Fen Species Research Articles

Plug method allows measurement of apical and lateral growth of fen brown mosses

ABSTRACT Introduction: A reliable method for measuring brown moss production helps us to understand the functioning of fen peatlands and to quantify their peat formation rate. However, traditional methods based on height increment are not suitable for measuring the growth rate of brown mosses with numerous lateral branches. Methods: The growth rate of common brown moss species in temperate and boreal fens was measured using two methods: (i) the marking method – a moss shoot was marked with oil paint and its growth increment measured from the mark (in the laboratory and in the field); and (ii) the plug method – a fragment of a moss colony was ‘plugged' (i.e. cored), weighed and replanted in a small basket for a year, then weighed again; a similar and bottomless basket was fixed in the moss colony as a control. Key results and discussion: Despite promising laboratory results, the marking method gave low shoot survival in the field, probably due to the restriction of external water transport along the shoots. No differences in shoot elongation were found between the plug method and the control. The plug method comprises the measurement of both apical and lateral growth, and the authors of the present study therefore recommend it for measuring the growth of brown mosses with numerous lateral branches. Considering only the elongation of the top shoots leads to an underestimation of growth by 50% and consequently to an underestimation of the peat-forming potential of brown mosses.

Is an infrequent moss species a weaker competitor? Experiment with three fen species

Overexploitation of mires leads to habitat degradation for many species, and the greatest impact is on species with specific demands or restricted distribution. Three fen species – with overlapping ecological demands, but different distribution frequency – were included in the study, to elucidate whether a less common species could be a weaker competitor under certain ecological conditions compared to other moss species inhabiting the same habitat. We grew the species under conditions that imitated changes in fen communities caused by human activities: water level drop, temperature rise, and shade increase. The species were grown as monocultures and as mixtures in distilled water, to exclude the influence of minerals and nutrients. Although all the species reacted to the different environmental conditions in a similar way, they grew better in monocultures. The shoot elongation of Hamatocaulis vernicosus, a less frequent species, even exceeded that of the two more common species included in the study: Calliergonella cuspidata and Scorpidium cossonii. Pairwise comparisons of shoot elongation showed the success of H. vernicosus. Our results proved that H. vernicosus is not a weaker competitor than other fen mosses in nutrient‐poor conditions, and can defeat the others in cool and flooded conditions. Restoration and conservation of such fen habitats is important to protect the populations of this species.

Carbon-coated Fe3C derived from MIL-100 growth on covalent triazine framework in situ as an efficient ORR catalysts

Fe-based N-doped carbon materials have become the most potential electrocatalysts to replace noble metal catalysts in oxygen reduction reaction (ORR) due to their wide availability, affordability, and high catalytic activity. In this study, novel Fe-based Fe3C nanoparticles encapsulated by N-doped mesopores carbon were prepared via a cost-effective method using MIL-100(Fe) growth on CTF as the precursor. Benefit from the compositional and structural synergistic effect of metal and substrate, the highly dispersed core–shell Fe/Fe3C@C catalyst shows excellent ORR activity and stability with an onset potential of 1.016 V and a half-wave potential of 0.831 V, which is comparable with commercial Pt/C. Meanwhile, the interfacial electron transfer between Fe3C nanoparticles and neighboring Fe-N species, as well as the porous carbon architecture, contribute to the excellent ORR performance. The CTF-derived synthetic enhances ORR activity strategy inspires new perspectives to develop Fe-based composites as high-efficiency ORR electrocatalysts.

The synthesis of iron-nitrogen sites embedded in electrospun carbon nanofibers with an excellent oxygen reduction reaction activity in alkaline/acidic media

Metal-nitrogen carbon catalysts have received great attention in the field of gas-evolving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion paths. A solution of porphyrin iron, g-C3N4 and polyacrylonitrile in N,N-dimethylformamide was sonicated and electrospun into doped polyacrylonitrile nanofibers (NFs), and the NFs were then stabilized and carbonized at 900 °C to prepare Fe-N/CNF catalyst for oxygen reduction reaction (ORR). It was found that the addition of g-C3N4 to the electrospinning precursor led to the formation of abundant Fe-N species in Fe3+ and Fe2+ valence states, while Fe3C nanoparticles were formed without adding g-C3N4. Compared to Fe3C/CNF prepared without g-C3N4, the Fe-N/CNF catalyst presents an 4e− improved oxygen reduction reaction activity in both alkaline and acidic media. Furthermore, as a cathode in Zn-air batteries, the Fe-N/CNF catalyst exhibits high performance with an open-circuit voltage of 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh g-1. This work suggests a way to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.

