Forest die-offs associated with drought and heat have recently occurred across the globe, raising concern that changes in fuels and microclimate accompanying die-off could affect subsequent fire behaviour. Despite widespread concern, little empirical data exist

Breshears, D.

Fontaine, J.

Hardy, G.

Law, D.

Matusick, G.

Powell, S.

Ruthrof, K.

English

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A series of bulletins outlining key research in the School of Veterinary & Life Sciences | 20162016RESEARCH FINDINGSin the School of VETERINARY & LIFE SCIENCESEcology, People & EnvironmentBULLETINKATINKA RUTHROF1, JOE FONTAINE1, GEORGE MATUSICK1,2, DAVID BRESHEARS3,4, DARIN LAW3, SARAH POWELL1 AND GILES HARDY1Forest die-offs associated with drought and heat have recently occurred across the globe, raising concern that changes in fuels and microclimate accompanying die-off could affect subsequent fire behaviour. Despite widespread concern, little empirical data exist. In 2011, a massive forest die-off event occurred in the Northern Jarrah Forest, southwestern Australia, in which over 16,000ha was affected (Matusick et al. 2013). Our key aim was to determine whether this drought-induced forest die-off caused changes in fuels and microclimate characteristics, and whether this could alter fire potentials. Such information would contribute to fire management and aid in predicting drought-fire interactions in this fire-prone region. Methods and resultsFollowing forest die-off, we measured surface fuels (including leaves, twigs, branches and logs) and standing dead trees within die-off and control plots (Figures 1 and 2). Sixteen months post-die-off, die-off plots had significantly elevated 1-hr fuels (11.8 vs. 9.8 tons ha-1; litter of 0–6mm in size), but there were no significant changes in larger fuel classes (10-hr and 100-hr fuels; litter of 7–25mm and >25mm, respectively) (Figure 3). What happens to fuels and fire potentials after drought-induced forest die-off? FIGURE 1 Example of the layout of plots (white dots) at a drought-induced forest  die-off site (brown area) in the Northern Jarrah Forest5.07FIGURE 2  Litter collection to determine amount and size of fuels resulting from drought-induced forest die-offDue to stem mortality, die-off plots had significantly greater standing dead wood mass (100 vs. 10 tons ha-1) (Figure 4). Supplemental, mid-summer microclimate measurements (temperature, relative humidity and wind speed) were combined with long-term climatic data and fuel load measurements to parameterize fire behaviour models. Results suggested that fire spread rates were predicted to be 30% greater in die-off plots with relatively equal contributions from fuels and microclimate (Figure 5). A series of bulletins outlining key research in the School of Veterinary & Life Sciences | 2016If you are interested in our research and would like to know more, then please contact us on vlsresearch@murdoch.edu.au Our research bulletins can be downloaded from www.murdoch.edu.au/School-of-Veterinary-and-Life-Sciences/Our-research/Our-Bulletins/Undergraduate or postgraduate degrees, please see www.murdoch.edu.au/School-of-Veterinary-and-Life-Sciences/Our-courses/  CRICOS Code: 00125J  200150100500Standing dead tonnes ha-1Die-off ControlFIGURE 4  Mean levels of fuels of standing dead (tonnes ha -1) (95% CI) (n=36 plots, 18 die-off, 18 control)FIGURE 3  Mean levels of fuels (left) 1-hr, (centre) 10-hr, and (right) 100-hr (tonnes ha-1) (95% confidence intervals) in die-off and control plots (n=360 samples, 180 die-off and 180 control) 121081-hour fine fuels tonnes ha-110-hour fine fuels tonnes ha-1100-hour fine fuels tonnes ha-1Die-off Control Die-off Control Die-off Control2.52.01.50.200.150.100.05FIGURE 5  Effect on fire potentials (rate of spread km hr -1) via elevated fuels, fire weather, and combined across three levels of fire danger.  Fuels and climate each contributed approx. equal amounts to elevated fire spread (~30% higher in die-off plots)  0.60.40.2Rate of spread km hr-1Fuels Climate Climate+FuelsFuels Climate Climate+FuelsFuels Climate Climate+FuelsLow-moderate High Very highDrought treatment    Control    Die-offPARKSAND WILDLIFEConclusions Our results underscore the potential for drought-induced tree die-off to interact with subsequent fire under climate change. Further research on drought and fire interactions will allow us to predict where and how the forest will respond to future disturbance events. nMore informationContact: Katinka Ruthrof  E: k.ruthrof@murdoch.edu.auAcknowledgementsWe would like to thank Jason Pitman, Anna Hopkins and Shannon Dundas for assistance with field work and the Department of Parks and Wildlife for site access.References1 Matusick, G., Ruthrof, K. X., Brouwers, N., Dell, B. and Hardy, G. (2013) Sudden forest canopy collapse corresponding with extreme drought and heat in a mediterranean-type forest in southwestern Australia. European Journal of Forestry 132, 3, 497–510Authors1 School of Veterinary and Life Sciences, Murdoch University, Western Australia, 6150, Australia. 2 The Nature Conservancy, Georgia Chapter, Chattahoochee Fall Line Conservation Office, Fort Benning, Georgia, 31905, USA. 3 School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, 85721, USA.  4 Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, 85721, USA.  Excerpt from: Ruthrof, K. X., Fontaine, J., Matusick, G., Breshears, D., Law, D., Powell, S., and Hardy, G. (2015) How drought-induced forest die-off alters microclimate and increases fuel loadings and fire potentials. International Journal of Wildland Fire. http://dx.doi.org/10.1071/WF15028.

What happens to fuels and fire potentials after drought-induced forest die-off?

https://researchrepository.murdoch.edu.au/id/eprint/33264/1/drought-induced-forest-die-off.pdf

What happens to fuels and fire potentials after drought-induced forest die-off?

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