New Zealand Journal of Botany abstracts
Productivity-decomposition dynamics of Baumea juncea and Gleichenia
dicarpa at Kaitoke Swamp, Great Barrier Island, New Zealand
Andrew P. McK. Pegman*
J. Ogden
School of Geography and Environmental Sciences
University of Auckland
Private Bag 92019
Auckland 1142, New Zealand
*Present address: 21 Victory Road, Laingholm, Auckland 0604, New
Zealand
Abstract The productivity and decomposition of Baumea juncea and Gleichenia dicarpa
were measured at two sites at Kaitoke Swamp, Great Barrier Island, New
Zealand, to determine their annual biomass dynamics. These
interactions, including resulting peat accumulation, are poorly
understood, especially for wetland sedges. Annual productivity and
maximum "standing" above-surface and below-surface biomass were
measured using sequential harvest plots. Decomposition was determined
using recently dead B. juncea culms and G. dicarpa fronds confined in
mesh litter bags placed on, above, and below the swamp surface.
The annual productivity of B. juncea (c. 1.4 kg m-2) was within worldwide estimates for swamp wetland species,
but that of G. dicarpa (c.0.5
kg m-2) was low. The order of decomposition of B. juncea leaf litter was: surface > above surface >
below surface; but in the case of G. dicarpa
there were no significant differences. Litter bag mesh size did not
affect decomposition processes for either species, indicating that
larger decomposer animals probably do not have a significant influence
on biomass loss. Peat accumulation was estimated based on observations
and measurements of the entrainment process. Baumea juncea and G. dicarpa both had high peat accumulation, with 71.6% (0.99
kg m-2 yr-1) and 42.8% (0.22
kg m-2 yr-1)
of the annual production remaining, respectively, after all components
had been underground for 5 years. Consequently, only a small amount of
the annual production of biomass is lost from both sites.
Keywords annual production; Baumea juncea;
biomass components; decomposition; entrainment process; Gleichenia
dicarpa; Great Barrier Island; growth cycle; peat accumulation
B06007; Received 27 February 2006; accepted 24 May 2006; Online
publication date 7 September 2006
New Zealand Journal of Botany, 2006, Vol. 44: 261–271
0028–825X/06/4403–0261 © The Royal Society of New Zealand 2006
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