Nitrogen Fixation in a Subarctic Mire

Granhall, Ulf; Selander, Hans

doi:10.2307/3543247

Cited by 111 publications

(70 citation statements)

References 14 publications

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“…Our areal estimations for fen stages and fen-bog transition are within the wide range of the admittedly few estimates available for Sphagnum-associated N 2 fixation in temperate, boreal, and subarctic ecosystems. These range from 0.1-6.4 g of N·m −2 ·y −1 for fens (11,16,24) and 0.1-1 g·m −2 ·y −1 for bogs (9,25). Nevertheless, our estimates may be rough because of the large SEs and the extrapolation over time:…”

Section: Resultsmentioning

confidence: 67%

“…However, the growth of Sphagnum mosses in peatlands is often N limited, at least under low atmospheric N deposition (5), so biological fixation of atmospheric N 2 , i.e., the biological conversion of dinitrogen to plant-available ammonium, may stimulate moss growth (6). Under low atmospheric N deposition, moss-associated cyanobacteria have been shown to play an important role in the N budget in forests (7,8) and peatlands (9), where N 2 fixation is favored by moist conditions. In peatlands, however, molecular analyses of genes that encode nitrogenase reductase proteins (nifH) in Sphagnum mosses have indicated that mossassociated N 2 fixers (diazotrophs) belong mainly to the metabolically diverse class Alphaproteobacteria (10), which includes phototrophic, heterotrophic, and methanotrophic genera.…”

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confidence: 99%

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Methanotrophy induces nitrogen fixation during peatland development

Larmola

Leppänen

Tuittila

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

164

169

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Nitrogen (N) accumulation rates in peatland ecosystems indicate significant biological atmospheric N 2 fixation associated with Sphagnum mosses. Here, we show that the linkage between methanotrophic carbon cycling and N 2 fixation may constitute an important mechanism in the rapid accumulation of N during the primary succession of peatlands. In our experimental stable isotope enrichment study, previously overlooked methane-induced N 2 fixation explained more than one-third of the new N input in the younger peatland stages, where the highest N 2 fixation rates and highest methane oxidation activities co-occurred in the water-submerged moss vegetation.P eat-accumulating wetlands, i.e., peatlands, store approxi-

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Section: Resultsmentioning

confidence: 67%

mentioning

confidence: 99%

Methanotrophy induces nitrogen fixation during peatland development

Larmola

Leppänen

Tuittila

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

164

169

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“…All Rights Reserved. [Basilier et al, 1978] TU 1.0-6.4 (4) [Crittenden, 1975] TU 0.0062-0.17 [Forman and Dowden, 1977] TU 0.022-0.18 (3) b [Granhall and Selander, 1973] TU 0.16-9.4 (2) [Gunther, 1989] TU 0.0025-0.01 (3) [Henry and Svoboda, 1986] TU 0.085-0.1 (2) [Kallio, 1975] TU 0.15-0.38 (3) [DeLuca et al, 2002] BO-F 0.17 [Gunther, 1989] BO-F 0.005-0.045 (2) [Huss-Danell, 1977] BO-F 0.1 [Lagerström et al, 2007] BO-F 0.05-0.2 (3) [Zackrisson et al, 2004] BO-F 0.025-0.15 (3) b [Zackrisson et al, 2009] BO-F 0.16 [Antoine, 2004] TE-C 0.15-1.65 (5) [Brown and Dalton, 2002] TE-C 0.2 [Denison, 1973] TE-C 0.59 b [Denison, 1979] TE-C 0.4 [Granhall and Lindberg, 1978] TE-C 0.035 [Green et al, 1980] TE-C 0.5 b [Pike, 1978] TE-C 0.45 [Sucoff, 1979] TE-C 0.006-0.24 (4) [Belnap, 2002] [Zhao et al, 2010] DE 0.4 [Crews et al, 2001] TR-F 0.1-0.2 (3) [Cusack et al, 2009] TR-F 0.38 TR-F 0.02-0.045 (3) [Matzek and Vitousek, 2003] TR-F 0.008-0.06 (6) [Forman, 1975] TR-C 0.48 [Freiberg, 1998] TR-C 0.35 b [Matzek and Vitousek, 2003] TR-C 0.004-0.04 (6) a Biomes are abbreviated as follows: TU = tundra, BO-F = boreal forest floor, TE-C = temperate evergreen canopy, DE = desert, TR-F = tropical rainforest floor, and TR-C = tropical rainforest canopy. Some studies provide more than one observed value (e.g., due to different habitats).…”

