Peat Accumulation Research Articles

Dynamics of mire ecosystems of Siberia in the Holocene and paludification process at the present stage

The paper considers the Holocene paludification process in West Siberian Plain; peat increase for the entire Holocene according to radiocarbon dating of peat deposits. The comparison of results by peat accumulation activity with the climate of Western Siberia in the Holocene is carried out, and the forecast of the natural evolution of mires is given. To determine the contemporary accumulation rate and linear peat increment, we used the model of peat and carbon accumulation process, and the field studies of carbon balance parameters of oligotrophic bog catena as an example. The modern rates of carbon accumulation and the linear peat increment of some types of mires were determined. The field studies of carbon balance parameters on the example of oligotrophic bog catena showed, in years with different climatic conditions, the NPP values varied from 206 to 337 g Cm−2 year−1. Most of the carbon losses are the carbon dioxide emission (an average is 61.3 g Cm−2 year−1, or 23.5 % NPP). The carbon flux, determined by the model of the removal chemicals, is 3.0% NPP with a mean value 7.9 g Cm−2 year−1. The calculations of the carbon balance indicate the progression of the paludification process in the studied area.

Preliminary data on formation and depositional environments of lake Chaika in the central part of the Curonian Spit (Kaliningrad region, Russia, South-Eastern Baltic)

Lake Chaika is the only major water body present in the sand barriers of the entire territory of South-Eastern Baltic shoreline. The article provides new insights into the formation of Lake Chaika, based on data acquired through a lithological investigation of the lake sediment core combined with an organic matter content analysis, a macrofossil analysis, a radiocarbon AMS-dating and a bathymetric survey. The study revealed that Lake Chaika was formed around 500 years ago. The kettle of the lake appears to have not been submerged during the Littorina transgressions. During the mid-late Holocene, the kettle of the lake was occupied by the peat-forming ecosystems of alder carrs and sedge fens with scattered alder. The accumulation of ligneous and sedge peat occurred. The sand horizon, separating the gyttja layer from peat deposits, is considered to be a time marker for the so-called “sand disaster”, which began in the study site 200-250 years earlier than in the main territory of the Curonian Spit. There are three main formation phases of the lake’s ecosystem: the period of carrs (5390–510 cal. yr BP), the “sand disaster” period (≈550–500 cal. yr BP) and the proper lake period (500 cal. yr BP – present time).

Evolution of a paleolake on Russian Island (Sea of Japan) in middle-late Holocene: record of sea-level oscillations, extreme storms and tsunami

The diatom algae from sediments of a paleolake serve as records of changes to environments over the last 7500 cal yr. The lagoon lake formed when the sea level approximately corresponded to the present-day position. Evolution of the paleolake was controlled by sea-level oscillations and humidity changes. Eight stages have been distinguished. During a dry episode in 7330–7090 cal yr BP the lake size decreased. The salinity reached maximal values at the Holocene transgression peak. Three stages of a higher salinity are recognized (6750–6500, 6080–5830, 5420–5090 cal yr BP). A severe flood occurred in 6080–6000 cal yr BP. The brackish-water lake existed in ∼5090 cal yr BP and the freshwater lake in ∼4090 cal yr BP. A prolonged phase of decreasing humidity, associated with a weakening of summer monsoons, led to a drop in sedimentation rates in ∼3510 cal yr BP. Peat accumulation started at the Little Ice Age. The lake was transformed into a swamp during drop in precipitations in ∼270 cal yr BP. Presence of marine diatoms typical in bay and deep-water forms are evidence of influence of extreme storms and tsunami. The age of the paleotsunami coincides well with the regional data.

