forest silvicultural options
Most discussions about silviculture methods
in native forests concentrate on harvesting options. Broadly
speaking there is a range of options from individual tree selection
through to total clearcutting. Harvesting option choices will
be influenced by practical and economic considerations. But
the environmental effects of each option are most important
for achieving successful regeneration, and minimising the effect
on other environmental, social and economic values.
In Ross Florences book Ecology
and Silviculture of Eucalypt Forests, the
effect of native forest harvesting on regeneration is shown
in a graph from Smith (1962). The graph shows the relationship
between the percentage of the tree canopy removed and the environmental
factors that are likely to influence regeneration. Depending
on the species mix that the landowner wishes to, or must, regenerate,
it is possible to define an appropriate harvesting intensity
that ensures sufficient seed for regeneration and provides an
environment that supports vigorous growth.
This graph illustrates some of the
environmental effects of different silvicultural systemsincluding
clearfelling, clearfelling with seed trees, shelterwood, selection.
From Smith, D.M. (1962) The Practice of Silviculture, 7th edition.
John Wiley & Sons, New York
An immature forest can be managed for timber
production through selective thinning, either for commercial
return or as a culling to waste, and possibly pruning. Thought
should also be given to the management of exotic weeds, fire
protection and vermin. Selective thinning can:
reduce competition between trees
encourage diameter growth
increase light levels for the understorey and can be
an important means of increasing understorey diversity
encourage regeneration of shade tolerant species
contribute to economic production from grazing or harvesting
non-timber products such as flowers or bush foods.
Thinning can be done using a chainsaw, brush cutter or by stem
injection of herbicide.
Landowners are encouraged to find out what
permits, if any, are required, before undertaking native forest
silvicultural operations. It is also important to thoroughly
assess the forest before developing a management plan. This
might include assessing the:
tree and understorey species, and their size and distribution
* seed loads held in the canopies
* wildlife species present
* soil erosion hazards.
Developing an understanding of a forests ecology and dynamics
of the forest is important for developing effective management
options. It can also greatly enhance the owners appreciation
and enjoyment of their forest.
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