This presentation by Dr Brad Murray of the University of Technology Sydney shows how a triple threat from gully plant flammability, climate change and exotic plant invasion could lead to catastrophic losses of gully habitat in the Sydney Region and highlights that reliance on gully habitat as refugia for native fauna may not be a robust strategy for the future. Presentation from Nature Conservation Council of NSW 2017 Bushfire Conference - Fire, Fauna & Ferals: from backyards to bush.

1. Landscape Variation in Plant Flammability:
Will Gullies be Safe Refugia for Native Fauna?
Dr Brad Murray, Senior Lecturer
Mr Daniel Krix, PhD Candidate
University of Technology Sydney

2. New Bushfire Era
The Guardian, 11/02/17
http://reneweconomy.com.au, 24/10/13
http://www.australiangeographic.com.au, 19/01/13
http://edition.cnn.com ,11/02/17
Sydney Morning Herald, 04/01/13

3. Implications of New Bushfire Era
 What does this new bushfire era mean
for places in the landscape, that
historically, have been less fire-prone?
 Gully vegetation
 Habitat it provides for native fauna
 Temperate forested areas of NSW
 Potential fate of gully habitat:
 Three key drivers of bushfires
Gully vegetation typically found in
temperate forested areas of NSW
D. Krix (2016)

4. Weather Conditions
 Ideal hot conditions for bushfires are
becoming more frequent in Australia:
 An overall warmer climate
 More frequent and severe very hot days
 Unseasonably hot days extending into
Spring and Autumn
 Hotter conditions lead to:
 Increases in bushfire ignition events
 Increases in bushfire spread and intensity
Sources: Hughes & Steffen (2013); Clarke (2015)

5. Topography
 Bushfires burn faster uphill than
downhill:
 Each 10° of uphill slope = fire doubles in
rate of spread
 Each 10° of downhill slope = fire halves
in rate of spread
 Also contributing to this topographic
effect:
 Sheltered from winds, less direct light,
more humid environments
Sources: Penman et al. (2007); Bradstock et al. (2010); Leonard et al. (2014); http://www.fire.nsw.gov.au, 15/05/17

6. Gullies and Ridgetops
Gully (left) and ridgetop (right) habitats in a temperate forest of NSW
D. Krix (2016)

7. The Future of Gullies
 Weather conditions are becoming more
‘ideal’ for bushfires
 Topography is not changing
 Potential outcomes:
 Increasing bushfire conditions may override
effects of topography to potentially
threaten once less fire-prone vegetation
 Areas of vegetation like gullies that have
burned less frequently in the past may
become more fire-prone
At risk – gully habitat in temperate forested
areas typically found in the Sydney region
and in remnant habitat in suburban areas
D. Krix (2016)

8. Contribution of Plant Fuel
 Bushfires are fuelled by vegetation
 Plants are the primary source of fuel
 What if gully plant species provide a
highly flammable fuel source?
 Exacerbate effects of changing
weather conditions
 Place gullies at even higher risk of
catastrophic bushfire

9. Gully vs Ridgetop Plants
 Leaves of gully plant species differ from
leaves of ridgetop plant species
 Differences suggest that gully and ridgetop
species might differ in leaf flammability
 Previous work on leaf flammability and
morphology
 “… plant traits that increase flammability
may exist in plant communities that are
rarely burnt, suggesting they have evolved
independently of landscape fire.”
Plants of ridgetop (top, Lambertia formosa) and gully (bottom, Astrotricha
latifolia) habitats, demonstrating differences in fuel (leaf) types
D. Krix (2016)
Source: Murray et al. (2013); Bowman et al. (2014)

10. Research Questions
1) Are leaves of gully plant species more flammable than leaves of
ridgetop species?
2) Can three important leaf traits explain variation in flammability?

11. Study Region, Sites and Species
 Blue Mountains, NSW
 Total of 93 plant species:
 35 gully species
 58 ridgetop species
The Blue Mountains study region (right)
and locations of ridgetop (triangles)
and gully (circles) sites (bottom left and
right)
Megan Phillips (2010); Google (2016)

12. Intrinsic Leaf Flammability
 Plant leaves are an important flammable
plant structure
 Provide a large amount of fuel, and the first
plant structures to ignite
 Leaf flammability:
 Ignitibility – time to ignition (TTI, s)
 Sustainability – burn duration (BD, s)
 Combustibility – mass loss rate (MLR, mg s-1)
Sources: Anderson (1970); Gill & Moore (1996); Simpson et al. (2016)
Hazard reduction burn at
Faulconbridge, Blue Mountains
B. Murray (2015)