PALEOGEOGRAPHICAL CONDITIONS FOR FORMATION OF COAL-BEARING THICKNESS OF THE LYUBELYA FIELD OF THE LVIV-VOLYN BASIN ON THE BASIS OF THE ANALYSIS OF LITHOLOGICAL-STRATIGRAPHIC SECTION

Determination of paleogeographical conditions for formation of coal-bearing formation of the Lyubelya field of the Lviv-Volyn Basin was conducted on the basis of the analysis of lithological-stratigraphical sections in area of the of the Lyubelya-3 plot. Studies of coal-bearing thickness wither the limits of the separate plot of the field will enable us to investigate in detail the evolution of the peat accumulation of the field in general and will help to interpret tectonic movements, to determine facies associations and to reproduce paleorelief.By lithological composition the studied thickness is mainly of aleurolite-argillite composition with some layers of sandstones, limestones and coal seams. Its accumulation occurred while alternating of marine shallow-water, near-shelf lagoon-bog and continental conditions. Smooth relief and humid tropical climate, the presence of boggy plots located on the open coast of the shallow sea contributed to the accumulation.In the studied territory, an intensive lowering of the south-western of the territory of the Lyubelya-3 plot in Serpukhovian time of the Lower Carboniferous is observed. Sufficient in flux of terrigenous material, creation of conditions for compensating sedimentation that promoted wide bogging of the locality and formatting of paleopeat deposits were connected with it. North-eastern and eastern parts of the plot underwent perceptible rising movements that is observed by the change in the lithological-facies of rocks.Obtained results confirm the common notions of paleogeographical conditions for the formation of coal-bearing thickness of the Lyubelya field of the Lviv-Volyn Basin. With common regressive trending and cyclic character of sedimentation the formation of relatively thick terrigenous polyfacial thickness with the layers of coal and limestone occurred. Common regressive trending caused by rising movements in the field of the Ukrainian crystalline shield led to receding of the sea in the south-western direction. In addition the gradual widening of continental situations of sedimentation and reducing of marine ones occurred.

Фізико-географічна характеристика Лемківщини

The article presents the physical-geographical characteristics of the Lemkos’ ethnic territory, the farthest western ethnographic group of Ukrainians who have long inhabited the slopes of the Carpathians Eastern Beskids. Lemkivshchyna is located on both slopes of the Carpathian Beskids between the Borzhava and San rivers in the east and Poprad and Dunajec in the west, located in three countries. The total area is about 9 000 km2. Lemkivschyna occupies the largest area within the mountainous part of South-Eastern Poland (48 %), less in the mountainous part of north-eastern Slovakia (41 %), the least in the Trans¬carpathian region of Ukraine (11 %). Most of the territory of Lemkivshchyna is located in the Carpathian lowlands of the Eastern Beskids. Only some peaks have a height of more than 1 000 m. The highest peak is Tarnitsa (1 346 m a.s.l.) on the Bukovo Berdo ridge. Lemkivshchyna is located in the temperate climate zone of Europe, which is formed under the influence of the western transfer of the Atlantic air masses. In addition, the climatic characteristics are influenced by the terrain, altitude, exposure of the slopes, the direction of extension of the mountain valleys. The territory of Lemkivshchyna lies on the Main European Watershed. The rivers that originate in the northern macro-slope of the Low Beskid are tributaries of the Vistula (the Baltic Sea basin). The rivers of the southern macro-slope are tributaries of the Tisza River, which flows into the Danube (the Black Sea basin). The largest river in the Lemky region is the San (444 km in length). Another tributary of the Vistula is the Vislok (165 km). The mountain rivers that originate on the southern slopes of the Low Beskid River flow in a meridional direction to the south and belong to the Tisza basin. The largest among them are Gorand (286 km), Poprad (169 km), Laborets (129 km), Ondava (112 km in length). The rivers of Lemkivshchyna are characterized by mixed food dominated by snow. Boundaries are observed in winter and during the dry season in summer. Floods can occur at any time of the year during heavy rainfall. The mountain-forest soils of Lemkivshchyna are formed on flysch rocks under beech and fir forests. Soils of low power (up to 75 cm), often stony, characterized by high acidity, poor in calcium, magnesium, phosphorus, iron. Mountain-meadow soils were formed in the subalpine meadows. The processes of accumulation of peat and organic material are observed on the watersheds and sites of poor runoff. The geographical location of Lemkivshchyna causes the vertical extent of the vegetation cover, which differs from the other mountain ranges of the Carpathians. Belt of deciduous forests, rising to an altitude of 1 156 m. is mainly represented with beech forests. The belt of the Polonynian subalpine meadows that developed under the influence of a long pasture farm is above the beech forests. About 1 000 species of vascular plants, more than 600 species of mosses and lichens, and many algae and fungi have been found in the Lemky region. A modern feature of the vegetation cover of Lemkivshchyna is the natural regeneration of forests, which occurred after the expulsion of the ethnic population from these territories. More than 200 species of vertebrates have been found in the Lemky region. Key words: Lemkivshchyna, physical and geographical conditions, relief of the Eastern Beskids, hydrography, vegetation.

