Know when your forest is ready for its first thinning
Proper and timely action can have a huge impact on the overall profitability of your plantation
Many farm forests are at, or rapidly approaching, the stage of first thinning and it is necessary to plan for this important operation in a methodical way. In most situations, proper and timely thinning results in a significant increase in the value to be realised from a timber crop later in the rotation, both from subsequent thinnings and final harvest.
The first thing to appreciate is that a forest cannot be accurately assessed from the boundary, so once the canopy has closed and the trees are 7m to 8m in height inspection paths must be created to allow access. Paths should be brashed to about 2m in height, ideally about 100m apart and interconnected.
This operation is frequently overlooked, but it is essential as it is the only way to 'see the wood from the trees' from within and thus enable planning and timing of operations. It allows purchasers to assess the crop and formulate a fair offer that reflects the value of the timber to be harvested. Once this is done, the owner can establish whether his forest is suitable for thinning and whether it is ready.
In some circumstances where the risks outweigh the advantages, thinning is inadvisable.
This is particularly the case on sites where there is a high risk of windthrow, poor drainage or persistent water logging, or where thinning has been delayed and the stand has grown beyond "critical height".
If in doubt, seek professional advice. Assuming none of these apply, the three most important factors which indicate whether a stand is ready to thin are stocking density, diameter at breast height (dbh), and top height.
An Irish thinning protocol is available as a free download from the Irish Timber Growers Association website. This provides a step-by-step guide to thinning systems in Ireland, and should be considered essential reading for any owner contemplating it.