B97034
Received 16 June 1997; accepted 31 October 1997
Comparative seedling growth of five endemic New Zealand podocarp species under
different light regimes
R. L. EBBETT
School of Forestry
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
J. OGDEN
School of Environmental and Marine Science
The University of Auckland
Private Bag 92019
Auckland, New Zealand
Abstract The comparative growth of seedlings of
Dacrycarpus dacrydioides,
Podocarpus totara,
Dacrydium
cupressinum,
Prumnopitys ferruginea, and
P.
taxifolia
was investigated at different light levels. Five light regimes were achieved
using shade cloth for glasshouse seedlings (2-25% of full sunlight) and under
different canopy vegetation types (5-30% of full sunlight) in dense lowland
podocarp forest at Whirinaki Forest Sanctuary, Central North Island, New
Zealand. Height growth, stem diameter growth, and dry weight increase were
measured for a 15 month period over two spring seasons in both glasshouse and
forest environments.
The five podocarp species show significant differences in height growth, stem
diameter growth, and dry weight increase under the different light regimes of
both glasshouse and forest environments. Seasonal height growth rates were
examined in the forest, and species exhibited different responses to the
climatic parameters of rainfall, humidity, temperature, and solar radiation.
Comparative growth rates are used to infer regeneration strategies of the five
podocarp species, particularly in response to elevated light levels. Totara and
kahikatea are considered to be light demanding and have the ability to respond
to increased light levels. Both rimu and matai do not appear to have the
ability to respond to elevated light levels and it may be more appropriate to
consider these two species as consistently slow growers. Miro is often
considered the most shade tolerant of the five podocarp species and in the
present study it exhibited an increased growth response to elevated light
levels, especially in the forest.
Keywords Dacrydium cupressinum; Dacrycarpus
dacrydioides; Podocarpus totara; Prumnopitys ferruginea;
Prumnopitys taxifolia; light; growth response; shade tolerance;
regeneration
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