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Fire, landscape change and models of small mammal habitat suitability at multiple spatial scales
- DI STEFANO, JULIAN, OWEN, LAURA, MORRIS, ROBERT, DUFF, TOM, YORK, ALAN
- Austral ecology 2011 v.36 no.6 pp. 638-649
- Xanthorrhoea, biodiversity, ecosystems, fire regime, habitats, mice, rats, small mammals, statistical models, variance, vegetation, vegetation structure
- 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 timeâsinceâfire (TSF) categories representing a 2â to 55âyear postâfire sequence and, on the basis of a habitat accommodation model, predicted that both species would select younger ageâclasses 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 abundance and occupancy including structural variables as predictors would be better than models including TSF. Pseudomys apodemoides selected 17â to 23âyearâold 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 (adjustedr2 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 including TSF. 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 0â20âcm. Our findings suggest that TSF may not be a good proxy for either vegetation structure or species abundance/occupancy.