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Decadal nitrogen addition alters chemical composition of soil organic matter in a boreal forest

Hasegawa, Shun and Marshall, John D and Sparrman, Tobias and Näsholm, Torgny (2021). Decadal nitrogen addition alters chemical composition of soil organic matter in a boreal forest. Geoderma. 386 , 114906
[Research article]

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Abstract

Boreal forests store approximately 470 Pg of carbon (C) in the soil, and rates of soil C accumulation are significantly enhanced by long-term nitrogen (N) enrichment. Dissecting the compositional profile of soils could help better understand the potential mechanisms driving changes in C cycling under enriched N conditions.We examined the impacts of long-term N addition on the chemical composition of soil organic matter (SOM) in a mature boreal forest. Two large experimental plots (15 ha each) were established: a control and a fertilised plot. The latter received NH4NO3 fertilizer at an average rate of 75 kg N ha(-1) year for 12 years. While the centre of this plot received the prescribed amounts of fertilizer, the year-to-year variation in distribution of fertilizer around the designated edges of the plot created a gradient in N-loading. Along this gradient, a compositional shift in SOM in the organic horizon was assessed using two methods: pyrolysis-gas chromatography/mass spectrometry (GC/MS) and solid-state C-13 nuclear magnetic resonance spectroscopy (C-13 NMR).Both of these methods revealed that the chemical composition of SOM changed with increasing N loading, with an increased fraction of lignin derivatives (i.e., aromatic, methoxy/N-alkyl C) relative to that of carbohydrate (i.e., 0-alkyl C), accompanied by increased soil C mass (kg m(-2)) at the fertilised plot. Also, the relative abundance of N compounds in the pyrolysis products increased with the N loading, mainly due to increased methyl N-acetyl-alpha(D)-glucosaminide in the F/H horizon, plausibly of microbial origin. Microbial N processing likely contributed to soil accumulation of fertilizer-derived N.Our results corroborate the hypothesis that addition of inorganic N suppresses enzymatic white-rot decomposition relative to non-enzymatic brown-rot oxidation. Taken together, our study suggests that N enrichment leads to a selective accumulation of lignin-derived compounds and points to a key role of such compounds for N-induced SOM accumulation.

Authors/Creators:Hasegawa, Shun and Marshall, John D and Sparrman, Tobias and Näsholm, Torgny
Title:Decadal nitrogen addition alters chemical composition of soil organic matter in a boreal forest
Series Name/Journal:Geoderma
Year of publishing :2021
Volume:386
Article number:114906
Number of Pages:13
ISSN:0016-7061
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
Keywords:Boreal forest, Soil organic matter, Nitrogen enrichment, Carbon accumulation, Pyrolysis, NMR
URN:NBN:urn:nbn:se:slu:epsilon-p-109534
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-109534
Additional ID:
Type of IDID
DOI10.1016/j.geoderma.2020.114906
Web of Science (WoS)000613923000004
ID Code:22738
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:11 Mar 2021 13:23
Metadata Last Modified:11 Mar 2021 13:31

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