The vegetation structure and condition of contracting lowland habitat for Leadbeater's possum (Gymnobelideus leadbeateri)

Abstract

Lowland Leadbeater’s possums are on a trajectory to extinction, with fewer than 40 individuals surviving in the wild. Quantification of the vegetation characteristics of their occupied habitat is urgently needed to inform strategies to conserve this genetically distinct population. We surveyed the canopy and midstorey vegetation at all remaining (nine) occupied territories and eleven abandoned territories in lowland swamp forest at the Yellingbo Nature Conservation Reserve. For each territory we quantified canopy and midstorey stem density, basal area (total and live) and vegetation condition (percentage live basal area, tree crown vigour and plant area index) within a 50-m radius of known den locations. The canopy at all locations was dominated by mountain swamp gum (Eucalyptus camphora), with most occupied sites supporting dense midstorey dominated by paperbarks, either Melaleuca squarrosa or Melaleuca ericifolia. Occupied territories had higher stem densities and better vegetation condition than abandoned territories. Stem density alone was able to predict occupancy vis-à-vis abandoned sites with a high (80%) degree of accuracy. Lowland Leadbeater’s possums occupy swamp forests characterised by high stem density, particularly in the midstorey, structural complexity and healthy vegetation. These findings can help guide habitat restoration and translocation projects currently underway to expand the area of lowland habitat for this critically endangered species.