Fe species anchored N, S-doped carbon as nonprecious catalyst for boosting oxygen reduction reaction

Although metal-organic frameworks (MOFs) derived nonprecious catalysts for oxygen reduction reaction (ORR) have been intensively investigated, biological metal organic frameworks (Bio-MOF) derived ORR catalysts are rarely explored. Herein, for the first time, Bio-MOF-100 derived Fe species embedded N, S-doped carbon (Fe@NSC) is prepared by a simple solution soaking and pyrolysis. The Fe@NSC catalyst shows superior ORR performance with a large half-wave potential of 0.87 V, excellent methanol resistance, and exceptional long-term durability, which even surpasses the benchmark Pt/C catalyst. The brilliant ORR catalytic activity of Fe@NSC is due to its unique nanoarchitecture: more than one type of active constituents (Fe nanoparticles and Fe-N species) anchored N, S-doped carbon skeleton provides a high intrinsic catalytic activity; the nanoporous carbon matrix with a large specific surface area (1130.97 cm2 g−1) interconnected by in-situ grown carbon nanotubes with high conductivity can not only guarantee excellent mass transfer but also facilitate electron transfer. This research presents an approach to rationally design and facilely synthesize Bio-MOF-based ORR catalyst and demonstrates that Bio-MOF-based ORR catalysts are promising for efficient and stable oxygen reduction.

Competitive Non-Radical Nucleophilic Attack Pathways for NH3 Oxidation and H2 O Oxidation on Hematite Photoanodes.

The sluggish H2 O oxidation kinetics on photoanodes severely obstructs the overall solar-to-energy efficiency of photoelectrochemical (PEC) cells. Herein, we find a 10 to 55-fold increase of photocurrent by conducting ammonia oxidation reaction (AOR) on hematite (α-Fe2 O3 ) photoanodes under near-neutral pH (9-11) and moderate applied potentials (1.0-1.4 VRHE ) compared to H2 O oxidation. By rate law analysis and operando spectroscopic studies, we confirm the non-radical nucleophilic attack of NH3 molecules on high-valent surface Fe-O species (e.g., FeIV =O) and Fe-N species that produces NOx - and N2 , respectively, which overwhelms the nucleophilic attack of H2 O on surface FeIV =O and contributes to a high Faradaic efficiency of above 80 % for AOR. This work reveals a novel non-radical nucleophilic attack strategy, which is significantly different from the conventional indirect radical-mediated AOR mechanism, for the rational design of high-performance AOR photoelectrocatalysts.

High nutrient loads hinder successful restoration of natural habitats in freshwater wetlands

Restoration of natural processes in ecosystems is key to mitigate the biodiversity crisis. Here, we evaluate 20 Danish stream‐valley restoration projects—mainly by rewetting—in terms of successful restoration of natural wetland habitats. We used quadratic discriminant analysis and generalized linear models to compare 80 vegetation plots from the restoration projects with >60,000 natural or semi‐natural wetland reference plots. We modeled the influence of time since restoration, grazing, rewetting, and nutrient availability on (1) the probability that study plots belong to natural habitats and (2) their richness of high‐quality‐habitat indicator species. The probability of a restored wetland having developed into a natural wetland habitat—such as an alkaline fen—was generally below 10%. Also, we found only half as many indicator species in restored wetlands than in reference wetlands and we demonstrated that the number of characteristic alkaline fen species did not deviate from what could be expected under the prevailing nutrient conditions. We found a negative effect of soil nutrient availability on the number of high‐quality‐habitat indicator species and the lowest probability of plots being natural wetlands in the most nutrient rich plots. The effect of grazing was only positive in the first years after restoration and only in the most nutrient rich plots, while the effect of rewetting sites to historical hydrological conditions was generally negative. Our findings suggest that unnaturally high nutrient availability is probably the core limiting factor for successful restoration of natural wetlands and their associated plant diversity.

