Spring-fed Fen Research Articles

The temporal and spatial complexity of carbonate deposition at Romincka forest cupola spring-fed fen (Central Europe) during the Holocene

Calcium carbonate records from alkaline fens provide valuable insights into past climate fluctuations. Yet, the climate is not the sole factor controlling tufa deposition. The present study aims to determine the drivers of postglacial tufa deposition at the exceptionally well-developed cupola alkaline fen located in the north-eastern Poland. Tufa deposition time frames and conditions are reconstructed using radiocarbon dating, geochemical, including loss on ignition and δ13C and δ18O, plant macrofossils, and mollusc analyses of two sediment sequences taken from the top and slope of the fen cupola. The exceptional in young-glacial area continuous Holocene-long history of CaCO3 precipitation was supported by a strong supply of artesian waters. The locally high endogenic heat flow density accelerated permafrost degradation and warranted the early start of artesian water circulation and tufa deposition ca. 11650 cal yr BP. Deposition of interlayered peat and tufa continued until ca. 4700 cal yr BP when the increasing height of the cupola disabled water outflow at the fen top, and peat with scattered CaCO3 started to accumulate. Seepages on the fen slopes supported deposition of interlayered peat and tufa on lower elevated parts of the mound until ca. 2300 cal yr BP. Colder and/or dryer episodes weakened the predominately intensive CaCO3 precipitation mainly at the top of the mound. Vegetation favoured tufa deposition (i) after the development of the soil, which enhanced chemical denudation of carbonate detritus from glacial deposits, (ii) during times of decreased evapotranspiration when the forest cover on the surrounding land diminished. Tufa deposition at the cupola top was limited between ca. 8450 and 4700 cal yr BP when trees entered the fen surface. The human impact on tufa deposition was likely limited except for the melioration of the surrounding area ca. 50 cal yr BP, after which CaCO3 precipitation eventually stopped.

High-resolution record of geochemical, vegetational and molluscan shifts in a Central European spring-fed fen: implications for regional paleoclimate during the early and mid-Holocene

Despite the increasing interest in spring-fed fens’ sediments as a palaeoenvironmental archive, their potential as high-precision climatic records is rarely used to its full extent. Here, we present a detailed early to mid-Holocene record of environmental changes in the Turtul hanging spring-fed fen, northeastern Poland, to test whether the well preserved and accurately subsampled alternating peat and tufa sediments allow us to recognise short-duration local and regional climatic changes. Our reconstructions are based on a loss-on-ignition analysis of the sediment, carbon and oxygen stable isotope values of tufa, and biotic proxies: plant macrofossil and malacological analyses. A detailed environmental reconstruction was possible due to the combination of detailed sampling (1 cm intervals) and high sediment accumulation rates. The two sediment sequences collected from the fen revealed the congruent palaeoenvironmental history; however, the temporal shift associated with the distance of the coring site from the water outflow was also apparent, stressing the need for careful selection of the coring site in palaeoenvironmental research. Peat deposition at Turtul started at 10,300 cal yr BP; however, tufa precipitation did not begin before 9250 cal yr BP. During the most active tufa deposition, from 7850 to 6100 cal yr BP, a high sedimentation rate was observed (0.11–0.25 cm yr−1). We found several abrupt and short-duration declines in carbonate deposition corresponding to climatic fluctuations recorded in geological archives from the southeastern Baltic region. The carbonate drops at 8200–8130, 7900–7850, 7400–7300, 6600–6500, 5980–5870 and 5400 cal yr BP were associated with climate cooling or drying, whereas those at 10,200–9250, 8450–8340 and 6160–6100 cal yr BP can be attributed to drying with no cooling. We conclude that the evident sensitivity of the Turtul fen to climatic shifts that emerge from our high-resolution (one sample every 17 years on average) reconstruction complements the still rare high-resolution palaeoenvironmental records in the area.

A multi-proxy long-term ecological investigation into the development of a late Holocene calcareous spring-fed fen ecosystem (Raganu Mire) and boreal forest at the SE Baltic coast (Latvia)

