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

The Forestry Commission Yield models for Sitka spruce with a maximum mean annual increment of 14 m3/ha/yr, initially planted at 1.7m spacing provides the following data for average trees within the crop.

Non-thin

Age	Height (m)	spacing (m)	dbh (cm)	vol (m3)	Windspeed to overturn (m/s)	Windspeed to break stem (m/s)
23	10.3	1.96	13	0.06	13.1	13.5
33	15.8	2.21	18	0.16	15.0	14.3
43	20.5	2.54	22	0.33	15.6	14.3

Intermediate thinning

Age	Height (m)	spacing (m)	dbh (cm)	vol (m3)	Windspeed to overturn (m/s)	Windspeed to break stem (m/s)
23	10.3	2.52	14	0.06	13.2	14.2
33	15.8	3.53	22	0.24	13.5	14.2
43	20.5	4.36	29	0.59	13.7	14.4

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a.law@macaulay.ac.uk

Last modified: Thu Aug 21 15:54:30 BST 1997