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Highlights • Three revegetation strategies are tested to restore wet depressions in fens. • Moss transfer promotes higher fen species richness and distinct plant assemblages. • Carex spp. revegetation increases vascular species cover. • Plant communities of Scirpus validus -revegetated depressions were similar to control. • Combining moss transfer and Carex transplants should foster restoration success. Abstract Pool margins and wet depressions (hollows) contribute considerably to peatland biodiversity by sheltering specific plant assemblages. In peatlands restored after peat extraction, the typical communities associated with pools generally fail to re-establish if only the moss layer transfer technique is applied, a common approach on flat bare peatlands. To adapt peatland ecological restoration methods for recolonizing shallow wet fen habitats, this study investigates the response of plant communities re-establishing in wet depressions subjected to four revegetation strategies. In a restored fen (southeastern Quebec, Canada), 48 depressions were dug out and revegetated with 1) mosses, 2) Carex species, 3) Scirpus validus , or 4) through spontaneous colonization (control treatment without implanted species). After four growing seasons, plant community structure and composition were surveyed in and outside the revegetated area respectively to test whether reintroduced communities had a propensity to extend beyond the central wet depression. Restoration strategies strongly impacted plant communities. Moss-revegetated wet depressions had higher moss and vascular fen-specialist species richness and distinct species assemblages relative to other treatments. Carex treatment increased only vascular cover compared to control, while Scirpus validus treatment did not differ from control. The positive impact of moss transfer was local and limited to core revegetated areas, as transferred plant material did not colonize any further. Our results suggest that transferring moss in created wet depressions is an effective strategy to foster the recolonization of diverse and distinct plant assemblages, and thereby restore local fen biodiversity hotspots. [ABSTRACT FROM AUTHOR]

The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methanecycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5mScm-1, respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site varia-tions of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re)establishment of methanogens and slow (re)establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting. [ABSTRACT FROM AUTHOR]

We document the long-term development of a spring-fed fen assessing its sensivity to climate changes over the last ca. 4000 years. Our investigation is based on high-resolution, continuous plant macrofossil remains and mollusc records, complemented by pollen, geochemical analysis and radiocarbon dating of Valea Morii, located in the Feleac Hills (Transylvanian Depression) in NW Romania, Central Eastern Europe. Based on our palaeocological data we have distinguished three stages of wet habitat conditions: two stages between 4000 and 2450 cal yr BP and one in the last 800 cal yr BP, and one dry stage between ca. 2450 and 800 cal yr BP. These local habitat conditions appear to reasonably reflect regional climate characteristics. High-resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession, and stable isotope values from ca. 500 cal yr BP. The appearance of C . mariscus during the last two centuries may be related to increased wetness and associated active CaCO 3 precipitation, which allowed this plant to colonise the spring-fed fen studied. However, it can be not excluded that the occurrence and spread of a Cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the Little Ice Age. The potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change, both temperature and humidity, in mountain spring-fed fen deposits is shown. Carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation, soil development and the dissolution of bedrock carbonates, primarily as a reaction to changes in climate humidity. [ABSTRACT FROM AUTHOR]

Abstract: Calcareous fens are species‐rich peatlands that are dependent on minerotrophic water sources for wetland functioning, with current conceptual models suggesting the water source is ubiquitously groundwater upwelling. By quantifying the water balance and subsurface water flow paths and fluxes over 3 growing seasons for calcareous fens in 3 different hydrogeomorphic settings (Riparian, Trough, and Basin), we show evidence that challenges this conceptual model. The Riparian Fen received an order of magnitude more water inputs than the Trough or Basin Fens and was dominated by stream recharge inputs and groundwater outputs. Precipitation and evaporation dominated the water balance of the Trough Fen whereas only the Basin Fen received sizeable groundwater inputs. Indeed, subsurface water fluxes were low at all fens due to weak hydraulic gradients and low saturated hydraulic conductivity in some areas of each wetland, though variations in growing season precipitation led to subsurface flow reversals in all 3 fens. Our results demonstrate the importance of understanding landscape position, or hydrogeomorphic setting, on calcareous fen hydrology for improving conservation, management, and restoration efforts of these important ecosystems. [ABSTRACT FROM AUTHOR]

Many endangered plant species remain absent in rewetted, previously drained fens. We performed a 3-year introduction experiment with endangered fen species (9 Carex - and 6 bryophyte species) in 4 hydrologically restored fens to investigate which factors hamper establishment and survival. Carex species were introduced as adults and seedlings, mosses as gametophytes. Introductions were done on (initially) bare soil, which allowed us to exclude excessive competition for light during the first year. First year survival of the transplants was high in all fens (mean survival = 96%), indicating that there were no direct abiotic constraints on establishment. However, survival analysis revealed that a decrease in relative light intensity (RLI) at the soil surface during consecutive years (indicating an increase in biotic competition for light) drove high mortality rates in most species. As a result, overall final survival was lowest in the two most productive (low light) fens (mean survival = 38%), while most transplants persisted in the two less productive (high light) fens (mean survival = 79%). Taller and faster-growing Carex species were able to outgrow light limitation near the soil surface, and thus had a higher overall survivability than smaller and slower-growing species. Light limitation also drove the loss of 5 out of 6 bryophyte species. We conclude that both dispersal limitation and asymmetric competition for light may explain the lack and loss of small and endangered plant species in rewetted fens. A minimum empirical threshold of c. 30% relative light intensity near the soil surface is required for successful introduction. [ABSTRACT FROM AUTHOR]

At the biogeographical limit between the boreal and the subarctic domain in northeastern Canada, peatlands are mainly oligotrophic fens characterized by a dominance of aquatic microforms such as pools and wet hollows. These peatlands present similar features as the appa mires in Scandinavia. They show evidence for recent water-table rise indicated by tree mortality, physical degradation of strings, and pool expansion. This study aims to evaluate the timing of pool inception and their impact on the long-term dynamics of these microforms within two patterned oligotrophic fens in the Laforge region, northern Québec. Plant macrofossil and testate amoeba analyses from sediment underneath pools were used along with radiocarbon dating to reconstruct peatland pool dynamics over the Holocene. Our data indicate that wet hollows or shallow pools developed at minimal ages between ~4200 and ~2500 cal. a BP. Pool initiation in the peatlands of the Laforge region corresponds to the climate shift toward cooler and wetter conditions from the onset of the late-Holocene cooling. We suggest that the pool developed as secondary features influenced by short growing seasons, low accumulation rates, and wet conditions, which in turn affected the wettest microforms to shift into permanent pools. The differential response of microforms to shift in surface wetness shows the complexity of processes involved in pool initiation. [ABSTRACT FROM AUTHOR]

Abstract: Beaver dams are known to raise water tables in mineral soil environments, but very little is known about their impact in wetlands, such as peatlands. Peatlands tend to have shallow water tables, and the position and tendency of the water table to fluctuate (i.e., stability) is a factor controlling the system's ability to store carbon and water. Many peatland environments, especially fens, offer ideal habitat for beaver, and the potential for beaver dams to influence this link by manipulating water tables requires investigation. Our objective was to determine the influence of beaver dams on the water table dynamics of a Rocky Mountain fen. We monitored water tables in the peatland for 4 years while beaver dams were intact and 2 years after they were breached by an extreme flood event. We found that, because of the unique way in which dams were built, they connected the peatland to the stream and raised and stabilized already high water tables within a 150‐m radius. Beaver‐mediated changes to peatland water table regimes have the potential to enhance carbon sequestration and the peatland's ability to respond to external pressures such as climate change. Furthermore, beaver dams increased surface and groundwater storage, which has implications for regional water balances, especially in times of drought. [ABSTRACT FROM AUTHOR]

