Mineral-rich Fens Research Articles

Re-assessment of phosphorus availability in fens with varying contents of iron and calcium

AimTo further unravel P availability in mineral-rich fens, and test whether high Fe in the soil would lead to low P availability to the vegetation.MethodsMesotrophic fens were selected over gradients in Ca and Fe in central Sweden and the Netherlands, to study characteristics of vegetation, pore water and peat soil, including inorganic and organic forms of P, Fe and Al.ResultsSoil Fe was more important than region or soil Ca, and P availability to the vegetation increased from Fe-poor to Fe-rich fens. Contrary to expectations, precipitation of iron phosphates played a minor role in Fe-rich fens. Fe-rich fens were P-rich for three reasons: (1) high P sorption capacity, (2) relatively weak sorption to Fe-OM complexes and (3) high amounts of sorbed organic P, which probably consists of labile P. Also, nonmycorrhizal wetland plants probably especially take up weakly sorbed (organic) P. However, high P did not lead to high biomass or low plant diversity. Fe-rich fens were limited by other nutrients, and high P may help protect the vegetation against Fe-toxicity.ConclusionsFe-poor fens are P-poor, irrespective of Ca, and Fe-rich fens P-rich even under mesotrophic conditions. However, high P itself does not endanger Fe-rich fens.

Small-scale Variation of Testate Amoeba Assemblages: the Effect of Site Heterogeneity and Empty Shell Inclusion

Studies on testate amoeba species distribution at small scales (i.e., single peatland sites) are rare and mostly focus on bogs or mineral-poor Sphagnum fens, leaving spatial patterns within mineral-rich fens completely unexplored. In this study, two mineral-rich fen sites of contrasting groundwater chemistry and moss layer composition were selected for the analysis of testate amoeba compositional variance within a single site. At each study site, samples from 20 randomly chosen moss-dominated plots were collected with several environmental variables being measured at each sampling spot. We also distinguished between empty shells and living individuals to evaluate the effect of empty shell inclusion on recorded species distribution. At the heterogeneous-rich Sphagnum-fen, a clear composition turnover in testate amoebae between Sphagnum-dominated and brown moss-dominated samples was closely related to water pH, temperature and redox potential. We also found notable species composition variance within the homogeneous calcareous fen, yet it was not as high as for the former site and the likely drivers of community assembly remained unidentified. The exclusion of empty shells provided more accurate data on species distribution as well as their relationship with some environmental variables, particularly moisture. Small-scale variability in species composition of communities seems to be a worthwhile aspect in testate amoeba research and should be considered in future sampling strategies along with a possible empty shell bias for more precise understanding of testate amoeba ecology and paleoecology.

Glacial-relict symptoms in the Western Carpathian flora

Glacial relicts have been regionally more common in glacial than in recent times. A rigorous assessment of which species are indeed glacial relicts is extremely difficult because direct evidence is untraceable or equivocal for many species. We aimed to identify species of the Western Carpathian flora (vascular plants, bryophytes and terrestrial lichens) that display apparent biogeographical and ecological symptoms, suggesting a wider regional or supra-regional distribution during glacial times, or at least before the middle-Holocene climate optimum. We worked with the premise that exemplary relict species should tolerate continental and/or arctic climates, should have large distribution ranges with disjunctions, being regionally rare and ecologically conservative nowadays, should be associated with habitats that occurred during glacial times (tundra, steppe, peatland, open coniferous forest) and should display a restriction of ecological niches in the study region. The assessed species were primarily those with boreo-continental or artcic-alpine distribution. We demonstrated a conspicuous gradient of glacial-relict symptoms, with Carex vaginata, Betula nana, Trichophorum pumilum, Nephroma arcticum, Saxifraga hirculus and Cladonia stellaris topping the ranking. Based on the arbitrary ranking, 289 taxa can be considered high-probability relicts. For only a minority of them, there are any phylogeographical and/or palaeoecological data available from the study area. Biogeographical and ecological symptoms of 144 taxa suggest that they retreated rapidly after the Last Glacial Maximum whereas other species probably retreated later. The first principal component of biogeographical symptoms sorted species from circumpolar arctic-alpine species of acidic peatlands and wet tundra to strongly continental species of steppe, steppe-tundra and mineral-rich fens. This differentiation may mirror the altitudinal zonation of glacial vegetation in the Western Carpathians.

