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Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia
Linköping University, The Tema Institute, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.ORCID iD: 0000-0002-1927-4656
MEM-group, Department of Biosciences, University of Helsinki, Helsinki, Finland.
Ecology and Biodiversity Group, Institute of Environmental Biology, Utrecht University, CH Utrecht, The Netherlands.
MEM-group, Department of Biosciences, University of Helsinki, Helsinki, Finland.
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2015 (English)In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 81, 204-211 p.Article in journal (Refereed) Published
Abstract [en]

Ombrotrophic raised bogs are nutrient poor acidic peatlands accumulating organic matter. They are widely spread on northern latitudes and are substantial sources of methane emissions to the atmosphere being of great concern from a climate change perspective. We investigated the methanogen community composition along microtopographic gradients within three bogs in Scandinavia, receiving different amounts of nitrogen precipitation. Methanogenic community analyses by terminal restriction fragment length polymorphism of the mcrA gene showed different profiles among the three sites, while no in- fluence of the microtopographic gradients was observed. Peat temperature and dissolved organic carbon were the major edaphic variables explaining 38% of the variation of the methanogenic community di- versity among the bogs. The family Methanoregulaceae (hydrogenotrophic methanogens) showed the largest relative proportion and highest activity in all three sites. Quantitative PCR of the mcrA gene and transcripts showed that the most northern site, receiving the lowest atmospheric nitrogen load, had significantly lower abundance and activity of methanogens (4.7 106 and 2.4 104 mcrA copies per gram of soil, respectively), compared to the most southern site (8.2 107 and 4.6 105 mcrA copies per gram of soil, respectively), receiving the highest nitrogen load. No patterns of the mcrA gene and tran- script abundances were observed along the microtopography. The results indicated that the difference in occurrence of methanogens is mainly due to geoclimatological conditions rather than site intrinsic microtopographic variation. The study further suggests that environmental changes on the site intrinsic topography will not affect the methanogenic activity, while increasing average temperatures in Scan- dinavian ombrotrophic raised bogs might contribute to an increase of the methanogenic archaeal activity resulting in an increase of methane production. 

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 81, 204-211 p.
Keyword [en]
Methanogenic arhcaea, mcrA gene, peatland, microtopography, T-RFLP, qPCR
National Category
Ecology Microbiology Environmental Sciences
Identifiers
URN: urn:nbn:se:liu:diva-113846DOI: 10.1016/j.soilbio.2014.11.016ISI: 000350524700024OAI: oai:DiVA.org:liu-113846DiVA: diva2:785109
Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Microbial Communities in Boreal Peatlands: Responses to Climate Change and Atmospheric Nitrogen and Sulfur Depositions
Open this publication in new window or tab >>Microbial Communities in Boreal Peatlands: Responses to Climate Change and Atmospheric Nitrogen and Sulfur Depositions
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Myrmarker har en stor roll i regleringen av den globala kolbalansen och koncentrationerna av koldioxid och metan i atmosfären, vilket gör dem till speciellt viktiga ekosystem ur ett klimatförandringsperspektiv. Förändringar av myrmarker genom naturlig utveckling eller antropogen påverkan kan därför få långtgående störningar av myrars klimatreglerande funktion. Mikroorganismer har en avgörande roll i biogeokemiska processer genom att t ex bryta ned organisk material i mark och därmed styra kolets kretslopp. För att förstå hur myrsystemen reagerar på störningar är det därför väsentligt att veta hur mikroorganismsamhällena reagerar genom förändringar i sammansättning och biogeokemisk aktivitet. Målet för studierna, som ligger till grund för denna avhandling, var att undersöka hur mikroorganismsamhällen i myrar reagerar på uppvärmning genom klimatförändring och ökade kväve- (N) och svavel- (S) halter i nederbörd. High through-put sekvensering användes för att studera taxonomiska och funktionella egenskaper hos mikroorganismerna i myrar och quantative PCR användes för att mer specifikt studera de metanbildande arkeorna. Två fältkampanjer vardera omfattande tre ombrotrofa myrar med olika klimatförhållanden och olika mängder N och S inederbörden användes för att undersöka lokala och storskaliga effekter på myrars mikrobiella samhällen. Resultaten visade att latudinell variation i geoklimatologiska förhållanden (temperatur ochnederbördsmängd) och deposition av näringsämnen hade en påverkan på sammansättningen av de mikrobiella samhällena och aktiva metanbildare förr än variationen i den kemiska miljön inom varje specifik myr. Myrväxtsamhällenas sammansättning för en specifik myr visades sig i stor utsträckning styra sammansättningen av motsvarande mikrobiella samhälle i torvprofilen. Detta framgick klart av i en analys av samexisterande nätverk av mikroorganismsamhällen och motsvarande växtsamhällen i en studie av tre geografiskt skilda myrar med olika kvävedeposition. Effekterna av klimatförändring och nederbörd med olika mängder av N och S studerades mer specifikt genom att analysera de mikrobiellasamhällena i  ett långliggande (18 år) försök. Påverkan av var och en av dessa manipulationer antingen förstärktes eller minskades, när de förekom i kombinationer. Ökad kvävedeposition var den faktor som hade starkast effekt. De långvariga störningarna medförde stora förändringar i den mikrobiella taxonomin inom samhällena. Detta återspeglades dock inte i den fysiologiska kapaciteten, vilket visar att det finns en stark buffring i myrarnas mikrobiella funktion. Detta tyder på att framtida utveckling av myrar i relation till olika störningar sannolikt inte kommer att påverka myrarnas roll för kolbalans och växthusgasutbyte med atmosfären.

