These notes provide some basic guidelines on the logging of native forests on farms in northern New South Wales.

The selection of the correct silvicultural technique is determined by forest type and forest condition.

Logging should attempt to improve the vigour of any forest stand in order to maximise its future productivity with regard to growth rate and commercial return.

These notes should assist landowners to better understand principles and techniques of native forest thinning and management.

Forest harvesting should attempt to improve the vigour of the forest in order that its growth rate and options for commercial returns are maximised. In general this will require the removal of many of the slower growing older or suppressed trees, as well as trees which are ready for harvesting now. The forest manager is attempting to replace the harvested trees with regeneration and/or advanced regrowth, and provide space for these trees to grow more rapidly than what they would in a stand that has not been logged.

Sometimes the removal of some younger trees in thinning operations may be required in order to improve spacing and maintain overall stand growth. Furthermore, it is also possible that a vigorously growing stand is not logged at all, but is left until competition starts to slow overall growth.

The forest manager must have information on the forest type, history of disturbance including logging operations, growth stage and current condition of the forest stand in order to plan and manage long-term forest management and actual logging operations.

PRACTICAL EXAMPLES

To demonstrate the Rule in practice, three diagrams are shown overleaf:

1. An unlogged stand,
2. The same stand following logging where the rule has been observed,
3. The same stand after logging where the rule has not been observed.

(B) LOGGED STAND OBEYING THE RULE

(C) LOGGED STAND NOT OBEYING THE RULE

The diagrams show that stand (B) has been logged correctly so as to maintain vigour. Note the following points:

• The advance growth has been thinned from below the canopy, while older trees of the same size have been removed on a single tree selection basis,
• Senescent and mature trees have been removed in such a way so as to create appropriately sized canopy gaps where required.

By contrast, stand (C) has included many small old stems that have been mistaken for young trees and an appropriate canopy gap has not been established. Hence, overall future growth will be diminished or not improved upon.

The Restart Solution:

APPROPRIATE STANDS FOR GAP CREATION

Gap creation is appropriate when almost all the residual trees are dominants and/or are senescent. Removal of these trees will allow rapid growth of seedlings and/or advance growth.

Identifying characteristics:

• Stands where there is little scope for further thinning from below the canopy as the less efficient older/suppressed trees are absent or almost absent,
• Regeneration is sparse, in poor condition or restricted in growth potential,
• There are sufficient large trees to sustain the logging operation.

Gap extension is an appropriate treatment in areas where the immediate commercial prospects are low and where there is currently little suitable regeneration to improve future prospects.

Identifying characteristics:

• An insufficiently regenerated natural gap adjacent to an area of large mature trees,
• An insufficiently regenerated gap caused by previous logging that is adjacent to an area of large mature trees,
• A small clump of large mature trees surrounded by areas with little regrowth.

To allow rapid growth at the centre, canopy gaps should be about 80 metres diameter for tall stands with wide crowns such as blackbutt, blue gum, and tallowwood or brush box. For shorter stand types with narrower crowns, such as spotted gum, gaps should be about 50-60 metres diameter.

CANOPY GAP SHAPE

Canopy gaps should be roughly circular to oval and orientated north south to maximise sunlight. Normally, there should be few right-angle corners.

CANOPY GAP NUMBER

An attempt should be made to establish 2-3 canopy gaps per 5 hectares in the area available for canopy gap logging at each cut (ie. excluding reserves and filter strips and areas more suited to thinning from below). The density of canopy gaps should not exceed about 25% of the logging area for any single logging operation.

Inappropriate Location of Canopy Gaps.

Two outcomes may result from the poor establishment of canopy gaps. They are:
1. Poor Regrowth Response
2. Excessive Disturbance

Poor Regrowth Response This may occur when:
(a) The canopy gaps are too small,
(b) There is insufficient site disturbance,
(c) There has been an inclusion of remnant trees within the gaps.
Greater Disturbance Than Necessary

This may occur when:
(a) The canopy gaps are too large,
(b) The canopy gaps are too frequent,
(c) The areas between the gaps are logged too heavily,
(d) The soil is excessively disturbed and lignotubers have been destroyed.

Updated December 2000