptus delegatensis) on public land in the state of Victoria, south-eastern Australia, which equates to approximately 283,000 hectares
Summary
Our study focussed on the distribution of eucalypt forests dominated by alpine ash (Eucalyptus delegatensis) on public land in the state of Victoria, south-eastern Australia, which equates to approximately 283,000 hectares. While there were localized differences in predicted changes to the number of short-interval fires among the six climate models, the majority indicated the potential for increased immaturity risk across the alpine ash distribution on the margins of the distribution (Figure 5). RF models explained 54 (CSIRO R2) to 69% (ECHAM R1) of the variation in simulated immaturity risk to alpine ash patches (20-year juvenile period) in the training set, and 13 (CSIRO R1) to 52% (CSIRO R3 and ECHAM R1) of variation in the test set (Table 2; Figure S10). Consistent responses of immaturity risk across models were indicated for mean aridity and the area of dry forest in the patch and 1km buffer (positive to asymptote), soil bulk density (positive), canopy top height (negative beyond 15 metres) and elevation (negative beyond 1,000 m; Figure 7)
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