Fire and fuel in Tasmanian buttongrass moorlands: regimes, characteristics, behaviour and management Jon B. Marsden-Smedley BSc. (hons) Submitted in fulfilment of the requirements for the degree of Doctor of Philosphy School of Geography and Environmental Studies Faculty of Science and Engineering University of Tasmania March 1998 Declaration This thesis contains no material which has been accepted for the award of any otlter degree or diploma in any tertiary institution and to tlte best of my knowledge and belief, this thesis contains no material previously published or thee pe<S , exce~/7efecencc ;, made ;n the text. Jona asil Marsdcn-Smedlr I . Febru~ 1998 Authority of access IT Abstract The aims of this thesis are to examine the fire regimes, fuel characteristics, fire behaviour and fire management of Tasmanian buttongrass moorlands. Major changes have occurred to the fire regime of southwest Tasmania over the past 170 years. The fire regime has changed from an Aboriginal regime of mostly frequent low intensity buttongrass moorland fires to the early European fire regime of frequent high intensity fires in all vegetation types, to a regime of low to medium intensity buttongrass moorland fires and finally to the current regime of very few fires. Buttongrass moorland fuel accumulation rates in western and southwestern Tasmania can be divided into two productivity groups, based on geological type. Within each productivity group, the vegetation cover and/or the time since the last fire can be used to model fuel load and the dead fuel load. Dead fuel moistures in buttongrass moorlands can be predicted from the relative humidity and dew point temperature. The main influences on buttongrass moorland rates of fire spread are wind speed, dead fuel moisture and age. Flame height in these moorlands is highly correlated with the fuel consumption rate, which in tum is controlled by the rate of fire spread, fuel load and dead fuel moisture. Operational fire behaviour models have been developed which use the wind speed, temperature, relative humidity, age and site productivity to predict the frre spread rate and flame height. The prescriptions for burning buttongrass moorlands have also been refined. Wildland fire management is a major problem in western and southwestern Tasmania. This is mainly due to the extensive area of fire-adapted and fire-dependent vegetation, the small area burnt by natural fires, the high incidence of arson in some areas and across much of the region, the old-growth nature of the buttongrass moorland vegetation. If we are going to preserve the ecological values of the region whilst minimising the economic and social costs of management, we are going to have to reintroduce frre into the region. Such reintroductions of fire will need to be performed in a highly sophisticated manner in order to maximise the potential that they will achieve the desired outcomes. m Acknowledgments During the course of this project, assistance was obtained from many people, without whom it could not have been performed. I am greatly indebted to my supervisors: Wendy Catchpole, who provided much needed statistical advice throughout the project, Jamie Kirkpatrick whose wholehearted enthusiasm kept me going, and Mick Brown for his interest and support. I would also like to thank Tim Rudman, Tony Blanks, Dylan Kendall and Adrian ' Pyrke who assisted greatly with the fuel characteristics, fuel moisture and fire behaviour modelling sections of the project. As with any project of this kind, many many days were spent in the field collecting the data. Many people assisted in this aspect of the project, but the efforts of Murray Haseler, Alex van de Vusse, Ian Balmer, Stuart Hagell, Dylan Kendall, Adrian Pyrke, Tracey Jarvis, and Mike Cooper deserve special thanks. The assistance of the Department of Environment and Land Management rangers is also appreciated, in particular the rangers from South-West National Park based at Maydena and from the Franklin- Lower Gordon Wild Rivers National Park based at Queenstown. Dylan Kendall coaxed the fire regime maps out of the GIS. Comments on the draft manuscript were made by Wendy Catchpole, Jamie Kirkpatrick, Kristen Williams, Mick Brown, David Heatley and Shirley Grosvenor. John Bally and Paul Fox-Hughes, weather forecasters at the Bureau of Meteorology, Hobart, provided first class weather forecasts without which the project's burning program could not have proceeded. This project received extensive funding from the Parks and Wildlife Service. Finally, I would like to thank Kristen Williams for her support. IV Contents Page Declaration I Authority of access n Abstr act m Acknowledgments IV Contents v 1 Introduction 1.1 Background I 1.2 Fire and vegetation dynamics 2 1.3 Wildland fire