Calcareous Fens Research Articles

Drivers for the Diversity of Mollusc Communities in Unique Calcareous Fen Habitats

The research was carried out in calcareous fen habitats which share coverage with Natura 2000 sites designated under the EU Habitats and the Birds Directive. A total of 27 taxa of molluscs were recorded: 23 gastropod and 4 bivalve species. Anisus vorticulus, one of the species of Community interest whose conservation requires designation of special conservation areas within the Habitats Directive Natura 2000, was subrecedent and accedent in mollusc communities. Calcareous fen habitats offer the aquatic organisms harsh environmental conditions including a relatively high temperature of the water up to 33.29 °C (undrained fens), oxygen deficits in the water, high pH of up to 11.08 (fen pools) and conductivity above 3000 μS cm−1 (fen ditches). Therefore molluscs have to face extreme environmental conditions. Temperature of the water, pH, dissolved oxygen and conductivity were the parameters most associated with the distribution of mollusc species in the calcareous fen habitats. The abundance of submerged and floating macrophytes, the degree of habitat persistence and the fish predation pressure on molluscs also exerted a significant effect on their distribution. The calcareous fen habitats that are listed in Annex I of the European Union Habitats Directive create a unique valuable ecosystem that contributes to the natural diversity of aquatic organisms.

Caddisflies (Trichoptera) of Protected Calcareous Fen Habitats: Assemblages, Environmental Drivers, Indicator Species, and Conservation Issues.

The caddisflies (Trichoptera) of calcareous fen habitats, in contrast to those of other peatland types, have been poorly researched. We thus conducted a two-year study in south-eastern Poland encompassing four types of such habitats-drained and undrained fens and water bodies (pools and ditches) located within the fens-in order to define trichopteran reference assemblages (PCoA), indicator species (IndVal analysis), and the drivers (both natural and those associated with landscape management, including area protection) responsible for caddisfly species distribution (CCA). The most important environmental driver was habitat persistence. Distance-based RDA analysis revealed a distinct pattern in the distribution of species with or without diapause along the persistence gradient. Environmental drivers associated with plants were also crucial for both fens and water bodies. The key factor influencing the caddisfly assemblages of pools and ditches was the use and management of the surrounding land, whereas in the fens, it was the level of area protection. Physical and chemical water parameters had no statistically significant impact on the assemblages. Some factors can be modified by humans (e.g., water level regulation, vegetation, and landscape management) to maintain healthy ecosystems for aquatic insects.

The future of carbon storage in calcareous fens depends on the balance between groundwater discharge and air temperature

Calcareous spring fens accumulate carbon-rich deposits through carbonate precipitation and slow organic-matter decomposition, which can be affected by a lowering water table. Ongoing climate change is altering the carbon balance and threatening the biota of these vulnerable ecosystems. Rising air temperatures intensify carbonate precipitation and may accelerate decomposition, which is also influenced by soil nutrients and soil temperature. These relationships complicate predictions of carbon storage in calcareous fens. Here, we measured summer mass loss and carbonate accumulation at 57 spots in 19 calcareous spring fens in the Western Carpathians using commercial green tea and rooibos, i.e., the tea bag method. Decomposition rates were determined by mass losses corrected for leaching. Structural equation modelling was used to test the causal relationships between air and soil temperature, water table, soil nutrient concentrations, and mass loss or carbonate accumulation. The results demonstrate that a lowering water table increases soil nitrogen, phosphorus, and potassium concentrations. Water table and air temperature positively affected carbonate accumulation for both types of tea bags. Rooibos decomposition rate decreased with increasing water table and decreasing soil phosphorus concentration. Overall, the role of hydrology appeared crucial for global change predictions. If increased precipitation or groundwater recharge keeps the water table high, as predicted for some areas, the rising temperature will intensify carbonate precipitation and shift the ecosystem from peat to tufa-forming. While this scenario is more conducive to maintaining biodiversity and sustainability of existing carbon sinks than an alternative scenario predicting decreasing discharge due to decreasing precipitation and increasing evapotranspiration, it depends on preserving and maintaining fens and natural landscape hydrology. This study demonstrates the utility of the tea bag method to test drivers of contrasting carbon accumulation processes in groundwater-dependent wetlands.

