Central North Island wood availability forecasts for the period 2008–2040

Data

Method used to obtain forest areas
Method to develop yield tables
Large-scale owners’ harvest intentions

Method used to obtain forest areas

Forest areas by croptype were obtained from the NEFD as at 1 April 2006. The following reductions in area were made:

6000 hectares in young age-classes was removed to allow for deforestation of young stands between 1 April 2006 and 31 December 2007.
The small-scale owners’ forest areas (apart from that of the investment syndicates and other professionally managed forests) were reduced by 15 percent. This was done because the area in this ownership category is often reported on the basis of gross area rather than net stocked area.

In addition some minor changes in croptyping were made based on information received from forest owners. For instance one large-scale owner noted that it assigns all replanted area to the NEFD minimum tending – without production thinning – croptype and reallocates to other croptypes once tending has been done.

Method to develop yield tables

In 2007 new yield tables for the Central North Island were developed in the following manner:

large-scale owners provided yield tables for their estate;
these were averaged on an area-weighted basis to get regional yield tables for each croptype;
yield tables for old (age 16+ years, planted in 1989 and earlier) radiata pine and Douglas-fir were then calibrated to match the harvest intentions data provided by large-scale owners; that is, the assumption is that the harvest intentions data is the most accurate information available as it is based predominantly on detailed inventory;
yield tables for young radiata pine croptypes (planted in 1990 and later) were also adjusted using the same percentage adjustments used for older stands;
the yield tables developed for the large-scale owners’ estate were also applied to the small-scale owners’ estate.

Large-scale owners’ harvest intentions

Large-scale owners were asked to provide details of planned harvest volume by log grade and area from 2006 to 2015. These harvest intention values were then included at the beginning of the forecasts to provide the most realistic wood availability forecasts over this period.

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