Fen Plants Research Articles

Leaf wax n-alkane distribution and hydrogen isotopic fractionation in fen plant communities of two Mediterranean wetlands (Tenaghi Philippon, Nisí fen—Greece)

Many continental paleoclimate archives originate from wetland sedimentary sequences. While several studies have investigated biomarkers derived from peat-generating vegetation typical of temperate/boreal bogs (e.g., Sphagnum), only scant information is available on emergent plants predominant in temperate/subtropical coastal marshlands, peri-lacustrine and fen environments. Here, we address this gap, focusing on two wetlands in the Mediterranean (Nisí fen and Tenaghi Philippon, Greece). We examined the concentration, homologue distribution, and hydrogen stable isotopic composition (δ2H) of leaf wax n-alkanes in 13 fen plant species, their surrounding soil, and surface water during the wet growing season (spring) and the declining water table period (summer). Our findings indicate that local graminoid species primarily contribute to the soil n-alkane signal, with a lesser influence from forbs, likely owing to differences in morphology and vegetation structure. The δ2H values of surface and soil water align with local average annual precipitation δ2H, reflecting winter-spring precipitation. Consistently, the average δ2H of local surface, soil, and lower stem water showed negligible evaporative enrichment, confirming minimal 2H-fractionation during water uptake. We find that δ2H values of source water for wax compound synthesis in local fen plants accurately mirror local annual precipitation. Furthermore, despite differences between leaves and lower stems in n-alkane production rates, their δ2H values exhibit remarkable similarity, indicating a shared metabolic substrate, likely originating in leaves. Our net 2H-fractionation values (i.e., precipitation to leaf n-alkanes) align with those in Chinese highlands and other similar environments, suggesting consistency across diverse climatic zones. Notably, our data reveal a seasonal decrease in the carbon preference index (CPI) in plant samples, indicating wax lipid synthesis changes associated with increased aridity. Additionally, we introduce a new parity isotopic difference index (PID) based on the consistent δ2H difference between odd and even n-alkane homologues. The PID demonstrates a strong anticorrelation with plant CPI, suggesting a potential avenue to trace long-term aridity shifts through δ2H analysis of odd and even n-alkane homologues in sedimentary archives. While further development of the PID is necessary for broad application, these findings highlight the intricate interplay between plant physiology, environmental parameters, and sedimentary n-alkanes in unravelling past climatic conditions.

Optimal harvest time for high biogas and biomass yield of Typha latifolia, Typha angustifolia and Phalaris arundinacea

Rewetting of peatland is commonly accepted as a useful measure for counteracting climate change. To increase the acceptance, an agricultural use of fen plants is needed. In this study, the optimal harvest date of Typha latifolia, Typha angustifolia and Phalaris arundinacea regarding their biogas potential and biogas yield per hectare was identified. Furthermore, the influence of the chemical composition of Typha spp. and P. arundinacea on the biogas and biochemical methane potential was determined. Finally, the predictability of the biochemical methane potential (BMP) of Typha spp. and P. arundinacea by their composition with published regression models was examined. The three fen plant species were harvested on five different dates in 2018 and/or 2020. For each harvest, the biomass yield, biogas potential and BMP were determined, the chemical composition of the biomass was analyzed, and the biogas yield per hectare was calculated. The biogas potential of T. latifolia, T. angustifolia and P. arundinacea decreased with increasing plant maturity and ranged between 315 and 647 LN kg−1 VS, 405 and 596 LN kg−1 VS and 361 and 597 LN kg−1 VS, respectively. The biogas and BMP of all three plant species investigated were negatively correlated with the lignin content and could be predicted with published regression models, which included the lignin content as main regressor. The derived optimal harvest dates, which were a compromise between biomass yield and biogas potential, for all three fen plants ranged between the development stages of full flowering and shortly after the seed heads turned brown.

