Managing Wood Quality / Pruning

Tending and objectives

TENDING
Any operation carried out for the benefit of a forest crop or of individual trees at any stage of their life, except regeneration felling and site preparation.

GENERAL TENDING OBJECTIVE
To produce as much as possible of the desired product at as low a cost as possible (with products and costs interpreted in the context of sustainable forest management).

Exterior wood quality indicators

Forking height: below 6 metres indicates poor quality
Lower live branches: presence indicates poor quality
Spiral grain: (indicated by bark characteristics) indicates poor quality
Transverse bending: indicates poor quality
Tree tilt / bend: indicates poor quality if very pronounced
Epicormic branches: indicate poor quality

High quality wood characteristics

Regular spatial distribution of crop trees
Vertical stem (no tilting)
Straight stem (no bending)
High natural pruning
Flat branches (steep angles undesirable)
No epicormic branches
No or little transverse bending (sinuosity)
No or little spiral grain
No damage or rot in the stem

Optimal stem for industry

TARGET DIAMETER = 70 cm
10 cm knotty core
5 cm occlusion
40 cm clear wood
10 cm sapwood
5 cm bark and irregularities

Fast HQT production

THE TWO-PHASE CONCEPT:
Narrow spacing followed by heavy thinning, with or without high pruning

THE OPEN-GROWN TREE CONCEPT:
Wide spacing and early high pruning followed by heavy thinning

Stand-based approach vs. single-tree approach
Rate of return diminishes with time: produce as fast as possible

Managing wood quality

Choice of provenance
Natural pruning
Formative pruning (height = 1-3 metres)
High pruning (height = 3-7 metres)
Pruning of epicormic branches (height = 3-7 metres)
Marking of potential final crop trees

Matching provenance to the site

NO TRANSFER:
From high to low elevation
From maritime to continental climate
From uniform climate to variable climate (drought, frost, etc.)
From basic soil to acidic soil or vice versa

Natural pruning

Natural pruning can be modified only through choice of genetic origin and stand density management

Formative pruning

Objective: to produce a single straight stem
Target: young trees up to 3 m tall
Result: doubtful
LESS THAN 5 branches in one go

Transitional combined pruning

Prune steep-angled branch in crown
Prune tip of branch to reduce competition with terminal leader
Pruning of thick branches and bottom-up pruning

High pruning

Objective: to produce high-quality hardwood timber
Target: young trees over 3-6 m tall, but less than 10-15 cm thick
Number of trees: 2 x no. of final crop trees
Prune only young and 'good' trees
Best time for high pruning = during growing season or when you have time

Pruning of epicormics

To a height of 7 metres
On a continuous basis at regular intervals
For pedunculate oak this is needed to reach optimal value (added value +2-2.5%)
For sycamore you need to prune so lightly and frequently that epicormics don't develop

Potential final crop trees

Concentrate silviculture on the commercially most valuable trees to optimize and safeguard an investment leading towards the production of high-quality timber

Consider minor species ('admixed / niche species')

Similar principles may be applied to other types of potential crop trees, for example trees of special value due to cultural heritage, spiritual issues, aesthetics, forest recreation or biodiversity

Improve only what is already good or superior in health, growth, quality (except branches) - or other relevant characteristics