During recent soil geographical expeditions to Casey Station (Coastal
Antarctica), soils with the morphological features of Gelic Podzols (WRB:
Spodic Haplic Cryosols) were found to be widespread. The purpose of this paper
is to provide further information on these unique soils with respect to soil
organic matter (SOM), microbiology, and soil formation. Antarctic Podzols
develop on solid rock, outwash sediments, and abandoned penguin rookeries. A
comparison of different SOM depth profiles, however, revealed carbon (C) and
nitrogen (N) of unknown origin. The SOM composition was characterised by a
mean C/N ratio of 10, with a high content of carboxyl-C units, probably
derived from amino acids, organic acids, and oxidised carbohydrates.
Pyrolysis-GC/MS and NMR showed a notable variation between SOM in depth
profiles and the horizons within each profile. Microbial colonisation was
affected by the surface vegetation, content of organic C, and the influence of
seabirds. Correlations between selected SOM compounds and bacteria on the
vegetated soils suggested that algal and moss C influence SOM to a great
extent. Most of the long-chain C moieties in the antarctic Podzols appeared to
contain multiple oxygen- and N-containing functional groups, cyclic ionised
and heterocyclic structures, and alkylations. Data suggest that, along with
the podzolisation process, organic acids, non-humified carbohydrates, and
N-containing moieties migrated from the topsoil into the spodic horizons. The
results are discussed with respect to (i) soil formation
and (ii) microbial colonisation in the cold climate. The
Gelic Podzols hold huge amounts of C and N but their origin is poorly
understood. Explaining the origin of the SOM should be a focus for future
research in antarctic soil biogeochemistry.
Twenty-Five Years of Radiocarbon Dating Soils: Paradigm of Erring and Learning