Year

2024

Degree Name

Doctor of Philosophy

Department

School of Earth, Atmospheric and Life Sciences

Abstract

Changes in climate and fire regimes, modified by topography, may lead to eucalypts evolving protective bark traits, reducing their likelihood of becoming fire-scarred. This may in turn influence eucalypt mortality rates and distribution patterns. For my thesis, I aimed to provide an insight into how climate, fire and topography may be related to current eucalypt species protective bark traits and fire scarring to infer how eucalypt species may evolve over time and be distributed in the future. I conducted field and laboratory studies in dry sclerophyll forests and a study on dry and wet sclerophyll forests using primary and secondary data, all in south-eastern Australia. I investigated the effects of temperature, aridity, solar radiation, rainfall variability and fire severity on eucalypt species bark thickness and bark density and the effects of fire frequency on their proportions of fire scars. I also investigated differences in relative bark thickness, bark density and proportions of fire scars between eucalypt species positioned on ridges and in gullies. I then predicted the spatial distributions of bark thickness, bark density and fire scarring. The results were sometimes complex and inconclusive. Smooth barks had strong predicted increases in bark thickness with increases in mean annual temperature and strong predicted decreases in bark density with increases in mean annual radiation. Rough barks had strong predicted decreases in bark density with increases in mean annual temperature and annual rainfall variability. Stringy barks had strong predicted decreases in bark density with increases in mean annual temperature, mean annual radiation and annual rainfall variability. Rough barks were predicted to have thinner bark with increases in fire severity and smooth barks were predicted to have thicker bark. Smooth and stringy barks had predicted increases in proportions of fire scars with increases in fire frequency. I concluded that stringy barks may be most well- protected against climate change, but rough barks may be most resilient to changes in fire regimes. There was a greater probability of trees on ridges with a higher relative bark thickness, bark density and proportion of fire scars than trees in gullies. I found that rough barks were predicted to have higher bark thicknesses and lower bark densities in regions with higher mean annual precipitations. Smooth barks were predicted to have higher bark thicknesses and higher bark densities in regions with lower mean annual precipitations. These findings can be used to identify regions of vulnerability for different eucalypt species based on their levels of resistance to changes in climate and fire regimes.

FoR codes (2008)

050101 Ecological Impacts of Climate Change, 060207 Population Ecology, 060208 Terrestrial Ecology, 060705 Plant Physiology

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.