A temporal snapshot of ecosystem functionality during the initial stages of reclamation of an upland-fen complex

Study regionAthabasca River Watershed, Athabasca Oil Sands Region (AOSR), Alberta, Canada. Study focusAOSR pre-disturbance landscape consists of a mosaic of upland-peatland complexes, dominated by fens, which have become the focus of recent mandatory reclamation efforts. Quantifiable metrics for evaluating reclamation project trajectories and long-term sustainability are required. Here, the initial performance of a constructed upland-peatland complex (Nikanotee Fen Watershed) is evaluated through a functional-based, ecosystem-scale approach focused on carbon dynamics and water use efficiency (WUE). Initial seven years (2013–2019) post-construction were monitored using eddy covariance and multispectral imagery to capture ecosystem evolution. New hydrological insights for the regionResults indicate the fen quickly evolved from a bare-ground, carbon source (2013) to a sedge-dominated (Carex aquatilis), carbon sink (2015). Slower growth rate of trees (Pinus banksiana, Populus balsamifera) and dry edaphic upland conditions initially resulted in net carbon losses. However, as upland vegetation became established, plant CO2 uptake increased. After 2015, fen WUE remained relatively stable despite fluctuations in seasonal rainfall. Stable WUE reflects a well-connected groundwater network between the two landscape units that supports hydrological self-regulation sufficient to maintain adequate plant function. Because of this groundwater supply, fen plants were no longer dependent solely on precipitation – increasing resilience to intervals of periodic water stress. Overall, carbon and water dynamics during early-development suggests the system is evolving towards a self-sustaining, carbon-accumulating, functional ecosystem.

Rising temperature modulates pH niches of fen species

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

Can nutrient uptake by Carex counteract eutrophication in fen peatlands?

Ground- and surface-water-fed peatlands (i.e., fens) of temperate Europe face high anthropogenic nutrient loads from atmospheric deposition, agricultural catchment areas, and from peat decomposition, if drained. As a result, nitrogen loads may exceed a fen's natural nutrient removal capacity, leading to increased eutrophication of adjacent water bodies. Therefore, it is important to address possible means to decrease a fen's nutrient load, including nutrient uptake by fen plants. To assess how much fen plants can contribute to nutrient removal by uptake, nutrient stocks of above- and below-ground biomass need to be quantified. Therefore, we investigated nitrogen, phosphorous, and potassium uptake capacities of sedges (Carex species), which are common dominants in fen plant communities. We grew specimens of five Carex species with varying preferences in nutrient availability under controlled, different nutrient levels. We show that Carex above-ground biomass harvest can remove up to one third of a system's total nitrogen even at high loads of about 40 g nitrogen m−2. Species-specific differences in biomass production, rather than preferences in nutrient availability under natural conditions, were drivers of standing nutrient stocks: Highly productive species, i.e., C. acutiformis and C. rostrata, had highest nutrient standing stocks across all nutrient levels. Amounts of nutrients stored in shoots increased almost linearly with increasing nutrient levels, whereas below-ground nutrient stocks species-specifically increased, saturated, or decreased, with increasing nutrient levels. As a rough estimate, depending on the species, 6–16 cycles of annual above-ground harvest would suffice to decrease nitrogen concentrations from the highest to the lowest level used in this study. Overall, our results indicate that Carex biomass harvest can be an efficient means to counteract anthropogenic nitrogen eutrophication in fens.

Suitability of paludiculture biomass as biogas substrate − biogas yield and long-term effects on anaerobic digestion

Abstract Fen plants cultivated on wet peatlands might be an environmentally friendly alternative biogas substrate to maize and grass grown on drained peatlands. This study demonstrates that if Typha latifolia, Phragmites australis, and Phalaris arundinacea were harvested in mid-June, then their specific biogas yields (SBY) reached values of up to 581 LN kg−1 volatile solids (VS), which is similar to the SBY of grass, but lower than the SBY, of 670 LN kg−1 VS, for maize. Mixtures with equal or more than 10% T. latifolia or 40% P. arundinacea (VS-base) exhibited a reduced SBY compared to 100% maize silage in a batch-test. From the composition of the substrates, it remains unclear why fen plants degraded that poorly. However, during the semi-continuous long-term experiment, this effect led to an accumulation of non-degraded material, which destabilized the degradation process at loading rates above 3 kg VS m−3 d−1. Destabilization became apparent with substantial increases in the viscosity of the fermenter content, enrichment of acids and a worsened methane formation. Our findings suggest that only small proportions of maize could be replaced by fen plants as substrate for biogas plants.

