Search Results (11)

Sustainable soil resource management requires detailed knowledge of soil pollution sources and their share in total pollution level. Spatial pollution caused by the total cumulative atmospheric deposition remains largely unknown, as the biggest pollutant emissions occurred in XIX/XX centuries. The use of ombrotrophic peatlands that are specific isolated ecosystems fed only through atmospheric deposition may serve as its natural archives. Accumulation of Cd and Pb from atmospheric deposition in undisturbed soil layers in relation to their total deposited cumulative loads recorded in the ombrotrophic peat bog was exemplified in the Izera Mountains, an area historically heavily affected with the transboundary long-range transmission of pollutants from Germany, the Czech Republic, and Poland. Balance of deposited Cd and Pb loads in soil in relation to the total cumulative deposition determined from peat records showed 30% depletion of Cd load in the soil profile due to washout of mobile phases, while that of Pb practically did not decline. The deposited element accumulation and release/depletion in undisturbed soil profiles can thus be quantified in relation to the total cumulative load of atmospheric deposition. This shows a new prospective application of peat bog records as monitors of total cumulative loads of trace elements supplied to soils from atmospheric deposition. Full article

This study examines a boreal peatland (the Sagnes peatland, Fanay, Limousin, France) with a depth of 1 m. This peatland is currently in the late stages of organic deposition, as evidenced by the growth of Carex species, along with Sphagnum mosses, in the uppermost level. To gain molecular insights, we conducted an analysis of the lignin and polyphenolic counterparts using HMDS (hexamethyldisilazane) thermochemolysis, enabling the identification of lignin degradation proxies. The goal was to develop characteristic indicators for the state of lignin degradation based on the relative distribution of lignin phenols, measured by gas chromatography coupled with mass spectrometry (GC-MS) after the HMDS thermochemolysis. For that purpose, the singular contribution of the 11 aromatic moieties yielded, along with SGC (sum of lignin moieties) and the most lignin degradation proxies, were applied. It has been shown that HMDS thermochemolysis exhibited the capacity to reveal oxidized and degraded lignin fractions, following the increasing trend yielded for most moieties and SGC proxy, in the mesotelm and catotelm layers. In addition, the C/G (Cinnamyl/Guaiacyl) and S/G (Syringyl/Guaiacyl) ratios showed their highest input in the upper half of the core. This bias in the aforementioned ratios could indicate that HMDS thermochemolysis is to be applied for geological samples, where low G-compounds exist. For the sake of validating HMDS thermochemolysis’ application, Principal Component Analysis (PCA) was then applied to the molecular fingerprint. For ratios and proxies of aromatic moieties of HMDS thermochemolysis, the PCA approach exhibited a higher contribution (79%). This indicates the efficiency of these ratios in describing the molecular fingerprint of peat depth records. In addition, a higher separation between the contributions of the investigated variables (molecular proxies) along the first two PCs was noticed. In other words, the variables that showed a high contribution towards PC₁ exhibited a low contribution towards PC₂, and vice versa. These findings indicate the high reliance of applying the ratios and proxies of HMDS thermochemolysis. Full article

Peatland hydrology plays an important role in preserving or changing the record in any consideration of past atmospheric deposition records in peat bogs. The Šijec bog, located on the Pokljuka plateau in Slovenia, is one of the largest ombrotrophic peatlands. We sampled the surface pools, pore water, drainage from the peatland, and karst streams not connected to the peatland. Additionally, we sampled the precipitation, as ombrotrophic peatlands receive mineral matter solely from the atmosphere. The results of the evaluation of the chemical and isotopic composition indicated different origins of dissolved mineral matter in different water types. The components originating from the bedrock and surrounding soils (Ca, Mg, Al, Si, Sr) predominated in the streams. The chemical composition of the peatland drainage water revealed the significant removal of major components from the peatland, particularly elements like Al, Fe, and REE, and metals that are readily dissolved in an acidic environment or mobile in their reduced state. Despite their solubility, concentrations of metals (As, Cr, Cu, Fe, Ni, Pb, Ti) and REE in surface pools remained higher than in the drainage due to incomplete elimination from the peatland. The composition of pore water reflects variations among the W and E parts of the peatland, indicating a heterogenous hydrological structure with different dynamics, such as an additional source of water at approximately 90 cm depth in the NW part. The chemical composition and isotope signature (¹⁸O and ²H) of pore water additionally indicated a heterogeneous recharge with residence times of less than a year. The overall analysis indicated a predominantly ombrotrophic type and a small part in the NW area of the peatland as a minerotrophic type of peat. Full article

