25th International Meeting on Organic Geochemistry IMOG 2011

O-31
The fate of collembola derived organic matter in soil
Ian Bull 1 , Andrew Rawlins 1 , Philip Ineson 2 , Richard Evershed 1
1 University of Bristol, Bristol, United Kingdom, 2 University of York, York, United Kingdom
Soil collembola play an important role in the initial
degradation and physical structuring of organic matter
entering the soil environment, especially in soils that
are in the early succession stages (Rusek, 1975).
However, the consequences of digestion for organic
matter are poorly understood at the molecular level.
Most soils contain millions of collembola faecal pellets
per square metre and it is thought these are beneficial
in releasing nutrients to plant roots as the faecal
material is decomposed by microbes (Hopkin, 1992).
Despite its importance, very little is known about the
fate of collembola derived organic matter, i.e.
collembola faeces, in the soil.
Organic matter processed by collembola (and the
faecal pellets produced), in a series of time-course
laboratory studies, was assessed and compared
using a range of analytical techniques. 13 C-labelled
substrates were used to examine the differences in
the decomposition processes taking place and to
determine the microbial community responsible for
organic matter decomposition in soil microcosms.
The biochemical composition of collembola diets
and the corresponding faeces were determined and
revealed that labile components of the diet such as
triacylglycerols, sterols, carbohydrates and short
chain/unsaturated fatty acids were readily assimilated
by collembolan, most likely satisfying their nutritional
requirements. More recalcitrant components of the
fresh organic matter such as wax esters, n-alkanes
and long chain fatty acids were still degraded by
collembola, albeit more slowly than labile
components. Lignin exhibited a marked resistance to
degradation by passage through the collembolan gut,
although guaiacyl pyrolysis products appeared to be
least affected as they became more dominant in the
collembola faeces. These results agree with those of
a previous analogous study of the pill millipede
(Rawlins et al., 2006). Changes in the composition
and abundance of biopolymers in soil microcosms
were investigated using pyrolysis gas
chromatography mass spectrometry. An increase in
abundance of guaiacyl components with carbonyl
functional groups was observed in amended soil after
incubation, indicating that lignin present after
incubation was at a more advanced state of
degradation. The concentration of carbohydrates was
much lower after incubation, with all soils containing
roughly the same concentration. The microbial
community involved in the decomposition of organic
matter was investigated by combining phospholipid
fatty acid (PLFA) analysis with compound-specific
stable carbon isotope analysis. The microbial biomass
found in all incubated soils was of a similar size and
was dominated by Gram-negative bacteria, indicated
by the occurrence of a predomiant C18:1�7 PLFA in
most soils after incubation. An increase in
concentration and � 13 C value of 10methylhexadecanoic
acid in some of the amended
soils reflects the important role played by
actinomycetes in lignin degradation, indicating that
lignin transformations and/or wholesale degradation
occurred within the timescale (80 days) of the
experiment.
References
Hopkin, S. P. (1992) Colembola. In : R. LAL (Ed.)
Encyclopaedia of Soil Science. Marcel Dekker, New
York, pp. 207-210.
Rawlins, A. J., Bull, I. D., Poirier, N., Ineson, P. and
Evershed, R. P. (2006) The biochemical
transformation of oak (Quercus robur) leaf litter
consumed by the pill millipede (Glomeris
marginata). Soil Biology and Biochemistry38, 1063-
1076.
Rusek, J. (1975) Die bodenbildend Funktion von
Collembolen und Acarina. Pedobiologia 15, 299-
308.
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