Establishing vegetation on a constructed fen in a post-mined landscape in Alberta’s oil sands region: A four-year evaluation after species introduction

Oil sands mining in Alberta has disturbed large areas of peatland, the dominant regional ecosystem type, and no formal strategies exist to reconstruct the landscape. Peatland reclamation is challenging, but approaches are now being tested to determine the feasibility of rebuilding these valuable ecosystems. To evaluate our design concept, a pilot reclamation fen and associated watershed was constructed in an oil sands mine near Fort McMurray, Alberta. We implemented a large-scale multifactorial field experiment to test the introduction of bryophytes and vascular plants by moss layer transfer (MLT), seeds, and nursery grown seedlings under wood-strand mulch and with a Typha latifolia removal treatment. Four years after planting, the MLT and Juncus balticus seedling treatment supported the highest bryophyte and vascular plant cover and species richness. Removal reduced T. latifolia cover but was not necessary in areas where seedlings or MLT were introduced as it may have been competitively excluded by the planted species. The most successful fen species to establish was Carex aquatilis that spread quickly but also reduced the cover and species richness of bryophytes and other vascular plants. Water level influenced species distributions, with near surface water tables supporting higher cover of T. latifolia and lower bryophyte and other vascular plant cover and species richness. Our research demonstrates that it is possible to establish and maintain fen bryophytes and vascular plants and limit T. latifolia invasion in a constructed fen. To prioritize fen plant species richness and bryophyte cover, future projects should design for lower water levels, select species tolerant of expected abiotic conditions, and introduce nurse plants such as J. balticus. This research is the first of its kind to evaluate a range of species introduction approaches and demonstrates that it is possible to establish fen plants in the post-mined landscape of Alberta.

Testing the moss layer transfer technique on mineral well pads constructed in peatlands

Peatlands are abundant in the boreal region of Canada but little is known about their restoration on oil sands well pads. The goal of this study is to compare the reintroduction of different peatland plant communities and substrate amendments/decompaction in order to rehabilitate peatland vegetation on former in situ well pads constructed in wetlands. One field experiment tested which peatland plant communities (Shrubby Rich Fen, Treed Rich Fen) would best colonize different substrates (sawdust, clay loam, mix sawdust-clay, peat, surface roughness). We found that the moss layer transfer technique (MLTT) facilitated the establishment of peatland communities on residual mineral soil used to construct the pad, when shaved back to an average water level of the surrounding wetland. The choice of peatland plant community is key to the introduction of bryophytes. Peat amendment facilitated the establishment of plants, whereas soil decompaction had no effect. The MLTT is a promising approach to restore fen plants on well pads. We recommend a scale-up experiment for a whole well site to test the validity of MLTT along different pad removal techniques.

Reintroduction of fen plant communities on a degraded minerotrophic peatland

We have developed an approach to restore bogs after peat extraction, but, when sedge-peat layers are exposed, the minerotrophic remnant peat conditions require restoration towards a fen ecosystem. Three restoration techniques, all including rewetting actions, were tested to assist fen vegetation recovery. None of the restoration techniques were effective at establishing fen bryophytes. However, for vascular plants, two techniques gave promising results in terms of species composition, although the vascular plant cover remained lower than in the reference fens. Depending on the site conditions, we suggest applying two restoration techniques to restore peatlands in areas of exposed sedge peat. In areas where sparse cover of fen species may have spontaneously established, rewetting should be carried out to raise water levels and create favourable conditions for their expansion. In areas covered with undesirable species or with inadequate topography for rewetting, surface peat should be remodeled and vegetation introduced. Since mechanized diaspore transfer did not result in a satisfactory cover of fen plants, other means of introduction could be considered, alone or in combination. A complementary fertilization experiment showed that fertilization with phosphorus could be an effective solution to enhance the establishment of mechanically introduced plant diaspores.