Lateglacial to Mid-Holocene history of Vasby Mose, eastern Sjælland, Denmark

We retrieved a sediment core from Vasby Mose, a calcareous fen on eastern Sjælland, Denmark. The record spans the period from c. 14 700 to 6800 cal. years BP. During the Lateglacial, Vasby Mose was a lake where minerogenic sandy and clayey sediments accumulated. In the early Lateglacial, from c. 14 700 to 13 200 cal. years BP, a tundralike open, treeless vegetation with Betula nana and Dryas octopetala was found in the region. During the Younger Dryas, a rich flora of aquatic plants was found in the lake. In the Early to Mid-Holocene, Vasby Mose was a spring-fed calcareous fen, with deposition of peat and tufa. The flora included the sedges Carex rostrata and Carex paniculata, the aquatic plant Menyathes trifoliata, the calciphilous reed plant Cladium mariscus and the today nationally extinct bryophyte Meesia triquetra. The fauna included aquatic mollusc taxa such as Pisidium sp., Valvata spp. And Bithynia tentaculate and terrestrial or semi-terrestrial species such as Galba truncatula, Euconolus cf. alderi, Succinea/Oxyloma, Zonitoides nitidus and Vallonia pulchella. The Preboreal oscillation and other Early Holocene climate events are seen as short-lived, wet intervals.

Ecophysiology of Endangered Plant Species Saussurea esthonica: Effect of Mineral Nutrient Availability and Soil Moisture

Saussurea esthonica is an endangered plant species typical for wet inland habitats such as calcareous fens. Due to its limited population size and distribution, non-invasive sampling of is important in the research of S. esthonica. The aim of the present study was to assess the effect of mineral nutrient availability and substrate moisture on the growth, physiological status, and mineral nutrition of S. esthonica. The non-destructive measurement of physiological parameters was performed in native habitats during three vegetative seasons, followed by two experiments in controlled conditions. Soil at the two Estonian sites had a relatively larger similarity in the composition of plant-available mineral nutrients in comparison to the two Latvian sites. The chlorophyll a fluorescence parameter Performance Index correlated with the total precipitation in the respective month before measurement, but no significant relationship with other environmental variables was found. For mineral nutrient experiments, plants were grown in four substrates with different mineral nutrient composition, resembling that of soil at different S. esthonica sites. Plant growth and physiological indices were significantly affected by the mineral composition of the substrate. Differences in leaf and root mineral nutrient concentrations of S. esthonica plants in part reflected differences in substrate mineral concentration. To evaluate the effect of soil moisture on growth and photosynthesis-associated parameters of S. esthonica, plants were cultivated in "Pope+" substrate at four different moisture treatments (dry, normal, wet, and waterlodged). The most intense growth of S. esthonica plants was evident in waterlodged conditions, which decreased with a decrease in soil moisture. The biomass of leaves increased by 106% and that of the roots increased by 72% as soil moisture increased from dry to normal. For waterlodged plants, leaf biomass increased by 263% and root biomass increased by 566%, in comparison to that for plants cultivated in dry substrate. Substrate drying had a more negative effect on the growth of S. esthonica plants in comparison to that of waterlodging, and this can be directly linked to prevalent hydrological conditions of an alkaline fen habitat native to the species. Therefore, the preservation of the natural water regime in natural habitats is critical to the conservation of the species.

Predictors of Calcareous Fen Floristic Quality in a Rapidly Urbanizing County

Predictors of Calcareous Fen Floristic Quality in a Rapidly Urbanizing County

Physiological responses of fen mosses along a nitrogen gradient point to competition restricting their fundamental niches

Nutrient availability determines vegetation patterns and ecological functioning of intact groundwater‐fed peatlands (fens). Bryophytes, commonly referred to as ‘brown mosses', dominate calcareous fens (rich fens), are an integral part of their unique biodiversity and contribute significantly to peat formation and carbon sequestration. Brown mosses are replaced by vascular plants as nutrient availability increases. The decline of brown mosses may either be due to their physiological intolerance of high nutrient levels or to them being outcompeted by vascular plants. We aimed to distinguish between these two hypotheses by investigating whether the ecological optima reflect the physiological optima of brown mosses. Eight brown moss species, common in calcareous fens of the northern hemisphere, were grown under a gradient of nitrogen and phosphorus availability. Biomass increment, chlorophyll content and biomass nutrient concentration were measured. All brown moss species studied achieved the highest growth rates and chlorophyll contents when grown under conditions of nitrogen and phosphorus concentrations higher than those where they occur naturally at the highest frequency. Two of the species showed no growth saturation even at the highest levels of nutrient availability, while the others appeared potassium‐limited at the highest N and P levels. Brown mosses dominate natural fens at the lower edge of their physiological optimum in terms of nutrient availability, i.e. their realized niche is much narrower than the fundamental one. Based on the literature, we argue that it is the competition for light with vascular plants which limits the occurrence of brown mosses in nutrient‐rich habitats and prevents them from occupying their entire fundamental niche.

