Litter Decomposition in Temperate Peatland Ecosystems: The Effect of Substrate and Site |
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Authors: | Tim R Moore Jill L Bubier Leszek Bledzki |
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Institution: | (1) Department of Geography and Global Environmental and Climate Change Centre, McGill University, 805 Sherbrooke St. W, Montreal, Quebec, H3A 2K6, Canada;(2) Environmental Studies Program, Department of Earth and Environment, Mount Holyoke College, South Hadley, Massachusetts 01075, USA |
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Abstract: | Abstract
The large accumulation of organic matter in peatlands is primarily caused by slow rates of litter decomposition. We determined
rates of decomposition of major peat-forming litters of vascular plants and mosses at five sites: a poor fen in New Hampshire
and a bog hummock, a poor fen, a beaver pond margin and a beaver pond in Ontario. We used the litterbag technique, retrieving
triplicate litterbags six or seven times over 3–5 years, and found that simple exponential decay and continuous-quality non-linear
regression models could adequately characterize the decomposition in most cases. Within each site, the rate of decomposition
at the surface was generally Typha
latifolia leaves = Chamaedaphne
calyculata leaves = Carex leaves > Chamaedaphne
calyculata stems > hummock Sphagnum = lawn/hollow Sphagnum, with exponential decay constant (k) values generally ranging from 0.05 to 0.37 and continuous-quality model initial quality (q
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) values ranging from 1.0 (arbitrarily set for Typha leaves) to 0.7 (Sphagnum). In general, surface decay rates were slowest at the bog hummock site, which had the lowest water table, and in the beaver
pond, which was inundated, and fastest at the fens. The continuous-quality model site decomposition parameter (u
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) ranged from 0.80 to 0.17. Analysis of original litter samples for carbon, nitrogen and proximate fractions revealed a relatively
poor explanation of decomposition rates, as defined by k and q
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, compared to most well-drained ecosystems. Three litters, roots of sedge and a shrub and Typha leaves, were placed at depths of 10, 30 and 60 cm at the sites. Decomposition rates decreased with depth at each site, with
k means of 0.15, 0.08 and 0.05 y−1 at 10, 30 and 60 cm, respectively, and u
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of 0.25, 0.13 and 0.07. These differences are primarily related to the position of the water table at each site and to a lesser
extent the cooler temperatures in the lower layers of the peat. The distinction between bog and fen was less important than
the position of the water table. These results show that we can characterize decomposition rates of surface litter in northern
peatlands, but given the large primary productivity below-ground in these ecosystems, and the differential rates of decomposition
with depth, subsurface input and decomposition of organic matter is an important and relatively uncertain attribute. |
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Keywords: | bog fen sedge moss shrub roots |
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