To quantify arsenic (As) volatilisation by peatlands and to elucidate the environmental factors governing As volatilisation, a series of anoxic incubations with acidic fen soil collected in northeast Bavaria in Germany were performed at 15 °C for 4 months. Arsenic volatilisation summed to 2.32 ng As in the control, which was 1.6% and ~ 0.01% of the porewater As and the total As storage in the fen soil, respectively. Treatment with 10 mM NaN 3 resulted in only 0.03 ng As volatilisation. In comparison, addition of 10 mM NaOAc stimulated microbial activity in fen soil and As volatilisation rose to 8.42 ng As, indicating that As volatilisation by fen soil is primarily biogenic. Spiking with 67 μM As(III) increased As volatilisation eightfold, supposedly caused by the largely enhanced As availability in porewater for microbes (~ 10 times higher than the control). Adding 10 mM FeCl 3 and Na 2 SO 4 decreased As volatilisation to 0.30 and 0.82 ng As, respectively, apparently due to the change of microbial activity. Speciation of gaseous As in the headspace using GC-ICP-MS/EI-MS showed the predominance of arsine and trimethylarsine in treatments with low and high porewater As concentrations, respectively, suggesting different formation pathways of arsine and methylarsines. This study demonstrated the strong linkage between microorganisms and As volatilisation by peatlands and furthermore indicated the minor role of As volatilisation in the natural As biogeochemical cycle in the semi-terrestrial environment. [ABSTRACT FROM AUTHOR]

This study reports the annual carbon balance of a drained riparian fen under two-cut or three-cut managements of festulolium and tall fescue. CO2 fluxes measured with closed chambers were partitioned into gross primary production ( GPP) and ecosystem respiration ( ER) for modelling according to environmental factors (light and temperature) and canopy reflectance (ratio vegetation index, RVI). Methodological assessments were made of (i) GPP models with or without temperature functions (Ft) to adjust GPP constraints imposed by low temperature (<10 °C) and (ii) ER models with RVI or GPP parameters as biomass proxies. The sensitivity of the models was also tested on partial datasets including only alternate measurement campaigns and on datasets only from the crop growing period. Use of Ft in GPP models effectively corrected GPP overestimation in cold periods, and this approach was used throughout. Annual fluxes obtained with ER models including RVI or GPP parameters were similar, and also annual GPP and ER fluxes obtained with full and partial datasets were similar. Annual CO2 fluxes and biomass yield were not significantly different in the crop/management combinations although the individual collars ( n = 12) showed some variations in GPP (−1818 to −2409 g CO2-C m−2), ER (1071 to 1738 g CO2-C m−2), net ecosystem exchange ( NEE, −669 to −949 g CO2-C m−2) and biomass yield (556 to 1044 g CO2-C m−2). Net ecosystem carbon balance ( NECB), as the sum of NEE and biomass carbon export, was only slightly negative to positive in all crop/management combinations. NECBs, interpreted as emission factors, tended to favour the least biomass producing systems as the best management options in relation to climate saving carbon balances. Yet, considering the down-stream advantages of biomass for fossil fuel replacement, yield-scaled carbon fluxes are suggested to be given additional considerations for comparison of management options in terms of atmospheric impact. [ABSTRACT FROM AUTHOR]

The moss layer transfer technique removes the top layer of vegetation from donor sites as a method to transfer propagules and restore degraded or reclaimed peatlands. As this technique is new, little is known about the impacts of moss layer transfer on vegetation and carbon fluxes following harvest. We monitored growing season carbon dioxide (CO) and methane (CH) fluxes as well as plant communities at donor sites and neighbouring natural peatland sites in an ombrotrophic bog and minerotrophic fen in Alberta, Canada from which material was harvested between 1 and 6 years prior to the study. Plant recovery at all donor sites was rapid with an average of 72% total plant cover one growing season after harvest at the fen and an average of 87% total plant cover two growing seasons after harvest at the bog. Moss cover also returned, averaging 84% 6 years after harvest at the bog. The majority of natural peatlands in western Canada are treed and tree recruitment at the donor sites was limited. Methane emissions were higher from donor sites compared to natural sites due to the high water table and greater sedge cover. Carbon budgets suggested that the donor fen and bog sites released higher CO and CH over the growing season compared to adjacent natural sites. However, vegetation re-establishment on donor sites was rapid, and it is possible that these sites will return to their original carbon-cycle functioning after disturbance, suggesting that donor sites may recover naturally without implementing management strategies. [ABSTRACT FROM AUTHOR]

Choosing past and present-day indicators could strengthen the reference ecosystem used for ecological restoration projects. Based on the paleoecological analysis of four peat cores and the characterization of 13 contemporary natural sites, the reference ecosystem for minerotrophic peatlands in southeastern Canada is composed of two broad categories of plant assemblages described as tall-sedge and Sphagnum-Thuja/brown moss. In paleoecological peat profiles, tall-sedge communities were found at the transition between aquatic and terrestrial, and were associated with high graminoid production, riverine peatlands, and elevated water table in the present-day analyses. Sphagnum-Thuja communities resemble the present-day vegetation found in natural basin type peatlands. Except for Sphagnum warnstorfii Russ., these communities, with high taxonomical diversity, contain more generalist species from boreal peatland vegetation, such as Rhododendron groenlandicum (Oeder) Kron & Judd, Thuja occidentalis L., Linnaea borealis L., and Maianthemum trifolium L. They grow in dryer or shady habitats such as hummocks or forest understory. The importance of brown mosses was revealed by paleoecological analysis. Overall, findings from both approaches are complementary: paleoecological stratigraphy informs us about past ecosystem dynamics, while present-day inventories allow us to define current plant communities and their major environmental characteristics. The range of variability of vegetation and environmental variables found in these studies are essential tools for fen restoration projects. [ABSTRACT FROM AUTHOR]

Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission ( FCH4), ecosystem respiration ( ER), net ecosystem exchange ( NEE) and gross primary production ( GPP) fluxes from a 9-years water table manipulation experiment in an Alaskan rich fen. The study included major flood and drought years, where wetting and drying treatments further modified the severity of droughts. Results support previous findings from peatlands that drought causes reduced magnitude of growing season FCH4, GPP and NEE, thus reducing or reversing their C sink function. Experimentally exacerbated droughts further reduced the capacity for the fen to act as a C sink by causing shifts in vegetation and thus reducing magnitude of maximum growing season GPP in subsequent flood years by ~15% compared to control plots. Conversely, water table position had only a weak influence on ER, but dominant contribution to ER switched from autotrophic respiration in wet years to heterotrophic in dry years. Droughts did not cause inter-annual lag effects on ER in this rich fen, as has been observed in several nutrient-poor peatlands. While ER was dependent on soil temperatures at 2 cm depth, FCH4 was linked to soil temperatures at 25 cm. Inter-annual variability of deep soil temperatures was in turn dependent on wetness rather than air temperature, and higher FCH4 in flooded years was thus equally due to increased methane production at depth and decreased methane oxidation near the surface. Short-term fluctuations in wetness caused significant lag effects on FCH4, but droughts caused no inter-annual lag effects on FCH4. Our results show that frequency and severity of droughts and floods can have characteristic effects on the exchange of greenhouse gases, and emphasize the need to project future hydrological regimes in rich fens. [ABSTRACT FROM AUTHOR]