The challenge of developing ecohydrological metrics for vegetation communities in calcareous fen wetland systems

Calcareous fens are peat-wetlands fed mainly by groundwater, located in topographic hollows and served by springs or seepages of water derived by contact with base-rich mineral ground. In the European Union they are protected habitats requiring special conservation measures. To better understand the environmental supporting conditions of alkaline fen habitat found in Ireland, a 2-years hydrological and hydrochemical monitoring programme was carried out on four contrasting fen sites that covered an ecohydrological gradient representing intact to highly degraded conditions. This paper presents a methodology (and its limitations) of how the evaluation of the temporal and spatial variability of the quality and hydrological dynamics associated with different representative vegetation communities within the four fens can be used to develop ecohydrological metrics for fen habitat. The conditions supporting fen habitat in “good” ecological condition, indicative of a functioning alkaline habitat, were determined and contrasted with conditions found in habitats deemed to be in “poor” ecological condition. Results indicate that an annual water level always above the ground surface within a threshold depth envelope of between 0.030 and 0.28 m is required for at least 60% of the year for healthy fen vegetation. In terms of hydrochemistry, higher concentrations of nutrients were found in the sediments at depth and the groundwater feed compared to the phreatic water table. This suggests the fens may be incorporating the incoming nutrients into their internal biogeochemical cycles and that there is a net accumulation of nutrients within the wetlands. Although envelopes of nutrient concentrations in the surface water of the fen associated with habitat in good ecological condition can be defined (e.g., dissolved reactive phosphorus concentrations of between 6 and 37 µg-P/l for PF1 habitat), these levels should be regarded as the water quality after the fen vegetation has effectively interacted with the higher incoming nutrient levels in the groundwater. Moreover, the local hydrogeological conditions that define groundwater pathways (and associated water quality impacts) in such calcareous fens, allied to the localized nature of these measurements in these field studies, makes it difficult to define groundwater water quality threshold values with any confidence.

Ecology of testate amoebae along an environmental gradient from bogs to calcareous fens in East-Central Europe: development of transfer functions for palaeoenvironmental reconstructions

Testate amoebae play an important role in biomonitoring and the understanding of peatland (palaeo)ecology. However, their application has been mainly limited to Sphagnum-dominated peatlands, especially ombrotrophic bogs. To facilitate wider use of these microorganisms, we explored their ecology along a gradient from mineral-poor acidic bogs to mineral-rich calcareous fens with tufa formation using a new calibration dataset of over 250 samples from East-Central Europe. Specifically, we examined environmental controls on testate amoebae along the complete gradient and separately in the minerotrophic (pH >5.5) and ombrotrophic (pH <5) parts. Based on these findings, we developed and statistically evaluated transfer function models for the dominant factors controlling the community composition of these protists. Multivariate statistical analysis showed that groundwater pH was the main driver of species composition in the full and minerotrophic datasets. In contrast, testate amoeba communities in the ombrotrophic dataset were primarily structured by depth to water table (DWT). Under leave-one-out cross-validation (LOO), the best-performing model for DWT gave a prediction error (RMSEP) of 5.43 cm. The most robust models for groundwater mineral richness yielded RMSEPLOO of 0.45 and 0.27 pH units, for the full and the minerotrophic dataset respectively. This is the first study to present a complete set of testate amoeba-based transfer functions that allow reconstructions of Holocene hydrochemical and hydrological (hydroclimatic) variability in different mire types within one region. The new models open up the possibility for testate amoebae to become a valuable tool in palaeoecological research, although further work is needed to fully assess their performance and usefulness in practice.

