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Flowing water can disperse a high number of seeds and vegetative propagules over long distances and is therefore a very important dispersal vector in wetland habitats. Although the dispersal of seeds is relatively well studied, the dispersal of vegetative propagules has received less attention. However, in riparian and aquatic systems where many species have clonal growth forms, it can be very important. The relative importance of vegetative propagules in the dispersal of fen species was assessed first by determining their relative abundance in the field and second, by determining the buoyancy of plant fragments of ten fen species experimentally. On average, vegetative propagules made up 3.2-58.9% of the total propagule number (mainly Elodea nutallii). Buoyancy of the tested species ranged from 25 days to over 6 months. Surprisingly, the propagules of Stratiotes aloides and Hydrocharis morsus- ranae increased buoyancy when spring started (after ca. 100 days). The results demonstrate that vegetative propagules of riparian and aquatic fen species have a high capacity to disperse over long distances via water and are therefore likely to play an important role in the colonisation of new habitats. Especially because in nine out of the ten species tested, over 50% of the propagules were still viable after 6 months of floating. [ABSTRACT FROM AUTHOR]

Highlights: [•] The above ground parts of fen mosses and vascular plants can be separated via n-alkanes. [•] Similar n-alkanes dominated in Sphagnum spp. and vascular plant below ground parts. [•] With RDA three groups were apparent: mosses, vascular plant above and below ground parts. [•] Similar plant biomarkers in fen and bog plants but patterns not directly interchangeable. [Copyright &y& Elsevier]

Although many studies have dealt with the spatial distribution of land-snail species and individuals, the effect of quadrat size on the interpretation of distributional patterns at small scales has rarely been investigated. We studied the spatial pattern of terrestrial snail distributions within a continuously sampled area of homogeneous habitat at very small scales (<1 m2). The sampling was conducted in two contrasting habitat types: deciduous forests (29 sites) and treeless fens (23 sites) in Central Europe; each site consisted of three nested quadrats (25 × 25 cm2, 50 × 50 cm2 and 75 × 75 cm2). On average the forest plots harboured higher numbers of species than fen plots and fen assemblages were composed of significantly smaller species in body volume. Numbers of species and individuals in smaller quadrats estimated from those present in larger ones often deviated significantly from those actually observed, showing frequently aggregated distribution of snails. These deviations were most marked for comparisons involving the smallest quadrats, whereas they almost disappeared in comparisons of large and middle-sized quadrats, both for species and individuals in both habitat types. Proportional deviances between collected and estimated numbers were always significantly higher for individuals than for species, with only one exception. Our results extend previous observations of land-snail spatial aggregations and they raise questions about environmental heterogeneity even in visually homogeneous areas or about possible biotic interactions among individual species. The steeper slope of the regression between area and numbers of species in log-log space from the smallest to the middle quadrat than from the latter to the largest quadrat, and the existence of several cases in which the observed richness was significantly greater than that predicted from rarefaction, suggest that even at this scale there are still idiosyncratic variations in the range of microhabitats available within quadrats. [ABSTRACT FROM AUTHOR]

Floristic studies indicate the abundance of microalgae in northern boreal peatlands, but we know relatively little about their ecology or how they will respond to changes in environmental conditions expected in this region as climate changes. We examined changes in algal community structure at sites exposed to a long-term water-table manipulation, including drought (lowered water-table treatment), flooding (raised water-table treatment), and control (no manipulation) treatments in an Alaskan fen. In previous years, continuous algal colonization typically would have occurred only in the raised water-table treatment, but a spring flood inundated experimental plots and provided a unique opportunity to examine algal community response to rewetting after long-term drought. This event allowed us to investigate how much ecosystem memory of the antecedent water-table manipulations regulated the ability of taxa to recolonize sites after prolonged drought compared to sites that had been continuously flooded. Despite no differences in water-table position among treatments at the time of sampling, surface-water nutrient concentrations were higher in the lowered water-table treatment relative to the other treatments after the spring thaw. This difference corresponded with greater algal abundance and biovolume in the lowered water-table treatment relative to the control and raised water-table treatments. Higher abundance and biovolume was driven mainly by filamentous green algae (Chlorophyta), especially Oedogonium, Spirogyra, and Microspora. Diatoms were most abundant in the raised water-table treatment, whereas chrysophytes were most abundant in the control treatment. Across all water-table treatments, N-fixing cyanobacteria increased as nutrients and water-table position declined over time. The differences in algal community structure among water-table treatments suggest that alternating drought and flooding events expected with climate change may significantly alter algal-driven functions in boreal wetlands. [ABSTRACT FROM AUTHOR]

