Effectiveness of Turf Stripping as a Measure for Restoring Species-Rich Fen Meadows in Suboptimal Hydrological Conditions

Most species‐rich fen meadows in nature reserves in The Netherlands are acidified due to weaker upwelling of base‐rich groundwater. The present study investigated whether and why turf stripping combined with superficial drainage might promote the long‐term recovery of such meadows and restore the nutrient‐poor, buffered conditions they require. In a field experiment, we analyzed changes in vegetation composition, soil parameters, and soil water chemistry in stripped plots of degraded Cirsio‐Molinietum vegetation over 12 years. After the first five years, many species from the target communities occurred in stripped plots. Both vegetation and soil data showed positive effects of turf stripping on the acid‐buffering capacity. Because sulfate concentration in the soil water decreased over time, whereas the bicarbonate concentration increased, we inferred that there was internal alkalinization driven by sulfate reduction in low‐lying stripped plots. However, the succession toward more acidophilus plant communities, in both control and stripped plots, indicated gradual acidification. This may be caused by a continuing weakening of the upward seepage of base‐rich groundwater as shown by declining calcium concentrations in the soil water. Though turf stripping exposed a nutrient‐poor soil layer with a greater acid‐buffering capacity, these positive effects might not be sufficient to combat the ongoing acidification in the long term.     

Higher acidification rates in fens with phosphorus enrichment

Question: Why is bryophyte succession in eutrophicated fens faster than in natural fens? Location: Mineral‐rich fens in The Netherlands and NW Europe. Methods: Literature review on the ecology of four bryophyte species in various successional types as observed in Dutch fens. Results: Bryophyte succession in eutrophicated fens from the brown moss Calliergonella cuspidata to Sphagnum squarrosum is much faster than in natural fens with species shifts from Scorpidium scorpioides to Sphagnum subnitens. Under P‐poor conditions, the brown moss stage is stabilized as long as mineral‐rich water is supplied. This is because S. scorpioides is tolerant of rainwater, is a strong competitor and can counteract acidification to some extent while S. subnitens is intolerant to groundwater and has low growth rates and low acidification capacity. In contrast, the Sphagnum stage is stable after rapid succession from rich‐fen mosses under P‐rich conditions. Calliergonella cuspidata has suboptimal growth in rainwater, possibly due to ammonium toxicity, while the high growth rates of S. squarrosum in nutrient‐rich and highly acidic groundwater allow early establishment and rapid expansion. Conclusions: If measures to improve fen base status occur in environments of increased nutrient (P) availability, the management may not lead to the desired restoration of brown moss stages, but instead to rapid acidification by S. squarrosum.     

Nutrient supply in undrained and drained Calthion meadows

Abstract. Plant species-rich Calthion meadows on mesotrophic fen peat soil extensively cut for hay are among the endangered semi-natural vegetation types in northwestern Europe. They are often badly affected by lowering the groundwater table (drainage) and fertilization. In a comparative study of an undrained site with a Calthion meadow and an adjacent drained site, availability of N, P and K was biologically assessed under field conditions (for two years) as well as in a greenhouse (for 18 weeks) by measuring shoot responsiveness. Also, experimental wetting of intact turf samples taken from both sites was applied in order to study the interaction between nutrient supply and anaerobic soil conditions. It was concluded that the above-ground phytomass yield in the undrained site was restricted by a major shortage of N-supply and a moderate shortage of K-supply by the fen peat soil. The above-ground phytomass yield of the drained site was only reduced by a strongly limited supply of K by the soil. The extent of K-deficiency was larger for the drained site. No P-deficiency was observed in any of the drained or undrained sites. Rewetting turf samples, taken from the drained site, did not change above-ground phytomass yields, suggesting that nutrient supplies were not affected by rewetting. Leaching has likely resulted in a strong reduction of K-supply in the drained site. It is assumed that a shortage in K-supply from the peat soil may have become an important environmental constraint for characteristic plant species of Calthion meadows. This may hamper the development of this meadow type on drained peat soils after rewetting by groundwater discharge.     