Peroxymonosulfate activation by Fe-N-S co-doped tremella-like carbocatalyst for degradation of bisphenol A: Synergistic effect of pyridine N, Fe-Nx, thiophene S

Bisphenol A (BPA) has received increasing attention due to its long-term industrial application and persistence in environmental pollution. Iron-based carbon catalyst activation of peroxymonosulfate (PMS) shows a good prospect for effective elimination of recalcitrant contaminants in water. Herein, considering the problem about the leaching of iron ions and the optimization of heteroatoms doping, the iron, nitrogen and sulfur co-doped tremella-like carbon catalyst (Fe-NS@C) was rationally designed using very little iron, S-C3N4 and low-cost chitosan (CS) via the impregnation-calcination method. The as-prepared Fe-NS@C exhibited excellent performance for complete removal of BPA (20 mg/L) by activating PMS with the high kinetic constant (1.492 min−1) in 15 min. Besides, the Fe-NS@C/PMS system not only possessed wide pH adaptation and high resistance to environmental interference, but also maintained an excellent degradation efficiency on different pollutants. Impressively, increased S-C3N4 doping amount modulated the contents of different N species in Fe-NS@C, and the catalytic activity of Fe-NS@C-1-x was visibly enhanced with increasing S-C3N4 contents, verifying pyridine N and Fe-Nx as main active sites in the system. Meanwhile, thiophene sulfur (C-S-C) as active sites played an auxiliary role. Furthermore, quenching experiment, EPR analysis and electrochemical test proved that surface-bound radicals (·OH and SO4⋅−) and non-radical pathways worked in the BPA degradation (the former played a dominant role). Finally, possible BPA degradation route were proposed. This work provided a promising way to synthesize the novel Fe, N and S co-doping carbon catalyst for degrading organic pollutants with low metal leaching and high catalytic ability.

Fen ecohydrologic trajectories in response to groundwater drawdown with an edaphic feedback.

Fens are high conservation value ecosystems that depend on consistent discharge of groundwater that saturates the near surface for most of the growing season. Reduced groundwater inputs can result in losses of native diversity, decreases in rare-species abundance and increased invasion by non-native species. As such, fen ecosystems are known to be particularly susceptible to changes in groundwater conditions including reduction in water levels due to nearby groundwater pumping. However, research is lacking on whether floristic degradation is influenced by feedbacks between hydrology and soil properties. We present a model of an archetype hillslope fen that couples a hydrological niche model with a variably saturated groundwater flow model to predict changes in vegetation composition in response to different groundwater drawdown scenarios. The model explores a potential edaphic feedback through the use of an observed relationship between fen floristic quality and soil/peat water retention characteristics that is attenuated with separate edaphic and floristic memory terms representing lags in biophysical responses to dewatering. Model parameters were determined based on data collected from six fens in Wisconsin under various states of degradation. We observed different water retention characteristics between sites that were minimally impacted versus degraded that are likely due to peat decomposition, oxidation and compaction at the degraded sites. These characteristics were also correlated with floristic quality. The results reveal a complex response to drawdown where changes in peat hydraulic properties following dewatering lead to even drier conditions and further shifts away from typical fen species.

In-situ coupling FeN nanocrystals with Fe/Fe3C nanoparticles to N-doped carbon nanosheets for efficient oxygen electrocatalysis

