There is a range of methods employed by VicForests during timber harvesting operations including; Regrowth Retention Harvesting, Single-tree Selection Harvesting, Thinning, Clearfell and Salvage Harvesting as our most utilised methods.
VicForests will chose the most appropriate timber harvesting method based on such factors as the forest type, soil, stakeholder feedback and presence of environmental values.
Different harvesting methods are applied on different sites to help ensure the forest regrows successfully and eco-system connectivity is maintained while also allowing for the most effective recovery of wood to go into everyday timber products.
Regrowth Retention Harvesting
Regrowth Retention Harvesting is the newest harvesting method to be adopted by VicForests for Ash forest types and it works by retaining additional areas to provide habitat for native animals.
From above these retained areas can often look like islands (image:right) and they are left to help ensure older forest develops in areas available for timber harvesting
Retention harvesting an alternative to traditional clearfell harvesting methods and aims to mimic natural disturbances as well as protect biodiversity values.
This new method comes as a result of many years of research as part of VicForests’ collaborative Retention Harvesting Project, community and expert feedback and strong support and advice from other forest management organisations, such as Forestry Tasmania.
VicForests is using retention harvesting to ensure older forest elements are retained and recruited in areas available for timber harvesting.
To meet these aims, Regrowth Retention Harvesting involves the retention of forest patches so that more than 50% of the harvested area is located within one tree length of retained forest.
VicForests will use this new harvesting system in at least 50% of the area harvested of Ash within the range of the Leadbeater’s Possum to assist in the possum’s recovery and persistence, by providing increased connectivity of habitat, and the recolonisation of areas following harvesting
Single-tree Selection Harvesting
Single tree selection is a low intensity method of harvesting where individual or small groups of trees are selected and removed within an area planned for timber harvesting.
This method looks for trees within areas of forest that contains a mix of different age classes ranging from young five year old regrowth trees to old growth trees that have already begun forming natural hollows.
The trees are selected on the basis of diameter and condition, with smaller and younger trees retained to grow on to the next harvest and the old growth trees left for future species habitat.
By selecting from the remaining competing trees, the retained trees have access to enough light, moisture and soil nutrients to respond and grow larger.
To be selected for single tree selection harvesting, trees need to be aged between 60 and 120 years. Both good quality trees will be removed for sawlog and poorer quality mature trees will be removed to allow the younger trees to become the future sawlogs.
Any remaining trees are either left behind as habitat trees or retained to continue to grow. When groups of trees are harvested during this process, the mechanical disturbance allows a seedbed for new seedlings to naturally establish.
Single tree selection is used when the forest contains an uneven age class of trees, ranging from young regrowth trees to old growth habitat trees and everything in between. This method also seeks to retain this uneven age class for future single tree selection.
Thinning is a harvesting method that removes up to 50 per cent of the smaller trees to allow remaining trees to grow more quickly.
A thinning operation usually takes place in 20-25 year old regrowth forests. VicForests will undertake Thinning when predictions indicate that the operation will generate viable commercial or ecological returns.
VicForests’ commercial objectives for Thinning are to:
increase the proportion of larger diameter sawlogs at final harvest;
shorten rotations to improve total economic returns;
maintain medium to long-term timber supply levels in areas with substantial areas of regrowth forest;
help meet existing residual log sales commitments.
Other than commercial and timber yield benefits, Thinning may also be used for a number of other ecological and environmental outcomes such as:
achieving an overall increase in water yields;
reducing forest fuel loads in high bushfire risk zones and;
the acceleration of hollow development through intentional damage of retained trees, benefiting hollow-dependent fauna such as the Leadbeater’s Possum.
VicForests undertakes Salvage operations after large fire events in areas available for timber harvesting in order to recover timber from fire-killed trees.
We will prioritise fire-killed areas for harvest soon after the fire event to ensure this timber can be utilised before the wood quality deteriorates.
Approximately 30% of all clearfell sites are retained for a number of reasons. These retained areas are normally in buffers around the edges of the harvesting area.
It is the most reliable method for achieving successful forest regrowth after harvesting and is the safest harvesting system for forest workers in our tall Ash forests.
Following a clearfell operation the area undergoes a regeneration burn and has seed sown by helicopter or hand to ensure the forest regrows.