AAIR Project No PL 94-2392

Encourage the development of deep, wide, symmetrical root plates

Roots will not cross deep plough furrows. This results in restricted root plates.

• Patch scarifying, mounding or complete cultivation are preferential to spaced furrow ploughing
• On mineral gleys and peaty gleys, moling either alone or in addition to other cultivation is beneficial
• If spaced furrow ploughing is used on gleys or deep peats then it should be as shallow as possible

Plough pans, iron pans and indurated layers restrict the depth of rooting

• Disrupt these if economically viable

Waterlogging kills roots and reduces the mechanical strength of the soil

• Drains should be created at an appropriate spacing

Assymetric root systems are less stable than symmetric root systems

• Roots should be well distributed around the planting spot at the time of planting. This is especially important in species which do not produce adventitous roots (e.g.pines, larches and Douglas fir)

Plan spacing, respacing and thinning carefully

Wide spacing leads to the development of large crowns and trees being subjected to high wind loads.
At the same time it also leads to the trees being relatively large, tapered, and on sites without restrictions it will lead to the develoment of large root systems, resulting in trees which are well designed to withstand such loads.

• initial spacing within the range 1500 to 3000 trees/ha has little clear effect on stability.

Thinning results in higher wind speeds within the canopy leading to greater wind loads, reduces the amount of crown damping, but ultimately results in larger trees which can adapt to their greater wind loads.

• avoid delayed, heavy or uneven thinning
• minimise damage to roots and soil by the use of brash mats and appropriate machines
• thin the most vulnerable stands in spring, allowing them a whole growing season to adapt before the probable occurrance of the next strong winds
• do not thin the upwind edges of vulnerable stands, thereby reducing wind penetration into the stand
• self thinning mixtures allow the silvicultural benefits of thinning to be obtained, while having only a gradual effect on wind loads

Plan felling sensibly

Wind damage is often severe at the margins of felling coupes, due to high wind speeds and trees which have not adapted to the associated loads.

• fell coupes to natural or established edges
• within a coupe start felling at the downwind edge, and progress windward
• create long term stable edges on deeply rootable soils.
• use severance cuts to expose new edges during a period of negligible or low risk
• do not create concave sections which will exacerbate the topographic funneling effect of the wind
• minimise the length of new edge required

Edges result in turbulence which can cause damage several tree heights downwind. Options for reducing turbulence are:

• 
  
• have a ramped edge to the forest by initially planting slower growing species of broadleaf or conifer, or by topping existing trees
• increase the spacing of the edge trees to increase wind permeability
• high prune the dge trees to increase wind permeability

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Last modified: Mon Aug 25 11:32:32 BST 1997