Fire modelling in Tasmanian buttongrass moorlands. IV. Sustaining versus non-sustaining fires

Abstract

Buttongrass moorlands are widespread in western Tasmania. In these moorlands, the ability to conduct burning without having to rely on hard fuel boundaries (e.g. vegetation which is too wet to burn, water courses, mineral earth breaks and/or roads) would be a major advantage to land managers. Such burning relies on fires self-extinguishing and is normally referred to as unbounded burning. The aim of this project was to model the probability of fires extinguishing using the data from 156 buttongrass moorland fires. The variables used were wind speed, dead fuel moisture and site productivity. The model, derived from a combination of logistic regression and classification tree modelling, predicts that fires will self-extinguish over a wide range of conditions in low productivity moorlands but, in medium productivity moorlands, the conditions within which fires will self-extinguish will be much more restrictive. As a result, the technique of unbounded burning should be widely applicable in low productivity moorlands, but will be of marginal utility in medium productivity moorlands.

Fuel Moisture Thresholds in the Flammability of Calluna vulgaris

“…Previous, similar research [24] has shown that wind speed is an important control on the development of sustaining fires; although the addition of this to our models did improve their predictive ability, the additional variance explained after inclusion of lower-canopy fuel moisture (FMC2) was not statistically significant. The majority of our tests were, however, completed at rather high wind speeds (Table 3) and we anticipate that tests in a wider range of conditions would lead to it having a significant effect.…”

“…A number of authors (e.g. [23][24][25][26][27][28]) have used field experiments to identify conditions necessary for sustained ignition whilst others (e.g. [29][30][31]) have demonstrated a significant relationship between fuel moisture and flammability in laboratory tests.…”

Fire spread in chaparral—'go or no-go?'

“…While these fires can be significant events, our ability to predict when fire will spread in these fuels is limited by two factors: (1) current fire spread models were not designed primarily for live fuels and (2) only a limited set of experimental data to develop and test models exists. Recent work in Europe and Australia has measured and modeled fire spread in various live fuels (Fernandes 2001;Marsden-Smedley et al 2001;Bilgili and Saglam 2003;De Luis et al 2004;Morvan and Dupuy 2004). In the USA, limited modeling of fire spread in live fuels has occurred (e.g.…”

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

“…Using geospatial modelling, Wood et al (2011a) demonstrated that the probability of fire occurrence varies with landscape setting, resulting in a self-reinforcing pattern such that landscape fire is channelled across flammable sedgelands but rarely affects forest. The strongly contrasting flammability of forest and sedgelands under moderate fire conditions reinforces these effects (Marsden-Smedley et al 2001). The association of forest with well-drained valley slopes suggests that soil drainage and aeration likely affect tree growth (Wood and Bowman 2012).…”

“…The model was implemented in NetLogo 6.0.1 (Wilensky 1999). Each cell in the landscape can be in either a forest or savanna state, with savanna cells more flammable than forest (as per Marsden-Smedley et al 2001). At the start of each simulation there is a sharp transition from forest to savanna in the horizontal mid-point of the grid (200 × 50 cells).…”