Abstract: To test the effects of altered hydrology on organic soil decomposition, we investigated CO2 and CH4 production potential of rich-fen peat (mean surface pH = 6.3) collected from a field water table manipulation experiment including control, raised and lowered water table treatments. Mean anaerobic CO2 production potential at 10 cm depth (14.1 ± 0.9 μmol C g−1 d−1) was as high as aerobic CO2 production potential (10.6 ± 1.5 μmol C g−1 d−1), while CH4 production was low (mean of 7.8 ± 1.5 nmol C g−1 d−1). Denitrification enzyme activity indicated a very high denitrification potential (197 ± 23 μg N g−1 d−1), but net reduction suggested this was a relatively minor pathway for anaerobic CO2 production. Abundances of denitrifier genes (nirK and nosZ) did not change across water table treatments. reduction also did not appear to be an important pathway for anaerobic CO2 production. The net accumulation of acetate and formate as decomposition end products in the raised water table treatment suggested that fermentation was a significant pathway for carbon mineralization, even in the presence of . Dissolved organic carbon (DOC) concentrations were the strongest predictors of potential anaerobic and aerobic CO2 production. Across all water table treatments, the CO2:CH4 ratio increased with initial DOC leachate concentrations. While the field water table treatment did not have a significant effect on mean CO2 or CH4 production potential, the CO2:CH4 ratio was highest in shallow peat incubations from the drained treatment. These data suggest that with continued drying or with a more variable water table, anaerobic CO2 production may be favored over CH4 production in this rich fen. Future research examining the potential for dissolved organic substances to facilitate anaerobic respiration, or alternative redox processes that limit the effectiveness of organic acids as substrates in anaerobic metabolism, would help explain additional uncertainty concerning carbon mineralization in this system. [Copyright &y& Elsevier]

Abstract: The definition of restoration targets and the evaluation of restoration success require a comprehensive, ecosystem-based analysis of all successional pathways, which proceed along gradients of land use intensification and continue after implementation of restoration measures. In the presented study, such analysis was applied to fen ecosystems. Study areas were river valleys and eutrophic lakes in The Netherlands and in Schleswig-Holstein, the northernmost state of Germany. At these sites high fen degradation has taken place and restoration strategies such as “recovery of peat-forming systems” and “development of species-rich fen grasslands” have recently been pursued. Based on an indirect successional analysis, we derived characteristic shifts of abiotic (hydrodynamics, soil parameter) and biotic (species composition, phytomass production) ecosystem traits relative to increasing land use intensity. Species richness and nature conservation value (NCV) initially increased and afterwards decreased during the process of land use intensification. This floristic change was accompanied by an initial decrease and subsequent increase in system productivity. Indicators for P-availability showed the same trend and there was evidence that nutrient limitation changed initially from N- (tall sedge reeds) to P- or P/N (co)-limitation (small sedge reeds) and afterwards again to N-limitation (wet and mesic grasslands). The successional analysis documented the abiotic requirements of vegetation types and their characteristic species, and thus, allowed for the use of these ecosystem traits as indicators to evaluate the success of specific restoration targets. For example, the decrease of Scheuchzerio-Caricetea species could be related more directly to reduced light availability than to an increase of the groundwater tables. Furthermore, we calculated threshold values of these traits for the occurrence of target species. For instance, a sustainable establishment of light-demanding mesotrophic species can only be expected if the standing crop value is less than 400gm−2. In a further step, we estimated the restoration success in selected study areas by applying the findings of the successional analysis. Results showed that rewetting measures have to be carried out with caution if both restoration strategies are aspired in one specific area. Moreover, restoration success of both strategies is limited in initially highly degraded areas. Sources for target species are often missing and abiotic conditions such as nutrient levels and flooding periods are often inappropriate. Consequently, expectations for restoration success should be adapted to the realistic development potential of the individual system and a cost–benefit analysis has to be carried out to avoid unnecessary management costs. [Copyright &y& Elsevier]

