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. 2013 Jun 17:4:150.
doi: 10.3389/fmicb.2013.00150. eCollection 2013.

Moss-cyanobacteria associations as biogenic sources of nitrogen in boreal forest ecosystems

Kathrin Rousk  1 , Davey L Jones, Thomas H Deluca
Affiliations

Moss-cyanobacteria associations as biogenic sources of nitrogen in boreal forest ecosystems

Kathrin Rousk et al. Front Microbiol. .

Abstract

The biological fixation of atmospheric nitrogen (N) is a major pathway for available N entering ecosystems. In N-limited boreal forests, a significant amount of N2 is fixed by cyanobacteria living in association with mosses, contributing up to 50% to the total N input. In this review, we synthesize reports on the drivers of N2 fixation in feather moss-cyanobacteria associations to gain a deeper understanding of their role for ecosystem-N-cycling. Nitrogen fixation in moss-cyanobacteria associations is inhibited by N inputs and therefore, significant fixation occurs only in low N-deposition areas. While it has been shown that artificial N additions in the laboratory as well as in the field inhibit N2 fixation in moss-cyanobacteria associations, the type, as well as the amounts of N that enters the system, affect N2 fixation differently. Another major driver of N2 fixation is the moisture status of the cyanobacteria-hosting moss, wherein moist conditions promote N2 fixation. Mosses experience large fluctuations in their hydrological status, undergoing significant natural drying and rewetting cycles over the course of only a few hours, especially in summer, which likely compromises the N input to the system via N2 fixation. Perhaps the most central question, however, that remains unanswered is the fate of the fixed N2 in mosses. The cyanobacteria are likely to leak N, but whether this N is transferred to the soil and if so, at which rates and timescales, is unknown. Despite our increasing understanding of the drivers of N2 fixation, the role moss-cyanobacteria associations play in ecosystem-N-cycling remains unresolved. Further, the relationship mosses and cyanobacteria share is unknown to date and warrants further investigation.

Keywords: N-cycle; acetylene reduction; boreal biome; bryophytes; global change; nitrogenase; symbioses.

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Figures

Figure 1
Figure 1
A simplified overview of the N-cycle in boreal forests, including N2 fixation in moss carpets as a candidate for filling the N-gap in boreal ecosystems. Boxes and arrows in gray indicate less common or less important pathways and sources of N in the boreal forest.
Figure 2
Figure 2
(A) A late-succession boreal forest site in Northern Sweden with an open canopy and a moss-dominated understory. Mosses, in particular feather mosses like Pleurozium schreberi and Hylocomium splendens, cover 70–100% of the ground in boreal forests. Photo by K. Rousk. (B) A section of a Pleurozium schreberi-leaf at ×100 magnification under an UV-fluorescence microscope. Coiled chains of Nostoc spp. are seen in bright red. The moss-cyanobacteria association is assumed to be mutualistic, however, no attempts have been made so far to identify the relationship moss and cyanobacteria share. Photo by K. Rousk.
Figure 3
Figure 3
Acetylene reduction rates (μmol m−2d−1) in Pleurozium schreberi at one late (open bars) and one early (filled bars) succession forest site in northern Sweden in response to P additions (5 kg P ha−1 yr−1 as NaH2PO4). Shown are acetylene reduction rates measured 1 and 5 years after the P additions. Phosphorus was applied annually to 10 replicate 1.0 m2 plots in four doses over the course of the summer. Distilled water was applied to the control plots. Mean values (n = 10) and +1 SE are given, **represents significant at P < 0.05 and n.s. represents not significant as determined by a One-Way ANOVA. Experimental design, sampling, and data analyses are reported for year-one in Zackrisson et al. (2004).
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References

    1. Ackermann K. (2013). Nitrogen Dynamics in Boreal Forests: a Feather Moss' Perspective. Ph.D. thesis, Bangor: Bangor University, 1–162
    1. Ackermann K., Zackrisson O., Rousk J., Jones D. L., DeLuca T. H. (2012). N2 fixation in feather mosses is a sensitive indicator of N deposition in boreal forests. Ecosystems 15, 986–998 10.1007/s10021-012-9562-y - DOI
    1. Adams D. G., Duggan P. S. (2008). Cyanobacteria-bryophyte symbioses. J. Exp. Bot. 59, 1047–1058 10.1093/jxb/ern005 - DOI - PubMed
    1. Aldous A. R. (2002). Nitrogen retention by Sphagnum mosses: response to atmospheric nitrogen deposition. Can. J. Bot. 80, 721–731 10.1139/b02-054 - DOI
    1. Ayres E., Van der Wal R., Sommerkorn M., Bardgett R. D. (2006). Direct uptake of soil nitrogen by mosses. Biol. Lett. 2, 286–288 10.1098/rsbl.2006.0455 - DOI - PMC - PubMed

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