Inter- and intra-specific comparisons were made between several co-occurring populations of two 'Banksia' species growing in Eastern Australian dry sclerophyll open woodland that experiences a grass-fueled surface-fire regime. The two species differ in life-history from a short basal resprouter (B. 'Neoanglica') to a tall fire-survivor (B. 'integrifolia'). Growth (LMA = leaf mass per unit mass area), persistence (bark thickness) and recruitment (serotiny) traits were determined across independent gradients in soil fertility and fire frequency. Trait correlations for the two species showed distinct patterns, from each other and across environments, with the resprouter having higher LMA and infructescence retention but lower bark thickness. However, there were no consistent intraspecific patterns with variation in fire and soil nutrients. LMA only varied in B. 'integrifolia' with soil fertility, and fire frequency had no effect on either species. Relative bark thickness varied with plant size but not among sites. There was a trend of increasing pyriscence with fire in B. 'neoanglica' and with lower nutrients soils but not in B. 'integrifolia'. Clearly the two species respond differently to variability in nutrients and fire. Nevertheless, growth form appears to be the strongest determinant of both growth (LMA) and fire traits (thicker bark; pyriscence) in these co-existing 'Banksia' species.

Although bark thickness and fire-activity are correlated in many ecosystems worldwide, substantial data-gaps remain, especially for dryland biomes, preventing generalisation of this relationship at the global scale. We examined bark thickness trends in trees and shrubs across a large-scale fire-rainfall gradient from desert to dry savanna in northern Australia. Bark thickness increased with local fire activity but was unrelated to mean annual rainfall or the mean normalised difference vegetation index (surrogates of resource-productivity). In high-fire regions, thin-barked trees were restricted to localised low-fire patches. Thicker bark was associated with sites characterised by flammable 'Triodia' hummock grassland (spinifex). Within this flora, bark thickness reflected a trade-off in trait allocation to fire resistance versus fire resilience. For trees, thicker bark (fire resistance) was strongly associated with epicormic resprouters. In contrast, fire-resilient species that were either basal resprouters or reseeders had thinner bark. With increasing aridity there was a shift in dominance from epicormic resprouters to thinner-barked shrub and mallee species that either basally resprout or are killed by fire. Pairwise congeneric species comparisons showed a consistent relationship of thicker bark under high fire activity. This same pattern also emerged from a multi-species comparison within the dominant tree genus 'Eucalyptus'. Overall, for this system, species with thick bark at the sapling stage dominate where fire is frequent. Thus, we confirm that fire can be a major driver of plant traits in fire-prone drylands.

Water availability influences regional tree distributions in rainforests, often by affecting survival of seedlings. The occurrence of 'dry rainforest' species in subhumid climates has been attributed to the evolution of drought-resistant species from their mesic rainforest congeners. Many genera are found in both dry and mesic rainforest of Australia but the extent to which this is due to differential drought resistance has not been confirmed experimentally. We compared drought survival within three congeneric pairs of dry and mesic rainforest taxa in a glasshouse dry-down experiment. Soil type could also play a role, with dry rainforests mostly occurring on fine-textured soils such as loams, which have a high available water-holding capacity, compensating for lower rainfall. Hence, we grew plants in loam or sand soil. In all pairs, the dry rainforest taxon was better able to survive drought, providing support for the climate-induced evolution of a dry rainforest flora and further confirming that drought resistance of seedlings can shape tree species distributions at regional scales. Two of three pairs had higher seedling survival on basalt-derived loam soil, suggesting that such soils may aid seedling persistence during drought. Over evolutionary time, this may have resulted in the high fidelity of dry rainforest for these soils.

The effect of fire on natural resources is termed "fire severity" and is related to the energy output of the fire. Recently the term "burn severity" has been introduced to identify the impacts of fire on soil and plants when the fire has been extinguished. This study addresses the assessment of a large wildfire in Gibraltar Range National Park, Australia, through remote sensing of fire severity and explores the spatial relationships between, fire severity and biophysical factors. Burn severity indices were developed from Landsat TM satellite images using pre-fire and post-fire images. Reflectance values computed from Landsat Enhanced Thematic Mapper (ETM) images acquired before and after the fire were used to estimate the Normalised Burn Ratio (NBR), which incorporates the near and mid infrared bands. Spatial distribution of ANBR data were calibrated with field observations and threshold values of burn severity were used to classify fire severity into 5 severity classes per vegetation type. ANBR values were extracted from different representative fire severities and spatial relationships were developed between ANBR and vegetation type, fuel type, fire danger index, time since fire, fire frequency, slope and rockiness in order to account for variables influencing fire severity patterns. General linear models and tests of significance were used to ascertain whether the effects of individual factors were statistically significant. The various models tested showed that no single factor (weather, fuel or landscape) accounted for the burn severity pattern. Fire weather and vegetation type Were found to be the key factors in the models.