Carbon isotopic evidence for rapid methane clathrate release recorded in coals at the terminus of the Late Palaeozoic Ice Age

The end of the Late Palaeozoic Ice Age (LPIA) ushered in a period of significant change in Earth’s carbon cycle, demonstrated by the widespread occurrence of coals worldwide. In this study, we present stratigraphically constrained organic stable carbon isotope (δ13Corg) data for Early Permian coals (312 vitrain samples) from the Moatize Basin, Mozambique, which record the transition from global icehouse to greenhouse conditions. These coals exhibit a three-stage evolution in atmospheric δ13C from the Artinskian to the Kungurian. Early Kungurian coals effectively record the presence of the short-lived Kungurian Carbon Isotopic Excursion (KCIE), associated with the proposed rapid release of methane clathrates during deglaciation at the terminus of the Late Palaeozoic Ice Age (LPIA), with no observed disruption to peat-forming and terrestrial plant communities. δ13Corg variations in coals from the Moatize Basin are cyclic in nature on the order of 103–105 years and reflect changes in δ13Corg of ~±1‰ during periods of stable peat accumulation, supporting observations from Palaeozoic coals elsewhere. These cyclic variations express palaeoenvironmental factors constraining peat growth and deposition, associated with changes in base level. This study also demonstrates the effectiveness of vitrain in coal as a geochemical tool for recording global atmospheric change during the Late Palaeozoic.

Stable isotope signatures of Holocene syngenetic permafrost trace seabird presence in the Thule District (NW Greenland)

Abstract. Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water Polynya (NOW) in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq, north of Cape York, is radiocarbon-dated to 4400 cal BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the Wolstenholme Fjord started 5650 cal BP. Both species provide marine-derived nutrients (MDNs) that fertilize vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset, decrease over time, and were about 2-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C∕N ratios and less depleted δ13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to δ15N trends, where decreasing accumulation led to increasing depletion in δ15N as seen in the little-auk-related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable δ15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first stable-water isotopic record from Greenland with mean δ18O of -18.0±0.8 ‰, mean δD of -136.2±5.7 ‰, mean d excess of 7.7±0.7 ‰, and a δ18O-δD slope of 7.27, which is close to those of the modern Thule meteoric water line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-center, dry-out, and polygon-high-center stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of neoglacial cooling and the establishment of the NOW, thus indirectly following the Holocene climate trends.

HYDROLOGICAL FUNCTION OF A MOUNTAIN FEN AT LOW ELEVATION UNDER DRY CONDITIONS

AbstractMountain fens are limited in their spatial extent but are vital ecosystems for biodiversity, habitat, and carbon and water cycling. Studies of fen hydrological function in northern regions indicate the timing and magnitude of runoff is variable, with atmospheric and environmental conditions playing key roles in runoff production. How the complex ecohydrological processes of mountain fens that govern water storage and release as well as peat accumulation will respond to a warmer and less snowy future climate is unclear. To provide insight, we studied the hydrological processes and function of Sibbald fen, located at the low end of the known elevation range in the Canadian Rocky Mountains, over a dry period. We added an evapotranspiration function to the Spence hydrological function method to better account for storage loss. When frozen in spring and early summer, the fen primarily transmits water. When thawed, the fen's hydrological function switches from water transmission to water release, leading to a summertime water table decline of nearly 1 m. Rainfall events larger than 5 mm can transiently switch fen hydrological function to storage, followed by contribution, depending on antecedent conditions. The evapotranspiration function was dominant only for a brief period in late June and early July when rainfall was low and the ground was still partially frozen, even though evapotranspiration accounted for the largest loss of storage from the system. This research highlights the mechanisms by which mountain peatlands supply baseflow during drought conditions, and the importance of frozen ground and rainfall in regulating their hydrological function. The study has important implications for the sustainability of low elevation mountain fens under climate change.

