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Growing Confidence in Forestry's Future

Progress with the flagship research programme supported by the Forest Growers Levy Trust, the Growing Confidence in Forestry’s Future or GCFF for short, was presented by Scion researchers at the GCFF conference in Dunedin at the end of March. This ambitious programme aims to double forest productivity, but to do this sustainably so as not to put forestry’s reputation as a sustainable land use and its licence to operate at risk.

A speaker from the US provided a valuable perspective on the use of fertilisers in forestry which have levelled off due to uncertainties over the level of response. The focus now is to optimise the efficiency of fertiliser by targeting fertiliser application to those sites where a response is achieved. The key to optimising fertiliser application is identifying those areas of the forest estate where the trees will respond to fertiliser application. The work also includes understanding where the nitrogen is being stored or lost in the ecosystem. A key to this work is a detailed knowledge of the forest soils.

An important outcome from this programme is the completion of a Stand Density Index. This is allowing forest managers to determine the stocking that optimises value for each site in their forest. Work on a range of sites across New Zealand is showing that optimal stocking increases with an increase in 300 Index with optimal stockings ranging from 250 to 700 stems per hectare. On average across New Zealand, structural stands are about 100 stems per ha below the optimal which is equivalent to a net value loss per hectare of $2,500 at harvest. If stands were increased to the optimal stocking, a $2,500 per hectare value increase applied across the national structural estate results in a net value gain of $150 million in NPV terms. This is value that could be added to forest valuations.

New research in the nursery to improve seedling quality and performance in the forest was outlined. The role of mycorrhiza and other soil biota in tree nurseries is well known but the impact of fungicides on these is less understood. An important result from this work is that reducing fungicide applications in the nursery is resulting in improved growth and seedling quality. As a result of this promising work 46 new trials are being established to test the responses of reduced fungicide and different fertiliser treatments.

Remote sensing is showing rapid update in the primary sector and forestry is well suited to this technology. To the forest manager however it is often confusing as to what is the appropriate technology. From the work to date we are now able to say that Airborne LiDAR scanning can detect individual trees, delineate tree crown and shape, and measure tree heights. It is also best for delineation of ground features and for engineering planning. Terrestrial LiDAR scanning is best suited to assessing tree location, diameter and form with Multispectral Imagery showing most promise for disease detection. To date assessment of wood quality from remote sensing has not been successful with assessment of cores or disks still the best way of assessing wood quality.

What is not often appreciated is the value of the national Permanent Sample Plot system to forestry research. Much of the work in this programme that is delivering value to forest owners today is based on data from trials established by previous researchers and forest managers. Containing data from over 100 years, 145 species and 32,000 records this is a data base of national significance that must be protected and removed from the vagaries of short term research funding.