Updated: 01 December 2008
Final report [PDF 4.3MB] and appendices [PDF 7.9MB]
Over the past 50 years the New Zealand forestry industry has become increasingly dependent on structural and industrial timber in general and radiata pine timber in particular. Although plantings of Douglas-fir and various species of Eucalyptus experienced an encouraging increase through the 1990s, the structure of the New Zealand forestry estate still lacks diversity. This dependence on a narrow range of species increases the industry's exposure to risk at a time when our competitive advantage in forest growing is reducing. This lack of estate diversity also increases the biological risk and reduces future market and economic flexibility. It also reduces regional development and sustainable land management options and increases social risks associated with the public perception of forests as largely unattractive producers of ‘industrial' products with few other redeeming features.
Our strategy in the past has been to grow a species that has a broad range of uses. Expanding the range of species in the estate to include species that have a high international reputation, strong market appeal and high value places the country in a better market position. A particular opportunity exists for higher value finishing timber. Historically New Zealand's finishing timbers were supplied by its indigenous forests. More recently the decline in the availability of native timbers has been met by the importation of timbers often sourced from unsustainable forests in Southeast Asia. However, a significant reason for the continued dominance by radiata pine has been because of the inferior performance of other species.
In the late 1950s Gilmore recognised that the poor growth of Douglas fir was due to a lack of mycorrhizal fungi—an intimate and obligate association between plant roots and specially adapted fungi that assist in the uptake of plant nutrients. So important is this relationship that all trees are dependent on mycorrhizal fungi (http://users.sunbeach.net/users/lec/types.html; http://www.ffp.csiro.au/research/mycorrhiza/intro.html). Many other alternative species struggle in New Zealand when compared to their successful performance overseas and it is possible that this too is due to the absence of suitable mycorrhizal fungi on their roots. It is, therefore, essential to ensure that alternative forest trees are infected with effective mycorrhizal fungi in the nursery (http://www.trufflesandmushrooms.co.nz/page3.html).
Spontaneous mycorrhizal infections that are formed by mycorrhizal fungi resident in a bare rooted nursery or spores that might blow into a greenhouse through vents and doors cannot be relied upon to ensure adequate mycorrhizal formation. This is particularly important with plants raised in containers where the soilless potting mixes used are invariably devoid of mycorrhizal fungi. In some instances a lack of understanding of the mycorrhizal relationship has led to plantation failure. Some nurserymen compensate for a lack of mycorrhizal fungi on their plants and make them look healthy simply by applying large amounts of nutrients and fungicides with problems arising after outplanting.
We believe that the opportunities for improving New Zealand's competitive advantage provided by diversifying the forest estate could be unlocked by the careful management of mycorrhizas in nurseries. Possible outcomes include:
The choice of tree species will be based on market appeal and unexpected poor performance after outplanting. Techniques will then be devised to successfully infect them with appropriate mycorrhizal fungi either in the greenhouse or bare root nursery followed by field trials to compare plants inoculated with specific mycorrhizal fungi with those produced using standard nursery practices. The introduction of mycorrhizal infection certification for novel forest species may also help increase grower confidence. Additional background information can be found here [PDF 1.25MB]