Moss-specific changes in nitrogen fixation following two decades of warming, shading, and fertilizer addition

Sørensen, Pernille Lærkedal; Lett, Signe; Michelsen, Anders

doi:10.1007/s11258-012-0034-4

Cited by 59 publications

(58 citation statements)

References 45 publications

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“…2). As in other subarctic heaths, grasses, and forbs had low cover and did not respond significantly, even after two decades of warming (Sorensen et al 2012). These responses are consistent with a global assessment of experimental climate warming on tundra vegetation, which has shown that shrubs increase with warming only where ambient temperature is highest, i.e., in the Subarctic and Low Arctic, whereas graminoids increase primarily in high arctic sites (Elmendorf et al 2012).…”

Section: Plant Functional Types Nutrient Availability and Responsivsupporting

confidence: 83%

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Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

Michelsen

Rinnan

Jonasson

2012

AMBIO

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Section: Plant Functional Types Nutrient Availability and Responsivsupporting

confidence: 83%

“…3), probably due to the relatively high P content in birch litter (Sorensen and Michelsen 2011), the very high nutrient input with NPK fertilizer strongly reduced N 2 fixation at the mesic heath (Fig. 3) (Sorensen et al 2012). If N input increases due to deposition, N 2 fixation is likely to decrease.…”

Section: Nitrogen Cycling In Strongly N-limited Ecosystemsmentioning

confidence: 96%

Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

Michelsen

Rinnan

Jonasson

2012

AMBIO

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“…This warming is likely to have a positive effect on forest floor cyanobacteria growth and N fixation as long as temperatures remain within or below the enzymatic optimum temperature for N fixation (between 20 • C and 30 • C) [14]. With that said, increases in temperature might have a negative effect on moss host plants that could reduce forest-wide densities of N fixing cyanobacteria [11,30,31], thus extrapolating the stimulatory effects of increased temperature and CO 2 on forest floor, moss-associated cyanobacterial N fixation to the forest level is difficult [32]. Another reason for this is because the fate of the N fixed by terrestrial cyanobacteria is still unclear.…”

Section: Discussionmentioning

confidence: 99%

“…(2,30) 9.77 <0.001 CO 2 × temperature (2,30) 4.71 0.017 time (6,180) 53.83 <0.001 time × CO 2 (6,180) 1.41 0.204 time × temperature (12,180) 30.95 <0.001 time × CO 2 × temperature (12,180) 2.34 0.008…”

Section: Experiments 2: N Fixation Under Elevated Warming and Atmosphementioning

confidence: 99%

Elevated Atmospheric CO2 and Warming Stimulates Growth and Nitrogen Fixation in a Common Forest Floor Cyanobacterium under Axenic Conditions

Lindo

Griffith

2017

Forests

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Abstract:The predominant input of available nitrogen (N) in boreal forest ecosystems originates from moss-associated cyanobacteria, which fix unavailable atmospheric N 2 , contribute to the soil N pool, and thereby support forest productivity. Alongside climate warming, increases in atmospheric CO 2 concentrations are expected in Canada's boreal region over the next century, yet little is known about the combined effects of these factors on N fixation by forest floor cyanobacteria. Here we assess changes in N fixation in a common forest floor, moss-associated cyanobacterium, Nostoc punctiforme Hariot, under elevated CO 2 conditions over 30 days and warming combined with elevated CO 2 over 90 days. We measured rates of growth and changes in the number of specialized N 2 fixing heterocyst cells, as well as the overall N fixing activity of the cultures. Elevated CO 2 stimulated growth and N fixation overall, but this result was influenced by the growth stage of the cyanobacteria, which in turn was influenced by our temperature treatments. Taken together, climate change factors of warming and elevated CO 2 are expected to stimulate N 2 fixation by moss-associated cyanobacteria in boreal forest systems.

