Influence of fire history on small mammal distributions: insights from a 100-year post-fire chronosequence

Aim Fire affects the structure and dynamics of ecosystems world-wide, over long time periods (decades and centuries) and at large spatial scales (landscapes and regions). A pressing challenge for ecologists is to develop models that explain and predict faunal responses to fire at broad temporal and spatial scales. We used a 105-year post-fire chronosequence to investigate small mammal responses to fire across an extensive area of 'tree mallee' (i.e. vegetation characterized by small multi-stemmed eucalypts). Location The Murray Mallee region (104,000 km superset of) of semi-arid Australia. Methods First, we surveyed small mammals at 260 sites and explored the fire responses of four species using nonlinear regression models. Second, we assessed the predictive accuracy of models using cross-validation and by testing with independent data. Third, we examined our results in relation to an influential model of animal succession, the habitat accommodation model. Results Two of four study species showed a clear response to fire history. The distribution of the Mallee Ningaui Ningaui yvonneae, a carnivorous marsupial, was strongly associated with mature vegetation characterized by its cover of hummock grass. The occurrence of breeding females was predicted to increase up to 40-105 years post-fire, highlighting the extensive time periods over which small mammal populations may be affected by fire. Evaluation of models for N. yvonneae demonstrated that accurate predictions of species occurrence can be made from fire history and vegetation data, across large geographical areas. The introduced House Mouse Mus domesticus was the only species positively associated with recently burnt vegetation. Main conclusions Understanding the impact of fire over long time periods will benefit ecological and conservation management. In this example, tracts of long-unburnt mallee vegetation were identified as important habitat for a fire-sensitive native mammal. Small mammal responses to fire can be predicted accurately at broad spatial scales; however, a conceptual model of post-fire change in community structure developed in temperate Australia is not, on its own, sufficient for small mammals in semi-arid systems.