New Zealand's forest and shrubland communities: a quantitative classification based on a nationally representative plot network

Abstract

Question: What are the composition, structure and extent of contemporary, common woody vegetation communities in New Zealand? How do the woody plant communities we describe, based on representative sampling, compare to those of previous New Zealand classifications?Methods: We used cluster analysis to classify data from 1177 systematically located vegetation plots, calculated spatial extent and ecological statistics for each alliance defined, and combined forest alliances into groups to assess correspondence with earlier mapped classifications. We used plot-based data on vegetation structure to infer potential community changes.Results: Twenty-four alliances were recognized, each of 19 to 105 plots, with estimated extents of 144 000-794 000 ha. Stand structure data suggest that 15 alliances are largely stable whereas nine may undergo compositional change. Among alliances, the proportion of exotic species ranged from 0 to 50%. Our forest and shrubland classification is another stage in progressively revising such classifications (i.e. forest class maps, vegetative cover map, ECOSAT woody classification and land cover database) produced over the last five decades.

Expanding an existing classification of New Zealand vegetation to include non-forested vegetation

“…The temporal extent includes any vegetation measurements from1970 onwards. The thematic extent includes records of vascular plants in non-forested vegetation, including shrublands that were not previously defined in the classifications of woody vegetation of Wiser et al (2011) or Wiser andDe Cáceres (2013).…”

“…A framework has recently been developed, termed 'semisupervised clustering' (Tichý et al 2014), that allows new data to be incorporated into a pre-existing classification, while retaining types defined in the original classification (De Cáceres et al 2010). For New Zealand's woody vegetation, adopting this framework allowed the 17 vegetation alliances described by Wiser et al (2011) to be retained and also related to a finer thematic level when new data were analysed, and 12 new alliances and 79 associations to be defined (Wiser & De Cáceres 2013; the names 'alliance' and 'association' follow usage in Europe and North America; Peet & Roberts 2013). Adopting this framework allows us to initiate the development of a plot-based, quantitative classification of New Zealand's non-forest vegetation despite data not being comprehensive.…”

“…Here, the primary measure is species percentage cover in height strata using predefined cover classes. Data from disparate projects were incorporated into the classification of Wiser et al (2011) to begin a description of less common woody vegetation types and to increase the typological resolution of the classification (Wiser & De Cáceres 2013). The third factor was that much of the forest compositional data are readily available from the National Vegetation Survey Databank (Wiser et al 2001).…”

New Zealand forest dynamics: a review of past and present vegetation responses to disturbance, and development of conceptual forest models

“…Nevertheless, NZ's native forests ( Fig. 2) can be divided into two broad classes: beech forests (with Nothofagaceae), and mixed conifer-angiosperm forests (including the northern forests where kauri Agathis australis is patchily dominant); these forest types have been described in detail by Wardle (1984), Wardle (1991), Ogden and Stewart (1995), Leathwick (2010), Wiser et al (2011), Allen et al (2013) and Singers and Rogers (2014). Our nomenclature here follows the New Zealand Plant Conservation Network (www.nzpcn.org.nz).…”

“…and Lophozonia menziesii) comprise the major forest element, whether in pure associations or in mixtures with conifers or broadleaved angiosperms, account for approximately 60% of what remains of New Zealand's indigenous forests (Wiser et al 2011;Allen et al 2013). Beech-dominated forests are the least floristically diverse of NZ's forest types (Ogden et al 1996) and are typically associated with higher latitudes and elevations, and lowland areas with infertile and poorly drained soils (Wardle 1984).…”