Foliar Nutrients Reflect Variation in Floristic Quality and Hydrology of Calcareous Fens

Foliar Nutrients Reflect Variation in Floristic Quality and Hydrology of Calcareous Fens

Conservation and restoration of Central European fens by mowing: A consensus from 20 years of experimental work

While the importance of conservation mowing for mesic grasslands is generally accepted, its use for fens and fen grasslands interspersed within agricultural land is still controversial. Although fens may persist naturally, ongoing environmental changes increase productivity and accelerate succession. These processes can be mitigated through conservation management with appropriate settings. However, long-term management experiments are challenging and provide only locally valid results. Here, we analysed vegetation data (bryophytes and vascular plants) from seven management experiments (spanning 3–20 years) conducted in Central European poor, moderately-rich, and calcareous spring fens (Czech Republic, Slovakia). Two of these experiments examined the effects of restoration of abandoned fens, while five experiments examined changes in mowing regimes in managed fens (cessation, intensification, delay to autumn, and litter removal). Data were analysed using unidimensional and multidimensional methods separately for the initial, extended, and entire period. Mowing had a statistically significant effect on species composition except for the shortest (3-year) experiment. Litter removal did not compensate for mowing. Mowing twice or delayed mowing significantly affected the species composition of calcareous fens. In all cases, cessation of mowing significantly reduced the richness of species, especially those of conservation importance. In contrast, any mowing of abandoned fens increased species richness. The effects of mowing intensification or cessation on species richness and composition of a restored calcareous fen were evident in the first 2–3 years. Other effects were initially weak or nonsignificant but later became stronger, such as mowing delay and restoration removal of litter, which became significant only after nearly 20 years. We found that cessation or restoration of mowing usually triggers a rapid vegetation change, whereas it can take decades to detect the response caused by changes in mowing timing. Importantly, mowing can stabilise or even restore vegetation of fen ecosystems that have been weakened by their fragmentation in the temperate agricultural landscapes.

Holocene history of the landscape at the biogeographical and cultural crossroads between Central and Eastern Europe (Western Podillia, Ukraine)

Continentality is a globally significant gradient influencing broad-scale biogeographical patterns. An excellent example is the transition from the European temperate forest biome to the continental steppe and forest-steppe of Eurasia. One of the biogeographic crossroads where the two biomes meet is the Western Podillia in the western part of Ukraine. It is known for its rich biodiversity with a mixture of steppe, forest and montane species, despite a relatively humid climate suitable for closed-canopy forests. Biologists have postulated the refugial character of the local steppes, but a modern paleoecological reconstruction of the environmental history of the region has been lacking. We fill this gap here with a multi-proxy study (pollen, plant and mollusc macrofossils, microcharcoal, geochemistry) of two profiles sampled in calcareous fens adjacent to species-rich steppe grasslands. To link the reconstructed environmental history with the history of human settlement, we compiled available archaeological records from the studied region. Together, the analyzed profiles cover the entire Holocene and the end of the Last Glacial period, as shown by high-quality age-depth models. All studied proxies support the hypothesis that an open or semi-open landscape existed in Western Podillia during the Holocene. The complete absence of wood remains in Holocene sediments, and the persistence of fen specialists showed the exceptional long-term stability of open wetlands. The continuous presence of pollen of light-demanding plants, low abundance of closed-canopy trees compared to open-canopy trees, and stable concentrations of geochemical indicators of erosion suggest a semi-open landscape with a mosaic of forests, steppe grasslands, and other open habitats. Multivariate analysis revealed the similarity of pollen assemblages with sites in the forest-steppe zone at the interface between the Pannonian Basin and the Western Carpathians. The continuous presence of non-woody microcharcoal in high abundance suggests a role of fire in maintaining open habitats, and the archaeological record provides evidence of human activity throughout the Holocene near the study sites. Comparison with modern pollen spectra suggests that the landscape was probably somewhat more forested in the past than today, but rather by open-canopy trees. Our results indicate that Western Podillia has become a biogeographic crossroads not only because of its location on the border between Central and Eastern Europe, but also because of the unusual combination of relatively humid climate and continuity of open or semi-open landscapes since the Last Glacial.