Middle-Holocene environmental change and archaeology in coastal wetlands: Further implications for our understanding of the history ofTaxuswoodland

A radiocarbon-dated multi-proxy palaeoenvironmental record from Beckton in the Lower Thames Valley, Southern England, has permitted a detailed reconstruction of human activities and environmental change during the middle-Holocene. Peat accumulation occurred over river terrace gravels from ca. 7200 to 6600 until at least 3450–3240 cal. BP, and in the later period a trackway and platform structure provide unequivocal evidence for human exploitation of the floodplain environment during the Bronze Age. The site is unique in offering the first certain evidence of the utilisation of Taxus in the construction of a wooden prehistoric platform. Across north-west Europe during the middle-Holocene, the colonisation of Taxus on peat is well documented; at Beckton, it occurred between ca. 5220–4940 and 4410–4220 cal. BP. This research provides important insights into the former distribution of Taxus, and reasons for its expansion and decline during the Holocene, which has relevance to present-day concerns over the conservation and management of Taxus woodland. Abandonment of the site occurred in response to environmental change to wetter conditions. The study employed multi-proxy analyses, including pollen, plant and wood macrofossils, and uniquely Coleoptera; Coleopteran analysis has significant potential to enhance understandings of environmental change and human–environment interactions in coastal wetland research.

Sphagnum outcompetes feathermosses in their photosynthetic adaptation to postharvest black spruce forests

Mosses dominate the understory of black spruce forest, and changes in moss community composition and functional traits may influence many important ecosystem processes, particularly paludification due to accumulation of peat (mainly Sphagnum). To understand performance and fitness of ground-cover mosses in early forest succession following clearcutting, we investigated photosynthetic traits in Sphagnum and three feathermoss species (i.e., Hylocomium, Ptilium, and Pleurozium) coexisting in mature stands and decade-old black spruce harvest blocks. The results showed that all of these mosses have a significantly higher light saturation point at the harvested plots than the forested plots. Feathermosses at the harvested plots all underwent a reduction in quantum efficiency, chlorophyll b content, and chlorophylls:carotenoids ratio related to photoinhibition, particularly Pleurozium, which experienced a significant decrease in maximum net photosynthesis. In contrast, Sphagnum showed a significant increase in maximum gross photosynthesis, dark respiration, and the ratio of chlorophyll a:b at the harvested plots compared with the forested plots. The distinctive responses of moss photosynthetic traits indicate the potential proliferation of Sphagnum and decrease of feathermosses, and thus consequent peat accumulation. Our results emphasize the importance of the photosynthetic traits of moss as indicators of postharvest conditions for enhancing understory vegetation management to maintain and improve productivity of black spruce.

Microbial Community Structure and Methane Cycling Potential along a Thermokarst Pond-Peatland Continuum.

The thawing of ice-rich permafrost soils in northern peatlands leads to the formation of thermokarst ponds, surrounded by organic-rich soils. These aquatic ecosystems are sites of intense microbial activity, and CO2 and CH4 emissions. Many of the pond systems in northern landscapes and their surrounding peatlands are hydrologically contiguous, but little is known about the microbial connectivity of concentric habitats around the thermokarst ponds, or the effects of peat accumulation and infilling on the microbial communities. Here we investigated microbial community structure and abundance in a thermokarst pond-peatland system in subarctic Canada. Several lineages were ubiquitous, supporting a prokaryotic continuum from the thermokarst pond to surrounding peatlands. However, the microbial community structure shifted from typical aerobic freshwater microorganisms (Betaproteobacteria and Alphaproteobacteria) in the pond towards acidophilic and anaerobic lineages (Acidobacteria and Choroflexi) in the connected peatland waters, likely selected by the acidification of the water by Sphagnum mosses. Marked changes in abundance and community composition of methane cycling microorganisms were detected along the thermokarst pond-peatland transects, suggesting fine tuning of C-1 carbon cycling within a highly connected system, and warranting the need for higher spatial resolution across the thermokarst landscape to accurately predict net greenhouse gas emissions from northern peatlands.