Overburden and tailings materials from oil sands production were used as construction materials as part of a novel attempt to create a self-sustaining, peat accumulating fen-upland ecosystem. To evaluate the potential for elemental release from the construction materials, total elemental concentrations in the tailings sand, petroleum coke and peat used to construct a fen ecosystem were determined using microwave-assisted acid digestions and compared to a leaching experiment conducted under environmentally-relevant conditions. A comparison of solid phase to aqueous Na, Ca, S and Mg concentrations showed they were highly leachable in the materials. Given that the concentrations of these elements can affect plant community structure, it is important to understand their leachability and mobility as they migrate between materials used to construct the system. To that end, a mass balance of aqueous Na, Ca, S and Mg was conducted based on leaching experiments and materials analysis coupled with existing data from the constructed system. The data indicate that there is a large pool of leachable Na, Ca, S and Mg in the system, estimated at 27 t of Na, 14 t of Ca, 37.3 t of S and 8.8 t of Mg. Since recharge mainly drives the fen-upland system water regime, and discharge in the fen, evapo-accumulation of these solutes on the surface may occur. [ABSTRACT FROM AUTHOR]

Wetlands are very vulnerable ecosystems and sensitive to changes in the ground water table. For the last few thousand years, hydrological balance has also been influenced by human activity. To improve their cropping features, drainage activity and fertilizing were applied. The drainage process led to an abrupt change of environment, the replacement of plant communities and the entire ecosystem. The problem of carbon sequestration is very important nowadays. A higher accumulation rate is related to higher carbon accumulation, but the intensity of carbon sequestration depends on the type of mire, habitat, and climatic zone. The main aim of this article was an examination of the changes in poor-fen ecosystem during the last 200 years in relation to natural and anthropogenic factors, using paleoecological methods (pollen and macrofossils). The second aim was a detailed investigation of the sedimentary record to aid our understanding of carbon sequestration in the poor fen of temperate zone. This case study shows that fens in temperate zones, in comparison with boreal ones, show higher carbon accumulation rates which have been especially intensive over the last few decades. To reconstruct vegetation changes, detailed palynological and macrofossil analyses were done. A 200-year history of the mire revealed that it was influenced by human activity to much degree. However, despite the nearby settlement and building of the drainage ditch, the precious species and plant communities still occur. [ABSTRACT FROM AUTHOR]

Large peatland complexes dominate the landscape of the James Bay Lowland in subarctic Ontario, Canada. However, there is not a thorough understanding of the hydrological processes occurring in these important systems, particularly how ladder fens connect large domed bogs to the aquatic ecosystems that drain the peatland complex. Ladder fens consist of a pool-rib topography where flow downgradient is controlled by the peat ribs. Within the ribs, low-lying preferential flow paths typically enhance the transmission of water, whereas the elevated ridge microforms impede water flow to downgradient aquatic ecosystems. To assess the hydrological connectivity, we study the role of the water table, peat transmissivity, and microtopography of a small ladder fen for 3 summers (2013-2015) in the James Bay Lowland. The system was manipulated with a sustained hydrological forcing (water addition) to the upslope boundary of the fen during 2014 (38 m3/day) and 2015 (30 m3/day). There was an exponential increase in transmissivity towards the peat surface due to extremely high-hydraulic conductivities within the upper few centimeters of the peat deposit. At the maximum water table, the saturated hydraulic conductivity of the 0.1 m layer of peat below the water table varied depending on peat microtopography (preferential flow paths = 42-598 m/day and ridges = 16-52 m/day), resulting in high-hydrological connectivity periods. Furthermore, during 2015, there was an abnormally large amount of precipitation (300 mm vs. long-term average ~ 100 mm) that resulted in complete surface water connectivity of the site. This caused rapid movement of water from the head of system to the outlet (~15 hr) and runoff ratios >1, compared to low-water table periods (runoff ratio ~ 0.05). This study highlights the profound importance of the transmissivity-water table feedback mechanism in ladder fens, on controlling the water retention and drainage of large peatland complexes. [ABSTRACT FROM AUTHOR]

Questions On-going rapid loss of fen biodiversity in Central Europe is well known, but rigorous testing of this is complicated. We compared historical and present-day vegetation plot records from a cultural landscape rich in fishponds, where recent eutrophication and water table manipulations threaten the unique fen diversity. We assess species composition change over the last 50 yr. Location Třeboň Basin, Czech Republic. Methods First, we revisited historical vegetation plots to collect present-day data and then identified the most similar present-day record (the present-day counterpart) because no permanent plots were available. Second, we inferred water level, pH and conductivity (a proxy of mineral richness) using a training set of present-day field measurements, and calculated Ellenberg indicator values. Then we applied modified TWINSPAN classification, CCA, PERMANOVA, PERMDISP and RMANOVA in order to test changes in the species composition, β-diversity and environmental conditions between the historical records and their present-day counterparts. Results Fen vegetation has persisted on half of the sites. Out of four vegetation types, poor fens and especially flooded fens were over-represented in the present-day subset, while rich fens and quaking fens were under-represented. Overall species composition differed between historical plots and their present-day counterparts, even within individual vegetation types. Historical rich fens showed significantly higher β-diversity than their present-day counterparts, which predominantly represent flooded fens. Inferred water level and its fluctuation, Ellenberg moisture and nutrient values have increased, while inferred pH, conductivity and Ellenberg light value have decreased. Conclusions The historically wide array of fen vegetation has turned into a homogeneous and floristically depauperate set of acidic yet productive flooded fens with a high water level. Rich and quaking fens that were both low in nutrient availability and had a stable water level near the moss layer experienced a large and substantial reduction and have become rare in the landscape. Eutrophication combined with a lack of management has resulted in fen species persisting only in flooded fens. However, fluctuating water levels and high nutrient availability in flooded fens favour productive Sphagnum fens over the other vegetation types, and, importantly, do not support some endangered fen species. [ABSTRACT FROM AUTHOR]

Effective conservation of priority habitat 7210* Calcareous fens with Cladium mariscus and species of the Caricion davallianae depends on complete knowledge of the biology of Cladium mariscus. This study was aimed to determine effect of temperature and habitat water level on growth, development and physiological status of generative shoots of C. mariscus. Maximum quantum yield of photosystem II photochemistry dynamics during both seasons was similar; but in summer 2016 the values were significantly higher than in 2015. Difference in height of generative shoots was not found between years. Average number of generative shoots indicated a significant difference between years. Immediate effect of temperature or habitat water level changes on generative shoot growth were not observed. However, two-season measurements of maximum quantum yield of photosystem II photochemistry showed that C. mariscus is welladapted to high habitat water level and might be sensitive to habitat water level fluctuations, when the water level falls below 5 cm. On the north-eastern limit of the distribution range the number of generative shoots of C. mariscus in the next growing season is affected by previous autumn drought and temperature below 0 °C as well. [ABSTRACT FROM AUTHOR]

Vegetation indices are widely used as model inputs and for non-destructive estimation of biomass and photosynthesis, but there have been few validation studies of the underlying relationships. To test their applicability on temperate fens and the impact of management intensity, we investigated the relationships between normalized difference vegetation index ( NDVI), leaf area index ( LAI), brown and green above-ground biomass and photosynthesis potential ( PP). Only the linear relationship between NDVI and PP was management independent ( R2 = 0·53). LAI to PP was described by a site-specific and negative logarithmic function ( R2 = 0·07-0·68). The hyperbolic relationship of LAI versus NDVI showed a high residual standard error (s.e.) of 1·71-1·84 and differed between extensive and intensive meadows. Biomass and LAI correlated poorly ( R2 = 0·30), with high species-specific variability. Intensive meadows had a higher ratio of LAI to biomass than extensive grasslands. The fraction of green to total biomass versus NDVI showed considerable noise (s.e. = 0·13). These relationships were relatively weak compared with results from other ecosystems. A likely explanation could be the high amount of standing litter, which was unevenly distributed within the vegetation canopy depending on the season and on the timing of cutting events. Our results show there is high uncertainty in the application of the relationships on temperate fen meadows. For reliable estimations, management intensity needs to be taken into account and several direct measurements throughout the year are required for site-specific correction of the relationships, especially under extensive management. Using NDVI instead of LAI could reduce uncertainty in photosynthesis models. [ABSTRACT FROM AUTHOR]