Hetero-nanoparticles encapsulated in nitrogen-doped carbon show promising potential application in oxygen reduction reaction (ORR). Herein, a covalent-organic frameworks (COFs) based composite with FeN species and Fe/Fe3C nanoparticles embedded in N-doped carbon nanosheets (Fe/Fe3C@FeN-Cs) has been successfully synthesized by an in-situreduction of pre-designed Fe-N2-O2 units. Benefit from the compositional and structural synergistic effect, the optimized Fe/Fe3C@FeN-C-900 displays excellent ORR activity in both acidic (E1/2 = 0.77 V) and alkaline (E1/2 = 0.88 V) electrolytes, which are comparable and even superior to the benchmark Pt/C. Impressively, the maximum power density of fuel cell using Fe/Fe3C@FeN-C-900 as cathode catalyst reaches 408 mW cm−2. Moreover, the Fe/Fe3C@FeN-C-900-drived rechargeable zinc-air batteries (ZABs) deliver a higher power density (156.8 mW cm−2), larger specific capacity (775 mA h g−1) and better cycling stability (270 cycles) as compared with the state-of-the-art Pt/C counterpart. Theinterfacial electron transfer between Fe/Fe3C nanoparticles and neighboring FeN species, as well as the porous carbon architecture contribute to the excellent ORR performance of Fe/Fe3C@FeN-C-900, resulting in the easily adsorption/activation of O2 and accelerated ORR kinetics because of the fast mass transfer. The COF-derived synthetic strategy inspires new perspectives to develop hetero-nanoparticle composites as high-efficiency ORR electrocatalysts for the economical-practical energy conversion devices.

Rationally-designed sandwiched nanostructures boosting Fe-N based catalysts toward efficient oxygen reduction electrocatalysis in acidic medium

The development of acidic-available noble-metal-free oxygen reduction reaction (ORR) catalysts with high activity and good long-term durability is of significant importance for efficient proton exchange membrane fuel cells, but is still very challenging. Herein, we develop originally a facile wet-chemical-adsorption, pyrolysis and post-etching strategy to effectively intercalate Fe clusters among two nitrogen-doped carbon (NC) layers, forming unique hollow spherical nanostructures with sandwiched NC/Fe/NC shells as an active ORR catalyst. Thanks to the sandwiched nanostructure and the active Fe-N species, this as-prepared hollow sandwiched NC/Fe/NC catalyst could present superior ORR activity in an acidic medium, with a nice onset potential of 0.92 V and decent diffusion-limited current density of ~5.1 mA/cm2. The NC/Fe/NC catalyst manifests strong methanol tolerance and outstanding durability during a long-term acidic ORR operation, being a promising alternative to Pt-based catalysts toward efficient proton exchange membrane fuel cells. Synchrotron radiation characterizations and X-ray photoemission spectroscopy reveal at the atomic-level that the abundant robust Fe–N bonds presented in the sandwiched shells of hollow NC/Fe/NC spherical catalyst contribute substantially to high electrochemical activity and superior corrosion-resistance for efficient 4e¯ ORR in acidic electrolyte.

Recent Lateral Expansion of Sphagnum Bogs Over Central Fen Areas of Boreal Aapa Mire Complexes

We investigated recent changes in spatial patterning of fen and bog zones in five boreal aapa mire complexes (mixed peatlands with patterned fen and bog parts) in a multiproxy study. Comparison of old (1940–1970s) and new aerial images revealed decrease of flarks (wet hollows) in patterned fens by 33–63% in middle boreal and 16–42% in northern boreal sites, as lawns of bog Sphagnum mosses expanded over fens. Peat core transects across transformed areas were used to verify the remote sensing inference with stratigraphic analyses of macrofossils, hyperspectral imaging, and age-depth profiles derived from 14C AMS dating and pine pollen density. The transect data revealed that the changes observed by remote sensing during past decades originated already from the end of the Little Ice Age (LIA) between 1700–1850 CE in bog zones and later in the flarks of fen zones. The average lateral expansion rate of bogs over fen zones was 0.77 m y−1 (range 0.19–1.66) as estimated by remote sensing, and 0.71 m y−1 (range 0.13–1.76) based on peat transects. The contemporary plant communities conformed to the macrofossil communities, and distinct vegetation zones were recognized as representing recently changed areas. The fen-bog transition increased the apparent carbon accumulation, but it can potentially threaten fen species and habitats. These observations indicate that rapid lateral bog expansion over aapa mires may be in progress, but more research is needed to reveal if ongoing fen-bog transitions are a commonplace phenomenon in northern mires.