Long‐term effects of drainage and initial effects of hydrological restoration on rich fen vegetation

Questions: What vegetational changes does a boreal rich fen (alkaline fen) undergo during a time period of 24 years after drainage? How is plant species richness affected, and what are the changes in composition of ecological groups of species? Is it possible to recover parts of the original flora by rewetting the rich fen? Which are the initial vegetation changes in the flora after rewetting? What are the major challenges for restoration of rich fen flora after rewetting? Location: Eastern central Sweden, southern boreal vegetational zone. Previously rich fen site, drained for forestry purposes during 1978–1979. The site was hydrologically restored (rewetted) in 2002. Method: Annual vegetation survey in permanent plots during a period of 28 years. Results: There were three successional stages in the vegetational changes. In the first stage there was a rapid (< 5 years) loss of rich fen bryophytes. The second step was an increase of sedges and early successional bryophytes, which was followed by an increase of a few emerging dominants, such as Molinia caerulea, Betula pubescens and Sphagnum spp. After rewetting, there are indications of vegetation recovery, albeit at slow rates. Depending on, for instance, initial species composition different routes of vegetation change were observed in the flora after drainage, although after 24 years, species composition became more homogenous and dominated by a few species with high cover. Conclusion: Major changes have occurred after changes in the hydrology (drainage and rewetting) with a severe impact on the biodiversity among vascular plants and bryophytes. Several rich fen bryophytes respond quickly to the changes in water level (in contrast to vascular plants). The recovery after rewetting towards the original rich fen vegetation is slow, as delayed by substrate degradation, dispersal limitation and presence of dominant species.     

Nutrient limitation in boreal plant communities and species influenced by scything

Abstract. The nutrient status was studied in permanent plots of four plant communities, two rich-fen communities and two wooded grassland communities, all formerly used for haymaking. The concentrations of N, P and K in plant material of dominant and subdominant species (above- and below-ground) were measured in plots experimentally scythed annually or biennially for two decades, and in plots unscythed for four decades. Three of the communities had an N:P ratio of 14 or less, indicating N-limitation; the most fertile grassland community had particularly low values for the N:P ratio (6–12), as did a majority of the species, including all tall-herb species. A species-rich community of fen-margin vegetation in the lowest productive rich fen, had an N: P ratio of 17–19 in the above-ground biomass, which indicates P-limitation of nutrients. Molinia caerulea and Thalictrum alpinum were found to be the vascular plants with the highest N:P ratio, indicating P-limitation of nutrients. Calculations of N:K and K:P ratios indicated possible K-limitation in the rich-fen communities, especially for Thalictrum alpinum, the species with the highest N:K value. No expected change from N- to P-limited growth was found; in contrast, a reduction in the N:P ratio was found in the annually scythed plots of the rich fens, suggesting that reduced biomass production is mainly a result of disturbance by scything. As expected, a reduction in the concentration of K was detected in the scythed plots.     

Hydrology of Dutch Cirsio‐Molinietum meadows: Prospects for restoration

Abstract. Fen meadows (Cirsio dissecti‐Molinietum) are seriously threatened by desiccation, acidification and eutro‐phication. In The Netherlands several projects were launched to restore damaged fen meadows. This review describes how successes and failures of these restoration projects depend on hydrological systems. Six hydrological systems have been distinguished, which all provide the site conditions required by this community. Nowadays, the best developed fen meadows are found in the higher Pleistocene landscape of The Netherlands, where they depend on base‐rich groundwater discharging from local or large groundwater systems. Fen meadows of the lower Holocene landscape usually occur in man‐made surface water systems. Almost all stands have been severely deteriorated. Restoration of fen meadows in the Pleistocene landscape is promising when the hydrology is only slightly disturbed or when hydrological measures are taken in combination with sod cutting. Restoration prospects of fen meadows in the Holocene landscape are low. Until now a complete regeneration of Cirsio‐Molinietum meadows has not been realized. Restoration measures failed to restore high pH values in the top soil. It is hypothesized that viable seeds of many target species lack in the soil seed bank. In addition, the dispersal capacities of these species seem to be limited.     