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Aims Phytosociological classification of fen vegetation ( Scheuchzerio palustris-Caricetea fuscae class) differs among European countries. Here we propose a unified vegetation classification of European fens at the alliance level, provide unequivocal assignment rules for individual vegetation plots, identify diagnostic species of fen alliances, and map their distribution. Location Europe, western Siberia and SE Greenland. Methods 29 049 vegetation-plot records of fens were selected from databases using a list of specialist fen species. Formal definitions of alliances were created using the presence, absence and abundance of Cocktail-based species groups and indicator species. DCA visualized the similarities among the alliances in an ordination space. The ISOPAM classification algorithm was applied to regional subsets with homogeneous plot size to check whether the classification based on formal definitions matches the results of unsupervised classifications. Results The following alliances were defined: Caricion viridulo-trinervis (sub-halophytic Atlantic dune-slack fens), Caricion davallianae (temperate calcareous fens), Caricion atrofusco-saxatilis (arcto-alpine calcareous fens), Stygio-Caricion limosae (boreal topogenic brown-moss fens), Sphagno warnstorfii-Tomentypnion nitentis ( Sphagnum-brown-moss rich fens), Saxifrago-Tomentypnion (continental to boreo-continental nitrogen-limited brown-moss rich fens), Narthecion scardici (alpine fens with Balkan endemics), Caricion stantis (arctic brown-moss rich fens), Anagallido tenellae-Juncion bulbosi (Ibero-Atlantic moderately rich fens), Drepanocladion exannulati (arcto-boreal-alpine non-calcareous fens), Caricion fuscae (temperate moderately rich fens), Sphagno-Caricion canescentis (poor fens) and Scheuchzerion palustris (dystrophic hollows). The main variation in the species composition of European fens reflected site chemistry (pH, mineral richness) and sorted the plots from calcareous and extremely rich fens, through rich and moderately rich fens, to poor fens and dystrophic hollows. ISOPAM classified regional subsets according to this gradient, supporting the ecological meaningfulness of this classification concept on both the regional and continental scale. Geographic/macroclimatic variation was reflected in the second most important gradient. Conclusions The pan-European classification of fen vegetation was proposed and supported by the data for the first time. Formal definitions developed here allow consistent and unequivocal assignment of individual vegetation plots to fen alliances at the continental scale. [ABSTRACT FROM AUTHOR]

Efficient scale- and location-specific soil micronutrients management is important for crop yield and environmental quality. This usually requires knowledge on scale- and location-specific control of soil micronutrients, which is not readily available from the traditional correlation analysis. The objective of this study was to analyze the scale- and location-specific relationships between surface (0–20 cm) soil available micronutrients (Cu, Fe, Mn, and Zn) and environmental factors by wavelet coherency analysis. For this purpose, soil available micronutrients, soil pH, soil organic matter (SOM), and topographic factors were obtained at 1 km interval along a 117 km-transect in the arable land of Fen River basin, China. The results showed that Cu, Mn, and Zn were positively correlated with SOM at scales 32–40 km at all locations, while Fe was positively correlated with SOM at scales 7–16 km at locations 75–117 km. Soil pH had negative influences on Cu and Zn at scales 25–40 km at all locations and on Fe at scales 12–21 km at locations 1–64 km. Both Cu and Zn had significantly negative relationships with aspect at scales 15–32 km at all locations, which cannot be detected at the sampling scale by the traditional correlation analysis. Wetness index had a significant impact on the distribution of Zn at scales 24–38 km at all locations and at scales 14–24 km at locations 1–60 km. Although elevation and slope showed significant correlations with Cu, Mn, and Zn at the sampling scale, wavelet coherence did not show any significant correlations in the scale-location domain. Therefore, the relationships of soil available micronutrients and influencing factors were scale- and location-dependent, which implies that different management practices are needed at different scales and locations to improve the global level of soil available micronutrients in the arable land of Fen River basin. [ABSTRACT FROM AUTHOR]

This paper describes the impact of drainage and grassland use on selected soil parameters (e.g. organic carbon content, bulk density) of typical fen soils in Northeast Germany and, hence, their influence on grassland productivity. A broad investigation of site conditions has been realized at 23 grassland fields concerning soil properties, vegetation attributes and groundwater dynamics. Collectively selected fields represent characteristic types of grassland management and stages of moorsh-forming process. Concerning the entire sample, site conditions of agriculturally used peatlands vary strongly. Based on that complex data-set, the importance of defined potential impact factors on grassland production is tested and expressed in a linear regression model. Annual yield of the 2011 growing season, as a quantitative parameter of grassland productivity, does not indicate any correlation to site-specific conditions or cultivation strategy. In contrast, energy content as a qualitative measure varies strongly in relation to defined environmental parameters. Model performance is indicated with an adjusted R-square of 0.89 while the main impact factors are annual use frequency, mean summer water table (MSWT), maximum groundwater drawdown (GWmax), and organic carbon content (Corg). [ABSTRACT FROM AUTHOR]

Prairie fens are globally vulnerable wetlands that are considered a conservation priority due to threats to their high biodiversity and hydrological functions. Establishing a thorough and repeatable plant sampling protocol is critical to evaluating conservation and management initiatives. Our goal was to evaluate a sample methodology designed to assess prairie fen plant diversity and determine if it produced results (1) representative of site diversity, (2) comparable among fens, and (3) efficient to collect. Nineteen fens between 8.5 and 28.4 ha were surveyed twice within one growing season during 2012 and 2013 field seasons using an area-proportional, random design. The turnover in species between spring and summer sampling periods within a site ranged from 8 to 50 %. Sample coverage of total estimated plant species richness ranged from 84.8 to 95.0 % with a mean of 90.1 %. We compared results from our area-proportional, random design to simulated random samples of 10, 15, 20, 25, 30, 35 and 40 quadrats per site. No significant difference was found in sample coverage per fen when using sampling rates of 25, 30, or 35 quadrats per site versus the area-proportional design. Shannon's diversity index and floristic quality index differed by sample period and number of quadrats sampled per fen. Our sample design produced acceptable levels of coverage and facilitated comparisons across fens. Our methodology could be applied to future research, restoration monitoring, and conservation planning efforts in Midwestern prairie fens. [ABSTRACT FROM AUTHOR]