The calcareous substrate of spring-fed fens makes them unique islands of biodiversity, hosting endangered, vulnerable, and protected vascular plants. Hence, spring-fed fens ecosystems require special conservation attention because many of them are destroyed (e.g. drained, forested) and it is extremely difficult or even impossible to restore the unique hydrogeological and geochemical conditions enabling their function. The long-term perspective of paleoecological studies allows indication of former wetland ecosystem states and provides understanding of their development over millennia. To examine the late Holocene dynamics of a calcareous spring-fed fen (Raganu Mire) ecosystem on the Baltic Sea coast (Latvia) in relation to environmental changes, substrate and human activity, we have undertaken high-resolution analyses of plant macrofossils, pollen, mollusc, stable carbon (δ13C) and oxygen (δ18O) isotopes combined with radiocarbon dating (AMS) in three coring locations. Our study revealed that peat deposits began accumulating ca. 7000 cal. yr BP and calcareous deposits (tufa) from 1450 cal. yr BP, coinciding with regional hydrological changes. Several fire events occurred between 4000 and 1600 cal. yr BP, which appeared to have had a limited effect on local vegetation. The most significant changes in the forest and peatland ecosystems were at 3200 cal. yr BP associated with a dry climate stage and high fire activity, and then between 1400 and 500 cal. yr BP potentially associated with temperature changes during the Medieval Climate Anomaly (MCA) and Little Ice Age. Hydrological disturbances in the peatland catchment from 1400 cal. yr BP were most likely strengthened by human activity (deforestation) in this region. The relationship between the development of this peatland and changes in its catchment area, such as land cover changes or fluctuations in groundwater levels, suggest that protection and restoration of spring-fed fen ecosystems should also include the surrounding catchment. The presence of calcareous sediments, as well as appropriate temperature and local hydrological conditions appear to be the most crucial factors controlling Cladium marisus populations in our site - currently at the eastern limit of its distribution in Europe.

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.

Hydrology of a Southern Appalachian Hypocrene Spring-Fed Fen

ABSTRACT Garland Seep is a Southern Appalachian fen that supports a population of federally endangered green pitcher plants (Sarracenia oreophila). The wetland is underlain by clayey stream deposits above fractured bedrock, is located at the base of a mountain slope, and is fed by groundwater that originates as recharge on the adjacent hillslope. Groundwater wells were installed following a hydrologic restoration in the mid-1990s and have been monitored at varying frequencies since that time. The 20+ year record provides evidence that Garland Seep can be classified as a “hypocrene fen,” in which spring flow rarely reaches the ground surface because of low discharge rates and high evapotranspiration (ET). In general, water-level fluctuations followed seasonal ET patterns, with higher water levels in the winter and early spring (when ET is low) and lower levels in the summer and fall. During wetter years, the water table remained near the ground surface for much of the year, with the clay layer underlying the site retaining moisture even after water levels had dropped. The “clay wetting” period was shorter during dryer years and corresponded with a reduction in the number of pitcher plant clumps observed at the site. In addition to the geologic and climatic controls on hydrology, previous landowners used fire to maintain open space for grazing, and The Nature Conservancy has continued the practice to combat woody vegetation and to open the canopy. Prescribed burns reduce ET (at least initially), cause a rise in water levels, and have helped maintain a thriving Sarracenia population.

Holocene environmental changes in northern Poland recorded in alkaline spring-fed fen deposits – A multi-proxy approach

Spring-fed fen deposits (peat-tufa sequences) from northern Poland were investigated for Holocene environmental reconstruction (climate and hydrology) using multi-proxy analysis (lithofacies, molluscs, pollen, plant macrofossils, geochemistry, and stable oxygen- and carbon-isotopes). The main aims of these studies were: (1) comparison of several similar sites with the same type of groundwater supply and sedimentation on a widespread space scale, (2) detailed reconstruction of their long-term development, assessing their sensitivity to climate change, (3) verification of the synchronicity of the record of different proxies in distant sites in the context of Holocene climate changes in relation to specific well-known global and/or regional climate events (so-called Bond events), and (4) discussion on permafrost degradation as a driver of spring-fed fens development.Based on our palaeogeographical data, we have distinguished an asynchronicity of the beginning of the development of spring-fed fens in the eastern and western parts of the studied region that is associated with different times of ascending groundwater supply unblocking after complete permafrost degradation. Therein, asynchronicity of permafrost degradation was brought about by multiple climatic, geological and structural conditions. Our results also indicate significant differences in the trends of succession (ecological and lithological) caused by the geographical location of the studied sites. Asynchronicity of the occurrence of wet and dry phases, as well as significant differences in their duration were noted. This depended upon the influence of oceanic (western part) or continental climates (eastern part). Warm and humid oceanic climate promoted the domination and longer duration of wet phases (especially in the Eo- and early Mesoholocene), while the harsh continental climate promoted the more frequent occurrence of dry phases, with short episodes of increased humidity. From the middle Mesoholocene, this marked regional diversification becomes less pronounced. Results also allowed for the recognition of several palaeoclimatic events on a regional scale. Four main cold episodes (Bond events 8–5): during LG/H transition (11.5 ky cal BP), Eo- (∼10.25 ky cal BP, ∼9.4 ky cal BP) and at the beginning of the Mesoholocene (∼8.2 ky cal BP) are well-documented by multiple proxies at all study sites. Other cold episodes (Bond events 4–0) are slightly less documented and are not clear for interpretation. The results of our study demonstrate the importance of spring-fed fen deposits for detailed palaeoenvironmental reconstruction on a regional scale.

