A. Van Den Pol-van Dasselaar et O. Oenema, Methane production and carbon mineralisation of size and density fractionsof peat soils, SOIL BIOL B, 31(6), 1999, pp. 877-886
For the purpose of characterisation of soil organic matter breakdown, soil
organic matter is often divided into different fractions, each with its own
decomposition rate. Thus far, no attempts had been made to quantify the me
thane production capacity of individual soil fractions. We aimed to improve
our understanding of CH4 emissions from peat soils by studying the CH4 pro
duction capacity of individual soil fractions in parallel with their carbon
mineralisation capacity. Samples from two wet grasslands on peat soil (0-6
0 cm) were fractionated into different size and density fractions (> 2.0 mm
; 0.25-2.0 mm, light; 0.25-2.0 mm, heavy; 150-250 mu m, light; 150-250 IJ-m
, heavy; <150 mu m) using sieves and Ludox, an aqueous colloidal dispersion
of silica particles. The individual fractions were rather similar with res
pect to C mineralisation capacity and C-to-N ratio, but not with respect to
CH4 production capacity. C mineralisation capacity ranged from 10 to 100 m
u mol CO2-C g(-1) C d(-1) and decreased with depth. CH4 production capacity
ranged from 0 to 150 nmol CH4-C g(-1) C d(-1). We found that significant C
H4 production only occurred for fractions with a large particle size; the f
raction >2.0 mm contributed 90% to total CH4 production capacity. Furthermo
re, CH4 production capacity strongly decreased with depth; the layer 0-5 cm
contributed 70% to total CH4 production capacity. This indicates that in t
he wet peat soils recent plant residues are a major substrate for methanoge
ns. (C) 1999 Elsevier Science Ltd. All rights reserved.