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

Joe Greet,Dan Harley,Darcy Watchorn,David Duncan,Kita Ashman

doi:10.1071/am20047

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.

Highlights

Anthropogenic land use is the major driver of biodiversity loss, with agriculture the leading contributor to deforestation, forest fragmentation and degradation (Chaudhary et al 2016)
The third forest type occupied by the species is lowland swamp forest (100–120 m) dominated by mountain swamp gum (Eucalyptus camphora), which currently contributes,0.1% of available habitat
We considered that site occupancy would vary according to stem density, live basal area, and vegetation condition

Summary

Introduction

Anthropogenic land use is the major driver of biodiversity loss, with agriculture the leading contributor to deforestation, forest fragmentation and degradation (Chaudhary et al 2016). The species occupies three distinct forest types spanning a broad elevation gradient (100–1500 m Australian Height Datum) (Harley 2004a; DEPI 2014). These include one outlying lowland population that is disjunct from highland populations. 96% of the remaining habitat known to support extant populations of Leadbeater’s possum is montane ash forest (600–1300 m), typically dominated by mountain ash (Eucalyptus regnans) or alpine ash (Eucalyptus delegatensis). Subalpine woodland (1300–1500 m) dominated by snow gum (Eucalyptus pauciflora) accounts for ,4% of the remaining available habitat within the species’ range. The third forest type occupied by the species is lowland swamp forest (100–120 m) dominated by mountain swamp gum (Eucalyptus camphora), which currently contributes ,0.1% of available habitat.

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Discussion

Conclusion