Human landscape modification has led to habitat fragmentation for many species. Habitat fragmentation, leading to isolation, decrease in patch size and increased edge effect, is observed in fen ecosystems that comprise many endangered plant species. However, until now it has remained unclear whether habitat fragmentation per se has a significant additional negative effect on plant species persistence, besides habitat loss and degradation. We investigated the relative effect of isolation, habitat size, and habitat edge compared to the effect of habitat degradation by including both 'fragmentation variables' and abiotic variables in best subsets logistic regression analyses for six fen-plant species. For all but one species, besides abiotic variables one or more variables related to fragmentation were included in the regression model. For Carex lasiocarpa, isolation was the most important factor limiting species distribution, while for Juncus subnodulosus and Menyanthes trifoliata, isolation was the second most important factor. The effect of habitat size differed among species and an increasing edge had a negative effect on the occurrence of Carex lasiocarpa and Pedicularis palustris. Our results clearly show that even if abiotic conditions are suitable for certain species, isolation of habitat patches and an increased habitat edge caused by habitat fragmentation affect negatively the viability of characteristic fen plant species. Therefore, it is important not only to improve habitat quality but also to consider spatial characteristics of the habitat of target species when deciding on plant conservation strategies in intensively used landscapes, such as fen areas in Western Europe and North America. [ABSTRACT FROM AUTHOR]

Abstract: As the global climate changes so will the balance of carbon dioxide (CO2) sequestration and release from peatlands. The changes occurring within peatlands will be complex, making their future carbon (C) responses difficult to predict. We studied three boreal fen peatlands along a nutrient gradient in northern Ontario, Canada. Specifically, we investigated how abiotic and biotic responses of the fens interacted with seasonal and annual hydrologic variability. We further assessed the role that a local disturbance, such as inundation due to beaver dams, has in confounding fen C dynamics. We conducted these assessments by applying the process-based model Wetland-DNDC, which we parameterized, calibrated and corroborated with field data, to examine how C dynamics were affected by fen type (rich, intermediate and poor), historical and projected climate and local flooding disturbance. We found inter-annual variability in greenhouse gas (CO2 and methane, CH4) dynamics to be large among fens, with larger coefficients of variation for heterotrophic respiration and CH4 effluxes (a range of 40–85% and 31–58%, respectively) than gross primary production (a range of 9–26%). This annual variability in C effluxes correlated to meteorological conditions and water table, although the specific drivers differed among fens. Scenarios of prolonged flooding and drought had opposite effects on C effluxes. Drought increased CO2 efflux by 43%, 175% and 65% for rich, intermediate and poor fens, respectively, and decreased CH4 efflux by 11% and 14% for the intermediate and poor, but increased CH4 efflux by 19% for the rich fen. In contrast, shallow flooding decreased CO2 by 40%, 72% and 57% in the rich, intermediate and poor fen, and increased CH4 effluxes by 87%, 202% and 269%, respectively. Flooding by beaver dams during a prolonged drought moderately decreased CO2 (29%, 66% and 53%) but strongly increased CH4 efflux by 121%, 261% and 333%, respectively, than the flooding only. We conclude that the interacting controls on greenhouse gas dynamics differ among fens types, contributing to the magnitude of effluxes and their response to changing conditions. We propose that effects of water table level, peat nutrient status, and vegetation composition, and their interactions, on C processes require enhanced understanding to define natural ranges of spatial and temporal variability. Only then will it be possible to adequately predict future peatland C responses to climate and other environmental changes. As such, short-term experimental results or field studies should not be used to predict future peatland C dynamics without an understanding of the natural range of variation in the environmental drivers and the response of C processes to those drivers. [Copyright &y& Elsevier]

