SPATIAL PATTERNS OF FIRE BEHAVIOUR IN RELATIONTO WEATHER, TERRAIN AND VEGETATION

摘要

Understanding fire behaviour in different weather conditions and across large, flammable landscapes is important for fire management. In this study, the influences of weather and major landscape variables on fire behaviour were examined following a large fire in the Blue Mountains, near Sydney. Patterns of fire behaviour were inferred from a fire severity map derived using remote sensing and field validation. Fire weather on the day of burning was determined for different parts of the landscape using bureau of meteorology data and fire spread maps compiled during the event. Relative proportions of the landscape burnt by different fire behaviour classes (particularly crown and understorey fires) were determined in a geographic information system. The influence of vegetation type, fuel age and terrain on fire behaviour during two contrasting weather conditions (extreme and moderate fire weather) was examined. The analysis showed that during extreme weather, fire behaviour was dominated by either a crown fire that consumed the canopy or a fire of an intensity that scorched the canopy leaves. In relatively moderate weather, crown fire was almost non-existent and the canopy remained intact over about half of the landscape. Fuel age (time since last fire) of between 1-4 years appeased to moderate fire behaviour relative to fuel ages of 5 to >20 years. Ridge tops and slopes of 15° or less appeared to suffer more crown fire than gullies and slopes of >15°. Surprisingly, aspect did not greatly influence fire behaviour despite strong, directional winds. An important ecological implication may be that fires that occur during severe weather lead to greater landscape homogeneity than fires that occur during more mild weather.