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Lignin degradation

long-term effects of nitrogen addition on decomposition of forest soil organic matter

Sjöberg, Gudrun (2003). Lignin degradation. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Agraria, 1401-6249 ; 419
ISBN 91-576-6449-8
[Doctoral thesis]

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Long-term addition of nitrogen (N) reduces the decomposition rate of humified soil organic matter (SOM) in forest ecosystems causing an increase in SOM storage. This could be an effect of (1) suppressed enzyme activity among white-rot fungi degrading lignin (2) formation of recalcitrant phenolic compounds or (3) altered microbial composition. The aims were to study the long-term effects of N addition on CO2 evolution, production of dissolved organic matter (DOM), lignin degradation and structural changes of the C and N composition. CuO oxidation, solid-state and dipolar-dephasing CPMAS 13C and 15N NMR, Klason lignin and acid detergent lignin (ADL) were used as methods. Fresh and decomposed needle litter, Oi, Oe and Oa layers, and fresh and decomposed root litter were investigated. The needle litter was decomposed under laboratory conditions, whereas the root litter was decomposed in litterbags under field conditions. To estimate CO2 evolution and DOM production, Oe and Oa layers were laboratory incubated in columns. The samples originated from the long-term N fertilization experiment Skogaby in southwestern Sweden (plots denoted NS receiving 100 kg N ha-1 yr-1 as (NH4)2SO4). The long-term N fertilization experiment Stråsan in south-central Sweden (plots denoted N1, N2 and N3 receiving 35, 73 and 108 kg ha-1 yr-1 as NH4NO3) was also used in the column incubation. The unfertilized and the N-fertilized plots at both sites were compared with each other for each layer or decomposition period. The CO2 evolution rate was significantly lower in the NS Oe layer than in the control Oe layer at Skogaby. The N3 Oe layer at Stråsan showed a similar trend. No significant treatments effects on the degree of lignin degradation (expressed as Ac/Al)V) could be found except for 853-day decomposed root litter. The lignin degradation products (VSC) obtained by CuO oxidation did not show any significant treatment effects. No heterocyclic N compounds could be detected by 15N NMR in the forest floor at Skogaby. The dipolar-dephasing technique showed that tannin was present. Tannin might have caused the slight increase in phenolic C with depth. In conclusion, no major qualitative change in the SOM due to N was found and no heterocyclic N compounds were observed. Thus, the common explanations for decreased decomposition due to N additions did not seem to be valid.

Authors/Creators:Sjöberg, Gudrun
Title:Lignin degradation
Subtitle:long-term effects of nitrogen addition on decomposition of forest soil organic matter
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Agraria
Year of publishing :September 2003
Number of Pages:46
ALLI. Sjöberg, G., Bergkvist, B., Berggren, D., Nilsson, S.I. 2003. Long-term N addition effects on the C mineralization and DOC production in mor humus under spruce. Soil Biology & Biochemistry (In press). II. Sjöberg, G., Knicker, H., Nilsson, S.I., Berggren, D. Impact of long-term N fertilization on the structural composition of spruce litter and mor humus. Soil Biology & Biochemistry (In revision). III. Sjöberg, G., Nilsson, S.I., Persson, T., Karlsson, P. Degradation of cellulose and lignin in decomposing spruce needle litter in relation to N. Soil Biology & Biochemistry (Submitted).
Place of Publication:Uppsala
ISBN for printed version:91-576-6449-8
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P34 Soil biology
Subjects:Not in use, please see Agris categories
Agrovoc terms:picea abies, plant litter, humus, lignins, copper, oxidation, surfactants, forest soils
Keywords:Norway spruce, Litter, Mor humus, Lignin, CuO oxidation, Klason lignin, Acid detergent lignin, 13C NMR, 15N NMR
Permanent URL:
ID Code:341
Department:(NL, NJ) > Dept. of Soil Sciences (until 081001)
Deposited By: Gudrun Sjöberg
Deposited On:18 Sep 2003 00:00
Metadata Last Modified:02 Dec 2014 10:03

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