Rainfall immediately before and after fire promotes long-term occurrence of a rare, fire-sensitive passerine.

Abstract

Attributes of fire regimes are known to drive habitat suitability for many species in fire-prone environments. Comparatively little is known about how abiotic conditions (e.g. rainfall events, cumulative rainfall, drought) at the time of fire may affect long-term (>2-years) post-fire occurrence. We sought to a) establish whether the post-fire development of heathland habitat for the endangered mallee emu-wren is influenced by rainfall within 12-months before or after the most-recent fire, b) identify the preferred fire-age of heathland vegetation for the mallee emu-wren, and c) map those habitats most likely to support the species across a large reserve ([~]271,000 ha), Ngarkat Conservation Park, from which it has been extirpated. Using historical presence records, collected prior to the extirpation of mallee emu-wrens from the study area, we implemented a random-forest modelling approach to predict relative likelihood of occurrence (considered a proxy for probability of suitable habitat). Rainfall in the 12-months before and after fire had a positive effect on relative likelihood of mallee emu-wren occurrence. The development of high-quality mallee emu-wren habitat required at least 420 mm of rainfall in the 12-months prior to the most recent fire. Only 35% of Ngarkat received rainfall above this threshold prior to the most recent fire. Rainfall in the 12-months after fire positively influenced relative likelihood of mallee emu-wren occurrence, though the effect was less pronounced than pre-fire rainfall. Relative likelihood of mallee emu-wren occurrence peaked 15 years after fire, with an [~]10-year peak time window of relative occurrence (10-20-years). This study highlights that abiotic conditions at the time of fire, particularly rainfall in the 12-months preceding fire, have long-lasting impacts on relative probability of occurrence for this fire-sensitive species. Targeting fire management in ways that maximise post-fire occurrence of the mallee emu-wren - particularly by burning senesced habitat following periods of elevated rainfall - has potential to enhance conservation outcomes. Given the substantial and long-term impact of rainfall around the time of a fire identified in this study, short-term climatic conditions deserve greater attention in a range of ecosystems where managers aim to use fire to manipulate habitat for the benefit of fire-sensitive species.