Shrub encroachment in the Alps gives rise to the convergence of sub‐alpine communities on a regional scale

Question: How does Alnus alnobetula colonization affect plant communities in sub‐alpine grasslands undergoing land abandonment on a regional scale? Location: Savoie, French Alps. Methods: Variations within and between communities were monitored in 243 plots within three types of stands representing an A. alnobetula colonization chronosequence from grassland to dense vegetation. They were tested for species richness, species strategies and species distribution through multivariate analysis. Regional variations were assessed at three sites along a rain shadow gradient. Results: We detected a convergence of the understorey communities along an A. alnobetula colonization gradient at all sites, associated with a reduction in species richness and the replacement of stress related strategists by competitor strategists. This convergence was unaffected by the rain shadow gradient although it was a key factor of plant distribution. Conclusions: The dense cover and the soil properties provided by A. alnobetula stands buffered the heterogeneity of sub‐alpine communities induced by a rain shadow gradient throughout the study region. It facilitated the development a homogeneous understorey community dominated by competitor related strategists while excluding grasslands stress adapted species through competition processes. The resulting community, although species‐poor, has an interesting conservation value. Accordingly, as a ‘native invader’, A. alnobetula does not display typical traits of biological invaders. Future experimental research on the interactions between A. alnobetula and components of the understorey would be particularly interesting in a severe environment that promotes facilitation among plants.     

Recent changes in the plant composition of wetlands in the Jura Mountains

Aim

To assess vegetation changes in montane fens and wet meadows and their causes over 38 years.

Location

Wetlands, Jura Mountains (Switzerland and France).

Methods

Plots were inventoried in 1974 and re‐located in 2012 (quasi‐permanent plots) on the basis of sketches to assess changes in plant communities. The 110 plots belonged to five phytosociological alliances, two in oligotrophic fens (Caricion davallianae, Caricion fuscae) and three in wet meadows (Calthion, Molinion, Filipendulion). Changes between surveys were assessed with NMDS, and changes in species richness, Simpson diversity, species cover and frequency and the causes of these changes were evaluated by comparing ecological indicator values.

Results

Changes in species composition varied between alliances, with a general trend towards more nutrient‐rich flora with less light at ground level. Species diversity declined, with a marked decreasing trend for the typical species of each alliance. These species were partly replaced by species belonging to nitrophilous and mesophilous grasslands. However, no trend towards drier conditions was detected in these wetlands. The largest changes, with an important colonization by nitrophilous species, occurred in the Swiss sites, where grazing was banned 25 years ago. As a result of floral shifts, many plots previously belonging to fens or wet mesotrophic meadows shifted to an alliance of the wet meadows, generally Filipendulion. Moreover, communities showed a slight trend towards more thermophilous flora.

Conclusions

The investigated wetlands in the Jura Mountains have suffered mainly from eutrophication due to land‐use abandonment and N deposition, with a loss of typical species. Areas with constant land use (grazing or mowing) showed less marked changes in species composition. The most important action to conserve these wetlands is to maintain or reintroduce the traditional practices of extensive mowing and livestock grazing in the wetlands, especially in areas where they were abandoned 25 years ago. This previous land‐use change was intended to improve fen conservation, but it was obviously the wrong measure for conservation purposes.     

Changes in soil and vegetation during dune slack succession

Many rare plant species occur in Dutch wet dune slacks, particularly in the Junco baltici‐Schoenetum nigricantis. For nature management it is important to understand the processes controlling the presence of these basiphilous early successional communities, which is why we investigated vegetation and soil development during succession in coastal dune slacks. We compared 12 chronosequential stages of 0, 2, 4, 9, 10, 13, 25, 30, 43, 60, 70 and 85 yr in five different dune slack systems. In four of these locations turf had earlier been removed in order to restore the basiphilous pioneer stage. The main variation in the vegetation is related to the acidification/soil enrichment gradient and the salinity/maritime gradient. During succession, organic matter accumulates and acidification takes place. Maritime influence can buffer the soil and postpone the succession of basiphilous pioneer communities for many years. A significant correlation with age was found for 18 variables. Multiple regressions predicted changes in the vegetation (dependent variables: biomass, cover of Salix repens, Calamagrostis epigejos and Schoenus nigricans) as a function of acidification, organic matter accumulation, increase in available P and presence of Na in the soil. We conclude that natural ageing of the vegetation and the associated process of accumulation of biomass drive succession in this hydrosere. The underlying soil processes are acidification and organic matter accumulation. During succession dominance shifts from S. nigricans to S. repens or C. epigejos. Maintenance of the pioneer character of the habitat is only possible by local intervention or by natural or man‐induced dune forming. The effect of sod‐stripping depends on the environmental conditions and, in case of acidification, success is limited. Succession can be postponed by mowing.     