Microsatellite variation in three calcium-tolerant species of peat moss detected specific genotypes of Sphagnum warnstorfii on magnesium-rich bedrock

Peat mosses are a key functional group in peatla nds, driving biogeochemical cycles, habitat development and changes in species composition. They are generally intolerant of calcium and magnesium bicarbonate, but some species are ada pted to mineral-rich fens. A previous study found a coincidence between genetic variation and the ability to tolerate high pH/calcium levels in Sphagnum warnstorfii . Here we compare its microsatellite variation with that of two rarer cal- cium-tolerant species ( Sphagnum subnitens , S. contortum ), using a novel data set from Eurasia. Because physiological experiments indicate that S. warnstorfii can tolerate high magnesium lev- els, we included also samples from dolomite and serpentinite. Genetic diversity of S. warnstorfii was higher than that of other species. The Bayesian analysis in program Structure resulted in two population groups of S. warnstorfii . One group coincided with dolomite (Italy, Austria, Estonia) and moderately magnesium-rich (but calcium-poor) r ocks (serpentinite, metadolerite, cordierite- bearing migmatite on the Bohemian Massif), wh ile the second one coincided with magnesium- poor bedrock across Eurasia. The principal coor dinate analysis revealed a cline between popula - tions from magnesium-rich and magnesium-poor bedrocks, with populations from dolomite and serpentinite forming one extreme. Populations from magnesium-poor bedrock located far from any dolomite or serpentinite formed the opposite ex treme of the cline. We demonstrate for the first time that magnesium toxicity may drive bryophyte microevolution, as has repeatedly been shown for vascular plants, including ferns.

The response of Clitellata (Annelida) to environmental gradients in spring fens

Patterns in aquatic Clitellata assemblage composition are known to be driven by several environmental gradients, with water chemistry and substratum characteristics being particularly important. In this study we explored 54 isolated spring fens across the eastern Czech Republic and Slovakia. These fens varied in calcium and magnesium concentrations, forming a sharp and well defined environmental gradient running from calcium-poor acidic fens to extremely calcium-rich tufa-forming fens. We found that the main changes in clitellate species composition were controlled by this gradient, and/or total organic carbon content, over a wide area, including fen sites differing in other environmental conditions and historical development. However, this pattern was weakened in sites with a high organic matter content, which represented a second driver of change in assemblage composition along with water temperature. Three main types of fens were determined using cluster analysis based on clitellate assemblage composition. However, only the first type, which included tufa-forming fens, was found to fit with the previously established spring fen types based on vegetation (i.e. extremely mineral-rich fens with a tufa, brown-moss mineral-rich fens, mineral-rich Sphagnum fens and mineral-poor Sphagnum fens). The second clitellate type included sites with low temperatures and occasional desiccation, while the third type was characterised by high temperatures and trophy. Using eight environmental predictors, we were able to significantly explain changes in the population abundances of all 12 common species (i.e. recorded at 15-plus sites). The results from individual species modelling also suggests that an increase in organic matter content can trigger compositional shifts towards assemblages of common eurytopic tubificid species. Thus, human-induced eutrophication and negative changes in spring fen hydrology, mainly drying up, can represent a serious threat for species-specific assemblages of aquatic clitellates, especially at alkaline sites due to their isolated and spatially limited nature.

Disjunct Occurrences of Plant Species in the Refugial Mires of Bulgaria

Many mire vascular plant and bryophyte species have disjunct occurrences in Bulgaria despite that most of south-eastern Europe is not suitable for the occurrence of permanently waterlogged and nutrient-limited wetlands due to the current and glacial dry climate conditions as well as prevailing limestone bedrock. Unfortunately, such important distributional data are scattered throughout numerous papers and reports, and are not adequately provided even by national checklists and floras. No attempt to summarize them has been done yet. Therefore, the main aim of this paper is to review and enlarge such data, and to use the resulting data set to address the question whether the disjunctly occurring rare species are concentrated in certain mire complexes or even in particular vegetation plots and if they do characterize such localities. Our current research shows that the phenomenon of isolated occurrences of mire plants in Bulgaria is even more widespread than previously thought. Seventeen species were found as new for Bulgaria with their distribution range limits there, and distributional data of many other species, including some previously considered extinct, were enlarged. Fifty-four mire species were found at only three or fewer sites. Our analyses showed a conspicuous concentration of rare, disjunctly occurring species at a few sites, which are, however, largely unexplored in terms of palaeoecology or ecology, not legally protected and currently threatened by human activities. The distributions of target rare species within Bulgarian mires were significantly nested, which means that more species-poor assemblages were subsets of richer ones. Nestedness was significantly related to the estimated area of mire complex, but not all high-diversity mires were large. Disjunctly occurring rare species were more concentrated in particular vegetation plots at lower altitudes and in mineral-rich fens. Fragmentary data about the ecology and history of Bulgarian refugial mires suggest that these mires harbour specific ecotypes and genotypes, contain specifically distributed biogeographic groups of species, provide an opportunity to test biogeographical hypotheses and shelter crucial information about the history of European mires. Thus, these sites have a potential to become a source of very important information for biogeographical, palaeoecological, and phylogeographical analyses.