Ombrotrophic suboceanic bogs are distinguished by a high diversity of complex microlandscapes within the bog massif. Each complex microlandscape is a separate intrabog ecosystem with a specific set of parameters and relationships. This study aims to assess the specifics of the characteristics and parameters of the complex microlandscapes as part of an ombrotrophic suboceanic Sphagnum bog and as stages of bog morphogenesis, and to establish the internal relationships and their relationship with external environmental factors. A comprehensive multidisciplinary approach was used to assess the functioning of the complex microlandscapes. It was found that the relationship with the air temperature is closer than with the bog water table dynamics. It was shown that the morphometric parameters of perennial dwarf shrubs can serve as indicators of the stages of development of bogs. The processes of the self-regulation of complex microlandscapes are weakened with the age of the complex microlandscape, as evidenced by an increase in the amplitude of temperature fluctuations and the level of bog waters, as well as the key physicochemical parameters of the peat deposit. This leads to a gradual, slow reorientation of the physicochemical processes occurring in the deposit, from the deposition of organic matter to the decomposition of peat biomass. Full article

West Siberian mires covering more than 50% of area in the subarctic are still poorly investigated despite their thick peat sediments suitable for paleogeographic research of past long-term landscape and climatic changes. In this research, a combination of paleoecological methods were used, including the analysis of pollen, spores, diatoms, NPPs, and macrofossils, the measurement of peat humification, and quantitative paleoclimate reconstruction. This multi-proxy approach was applied to study a palsa bog (frost peat heave mound) located in the north of western Siberia on the border of the northern taiga and forest–tundra (65°18′56″ N, 72°52′27″ E). Chronology is based on 21 radiocarbon dates, which were calibrated in CLAM. Studies have shown that sediments of palsa bog Nadym of a 1050 cm thickness were formed both in the Holocene and earlier periods of the Quaternary. Radiocarbon dating worked well for peat sequences (610 cm thick), but failed for underlying lacustrine and mineral sediments (440 cm thick). Numerous remains of salt-water diatoms and exotic Neogene pollen were found in the lacustrine sediments (650–850 cm). The oldest sediments (850–1050 cm) have signs of secondary epicryogenic diagenesis in the form of cryogenic iron-enriched granules. Both lacustrine and bottom sediments contain abundant coniferous pollen. At the same time, spore–pollen complexes dated to the Last Glacial Age were not found in low sediments because of failed dates. To explain this, the authors turn to the hypothesis of glyacioisostatic compensation, according to which the study area was uplifted during the Last Glacial Age and the ancient deposits underwent secondary diagenesis in subaerial conditions. Holocene lacustrine sedimentation began to form about 9800 cal. a BP. These lacustrine sediments turned out to be enriched in redeposited Neogene pollen and diatoms. It was interpreted as an influence of excess humid climate in combination with geological subsidence of landscape in the study area during the Early Holocene. This caused lake formation and introduction of exotic microfossils via surface run-off from higher-relief areas in the catchment. Syngenetic sedimentation in the Nadym section is associated only with peat-mire deposits covering the last 8400 cal. a BP. For this time, the dynamic of vegetation cover and quantitative changes in paleoclimate were reconstructed using spore–pollen, macrofossil, humus, and NPP data as well as the information–statistical method of V.A. Klimanov. The spore–pollen analysis revealed four main phases in the development of vegetation cover: 1. Spruce–birch forests with open meadows and lakes (8400–7600 cal. a BP); 2. Dominance of spruce forests and thawed eutrophic (minerotrophic) mires (7600 to 6500 cal. a BP); 3. Coniferous–birch forests and thawed mesotrophic mires (6500 to 4500 cal. a BP); 4. Birch–pine forests and oligotrophic (ombrotrophic) bogs with permafrost mounds—palsa bogs (approx. the last 4500 years). Quantitative reconstructions of paleoclimate based on pollen data show that in most cases the periods of a sharp decrease in mean January and mean July temperatures coincided with episodes of low solar activity. The assumption was made about the determining influence of solar activity on the formation of permafrost in the soils and mires of the study area. Sun minima caused permafrost formation in the mire periodically since 8400 cal. a BP in study peatland, but complete freezing of the peat mire and formation of the palsa bog occurred at c. 2800 cal. a BP. Full article

