TY - JOUR

T1 - Changes in dissolved lignin-derived phenols, neutral sugars, uronic acids, and amino sugars with depth in forested Haplic Arenosols and Rendzic Leptosols

AU - Kaiser, Klaus

AU - Guggenberger, Georg

AU - Haumaier, Ludwig

N1 - Funding information: The study was funded by the Deutsche Forschungsgemeinschaft joint research program ROSIG and the University of Bayreuth. H. Ciglasch, J. Dilling, T. Gonter, S. Peter, U. Roth, and A. Wetzel assisted during the field and laboratory work. A part of the analyses was carried out by the Central Analytical Department of the Bayreuth Institute of Terrestrial Ecosystem Research. We are grateful to the staff of the Bavarian Forest Administration at Bayreuth and Betzenstein for the help during the selection of the sites and the support during sampling.

PY - 2004/8

Y1 - 2004/8

N2 - A major part of the dissolved organic matter produced in the organic layers of forest ecosystems and leached into the mineral soil is retained by the upper subsoil horizons. The retention is selective and thus dissolved organic matter in the subsoils has different composition than dissolved organic matter leached from the forest floor. Here we report on changes in the composition of dissolved organic matter with soil depth based on C-to-N ratios, XAD-8 fractionation, wet-chemical analyses (lignin-derived CuO oxidation products, hydrolysable sugars and amino sugars) and liquid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Dissolved organic matter was sampled directly beneath the forest floor using tension-free lysimeters and at 90cm depth by suction cups in Haplic Arenosols under Scots pine (Pinus sylvestris L.) and Rendzic Leptosols under European beech (Fagus sylvatica L.) forest. At both sites, the concentrations of dissolved organic carbon (DOC) decreased but not as strongly as reported for deeply weathered soils. The decrease in DOC was accompanied by strong changes in the composition of dissolved organic matter. The proportion of the XAD-8-adsorbable (hydrophobic) fraction, carboxyl and aromatic C, and the concentrations of lignin-derived phenols decreased whereas the concentrations of sugars, amino sugars, and nitrogen remained either constant or increased. A general feature of the compositional changes within the tested compound classes was that the ratios of neutral to acidic compounds increased with depth. These results indicate that during the transport of dissolved organic matter through the soils, oxidatively degraded lignin-derived compounds were preferentially retained while potentially labile material high in nitrogen and carbohydrates tended to remain dissolved. Despite the studied soils' small capacity to sorb organic matter, the preferential retention of potentially refractory and acidic compounds suggests sorption by the mineral soil matrix rather than biodegradation to govern the retention of dissolved organic matter even in soils with a low sorption capacity.

AB - A major part of the dissolved organic matter produced in the organic layers of forest ecosystems and leached into the mineral soil is retained by the upper subsoil horizons. The retention is selective and thus dissolved organic matter in the subsoils has different composition than dissolved organic matter leached from the forest floor. Here we report on changes in the composition of dissolved organic matter with soil depth based on C-to-N ratios, XAD-8 fractionation, wet-chemical analyses (lignin-derived CuO oxidation products, hydrolysable sugars and amino sugars) and liquid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Dissolved organic matter was sampled directly beneath the forest floor using tension-free lysimeters and at 90cm depth by suction cups in Haplic Arenosols under Scots pine (Pinus sylvestris L.) and Rendzic Leptosols under European beech (Fagus sylvatica L.) forest. At both sites, the concentrations of dissolved organic carbon (DOC) decreased but not as strongly as reported for deeply weathered soils. The decrease in DOC was accompanied by strong changes in the composition of dissolved organic matter. The proportion of the XAD-8-adsorbable (hydrophobic) fraction, carboxyl and aromatic C, and the concentrations of lignin-derived phenols decreased whereas the concentrations of sugars, amino sugars, and nitrogen remained either constant or increased. A general feature of the compositional changes within the tested compound classes was that the ratios of neutral to acidic compounds increased with depth. These results indicate that during the transport of dissolved organic matter through the soils, oxidatively degraded lignin-derived compounds were preferentially retained while potentially labile material high in nitrogen and carbohydrates tended to remain dissolved. Despite the studied soils' small capacity to sorb organic matter, the preferential retention of potentially refractory and acidic compounds suggests sorption by the mineral soil matrix rather than biodegradation to govern the retention of dissolved organic matter even in soils with a low sorption capacity.

KW - Dissolved organic carbon

KW - Dissolved organic matter

KW - Dissolved organic nitrogen

KW - Liquid-state C NMR

KW - XAD-8 fractionation

UR - http://www.scopus.com/inward/record.url?scp=4744375075&partnerID=8YFLogxK

U2 - 10.1023/B:BIOG.0000049340.77963.18

DO - 10.1023/B:BIOG.0000049340.77963.18

M3 - Article

AN - SCOPUS:4744375075

VL - 70

SP - 135

EP - 151

JO - BIOGEOCHEMISTRY

JF - BIOGEOCHEMISTRY

SN - 0168-2563

IS - 1

ER -