Quantifying the effects of topographic aspect on water content and temperature in fine surface fuel
Petter Nyman A B , Daniel Metzen A , Philip J. Noske A , Patrick N. J. Lane A and Gary J. Sheridan A
+ Author Affiliations
- Author Affiliations
A School of Ecosystem and Forest Sciences, The University of Melbourne, 221 Bouverie Street, Parkville, Vic. 3010, Australia.
B Corresponding author. Email: nymanp@unimelb.edu.au
International Journal of Wildland Fire 24(8) 1129-1142 https://doi.org/10.1071/WF14195
Submitted: 27 October 2014 Accepted: 21 August 2015 Published: 25 November 2015
Abstract
This study quantifies the effects of topographic aspect on surface fine fuel moisture content (FFMC) in order to better represent landscape-scale variability in fire risk. Surface FFMC in a eucalypt forest was measured from December to May (180 days) on different aspects using a novel method for in situ monitoring of moisture content (GWClit) and temperature (Tlit) in litter. Daily mean GWClit varied systematically with aspect. North (0.07 ≤ GWClit ≤ 1.30 kg kg–1) and south (0.11 ≤ GWClit ≤ 1.83 kg kg–1) aspects were driest and wettest respectively, whereas east and west were somewhere in between. On the warmest day (38.9°C), the maximum Tlit on north (43.7°C) and south (29.8°C) aspects differed by 13.9°C. Aspect-driven variation in Tlit and GWClit is exacerbated by vegetation, which increases markedly in density with decreasing solar exposure. GWClit was below fibre saturation point (<0.35 kg kg–1) on 49 and 128 days on south and north aspects, respectively, demonstrating that fuels beds are often in different stages of drying and therefore subject to different hydrological processes depending on landscape position. This terrain-related variability in moisture dynamics strongly affects the spatial connectivity of fuels, and may be more important for predicting landscape-scale burn outcomes than sub-daily fluctuations at a point.
Additional keywords: fire danger, fire management, fuel availability, soil, weather.
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