Rising temperature modulates pH niches of fen species

Rising temperatures may endanger fragile ecosystems because their character and key species show different habitat affinities under different climates. This assumption has only been tested in limited geographical scales. In fens, one of the most endangered ecosystems in Europe, broader pH niches have been reported from cold areas and are expected for colder past periods. We used the largest European-scale vegetation database from fens to test the hypothesis that pH interacts with macroclimate temperature in forming realized niches of fen moss and vascular plant species. We calibrated the data set (29,885 plots after heterogeneity-constrained resampling) with temperature, using two macroclimate variables, and with the adjusted pH, a variable combining pH and calcium richness. We modelled temperature, pH and water level niches for one hundred species best characterizing European fens using generalized additive models and tested the interaction between pH and temperature. Fifty-five fen species showed a statistically significant interaction between pH and temperature (adj p˂.01). Forty-six of them (84%) showed a positive interaction manifested by a shift or restriction of their niche to higher pH in warmer locations. Nine vascular plants and no moss showed the opposite interaction. Mosses showed significantly greater interaction. We conclude that climate significantly modulates edaphic niches of fen plants, especially bryophytes. This result explains previously reported regional changes in realized pH niches, a current habitat-dependent decline of endangered taxa, and distribution changes in the past. A warmer climate makes growing seasons longer and warmer, increases productivity, and may lower the water level. These effects prolong the duration and intensity of interspecific competition, support highly competitive Sphagnum mosses, and, as such, force niches of specialized fen species towards narrower high-pH ranges. Recent anthropogenic landscape changes pose a severe threat to many fen species and call for mitigation measures to lower competition pressure in their refugia.

Drepanocladus lycopodioides rediscovered in the Czech Republic: Abandoned quarries as refugia for endangered fen species

The moss Drepanocladus lycopodioides, considered extinct in the Czech Republic, has been rediscovered. The population occurs in an abandoned sandstone quarry with a shallow water pool; the site known as Lom Rasová is located in the Bílé Karpaty Mts (the White Carpathians) in the south-eastern part of the Czech Republic. The species has not been recorded in the country since the first half of the 20th century. The plant community with D. lycopodioides recorded in the Lom Rasová quarry resembles alkaline fens transient to intermittently wet meadows, i.e. the natural habitat of the species. We conclude that abandoned waterlogged quarries mimic the key environmental conditions that determine the natural occurrence of D. lycopodioides, i.e. high calcium richness, water table fluctuations, low productivity and irregular disturbances that prevent the dominance of competitively superior species. Such conditions no longer occur in current central-European agricultural landscapes. We encourage bryologists and mire ecologists to explore abandoned quarries and other post-mining habitats with shallow water bodies, as they may represent potential refugia for endangered fen species.

Cause of decade’s stagnation of plant communities through16-years successional trajectory toward fens at a created wetland in northern Japan

Hiraoka is the created wetland that was constructed in 2000 in an urban park in Sapporo City. We introduced fen and bog plants and monitored the hydrochemical conditions and species assemblage composition four times during the 16 years after construction (YAC). The species richness indices of total, exotics, and annuals resembled those of the target fens within 11 YAC, but the species assemblages did not match the target fens even after 16 YAC, showing that species richness is a less effective way to measure success. The 0.1 m high artificial hummocks enhanced species richness 1.3 to 1.4 times more than the surrounding hollows and increased variety within species assemblages (although these hummocks collapsed before16 YAC). Water level from ground surface (WL) were stable at around 0.00 to +0.05 m, except during several-days floods, when a maximum WL of +0.4 to +0.5 m. Hydrological conditions were, therefore, similar to those natural fens nearby. Mean pH values (min and max) decreased from 6.9 (5.5–9.3) in 1 YAC to 6.2 (5.7–6.9) in 16 YAC and approached those of natural fens. The mean electrical conductivity (166–196 μScm-1) and concentrations of major minerals (Ca2+, Mg2+, and K+) were consistently higher than those of Japanese fens, but dissolved phosphorus (0.00–0.04 mg l−1) and nitrogen (0.12–0.48 mg l−1) were lower. The trajectory of species assemblages quickly approached the target fen at least 5 YAC, but then changed between 5 and 11 YAC, before stagnating. Since mineral content in Hiraoka was near the lower limit of calcareous rich-fens, abundant minerals would be less effective in changing the species assemblage compositions. Due to the dominance of eight initially introduced fen species, the trajectory turned in a different direction. Species assemblages stagnated between initial and target communities before 16 YAC, since the five fen dominants introduced at 8 to 9 YAC had not yet dominated. Accordingly, initial introductions, including species combinations of target fen, can shorten the time required to achieve natural fens. At 16 YAC, large emerged macrophytes did not dominate and did not competitively exclude fen species, probably because the water was oligotrophic and the wetland design did not include open water.

