Can fire-age mosaics really deal with conflicting needs of species? A study using population hotspots of multiple threatened birds.
Abstract
1. Locations that support high densities of a species ('population hotspots') often have a disproportionate influence on species' persistence. In fire-prone ecosystems, managers attempting to promote population hotspots of multiple species must understand how hotspot locations might shift with post-fire succession and how much overlap exists in the locations of population hotspots for multiple species. Mangers are then tasked with resolving fire-management conflicts in overlapping locations. 2. We studied three co-occurring threatened bird species in a fire-prone 'mallee' region of south-eastern Australia. We undertook field surveys for each species (1,508 surveys, 540 sites; 9-ha each). We used N-mixture models to determine (a) what factors affect species' density (including post-fire succession); (b) species' population sizes; (c) locations of species' current population hotspots and locations that may become population hotspots in the future as the post-fire successional state changes and (d) the degree of overlap in the current and possible future hotspots of species. 3. We found substantial variation in the densities of the three species across the study area, with roughly half of each species' population occurring in only 20% of potential habitat (i.e. population hotspots). All species shared a preference for subtle depressions in the landscape, resulting in substantial overlap in their population hotspots. Two species had contrasting responses to post-fire succession in the subtle depressions. As a result, there was only a narrow post-fire period that supported population hotspots of both species, creating a challenge for fire managers in these shared locations. 4. Synthesis and applications. Many studies make vague recommendations for fire-age mosaics that do not provide conservation managers with the detail they need to implement appropriate fire-age mosaics. By contrast, we explicitly quantify, then balance the conflicting post-fire needs of species in locations that support population hotspots of multiple species. Using this approach, we develop principles to guide the implementation of fire-age mosaics in such locations. This approach represents an important step towards applying fire-age mosaic theory to effectively support species conservation.