Control your Harvest and Sale

When harvesting operations begin, it is essential that you or your forester carefully monitor progress and ensure all procedures that were pre-agreed are being followed. This involves supervising thinning and clearfell operations, keeping track of timber harvested and getting paid for your timber.

While the clearfell harvest is relatively straightforward; thinning requires careful management to ensure the future development of your forest.

• Over-thinning may give some short-term financial gain, but it can result in serious long-term devaluation of the crop.
• Under-thinning does not sufficiently allow your forest to develop to its full potential.

Thinning control protects your forest in the long term by ensuring that thinning is carried out to the recommended prescription and that the correct intensity, volume and type of trees are removed.

Thinning prescription

An experienced forester can prescribe an appropriate thinning prescription based on the information gathered in the forest inventory.

For example in first thinning, the prescription might be to remove one third of trees with the aim of increasing the mean Diameter at Breast Height (DBH) of the remaining trees by 1cm - 2cm. In second and subsequent thinnings, a forester can recommend a thinning prescription based either on basal area or marginal thinning intensity.

Thinning control

In first thinning, the value of the thinnings removed is low. Simple thinning control systems are used (see table below):

• Method 1 - examine the size of the cut stumps. If there are a lot of large cut stumps with small trees left growing beside them (excluding the removed lines), you should ask questions about the size of the trees being cut.
• Method 2 - measure the average DBH. In general, you would expect the average DBH of the remaining trees to be about 1 - 2cm greater after thinning than before thinning.

In second and subsequent thinnings, the accuracy of thinning control becomes more important to reflect the increase in timber value.

Before thinning begins, an estimate of the volume to be removed or intensity is calculated by laying down a series of thinning control plots throughout the forest. In these plots, the trees to be removed are marked and measured. Information from the plots should be used during thinning as a reference to the number of trees and volume to be removed.

Ideally, all trees to be removed in the stand (in second and subsequent thinnings) should be marked. In doing so, it will ensure that the correct volume (and trees) to be removed is controlled. This may appear as an extra expense but it more than pays for itself in the long run when you consider:

• it helps to ensure the removal of only appropriate trees
• it may reduce the length of the rotation
• it can increase the stability of the forest
• it can speed up the felling process, when the decision of which tree to remove is taken from the harvester operator
• a good volume estimate and assortments are known before harvesting commences

If trees for removal are not marked, the decision of selecting trees for removal is left to the harvester operator. In this case, random plots should be taken by your forester to compare actual volume removed with that prescribed in the thinning control plots. Where over-thinning or under-thinning is identified, corrective action should be taken.

A clearfell harvesting is relatively straight forward. A forester should carry out an inventory to include the number of trees/ha, the average harvesting volume/tree, the volume/ha, and indication of product assortments (% pulp, pallet and sawlog) and an assessment of tree quality. This will provide valuable information when advertising the sale. It is important to be aware that on some sites not all trees cut will be extracted to the roadside. A small number may be left in the forest – used as bridges to cross drains, build up soft areas etc.

Ideally, these trees should be removed in the final extraction operations.

Harvester head printout

Real-time information on the volume of timber being harvested is a useful way to monitor progress. All modern harvesting machines can provide a print-out of the volume and categories of timber cut. The information is generated through length and diameter readings of the trees as they are processed through the harvester head. This is valuable information. Regular print-outs or screen shots of the harvester’s computer screen will show how much volume and what categories of timber (pulp, stake, pallet or sawlog) have been cut. These records will show if the correct size and number of trees are being cut and should be retained to compare against the final harvest outcome.

Stack measurement

Timber stacks can be measured by the forest owner or forester at roadside. It is a useful way to estimate the volume of different timber products. It involves measuring the length and width (i.e. log length) of the stack and getting the average height of the stack. These measurements are multiplied together; (l x w x h). A correction factor is then used to take in to account the air spaces within the stack resulting in solid stack volume. 0.7 is the most commonly used conversion factor in the forest industry. However this correction factor can be calculated for individual stacks.

A guide to timber stack measurement is available here:

• Timber Stack Measurement (PDF)

Weight versus volume

Timber is generally sold by weight (tonnes) or by volume (cubic metres, m³). When comparing weight and volume measurements, it is important to understand that the weight of timber can change but the volume of timber generally remains the same.

The weight of timber can vary considerably depending on a number of factors such as tree species, the length of time at roadside, log size and the weather conditions. Timber begins to dry out as soon as it is felled. The longer timber is left sitting roadside, the more moisture it loses and the lighter it becomes. This should be taken into consideration where timber is sold by weight (tonnes), as this may result in a loss of income to the owner. The converse is true if timber is going for wood energy as it is sold based on a low moisture content. 

To avoid loss of income, the owner should insist, through the timber sales contract, that the logs are moved immediately after harvest or by a specified date (usually within 15 days of felling) to the weighbridge. If the logs are not removed by the specified date, the agreed price per tonne should be increased by e.g. 3% for the logs for every additional seven days or part thereof that the timber remains on site.

All sawmills also provide a system where timber is measured by volume. Timber arriving at the mill is converted from weight to volume using a correction factor. It takes into account the weight loss post-harvest. This system is used by some of the larger timber suppliers and may also be available to private growers.

Timber security

Harvested timber is a valuable commodity and as such should be protected. There are a number of precautions an owner can take to reduce the risk of theft:

• operate a forest docket system
• install a gate or barrier at the entrance to the forest to regulate access
• erect temporary cameras (in accordance with data protection legislation)
• take regular photos of stacks to monitor roadside stocks
• assign an individual to supervise harvesting/delivery to market

Forest docket system

Having an appropriate system in place will help in accounting for all timber removed from the forest and to improve timber security. The ITGA Model Timber Sales Dispatch System (external PDF) provides a widely accepted template for managing timber sales in private forests. 

The following is a brief summary of the docket dispatch system:

• the vendor (owner or agent) gives a standardised forest docket book to the purchaser. These dockets are available from the ITGA.
• the vendor is notified before every entry into the forest. This notification contains agreed information and is texted by the haulier at least one hour before arrival.
• on receipt of the text, a unique permit number is texted back to the haulier.
• entry to the forest is only allowed during agreed times.

Normally a deposit is paid to secure the purchase and payment instalments are made at intervals. As harvesting progresses and logs are extracted to roadside, the owner and forester should ensure that the agreed payment schedule is strictly adhered to.

It is important for the owner to retain control of the timber on the site until payments are made in accordance with the contract.

Post-harvest sign-off

It is very important that the harvest site is left in good condition when harvesting is completed. Details of owners’ requirements should be outlined in the contract. These may include road repairs, replacing damaged culverts, clearing and repairing drains, cleaning sediment traps, correctly disposing of hazardous material, debris, litter and removing log bridges and other temporary structures.