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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]

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]

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]

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]

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]