While fens provide a host of ecosystem services, those located at the base of river terraces are under threat from upgradient agricultural activities. We investigated a fen located along the boundary of the highly agricultural terrace and modern floodplain of the Cedar River in southeast Iowa using a transect of groundwater and surface water monitoring points. During the three-year monitoring period, the water table level in the terrace fluctuated 55 cm in the terrace, but hydraulic head in the fen varied only 18 cm during a severe drought that occurred in the region. Fen water table levels were significantly related to those measured in the adjacent terrace but groundwater flow to the fen from regional aquifer sources appeared to provide resilience against large fluctuations in fen water table levels. Terrace groundwater discharging into the fen from a spring at the terrace base had NO3-N concentrations as high as 16 mg/l, averaging approximately 8 mg/l during the study. Concentrations were significantly lower in fen groundwater, likely due in part to denitrification occurring in the organic-rich fen deposits. PO4-P concentrations were less variable (ranging from 0.04 to 0.1 mg/l) but were significantly higher (1.2 mg/l) in the low-redox fen groundwater. Conservation of these unique and high-value terrace-fen ecosystems should be made a priority through additional hydrologic investigation and local land management. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Floating fen ecosystems are home to several protected habitats and species. Their development and conservation require special attention regarding water management. Although they are known to be heterogeneous and partially buoyant, their root mats are simulated in hydrological models as homogeneous, static systems. The objective of this study is to quantify root mat heterogeneity and buoyancy and to assess their effects on groundwater flow and transport, and to determine if these factors need to be taken into account in modelling. We conducted field measurements of root mat heterogeneity and buoyancy in the 'Nieuwkoopse Plassen', the Netherlands. We found that hydraulic conductivity varied over four orders of magnitude and negatively correlated with degree of decomposition, resulting in a zonation of high conductivity near the surface and low conductivity in the deeper layers. Also, we found that the root mat moved vertically with the surface water. It became more buoyant with higher temperatures, but less buoyant with increasing groundwater levels relative to the surface. We implemented the findings in a semi-steady state hydrological model of a floating fen to compare the effects with other parameters. The profound heterogeneity had a limited effect on the water budget, but a clear effect on the flow lines and thus should be taken into account when modelling transport processes in floating fens. Although buoyancy affected the relative groundwater level near the root mat edge, it did not affect the water budget or the flow lines and may therefore be neglected in water budget modelling. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fens, which are among the most biodiverse of wetland types in the USA, typically occur in glacial landscapes characterized by geo-morphologic variability at multiple spatial scales. As a result, the hydrologic systems that sustain fens are complex and not well understood. Traditional approaches for characterizing such systems use simplifying assumptions that cannot adequately capture the impact of variability in geology and topography. In this study, a hierarchical, multi-scale groundwater modelling approach coupled with a geologic model is used to understand the hydrology of a fen in Michigan. This approach uses high-resolution data to simulate the multi-scale topographic and hydrologic framework and lithologic data from more than 8500 boreholes in a statewide water well database to capture the complex geology. A hierarchy of dynamically linked models is developed that simulates groundwater flow at all scales of interest and to delineate the areas that contribute groundwater to the fen. The results show the fen receiving groundwater from multiple sources: an adjacent wetland, local recharge, a nearby lake and a regional groundwater mound. Water from the regional mound flows to an intermediate source before reaching the fen, forming a 'cascading' connection, while other sources provide water through 'direct' connections. The regional mound is also the source of water to other fens, streams and lakes in this area, thus creating a large, interconnected hydrologic system that sustains the entire ecosystem. In order to sustainably manage such systems, conservation efforts must include both site-based protection and management, as well as regional protection and management of groundwater source areas. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Several boreal fens belong to the patterned fen category, which is composed of two compartments, the pool (or hollow), and the string (or hummock) compartments. Both compartments are distributed perpendicular to the mire slope and drainage flow. The surface of patterned fens is repeatedly invaded by water, which is known to affect the original pool-string pattern through the creation and enlargement of pools, a process caused by the action of aqualysis. Aqualysis refers to the destruction of the vegetation cover by flooding of low-elevated strings or lawns causing the formation and enlargement of pools. It is argued here that the nature and composition of the pool structure (number and size) reveal the state of development of patterned fens of the boreal environment. Quantitative and spatial data for pool size structure in 24 fens of northern Quebec, including 4881 pools, were used for the assessment of patterned fen development. Among the main factors influencing patterned fen development, area and slope contribute to the construction of the peatland surface. Also, watershed area, alternating strings and hollows, and peat thickness all facilitate pool creation and expansion. The construction of the pool structure of most fens has been a long process of ecosystem building. This probably explains why most sloping fens, i.e, moderate- and steep-sloping fens, are today at an equilibrium stage characterized by the coexistence of pools of all sizes with the smallest pools being the most numerous. In contrast, most low-sloping fens have developed toward a lacustrine stage with a bimodal distribution of small and very large pools. Boreal patterned fens of all developmental stages will be subject to increased pool size and number in the near future if more humid climatic conditions prevail. [ABSTRACT FROM AUTHOR]

The genetic diversity of five populations ofLiparis loeseliifrom two regions of Poland, Podlachia and Silesia, was compared with respect to minisatellite markers. Moreover, the standard 2-loci barcode DNA regions,rbcLandmatKgenes, as well as an additional regiontrnL-Ffrom chloroplast and ITS2 from nuclear genome were studied. The total genetic diversity at the species level amounted toHT= 0.356. The analysis of molecular variance revealed that 58% of genetic variation was distributed within populations, 2% among populations, and 40% between regions from NE Poland (Podlachia), and S Poland (Silesia). Nei's genetic distances indicated that specimens from the Podlachia population were genetically isolated from Silesian ones. Two genetic barriers among the studied populations were found: one barrier separated the Podlachian population from all Silesian populations and another barrier divided Kuźnica Warężyńska population from other Silesian populations. Based on barcode sequences it was found that all the examined samples were identical with respect to all the studied DNA regions.Liparisloeselii trnL-Fregion sequences were detected for the first time and they can be useful as complementary barcodes for this species. The analysed sequences ofL. loeseliiare fully consistent with sequences of specimens originating from the UK, Canada, Czech Republic, Hungary, Sweden, Italy, and Russia. [ABSTRACT FROM AUTHOR]

Natural Boreal saline fens provide analogues for reclaimed wetland systems constructed with sodium-rich tailings materials. These natural analogues can improve our understanding of vegetative controls on dominant ecohydrological processes (i.e. evapotranspiration (ET)) in constructed landscapes. Therefore, the objective of this study is to characterize ET within a natural boreal saline fen over a growing season to determine the primary hydro-climatic controls using community-scale ET measurements targeting dominant vegetation communities within different microforms along with environmental controls. ET rates were highest during periods of peak vegetation growth and temperatures between June and August, with rates decreasing slightly in July. Vegetation species' physiology was the dominant variable governing ET. The more salt tolerant species maintained higher ET rates despite the lower leaf area index and water table levels found within these species. The lower ET rates measured in July can be attributed to high water tables from above average precipitation causing soil inundation and salt stress, increasing stomatal closure. However, community plots containing Triglochin maritima maintained transpiration rates under the coupled stress conditions. Therefore, this is a potentially important species for use in boreal reclamation planting schemes. Last, the findings emphasize that the dominant vegetation selected for reclamation projects must coincide with the materials used (peat and subsurface materials), as results within this study demonstrate that some native boreal fen species ( Calamagrostis inexpansa, Hordeum jubatum, and Juncus balticus) were unable to maintain transpiration rates during flood and saline conditions that can occur within the mining area of this region. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A greenhouse experiment was set up to investigate if infrequently and frequently occurring species respond differently to simulated habitat changes. Two frequently occurring (Bryum pseudotriquetrumandCalliergonella cuspidata)and two infrequently occurring (Hamatocaulis vernicosusandPaludella squarrosa) rich fen bryophytes were grown in mixed culture and subjected to rainwater or groundwater and three levels of N, ammonium nitrate (0, 1 and 3 mg N L–1) and P, potassium phosphate (0, 0.05 and 0.1 mg P/L). All species responded negatively to higher N-levels and three of the four species responded negatively to rainwater and higher P-levels.C. cuspidatahad highest relative growth rate (RGR) in all treatments, and the infrequently occurring species had lower RGR and were more negatively affected by high levels of N than the frequently occurring species. A negative effect of rainwater seemed to be caused by higher background levels of N in rainwater compared to groundwater. We found a negative effect of high initial bryophyte density in three of the four species indicating density-dependent inhibition between species. We suggest that maintenance of oligotrophic conditions by recharge of nutrient-poor groundwater is vital for conservation of infrequently as well as frequently occurring rich fen bryophytes. [ABSTRACT FROM AUTHOR]

