Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

Jiroušek, Martin; Hájek, Michal; Bragazza, Luca

doi:10.1016/j.envpol.2010.10.004

Cited by 39 publications

(48 citation statements)

References 35 publications

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“…The low N : P ratios of Sphagnum tissue of controls (around 10) indicate relative N limitation (Wang and Moore, 2014;Bragazza et al, 2004). However, under these eutrophic conditions with high N availability and high tissue N concentrations, low ratios rather seem to be an effect of high P concentrations (Jiroušek et al, 2011). Concentrations of N, P and K in Sphagnum tissue (including their microbial community) were all high or on the high end for Sphagnum in minerotrophic peatlands, particularly for P (Aerts et al, 1999;Lamers et al, 2000;Bragazza et al, 2004) (Table 3).…”

Section: Role Of P Availabilitymentioning

confidence: 99%

Symbiosis revisited: phosphorus and acid buffering stimulate N2 fixation but not Sphagnum 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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Section: Role Of P Availabilitymentioning

confidence: 99%

Symbiosis revisited: phosphorus and acid buffering stimulate N2 fixation but not Sphagnum growth

et al. 2017

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“…4b) may suggest P transport from the stem into the capitulum in all Sphagnum sections along the gradient and the importance of P recycling in these peatlands. We observed a larger N:P ratio in Acutifolia than Cuspidata sections, a trend also described by Jiroušek et al (2011). Assuming that the N:P ratio reflects limitations of these two nutrients, in general the hollow Sphagnum species were more P limited (N:P ratio > 16), whereas in the hummocks there may be co-limitation of N and P, though the pattern varied across the sites.…”

Section: Discussionmentioning

confidence: 45%

“…Atmospheric N deposition increases N content in Sphagnum mosses (Aerts et al 1992;Bragazza et al 2005;Granath et al 2009;Jiroušek et al 2011). Less is known about rates of atmospheric P deposition, which have a high degree of spatial variation (Tipping et al 2014) and are thus more difficult to assess in terms of their impact on Sphagnum P concentration.…”

Section: Introductionmentioning

confidence: 99%

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Variations in nitrogen, phosphorus, and δ¹⁵N in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada

Živković

Disney

Moore

2017

Botany

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We examined concentrations of nitrogen (N) and phosphorus (P) and δ 15 N value in Sphagnum sections Acutifolia and Cuspidata inhabiting hummocks and hollows from 8 bogs along a transect from ~45 to ~55 °N in Ontario/Quebec. The N concentration in Sphagnum declined from South to North, correlating with a decrease in atmospheric N deposition. Although the overall N concentration was larger in hollows than hummocks, the pattern was inconsistent across the sites.There was a proportionally larger decline in P concentration from South to North and an overall larger P concentration in hollows than hummocks, but there were inconsistent differences across the sites. The N:P ratio ranged from 12:1 to 29:1, driven primarily by the variation in P concentration. Ratios of N and P concentration in Sphagnum capitulum:stem averaged 1.2:1, suggesting nutrient resorption from stem to capitulum during growth; the ratio rose with increasing N and P concentration in the capitulum. The δ 15 N value of Sphagnum rose from ~-6‰in the South to ~-1‰ in the North, correlated with the decrease in Sphagnum N concentration and with a rise in water table. We interpret this to indicate a greater dependence on N 2 -fixation for N acquisition in the northern and wetter sites.

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“…But by comparing the N:P ratio (11.18±0.51) in our study with those from central-west and northern Europe [5, 47] and South America [23], we found that the discrepancy of low N:P ratio is mainly caused by relatively high P concentrations (1.81±0.11) rather than by low N concentrations. Possible explanations for the lower N:P ratios are that this region has suffered from disproportionate input of N and P, or that the two studied epiphytic bryophytes may be still N-limited despite high capitula N concentrations [57]. Therefore, it is more reasonable to use the N:P ratio, rather than the absolute concentration, to indicate the type of nutrient limitation in epiphytic bryophytes.…”

Section: Discussionmentioning

confidence: 99%

Physiological Responses of Two Epiphytic Bryophytes to Nitrogen, Phosphorus and Sulfur Addition in a Subtropical Montane Cloud Forest

et al. 2016

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Atmospheric depositions pose significant threats to biodiversity and ecosystem function. However, the underlying physiological mechanisms are not well understood, and few studies have considered the combined effects and interactions of multiple pollutants. This in situ study explored the physiological responses of two epiphytic bryophytes to combined addition of nitrogen, phosphorus and sulfur. We investigated the electrical conductivity (EC), total chlorophyll concentration (Chl), nutrient stoichiometry and chlorophyll fluorescence signals in a subtropical montane cloud forest in south-west China. The results showed that enhanced fertilizer additions imposed detrimental effects on bryophytes, and the combined enrichment of simulated fertilization exerted limited synergistic effects in their natural environments. On the whole, EC, Chl, the effective quantum yield of photosystem II (ΦPSII) and photochemical quenching (qP) were the more reliable indicators of increased artificial fertilization. However, conclusions on nutrient stoichiometry should be drawn cautiously concerning the saturation uptake and nutrient interactions in bryophytes. Finally, we discuss the limitations of prevailing fertilization experiments and emphasize the importance of long-term data available for future investigations.

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Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

Cited by 39 publications

References 35 publications

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

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

Variations in nitrogen, phosphorus, and δ¹⁵N in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada

Physiological Responses of Two Epiphytic Bryophytes to Nitrogen, Phosphorus and Sulfur Addition in a Subtropical Montane Cloud Forest

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Nutrient stoichiometry in Sphagnum along a nitrogen deposition gradient in highly polluted region of Central-East Europe

Cited by 39 publications

References 35 publications

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

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

Variations in nitrogen, phosphorus, and δ15N in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada

Physiological Responses of Two Epiphytic Bryophytes to Nitrogen, Phosphorus and Sulfur Addition in a Subtropical Montane Cloud Forest

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

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

Variations in nitrogen, phosphorus, and δ¹⁵N in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada