Variations in the dynamic modulus of elasticity with proximity to the stand edge in radiata pine stands on the Canterbury Plains, New Zealand
To explore the effects of wind on tree form and wood quality, 30 transects were placed across each of three relatively narrow stands of Pinus radiata, aged 11, 17 and 25 years old, on the Canterbury Plains, New Zealand. The experimental design assumed that the major influence on stand edges to be the prevailing strong north-westerly winds that blow across this region. Outerwood dynamic modulus of elasticity (Ed) and tree height increased with distance from the stand edge, while taper reduced. The negative effect of wind extended into the stand the equivalent of one tree height, regardless of the age of the stand, with the least stiff trees (i.e., those with the lowest Ed) located at the stand edge. Surprisingly, larger effects were observed at the downwind edge of these stands, although the reasons for this are not clear. Results from this study indicate that for those stands investigated trees located at the stand edge, or within a distance equivalent to one tree height from the edge, may be of marginal value for structural timber.