Higher acidification rates in fens with phosphorus enrichment

AbstractQuestion: 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.

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.

COMPOSITION AND SPECIES RICHNESS OF MOLLUSCAN COMMUNITIES IN RELATION TO VEGETATION AND WATER CHEMISTRY IN THE WESTERN CARPATHIAN SPRING FENS: THE POOR–RICH GRADIENT

Molluscs, vegetation and water chemistry were investigated at 48 spring fens situated in the borderland between the Czech Republic and Slovakia in 1997–2000. The purpose of this study was to test whether the gradient from mineral-poor to mineral-rich fens is reflected in the composition and species richness of mollusc communities, and to determine the importance of vegetation in predicting the mollusc community composition. A cluster analysis of mollusc communities separated the fens studied into five basic clusters which accord well with the results of detrended correspondence analysis (DCA). These clusters are arranged along the first DCA axis following the poor–rich trophic gradient. Ca, Mg, Fe, K, pH and conductivity are strongly correlated with the first DCA axis of the mollusc data. Similarly, Ca, Mg, Fe, pH and conductivity explain a substantial part of species-data variation, as verified by separated canonical correspondence analyses (CCAs) with a single variable. When sites with Sphagnum spp. were excluded, no significant correlations with K, pH and conductivity were found, whereas the significance of correlation with Fe increased markedly. Site classifications based on mollusc data are applicable to vegetation data and vice versa. Vegetation composition is a more important factor for explaining the variation in mollusc species than water chemistry when both are included in two separated CCAs as constraining variables. We found a linear correlation between mollusc species richness and water calcium concentration in the poor fens. In the rich fens, such a correlation was not found, and species richness was dependent on other abiotic and biotic factors, namely the Fe concentration and the water regime.

Contrasting the sorption of Zn by oxyhydroxides of Mn and Fe, and organic matter along a mineral-poor to mineral-rich fen gradient

The geochemistry of Mn and Fe in surface pools, pore-waters and surface peats and the sorption of Zn by the surface peats was contrasted among 15 peatlands sampled along a mineral-poor to mineral-rich fen gradient. Sorption of Zn by surficial peats was compared via distribution coefficients, both total (K DT) and partial (K DERMn, K DRFe and K DORG), where ER Mn, R Fe and ORG are amounts of Zn recovered from the easily reducible Mn oxides, reducible Fe oxides, and organic components of peat, respectively. Apparent stability constants (K As) for Zn sorption onto oxides of Fe recovered from the surface peats were also calculated and compared along the same gradient. Peat geochemistry was peatland dependent; mineral-poor fens had less easily reducible Mn and greater amounts of organic matter (%Loss on Ignition; LOI) versus mineral-rich fens (range of 0.66–8.6 mm kg −1 for ER Mn and 20–88% LOI for organic matter). Reducible Fe also varied among peatlands (range 51–315 mm kg −1) but was independent of the mineral-poor to mineral-rich fen gradient. Comparison of partial K Ds for amounts of Zn sorped onto the ER Mn, R Fe and ORG components of peat indicated that sorption was dominated by R Fe in all peatlands. K DTs ranged from 0.54–2.00. In contrast to other aquatic systems, however, the range in K DTs was not related to either surface or pore-water pH. K As ranged from 0.36 to 3.06 and were also independent of surface or pore-water pH. However, average K As (but not K DTs), were greater for mineral-poor fens ( P<0.02), suggesting greater Zn binding by surface peats of mineral-poor fens versus either the moderately poor or mineral-rich peatlands. Other water chemistry variables, such as pore-water base cation concentrations, weakly correlated to Zn partitioning onto R Fe ( r=−0.35, P=0.05), but did not fully explain differences in Zn partitioning among peatlands. Greater average K As for the mineral-poor peatlands may in part be due to the presence of strong metal-organic matter-Fe oxide complexes in the Sphagnum dominated peatlands as well as lower pore-water base cation concentrations that occur in the mineral-poor peatland as compared to the more mineral-rich fens.

Base cation composition of pore water, peat and pool water of fifteen Ontario peatlands: Implications for peatland acidification

Base cation (Ca, Mg, Na, K) concentrations in surface waters, pore waters and surface peats were determined along a mineral-poor to mineral-rich fen gradient for 15 south-central Ontario peatlands. Surface waters of the peatlands ranged in pH and alkalinity from 4.5 to 6.3 and 0 to 181μeqL−1, respectively. Both surface water and pore water Ca and Mg concentrations followed the expected decrease along the mineral-rich to poor-fen gradient. Surface water concentrations of Ca and Mg were significantly lower in the mineral-poor versus the moderately-poor and mineral-rich fens (P<0.05, ANOVA). Pore water concentrations of base cations were 3–5 fold less in mineral-poor vs. mineral-rich fens. In contrast to surface and pore waters, peat base cation concentrations did not decrease along the mineral-rich to mineral-poor fen gradient. Surface peat base cation concentrations were also independent of pore water cation concentrations, and local bedrock geology. Relative concentrations of base cations in surface peats of all peatlands were best described by the exchangeable cation capacity of the surrounding soils.

