Disturbed Birds: The function of fire in shaping patterns of avian diversity in south-eastern Australia
Creators: name: Reynolds, Zoe
Publisher: name: The Australian National University
Year: 2019

description: Fire is a widespread environmental process that influences the diversity, distribution, and abundance of plants and animals. However, we still have a limited understanding of how species and communities respond to different components of fire regimes, and few studies have explored effects of fire on animals in a phylogenetic context. In this thesis, I present four studies that explore how fire influences spatial and temporal variation in the abundance, diversity, and structure of bird communities across semi-arid mallee woodland in south-eastern Australia. First I explore how a major fire event and a prolonged period of drought combined to influence temporal variation in bird communities over an 18-year period. While I found little evidence for an interactive effect between these processes, both fire and rainfall had significant effects on bird communities, highlighting the importance of considering multiple disturbance processes in long-term studies. I found phylogenetic signal in the temporal fire-response patterns of bird species, suggesting that fire-responses may be mediated by phylogenetically-conserved ecological traits. Next I investigate the role of unburnt patches as refuges for birds in a post-fire landscape, testing which characteristics determine their value as refuges, and whether they contribute to spatial patterns of phylogenetic diversity. I found no evidence that unburnt patches influenced spatial patterns in phylogenetic diversity across the fire scars. Unburnt patches functioned as refuges for birds following fire, but this refuge effect weakened with time since fire. I found that short-term post-fire species richness was associated with habitat differences between burnt and unburnt areas, but not with habitat differences among unburnt areas, nor with their context within the landscape, suggesting that even small or isolated unburnt patches could be important in maintaining bird diversity and facilitating recovery of bird communities across large fire scars. Then I explore how increased frequency of fire events affects the post-fire recovery of mallee woodland birds and their habitat, and then conduct a meta-analysis to examine the published scientific literature on terrestrial vertebrate responses to infrequent versus frequent fires in fire-prone ecosystems around the world. In mallee woodland, richness and abundance of birds were negatively impacted by repeated fires, suggesting that increased fire frequency will have long term negative effects on bird communities in this ecosystem. Globally, there was a neutral overall effect of both frequent and infrequent fires on richness and abundance of terrestrial vertebrates. Effects of fire were instead determined by taxonomic group, geographic location, biome, and fire type. Finally, I use a phylogenetic modelling framework to investigate the influence of fire history on phylogenetic community structure, and discuss the contribution of fire to community assembly processes. I showed that there was significant phylogenetic overdispersion in bird species co-occurrence, which could not be accounted for by fire history of sites or the set of traits included in this study. My results suggest that competition among closely related species may be the key mechanism driving post-fire reassembly of mallee woodland bird communities, but that fire does not appear to alter the relative importance of competition and environmental filtering.