Species trait shifts in vegetation and soil seed bank during fen degradation

Fens in Central Europe are characterised by waterlogged organic substrate and low productivity. Human-induced changes due to drainage and mowing lead to changes in plant species composition from natural fen communities to fen meadows and later to over-drained, degraded meadows. Moderate drainage leads to increased vegetation productivity, and severe drainage results in frequent soil disturbances and less plant growth. In the present article, we analyse changes in plant trait combinations in the vegetation and the soil seed bank as well as changes in the seed bank types along gradient of drainage intensity. We hypothesize that an increase in productivity enhances traits related to persistence and that frequent disturbance selects for regeneration traits. We use multivariate statistics to analyse data from three disturbance levels: undisturbed fen, slightly drained fen meadow and severely drained degraded meadow. We found that the abundance of plants regenerating from seeds and accumulating persistent seed banks was increasing with degradation level, while plants reproducing vegetatively were gradually eliminated along the same trajectory. Plants with strong resprouting abilities increased during degradation. We also found that shifts in trait combinations were similar in the aboveground vegetation and in soil seed banks. We found that the density of short-term persistent seeds in the soil is highest in fen meadows and the density of long-term persistent seeds is highest in degraded meadows. The increase in abundance of species with strong regeneration traits at the cost of species with persistence-related traits has negative consequences for the restoration prospects of severely degraded sites.     

Classification of peatland vegetation in Atlantic Canada

Abstract. The peatlands of Atlantic Canada are classified in four plant alliances, consisting of 10 plant associations. The four plant alliances comprise the dry bog communities (Kalmio-Cladonion Wells 1981), wet bog communities (Scirpo-Sphagnion Wells 1981), hummock and ridge communities of slope and string fens (Betulo-Sphagnion Wells all. nov.), and poor, intermediate and rich fen plant communities (Scirpo-Myricion Wells 1981). Distribution maps are presented for relevés in each of the 10 associations. Based on species distributions, floristic regions are defined for peatlands in Atlantic Canada. Nutritional characteristics are also described for each plant association. pH and total soil concentrations of calcium, nitrogen and iron proved reliable in separating bog from fen. A boundary between ombrotrophic peatlands and minerotrophic peatlands is suggested, based on a soil pH of 4.0, total soil concentrations of 3.0 mg g^?1 Ca, 4.0 mg g^?1 Fe, 13.0 mg g^?1 N and a Ca/Mg ratio of 2.5. Comparisons between the syntaxa for peatlands in Atlantic Canada and those in Europe are discussed for higher taxa. The possibility of establishing a new order (Chamaedaphno-Scirpetalia Wells ord. nov.) for peatlands in Atlantic Canada is also discussed.     

The effects of drainage on groundwater quality and plant species distribution in stream valley meadows

Conditions in fen meadows in Dutch stream valleys are influenced by both deep (Ca²⁺-rich) and shallow (Ca²⁺-poor) groundwater flows. The distribution patterns of phreatophytic (groundwater-influenced) plant species showed distinct relationships with the distribution of different groundwater types. Large fluctuations in the ionic composition of groundwater were observed in the upper peat layers of drained areas. Ca²⁺-rich groundwater was replaced by precipitation water to a considerable depth (1–1.5 m). These fluctuations in groundwater composition were less pronounced in undrained areas.It was observed that characteristic species of fen meadow communities and rare phreatophytic species were restricted to areas with high water tables, which were nourished by either Ca²⁺-poor or by Ca²⁺-rich groundwater. Few species showed a preference for drained areas, where replacement of groundwater types gave rise to the occurrence of an intermediate groundwater type, which was thought to be the result of an increased acidification of the top soil (increased influence of infiltration water).It was argued that the endangered species were best preserved in areas with an undisturbed discharge of natural groundwater flows.Abbreviations EC = Electrical conductivity     

