The effects of inter-fire interval on flora-fauna interactions in a sub-alpine landscape

Attributes of the historical fire regime can influence fauna dynamics by moderating vegetation composition and the availability of appropriate habitat. Despite this, the indirect impacts of specific aspects of the long-term fire regime are often overlooked. Here we conduct a field survey at 27 sites in sub-alpine forests of Namadgi National Park (Australia) to determine if one aspect of the historical fire regime, inter-fire interval, influences vertebrate fauna and fauna habitat. Sites were stratified between three inter-fire interval categories (20, 65-70 and 83 years between the previous two fires) in areas last burned 15-years prior to the field survey. All other environmental attributes thought to impact vegetation dynamics were controlled for in the study design. Fauna activity was monitored for four weeks using trail cameras and 15 habitat attributes were assessed using field and remote-sensing survey techniques. Most fauna and habitat variables did not differ among the inter-fire interval categories. However, mountain brush-tail possum detections increased with inter-fire interval length, with 260% more observations within the older treatment when compared with the younger treatment. Large tree density, maximum tree height, and tree canopy cover were 40%, 38% and 12% higher within the older than younger treatment, respectively. Conversely, small tree density was 78% lower within the older treatment. Our results show a limited response of fauna to historical fire-return intervals of > 20 years within a fire-prone forest, however also highlight that species-/habitat-specific responses do manifest via indirect effects pathways at longer fire return intervals.