Wind effects on juvenile trees: a review with special reference to toppling of radiata pine growing in New Zealand

摘要

Toppling, or the windthrow, of young (2–3 years of age) trees is a problem in some regions of the world, including New Zealand. In that country, the incidence of toppling of young radiata pine (Pinus radiata D. Don) trees is a concern to foresters. Toppling differs from wind damage in older forests as trees are not blown completely over, but instead attain a lean; a tree is said to have toppled when this lean exceeds 15° from vertical. Impacts of toppling include a higher incidence of stems with basal sweep and reduced selection choice at the time of pruning and thinning. When trees from toppled stands are harvested, basal sweep results in reduced yields of clearwood and increased levels of compression wood in sawn timber. This paper discusses the phenomenon of toppling and presents an overview of research that has been carried out to identify key causal factors and evaluate treatments which reduce this risk. Due to confounding influences, it is often difficult to experimentally determine those factors responsible. Therefore, a mechanistic model is proposed, which aims to predict the probability that a tree will topple, as well as allowing the effect of different management actions to be evaluated.