Hydro-ecological analysis of the Biebrza mire (Poland)

Vegetation composition and structure of 58 sites along gradients in the valley mire of Biebrza, Poland, are related to physical and chemical variables of groundwater and peat. The three most prominent hydrochemical processes in the valley are (a) dissolution of calcite; (b) dissolution of iron, manganese and aluminium; and (c) enrichment with nitrogen and potassium. Major factors determining these processes are vertical flow of the groundwater and river flooding.Within the rheophilous zone of the mire, calcium-richness of the shallow groundwater and base-saturation of the peat are caused by upward seepage of groundwater originating from adjacent higher grounds. This groundwater movement keeps the larger part of the mire saturated with calcium.Good correlations exist between hydrochemistry and vegetation patterns. Groundwater-fed sites support a characteristic rich fen vegetation (Caricetum limoso-diandrae) with a low biomass production. The flood-plain vegetation consists of highly-productive communities of Glycerietum maximae and Caricetum elatae. In a belt in the Upper Basin where neither flooding nor upward seepage occurs, succession, probably caused by intensified drainage, leads to a dwarf-shrub vegetation (Betuletum humilis; poor fen).     

Effects of stream flooding on the distribution and diversity of groundwater‐dependent vegetation in riparian areas

1. Effects of the frequency and duration of flooding on the structural and functional characteristics of riparian vegetation were studied at four sites (n = 80, 50 × 50 cm, plots) along medium‐sized naturally meandering lowland streams. Special focus was on rich fens, which – due to their high species richness – are of high priority in nature conservation. 2. Reed beds, rich fens and meadows were all regularly flooded during the 20‐year study period, with a higher frequency in reed bed areas than in rich fen and meadow areas. In rich fens, species richness was higher in low frequency flooded areas (≤3 year^?1) than in areas with a high frequency of flooding (>3 year^?1) or no flooding, whereas species richness in reed beds and meadows was unaffected by flood frequency. 3. The percentage of stress‐tolerant species was higher in low intensity flooded rich fen areas than in high intensity and non‐flooded areas, indicating that the higher species richness in low frequency flooded rich fens was caused by competitive release. We found no indication that increased productivity was associated with high flooding frequencies. 4. We conclude that the restoration of morphological features in stream channels to increase the flooding regime can be beneficial for protected vegetation within riparian areas, but also that groundwater discharge thresholds and critical levels for protected vegetation should be identified and considered when introducing stream ecosystem restoration plans.     

Vegetation heterogeneity and ditches create spatial variability in methane fluxes from peatlands drained for forestry

Drainage of peatlands for forestry starts a succession of ground vegetation in which mire species are gradually replaced by forest species. Some mire plant communities vanish quickly following the water-level drawdown; some may prevail longer in the moister patches of peatland. Drainage ditches, as a new kind of surface, introduce another component of spatial variation in drained peatlands. These variations were hypothesized to affect methane (CH₄) fluxes from drained peatlands. Methane fluxes from different plant communities and unvegetated surfaces, including ditches, were measured at the drained part of Lakkasuo mire, Central Finland. The fluxes were found to be related to peatland site type, plant community, water-table position and soil temperature. At nutrient-rich fen sites fluxes between plant communities differed only a little: almost all plots acted as CH₄ sinks (−0.9 to −0.4 mg CH₄ m⁻² d⁻¹), with the exception of Eriophorum angustifolium Honck. communities, which emitted 0.9 g CH₄ m⁻² d⁻¹. At nutrient-poor bog site the differences between plant communities were clearer. The highest emissions were measured from Eriophorum vaginatum L. communities (29.7 mg CH₄ m⁻² d⁻¹), with a decreasing trend to Sphagna (10.0 mg CH₄ m⁻² d⁻¹) and forest moss communities (2.6 mg CH₄ m⁻² d⁻¹). CH₄ emissions from different kinds of ditches were highly variable, and extremely high emissions (summertime averages 182–600 mg CH₄ m⁻² d⁻¹) were measured from continuously water-covered ditches at the drained fen. Variability in the emissions was caused by differences in the origin and movement of water in the ditches, as well as differences in vegetation communities in the ditches. While drainage on average greatly decreases CH₄ emissions from peatlands, a great spatial variability in fluxes is emerged. Emissions from ditches constantly covered with water, may in some cases have a great impact on the overall CH₄ emissions from drained peatlands.     

