Silvicultural advice for reducing the risk of wind damage

Two scenarios can be tested:

• non-thinning of stands
• thinning of stands at the marginal thinning intensity

Note data calculated from FC Yield models and usersnap.exe

Non-thin

Intermediate thinning

Discussion

- by R. Dunham

For both the peaty gley and the podzol, the changes in stocking density associated with thinning result in the thinned trees requiring a lower wind speed for damage to occur than for the unthinned trees (and are therefore more likely to be damaged). This agrees with the idea that thinning results in an increased risk of damage.

The trees growing on podzols generally require greater wind speeds to overturn them than similar trees growing on peaty gleys. Again this agrees with the FC's windthrow hazard classification, that forests on peaty gleys are more susceptible to damage than forests on podzols. Note however that the wind speed needed to break the trees is unaffected by soil type.

Furthermore the wind speed needed to break trees is generally less for unthinned than for thinned trees

As a consequence, the unthinned trees on podzols require a lower windspeed to break them than to overturn them. They are therefore at high risk of stem breakage. This suggests that while non-thinning may reduce the risk of overturning, if high windspeeds do occur then stem breajage may occur.

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Last modified: Thu Aug 21 16:08:22 BST 1997