25th International Meeting on Organic Geochemistry IMOG 2011

P-024
The phenolic characterisation of peat profiles along a vegetation
succession using 13C-labelled tetramethylammonium hydroxide
(13C-TMAH) thermochemolysis
Eleanor Swain, Geoffrey Abbott
Newcastle University, Newcastle upon Tyne, United Kingdom (corresponding author:geoff.abbott@ncl.ac.uk)
Northern peatlands cover an area of around 350 x10 6
ha, and store approximately one-third of global soil
carbon (C) 1 . Peatland vegetation varies in response to
external drivers including climate induced
disturbance, due to differences in tissue biochemistry
and changes in litter reactivity. These factors are
poorly understood, but critical to understanding soil
organic matter turnover in peatlands and its response
to a changing climate. This study aims to provide a
detailed and comprehensive SOM characterisation of
a peatland using thermally assisted hydrolysis and
methylation (THM) in the presence of 13 C-TMAH.
Peat profiles were sampled from Wark Forest, an
afforested moorland site in northeast England. The
site includes two soil profiles in an undisturbed open
bog and four profiles in a bog margin. The bog margin
comprised two pits amongst Sitka spruce but not
situated underneath the canopy, and two pits located
directly under the canopy of Sitka spruce.
Figure 1: Depth profile showing changes in total lignin
products (Λ) (x10 -2 mg/100mg OC). SE = 4.
The addition of 13 C-TMAH allows the distinction
between intact lignin, degraded lignin and non-lignin
phenols to be made 2 .
This site was selected due to the absence of any
recent human influence on the peat, to allow us to
explore the effect of direct lignin and tannin inputs on
the geochemical and carbon contents of the peat
down the profile.
A high Sphagnum input is observed in the surface
litter of the peat beneath the Sitka Spruce, indicating
a current vegetation cover of Sphagnum. The
Sphagnum and lignin inputs (Figs.1 & 2 respectively)
are very low in the deeper organic horizons,
suggesting an increased SOM turnover.
The phenolic composition of the SOM of the surface
litter reflects the vegetation input at all three sites.
However, these molecular characteristics are lost with
increasing depth. The open bog site with no
Sphagnum at the surface had a significantly higher
carbon storage compared to the bog margin sites
(409 and 290 t C/ha respectively). This suggests that
Sphagnum moss may not incorporate more carbon
than any other plant genus as previously thought 3 .
Figure 2: Depth profile showing changes in total
Sphagnum products (mg/100mg OC). SE = 2.
[1] Gorham, E. (1991) Ecological Applications 1(2)
182-195; [2] Filley, T., Minard, R., and Hatcher, P.
(1999) Organic Geochemistry 30(7) 607-621; [3]
Clymo, R., and Hayward, P.(1982) in Bryophyte
Ecology 229-289.
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