regimes and fue management 5 1.3.1 Fire regime 5 1.3.2 Interactions between the fuel array and fife behaviour 6 1.3.3 Fire behaviour modelling 7 1.3.4 Buuongrass moorland fire management strategy 8 1.3.5 Hazard-reduction burning 10 1.3.6 Habitat-management burning in buttongrass moorlands 11 1.4 Thesis aims 13 2 Study sites and ecological background 14 2.1 Background 14 2.2 Vegetation associations in lowland areas of western and southwestern Tasmania 14 2.2.1 Bunongrass moorland 15 2.2.2 Wet scrub 16 2.2.3 Wet eucalypt forest 16 2.2.4 Rainforest 16 2.3 Buttongrass moorland distribution and ecology 17 2.4 Climate 18 2.5 Landforms 18 2.6 Geology and soil types 18 3 Fire regimes in southwestern Tasmania 20 3.1 Background 20 3.2 Recorded fifeS in southwestern Tasmania 21 3.3 Methods of assessing fire regimes 23 3.3.1 Published papers 23 3.3.2 Field data and aerial photograph interpretation 24 3.3.3 Fire history map production 26 3.3.4 Fire regimes in the different vegetation types of southwestern Tasmania 26 3.4 Results 30 3.4. 1 Aboriginal fire regime 30 3.4.2 Early European fue regime between 1830 and 1940 32 3.4.3 Fire regime between 1940 and 1970 43 3.4.4 Post !970 fire regime 44 3.4.5 Fire regimes and area burnt in different time periods 45 3.4.6 Interactions between drought years and area burnt 57 3.5 Discussion 58 4 Fuel load 63 4.1 Background 63 4.2 Methods 64 4.2.1 Study site locations 64 4.2.2 Site age 66 4.2.3 Fuel data collection 67 4.3 Results 69 4.3.1 Fuel load models 69 4.3.2 Models for dead fuel load 74 4.4 Discussion 76 v Contents (cont.) Page 5 Fuel moisture 79 5.1 Background 79 5.2 Methods 82 5.2.1 Fuel moisture data collection 82 5.2.2 Weather data collection 84 5.2.3 Hazard stick data collection 84 5.2.4 Effect of variation in aspect on dead fuel moisture 85 5.2.5 Dead fuel moisture model test data 85 5.3 Results 85 5.3.1 Data summary 85 5.3.2 Dead fuel moisture response times 87 5.3.3 Dead fuel moisture modelling using weather data 88 5.3.4 Dead fuel moisture modelling using hazard stick data 89 5.3.5 Published fuel moisture prediction models examined 91 5.3.6 Dead fuel moisture model evaluation 93 ' 5.4 Discussion 94 6 Fire behaviour 96 6.1 Background 96 6.2 Methods 97 6.2.1 Site locations 97 6.2.2 Fuel loads 98 6.2.3 Fuel moisture 98 6.2.4 Fuel heat content 98 6.2.5 Meteorological data 99 6.2.6 Burning block design, fire ignition and control 99 6.2.7 Rates of fire spread and flame heights 100 6.2.8 Fuel consumption 101 6.3 Results 102 6.3.1 Published fire behaviour models 102 6.3.2 Buttongrass moorland rate of fire spread model 109 6.3.3 Buttongrass moorland flame height model 113 6.3.4 Buttongrass moorland flank and back fire predictions 114 6.3.5 Fire behaviour model evaluation 115 6.4 Discussion 115 6.4.1 Fire behaviour model performance 116 6.4.2 Factors influencing buttongrass moorland fire behaviour 116 7 Fire management in buttongrass moorlands 119 7.1 Background 119 7.2 Changes in fire regime in southwestern Tasmania 119 7.3 Interactions between different aspects of buttongrass moorland fuel characteristics 121 7.4 Buttongrass moorland dead fuel moisture 122 7.5 Buttongrass moorland fire behaviour 122 7.6 Buttongrass moorland operational fire management 123 7.6.1 Aims of buttongrass moorland operational fire management 123 7.6.2 Buttongrass moorland operational frre behaviour model parameters 124 7.6.3 Buttongrass moorland operational fire behaviour model equations 126 7.6.4 Prescriptions for conducting buttongrass moorland burning 128 7.7 Further fire research required in buttongrass moorlands 129 7.7.1 Further fire regime research required in buttongrass moorlands 130 7.7.2 Further fire ecology research required in buttongrass moorlands 130 7.7.3 Further fuel characteristics research required in buttongrass moorlands 131 7.7.4 Further fuel moisture research required in buttongrass moorlands 131 7.7.5 Further fire behaviour research required in buttongrass moorlands 132 7.8 Outcomes of the buttongrass moorland frre behaviour models 132 8 Fire in wildland vegetation 135 9 :Refer ences 140 VI Contents (cont.) Appendices Page Appendix 1 Historical references used 160 Appendix 2 Site ages in southwestern Tasmania 165 Appendix 3 Fire records in southwestern Tasmania 173 Appendix 4 Fuel modelling site data 181 Appendix 5 Fuel moisture data 184 Appendix 6 Fire behaviour data 187 Appendix 7 Papers and reports produced from this thesis 191 Figures Figure 2.1 Buttongrass moorland near Melaleuca in southwestern Tasmania 15 Figure 3.1 Site burnt by a lightning fire in the Hardwood Valley 22 Figure 3.2 Vegetation map of southwestern Tasmania 27 Figure 3.3 Destruction of forested vegetation by fm: near Mt Read 37 Figure 3.4 Burnt vegetation in the Southern Ranges in the 1920s 37 Figure 3.5 Area burnt