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Ms Helen Stephens

Ms Helen Stephens

PhD student

Topic: does aggregated retention provide suitable habitat for mammal conservation in old growth forests?

University of Tasmania

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Traditional harvesting (clearfell, burn and sow) of wet old growth forests generally removes all remnants of the native uneven-aged stand, replacing them with even-aged stands of uniform structure. Old growth forests have complex forest structures such as tree hollows and coarse woody debris which are important habitats for many animals and are generally not created within the usual forestry operations.

Forestry Tasmania is reducing the level of traditional clearfell harvesting in wet forests. To achieve this, they are phasing in aggregated retention, which maintains patches of forest (>1ha size) in operational coupes for at least one rotation (~80 years). The objective of this method is to retain old growth species and structures to provide wildlife habitat, refuge and seed banks for regeneration. Aggregated retention was developed to emulate natural disturbance regimes and allows old-growth influences to remain within an operational coupe. Retained aggregates may be “island aggregates” which are surrounded by the harvested area or “edge aggregates” which are connected to adjacent native stands. 

The aim of my project is to determine if aggregated retention in old growth forestry is an adequate management strategy for conservation of small to medium-sized native mammals. This will be achieved by monitoring mammal use of operational aggregated retention coupes in the Styx and Huon valleys, with clearfell coupes and non-adjacent native forest sites used as control sites. In addition to this, I will evaluate the influence of aggregate characteristics and habitat variables (e.g. vegetation type and cover, presence of hollows and coarse woody debris) on mammal activity, biodiversity, population demographics and diet.

After completing a Bachelor of Science in Environmental Science at the University of Sydney, I combined my love of plants and animals for my honours project on plant-herbivore interactions in Royal National Park (Sydney), supervised by Dr Clare McArthur (previously of the University of Tasmania and the CRC for Sustainable Production Forestry). My interest in ecological studies has led me to the wondrous old growth forests of Tasmania, where I will be working closely with Forestry Tasmania to assess the conservation value of aggregated retention within production forests. 

My supervisors are Dr Julianne O’Reilly-Wapstra and Professor Brad Potts from the browsing and eucalypt genetics groups at the University of Tasmania, Dr Sue Baker from Forestry Tasmania and Dr Sarah Munks from the Tasmanian Forestry Practices Authority.

My PhD studies contribute to CRC for Forestry Project 4.2 Biodiveristy (subproject: biodiversity benefits of alternatives to clearfelling).

I was recently awarded a Holsworth Wildlife Research Endowment. Click to read more