Climate change induced drying and flooding may alter the redox conditions of organic matter decomposition in peat soils. The seasonal and intermittent changes in pore water solutes (NO3-, Fe2+, SO42- , H2S, acetate) and dissolved soil gases (CO2, O2, CH4, H2) under natural water table fluctuations were compared to the response under a reinforced drying and flooding in fen peats. Oxygen penetration during dryings led to CO2 and CH4 degassing and to a regeneration of dissolved electron acceptors (NO3-, Fe3+ and SO42-). Drying intensity controlled the extent of the electron acceptor regeneration. Iron was rapidly reduced and sulfate pools ~1 mM depleted upon rewetting and CH4 did not substantially accumulate until sulfate levels declined to ~100 µmol L-1. The post-rewetting recovery of soil methane concentrations to levels ~80 µmol L-1 needed 40-50 days after natural drought. This recovery was prolonged after experimentally reinforced drought. A greater regeneration of electron acceptors during drying was not related to prolonged methano-genesis suppression after rewetting. Peat compaction, solid phase content of reactive iron and total reduced inorganic sulfur and organic matter content controlled oxygen penetration, the regeneration of electron acceptors and the recovery of CH4 production, respectively. Methane production was maintained despite moderate water table decline of 20 cm in denser peats. Flooding led to accumulation of acetate and H2, promoted CH4 production and strengthened the co-occurrence of iron and sulfate reduction and methanogenesis. Mass balances during drying and flooding indicated that an important fraction of the electron flow must have been used for the generation and consumption of electron acceptors in the solid phase or other mechanisms. In contrast to flooding, dry-wet cycles negatively affect methane production on a seasonal scale, but this impact might strongly depend on drying intensity and on the peat matrix, of which structure and physical properties influence moisture content. [ABSTRACT FROM AUTHOR]

Calcareous fens are unique environments whose history is almost unexplored. The radiocarbon dates of the basal layers of 49 undisturbed calcareous fens showed that in the Western Carpathians (central Europe) many of the extant fen sites originated fairly recently, with two peaks in the High Middle and Roman Ages, the former corresponding to human-induced changes of the landscape. Conspicuous number of fens also appeared in the Lateglacial and later in the Bronze Age owing to suitable environmental conditions. The Lateglacial calcareous fens were of semi-open character with coniferous trees, a heliophilous understorey, and mollusc communities composed of several snail species typical of glacial landscapes. We found wood of Taxus baccata in six localities between 7390 and 600 cal. a BP, suggesting that calcareous fens could have represented a refugial habitat for this red-listed species during the middle Holocene. Using plant macrofossil and mollusc analyses of three representative profiles we illustrate the most common developmental types: (i) fens originating in the Lateglacial, having an open or semi-open character during the whole Holocene; (ii) open fens originating as wooded wetlands; and (iii) open fens starting their development de novo in the late Holocene. Human activities were responsible for the formation of a high number of calcareous fens, especially in the Outer Western Carpathians, and became important drivers of fen biodiversity development. Only a few recently existing calcareous fens contain old sequences of calcareous deposits. They represent unique natural archives and harbour highly endangered relic populations of fen specialists, making their strict protection urgent. [ABSTRACT FROM AUTHOR]

While the effects of contemporaneous local environment on species richness have been repeatedly documented, much less is known about historical effects, especially over large temporal scales. Using fen sites in the Western Carpathian Mountains with known radiocarbon-dated ages spanning Late Glacial to modern times (16?975-270 cal years before 2008), we have compiled richness data from the same plots for three groups of taxa with contrasting dispersal modes: (1) vascular plants, which have macroscopic propagules possessing variable, but rather low, dispersal abilities; (2) bryophytes, which have microscopic propagules that are readily transported long distances by air; and (3) terrestrial and freshwater mollusks, which have macroscopic individuals with slow active migration rates, but which also often possess high passive dispersal abilities. Using path analysis we tested the relationships between species richness and habitat age, area, isolation, and altitude for these groups. When only matrix-derived taxa were considered, no significant positive relation was noted between species richness and habitat size or age. When only calcareous-fen specialists were considered, however, habitat age was found to significantly affect vascular plant richness and, marginally, also bryophyte richness, whereas mollusk richness was significantly affected by habitat area. These results suggest that in inland insular systems only habitat specialist (i.e., interpatch disperser and/or relict species) richness is influenced by habitat age and/or area, with habitat age becoming more important as species dispersal ability decreases. [ABSTRACT FROM AUTHOR]

