Background/Question/Methods
Future climate scenarios predict a changing climate with increased temperatures, heatwaves, prolonged droughts and changes to fire regimes. Such changes to climate will have significant effects on the fire-prone forest ecosystems of south-eastern Australia, causing widespread forest dieback and modification to faunal food and habitat resources. This study investigated the effect of fire frequency, mean annual temperature and rainfall on coarse woody debris availability and log-hollow modification in the Sydney Basin Bioregion of NSW. Sites were sampled across nine “climatic regions”; combinations of mean annual temperature (12, 14 and 16 °C) and mean annual precipitation (800, 1000 and 1200 mm). Within these climatic regions, sites were stratified by fire frequency with sites burnt once, twice, three times or greater than three times between 1972-2003. At each site, coarse woody debris (>7.5cm diameter) was surveyed in a 50 x 20m quadrat, recording diameter at both ends, length, decomposition state (1-5), surface char (% total area burnt) and hollow width and depth for each piece.
Results/Conclusions
Increasing temperatures from 12°C to 16°C saw a reduction in coarse woody debris biomass. Log-hollow abundance was dependant on mean annual rainfall, with higher rainfall reducing overall abundance of hollows at the site scale. At the individual log scale however, hollow presence was linked to increasing diameter, surface log char and decomposition state. As a general pattern, hollow presence increases with increasing diameter with the exception of high decomposition states and high surface charring. Overall, fire frequency had a limited effect on woody debris abundance, however it appears to be an important factor in hollow abundance and formation. Temperature and precipitation appear to be driving factors of coarse woody debris abundance, presumably through tree growth and mortality. These findings provide important insight into the potential ramifications of climate change on these habitat resources. Increasing temperatures, changes to rainfall and changes to burning patterns across south-eastern Australia could significantly impact total coarse woody debris biomass and hollow abundance, resources important to threatened forest fauna.