TY - JOUR

T1 - Budgets and chemistry of dissolved organic carbon in forest soils: effects of anthropogenic soil acidification

AU - Zech, Wolfgang

AU - Guggenberger, Georg

AU - Schulten, Hans Rolf

N1 - Funding information: This work was financed by a grant from the Bayerisches Ministerium fiir Landesentwicklung und Umweltfragen. The authors express their appreciation to R. Miiller for recording the Py-FI mass spectra. We also thank B. Glaser and W. GStz for their technical assistance. Furthermore, we are grateful to W. Schaaf and T. Tiirk who put the water fluxes for the three investigated soils at our disposal.

PY - 1994/7/25

Y1 - 1994/7/25

N2 - Budgets and chemistry of dissolved organic carbon (DOC) are compared at three spruce stands receiving different rates of acid deposition. Generally, an increasing input of mineral acids is associated with increased soil acidification and an increased degree of forest decline phenomena. In order to assess the effects of anthropogenic soil acidification on DOC control, we combined measurements of DOC concentrations and fluxes with an analytical approach in terms of DOC fractionation, wet-chemical degradation, and pyrolysis-field ionization mass spectrometry. Mean annual DOC concentration in the mineral soil input varies around 27.0 mg 1-1 at the less damaged stands, and reaches 59.4 mg 1 -1 at the severely damaged stand. We suggest a biotic control of DOC release in the forest floor, which is in turn influenced by environmental conditions. Enhanced anthropogenic N deposition and crown thinning increase the DOC release in the forest floor due to a stimulation of microbial organic matter mineralization. Furthermore, N hampers the ligninase production which results in the accumulation of partly water-soluble soft-rot lignin-degredation products. Sorption of DOC by sesquioxides in the B horizons reduces the mean annual DOC concentration to values between 2.63 mg 1-1 in the least acidified soil and 31.15 mg 1-1 in the most acidified soil. In this soil DOC retention is impeded by soil indigenous factors such as covering of sesquioxides with organic carbon. Moreover, anthropogenic soil acidification results in an increasing DOC output of the mineral soil due to (i) elevated DOC release in the forest floor, (ii) competition of DOC with sulfate for sorption sites, and (iii) loss of Al and Fe oxides/hydroxides due to buffer processes. The less acidified mineral soils are characterized by a pronounced preferential retention of polymeric hydrophobic acids. In contrast, the soil receiving the highest rates of acid deposition shows only a minor qualitative alteration of DOC in the profile.

AB - Budgets and chemistry of dissolved organic carbon (DOC) are compared at three spruce stands receiving different rates of acid deposition. Generally, an increasing input of mineral acids is associated with increased soil acidification and an increased degree of forest decline phenomena. In order to assess the effects of anthropogenic soil acidification on DOC control, we combined measurements of DOC concentrations and fluxes with an analytical approach in terms of DOC fractionation, wet-chemical degradation, and pyrolysis-field ionization mass spectrometry. Mean annual DOC concentration in the mineral soil input varies around 27.0 mg 1-1 at the less damaged stands, and reaches 59.4 mg 1 -1 at the severely damaged stand. We suggest a biotic control of DOC release in the forest floor, which is in turn influenced by environmental conditions. Enhanced anthropogenic N deposition and crown thinning increase the DOC release in the forest floor due to a stimulation of microbial organic matter mineralization. Furthermore, N hampers the ligninase production which results in the accumulation of partly water-soluble soft-rot lignin-degredation products. Sorption of DOC by sesquioxides in the B horizons reduces the mean annual DOC concentration to values between 2.63 mg 1-1 in the least acidified soil and 31.15 mg 1-1 in the most acidified soil. In this soil DOC retention is impeded by soil indigenous factors such as covering of sesquioxides with organic carbon. Moreover, anthropogenic soil acidification results in an increasing DOC output of the mineral soil due to (i) elevated DOC release in the forest floor, (ii) competition of DOC with sulfate for sorption sites, and (iii) loss of Al and Fe oxides/hydroxides due to buffer processes. The less acidified mineral soils are characterized by a pronounced preferential retention of polymeric hydrophobic acids. In contrast, the soil receiving the highest rates of acid deposition shows only a minor qualitative alteration of DOC in the profile.

KW - DOC composition

KW - DOC fluxes

KW - Forest soils

KW - Pyrolysis-mass spectrometry

UR - http://www.scopus.com/inward/record.url?scp=0028161114&partnerID=8YFLogxK

U2 - 10.1016/0048-9697(94)90550-9

DO - 10.1016/0048-9697(94)90550-9

M3 - Article

AN - SCOPUS:0028161114

VL - 152

SP - 49

EP - 62

JO - Science of the Total Environment, The

JF - Science of the Total Environment, The

SN - 0048-9697

IS - 1

ER -