Peatlands store large amounts of organic carbon, but the carbon stock is sensitive to changes in precipitation or water table manipulations. Restoration of drained peatlands by drain blocking and flooding is a common measure to conserve and augment the carbon stock of peatland soils. Here, we report to what extent flooding affected the contribution of heterotrophic and rhizosphere respiration to soil CO2 efflux in a grass-dominated mountain fen, Germany. Soil CO2 efflux was measured in three unmanipulated control plots and three flooded plots in two consecutive years. Flooding was achieved by permanent irrigation during the growing seasons. Radiocarbon signatures of CO2 from different sources including soil CO2 efflux, incubated peat cores and live grass roots were repeatedly analyzed for partitioning of soil CO2 efflux. Additionally, heterotrophic respiration and its radiocarbon signature were determined by eliminating rhizosphere respiration in trenched subplots (only control). In the control plots, rhizosphere respiration determined by 14C signatures contributed between 47 and 61% during the growing season, but was small (4 %) immediately before budding. Trenching revealed a smaller rhizosphere contribution of 33% (2009) and 22% (2010) during growing seasons. Flooding reduced annual soil CO2 efflux of the fen by 42% in 2009 and by 30% in 2010. The reduction was smaller in 2010 mainly through naturally elevated water level in the control plots. A 1-week interruption of irrigation caused a strong short-lived increase in soil CO2 efflux, demonstrating the sensitivity of the fen to water table drawdown near the peat surface. The reduction in soil CO2 efflux in the flooded plots diminished the relative proportion of rhizosphere respiration from 56 to 46 %, suggesting that rhizosphere respiration was slightly more sensitive to flooding than heterotrophic respiration. We conclude that the moderate decrease in rhizosphere respiration following flooding arises from a gradual change in vegetation in this fen ecosystem. [ABSTRACT FROM AUTHOR]

We compared the amount and composition of different aboveground biomass (BM) fractions of four mires with their net ecosystem CO2 exchange (NEE) measured by eddy covariance. We found clear differences in response of green biomass (GBM) of plant functional types (PFTs) to water table (WT), which resulted in larger spatial variation in GBM within a mire than variation between mires. GBM varied between mires from 126 ± 7 to 336 ± 16 g·m-2 (mean ± SE), while within mire variation at largest was from 157 ± 17 to 488 ± 20 g·m-2 (mean ± SE). GBM of dominant PFTs appeared to be better in explaining the peak growing season NEE than the total BM or GBM of a mire. The differences in photosynthetic capacity between PTFs had a major role, and thus a smaller GBM with different species composition could result in higher NEE than larger GBM. Vascular plant GBM, especially that of sedges, appeared to have a high impact on NEE. Eleven PFTs, defined here, appeared to capture well the internal variation within mires, and the differences in GBM between communities were explained by the water table response of PFTs. Our results suggest the use of photosynthesizing BM, separated into PFTs, in modelling ecosystem carbon exchange instead of using just total BM. [ABSTRACT FROM AUTHOR]