Impact of local- and regional-scale restoration measures on a vulnerable rich fen in the Naardermeer nature reserve (the Netherlands)

Restoration of rich fens is commonly attempted through local-scale measures, such as removal of sod or blockage of ditches. However, regional-scale restoration measures, that aim to re-establish the original hydrology in which rich fens developed, might have a more long-lasting effect. We investigated the effect of local- and regional-scale restoration measures on a vulnerable rich fen in the Naardermeer nature reserve in the Netherlands. We compared water quality and vegetation composition of the fen before and after the restoration measures, almost 30 years apart. Overall rich fen species increased and although this indicates the desired increased supply of fresh mineral-rich groundwater to the fen, continued succession towards poor fen vegetation has not been prevented in the entire fen. Despite sod layer removal, we observed an increase in a Polytrichum-dominated vegetation in patches that are primarily fed by rainwater. Our findings confirm results from a previous study which showed that brackish palaeo-groundwater is still contributing substantially to the water balance of the fen, especially in periods of precipitation deficit. We conclude that the local- and regional-scale restoration measures have been successful in increasing the abundance of rich fen species in parts of the fen. However, considering the pressures of climate change and high atmospheric N-deposition on the fen, it is uncertain whether rich fen species can be sustained in quite nutrient-poor conditions in the future. Therefore, there is a need for continued management that keeps the nutrient-poor and mineral-rich conditions of the fen intact.

Is 15% restoration sufficient to safeguard the habitats of boreal red-listed mire plant species?

We used habitat suitability modeling to investigate whether the 15% ecosystem restoration target set in the previous Convention of Biological Diversity (CBD) and EU Biodiversity strategy targets, is sufficient to safeguard red-listed mire plant species. We assessed six theoretical restoration scenarios for drained peatland landscapes by altering the proportion of drained and undrained peatland area in 25-ha grid cells. The proportions represented steps when 15%, 30%, 45%, 60%, 75% and 100% of the drained peatland is restored. We modelled the habitat suitability for 48 red-listed plant species in the aapa mire region in boreal Finland. Model outcomes were assessed at the level of five species groups: calcareous species, rich fen species, decaying wood species, mesotrophic fen species, and spruce swamp species. The predicted distribution increased for 34 (71%) of the 48 red-listed plant species when 15% of drained peatland area was predicted to be restored. At the same time the potentially occupied area of species increased by 9%. In the scenario where all peatlands were restored, the predicted distribution of 43 (90%) of species increased, and on average the distribution of species quadrupled. According to our predictions, meeting the 15% ecosystem restoration target, set in the previous CBD and EU Biodiversity strategy targets would be beneficial for most of the boreal red-listed mire plant species, but a larger restoration area would expand their distribution considerably more. Our study shows that a landscape level approach is important to assess thresholds for the potential biodiversity benefits arising from peatland restoration. The models can also be used to select suitable areas for restoration.

Can relict-rich communities be of an anthropogenic origin? Palaeoecological insight into conservation strategy for endangered Carpathian travertine fens

Western-Carpathian travertine fens developed on deep-circulation groundwater are highly localised and harbour unique communities that combine rare species of calcareous fens and salt marshes, with many species considered glacial or Early-Holocene relicts. Using a multi-proxy palaeoecological approach, we tested the assumption of naturalness and Holocene continuity of the current plant and mollusc communities occupying one of the best-preserved travertine fens in Europe. Our novel results, based on two complete cores throughout the fen deposits, document an anthropogenic origin of the current communities, despite their richness in rare and relict species. The habitat originated in the very beginning of the Holocene, later it was encroached by a semi-open woodland with spruce and alder and then by a dense reed bed that suppressed fen species even more than woodland encroachment. When compared with a fen site on shallow-circulation groundwater, the Holocene succession to woodlands has been blocked by travertine formation, allowing survival of light-demanding relicts in small patches. The current communities were established once the woody plants, and especially reed, were reduced by medieval land use. The community itself is therefore not relict, but it harbours probable descendants of relict populations that survived in neighbouring small refugia throughout the Holocene. Our results strongly support the need for active conservation actions as mowing and extensive grazing, mimicking the traditional type of land use, which has conditioned the recent travertine assemblages in the past.

