4 Microbial nitrogen cycling in permafrost soils: implications for atmospheric chemistry

Horn, Marcus A.; Hetz, Stefanie A.

doi:10.1515/9783110497083-004

Cited by 3 publications

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“…A complex network of metabolically versatile microorganism catalyzes various N processes in soils in general (reviewed, e.g., by [128]) as well as in permafrost-affected soils (reviewed, e.g., by [53,58,59]). The microbial composition and activities of N cycling microorganisms, together with organic matter quantity and quality, determine the N availability of soils.…”

Section: Key Microbial N Processes Determining N Availability In Perm...mentioning

confidence: 99%

“…Studies of in-situ denitrification rates in permafrost-affected soils are rare (e.g., [112,204]) but have recently been reviewed [58]. Denitrifying communities of permafrost-affected soils remain largely unresolved to date, with one of the first characterizations of denitrifiers occurring in N hotspots of bare permafrost peatlands and sea animal-influenced soils (details see chapters below).…”

Section: Denitrificationmentioning

confidence: 99%

“…However, most of the nitrogen is firmly bound in soil organic matter (SOM) by tight N mineralizationimmobilization-turnover (MIT) or in the perennially frozen ground, therefore tundra ecosystems are generally described as severely N-limited [30,[43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Nitrogen limitation is enhanced by low internal N inputs due to low or even negative net N mineralization rates, including ammonification and nitrification under cold and wet conditions (summarized in [53,[57][58][59]) and low external N inputs due to biological N fixation (20-2000 mg m −2 y −1 , [53,[59][60][61]) combined with low atmospheric N deposition (<200-300 mg m −2 y −1 , [62,63]), and no external N fertilization. Recycled N accounts for over 95% in the Arctic tundra [47] and inhibited microbial inorganic N turnover [64,65].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, advances in microbial gene abundance and activity surveys over the last two decades have shown that N cycling microbes can be very abundant in both the seasonally thawing active layer and the long-term frozen permafrost, and that microorganisms actively drive N cycling (recently reviewed in [58,59]). At the same time, there is increasing evidence that permafrost-affected soils represent an important source of the potent greenhouse gas (GHG) nitrous oxide (N 2 O) [82], a strong ozone-depleting gas and the third most important GHG with a global warming potential of 298 times higher than that of CO 2 on a 100-year timescale [83].…”

Section: Introductionmentioning

confidence: 99%

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Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions

et al. 2022

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Permafrost-affected tundra soils are large carbon (C) and nitrogen (N) reservoirs. However, N is largely bound in soil organic matter (SOM), and ecosystems generally have low N availability. Therefore, microbial induced N-cycling processes and N losses were considered negligible. Recent studies show that microbial N processing rates, inorganic N availability, and lateral N losses from thawing permafrost increase when vegetation cover is disturbed, resulting in reduced N uptake or increased N input from thawing permafrost. In this review, we describe currently known N hotspots, particularly bare patches in permafrost peatland or permafrost soils affected by thermokarst, and their microbiogeochemical characteristics, and present evidence for previously unrecorded N hotspots in the tundra. We summarize the current understanding of microbial N cycling processes that promote the release of the potent greenhouse gas (GHG) nitrous oxide (N2O) and the translocation of inorganic N from terrestrial into aquatic ecosystems. We suggest that certain soil characteristics and microbial traits can be used as indicators of N availability and N losses. Identifying N hotspots in permafrost soils is key to assessing the potential for N release from permafrost-affected soils under global warming, as well as the impact of increased N availability on emissions of carbon-containing GHGs.

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Section: Key Microbial N Processes Determining N Availability In Perm...mentioning

confidence: 99%

Section: Denitrificationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions

et al. 2022

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Seasonal nitrogen fluxes of the Lena River Delta

Sanders

Fiencke

Fuchs

et al. 2021

Ambio

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The Arctic is nutrient limited, particularly by nitrogen, and is impacted by anthropogenic global warming which occurs approximately twice as fast compared to the global average. Arctic warming intensifies thawing of permafrost-affected soils releasing their large organic nitrogen reservoir. This organic nitrogen reaches hydrological systems, is remineralized to reactive inorganic nitrogen, and is transported to the Arctic Ocean via large rivers. We estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean by sampling in the Lena River and its Delta. We took water samples along one of the major deltaic channels in winter and summer in 2019 and sampling station in the central delta over a one-year cycle. Additionally, we investigate the potential release of reactive nitrogen, including nitrous oxide from soils in the Delta. We found that the Lena transported nitrogen as dissolved organic nitrogen to the coastal Arctic Ocean and that eroded soils are sources of reactive inorganic nitrogen such as ammonium and nitrate. The Lena and the Deltaic region apparently are considerable sources of nitrogen to nearshore coastal zone. The potential higher availability of inorganic nitrogen might be a source to enhance nitrous oxide emissions from terrestrial and aquatic sources to the atmosphere.

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Burkholderiaceae Are Key Acetate Assimilators During Complete Denitrification in Acidic Cryoturbated Peat Circles of the Arctic Tundra

Hetz

Horn

2021

Front. Microbiol.

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Cryoturbated peat circles (pH 4) in the Eastern European Tundra harbor up to 2 mM pore water nitrate and emit the greenhouse gas N2O like heavily fertilized agricultural soils in temperate regions. The main process yielding N2O under oxygen limited conditions is denitrification, which is the sequential reduction of nitrate/nitrite to N2O and/or N2. N2O reduction to N2 is impaired by pH < 6 in classical model denitrifiers and many environments. Key microbes of peat circles are important but largely unknown catalysts for C- and N-cycling associated N2O fluxes. Thus, we hypothesized that the peat circle community includes hitherto unknown taxa and is essentially unable to efficiently perform complete denitrification, i.e., reduce N2O, due to a low in situ pH. 16S rRNA analysis indicated a diverse active community primarily composed of the bacterial class-level taxa Alphaproteobacteria, Acidimicrobiia, Acidobacteria, Verrucomicrobiae, and Bacteroidia, as well as archaeal Nitrososphaeria. Euryarchaeota were not detected. 13C2- and 12C2-acetate supplemented anoxic microcosms with endogenous nitrate and acetylene at an in situ near pH of 4 were used to assess acetate dependent carbon flow, denitrification and N2O production. Initial nitrate and acetate were consumed within 6 and 11 days, respectively, and primarily converted to CO2 and N2, suggesting complete acetate fueled denitrification at acidic pH. Stable isotope probing coupled to 16S rRNA analysis via Illumina MiSeq amplicon sequencing identified acetate consuming key players of the family Burkholderiaceae during complete denitrification correlating with Rhodanobacter spp. The archaeal community consisted primarily of ammonia-oxidizing Archaea of Nitrososphaeraceae, and was stable during the incubation. The collective data indicate that peat circles (i) host acid-tolerant denitrifiers capable of complete denitrification at pH 4–5.5, (ii) other parameters like carbon availability rather than pH are possible reasons for high N2O emissions in situ, and (iii) Burkholderiaceae are responsive key acetate assimilators co-occurring with Rhodanobacter sp. during denitrification, suggesting both organisms being associated with acid-tolerant denitrification in peat circles.

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4 Microbial nitrogen cycling in permafrost soils: implications for atmospheric chemistry

Cited by 3 publications

References 0 publications

Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions

Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions

Seasonal nitrogen fluxes of the Lena River Delta

Burkholderiaceae Are Key Acetate Assimilators During Complete Denitrification in Acidic Cryoturbated Peat Circles of the Arctic Tundra

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