Section: Chemical Weatheringmentioning

confidence: 99%

Estimating impacts of lichens and bryophytes on global biogeochemical cycles

Porada

Weber

Elbert

et al. 2014

Global Biogeochemical Cycles

124

107

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Lichens and bryophytes may significantly affect global biogeochemical cycles by fixation of nitrogen and biotic enhancement of surface weathering rates. Most of the studies suggesting these effects, however, are either conceptual or rely on upscaling of regional estimates to obtain global numbers. Here we use a different method, based on estimates of net carbon uptake, to quantify the impacts of lichens and bryophytes on biogeochemical cycles at the global scale. We focus on three processes, namely, nitrogen fixation, phosphorus uptake, and chemical weathering. Our estimates have the form of potential rates, which means that we quantify the amount of nitrogen and phosphorus needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, we use potential phosphorus uptake on bare ground to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tg yr −1 and for phosphorus it ranges from 0.46 to 4.6 Tg yr −1 . Estimates of chemical weathering are between 0.058 and 1.1 km 3 yr −1 of rock. These values seem to have a realistic order of magnitude, and they support the notion that lichens and bryophytes have the potential to play an important role for biogeochemical cycles.

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“…These N 2 fixation rates were also converted to rates of N fixed per unit area with bulk density data from the field (dry weight of the upper 2 cm of each species in a 10 cm 2 plot (N = 4 replicates)). Fixation rates per hectare per year were calculated assuming N 2 fixation activity throughout the growing season (Rousk et al, 2015) during a growing season of around 250 days for peatlands in the Northern Hemisphere with mild winters (Helfter et al, 2015;Zhu et al, 2012) and corrected for an average seasonal temperature of 13 • C, assuming a Q 10 of 3 (Kravchenko and Doroshenko, 2003;Granhall and Selander, 1973;Alexander and Schell, 1973). Total P and potassium (K) concentrations were determined in digestates of dried and ground Sphagnum-microorganism tissue.…”

Section: N 2 Fixation Rates and Elemental Composition Of Sphagnummentioning

confidence: 99%

Symbiosis revisited: phosphorus and acid buffering stimulate N<sub>2</sub> fixation but not <i>Sphagnum</i> growth

et al. 2017

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Abstract. In pristine Sphagnum-dominated peatlands, (di)nitrogen (N 2 ) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha −1 yr −1 ), we found that diazotrophic activity (as measured by 15−15 N 2 labeling) was still present at a rate of 40 nmol N gDW −1 h −1 . This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum hosts, in which a sheltered environment apparently outweighs the less favorable environmental conditions. We conclude that microbial activity is still nitrogen limited under eutrophic conditions because dissolved nitrogen is being monopolized by Sphagnum. Moreover, the fact that diazotrophic activity can significantly be upregulated by increased phosphorus addition and acid buffering, while Sphagnum spp. do not benefit, reveals remarkable differences in optimal conditions for both symbiotic partners and calls into question the regulation of nitrogen fixation by Sphagnum under these eutrophic conditions. The high nitrogen fixation rates result in high additional nitrogen loading of 6 kg ha −1 yr −1 on top of the high nitrogen deposition in these ecosystems.

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Nitrogen Fixation in a Subarctic Mire

Cited by 111 publications

References 14 publications

Methanotrophy induces nitrogen fixation during peatland development

Methanotrophy induces nitrogen fixation during peatland development

Estimating impacts of lichens and bryophytes on global biogeochemical cycles

Symbiosis revisited: phosphorus and acid buffering stimulate N<sub>2</sub> fixation but not <i>Sphagnum</i> growth

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Nitrogen Fixation in a Subarctic Mire

Cited by 111 publications

References 14 publications

Methanotrophy induces nitrogen fixation during peatland development

Methanotrophy induces nitrogen fixation during peatland development

Estimating impacts of lichens and bryophytes on global biogeochemical cycles

Symbiosis revisited: phosphorus and acid buffering stimulate N&lt;sub&gt;2&lt;/sub&gt; fixation but not &lt;i&gt;Sphagnum&lt;/i&gt; growth

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Symbiosis revisited: phosphorus and acid buffering stimulate N<sub>2</sub> fixation but not <i>Sphagnum</i> growth