When done, the benefits of thinning for an owner are
- The correct management of the crop
- Tax-free revenue from timber sales
- Increase in asset value of the remaining crop
- Remaining trees increase in volume faster which allows clear felling to be completed as quickly as possible
Not thinning will result in a larger number of smaller sized trees per hectare with a significantly reduced value on clearfelling.
Planning for Thinning
Planning for first thinning should start when the crop is 10 years old. Inspection paths need to be cut to permit access to the crop to determine its productivity and its projected first thin year. Cutting an inspection path or ‘brashing’ involves removing the branches to head height between two lines of trees.
Forest roads need to be planned and a General Felling Licence applied for.
General Felling License
Tree felling is controlled through the 1946 forestry Act. Before an owner can thin a plantation a general felling license must be secured from the Forest Service of the Department of Agriculture. Forestry Services ltd. Ltd applies for these licenses on behalf of the owner. This license specifies how the thinning is to be completed, and any environmental conditions that must be adhered to.
Types of Thinning
There are many types of thinning, with the most common one being what is normally referred to as 1 in 7 plus selection. This means 1 in every 7 lines of trees is completely removed to facilitate access with inferior quality trees selected for removal in the intermittent lines. This is normally completed mechanically with motor manual (chainsaw operator) employed only on specific stands.
Mechanical thinning uses specialised harvesting heads, which are fitted to purpose built harvesters of standard excavators. The timber is then removed to the roadside by a forwarder, which is a specialised forest machine.