Pruning Timber Processing I PDF

PRUNING TIMBER PROCESSING I DEFINITION OF PRUNING The removal of live, dead or dying branches from a standing tree with one or more objectives in mind. Cost factor  Expensive operation  Must be justified  Pruned logs sell for higher price Forester Saw miller Primary Rea...

PRUNING TIMBER PROCESSING I DEFINITION OF PRUNING The removal of live, dead or dying branches from a standing tree with one or more objectives in mind. Cost factor  Expensive operation  Must be justified  Pruned logs sell for higher price Forester Saw miller Primary Reasons for Pruning 1. Preventing dead knots 2. Preventing knots Secondary reasons 1. Fire protection 2. Health of compartment 3. Accessibility 4. Higher value timber  Knot influence 1. Greatest factor that influence timber quality/ selling price 2. Reduce strength: Lateral distortion around knot = knot size 3. Harder, denser, more resin, different shrinkage - cracks, bad painting, deviate saws, dull pulping chipper knives, longer chemical digestion in pulp Tight/ live knots  Tight knots will not fall out as the wood dries.  Formed if living branch is overgrown by the main stem of the tree.  Part of the living stem, thus not as hard and weak as dead knots  Tight knots still reduce the strength of the wood but stronger than dead knots  Many different types of knots Loose/Dead knot  Upon drying, such knots can fall out of the wood of which they are a part.  Formed if a dead branch is overgrown by the main stem of the tree.  Branch is simply surrounded by new growth and does not become an integral part of the main stem.  Again, strength reductions related to slope of grain can be significant. Pruning Schedules  Commercial forestry are cost/profit driven. A pruning schedule therefore aims to lay down prescriptions dealing with when and how trees should be pruned for maximum financial gain.  Drawing up pruning schedules requires careful consideration and planning. Correct pruning schedule  Limit knots to the knotty core section in the tree  Form tight knots in stead of loose knots  Be timely so that enough clear timber can accumulate around the knotty core.  Are specific for three specie and growth rate  Not stub the tree growth  Fixed lift pruning Dominant tree Pruning Height Age of tree Height (M) (M) (Years) 3.5 m 1m 3-4 6m 3m 4-6 9m 5m 8-9 12 m 7m 10-12 Typical fixed lift pruning regime 12m 9m 7m 6m 5m 3.5m 3m 1.0m  Diameter pruning regime: P. patula and P. taeda Dominant tree Prune to top Estimated Pruning Height (M) Diameter Height 4m - ½height 7.5 m 10cm/50% of 3-4 m crown 10.5 m 10cm/50% of 5-6 m crown 13.5 m 10cm/50% of 7 m+ crown 14.5 m 10cm/50% of 8 m+ crown 16 m 10cm/50% of 9 m+ crown Diameter Pruning OVER PRUNED Pruning Effects on Trees 1. Over pruning = bark scorch (Patula) 2. Heavy pruning = epicormic shoots (young, HW, P.radiata) 3. Wrong methods can cause cambium damage, bark and resin pockets as well as disease 4. 25% removal of living crown – no grow restriction provided all trees are pruned – 5. 50% removal – temporal effect on diameter but none on height growth 6. 70% removal –reduction on height and diameter growth. Delayed Pruning Knotty core increases Thicker branches ( lower production, higher cost, hard on equipment) 1st pruning is difficult as movement of workers are restrained Branches are heavier and stacking is difficult Heavy branches often causes bark tear Occlusion takes longer (bigger wounds) Cause timber to fall outside specifications More & bigger branches = more competition between trees. Larger knots Lower quality product Correct Pruning Season of Pruning  Trees should be pruned in winter (dormant Season). Summer pruning results in tree stress and opens the door for secondary pests and disease to attack trees  Poor silvicultural practices will contribute to tree stress and contribute to pest and disease attacks.  NATURAL PRUNING (CLADOPTOSIS) 1. A slow process whereby lower branches of the live crown of trees are removed naturally by physical and biotic environmental factors. 2. Lower branches smaller 3. Thicker branches takes longer to drop. 4. Species: More common in eucalyptus than pine 5. In species - fungal activity [temp, RH, resin] 6. Healing determined by stub length and diameter growth rate. Pruning Equipment  Pole pruning saw  Pruning shears  Chainsaws  Sticks  Rich pruning tool  Pruning saw handles  Diameter gauge Pole pruning saws Pruning shears Powered pruning saw Rich Tool Sharp blade severs off branch END