Simulating effects of climate change and ecological restoration on fire behaviour in a south-western USA ponderosa pine forest

Global climate change has the potential to affect future wildfire activity, particularly in south-western USA ponderosa pine forests that have been substantially altered by land-use practices and aggressive fire suppression. Using two regional general circulation models for the A1B greenhouse gas emission scenario, Australia's CSIRO:MK3 and Germany's MPIM:ECHAMS, we predicted fire behaviour under the 80th, 90th and 97th percentiles of future fire-weather conditions at a study site on the Kaibab National Forest, Arizona. We then altered the fuel structure by simulating alternative ecological restoration treatments: a full treatment (FULL), a full treatment with a 40.6-cm-diameter restriction on tree removal  (16" CAP) and a full treatment with a 25.4-cm-diameter restriction on tree removal (10" CAP). Model results show that differences in fire weather (temperature and fuel moistures) expected by the end of the 21st century were not influential enough to alter fire behaviour significantly, but treatments did significantly reduce severe burning. Alteration of fuel structure through the 16" CAP and FULL ecological restoration treatments caused significant declines in fire behaviour and crown fire activity under all climate scenarios. The 10" CAP substantially reduced treatment effectiveness.