Impacts of tending on attributes of radiata pine trees and stands in New Zealand – a review

Abstract

Background: Radiata pine (Pinus radiata D.Don) has been grown in New Zealand’s plantations for more than a century, and silviculturists began by employing Eurocentric ideas about how to manage forest stands. Research and development gradually led to an entirely new approach to silviculture, where volume production was sacrificed to promote value, and high investments in individual trees led to very low stand stockings by international standards. Methods: The development of pruning and thinning technology was reviewed, highlighting the most important developments, and identifying impacts of tending on tree and stand attributes. Results: Decision-support systems for planning pruning and heavy, early pre-commercial (waste) thinning became very sophisticated. As ideas changed, however, structural regimes without pruning became more prevalent, and this has necessitated new forms of silvicultural research. Ideas for new areas of tending research in New Zealand are outlined. Conclusions: A unique approach to tending plantations developed in New Zealand that involves sacrificing volume production to increase the value of an investment in pruned forest stands. Experiments aimed at building decision-support systems for these silvicultural regimes have yielded a great deal of information about impacts of pruning and thinning in stands with relatively open canopies. Recent changes in focus towards growing construction lumber require a greater research focus on factors influencing wood stiffness and stability as well as a clear understanding of the use of higher stocking levels with a variety of genotypes on a range of sites. Stand dynamics and mortality will be more relevant than for pruning regimes, and a variety of new experiments is required.