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“…In temperate and subtropical regions, nutrient enrichment tends to increase algal growth and alter species composition (Goldsborough and Robinson 1996), with consequences for ecosystem function (Richardson 2010). Similar information is not available for algae in northern peatlands, where nutrient levels are typically low (Sorensen et al 2012) and elevated nutrient levels are likely to coincide with warmer temperatures. Since many of the enzymatic reactions involved in photosynthesis are temperature-dependent (Davison 1991), warmer temperatures may enhance the influence of elevated nutrient levels on algal production in northern ecosystems where low mean annual temperatures tend to constrain metabolic activity (Rosa et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Nutrients and temperature interact to regulate algae and heterotrophic bacteria in an Alaskan poor fen peatland

Wyatt

Bange

Fitzgibbon

et al. 2015

Can. J. Fish. Aquat. Sci.

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Permafrost thaw associated with warmer temperatures is expected to elevate nutrient levels in northern aquatic ecosystems, including peatlands. To evaluate these effects on algae and heterotrophic bacteria, we manipulated nutrients (nitrogen (N) and phosphorus (P)) and temperature (ambient and warmed) in a factorial design using nutrient diffusing substrates inside warming chambers in an Alaskan peatland. After 16 days, there was no effect of warming on the abundance of algae or heterotrophic bacteria in the absence of nutrient enrichment. Algal production and bacterial biomass were substantially elevated by N with and without P (NP and N, respectively), independent of warming. Warming significantly enhanced the effect of nutrient enrichment on the abundance of algae and heterotrophic bacteria compared with ambient temperatures. Rates of N fixation increased with the presence of heterocyst-forming cyanobacteria, which represented a greater proportion of algal taxonomic composition in the absence of N enrichment in both ambient and warmed conditions. Our results indicate that warmer temperatures and nutrient enrichment will elevate algal and heterotrophic metabolism in northern peatlands, and the magnitude of increase will depend on the combination of nutrients available during periods of inundation.Résumé : La fonte du pergélisol associée à la hausse des températures devrait entraîner une augmentation des concentrations de nutriments dans les écosystèmes aquatiques nordiques, notamment les tourbières. Afin d'évaluer ces effets sur les algues et les bactéries hétérotrophes, nous avons manipulé les nutriments (azote (N) et phosphore (P)) et la température (ambiante et élevée) dans un schéma factoriel faisant appel à des substrats qui diffusent les nutriments, à l'intérieur d'enceintes de réchauffe-ment dans une tourbière alaskienne. Après 16 jours, il n'y avait aucun effet du réchauffement sur l'abondance d'algues ou de bactéries hétérotrophes en l'absence d'enrichissement en nutriments. La production d'algues et la biomasse de bactéries étaient significativement élevées par l'enrichissement en N avec ou sans P (NP et N, respectivement), indépendamment du réchauffe-ment. Ce dernier rehaussait de manière significative l'effet de l'enrichissement en nutriments sur l'abondance d'algues et de bactéries hétérotrophes par rapport aux températures ambiantes. Les taux de fixation de N augmentaient en présence de cyanobactéries formant des hétérocystes, qui représentaient une proportion plus importante de la composition taxinomique des algues en l'absence d'enrichissement en N à des températures tant ambiantes qu'élevées. Nos résultats indiquent que des températures plus élevées et l'enrichissement en nutriments entraîneront une augmentation du métabolisme algal et hétéro-trophe dans les tourbières nordiques, l'ampleur de cette augmentation dépendant de la combinaison de nutriments disponibles durant les périodes d'inondation. [Traduit par la Rédaction]

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Moss-specific changes in nitrogen fixation following two decades of warming, shading, and fertilizer addition

Cited by 59 publications

References 45 publications

Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

Two Decades of Experimental Manipulations of Heaths and Forest Understory in the Subarctic

Elevated Atmospheric CO2 and Warming Stimulates Growth and Nitrogen Fixation in a Common Forest Floor Cyanobacterium under Axenic Conditions

Nutrients and temperature interact to regulate algae and heterotrophic bacteria in an Alaskan poor fen peatland

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