Current state and vegetation history of spring-fed fens in Western Pomerania (Northern Poland): a case study of the Chociel River valley

Alkaline spring-fed fens are a rare type of soligeneous wetlands, characterised by an alternating arrangement of layers of peat and calcareous tufa, defined as the peat-tufa rhythmite. They are known, for example, from the strongly undulating young glacial landscapes of Central Europe, where many of them are protected by law. These include sites located in the Chociel River valley, in Western Pomerania (Northern Poland). One such spring-fed fen (Bobolice site) was investigated in detail using multiple methods (phytosociological, plant macrofossils, sedimentological and geochemical) for the current state of vegetation, reconstruction of its long-term development and, eventually, the identification of management strategies for its effective protection. Six developmental phases reflecting changes in the natural environment at the end of the Late Glacial and in the Holocene, as well as changes caused by human impacts in recent centuries, were identified for the investigated site. In the past, the dominant role in the formation of the spring-fed fen was attributed to sedge and sedge-moss communities, also with an admixture of Sphagnum in the last phase of the fen’s development. For about 300 years increased human activity has been recorded in the Chociel Valley, resulting in a modification of the water regime and a strong transformation of vegetation. Today, the real vegetation is therefore the result of both the presence of various mire habitats and various types of agricultural use. The current state of spring-fed fens in the Chociel River valley points to the urgent need for the implementation of various active protection measures.

Palaeoecological evolution of a spring-fed fen in Pawłów (eastern Poland)

A continuous record of sedimentation in spring-fed fens makes them suitable for detailed palaeoenvironmental studies. A newly investigated cupola spring-fed fen (Pawłów site), located in the Lublin chalkland, eastern Poland, was the object of our study. This special karst region is characterised by the occurrence of Upper Cretaceous carbonate rocks in the substratum. Sedimentological observations indicated strong variability of biogenic-carbonate series in the deposits (=peat-tufa rhythmite), reflects changes of accumulation conditions (oxidising versus reducing), resulting from alternate occurrence of warmer and cooler periods. Difficulties in pollen analysis due to oxidising conditions necessitate a multidisciplinary approach for palaeoenvironmental reconstruction. We used a multidisciplinary approach (sedimentological, palaeobotanical, geochemical analyses and radiocarbon dating) to determine the main evolutionary stages of this unique fen ecosystem and to discuss the role of local or/and regional factors in its development. Pollen and plant macrofossil analyses, supported by radiocarbon dating, proved that the bottom part of the cores represents the Late Glacial–Early Holocene stages of the fen development. A comparative analysis of palaeoenvironmental data showed close resemblance between the Pawłów fen and the earlier studied fens in eastern Poland and Central-Eastern Europe, and the connection between their development and supraregional hydrological-climatic factors. The results indicated also the influence of the morphological position of such a type of ecosystem on the development of a continuous deposit succession. The occurrence of a river valley in close proximity of the Pawłów site resulted in the lack of tufa deposits from the Atlantic period, because of an erosional phase in the river valley.

Response of a spring-fed fen ecosystem in Central Eastern Europe (NW Romania) to climate changes during the last 4000 years: A high resolution multi-proxy reconstruction

We document the long-term development of a spring-fed fen assessing its sensivity to climate changes over the last ca. 4000 years. Our investigation is based on high-resolution, continuous plant macrofossil remains and mollusc records, complemented by pollen, geochemical analysis and radiocarbon dating of Valea Morii, located in the Feleac Hills (Transylvanian Depression) in NW Romania, Central Eastern Europe. Based on our palaeocological data we have distinguished three stages of wet habitat conditions: two stages between 4000 and 2450 cal yr BP and one in the last 800 cal yr BP, and one dry stage between ca. 2450 and 800 cal yr BP. These local habitat conditions appear to reasonably reflect regional climate characteristics. High-resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession, and stable isotope values from ca. 500 cal yr BP. The appearance of C. mariscus during the last two centuries may be related to increased wetness and associated active CaCO3 precipitation, which allowed this plant to colonise the spring-fed fen studied. However, it can be not excluded that the occurrence and spread of a Cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the Little Ice Age. The potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change, both temperature and humidity, in mountain spring-fed fen deposits is shown. Carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation, soil development and the dissolution of bedrock carbonates, primarily as a reaction to changes in climate humidity.

Origin and Neoholocene evolution of spring-fed fens in Wardzyń, Łódź Upland, central Poland

Spring-fed fens in Wardzyn represent the rare group of alkaline mires supplied by artesian groundwater. Using multidisciplinary methods (including sedimentological, hydrometric and hydrochemical, pollen, macrofossil, malacological, geochemical, radiocarbon dating, and stable oxygen and carbon isotope analyses) we have been able to (1) reconstruct the main phases of spring-fed fen development, and to (2) determine the cause of Neoholocene groundwater ascension responsible for the mire inception. These phases are characterized by cyclic organic (peat) and carbonate (tufa) sedimentation associated with the Holocene fluctuations in humidity and temperature. The beginning of the activation of hydrological systems (involving the flow of confined groundwater of the Cretaceous aquifer) at Wardzyn occurred in the Subboreal period of the Holocene, after a long episode of decreased humidity initiated ca. 4.2 ka cal BP.