Plant macrofossil and biomarker evidence of fen–bog transition and associated changes in vegetation in two Finnish peatlands

Past vegetation assemblages, preserved in peat layers, are one of the key proxies when reconstructing historical peatland dynamics. Northern peatlands can be divided into two main types: fens and bogs. Compared with bog peat, the fen peat is usually more decomposed because of different eco-hydrological conditions and effective humification processes. A high level of decomposition hampers reliable identification of plant remains and constrains palaeoecological approaches. Biogeochemical studies on bog plants and bog peat have shown that plant group–specific biomarkers can be applied to identify fossil plants or plant groups from peat, given the identification of plant group–specific markers in living fen plants. In this study, we applied plant macrofossil, biomarkers and multivariate statistical analyses to two mid-boreal peat sequences to investigate whether biomarkers can be applied to distinguish fen and bog environments and whether plant-specific biomarkers can be identified from fen peat. Macrofossil analyses clearly separate dry bog hummocks, moist lawns and wet fen habitats apart. Corresponding division emerged when the biomarker data were combined with the macrofossil data. Moreover, we succeeded to separate bog and fen habitats apart by the changes in n-alkane and the n-alkane ratio distributions along the cores. The fen–bog transition zone was indicated by high sterol and triterpenoid concentrations and changes in degradation measures. However, it remains a challenging task to attain species-level information of past plant assemblages from highly humified fen peat layers based on biomarkers only.

Hydro-ecology of groundwater-dependent ecosystems: applying basic science to groundwater management

Effective policies to protect groundwater-dependent ecosystems require robust methods to determine the environmental flows and levels required to support species and processes. Frameworks to support groundwater management must incorporate the relationships between hydrology and species and ecological processes. These hydro-ecological relationships can be used to develop quantitative, measurable thresholds that are sensitive to changes in groundwater quantity. Here we provide a case study from a group of fens in central Oregon, USA, that are used for cattle watering, but also support numerous sensitive species. We developed quantitative relationships between the position of the water table and wetland indicator plant species and the process of peat development, to propose groundwater withdrawal thresholds. A maximum depth to water table of –0.9 to –34.8 cm for fen plants and –16.6 to –32.2 cm for peat accretion can be tolerated in these wetlands. Defining hydro-ecological relationships as thresholds can support management decisions.Editor D. Koutsoyiannis; Guest editor M. AcremanCitation Aldous, A.R. and Bach, L.B., 2014. Hydro-ecology of groundwater-dependent ecosystems: applying basic science to groundwater management. Hydrological Sciences Journal, 59 (3–4), 530–544.

Biogeochemical sequestration of carbon within phytoliths of wetland plants: A case study of Xixi wetland, China

