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Abstract
This study describes the flora and vegetation of pakihi land (mostly rush-fernland) and surrounding vegetation in North Westland. This work is a prerequisite for determining the degree to which the reserve system represents the diversity of pakihi vegetation, and will aid reserve management.
Thirty five areas of pakihi vegetation in seven Ecological Districts were sampled using non-area plots. Soil profile features were recorded from auger samples and soil pits. Leptospermum scoparium stem ages and densities were recorded. Floristic data were analysed using TWINSPAN and DECORANA. Twelve plot groups were identified, from forest to open herbaceous vegetation. The first axis of the ordination was interpreted as relating primarily to soil drainage and to fire frequency. The second axis related mainly to soil nutrient status, influenced by release of nutrients following disturbance, e.g., by fires after forest clearance.
Most pakihi areas once supported forest and many are being invaded by L. scoparium. There is a close and statistically significant correlation between the age of L. scoparium scrub and the number of woody species in the vegetation. Given time, and the absence of fire, this scrub would revert to forest of podocarps and species of Nothofagus.
The flora and composition of the pakihis varies throughout North Westland. Those in western Ecological Districts, at high altitudes, and near Lake Hochstetter are the most distinctive groupings. These differences may be related to landform features, climate, and vegetation history.
The dynamic nature of pakihi vegetation will require reserves including them to be managed, particularly with fire, if their distinctive features, ranging from rare orchids to fern birds, are to be conserved.