13. Leaf Collection and Measurements
 Leaf collection, flammability experiments,
and measurements of leaf traits followed
established protocols
 Muffle furnace set to radiant heat 700 °C
 Leaf traits
 Field moisture content (FMC) [↑ gully]
 Mass per area (LMA) [↑ ridgetop]
 Area (LA) [↑ gully]
Methodological steps in the experiment
D. Krix (2016)
Source: Gill & Moore (1996); Murray et al. (2013); Pérez-Harguindeguy et al. (2013)

14. Time to Ignition: Gully vs Ridge
Krix & Murray (in prep.)
Lines are best fit in the
linear model, with 95%
confidence intervals
shaded
Partial R2 shows the
unique variation
explained by each
leaf trait

15. Time to Ignition: Gully vs Ridge
Krix & Murray (in prep.); photos – http://davesgarden.com
Lines are best fit in the
linear model, with 95%
confidence intervals
shaded
Partial R2 shows the
unique variation
explained by each
leaf trait
Stenocarpus salignus
Petrophile pulchella

16. Burn Duration: Gully vs Ridge
Krix & Murray (in prep.)
Lines are best fit in the
linear model, with 95%
confidence intervals
shaded
Partial R2 shows the
unique variation
explained by each
leaf trait

17. Mass Loss Rate: Gully vs Ridge
Krix & Murray (in prep.)
Lines are best fit in the
linear model, with 95%
confidence intervals
shaded
Partial R2 shows the
unique variation
explained by each
leaf trait

18. Mass Loss Rate: Gully vs Ridge
Krix & Murray (in prep.); photos – http://nelsonbaynativeplants.net
Lines are best fit in the
linear model, with 95%
confidence intervals
shaded
Partial R2 shows the
unique variation
explained by each
leaf trait
Astrotriche longifolia
Brachyloma daphnoides

19. Summary of Key Findings
 Leaves of gully species ignited significantly faster than leaves of ridgetop
species:
 Leaves with lower LMA (partial R2 = 0.78), lower FMC (partial R2 = 0.21) and
broader area (partial R2 = 0.05) ignited more quickly
 Low LMA means less dense tissue with lower thermal mass which takes less time to
heat up and combust
 High LA means thicker boundary layers with higher average temperatures which
makes it harder for large leaves to lose heat – the larger and hotter the leaf, the
easier it ignites

20. Summary of Key Findings
 Leaves of gully species ignited significantly faster than leaves of ridgetop
species:
 Low FMC predicts fast ignition, because less heat needs to be absorbed before
sufficient energy input needed to vaporise leaf water
 But, gully species had significantly higher FMC than ridgetop species
 Thus, LMA and LA combine and are much more important for predicting time to
ignition than FMC

21. Summary of Key Findings
 No difference in burn duration between leaves of gully and ridgetop
species
 Leaves of gully species were more combustible than leaves of ridgetop
species:
 Leaves with larger LA (partial R2 = 0.89) and higher LMA (partial R2 = 0.02) lost
mass more quickly
 Gully species have more overall leaf mass from their bigger area
 Gully and ridgetop species have similar burn durations
 Gully species must lose more mass than ridgetop species in that given time

22. Exotic Plant Invasion
 Gullies tend to be susceptible to
exotic plant invasion
 When dry, exotic leaves ignite
significantly faster than dry native
leaves
 Exotic plant invasion has the
potential to further increase
bushfire risk
Native-exotic boxplot comparisons of leaf flammability as a
function of both status (native, exotic) and leaf condition
(fresh = closed squares, dry = open squares)
Murray et al. (2013)
P < 0.001

23. Implications for Gullies as Refugia
 Leaves of gully species are more flammable than ridgetop species
 Intrinsic leaf flammability of gully plants has the potential to exacerbate
impacts of changing weather conditions
 Triple threat from climate change, gully plant flammability, and exotic plant
invasion that could lead to catastrophic losses of gully habitat from bushfire

24. Implications for Gullies as Refugia
 Consequences for conservation of native plant biodiversity in gullies
 Recent work is showing that gullies play a critical role in preserving
structurally complex stands of vegetation for fauna
 Impacts on fauna that use gullies as refugia
 Our work provides support for the notion that gullies may not be safe
refugia in the future
Source: Collins et al. 2012; Robinson et al. 2014; Chia et al. 2015; Swan et al. 2016

25. Acknowledgements
 UTS and the Faculty of Science
 UTS Laboratory Staff
 Members of the Murray Ecology Lab at UTS
 Colin Brown and colleagues at the RFS
 Megan Phillips, Lyndle Hardstaff