As an important long-term terrestrial carbon sequestration mechanism, biogeochemical sequestration of carbon within phytoliths may play a significant role in the global carbon cycle and climate change. The aim of this study is to explore the potential of carbon bio-sequestration within phytoliths produced by wetland plants. The results show that the occluded carbon content of phytoliths in wetland plants ranges from 0.49% to 3.97%, with a CV (coefficient of variation) value of 810%. The data also indicate that the phytolith-occluded carbon (PhytOC) content of biomass for wetland plants depends not only on the phytolith content of biomass, but also the efficiency of carbon occlusion within phytoliths during plant growth in herb-dominated fens. The fluxes of carbon bio-sequestration within phytoliths of herb-dominated fen plants range from 0.003 to 0.077 t CO2 equivalents t-e-CO2 ha−1 a−1. In China, 0.04×106 to 1.05×106 t CO2 equivalents per year may be sequestrated in phytoliths of herbaceous-dominated fen plants. Globally, taking a fen area of 1.48×108 ha and the largest phytolith carbon biosequestration flux (0.077 t-e-CO2 ha−1 a−1) for herb-dominated fen plants, about 1.14×107 t CO2 equivalents per year would have been sequestrated in phytoliths of fen plants. If other wetland plants have similar PhytOC production flux with herb-dominated fen plants (0.077 t-e-CO2 ha−1 a−1), about 4.39×107 t-e-CO2 a−1 may be sequestrated in the phytoliths of world wetland plants. The data indicate that the management of wetland ecosystems (e.g. selection of plant species) to maximize the production of PhytOC have the potential to bio-sequestrate considerable quantities of atmospheric CO2.

The n-alkane and sterol composition of living fen plants as a potential tool for palaeoecological studies

In groundwater-fed fen peatlands, the surface biomass decays rapidly and, as a result, highly humified peat is formed. A high degree of humification constrains palaeoecological studies because reliable identification of plant remains is hampered. Organic geochemistry techniques as a means of identifying historical plant communities have been successfully applied to bog peat. The method has also been applied to fen peat, but without reference to the composition of fen plants. We have applied selected organic geochemistry methods to determine the composition of the neutral lipid fractions from 12 living fen plants, to investigate the potential for the distributions to characterize and separate different fen plants and plant groups. Our results show correspondence with previous studies, e.g. C23 and C25n-alkanes dominating Sphagnum spp. and C27 to C31 alkanes dominating vascular plants. However, we also found similarities in n-alkane distributions between Sphagnum spp. and the below ground parts of some vascular plants. We tested the efficiency of different n-alkane ratios to separate species and plant groups. The ratios used for bog studies (e.g. n-C23/n-C25 and n-C23/n-C29) did not work as consistently for fen plants. Some differences in sterol distribution were found between vascular plants and mosses; in general vascular plants had a higher concentration of sterols. When distributions of n-alkanes, n-alkane ratios and sterols were all included as variables, redundancy analysis (RDA) separated different plant groups into their own clusters. Our results imply that the pattern for bog biomarkers cannot directly be applied to fen environments. Nevertheless, they encourage further testing to determine whether or not the identification of plant groups, plants or plant parts from highly humified peat is possible by applying fen species-specific biomarker proxies.

Impacts of oil sands process water on fen plants: Implications for plant selection in required reclamation projects

Fen plant growth in peat contaminated with groundwater discharges of oil sands process water (OSPW) was assessed in a greenhouse over two growing seasons. Three treatments (non-diluted OSPW, diluted OSPW and rainwater) were tested on five vascular plants and four mosses. All vascular plants tested can grow in salinity and naphthenic acids levels currently produced by oil sands activity in northwestern Canada. No stress sign was observed after both seasons. Because of plant characteristics, Carex species (C. atherodes and C. utriculata) and Triglochin maritima would be more useful for rapidly restoring vegetation and creating a new peat-accumulating system. Groundwater discharge of OSPW proved detrimental to mosses under dry conditions and ensuring adequate water levels would be crucial in fen creation following oil sands exploitation. Campylium stellatum would be the best choice to grow in contaminated areas and Bryum pseudotriquetrum might be interesting as it has spontaneously regenerated in all treatments.

