New Zealand Journal of Botany abstract
The biology of kauri (Agathis australis ) in New Zealand. I. Production,
biomass, carbon storage, and litter fall in four forest remnants
W. B. SILVESTER
T. A. ORCHARD
Department of Biological Sciences
The University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract Four kauri forest sites, ranging from pole stands to
mature forest, were surveyed for standing biomass and forest floor biomass.
Destructive sampling was done at two further sites to obtain data on tree form
and biomass. Total dry matter, including that on the forest floor, ranged from
132 to 2290 t ha
-1, with as much as 546 t ha
-1 of forest
floor litter and humus in the oldest stand. Total stored carbon above the
mineral soil ranged from 64 to 990 t ha
-1. Litter fall was collected
monthly in five 1-m
2 litter traps at each site for two years. Total
annual litter fall ranged from 4.5 to 13.2 t ha
-1 with leaf litter
making up 41% or less, by weight, of the total litter fall. Forest floor
accumulation of litter in kauri forest is extremely high with mean residence
time of 9-78 years. In general, sites with higher litter fall are accompanied
by faster breakdown, but at all sites litter decomposition is slow. Leaf area
index (LA) of light-suppressed saplings and poles ranged from 0.08 to 0.84,
whereas young emergent trees had LA of 3.33-3.66. LA of mature trees, estimated
from litter fall and mean leaf age, was 1.0-3.0, with a new foliage increment
of 0.4-0.9 LA per annum. A simple biomass and production model for two mature
kauri site shows a wide variation in production. For Trounson Forest, a site
with mature trees, the net production is c. 8.5 t ha
-1
yr
-1 with 2.4 t allocated to wood, 2 t to roots, and 4.1 t to
replacing litter fall. For a younger stand on farmland at Kaipara Flats, net
production is c.15 t ha
-1 yr
-1 with 11.1 t allocated to
replacing litter fall.
Keywords kauri; Agathis australis; biomass; carbon
storage; forest production; leaf area index; litter fall
B98058
Received 8 October 1998; accepted 12 March 1999
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