Long-Term Hydrologic Sustainability of Calcareous Fens along the Glacial Lake Agassiz Beach Ridges, Northwestern Minnesota, USA

Long-Term Hydrologic Sustainability of Calcareous Fens along the Glacial Lake Agassiz Beach Ridges, Northwestern Minnesota, USA

Indicators of regional high capacity well impacts predicts fen floristic quality and composition in Wisconsin calcareous fens

High-capacity wells (HCWs) are known to reduce groundwater discharge to fens and impact their floristic quality, but whether HCW impacts have become predictive of fen floristic quality across large areas has not been studied. Here we used Thiem-equation-estimated drawdown as an indicator of regional HCW impacts to predict floristic quality, floral richness, and community composition in fens throughout their Wisconsin (USA) range. This indicator of HCW influence (HCWinfluence) was associated with a strong decline in floristic quality measures and native-species richness, while non-native-species richness increased sharply. Fuzzy Set Ordination of community data suggested estimated drawdown was associated with the loss of high coefficient-of-conservatism graminoids and forbs, specialist species, and state-listed rare species. The abundance of non-native species and weedy natives increased with increasing HCW impact. The fact that our indicator of HCW influence has become predictive of fen quality and community composition statewide suggests that HCWs are a driver of floristic quality across large areas, and that possible declines in fen quality due to cumulative impacts should be addressed before siting wells.

Persistence and accumulation of environmental DNA from an endangered dragonfly

Detection of environmental DNA (eDNA) has become a commonly used surveillance method for threatened or invasive vertebrates in both aquatic and terrestrial environments. However, most studies in this field favor vertebrate target species. Environmental DNA protocols can be especially useful for endangered invertebrates such as the Hine’s emerald dragonfly (Somatochlora hineana) where conservation efforts have been greatly hindered by training, time, overall costs, and environmental impacts associated with conducting surveys in the calcareous fens occupied by this species. An essential step in developing such a protocol is to evaluate the dynamics of eDNA concentration under controlled conditions. We used the quantitative polymerase chain reaction (qPCR) to examine seasonal shifts in the persistence and net-accumulation of eDNA from captive S. hineana larvae in experimental mesocosms at temperatures corresponding with their overwintering (5.0 °C) and active (16.0 °C) seasons. Environmental DNA persisted longer at 5.0 °C but accumulated more readily at 16.0 °C. Differences in the accumulation and persistence of eDNA reflect differences in the longevity of eDNA at different temperatures and seasonal differences in larval S. hineana behavior. This study highlights the importance of considering how seasonal changes in temperature influence not only the speed of eDNA degradation but also the target species’ eDNA shedding rates.

Predictors of Rare and Specialist Plant Occurrence in Midwestern Calcareous Fens

Predictors of Rare and Specialist Plant Occurrence in Midwestern Calcareous Fens

Vegetation changes associated with release from cattle grazing in a WI calcareous fen

Although grazing was a part of calcareous fens’ disturbance regimes, few studies have examined the impact of grazing release in these systems, and managers are reticent to experiment with restoring grazing for management purposes. Here I describe vegetation, edaphic, and hydrologic differences in a Wisconsin calcareous fen between areas long-protected (since 1987) from cattle grazing and those protected in 2011, 2.5 years before the study. Vegetation surveys found that the long-protected areas had significantly lower floristic quality, fewer rare and specialist species, and more woody-plant encroachment than areas abandoned in 2011. Interviews with a farmer and air-photo interpretations suggested that vegetation changed in the protected areas around the time of abandonment. Known edaphic and hydrologic drivers of vegetation change in fens (volumetric water content, electrical conductivity, nutrient availability) could not account for the vegetation differences between the two areas. Site histories found no events accounting for these vegetation differences other than grazing. These results suggest that grazing release led to increased shrub encroachment, decline in floristic quality, and-possibly- a decline in specialist and rare species.

