New Zealand Journal of Forestry (2001) 46(3): 23–29
©New Zealand Institute of Forestry
The effects of a crown lightening technique on growth and form, and topple in two-year-old Pinus radiata.
Colley, P. Davies and J. Turner
Christchurch, New Zealand: New Zealand Institute of Forestry.
Toppling is recognised as an increasing problem in Pinus radiata plantations, particularly on fertile farm sites. Toppling can be costly to forest and woodlot owners due to the loss of value of the final crop, arising from poor stem form, and reduced selection ratios. Crown lightening, the reduction of a tree's "sail area" by shortening branches, is one method being applied to reduce the likelihood of topple. In June 1996 a trial was installed near Whangarei, New Zealand, to assess the effects of a crown lightening technique called "windproofing" on the growth, form and topple of two-year-old radiata pine. Two days following trial installation the trial was subjected to a storm event with high rainfall and winds gusting to 95 km/h. Assessment of the trial two years after installation shows no affect of windproofing on height or diameter. No windproofed trees toppled, while 50% of control trees toppled. The difference in topple resulted in better stem straightness in the windproofed trees. The relatively low cost of applying windproofing, no significant loss of growth, and the reduced chance of topple, suggest that windproofing is a useful tool for forest managers to increase the likelihood of achieving a high value tree crop at rotation end.