MODELING RELATIONSHIPS BETWEEN ENVIRONMENT AND CANOPY COMPOSITION IN SECONDARY VEGETATION IN CENTRAL NORTH-ISLAND, NEW-ZEALAND

Relationships between composition of secondary vegetation and environm ent were studied in central North Island, New Zealand. A classificatio n procedure was used to identify broad compositional groups which incl uded forest, broadleaved scrub, shrub-fernland, sclerophyllous scrub a nd shrubland, and tussock-shrubland. Generalised additive models (GAMs ) were used to examine relationships between species' distributions an d mean annual temperature and rainfall, stand age, distance from intac t forest, slope, topography, and drainage. There were marked differenc es in the environmental relationships of individual species. We conclu de that temperature and rainfall have a dominant role in determining s uccession after disturbance at a regional scale, but distance from int act forest, topography, slope and solar radiation, become important at local scales. Variation unaccounted for by these environmental factor s is most likely linked to historical factors such as variation in dis turbance and/or grazing and browsing regimes. Intervention by managers will probably be required in the future if the current diversity of s econdary vegetation in central North Island is to be maintained.