K. Kalbitz, Properties of organic matter in soil solution in a German fen area as dependent on land use and depth, GEODERMA, 104(3-4), 2001, pp. 203-214
The aim of this study was to identify the differences in the composition of
dissolved organic matter (DOM) in soil dependent on both land use and soil
depth. Soil solutions of six differently used sites in a German fen area w
ere sampled using ceramic suction cups at three depths (25, 55 and 95 cm) a
nd analyzed for dissolved organic carbon (DOC) over a 2 1/2-year period. St
udies on DOM composition included UV and fluorescence spectroscopy as well
as a fractionation in hydrophobic and hydrophilic components. The DOC conce
ntration was affected by land use in topsoil only. Degraded peatlands had a
high intensity of land use and therefore a low soil carbon content and low
DOC concentrations. The DOC concentrations decreased significantly with in
creasing soil depth. The DOM retention through adsorption or decomposition
was much higher at intact peatlands than at degraded peatlands. The degrade
d peatlands soil DOM had a higher specific absorption at 285 nm and a highe
r humification index derived from fluorescence spectra than DOM of intact p
eatlands (low intensity of land use) down to the subsoil. The higher DOM hu
mification was related to strong peat decay. The DOM of degraded peatlands
preserved its higher degree of aromaticity and polycondensation down to the
subsoil, although highly condensed and substituted aromatic compounds were
retained preferentially with increasing soil depth. Therefore, effects of
land use on the soil DOM composition are stronger than the effects dependen
t on increasing soil depth. The DOM fractionation in hydrophobic and hydrop
hilic components was not sensitive enough to detect the small differences i
n DOM composition caused by land use and depth. (C) 2001 Elsevier Science B
.V. All rights reserved.