Impacts of timber harvesting on mammals, reptiles and nocturnal birds in native hardwood forests of East Gippsland, Victoria: a retrospective approach

Abstract

Summary The occurrence of mammals, reptiles and nocturnal birds was assessed in a series of successional forest sites in East Gippsland, Victoria, Australia. A total of 63 sites, representing three major forest types (Wet, Damp and Lowland) and six different forest age classes (2, 5, 10, 18, 25 y after logging and unharvested), was sampled using a range of census techniques, with each combination of forest type and age class replicated. Totals of five nocturnal bird, twenty mammal and seven reptile species were recorded during this study. Key species were selected for subsequent analysis, representing three major faunal assemblages (arboreal mammals and nocturnal birds, ground-dwelling mammals, and heliothermic reptiles). Generalised linear modelling was used to investigate the relationship between the occurrence and diversity of species within each faunal assemblage with respect to the design variables (forest type and age class). To help explain any observed intra-age-class variation in animal occurrence or diversity, structural attributes were also analysed. The study highlights the importance of retained habitat attributes (old-growth legacies) within logged forest if wildlife conservation is to be a priority. The presence and abundance of large trees were the most important habitat variables for hollow-dependent fauna such as the southern boobook and yellow-bellied glider. The southern boobook and native rodents (Rattus spp.) were most likely to be found in unharvested forest, implying a negative impact of timber harvesting. The black wallaby was the only species to show a preference for younger age classes, an expected response from a species known to browse on regrowth seedlings. The mountain brushtail possum was more likely to be found on smaller coupes. Lowland forest supported the greatest species diversity of ground-dwelling mammals when only the design variables were considered. When effects of tree height and aspect were considered separately in the model, the trend was for greater species diversity in Damp forest. It is recommended that any increase in logging intensity in either Damp or Lowland forest should be balanced with suitable measures to protect sites of high conservation value. In the short term, no single species of heliothermic reptile appeared to be disadvantaged by logging operations. Spencer's skink may benefit from an increase in regrowth forest, provided large retained trees can be used as basking sites above the regrowth canopy. Species diversity of reptiles was affected adversely by harvesting in the Lowland forests and positively in the Wet forests. The protection of microhabitat attributes during timber harvesting operations may be one management strategy that would favour the long-term survival of forest reptiles in a logged area.