First thinning is make-or-break time for forests so it pays to prepare with care

William Merivale

February 19 2013 04:01 AM

Good management requires knowledge. The amount of knowledge available to a manager has a direct bearing on the quality of management that is possible allowing, as it does, for informed decision-making.

A fundamental requirement to successful business management is knowing the extent of the assets both owned by and available to the owner or manager.

"You can't see the wood for the trees," is a particularly apt phrase with regard to forest management, especially so in the case of young plantations in the pre-thinning stage. Once a plantation closes canopy, access becomes increasingly difficult and, without access, it is impossible to assess how the trees are faring with any degree of accuracy.

Only a small fraction of a typical plantation of say 10ha or 15ha is visible from the boundaries, ridelines and internal roads. And, in any event, the woodland edges do not give an accurate picture of what lies within. An intensive network of inspection paths brashed through the forest helps, indeed is essential, but even then it is still impossible to see everything.

Matters improve after the first thinning. A first thinning of spruce will usually entail the complete removal of rows of trees at regular intervals, referred to as 'racks', with a light selective thinning of a number of stems between the racks.

One row in seven is the usual prescription, leaving blocks of six rows between the racks and a 12m wide rack.

The harvester can then travel the rack and reach in three rows on either side to carry out selective thinning.

It is unusual these days to mark a first thinning. Marking involves identifying the stems to be removed either by cutting a blaze on the tree or spraying with paint. It is quite a labour intensive and therefore expensive job.

However, some degree of measurement should be carried out prior to first thinning. This will establish if the plantation is indeed ready to thin, and help to determine the thinning intensity – in other words, the volume to be removed.

Once these factors have been determined, a good contractor will know what to do. But, regardless how competent the contractor, any thinning should be supervised.

With the rise in the number of private forests now at the first thinning stage, the number of horror stories of cowboy contractors is also inevitably on the rise and no owner should forget that a first thinning can make or break his forest.

Do the research, only engage a contractor who comes well recommended, and preferably one with an interest in a long-term relationship.

A contractor who knows he stands a good chance of being engaged again to carry out subsequent thinnings will have the perfect incentive to get the first one right.

Once the first thinning has been completed, you can begin to see the wood for the trees and this is the ideal time to start preparing a detailed inventory.

This brings us back to my first point – good management requires knowledge and it is impossible to manage a forest well without knowing in some detail what's in it.

EMPHASIS

An inventory is an essential component of the woodland management plan, and as trees have the rather useful attribute of continuing to grow in value as well as size, the inventory should be updated reasonably regularly.

Over time, the emphasis with many of our even, aged and predominantly spruce plantations will be to convert them to more uneven, aged forests with greater species diversity, and inventories will become an increasingly important part of management planning.