Controls on soil carbon dioxide and methane fluxes from a peat swamp vary by hydrogeomorphic setting

AbstractCarbon dynamics of temperate peat swamps are a largely understudied component of wetland carbon cycling. Under a changing climate, hydrometeorological conditions may change, and understanding how peat swamps may be impacted is important. We investigated the importance of hydrogeomorphic setting on controlling soil carbon dioxide (CO2) and methane (CH4) fluxes from a temperate peat swamp in southern Ontario, Canada over a 3‐year period. We chose three different hydrogeomorphic settings: (a) a site with strong wetland‐stream interactions (i.e., an unconfined stream channel; unconfined), (b) a site with limited wetland‐stream interactions (confined), and (c) an interior site (no wetland–stream interaction). The differing hydrogeomorphic conditions between the sites resulted in differences in carbon fluxes. The unconfined site maintained a higher water table across all three study years, providing conditions that are not favourable to CO2 production. The confined and interior sites sustained a much lower water table, with conditions more conducive to CO2 efflux. The unconfined site also had the highest CH4 emissions due to the increased anoxic conditions favourable for CH4 production as a result of the higher water table position. Hydrogeomorphic setting was found to be important for understanding within site variation, suggesting the sites may respond differently to longer‐term shifts in environmental conditions. This may change relationships between sites if the responses are strong enough to significantly alter carbon fluxes, decomposition, and potential peat accumulation rates. It is important to understand the locally specific responses to environmental conditions within peat swamp ecosystems, in order to make future predictions about whole ecosystem function under changing conditions.

Age mark of holocen soil formation of Moscow region′s (upper Klyazma basin)

Radiocarbon studies of three pits in the upper Klyazma river basin near the village of Chashnikovo were carried out to determine the age of buried peat and soils. On the basis of nine radiocarbon dates, the age mark of the beginning of waterlogging on the watershed hill (1650 or 1790 years AD), the termination of the activity of the hydrocarbonate source and the beginning of soil formation in the rear of the high floodplain (about 300 years BC), as well as the age of water drain/drainage of the glacial lake and the beginning of peat accumulation (about 9.3 thousand years BC) in the upper Klyazma valley were determined. The isotopic composition (18О, 13C) and Genesis of travertine-like carbonates, the deposition of which is presumably associated with the activity of the hydrocarbonate source, were determined.

Palynofloral diversity and palaeoenvironments of early Eocene Akri lignite succession, Kutch Basin, western India

This study presents palynological analysis of lignite-bearing succession of Akri lignite mine, Kutch, Gujarat, and discussed the implications of the recovered palynomorphs for age, palaeovegetation and palaeoenvironments. A diverse palynological assemblage consisting of algal and fungal remains, pteridophytic spores, angiosperm pollen and dinoflagellate cysts has been recorded. The lower part of the succession (samples 1–5) is dominated by marine dinoflagellate cysts along with palm pollen belonging to family Arecaceae. The upper part of the succession (samples 6–8, 11) is dominated by terrestrial palynomorphs attributed to megathermal families (Bombacaceae, Ctenolophonaceae, Dipterocarpaceae, Meliaceae) followed by mangrove and back-mangrove elements. An early Ypresian age is inferred for the Akri lignite deposit, whereas a middle Ypresian–early Lutetian age is assigned to the post-lignite succession based on the age-diagnostic dinoflagellate cysts and spore-pollen assemblage. Furthermore, based on the distribution of marine and terrestrial palynomorphs, two palynological assemblages (A and B) have been recognised that are apparently controlled by changing depositional environment. The overall palynological assemblage points to a dense tropical rainforest that thrived in the vicinity of the depositional basin under high precipitation regime of warm and humid climate. The peat accumulation took place in a near-shore coastal swamp which was interrupted by fluctuating marine influences, followed by increased siliciclastic influx in a low-salinity coastal swamp dominated by mangroves. Moreover, the palynological comparison suggests that widespread lignite-bearing successions in the western Indian region are in part coeval and belong to the early Eocene (Ypresian) age.