Peatlands are one of the major sources of the powerful greenhouse gas methane (CH 4 ). Our aim was to detect responses of methanogenic archaeal and methane-oxidizing bacterial (MOB) communities that control the methane (CH 4 ) cycle to climatic warming. This study took place in two boreal fens three years after experimental warming in un-manipulated wet and drier regimes, thus simulating future climate scenarios. We determined active methanogen and MOB communities as transcripts of mcrA and pmoA genes, along with the abundance of these genes, CH 4 production and oxidation potentials, and in situ CH 4 fluxes. Methanogenic community remained similar, although methanogen abundance decreased after warming. In the wet regime, this decrease resulted in a small but significant reduction on the potential CH 4 production in such peat layers where the average production potential was high. Drying alone, however, reduced the potential CH 4 production more than warming, and this impact was strong enough to mask the small warming impact in the drier regime. Warming did not affect the MOB community or the potential CH 4 oxidation in the wet regime; however, type Ib MOB abundance decreased and MOB related to genus Methylocapsa became typical after warming in the drier regime of the southern fen. The in situ measured CH 4 fluxes indicated similar patterns as potential measurements; both warming and drying reduced methane emissions, drying more than warming. These results indicate that methanogens and MOB may have different controlling patterns on CH 4 fluxes when facing global warming. These patterns may further differ not only between moisture regimes, but inside the same habitat type, here boreal fen. Irrespective of this variation, the in situ CH 4 fluxes still seem to respond similarly across sites. [ABSTRACT FROM AUTHOR]

Methane emission from the grass-moss fens of the Western Siberia subtaiga was studied using a static chamber method. It was established that CH flux median ± half of the interquartile range in the studied wetland ecosystems constituted 4.9 ± 2.9 mg of CH/(m h). It was shown that such a high spatial variability of emission is caused mainly by the difference in the water table level. It was found that, in these observations, a higher water table level correlates with lower emission values. The causes of this phenomenon are discussed, and recommendations for conducting field studies for estimating the regional flux are given. [ABSTRACT FROM AUTHOR]

In regions with intensive agriculture, water level fluctuation in wetlands has generally become constricted within narrow limits. Water authorities are, however, considering the re-establishment of fluctuating water levels as a management tool in biodiverse, base-rich fens (‘rich fens’). This includes temporary inundation with surface water from ditches, which may play an important role in counteracting acidification in order to conserve and restore biodiversity. Inundation may result in an increased acid neutralizing capacity (ANC) for two reasons: infiltration of base-rich inundation water into peat soils, and microbial alkalinity generation under anaerobic conditions. The main objectives of this study were to test whether short-term (2 weeks) summer inundation is more effective than short-term winter inundation to restore the ANC in the upper 10 cm of non-floating peat soils, and to explain potential differences. Large-scale field experiments were conducted for five years in base-rich fens and Sphagnum-dominated poor fens. Winter inundation did not result in increased porewater ANC, because infiltration was inhibited in the waterlogged peat and evapotranspiration rates were relatively low. Also, low temperatures limit microbial alkalinity generation. In summer, however, when temperature and evapotranspiration rates are higher, inundation resulted in increased porewater Ca and HCO3- concentrations, but only in areas with characteristic rich fen bryophytes. This increase was not only due to stronger infiltration into the soil, but also to higher microbial alkalinity generation under anaerobic conditions. In contrast, porewater ANC did not increase in Sphagnum-plots as a result of the ability of Sphagnum spp. to acidify their environment. In both rich and poor fens, flooding-induced P-mobilization remained sufficiently low to safeguard P-limited vegetation. NO3- and NH4+ dynamics showed no considerable changes either. In conclusion, short-term summer inundation with base-rich and nutrient-poor surface water is considered beneficial in the management of non-floating rich fens, and much more effective than winter inundation. [ABSTRACT FROM AUTHOR]

Wetland restoration management is an important tool for stakeholders and practitioners to mitigate climate change and preserve ecological functioning. Various approaches to modifying the water management of a catchment for restoration purposes exist and were performed in a preservation area in northwest Germany. To validate the effect of the re-wetting practice, a monitoring network of 46 wells was established and monthly readings were taken from 1997 onwards. A declining trend in water table depth was present at 39 wells and equaled on average a lowering of 20 cm during the study period from 1997 to 2012. So far, half of the trend lines are above 40 cm below ground, which is an indicator of an effective re-wetting practice, but they will decline below this threshold until 2032 according to linear regression analysis. The progress of water table depths might be accelerated by climate change. According to the meteorological forecast, air temperatures will rise and the annual precipitation pattern will change. Thus, the climatic water balance tends toward more negative values in the summer and positive values in the winter, favoring an earlier and more intense water table draw-down. Because root water extraction from shallow groundwater is limited to a certain depth, the forecast of water table depth development according to the recent trend depicts a worst-case scenario. Nevertheless, the results emphasize that restoration management should be validated and has to be adapted in certain ways when mitigating the impact of climate change. [ABSTRACT FROM AUTHOR]

This paper presents a palaeoenvironmental reconstruction of the Wilczków fen (central Poland). The fen developed in an inactive valley at the onset of the Holocene (~11 ka BP) and peat accumulation lasted until 5.7 ka BP. Multi-proxy reconstructions were made on the basis of palaeobotanical, cladoceran, chironomid, beetle and geochemical analyses. A Kohonen self-organizing map ( SOM, unsupervised artificial neural network) of the biotic sequence distinguished four stages of fen history. Stage X1 (11.0-10.7 ka BP) was relatively wet and cool. Organic matter started to accumulate but the habitat conditions remained unstable. Moss, sedge and fern communities then developed. Sedimentary changes reveal an intensive groundwater supply at that time. Numerous and diverse chironomid and cladoceran subfossils indicate nearly permanent aquatic conditions. During stage Y1 (10.6-9.2 ka BP) conditions were dry and the upper peat layer desiccated. Cladocera nearly disappeared whereas chironomids were represented by semi-terrestrial and predatory (Tanypodinae) species. Conditions started to be more reducing. All the remaining samples belonged to the interweaving stages X2 and Y2. Stage Y2 (mostly 9.1-7.3 and 6.0-5.7 ka BP) was also dry but humidity increased towards the top. Oxidizing conditions occurred and the pH became more alkaline, favouring Cladium mariscus. The basin received mostly allochthonous matter input at that time. Stage X2 (mostly 6.8-6.1 ka BP) was humid and warm. The groundwater supply remained low but there was an increase in precipitation, changing local conditions to ombrotrophic. Species-rich chironomid and cladoceran communities were associated with temporary pools. Finally, conditions returned to those characteristic of stage Y2. The presented reconstruction documents long-term abiotic and biotic changes determined by water supply, including groundwater outflow, which have rarely been detected at a multi-proxy scale. We show that inactivated valley fens are sensitive to climate-driven hydrological fluctuations. Kohonen neural networks appear to be a promising method for analysing variability in multi-proxy data. [ABSTRACT FROM AUTHOR]

The reclamation of fen peatlands on post-oil sand development landscapes involves the transfer of peat from a donor fen to form the upper 2 m of a sediments-filled pit resulting from open-pit mining. The placed peat serves two major functions of attenuating the upwelling of dissolved solutes from the underlying tailing sediments to the rooting zone, and as fen vegetation establishment substrate. However, the modifications (e.g., decomposition and fragmentation) resulting from salvage and transfer practices (e.g., dewatering and loading/placement with earth-moving equipment) could impact the potentials of the placed peat to support ecohydrological functions in the constructed fen. Thus, we conducted a study to evaluate the impact of these practices on the biogeochemical and hydrologic functioning of a constructed fen. Peat cores were extracted along transects in the donor fen before peat transfer, and after placement in the constructed fen. Cores were also taken from a natural reference site to serve as the nearest possible comparison to donor site conditions prior to dewatering. The cores were subsampled and analyzed for selected physicochemical and hydrophysical properties. Relative to the reference site, our results indicates a higher surface bulk density, and accelerated mineralization of organic-bound nutrients in the dewatered donor peat. Following transfer of peat to the constructed fen, changes in hydrophysical properties were reflected in a reduction of the horizontal/vertical anisotropy ratio from 1.5 to 1, which could impact the vertical fluxes of water. However this impact is likely less than that of the heterogeneity associated with the fragmentation of the placed peat. Hence, we recommend some management practices that can alleviate the modifications resulting from contemporary operational practices. [ABSTRACT FROM AUTHOR]