Effects of Light Intensity and Groundwater Level on the Growth of a Globally Rare Fen Plant

Fens are wetlands of conservation concern across temperate regions of the world. Understanding how abiotic factors affect typical fen plants will help to direct conservation efforts in these wetlands. Here, I examine how light and groundwater levels affect the growth of the globally rare fen plant Trollius laxus. Stem and biomass production were compared among plants grown at combinations of two groundwater levels (10 and 20 cm below the surface) and four light levels (6, 40, 77, and 90% photosynthetic photon flux density) in the greenhouse. Light intensity and groundwater level interactively affected T. laxus growth, with the highest plant performance at high light intensity and low groundwater level. Plants showed no response to differences in groundwater level when highly shaded, but as light intensity increased, stem and biomass production increased more quickly at the lower than at the higher groundwater level. Increased light caused greater biomass allocation to roots versus shoots, but groundwater level did not influence allocation patterns. That T. laxus is physiologically tolerant of higher light and lower groundwater levels suggests that it, like other typical fen plants, may be excluded from drier, more optimal wetlands or parts of wetlands by plants that are stronger competitors for light.

Influence of fire on a rare serpentine plant assemblage: A 5‐year study of Darlingtonia fens

Serpentine soils have attracted the attention of evolutionary biologists for decades because of their high number of rare and endemic taxa, though less is known about the ecological factors that govern the diversity and composition of serpentine communities. Theory suggests that vegetation on these low-productivity soils will be relatively resilient to fire, the most common natural disturbance in serpentine systems. We studied the recovery of vegetation in Darlingtonia fens, a unique habitat dominated by herbaceous perennials, from a major fire that burned ∼202,000 ha in California and Oregon's Klamath Mountains in 2002. We established permanent plots in eight unburned and eight burned fens in 2003 and recorded percent cover of vascular plant species. We re-sampled plots each year through 2007. Burned fens had less plant cover than unburned fens for 2 yr after the fire. Average species density was ∼10% lower in burned fens 1 yr after the fire but ∼4-8% higher for the next 4 yr. Burned fens exhibited greater evenness but not until 4 yr after the fire. Differences in community composition were detected between the two fen types, but species ranks were similar, and species neither were added to nor removed from the burned assemblages. Burning of Darlingtonia fens has detectable, albeit modest, effects on serpentine communities. Because fens have little or no canopy cover, fire has little influence on light availability in this system. This relatively small resource change, combined with high soil moisture and well-developed underground organs of fen plants, produces a highly resilient assemblage.

Assessment of flora, plant communities, and hydrochemical conditions for adaptive management of a small artificial wetland made in a park of a cool-temperate city

In order to recreate the landscape of Ishikari Mire, an artificial wetland was made in 2000 at a city park in northern Japan. Its flora, plant communities, and hydrochemical conditions were examined in 2005 and compared with those determined in 2001 and with those of nearby intact fens. Management increased water levels by ca. 10 cm from 2002. Neutral pH, high electrical conductivity (EC), and high concentrations of nitrogen and mineral ions were the same as in 2001, but higher than in fens. The wetland was flooded by river water a few times every year. These hydrochemical conditions suit the growth of fen species. Total species increased from 73 (2001) to 105 (2005), whereas annuals and biennials decreased from 20 to 13 and naturalized exotic species from 18 to 15. Five naturalized exotic species that disappeared by 2005 were all mesophytes, and one of two newly found naturalized exotic species was a hygrophyte. Accordingly, the rapid change can be explained by the change of lifeforms in the early stage of secondary succession, and in some parts, by the disappearance of mesophytic plants as wetness increased. During the 6 years, the wetland communities changed toward that of fens because most of the migrated or imported fen species were increasing. Many other fen plants, therefore, would be able to grow in the wetland, while only four fen species had migrated. Accordingly, importation of other fen plants is essential to recreate the whole plant assemblages of mire.

