Effects of fire severity on the composition and functional traits of litter-dwelling macroinvertebrates in a temperate forest

Abstract

High severity fires are likely to become more prevalent with global climate change, so it is critical that we understand their effects on forest ecosystems. Leaf litter dependent fauna are likely to be particularly vulnerable to habitat loss resulting from fire, which often destroys their leaf litter habitat. We hypothesised that, as fire severity increased: (1) richness and abundance of macroinvertebrate litter fauna would decline; (2) species composition would change; and (3) species responses would depend on morphological and trophic traits, with proportions of larger, winged and predatory species increasing with fire severity. To test the effects of fire severity on the composition and functional traits of litter-dwelling macroinvertebrates, we collected macroinvertebrates using litterbags and standardised hand searches of logs at unburnt, low severity (ground burnt) and high severity (crown burnt) burnt eucalyptus forests (n = 7) in south eastern Australia, three years after fire. Litter-dwelling macroinvertebrates were larger, less abundant and less species-rich at high severity burnt than unburnt sites and species composition differed from unburnt and low severity burnt sites. Fire severity did not affect the proportion of winged species or individuals. Thus, we suggest small bodied species may struggle to recolonize through limited dispersal ability or may be limited by the drier post-fire environment. Increases in large scale, high severity fires may therefore result in assemblages dominated by larger macroinvertebrate species, but will also be associated with lower species richness.