Characteristics of Liparis loeselii (L.) Rich. populations in selected Natura 2000 areas in eastern Poland

In view of the sensitivity of Liparis loeselii to changes in habitat conditions, we carried out a study with the aim to monitor population numbers, identify the individual features of the Liparis loeselii population, analyse habitat conditions, identify threats and propose conservation measures to preserve the species. The investigations were conducted in seven unmanaged objects located in three Natura 2000 areas in eastern Poland. The results of this study provide a new insight into Liparis loeselii ecology. The analysed populations inhabited some habitat types: extremely poor fen, transitional mire, rich fen, calcareous fen, spring-fed fen. The content of nutrients was similar in all the habitats. A CCA analysis revealed that the total carbon content, pH, and redox potential of the substrate determine differences between the habitats analysed. Juvenile individuals represented a maximum of 12% of the analysed populations and were the least abundant group of these plants. The flowering was primarily influenced by hydrological conditions. Based on the long-term observations reported in this article, it can be assumed that the species stands a chance of surviving at the localities analysed, provided that the habitat conditions do not change dramatically.

Field detection of urease and carbonic anhydrase activity using rapid and economical tests to assess microbially induced carbonate precipitation.

Microbial precipitation of calcium carbonate is a widespread environmental phenomenon that has diverse engineering applications, from building and soil restoration to carbon sequestration. Urease-mediated ureolysis and CO2 (de)hydration by carbonic anhydrase (CA) are known for their potential to precipitate carbonate minerals, yet many environmental microbial community studies rely on marker gene or metagenomic approaches that are unable to determine in situ activity. Here, we developed fast and cost-effective tests for the field detection of urease and CA activity using pH-sensitive strips inside microcentrifuge tubes that change colour in response to the reaction products of urease (NH3 ) and CA (CO2 ). The urease assay proved sensitive and useful in the field to detect in situ activity in biofilms from a saline lake, a series of calcareous fens, and ferrous springs, finding relatively high urease activity in lake samples. Incubations of lake microbes with urea resulted in significantly higher CaCO3 precipitation compared to incubations with a urease inhibitor, showing that the rapid assay indicated an on-site active metabolism potentially mediating carbonate precipitation. The CA assay, however, showed less sensitivity compared to the urease test. While its sensitivity limits its utility, the assay may still be useful as a preliminary indicator given the paucity of other means for detecting CA activity in the field. Field urease, and potentially CA, activity assays complement molecular approaches and facilitate the search for carbonate-precipitating microbes and their in situ activity, which could be applied toward agriculture, engineering and carbon sequestration technologies.

Modern Pollen–Plant Diversity Relationships Inform Palaeoecological Reconstructions of Functional and Phylogenetic Diversity in Calcareous Fens

Predicting the trajectory of ongoing diversity loss requires knowledge of historical development of community assemblages. Long-term data from palaeoecological investigations combined with key biodiversity measures in ecology such as taxonomic richness, functional diversity (FD), phylogenetic diversity (PD) and environmental factors expressed as Ellenberg indicator values (EIVs) could provide that knowledge. We explored the modern pollen–plant (moss polster pollen vs surrounding vegetation) diversity relationships for herbaceous and woody taxa in calcareous fens from two different regions in Estonia, NE Europe. Associations of taxonomic richness, vegetation composition, FD (including functional alpha diversity and trait composition), PD and EIVs in modern pollen vs plant data were studied with correlation analysis, Procrustes analysis and linear regression models. To test their potential use in palaeoreconstructions, diversity measures were applied on pollen data from Kanna spring fen reflecting fen vegetation development over the last nine millennia and diversity changes through time were studied using generalized additive models. Results showed significant pollen–plant richness correlations for herbaceous taxa at vegetation estimate scales up to 6 m radius and Procrustes analysis showed significant compositional associations at all plant estimate scales (up to 100 m). Woody taxa had no significant pollen–plant richness correlations but composition relationships were significant at plant estimate scales of 6–100 m. Traits that were best reflected by pollen data (both in terms of trait composition and functional alpha diversity) among woody and herbaceous taxa were seed number, clonality, SLA and LDMC. PD of herbaceous species was reflected by pollen data. Among the EIVs, Ellenberg L and T were significantly reflected by pollen data for both woody and herbaceous communities. Palaeoreconstruction from Kanna fen indicates that trends of woody taxa are mostly related to long-term changes in climate while diversity variables of herbaceous taxa closely follow autogenic processes within the fen. We suggest that pollen-based diversity estimates should be calculated separately for woody and herbaceous taxa as they clearly represent different spatial scales. Present study suggests that linking sedimentary pollen data with FD, PD and EIVs provides possibilities to examine long-term trends in community assembly and ecosystem processes that would be undetectable from traditional pollen diagrams.