Composition of microbial PLFAs and correlations with topsoil characteristics in the rare active travertine spring-fed fen

Abstract We studied soil PLFAs composition and specific soil properties among transect of small-scale fen in Stankovany, Slovakia. The aim of this study was to determine potential differences in the microbial community structure of the fen transect and reveal correlations among PLFAs and specific soil characteristics. PCA analyses of 43 PLFAs showed a separation of the samples along the axis largely influenced by i14:0, 16:1ω5, br17:0, 10Me16:0, cy17:0, cy17:1, br18:0 and 10Me17:0. We measured a high correlation of sample scores and distance from fen edge (Kendall’s test τ = 0.857, P < 0.01). Kendall’s test showed a negative correlation of PLFAs content (mol%) and distance from the fen border for Gram (+) bacteria, Actinomycetes, mid-chain branched saturated PLFAs and total PLFAs. The redundancy analysis of the PLFA data set for the eight samples using PLFAs as species and 21 environmental variables identified soil properties significantly associated with the PLFA variables, as tested by Monte Carlo permutation showing most significant environmental variables including dichlormethan extractables, water extractables, Klason lignin, acid-soluble lignin, holocellulose, total extractables, organic matter content, total PLFA amount, bacterial PLFA and total nitrogen negatively correlated to axis 1 and dry weight and carbonate carbon positively correlated to axis 1. The amounts of Klason lignin, acid-soluble lignin, holocellulose total extractables, total PLFA, bacterial PLFA and total nitrogen were significantly correlated positively to the distance from fen border while moisture and total carbonate carbon were correlated negatively.

Multi-proxy evidence of Holocene climate variability in Volhynia Upland (SE Poland) recorded in spring-fed fen deposits from the Komarów site

Radiocarbon-dated spring-fed fen deposits from the Komarów site (Volhynia Upland, SE Poland) with its multi-proxy data (macrofossils, molluscs, geochemistry, pollen, stable isotopes of oxygen and carbon) enable us (1) to distinguish four main stages of fen evolution, which reflected a distinct variability of water supply conditions and (2) to reconstruct the Holocene humidity–temperature changes. The beginning of peat–tufa deposition took place in a Boreal phase, after a significant cool fluctuation of climate occurring ca. 9.4 ka cal. BP. We suggest that climate was the most important factor conditioning the development of the spring-fed fen. Permafrost degradation, and then wet periods, intensified the activity of ascending springs. The impact of humans was possible since the Neolithic period and increased during the Middle Ages: therefore, the anthropogenic influence could have partially overlapped with the regional tendencies of climate changes. Autogenic development of deposit succession in the studied fen was definitely conditioned by hydrological changes induced by climate. Based on the multi-proxy data, 12 cold events of different ranks were identified. They are also recorded in other Polish and European sites. A record of distinct variability of depositional conditions at ca. 9.4, 8.2, 5.9, 4.6, 2.8, 1.4 and 0.55 ka cal. BP corresponds to quasi-periodical global climate changes in the Holocene named the Bond events. The majority of the cold events recorded in δ13C and δ18O of carbonates can be correlated to the Greenland oxygen isotope curve.

Postglacial history of a marl fen: vegetational stability at Byron-Bergen Swamp, New York

Byron-Bergen Swamp, an 800-ha mire complex in western New York, is a mosaic of hardwood-conifer forest, white cedar swamp, and open nonforested fens dominated by sedges, other herbs, and shrubs. The mire is a sloping, spring-fed rich fen in which marl deposition occurs in the open fens but not under forest. Two cores, 120 m apart, one in a marl fen and the other in a hardwood-conifer swamp, were taken to investigate the history of the mire. Sediment, pollen stratigraphy, and 14 C chronology show that the Holocene record of local vegetation at each coring site was very different. One site was first a shallow marl pool (10 700 - 5600 years BP), then an open shrub-conifer vegetation, and finally a closed hardwood-conifer swamp. The other site progressed from a pine- spruce-tamarack swamp (10 700 - 8000 years BP) to a white cedar swamp (7500-3500 years BP) and then to a marl sedge fen (3500 years BP - present). The spatial arrangement of swamp forest and marl fen changed through time, responding to marl accumulation and lateral shifts in drainage pathways. Marl deposition occurred continu- ously at each site, although at different times, for several thousand years. The pattern of vegetation change that we found is not congruent with that predicted from classical hydrarch succession.