Petrographic and mineralogical study of extended outcrops of lignite layers in Agbor area, southern Nigeria

Coal layers up to 1 m thick, exposed mainly on river banks in the vicinity of Agbor, Okhuokhuo and Ubiaja, Southern Nigeria, were examined by means of organic petrology, mineralogy and geochemistry, in order to gain coal quality data and understand the palaeoenvironmental conditions during peat accumulation in the broad area of the Ogwashi-Asaba Formation. The obtained results show that coal is of low-rank C; it overlies mainly claystone derived from flooding of branches of the palaeo-Niger River. The precursor peat was accumulating in mires under mesotrophic to ombrotrophic, anoxic conditions. The peat-forming vegetation represented mainly herbaceous plants with minor tree contribution. Though the number of studied samples is low, the distribution of the lignite layers extends further towards N.NW of the known lignite-bearing area. Taking into consideration the low ash yields of some samples, there are encouraging indications for notable lignite deposits of high quality. The mineralogical composition and the activity concentrations of 238U, 226Ra, 232Th and 40K exclude any severe environmental effect from coal exploitation. Due to all these promising evidences, a detailed exploration in these and between these outcrops is recommended in order to estimate the lignite potential hosted in this area.

The Falkland Islands’ palaeoecological response to millennial‐scale climate perturbations during the Pleistocene–Holocene transition: Implications for future vegetation stability in the southern ocean islands

ABSTRACTOceanic island flora is vulnerable to future climate warming, which is likely to promote changes in vegetation composition, and invasion of non‐native species. Sub‐Antarctic islands are predicted to experience rapid warming during the next century; therefore, establishing trajectories of change in vegetation communities is essential for developing conservation strategies to preserve biological diversity. We present a Late‐glacial‐early Holocene (16 500–6450 cal a bp) palaeoecological record from Hooker's Point, Falkland Islands (Islas Malvinas), South Atlantic. This period spans the Pleistocene‐Holocene transition, providing insight into biological responses to abrupt climate change. Pollen and plant macrofossil records appear insensitive to climatic cooling during the Late‐glacial, but undergo rapid turnover in response to regional warming. The absence of trees throughout the Late‐glacial‐early Holocene enables the recognition of far‐travelled pollen from southern South America. The first occurrence of Nothofagus (southern beech) may reflect changes in the strength and/or position of the Southern Westerly Wind Belt during the Late‐glacial period. Peat inception and accumulation at Hooker's Point is likely to be promoted by the recalcitrant litter of wind‐adapted flora. This recalcitrant litter helps to explain widespread peatland development in a comparatively dry environment, and suggests that wind‐adapted peatlands can remain carbon sinks even under low precipitation regimes. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd.

New data of vegetation development of North Baikal area in the Middle-Late Holocene

For the first time, a continuous section of peat was obtained from the hard-to-reach mid-mountain North-Western part of the lake Baikal. The material was studied by methods of spore-pollen analysis, analysis of plant cell residues and radiocarbon Dating (data calibrated). The least identified in the Holocene speed of peat accumulation in the Baikal area. According to the calculated sedimentation rates, the temporal resolution of the study ranges from 100 years at the bottom of the incision to 800 years at the top. With a factor analysis identified six local pallinson and five Botanic zones. Changes in the vegetation cover and ecotope moisture conditions for 7670 years were reconstructed. For the first time in a quarter of a century, the height of the upper forest boundary has been clarified.