We studied the peat stratigraphy of the Mukhrino peatland, which is a typical ombrotrophic bog for the Middle Taiga zone of Western Siberia, to gain insights into its history, hydrology, and carbon fluxes. For the first time in Western Siberia, seven cores were collected from locations that were chosen to represent the typical present-day vegetation types, and this was performed for the dating of the separated dissolved (DOC) and particulate organic carbon (POC) fractions, which were determined using the Accelerator Mass Spectrometer (AMS) radiocarbon (${}^{14}$C) method. The oldest peat was found at the bottoms of an underlying lake (10,053 cal. year BP) and an ancient riverbed (10,989 cal. year BP). For the whole history of the peatland, the average peat accumulation rate was estimated to be 0.067 ± 0.018 cm yr${}^{-1}$ (ranging from 0.013 to 0.332 cm yr${}^{-1}$), and the carbon accumulation rate was 38.56 ± 12.21 g m${}^{-2}$ yr${}^{-1}$ (ranging from 28.46 to 57.91 g m${}^{-2}$ yr${}^{-1}$). There were clear age differences between the separated samples of the DOC and POC. The DOC was older than the POC in the uppermost 150 cm of the peat deposit and younger in the deeper layers. The difference in age increased with depth, reaching 2000–3000 years at the bottom of the peat deposit (depth of 430–530 cm). Following the consideration of a range of factors that could potentially cause the dating discrepancy, we hypothesised that the DOC continuously moves down into the mineral sediment beneath the peat, as an additional carbon flux that results in the mixing of younger and older carbon. On this basis, we estimated the apparent rate of the DOC’s downward movement and the associated rate of carbon loss. The first estimate of the average rate of the DOC’s downward movement in Western Siberia was 0.047 ± 0.019 cm yr${}^{-1}$, causing carbon loss in the range of 28–404 mg m${}^{-2}$ yr${}^{-1}$. Full article

Radiocarbon-dated peat cores collected from an ombrotrophic bog in southern Estonia record shifting environmental conditions and carbon accumulation rates in northern Europe during the late Holocene. Modern observations indicate that the water balance of the peatland is highly influenced by changes in relative humidity, followed by temperature and precipitation. The modern δ¹⁸O and δ²H values of surface water suggest that the groundwater is an integration of several months of precipitation. There also appears to be little or no direct influence of surface evaporation on the water within the bog, suggesting that water loss is preferentially through transpiration and sub-surface flow. Bulk peat δ¹³C values exhibit a trend of higher values through the late Holocene, suggesting a pattern of overall increased surface wetness. The δ¹⁵N values were low from ~4130 to 3645 cal yr BP, suggesting drier conditions, followed by intermediate values until ~2995 cal yr BP. The δ¹⁵N values decrease again from ~2995 to 2470 cal yr BP, suggesting a return to drier conditions, followed by intermediate values until ~955 cal yr BP. The δ¹⁵N values were high, suggesting wetter conditions from ~955 to 250 cal yr BP, followed by intermediate values through the modern. Carbon accumulation rates were low to intermediate from ~4200 to 2470 cal yr BP, followed by intermediate-to-high values until ~1645 cal yr BP. Carbon accumulation rates were then low until ~585 cal yr BP, followed by intermediate values through the modern. The geochemical data, combined with observed changes in peat composition and regional proxies of temperature and water table fluctuations through the late Holocene, suggest that carbon accumulation rates were relatively low under dry and warm conditions, whereas accumulation was generally higher (up to ~80 g C m⁻² yr⁻¹) when the climate was wetter and/or colder. These findings further suggest that future environmental changes affecting the regional water balance and temperature will impact the potential for northern peatlands to capture and store carbon. Full article

Microbial communities throughout the 6.5 m depth profile of a boreal ombrotrophic bog were characterized using amplicon sequencing of archaeal, fungal, and bacterial marker genes. Microbial populations and their relationship to oxic and anoxic batch sorption of radionuclides (using radioactive tracers of I, Se, Cs, Ni, and Ag) and the prevailing metal concentrations in the natural bog was investigated. The majority of the detected archaea belonged to the Crenarchaeota, Halobacterota, and Thermoplasmatota, whereas the fungal communities consisted of Ascomycota, Basidiomycota, and unclassified fungi. The bacterial communities consisted mostly of Acidobacteriota, Proteobacteria, and Chloroflexi. The occurrence of several microbial genera were found to statistically significantly correlate with metal concentrations as well as with Se, Cs, I, and Ag batch sorption data. We suggest that the metal concentrations of peat, gyttja, and clay layers affect the composition of the microbial populations in these nutrient-low conditions and that particularly parts of the bacterial and archaeal communities tolerate high concentrations of potentially toxic metals and may concurrently contribute to the total retention of metals and radionuclides in this ombrotrophic environment. In addition, the varying metal concentrations together with chemical, mineralogical, and physical factors may contribute to the shape of the total archaeal and bacterial populations and most probably shifts the populations for more metal resistant genera. Full article