Contrasting the geochemistry of aluminum among peatlands

Aluminum concentrations were measured in surface waters, pore waters and surface peats of 15 wetlands in south-central Ontario. Wetlands were grouped floristically and chemically as mineralpoor, moderately-poor or mineral-rich fen. Mineral-poor fens were dominated bySphagnum, were low in alkalinity (0.31μeq L−1) and pH (4.5–6.3). Moderately-poor fens had a mixture of vegetation (Sphagnum, sedges and grasses), mid-alkalinity (23–91μeq L−1) and pH (5.8–6.4). Mineral-rich fens were dominated by sedges and grasses, had high alkalinity (104–181μeq L−1) and circumneutral pH (6.2–6.3). Surface water Al concentrations were less in mineral-poor versus moderately-poor and mineral-rich fens (F=32.0; P<0.05). Pore water Al concentrations were lower in 4 of 5 mineral versus the mineral-rich fens (F=92.15; P<0.05). In all but two cases pore water Al (all species <0.2μm) were greater within the fen peats versus the overlying surface waters suggesting that peats could act as a source of Al to the overlying waters. In all wetlands, 70 and 30% of peat Al was recovered by a hydroxylamine hydrochloride/acetic extract (primarily inroganic) and an ammonium hydroxide extract (primarily organic), respectively. Differences in “extractable” Al recovered by the two reagents (i.e., inorganic+organic Al) among the 15 wetlands were independent of wetland type. Distribution coefficients, k d , were different among the 3 types of wetlands (F=25.0; P<0.05) with theSphagnum dominated mineral-poor fens containing higher values versus the sedge and grass dominated mineral-rich fens. Lower surface and pore water concentrations of Al in mineralpoor versus mineral-rich fens may in part be a result of differences in the degree of minerotrophic influences between the two types of peatlands. As well, the greater binding capacity ofSphagnum peat as indicated by higher k d 's in the mineral-poor fens, may have contributed to the observed lower pore water and surface water Al concentrations in mineral-poor versus mineral-rich fens. It has been postulated that anthropogenic acidification of peatlands will accelerate the transformation of a mineral-rich fen to that of a mineral-poor fen and ultimately to bog. Changes in Al geochemistry that may ensue as this transition occurs include decreases in pore and surface water Al concentrations with concurrent increases in peat bound Al.

Metal concentrations in chrionomids in relation to peatland geochemistry

Concentrations of Zn, Cu, Al, Fe, and Mn were determined in Chironomidae (Diptera) larvae sampled from three sites within eight peatlands, located in south-central Ontario, Canada. The eight peatlands displayed a range in pH and alkalinity and were classified abiotically (i.e., chemically, hydrologically) and biotically (i.e., dominant vegetation present) as mineral-poor, moderately poor, or as mineral-rich fen. Surface peats of mineral-poor fens were distinct from those of moderately poor and mineral-rich fens; mineral-poor fens contained higher concentrations of organic matter with low concentrations of easily reducible Mn vs. the moderately poor and mineral rich fens. A one-way nested ANOVA indicated that chironomid metal concentrations were peatland dependent (P<0.05). To determine if differences in chironomid metal concentrations among the peatlands could be related to peat geochemistry, an R2 MAX procedure using peat geochemistry as the independent variable and chironomid metal concentrations as the dependent variable was applied. Peat geochemistry was defined as concentrations of peat organic matter, reducible Fe (Fe oxides), reducible Mn (Mn oxides) and easily reducible metal (where metal = Zn, Cu, Al, Mn and Fe), and reducible metal and organically bound metal. Chironomids from mineralrich peatlands, i.e., peatlands low in organic matter with high concentrations of reducible Mn and Fe or easily extractable metal contained greater concentrations of Zn, Mn, and Fe vs. chironomids sampled from mineral poor peatlands, i.e., peatlands with high concentrations of peat organic matter and low concentrations of reducible Mn or easily extractable metal. In contrast, Cu concentrations were greatest in larvae sampled from mineral-poor vs. mineral-rich peatlands. Aluminum larvae concentrations were independent of peat geochemistry. We suggest that bioavailability of metals such as Zn, Fe, and Mn will be greater to invertebrates inhabiting mineral rich vs. mineral poor fens, whereas greater chironomid Cu concentrations will be found in chironomids sampled from mineral poor fens. Differences in metal availability to invertebrates among peatland types has important implications when comparing the impact of contaminant transfer to higher trophic levels among different types of peatlands.