Fire, landscape change and models of small mammal habitat suitability at multiple spatial scales JULIAN DI STEFANO,* LAURA OWEN, † ROBERT MORRIS, TOM DUFF AND ALAN YORK Department of Forest and Ecosystem Science, University of Melbourne, Creswick,Vic. 3363, Australia (Email: juliands@unimelb.edu.au) Abstract Fire is an important process in many ecosystems, but inappropriate fire regimes can adversely affect biodiversity.We identified a naturally flammable heathy woodland ecosystem where the use of planned fire had increased the extent of older vegetation, and quantified the abundance of two small native mammals in this landscape (silky mouse Pseudomys apodemoides and heath rat P. shortridgei).We defined four time-since-fire (TSF) categories representing a 2- to 55-year post-fire sequence and, on the basis of a habitat accommodation model, predicted that both species would select younger age-classes over older ones.We also predicted that (i) much of the variance in vegetation structure would remain unexplained by TSF and (ii) statistical models of mammal abun- dance and occupancy including structural variables as predictors would be better than models including TSF. Pseudomys apodemoides selected 17- to 23-year-old sites, while there was no evidence that P. shortridgei selected a particular TSF category, findings that were inconsistent with our predictions. In line with our predictions, relatively large portions of the variance in vegetation structure remained unexplained by TSF (adjusted r 2 for four structural variables: 0.24, 0.29, 0.35 and 0.57), and in three of four cases there was strong evidence that statistical models of mammal abundance and occupancy including structural variables were better than those includingTSF. At the site scale (hectares), P. shortridgei abundance was positively related to the cover of dead material at the base of Xanthorrhoea plants and at the trap scale (metres), the trapability of both species was significantly related to vegetation volume at 0–20 cm. Our findings suggest that TSF may not be a good proxy for either vegetation structure or species abundance/occupancy. Key words: Akaike’s information criterion, habitat accommodation model, habitat selection, landscape compo- sition, statistical model. INTRODUCTION Fire is an important process, maintaining the structure and function of many ecosystems (Gill 1981; Bond & Keeley 2005). Through actions such as fire exclusion and prescribed burning, humans have the capacity to alter the spatial and temporal occurrence of fire in ways that may affect biodiversity and ecosystem func- tion (Bradstock et al. 1995; Stephens & Ruth 2005). A potential effect of altered fire regimes is changed land- scape composition, a factor identified as important for biodiversity conservation (Bennett et al. 2006). Land- scape composition is an emergent property defined by the number of different land cover types and their relative proportions, and may be influenced by events that alter vegetation age. For example, active fire sup- pression will increase the mean age of vegetation com- munities and, over time, result in simplified landscapes dominated by older vegetation classes. We observed this phenomenon in a heathy wood- land ecosystem in south-eastern Australia where management practices over a number of years had resulted in a 55-year absence of fire from 23% of the landscape, while only 25% had been burnt within the last 10 years. Heathy ecosystems are highly flam- mable and although natural fire regimes are difficult to reconstruct, frequent fires are common and fire return intervals greater than 50 years are likely to be rare and ecologically detrimental (Keith et al. 2002). Given the natural flammability of these ecosystems, management practices that reduce fire frequency and extent will alter landscape composition in ways that may adversely affect some components of the system. The habitat accommodation model (Fox 1982; Monamy & Fox 2000) provides a framework within which the effects of landscape composition on some faunal communities can be assessed. The model proposes that post-disturbance recolonization and subsequent persistence by particular species is driven by the interacting effects of vegetation parameters (density, floristic diversity, etc.) and interspecific *Corresponding author. † Present address: 122 main Road, Paynesville, Vic. 3880, Australia. Accepted for publication September 2010. Austral Ecology (2011) 36, 638–649 © 2010 The Authors doi:10.1111/j.1442-9993.2010.02199.x Journal compilation © 2010 Ecological Society of Australia