The aim of this study was to establish the main drivers of the spatial variability in growing season CH flux within an arctic wetland ecosystem. During 3 years (2011-2013) we measured CH flux and potential drivers, e.g., CO fluxes (net ecosystem exchange (NEE), gross primary productivity (GPP) and ecosystem respiration), temperature, water table depth, pore-water concentration of organic acids (e.g., acetate) and the vascular plant composition and density. The study included 16-20 main plots (C) and in 2013 also experimental plots (10 excluded muskoxen grazing, 9 snow fence and 10 automated chamber plots) distributed over 0.3 km. The results show a 1.8-times difference in CH flux magnitude inter-annually and 9- to 35-times spatially (depending on year and treatment). During all 3 years GPP was a strong driver of the variability in C plots. Accordingly, the plant productivity related variables NEE, GPP and acetate were singled out as the strongest drivers of the variability in 2013, when all variables were measured on a majority of the plots. These variables were equally strong drivers of the spatial variability in CH flux regardless of whether experimental plots were included in the analysis or not. The density of Eriophorum scheuchzeri was the strongest driver of the spatial variability in NEE, GPP and acetate. In conclusion, changes in vegetation composition or productivity of wet arctic ecosystems will have large impacts on their carbon balance and CH flux, irrespective of whether these changes are driven directly by climate change or by biotic interactions, such as grazing. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the effects of fen rewetting on carabid beetle and vascular plant assemblages within riverine fens along the river Peene in north-eastern Germany. Drained (silage grassland), rewetted (restored formerly drained silage grassland), and near-natural (fairly pristine) stands were compared. Eighty-four beetle species (7,267 individuals) and 135 plant species were recorded. The richness of vascular plant species and the number of endangered species were highest on near-natural fens. Fourteen years of rewetting did not increase plant species numbers compared with drained fens. For carabid beetles, however, species richness and the number of stenotopic species were highest on rewetted fens. Rewetting caused the replacement of generalist carabids by wetland specialists, but did not provide suitable habitat for specialist fen carabids or for plant species of oligo- or mesotrophic fen communities. Therefore, raising the water table on fens with nutrient-rich, degraded peat was not sufficient for restoring species assemblages of intact fens, although water level was the most important environmental factor separating species assemblages. Our study illustrated that insects and plants may respond differentially to restoration, stressing the need to consider different taxa when assessing the efficiency of fen restoration. Furthermore, species assemblages of intact fens could not be restored within 14 years, highlighting the importance of conserving pristine habitat. [ABSTRACT FROM AUTHOR]

Agricultural legacies shape soil seed banks, which in turn alter subsequent vegetation recovery. However, the role of legacy-impacted seed banks in shaping wetland-vegetation recovery is not well studied, and hydrologic context may alter impacts of seed bank legacies on extant vegetation. Here we compare seed banks and extant vegetation of four plowed fens to an on-site reference fen to determine (i) if plowing legacies have altered seed banks, (ii) if 13-year post-abandonment vegetation differs from the reference fen, and (iii) whether extant vegetation composition is different than that of seed banks in both reference and plowed fens. The relative abundance of key native graminoid and fen specialist species was greatly reduced in plowed-fen seed banks compared to the reference fen, while weedy/invasive species present in the post-agricultural fens' seed banks were absent from the reference fen. The depletion of normally dominant native graminoids from seed banks was reflected in extant vegetation. However, shallow water tables predicted shifts in extant vegetation from weedy-mesic annuals to areas dominated by either native clonal forbs or Phalaris arundinacea. In general, plowed plant communities had decreases relative abundance of weedy-mesic species and increased relative abundance clonal forbs or clonal-invasive graminoids compared to seed banks. Our results suggest that while depletion of native graminoids from seed banks plays a part in vegetation recovery, the abundance of weedy-mesic species was not reflected in the recovering vegetation in wetter areas. [ABSTRACT FROM AUTHOR]

Global land-use intensification and drainage has altered the biogeochemical properties of many peatlands, and concomitant eutrophication has led to a loss of low-competitive fen species. We investigated the hypothesis that removal of a degraded and eutrophied top peat layer, thereby exposing an underlying peat layer, can improve conditions for rich fen restoration. We studied the long-term (3–18 years) effects of past topsoil removal in six rich fens in Western Europe by comparing topsoil removal plots with (untouched) control plots. Overall, topsoil removal plots were characterized by lower bulk densities and soil nutrient pools of P and KCl-extractable NH 4 + , while organic matter contents and soil C:N ratios were higher. Pore water concentrations of NO 3 − and NH 4 + also decreased in the topsoil removal plots, while concentrations of base cations (Ca 2+ , Mg 2+ , Na + , K + ) and HCO 3 − increased. Furthermore, lower nutrient levels appeared to restrict herb biomass production in the topsoil removal plots, so that optimized light conditions led to the establishment of light-demanding target species and a significant increase in bryophyte cover. Multivariate analysis revealed that most variation in vegetation assembly was due to higher groundwater levels in the topsoil removal plots, closely followed by a higher relative light intensity (RLI) at surface level, lower pore water nutrient (NH 4 + ) concentrations, and higher concentrations of base cations. We conclude that topsoil removal can be an effective mechanism to “reset” a degraded peatland to its initial state of nutrient limitation, base saturation and high availability of light, thereby improving the conservation prospects of endangered rich fen communities. [ABSTRACT FROM AUTHOR]

To identify optimal habitat for the Aquatic Warbler Acrocephalus paludicola, a flagship species of fen mires, we related numbers of singing males to habitat variables in all core breeding sites in eastern Poland. The density of male Aquatic Warblers increased with increasing ground cover by water and mosses and litter layer height, and was highest where vegetation was 60-90 cm tall. Male densities also increased with the biomass of arthropods > 10 mm length, estimated by sweep netting, and with the abundance of spiders, estimated by pan trapping. We suggest that habitat management should take into account species-specific morphological adaptations, nest safety and arthropod productivity. Prevention of vegetation succession is a conservation priority for open fen mires. However, modern management practices to achieve this, especially mowing using tracked vehicles, should be evaluated and optimized to ensure that such practices do not adversely affect the long-term development of moss cover and litter structure. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effect of environment and species dispersal limitations may both significantly affect the structure of ecological metacommunities but there have been a relatively few attempts to separate their effects in aquatic assemblages. In this paper, we tested the relative importance of environment and space on the ostracod assemblages on a regional scale (encompassing ca 15,800 km) in 74 permanent helocrene springs. We used Canonical Correspondence Analysis and Variation Partitioning to test the unique and shared effects of environment and space, represented by Principal Coordinates of Neighbor Matrices. We found that ostracod assemblages were significantly influenced by environment (mainly the mineral content and TOC) and space (roughly the west-east direction); the shared effect was relatively low. A unique effect of space was found for both species strongly associated with spring habitats and for euryoecious species found in the springs. We suggest that the passive dispersal in ostracods is random and infrequent between the isolated spring fens and produces spatially structured assemblages. [ABSTRACT FROM AUTHOR]