Throughflow as a determining factor for habitat contiguity in a near-natural fen

Knowledge of the hydrological mechanisms that underlie stable plant communities within natural fens is essential for the improvement of current fen restoration and conservation strategies. In this study, steady-state groundwater modelling was performed to quantify the impact of throughflow mechanisms on the presence of exfiltrated, alkaline groundwater across a near-natural fen in the Biebrza River catchment (Poland). Alkaline groundwater is considered essential for the existence of low-productive fen plants. The results indicate that throughflow redistributes exfiltrated groundwater, mixed with locally infiltrated precipitation, in various concentrations across the fen. The throughflow model provides an explanation for the major patterns in the plant alliances that have a preference for minerotrophic or ombrotrophic habitat conditions. These patterns could not be reproduced with groundwater models that did not account for the existence of throughflow on a regional scale. We conclude that throughflow (1) enables a spatially contiguous supply of exfiltrated groundwater across fens, and thereby (2) facilitates abiotic conditions suitable for fen plants outside the zones that are directly supplied by exfiltrated groundwater. These new insights into landscape hydrological mechanisms that drive abiotic conditions within natural fens necessitate the reprioritisation of current hydrological fen restoration strategies. © 2009 Elsevier B.V. All rights reserved.

The dynamic form of rainwater lenses in drained fens

Inflow of nutrient poor alkaline groundwater is generally seen as a prerequisite for the development of species rich fen vegetation. Drainage and groundwater abstraction may lead to the development of so-called rainwater lenses in the upper groundwater of fens, which prevent upward seeping alkaline groundwater from reaching the fen root zone. This threatens the conservation of the species rich vegetation. To provide insight in rainwater lens dynamics as a basis for conservation and restoration of fen biodiversity, numerical groundwater flow model simulations were performed for a hypothetical case area in the Netherlands. The simulations indicate that drainage canal surface water levels mainly affect the phreatic level in the fens, while groundwater inflow fluxes mainly affect the thickness of the rainwater lens. Increasing thickness of a semi-confining surface layer results in a rise in phreatic level. As the phreatic level reaches the soil surface, the rainwater lens may split in two as a result of groundwater discharge windows, which come into existence in the centre of the parcel. The effect of seasonal recharge fluctuations on the rainwater lens appears small. Spells of dry and wet years have a considerably larger effect especially on the lower boundary of the rainwater lens, resulting in thinner lenses during spells of dry years. Most simulations show rainwater lens thicknesses well exceeding rooting depths of fen plants. This is inconsistent with the fact that fen vegetation is found in nature reserves for which the simulations are considered representative. Chemical buffer processes in the soil may explain this inconsistency, masking an acidification process under way. As buffer capacities become exhausted over time, acidification and fen deterioration will occur at a certain future moment. To arrive at more definite conclusions about this hypothesis, our simulations of convective groundwater flow need to be supplemented by modelling of hydrochemical processes in rainwater lenses, followed by verification at actual field locations.

Patterns of distribution of microfungi in decomposing bog and fen plants

The microfungal assemblages from the litter of the dominant vegetation of a forested bog and a riverine, sedge-dominated fen in southern boreal Alberta, Canada, were investigated over a 2-year period. Canonical correspondence analyses showed distinctly different fungal communities associated with litter of the dominant plant species of this bog (Sphagnum fuscum (Schimp.) Klinggr.) and fen (Carex aquatilis Wahlenb. leaves and rhizomes and Salix planifolia Pursh leaves and roots). Plant tissue quality variables, including total phosphorus and total nitrogen tissue concentrations, correlated most strongly with the fungal communities. In contrast, site-specific environmental (surface water chemical variables) and physical (peat and water temperatures, water level) variables were not correlated with the fungal communities of these five decomposing fen and bog plant litters. Of 93 identified fungal taxa, 25% occurred exclusively in the bog and 56% occurred exclusively in the fen. Eighteen species (19%) were common to the materials examined from both peatlands. Several species of (i) Aspergillus, Mortierella, and Oidiodendron were restricted to the Sphagnum litter in the bog, and species of (ii) Phialophora, Phialocephala, Fusarium, Dimorphospora foliicola, Monocillium constrictum, and several basidiomycetes were restricted to the Carex and Salix plant litters in the fen. These taxa constitute components of the bog and fen fungal communities, respectively.Key words: fungal communities, decomposition, bog, fen, canonical correspondence analysis (CCA).