New Zealand Journal of Botany abstract
The relationship between seed rain and the soil seed bank in a temperate
rainforest stand near Auckland, New Zealand
G. SEM
Department of Geography
University of Auckland
Private Bag 92109
Auckland, New Zealand
Present Address: Department of Geography, University of Papua New Guinea, P. O.
Box 320, University 134, National Capital District, Papua New Guinea
N. J. ENRIGHT
Department of Geography and Environmental Studies
University of Melbourne
Parkville
VIC. 3052, Australia
Abstract Composition of the germinable seed rain and the soil
seed bank is documented for five sites in temperate rainforest near Auckland,
New Zealand, in an effort to understand the dynamics of the soil seed bank. The
seed rain added a mean of 202 +/- 93 germinable seeds per 0.1 m2
over 15 months to the forest floor in 1988 and a total of 40 species (range
15-25 per site). The source of seeds included both native forest species
growing on-site, and adventive species of which most were growing off-site.
Species richness of the seed rain was highest in summer (32 species) and lowest
in winter (6 species). However, density of the recorded seed rain was highest
in late autumn-early winter from high seed rain and massive germination in May
and June of seeds from the native tree, Kunzea ericoides, at two sites
in the early stages of forest regrowth. Seed germination from soil samples
which had been denied seed inputs for 15 mo identified the density (52 +/-
41/0.1m2) and composition (18 species, range 2-9) of the
`persistent' component of the seed bank (i.e., seed longevity >1 y). Native
woody species were poorly represented in the persistent seed bank relative to
native herbs and adventives. An estimated 10% of the annual seed rain enters
the persistent soil seed bank. The presence, and dynamics of turnover for most
species in the persistent seed bank can be explained as a balance between
additions of new individuals and loss of old individuals over one to a few
years. At the same time, the combination of high persistent seed bank densities
and low seed rain inputs for a few adventive species (e.g., Phytolacca
octandra, Juncus bufonius) indicates that seed of these species may
derive from individuals which grew at or near the site at some time in the
past.
Keywords soil seed bank; seed rain; seed longevity;
Agathis australis; adventive species; persistent; transient
B95017
Received 11 April 1995; accepted 20 November 1995
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