New Zealand Journal of Botany abstracts
Topsoil seed banks in grazed and ungrazed eucalypt woodlands at Newholme,
Armidale, New South Wales, Australia
CARL D. GRANT
CATHERINE M. MACGREGOR
Ecosystem Management
School of Rural Science and Natural Resources
University of New England
Armidale, NSW 2351, Australia
Abstract Germinable soil seed stores were estimated in grazed
and ungrazed woodlands at Newholme (Armidale, New South Wales) to establish
whether there is a store in the topsoil of shrub species that are no longer
present in the extant vegetation. Soils were subjected to combinations of smoke
and heat treatments before the germination procedure was commenced. The mean
germinable topsoil seed reserve to a depth of 10 cm was 10 855 seeds
m
-2. Of this, 72% of seed was found in the upper 5 cm of soil.
Two rush species (
Juncus filicaulis and
J. homalocaulis, 3185 and
1197 seeds m
-2, respectively) and the perennial herb
Gnaphalium
gymnocepahalum (1728 seeds m
-2) were the most abundant species
in the topsoil. Almost half (46%) of the topsoil seed reserve was composed of
rushes or sedges, while perennial herbs composed a further 30%. Shrub species
were almost absent from the topsoil seed store. Soils collected from grazed
plots (12 360 +/- 2673 seeds m
-2) did not have significantly
different densities of topsoil seed to ungrazed plots (9351 +/- 2588 seeds
m
-2). However, four species showed a significantly greater seed
store in the grazed than the ungrazed plots (
Asperula conferta,
Eragrostis trachycarpa,
Plantago lanceolata, and
Sporobolus
creber), while
Elymus scaber (a native grass) exhibited a
significantly higher topsoil seed store in the ungrazed plots.
Of the 69 species identified, 4 species showed significantly higher
germination in smoked treatments (Centaurium tenuiflorum, Crassula
sieberiana, Hypericum gramineum, and Plantago lanceolata),
while 10 species exhibited significantly higher germination in unsmoked
treatments. Five species exhibited significantly higher germination in heated
trays (Desmodium varians, Dichondra repens, Geranium
potentilloides, Trifolium campestre, and Trifolium repens),
while 49 species showed significantly higher levels of germination in unheated
trays. Species responding to the smoke treatment were native and non-native
annuals, while those responding to the heat treatment were mainly perennial
legume species. Those species that showed increased germination with smoking
were killed by the heat treatment, while those species that required heat to
germinate showed no response to smoke. Comparison of the topsoil seed reserve
and the vegetation present in these areas using Detrended Correspondence
Analysis (DCA) showed that there was a large difference in both composition and
abundance between the topsoil and the extant vegetation. Only two shrub species
were relatively abundant (>10% frequency) in the extant vegetation
(Bursaria spinosa and Lissanthe strigosa). The
implications of these findings to the management of woodlands at Newholme are
discussed.
Keywords soil seed bank; Eucalyptus woodlands; grazed;
ungrazed; heat treatment; smoke treatment
B00055
Received 19 December 2000; accepted 26 February 2001
New Zealand Journal of Botany, 2001, Vol. 39: 471-481
0028-825X/01/3903-0471 $7.00 (c) The Royal Society of New Zealand 2001
PDF file of entire paper: medium quality (1230K); (scanned from paper original: notes about this process)
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