- Title:
-
Effects of Repeated Low-intensity Fire on Fuel Dynamics in a Mixed Eucalypt Foothill Forest in South-eastern Australia
- Date:
- December 2003
- Organisations
- DSE
- Authors:
- Kevin G. Tolhurst and Natalie Kelly
- Location:
- Victoria, VIC, Australia
Overview
Litter provides not only fuel for a fire, but also habitat for many terrestrial mammals, reptiles, birds and invertebrates. This study measured changes in litter on an annual and seasonal basis. Litterbed ages included in this study range from recently burnt to over 60 years old.This report addresses only the surface fine fuels in a mixed eucalypt foothill forest. It has not addressed elevated fuels, such as shrubs or the bark held on tree boles. Consideration of the impact of prescribed burning on potential fire behaviour should include consideration of the overall fuel complex.
Surface fine fuels in this forest type have an average steady-state level of 16 t ha-1, but seasonal variations may result in the fuel loads ranging from 8 t ha-1 to 24 t ha-1. Therefore, fuel accumulation models should only be used as a general, long-term, broadscale planning tool. To assess the impact of fuels on fire behaviour or hazard levels in any particular year or in any particular place, an on-site assessment must be made.
Following fire, surface litter reaccumulates quickly due to the reduced rates of litter decomposition. Surface fine fuels reaccumulate to 90% of the long-unburnt state within four years of either spring or autumn burning. The impact of low-intensity fire on surface fuels is therefore short-lived. However, studies elsewhere (e.g. Tolhurst et al. 1992; Tolhurst 1995; McCarthy & Tolhurst 2002) have shown that the effect of low-intensity fire on the overall fuel hazard levels may last for 15 years or more.
Consistently more surface fine fuel has been recorded in autumn than in spring. This difference amounts to between 1 and 2 t ha-1.
This study has demonstrated that some conclusions drawn from short-term studies or space-for-time studies can be misleading (space-for-time studies are those made at a single point in time at a number of different locations with different histories that are combined to represent the succession of changes over time at the one location). Trends in litter levels occurred on an annual basis, on a decadal basis and in the longer term. Given the longevity of a forest ecosystem, studies undertaken in a period of less than 10 years may attribute trends or variations to erroneous causes or overlook underlying trends altogether. Longitudinal studies, such as that presented here, provide a better insight into the dynamics of the forest ecosystem than short-term or space-for-time studies.
