Ecosystem type and species’ traits help explain bird responses to spatial patterns of fire

Abstract

BackgroundUnderstanding how temporal and spatial attributes of fire regimes, environmental conditions, and species’ traits interact to shape ecological communities will help improve biodiversity conservation in fire-affected areas. We compared the influence of time since the last fire at a site, and the area and diversity of post-fire successional vegetation surrounding a site (i.e., the “spatial context” of fire), on bird species and functional groups in two ecosystems in south-eastern Australia. These ecosystems, semi-arid “mallee” woodlands and temperate “foothill” forests, differ in stand-regeneration patterns, climate, and topography. For 22 bird species in mallee woodlands, 33 species in foothill forests and four functional groups of birds in both ecosystems, we fitted non-linear models that differed in fire regime predictor variables.ResultsIn foothill forests, models that included both time since fire and a spatial context variable explained more variation in bird abundances than models that included only time since fire or a spatial variable. In mallee woodlands, the addition of spatial attributes of fire helped explain the occurrence of several species, but this finding was muted when measured across all species. There were key differences between ecosystems in functional group responses to fire regimes. Canopy/upper-midstorey foragers were positively associated with the amount of late-successional vegetation in mallee woodlands, but not in foothill forests. Lower-midstorey foragers showed a decline response to the amount of late-successional vegetation in mallee woodlands and a contrasting incline response in foothill forests. However, lower-midstorey foragers showed a similar response to the amount of surrounding early-successional vegetation in both ecosystems—decreasing in abundance when > 50% of the surrounding vegetation was early-successional.ConclusionsThe influence of fire regimes on birds varies among species within sites, across landscapes and between ecosystems. Species’ foraging traits influence bird associations with fire regimes, and help to make sense of a myriad of relationships, but are usefully understood in the context of ecosystem types and the regeneration patterns of their dominant flora. The spatial context of fire regimes is also important—the amount of successional vegetation surrounding a site influences bird abundance. Fire management strategies that incorporate the spatial contexts of fire regimes, as well as the temporal and ecological contexts of fire regimes, will have the greatest benefits for biodiversity.