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The effect of simulated anthropogenic nitrogen deposition on the net carbon balance of boreal soils

Maaroufi, Nadia (2016). The effect of simulated anthropogenic nitrogen deposition on the net carbon balance of boreal soils. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2016:98
ISBN 978-91-576-8698-5
eISBN 978-91-576-8699-2
[Doctoral thesis]

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Abstract

Anthropogenic activities have globally increased nitrogen (N) deposition and carbon dioxide (CO₂) gas emissions. It is proposed that anthropogenic N deposition may increase the size of boreal forest CO₂ sink, because boreal ecosystems are N limited. Despite studies that have helped to clarify the magnitude by which N deposition enhances carbon (C) sequestration in the vegetation, there remains a paucity of studies evaluating how soils respond. This thesis aims to clarify the magnitude to which C sequestration in boreal forests responds to N enrichments, including rates that realistically simulated N deposition (≤ 12.5 kg N ha⁻¹ yr⁻¹). This work was conducted in two long-term experiments in northern Sweden. The N treatments consisted of ambient, low N addition (3-12.5 kg N ha⁻¹ yr⁻¹) and high N addition (50 kg N ha⁻¹ yr⁻¹) rates, in a Norway spruce and a Scots pine forest, maintained since 1996 and 2004, respectively. The organic soil C pool positively responded to N enrichment, especially at the high N addition level. This increase corresponded to a relationship between C sequestration and N addition of 10 kg C kg⁻¹ N. Further, low N addition treatments had no effect on microbial biomass and soil respiration (i.e. soil C outputs, microbial activity), while high N addition decreased total microbial, ectomycorrhizal fungal biomasses and soil respiration. The actinomycetes were the only microbes showing an increase with N addition. Annual litter production showed a minor impact on aboveground litter C inputs. Only mosses were the only major litter component showing significant quantitative and qualitative changes in response to N additions. Further, litter quality mediated by N enrichment was not the main driver of litter decomposition, while shifts in soil microbes strongly influence the early stages of litter decomposition. Low N addition rates had little effect on litter and humus decomposition, whereas high N addition rates impeded the early stage of decomposition of both substrates. The decline of litter decomposition appeared to be mediated by shifts in the abundance or community structure of saprophytic organisms, while the decrease of humus decomposition was likely the result of reduced ectomycorrhizal fungi. Altogether, the results of this thesis show that long-term N inputs simulating current atmospheric N deposition in the boreal region are likely to have subtle effects on the soil C balance and therefore on soil C accumulation.

Authors/Creators:Maaroufi, Nadia
Title:The effect of simulated anthropogenic nitrogen deposition on the net carbon balance of boreal soils
Series/Journal:Acta Universitatis agriculturae Sueciae (1652-6880)
Year of publishing :30 September 2016
Depositing date:30 September 2016
Volume:2016:98
Number of Pages:77
Papers/manuscripts:
NumberReferences
IMaaroufi, N.I., Nordin, A., Hasselquist, N.J., Bach, L.H, Palmqvist, K. and Gundale, M.J. (2015). Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils. Global Change Biology 21(8), 3169-3180. DOI: 10.1111/gcb.12904
IIMaaroufi, N.I., Nordin, A., Palmqvist, K. and Gundale, M.J. (2016). Chronic nitrogen deposition has a minor effect on the quantity and quality of aboveground litter in a boreal forest. PLOS ONE 11(8), e0162086. DOI: 10.1371/journal.pone.0162086
IIIMaaroufi, N.I., Nordin, A., Palmqvist, K. and Gundale, M.J. (2016). Nitrogen enrichment impacts on boreal litter decomposition are driven by changes in soil factors rather than litter quality (submitted manuscript).
IVMaaroufi, N.I., Nordin, A., Palmqvist, K., Hasselquist, N.J., Forsmark, B., Rosenstock, N., Wallander, H. and Gundale, M.J. Shifts in ectomycorrhizal and saprophytic fungal communities mediate litter and humus decay in response to chronic nitrogen enrichment (manuscript).
Place of Publication:Umeå
Publisher:Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8698-5
ISBN for electronic version:978-91-576-8699-2
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:K Forestry > K01 Forestry - General aspects
P Natural resources > P34 Soil biology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Ecology
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Soil Science
Agrovoc terms:boreal forests, forest soils, carbon sequestration, carbon cycle, nitrogen fertilizers, nitrogen cycle, fertilizer application, soil respiration, ectomycorrhizae, humus, forest litter, soil microorganisms, simulation models, sweden
Keywords:boreal forest, carbon sequestration, soil respiration, litter, humus, PLFA, ectomycorrhizae, ecological stoichiometry, root-exclosure, nitrogen addition
URN:NBN:urn:nbn:se:slu:epsilon-e-3714
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3714
ID Code:13700
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
External funders:Centre for Environmental Research (CMF)
Deposited By: Nadia Maaroufi
Deposited On:04 Oct 2016 09:00
Metadata Last Modified:05 Oct 2016 04:54

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