Abstract [en]

Peatlands play a substantial role in regulating the global carbon balance and concentrations of the greenhouse gases CO2 and CH4 in the atmosphere, and are thus of utmost importance from a climate change perspective. Any changes of peatland functions due to natural or anthropogenic perturbations may result in changes in these ecosystem services. Soil microbial communities are essential drivers of biogeochemical processes, including the carbon cycle. In order to fully understand the effect of environmental perturbations on peatland functions, it is essential to understand how microbial communities are affected. The aim of the research presented in this thesis was to investigate the responses of the peat microbial communities to climate change and increased precipitation of nitrogen(N) and sulfur (S) compounds. High-throughput sequencing approaches were used to investigate the taxonomic and functional composition of microbial communities, and quantitative PCR was used to specifically target the methanogen community. Two field studies including three ombrotrophic peatlands each that differed in climatological conditions and atmospheric N and S depositions, were used to investigate and compare the effect of large- and local-scale environmental conditions on microbial communities. The results show that the variation in geo-climatological (temperature and precipitation) and atmospheric deposition conditions along the latitudinal gradient modulate the peat microbial community composition and the abundance of active methanogens to a greater extent thansite-related microhabitats. Furthermore, a tight coupling between the plant community composition of a site and the composition of its microbial community was observed, and was found to be mainly driven by plants rather than microorganisms. These co-occurrence networks are strongly affected by seasonal climate variability and the interactions between species in colder areas are more sensitive to climate change. The long-term effects of warming and increased N and S depositions on the peat microbial communities were further investigated using an 18-year in-situ peatland experiment simulating these perturbations. The impacts of each of these perturbations on the microbial community were found to either multiply or counteract one another, with enhanced N deposition being the most important factor. While the long-term perturbations resulted in a substantial shift in the taxonomic composition of microbial communities, only minor changes occurred in genome-encoded functional traits, indicating a functional redundancy. This could act as a buffer maintaining ecosystem functioning when challenged by multiple stressors, and could limit future changes in greenhouse gases and carbonexchange.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 60 p.
Series
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 715
Keyword
Microbial communities, methanogens, plant communities, peatland, temperature, nitrogen, long-term, field experiment, high-throughput sequencing, Microbiella samhällen, metanogener, växtsamhällen, myrar, torv, temperatur, kväve, långtid, fältexperiment, high-throughput-sekvensering
National Category
Physical Geography Water Engineering Climate Research
Identifiers
urn:nbn:se:liu:diva-137487 (URN)10.3384/diss.diva-137487 (DOI)9789176855331 (ISBN)
Public defence
2017-06-09, TEMCAS, hus T, Campus Valla, Linköping, 10:15 (English)
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Supervisors
Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2017-05-17Bibliographically approved

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