Date of Award

2009

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

School

School of Natural Sciences

Faculty

Faculty of Computing, Health and Science

First Advisor

Dr Eddie van Etten

Second Advisor

Will Stock

Abstract

Within the Mediterranean shrublands, fires are particularly intensive and widespread. In the Transitional Rainfall Zone in Western Australia, these large fires bum in areas with high conservation value, and present risks to human lives and infrastructure on properties in the region. The concern for the effect fires have on anthropocentric and ecological values in these shrublands makes it a priority in management to reduce the risks. Of the environmental and biotic factors that influence a fire, fuel is one of the most significant as it has the capacity to determine fire prope1iies such as the intensity, extent, bum pattern within the fire, and frequency. While fuel load is the most commonly assessed parameter, there are other fuel characteristics that also contribute to the behaviour and impacts of a fire, but don't receive as much attention. Fuel arrangement (plant density throughout the vertical profile), composition (live and dead, fine and coarse etc), continuity (horizontal distribution) and height are also important factors to consider in assessment of fuel dynamics. Knowledge on fuel dynamics provides the foundations for inferring return time of subsequent fires and the likely behaviour of these fires. For land managers, fuel characteristics may then be maintained or changed (e.g. through prescribed burning) to create a fire regime that satisfies management objectives. The purpose of this study was to gain an understanding of current fuel dynamics in shrublands of the Transitional Rainfall Zone, through assessment of fuel loading at the surface and above the ground, and assessing spatial arrangement of fuel. It was found that these shrub lands had heterogeneous fuel characteristics at small spatial scales, which is typical for this type of system. Heterogeneity was more likely explained by site factors such as underlying soil differences and climate, rather than as a result of the fire itself. Senescence was a dominant feature of the system in long unburnt sites, and contributed to creation of large interpatch spaces, high amounts of suspended dead material, and litter at the surface. Recently burnt sites had very small portions of dead material, large interpatch spaces, and litter was absent until around 14-18 years since last fire. Sites at 24-45 years since last fire had the greatest patch coverage and continuity in the horizontal and vertical array, and had larger quantities of fuel compared to all other ages. This shrubland system had slightly higher quantities of fuel than the accepted hazardous level, though it was still comparable to other similar shrubland systems in Australia and throughout the world. Patch coverage and continuity was also slightly higher than other systems, though took longer to reach this level. Equilibrium was eventually reached when sites were ve1y old, at about 80 years since last fire. From the time shrublands in this system reach about 14 years, fuel characteristics are typical of those required to foster intensive, wide spread fires that are prevalent in this system. For management, this study has shed light on the nature of fires to be expected in this system.

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