Self‐facilitation and negative species interactions could drive microscale vegetation mosaic in a floating fen

AbstractAimThe formation of a local vegetation mosaic may be attributed to local variation in abiotic environmental conditions. Recent research, however, indicates that self‐facilitating organisms and negative species interactions may be a driving factor. In this study, we explore whether heterogeneous geohydrological conditions or vegetation feedbacks and interactions could be responsible for a vegetation mosaic of rich and poor fen species.LocationLake Aturtaun, Roundstone Bog, Ireland.MethodsIn a floating fen, transects were set out to analyze the relation between vegetation type and rock–peat distance and porewater electrical conductivity. Furthermore, three distinct vegetation types were studied: rich fen, poor fen and patches of poor fen within rich fen vegetation. Biogeochemical measurements were conducted in a vertical profile to distinguish abiotic conditions of distinct vegetation types.ResultsGeohydrological conditions may drive the distribution of poor and rich fen species at a larger scale in the floating fen, due to the supply of minerotrophic groundwater. Interestingly, both rich and poor fen vegetation occurred in a mosaic, when electrical conductivity values at 50 cm depth were between 300 µS/cm and 450 µS/cm. Although environmental conditions were homogeneous at 50 cm, they differed markedly between rich and poor fen vegetation at 10 cm depth. Specifically, our measurements indicate that poor fen vegetation lowered porewater alkalinity, bicarbonate concentrations and pH. No effects of rich fen vegetation at 10 cm depth on biogeochemistry was measured. However, rich fen litter had a higher mineralization rate than poor fen litter, which increases the influence of minerotrophic water in rich fen habitat.ConclusionsThese results strengthen our hypothesis that species can drive formation of vegetation mosaics under environmentally homogeneous conditions in a floating fen. Positive intraspecific self‐facilitating mechanisms and negative species interactions could be responsible for a stable coexistence of species, even leading to local ecosystem engineering by the species, explaining the local vegetation mosaic at the microscale level in a floating fen.

The ratio between bryophyte functional groups impacts vascular plants in rich fens

AbstractQuestionFens have a well‐developed bryophyte layer covering most of the ground. Non‐sphagnaceous bryophytes, especially the group of so‐called brown mosses, prevail over sphagna under alkaline conditions. In sub‐alkaline conditions, rich fens allow the co‐occurrence of both these functional groups, but sphagna are competitively superior over non‐sphagnaceous bryophytes and seedlings of vascular plants, and they are currently expanding in some regions. We test whether the ratio between the two major bryophyte functional groups (bryo‐ratio) accounts for the species composition of vascular plants in fens.LocationCentral and Eastern Europe.MethodsAnalysis of two existing regional‐ and continental‐scale data sets of the vegetation‐ plot records and measured local factors by Canonical Correspondence Analysis with variation partitioning (community‐level analysis) and Structural Equation Modelling (species‐level analysis).ResultsAt the community level, the bryo‐ratio accounted significantly for species composition of fen‐specialized vascular plants, more obviously in the regional‐scale data set. At the species level, more fen species (50–67% according to the data set) were significantly directly affected (adjusted p < 0.05) by the bryo‐ratio than by water pH (14–17%) and by measured water table depth (WTD) in the regional data set (12.5%). In the continental data set, the comparable proportions of species were directly affected by the bryo‐ratio and WTD inferred by soil moisture indicator values (50% vs 58%). Most of the species affected significantly by the bryo‐ratio preferred the fens rich in non‐sphagnaceous bryophytes. They were largely those with a low capability of vegetative reproduction.ConclusionsThe group of species preferring brown moss patches includes mostly rare and endangered species with a great need for generative reproduction (e.g., Primula farinosa, Triglochin palustris, Pedicularis palustris, Saxifraga hirculus). Our findings demonstrate the important role of the bryophyte layer in the structuring of vascular plant communities in fens and highlight urgent conservation needs for brown moss patches.