National forest owner survey and resource inventory of alternative species
By Vega Xu and Bruce Manley, January 2023.
Download SWP-T159 (pdf)
Stage 3: Mapping alternative species in East Coast
This study used a remote sensing approach to classify alternative species of small-scale plantations in the East Coast wood supply region (i.e. Gisborne District). With additional truthing data, the approach achieved 92.9% overall classification accuracy. Douglas-fir and Eucalyptus were the two most accurately classified alternative species categories, with producer’s accuracies of 97.2 and 94.0% respectively. The most important input variable selected for the classification was DEM (Digital Elevation Model), suggesting that elevation plays an important role in differentiating plantation species.
When applying the classification to the East Coast region, overall 4,582 ha of small-scale alternative species were mapped and the most common alternative species categories are Douglas-fir and Eucalyptus, accounting for 35% and 30% of the total small-scale alternative species resources. Acacia and poplar are the least common alternative species identified, with 72 ha and 59 ha estimated respectively. When aggregated with the area provided by the large-scale owners, in total 5,353 ha of alternative species were estimated in the East Coast region. This is 780 ha (17%) more than the NEFD-reported area. The area of cypress, other softwoods and hardwoods are similar to the NEFD area. However, Douglas-fir was 245 ha (12%) less than the NEFD area and the estimated Eucalyptus area was three times more than the NEFD area. Overall, it appears that NEFD underestimates the total area of small-scale alternative species.
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