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Abstract
The potential woody vegetation of Central Otago, South Island, New Zealand, immediately prior to human settlement, is described using complementary lines of evidence. Generalised additive models based on a database of present species locations and environmental surfaces are used to predict the potential distribution of woody species in relation to the environment across a study area of 15 500 km2. Twelve biogeographic zones are classified on the basis of the predicted distributions of the 15 most common potential canopy tree species. The likely structure and composition of each zone is assessed using (1) model‐predicted occurrences of more common canopy, subcanopy, and shade‐intolerant species, and present‐day locations of rarer woody species, (2) compiled information from the subfossil wood, charcoal, and pollen records, and (3) the presence of plant species and life forms in zones of environmental stress. We conclude that water deficit and winter temperature minima are not sufficiently severe to have excluded tall woody vegetation from the intermontane basin and valley floors of Central Otago, and that low forest and shrublands would have dominated here prior to human settle‐ment. At low elevations, grassland was probably confined to floodplains and local areas of shallow or permanently moist soils, while saline soils supported distinctive herbaceous communities. Tall conifer‐hardwood and Nothofagus forests are predicted to have once covered the montane and subalpine range slopes. Analysis of environmental tolerances suggests that shrublands may also have dominated above the regional treeline (770–1380 m a.s.l. in Central Otago) although tall tussocks probably increased in dominance towards the range summits. We discuss the strengths and limitations of the different approaches to vegetation reconstruction. Remaining uncertainties may be resolved with a combination of palaeoecological and physiological research and the application of spatial process modelling. Implications of the work for conservation management are discussed.
