New Zealand Journal of Botany abstract
Aspects of the ecology and conservation of the threatened tree Olearia
hectorii in New Zealand
G. M. ROGERS
Manaaki Whenua - Landcare Research
Private Bag 3127
Hamilton, New Zealand
Present address: Department of Conservation, P. O. Box 5244, Dunedin, New
Zealand
Abstract Olearia hectorii Hook.f. is a low-growing
deciduous tree confined to four widely separated districts in New Zealand:
Rangitikei and southern Wairarapa in the North Island; and Nelson-Marlborough
and Otago-Southland in the South Island. Topographically it occurs where
mountains or hill country meet alluvial lowland on sites variously affected by
flooding and siltation, debris avalanching, seasonal waterlogging and drought,
and frost - environmental factors that reduce competition from taller trees.
The species escapes competition from taller forest trees as a component of
seral vegetation, occupying sites such as cut-off meanders and frosty
depressions, which are marginal to forest trees, and exploiting light gaps in
forest understoreys beneath lightly-canopied or deciduous broadleaved trees.
Only three of the 24 extant populations of O. hectorii occur in
self-maintaining habitats; the remainder have low numbers and, in many
instances, habitat viability through agricultural fragmentation of the former
forest ecosystem. Clearance of forest, competing ground cover of introduced
grasses and herbs, and damage from browsing animals have led to a loss of at
least eight populations this century, and induced a regeneration failure in
many of the extant populations. However, the present regionally disjunct
distribution in eastern lowland valleys and plains is probably similar to that
of pre-human times.
Keywords conservation; endangered plants; Olearia
hectorii; New Zealand; endemism
B94055
Received 15 December 1994; accepted 5 February 1996
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