Peatlands are remarkable for their specific biodiversity, crucial role in carbon cycling and climate change. Their deposits preserve organism remains that can be used to reconstruct long-term ecosystem and environmental changes as well as human impact in the prehistorical and historical past. This study presents a new multi-proxy reconstruction of the peatland and vegetation development investigating climate dynamics and human impact at the border between mixed and boreal forests in the Valdai Uplands (the East European Plain, Russia) during most of the Holocene. We performed plant macrofossil, pollen, testate amoeba, Cladocera, diatom, peat humification, loss on ignition, carbon and nitrogen content, δ¹³C and δ¹⁵N analyses supported by radiocarbon dating of the peat deposits from the Krivetskiy Mokh mire. The results of the study indicate that the wetland ecosystem underwent a classic hydroserial succession from a lake (8300 BC–900 BC) terrestrialized through a fen (900 BC–630 AD) to an ombrotrophic bog (630 AD–until present) and responded to climate changes documented over the Holocene. Each stage was associated with clear changes in local diversity of organisms responding mostly to autogenic successional changes during the lake stage and to allogenic factors at the fen-bog stage. The latter can be related to increased human impact and greater sensitivity of peatland ecosystems to external, especially climatic, drivers as compared to lakes. Full article

We studied twelve late Holocene organic deposits in West-Frisia, The Netherlands. Pollen, spores, non-pollen palynomorphs, mosses, other botanical macrofossils and insect remains were recorded for reconstructions of changing environmental conditions. Eastern West-Frisia was a cultivated landscape during the Bronze Age, but it became a freshwater wetland in the Late Bronze Age. In most of our sites, radiocarbon dates show that time transgressive inundation of soils preceded the climate shift at 850 cal BC for several centuries. We suggest that solar forcing of climate change may have delivered the final push to the inundation and depopulation of West-Frisia, which had already commenced several centuries before, due to sealevel rise. We did not find evidence for significant Bronze Age tree growth in West-Frisia before the inundations. Vegetation successions in the new wetlands developed from shallow mineral-rich freshwater to rich-fen vegetation. Subsequently poor fen vegetation with birch and pine developed, and the natural succession led to ombrotrophic raised bog vegetation. Complete successions from shallow, mineral-rich lakes to raised bog lasted between 1000 and 1500 calendar years. We hypothesize that medieval drainage and reclamation became possible only when the mires of West-Frisia had reached the raised bog stage. Reclamation of raised bogs by medieval farmers (drainage, eutrophication, peat digging) caused compaction, oxidation and loss of the upper part of the peat deposit. Seeds of salt-tolerant and salt-demanding plant species indicate that the medieval sites were inundated during storm surges with brackish or salt water, which triggered the farmers to build artificial mounds and, later, dikes. Under mounds and dikes, peat deposits remained protected against further decay. With our data we deliver a long-term perspective on contemporary ecosystem dynamics of freshwater wetlands, relevant for nature conservation and future climate change. Full article

Large areas in Northern Russia are covered by extensive mires, which represent a complex mosaic of ombrotrophic raised bogs, minerotrophic and eutrophic fens, all in a close proximity to each other. In this paper, we compared microbial diversity patterns in the surface peat layers of the neighbouring raised bogs and eutrophic fens that are located within two geographically remote mire sites in Vologda region using 16S rRNA gene sequencing. Regardless of location, the microbial communities in raised bogs were highly similar to each other but were clearly distinct from those in eutrophic fens. Bogs were dominated by the Acidobacteria (30%–40% of total 16S rRNA gene reads), which belong to the orders Acidobacteriales and Bryobacterales. Other bog-specific bacteria included the Phycisphaera-like group WD2101 and the families Isosphaeraceae and Gemmataceae of the Planctomycetes, orders Opitutales and Pedosphaerales of the Verrucomicrobia and a particular group of alphaproteobacteria within the Rhizobiales. In contrast, fens hosted Anaerolineae-affiliated Chloroflexi, Vicinamibacteria- and Blastocatellia-affiliated Acidobacteria, Rokubacteria, uncultivated group OM190 of the Planctomycetes and several groups of betaproteobacteria. The Patescibacteria were detected in both types of wetlands but their relative abundance was higher in fens. A number of key parameters that define the distribution of particular bacterial groups in mires were identified. Full article