• Peat burning and consequent subsidence (Figure 2) – Dry peat smolders for long periods and burns down to the water table. When this happens, tree roots are exposed and both the peat and forest vegetation become unstable, resulting in peat subsidence, massive tree falls and the consequent loss of large areas of forest.
Figure 2a & 2b photographed by Susan Cheyne and Marie Hamard
• Effects on flora – PSF trees are not adapted to fire (most have very thin
bark), so tree mortality post-fire is high. Although fires are generally low intensity, their slow spread rate means fire is in contact with trees for long periods, heating up the bark. Fire can kill 23-44% of trees with >10cm DBH (diameter at breast height) and 95% of stems with >1cm DBH (Harrison et al, 2008). They alter species composition in the area with little regeneration even 15 years after burning (Cochrane et al, 1999). Tree mortality in severely burnt areas of PSF is virtually 100%, as most trees fall once the supporting peat is burnt away (Figure 2b).
• Effects on fauna – Animals dependent on intact PSF will clearly be impacted directly by fire. Loss of habitat due to forest fires is one of the primary reasons of decreasing orangutan population. More information on the plight of the orangutans can be found in this link: http://orangutanfoundation.wildlifedirect.org/
Indirect effects are also likely. For example, gibbons sing less frequently in smoky conditions, which could interfere with territorial spacing and ultimately, reproduction (Chayne, 2007).