Nutrient limitation in species-rich lowland fens

Abstract. Nitrogen, phosphorus and potassium were supplied to some Belgian fens of varying nutrient status and productivity. Plant growth in the lowest productive fen with a species-rich Caricion davallianae vegetation was strongly P-limited. N was ineffective when applied alone, but increased the effect of P-addition when applied together. Summer biomass and plant nutrient concentrations were monitored for four years, and showed partial recovery of nutrient limitation. In a more productive fen dominated by Carex lasiocarpa and in a fen meadow, nutrient limitation was less strong. N limited growth in the productive fen, and N and K were co-limiting in the fen meadow. The P-concentration in the productive fen vegetation showed a marked increase after P-fertilization, but it did not result in higher standing crop. The significance of P-limitation for the conservation of species rich low productive fens is discussed. P-limitation may be an essential feature in the conservation of low productive rich fens: because it is less mobile in the landscape than N and/or because it is an intrinsic property of this vegetation type. Plant nutrient concentrations and N:P-ratios may be used as an indication for the presence and type of nutrient limitation in the vegetation. We found N:P-ratios of 23 to 31 for a P-limited site and 8 to 15 in N-limited sites. This was in agreement with critical values from the literature: N:P > ca. 20 for P-limitation and N:P < 14 for N-limitation. Thus, this technique appears valid in the vegetation types that were studied here.     

Patterned fens in Scotland: evidence from vegetation and water chemistry

Mires with attributes similar to the patterned fens of boreal continental regions have recently been reported from northern Scotland. This paper reports on the vegetation and water chemistry of 18 of these sites. Most of the 18 mires displayed remarkable uniformity in their vegetation, with Carex lasiocarpa being a main character species. Major variation of plant communities is associated with microtopographical niches, similar to those found on ombrotrophic mire systems and secondarily with pH and conductivity of surface waters. Nine vegetation noda are described and compared with existing phytosociological associations and National Vegetation Classification (NVC) communities. The dominant Sphagnum - Carex communities are intermediate between the Oxycocco-Sphagnetea and the Caricion lasiocarpae and are thus difficult to assign to existing associations or to NVC communities. Although there is a large variation in pH of surface waters (3.9–6.6), mean measurements for terrestrial and aquatic communities are 5.12 and 5.51 respectively. pH levels are comparable with poor fen systems elsewhere in Britain and slightly higher than patterned fens in continental regions of Europe and North America. The vegeta-tional and chemical attributes of these sites therefore confirm the existence of true patterned fen systems in the British Isles.     

Nutrient limitation in boreal rich‐fen vegetation: A fertilization experiment

Abstract. Rich‐fen vegetation influenced by hay‐making in the Sølendet Nature Reserve, Central Norway, was fertilized with N, P and K in a full‐factorial fertilization experiment to investigate the nutrient limitation of plant growth at both community and species levels. Above‐ground biomass, shoot density and nutrient concentration were measured in several species and groups of species at three sites after two years of fertilization. At the community level, the results indicate multiple limitation by N and P in the two least productive rich‐fen communities: one characterized by small sedges and herbs, and the other by high abundance of Menyanthes trifoliata and tall sedges. Increased nutrient availability had no effect on a more highly productive, tall‐growing, spring‐influenced community, indicating no nutrient limitation. The results at the species level correspond well with those at the community level, indicating multiple limitation by N and P in most of the dominant and sub‐dominant species. However, P seems to limit growth more than N in Succisa pratensis, and N seems to limit growth more than P in Carex panicea. Furthermore, Eriophorum angustifolium seems to be limited by K. The results did not show which nutrient limits the growth of Carex dioica, C. lasiocarpa and Trichophorum cespitosum. Indications that growth in low‐productive, boreal rich‐fen communities is generally limited by P was not confirmed.