Background:Many minerotrophic fens in Central Europe have undergone similar sequences of land-use transformation. Drained and used as meadows or pastures for decades in the twentieth century, they were abandoned in the 1990s due to changes in agricultural economics. This sequence of land-use change has a severe impact on vegetation and is likely to initiate secondary succession and is possibly leading to an impoverishment in species diversity and to taxonomic homogenisation. Aims:We assess the impact of agricultural use and subsequent abandonment on vegetation composition in a percolation fen in north Germany and characterise successional changes and changes in abiotic site conditions. Methods:In 2010, we resampled 77 plots of a phytosociological survey from 1967–1970 in a lowland percolation mire complex in the lower Recknitz valley, north-east Germany. These included three characteristic vegetation types of percolation fens. To investigate and quantify vegetation changes we used dissimilarity measures, diversity metrics and ecological species indicator values. Results:Overall species richness declined only slightly while there was a more pronounced decrease in species richness at the plot level in all recorded vegetation types, resulting in increased beta diversity. Generalist and nitrophilous species increased in abundance, indicating ongoing succession. Conclusions:Drainage for agricultural use and subsequent abandonment has long-lasting effects. Altered hydrological and nutrient status of the fen soil has initiated secondary succession. There is indication of an extinction debt that in the future may lead to an impoverishment of species diversity in the area. Conservation of open mesotrophic fen species may thus only be achieved if moderate use is continued and hydrologic conservation measures are applied on wide contiguous areas. [ABSTRACT FROM AUTHOR]

ABSTRACT Fens represent a large array of ecosystem services, including the highest biodiversity found among wetlands, hydrological services, water purification and carbon sequestration. Land-use change and drainage has severely damaged or annihilated these services in many parts of North America and Europe; restoration plans are urgently needed at the landscape level. We review the major constraints on the restoration of rich fens and fen water bodies in agricultural areas in Europe and disturbed landscapes in North America: ( i) habitat quality problems: drought, eutrophication, acidification, and toxicity, and ( ii) recolonization problems: species pools, ecosystem fragmentation and connectivity, genetic variability, and invasive species; and here provide possible solutions. We discuss both positive and negative consequences of restoration measures, and their causes. The restoration of wetland ecosystem functioning and services has, for a long time, been based on a trial-and-error approach. By presenting research and practice on the restoration of rich fen ecosystems within agricultural areas, we demonstrate the importance of biogeochemical and ecological knowledge at different spatial scales for the management and restoration of biodiversity, water quality, carbon sequestration and other ecosystem services, especially in a changing climate. We define target processes that enable scientists, nature managers, water managers and policy makers to choose between different measures and to predict restoration prospects for different types of deteriorated fens and their starting conditions. [ABSTRACT FROM AUTHOR]

Questions What is the distribution of base-rich fen vegetation and the specialist species along European biogeographic regions? How do the gradients in species composition correlate to geography and climate at continental scale? What are the implications of such patterns for the classification of these habitats? Location Fifteen countries of Central, Western and Northern Europe. Methods We compiled a vegetation plot database of base-rich fens and related communities including vascular plants and bryophytes. The initial data set with 6943 plots was filtered according to the presence of specialists using discriminant analysis. We used DCA to analyse the correlation of species composition with geography and climate, and kriging interpolation for mapping gradients in the study area. Modified TWINSPAN was used to detect major vegetation groups. The results of the whole data set (plot size 1-100 m2) were compared with those obtained from two subsets with plots of 1-5 m2 and 6-30 m2. Results Most of the specialists were distributed among all the biogeographic regions, but many were more represented in the Alpine than in the Atlantic, Boreal and Continental regions. Variation in species composition was mainly correlated to temperature, precipitation and latitude in the three data sets, showing a major gradient from (1) alpine belt fens characterized by spring species to (2) small sedge fens mainly distributed in mountain regions and (3) boreo-temperate fens reflecting waterlogged conditions. Conclusions Base-rich fen communities are widely distributed across European biogeographic regions, but the Alpine region can be considered as the compositional centre of this vegetation type. Large-scale gradients of species composition are mainly explained by climate, while the influence of latitude is probably correlated to increasing water table in the boreo-temperate regions. These gradients can be better understood by differentiating three major vegetation types, which should be considered when establishing classification systems of base-rich fens in Europe. [ABSTRACT FROM AUTHOR]

Hydrological effects of groundwater abstraction near a Danish river valley have been assessed by integrated hydrological modelling. The study site contains groundwater-dependent terrestrial ecosystems in terms of fen and spring habitats that are highly dependent on regional and local scale hydrology. Fens are rare and threatened worldwide due to pressures from agriculture, to lack of appropriate management and to altered catchment hydrology. A solid foundation for hydrological modelling was established based on intensive monitoring at the site, combined with full-scale pumping tests in the area. A regional groundwater model was used to describe the dynamics in groundwater recharge and the large-scale discharge to streams. A local grid refinement approach was then applied in a detailed assessment of damage in order to balance the computational effort and the need for a high spatial resolution. A considerable flow reduction in the natural spring was monitored during a full-scale pumping test while no significant effects on the water table in the fen habitats were observed. A modelled abstraction scenario predicted a lowering of 2-3 cm in the centre of the main fen area during summer periods. The predicted change in water table conditions in the fen habitat is compared to the variability found in 35 Danish fens, and the ecological response is discussed based on statistical water-level vegetation relations. The results provide a rare quantitative foundation for decision making in relation to management of groundwater-dependent terrestrial ecosystems. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Fens and concomitantly the associated species assemblages have undergone dramatic declines in recent decades. Given that many remaining or restored fens are currently lying fallow, an important question is which management regime, if any, is most effective in preserving fen biodiversity. Against this background we here investigate the effects of five management regimes (intensive grassland, moist meadows, summer harvested sites, winter harvested sites, fallows) on three insect taxa (butterflies, grasshoppers, carabid beetles) in riverine fens in north-eastern Germany. Butterflies and grasshoppers showed highest species numbers, diversity and numbers of threatened species on moist meadows and were detrimentally affected by high vegetation. In contrast, ground dwelling carabid beetles were less strongly affected by different management regimes, but responded very sensitive to drainage. Winter harvested sites and fallows seemed to be particularly beneficial to carabid beetles. Overall, drained, intensive grassland was not suitable for preserving fen-specific communities, while extensively managed moist meadows harboured overall the highest numbers of threatened species. We conclude that in terms of management maintaining high water tables is most important. Furthermore, some management seems necessary to maintain stands with lower vegetation turf for associated species. However, care is needed to also maintain fallows and to consider the specific demands of some highly endangered, management-sensitive species. [ABSTRACT FROM AUTHOR]

Water levels in areas with intensive agriculture have often been strictly controlled for decades. Recently, more natural fluctuating water levels have been propagated to improve the ecological quality of wetlands in these areas. This study investigated the effects of water levels on protected base-rich mesotrophic fens during winter and summer., We used a mesocosm approach to simulate water level fluctuations under winter and summer conditions (light and temperature) to test the effects of water level on the biogeochemistry and vegetation of two highly endangered fen types with the brownmosses Scorpidium scorpioides and Hamatocaulis vernicosus as dominant mosses., Both species showed decreased photosynthetic capacity at lower water levels. These levels also resulted in decreased alkalinity due to oxidation processes in the moss layer. High water levels led to increased pH and alkalinity, due to reduction processes and infiltration of base-rich water., For the P-limited S. scorpioides mesocosms, high water levels did not lead to P mobilization or to significant changes in biomass production, P uptake and N:P ratios. However, for the mesocosms with H. vernicosus, where P limitation was not obvious, high water levels did result in P mobilization and increased P availability due to iron reduction. The lower P mobilization for S. scorpioides appeared to be related to lower total soil P content and higher Fe:P and Ca:P ratios. Although high water levels resulted in the accumulation of ammonium under winter conditions, this did not happen under summer conditions, making ammonium toxicity unlikely., Synthesis and applications. Our results suggest that low water levels could hamper protected brownmosses in rich fens, especially during the summer. In contrast, inundations may have a positive effect on rich fens by increasing the alkalinity. However, inundations may lead to eutrophication due to internal P mobilization in soils with a high total P content and low Fe:P ratio. Therefore, we recommend that soils with high total P content and low Fe:P ratios should not be flooded. [ABSTRACT FROM AUTHOR]