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.

Tree root research in New Zealand: a retrospective ‘review’ with emphasis on soil reinforcement for soil conservation and wind firmness

“…Mason & Cullen (1986) found that soil ripping, with or without soil mounding, reduced toppling incidence. Trees planted on ripped sites had better root form and vertical root growth than trees growing on unripped sites (Mason et al 1988). Similarly, Somerville (1979) found that the vertical distribution and form of roots of 11.5-year-old radiata pine trees were improved by ripping-even though the amount of below-ground biomass remained relatively unaffected by this treatment.…”

“…New Zealand studies have ranged from descriptive, including photographing or drawing of root systems (e.g., Watson & O'Loughlin 1985, Ross et al 2004 ), to the development of more systematic assessments and indices (e.g., Somerville 1979;Balneaves & de la Mare 1989). Reported New Zealand root morphology indices (Balneaves & de la Mare 1989;Mason 1985) are generally subjective and have been used to compare tree performance following different plant establishment treatments such as soil ripping. They tend to focus on an appraisal of taproot distortion, lateral root arrangement, and root tangle.…”

“…New Zealand research has tended to focus on the toppling of young plantation stands of radiata pine less than six years of age or between 1 and 3 m in height (see Moore et al 2008). A permanent lean of ≥ 15° in juvenile radiata pine is likely to result in some degree of stem distortion at maturity (Mason 1985;Watson & Tombleson 2002) which affects the future value of the tree. Watson & Tombleson (2004) summarised the tree root growth responses to wind exposure in New Zealand.…”

Lessons from insect and disease impacts on radiata pine (Pinus radiataD. Don) plantations in New Zealand over the last hundred years

“…With alternative tree species, the most relevant costs are opportunity costs in profitability relative to that of growing radiata pine. Because of lower productivity, or need for longer rotations, or much greater sensitivity to site variation, and often problems of utilisation and marketing their wood, alternative species are typically far less profitable to grow than radiata pine (Maclaren 2005 3 ). Site sensitivity can effectively reduce a species' wide use, often making them more suited to small growers of speciality woods.…”

“… 3 Maclaren 2005 looks at optimum situation, but this is less common with alternative species than radiata pine.…”