Status of widespread indigenous trees

  • Image, Status of widespread indigenous trees.

    Eight indigenous tree species, spanning a range of ecological niches, were surveyed twice between 2002 and 2014 as part of a vegetation monitoring programme. The data from these surveys can be used to assess changes in tree populations. Monitoring the status and trends of these widespread tree species helps us detect large-scale, long-term changes and problems for our forest ecosystems.

    We classified Status of widespread indigenous trees as a national indicator.

    Key findings

     Trend not assessed

    For 7 of 8 tree species investigated in two surveys (taking place between 2002 and 2014), the number of newly established trees (recruitment) was either greater than or not significantly different from the number of trees that died (mortality).

    • For the remaining species, the number of trees that died was greater than the number of newly established trees.
    • No significant changes occurred in the number of trees per hectare for any of the eight tree species surveyed.

    Figure 1

    Figure 2

    Note: Error bars represent standard error. Surveys with overlapping error bars are unlikely to be significantly different.

    Definition and methodology

    The status of widespread indigenous trees provides information on the nationwide population trends of eight widespread species of trees: broadleaf, lowland and mountain five-finger, kohekohe, patē, southern rātā, and lowland and upland tōtara.

    This information is from 869 survey plots (20m x 20m) distributed across forests on both public conservation land and private land around New Zealand. Each plot was first surveyed between 2002 and 2007. All trees with trunk diameters greater than or equal to 2.5cm when measured at 1.35m height (called ‘diameter at breast height’ or DBH) were tagged and identified. The same plots were resurveyed between 2009 and 2014. Any trees present in the first survey but missing from the second survey were recorded as dead. Any trees not recorded in the first survey but recorded in the second survey as having a trunk greater than or equal to 2.5cm DBH were recorded as newly established trees.

    This indicator does not include information on the state of small species, or seedlings and saplings that might have been removed by herbivores before reaching the height and size of a new tree as defined above.

    Data quality

    We classified Status of widespread indigenous trees as a national indicator.

    Relevance

    relevance-direct This national indicator is a direct measure of the ‘Presence and abundance of indigenous plants and animals’ topic.

    Accuracy

    accuracy-high The accuracy of the data source is of high quality.

    See Data quality information for more detail.

     

    Published 21 October 2015

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