Fens and wet meadows are important mountain wetland types, but influences on assemblage structure of associated invertebrates are poorly understood compared with other aspects of the ecology of these habitats. We sought to determine the relative contributions of terrestrial and aquatic invertebrates to diversity and abundance in these wetlands, the extent to which terrestrial and aquatic invertebrate assemblages differ with wetland type, and to what degree the aquatic assemblages vary as a function of slow sheet flow. We compared assemblages in fens and wet meadows, with and without flow, at 80 backcountry sites dispersed across the 6200 km2 landscape of Yosemite, Sequoia, and Kings Canyon National Parks in the Sierra Nevada mountains of California, U.S.A., using standard aquatic and terrestrial sweep netting. Cicadellid leafhoppers, aphids, and thomisid crab spiders were the most abundant terrestrial taxa. Cicadellids, Lepidoptera, anthomyiid, muscid, chloropid, and ephydrid flies, and thomisids were more abundant in fens than in wet meadows. Only mind leaf bugs were significantly more abundant in wet meadows than fens. Sphaeriid clams and chironomid midges dominated aquatic assemblages both with and without flow. Chloroperlid stoneflies, mites, clams, and flatworms were all more abundant in flow, and Hemiptera and mosquitos were significantly more abundant in quiescent water. Mosquitos were more abundant in wet meadows, but there were few other population differences as a function of wetland type. Terrestrial diversity was 1.1 to 2.0 times that of aquatic diversity, depending on metric and habitat. Fens had greater terrestrial abundance, richness, evenness, and diversity than wet meadows; there were fewer differences as a function of wetland type for aquatic fauna. Presence or absence of slow sheet flow had more effect on these aquatic assemblages than did wetland type. Cluster analyses, ordination, and multi-response permutation procedures were generally consistent with the univariate results. Vegetation-based wetland classifications should be extrapolated to faunal assemblages with caution, particularly for aquatic invertebrates. [ABSTRACT FROM AUTHOR]

Question: Which restoration measures (reintroduction techniques, reintroduction timing and fertilization) best enable the establishment of fen species on North American cut-away peatlands? Location: Rivière-du-Loup peatland, southern Québec, Canada. Methods: In total, eight treatments which tested a combination of two reintroduction techniques, two reintroduction timings and the use of phosphorus fertilization were tested in a field experiment within a completely randomized block design. Results: Sphagnum transfer, a reintroduction technique commonly used for bog restoration in North America, was effective for establishing Sphagnum and Carex species. The hay transfer method, commonly used for fen restoration in Europe, was much less successful, probably due to questionable viability of reintroduced seeds. The treatments which included light phosphorus fertilization, had a higher Carex cover after three growing seasons. The timing of the reintroductions had no impact on the success of vegetation establishment. However, vegetation reintroduction should be carried out in the spring while the ground is still frozen to minimize other ecological impacts. Conclusions: The success of the diaspore reintroduction technique on small-scale units indicates that a large-scale restoration of fens using this technique is feasible. [ABSTRACT FROM AUTHOR]

It is demanded currently in public discussions to rewet peatlands and re-establish their function as nutrient sinks. But due to high phosphorus (P) concentrations in the pore water of rewetted peatlands (40–420 μM) it is hypothesized that they can act as a surplus P source for adjacent surface waters and consequently support the eutrophication of such waters. Our detailed investigations of processes at the redox interface in four fens with different geochemical character show the dependence of P retention from the chemistry of the pore water. The precipitation of Fe(III) oxyhydroxide led to high retention of phosphorus and other substances such as DOC and sulphate in the eutrophic fens. When molar Fe/P ratios were larger than about 3 the initially high P concentrations in the anaerobic pore water (20–210 μM) decreased to concentrations below 1 μM under aerobic conditions. Thus, after rewetting high pore water concentrations of P do not automatically result in an increased P load to adjacent surface waters compared to pre-rewetting conditions. An enhanced P export to adjacent surface waters from eutrophic fens can be expected when the Fe/P ratio is smaller than 3 in the anaerobic pore water. In our investigations of natural, oligotrophic to mesotrophic fens the precipitation of Fe(III) oxyhydroxide was inhibited by the formation of stable dissolved Fe ∼ humic complexes. P retention in these fens was only related to the DOC concentrations at the redox interface, so that lower DOC concentrations concurred with higher P retention. The P equilibrium concentrations in an aerobic environment can be higher than that of eutrophic fens with Fe/P ratios larger than about 3 in the anaerobic pore water. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discuss various reports within the issue on topics including the 1927 meeting of the Tennessee Academy of Science (TAS) with the American Association for the Advancement of Science, the botanical features of five fens in Shady Valley, and TAS' achievements in 2011.