“Knowledge is of two kinds. We know a subject ourselves, or we know where we can find information on it.” — Samuel Johnson
In our earlier post, Stand Tending 101: Spacing and Pruning (Part I), we shared a video and some highlights from a recent trip to Sidney Island where we caught up with Paul Nimmon and his silviculture crew carrying out a juvenile spacing and tree pruning operation.
As follow up, we’ve included information from our favourite resource, Managing Your Woodland: A Non-forester’s Guide to Small-scale Forestry in British Columbia, to help consider how you might apply these treatments to your own woodland.
What Is Thinning and Spacing Anyway?
Spacing and thinning treatments change the characteristics of your stand by reducing the number of stems per hectare. Generally, these treatments are used to:
- Focus the growing potential of the site on the trees most capable of responding (your crop trees).
- Modify species composition.
- Remove undesirable species, damaged or diseased trees.
- Create stand conditions (light levels) that favor certain understorey species for forage for wildlife, livestock or botanical forest products.
Thinning treatments are carried out at different stages in the development of a stand.
The first thinning treatment is usually called juvenile spacing since it removes very young stems. It’s also referred to as pre-commercial thinning since the stems removed are traditionally too small to be sold as a commercial crop.
Commercial thinning happens later in the life of the stand, and removes stems large enough to be sold as commercial products such as firewood, pulp logs, small sawlogs, and small veneer logs.
The Benefits of Thinning
The volume of wood capable of being produced in any given stand is fairly constant, based on the capability of the site to produce particular species of trees. When you remove some trees, the resources of the site are channeled onto the remaining trees.
This has two advantages:
- Enables preferred trees to ‘capture’ the growth potential that would otherwise be ‘wasted’ on trees that will eventually die from overcrowding.
- Accelerates the natural process of stand development and enables you to produce your future crop trees to a merchantable harvest size in a much shorter time period.
Some benefits achieved by juvenile spacing and other thinning treatments include:
- Shortening crop rotation by speeding up growth of higher value, larger diameter crop trees.
- Interim, mid-crop-rotation timber harvest revenue.
- Increasing merchantable volume by concentrating growth on fewer stems.
- Producing more favourable end-products by controlling the species and stem form.
- Reducing losses to windthrow and snowpress by increasing individual stem stability.
- Improving the overall health of the stand and protecting it from disease and insects by the selective removal of diseased or defective stems.
- Reducing future logging costs by creating a more uniform and larger piece size.
- Improving stand-level aesthetics and minimizing landscape-level visual quality impacts of timber harvesting.
Planning for Juvenile Spacing
Assuming your stand is adequately stocked, by the time your trees are between 3 and 5 metres in height, their crowns and root systems will usually start to crowd each other out as the crowns of neighbouring trees touch and start to block the entry of sunlight to the forest floor.
If light below the main canopy is blocked out, the foliage on lower branches begins to die, and the live crown appears to ‘shrink’ and recede up the tree. If left, this situation will result in a slowdown in growth.
The purpose of juvenile spacing is to organize the growing space in your stand by removing unwanted or excess stems. It creates growing room for those species most capable of productive growth. The selection of stands for juvenile spacing and the timing of treatment will depend on the characteristics of the stand and your management objectives.
In general, juvenile spacing supports many management objectives by:
- Improving access for both people and wildlife.
- Enhancing stand vigour.
- Reducing hazards related to fire and pests over the life of the stand.
It’s worth drawing your attention to Harold Macy’s comment on our earlier post. Harold reminds us:
“While stand tending treatments such as the juvenile spacing referenced in this article will accelerate growth and consolidate volume on less stems per hectare, you will not necessarily end up with more volume through recovery of imminent mortality as once thought. At our recent BC Woodlot Federation AGM in Campbell River, Rick Monchak of TimberWest gave a very good tour illustrating this point.”