Mechanisms for the Development of Microform Patterns in Peatlands of the Hudson Bay Lowland

Spatial surface patterns of hummocks, hollows, ridges, and pools (microtopography) are common features of many northern peatlands and are particularly distinct within the vast peatlands of the Hudson Bay Lowland (HBL), Canada. Hypotheses and models describe how small-scale feedbacks among vegetation, hydrology, and nutrients cause spatial differences in peat accumulation that enable microforms and surface patterns to develop over time. Empirical tests of the predictions from theoretical models of these proposed feedback mechanisms are limited, particularly in large peatland complexes such as the HBL. We investigate feedbacks controlling peatland structure and function in an ombrogenous bog and a minerogenous fen in the HBL. Our sites represent surface patterns found in many northern peatlands, specifically spatially irregular hummocks and hollows, and parallel ridges and pools that are perpendicular to slope. We found the occurrence of different spatial patterns depends on position within a peat landform, with these differences attributed to the ecohydrological setting. In turn, the ecohydrological setting, with different water table depths, nutrient availability, and species composition, influences the strength and direction of feedback mechanisms at the microform scale. Our data support the prediction of a positive feedback between plant productivity and acrotelm thickness for peat accumulation and hummock growth and that this may be enhanced by water ponding on slopes to form ridge–pool tracks. We did not find evidence to support the proposed feedback among evapotranspiration-driven transport of water and nutrients for the development of hummocks. Our results suggest a combination of mechanisms operating at various temporal and spatial scales is associated with the development of surface patterns in northern peatlands.

Reconstruction of atmospheric lead and heavy metal pollution in the Otrębowskie Brzegi peatland (S Poland)

We reconstruct palaeoenvironmental changes since the Late Holocene in the Orava–Nowy Targ Basin, with an emphasis on anthropogenic influence (Walker et al., 2018). This reconstruction employs multiproxy analyses of the Otrebowskie Brzegi poor fen. We combined radiocarbon and 210 Pb dating with elemental geochemistry, stable lead isotopes, and palaeobotanical analyses. The core we investigated covers a period from 4200 ± 100 BC to the present, with a peat accumulation rate varying between 0.001 and 0.243 cm y –1 . Heavy metal concentrations, Pb isotopic ratios, and a palynological analysis revealed a significant impact of human activities in the past. The highest concentration and accumulation rate of Pb, were found around 1950 AD. The 206 Pb/ 207 Pb quotient ranged between 1.168 and 1.223, with average value around 1.198. Most of the interpretation was based on Pb and its stable isotopes; however, other elements were also important indicators of natural and anthropogenic environmental changes. Our results revealed similarities between the geochemical composition of the peatland studied and other peatlands from the Orava–Nowy Targ Basin.

Alleviation of Plant Stress Precedes Termination of Rich Fen Stages in Peat Profiles of Lowland Mires

Mesotrophic rich fens, that is, groundwater-fed mires, may be long-lasting, as well as transient ecosystems, displaced in time by poor fens, bogs, forests or eutrophic reeds. We hypothesized that fen stability is controlled by plant stress caused by waterlogging with calcium-rich and nutrient-poor groundwater, which limits expansion of hummock mosses, tussock sedges and trees. We analysed 32 European Holocene macrofossil profiles of rich fens using plant functional traits (PFTs) which indicate the level of plant stress in the environment: canopy height, clonal spread, diaspore mass, specific leaf area, leaf dry matter content, Ellenberg moisture value, hummock-forming ability, mycorrhizal status and plant functional groups. Six PFTs, which formed long-term significant trends during mire development, were compiled as rich fen stress indicator (RFSI). We found that RFSI values at the start of fen development were correlated with the thickness of subsequently accumulated rich fen peat. RFSI declined in fens approaching change into another mire type, regardless whether it was shifting into bog, forest or eutrophic reeds. RFSI remained comparatively high and stable in three rich fens, which have not terminated naturally until present times. By applying PFT analysis to macrofossil data, we demonstrated that fens may undergo a gradual autogenic process, which lowers the ecosystem’s resistance and enhances shifts to other mire types. Long-lasting rich fens, documented by deep peat deposits, are rare. Because autogenic processes tend to alleviate stress in fens, high levels of stress are needed at initial stages of rich fen development to enable its long persistence and continuous peat accumulation.