Of particular interest in the north of Western Siberia are frozen flat-mound bogs. Being formed in a transitional climatic zone, on the southern front of the permafrost zone, these frozen peatlands ...may turn out to be highly reactive upon thawing and deliver high amounts of solutes to the hydrological network. A detailed study of a flat-mound bog was carried out in a key area of about 3 hectares (Purovsky district, Yamalo-Nenets Autonomous Okrug). The soil-ecological conditions of the site are described, as well as the effect of spatial heterogeneity on the composition and properties of soils. Using topographic mapping and photogrammetry, it was identified that the bog surface is characterized by distinct microtopography (mounds-hollows-thermokarst subsidence with a percentage areas ratio of 49:30:21, respectively). Small-scale variations in ecohydrological settings, microtopography, and vegetation affect the distribution of nutrients, organic carbon in soils, and DOC (dissolved organic carbon) in bog waters. The main soil types are Dystric Hemic Cryic Histosols and Dystric Hemic Histosols (Gelic) found on mounds and in subsidence, respectively. If the peat thickness decreases to 40– 60 cm, then Spodic Histic Turbic Cryosols (Albic, Arenic) and Histic Turbic Cryosols (Albic, Arenic) form. In hollows and fens, Dystric Epifibric Histosols, Spodic Histic Turbic Cryosols (Arenic), and Gleyic Histic Entic Podzols (Turbic) are the most common. The proportion of soils with frozen peat is no more than 20% of the area of the key site and permafrost lies deeper, in the underlying rocks. It was found that carbon stocks within the key area vary from 31.1 to 91.3 kg/m2. The maximum values are observed in transit subsidences/hollows between mounds, where water is discharged. Concentrations of macro-microelements in bog waters vary depending on microform types. For some elements (e.g., DOC, Fe, Al, B, Si, Ti, V, Rb, Sb, Cs, REEs (rare earth elements), Pb, Th, U), they are approximately equal or 1.5–2 higher on the mounds. The export of DOC and other elements in permafrost areas is primarily controlled by the residence time of water and movement ways along the profile. In addition to this, the physicochemical properties of peat and biomass, which are also higher on mounds, influence the distribution and accumulation of nutrients.
Mountain ombrotrophic peatlands in Central Europe are an important stock of transboundary contamination both of natural and anthropogenic origin. The Śnieżka Mountain (West Sudetes) forms a ...significant orographic barrier and receives aerosols from broadly-recognized anthropogenic sources (production and use of stainless steel, processing of uranium, coal combustion, nuclear weapon tests, and Chernobyl accident). The main objective of the study was to assess the pattern of distribution and origin of trace elements and to distinguish the long-range transport vs. local signals in two 210Pb and 14C – dated peat cores from the highest summit of the Karkonosze (West Sudetes) spanning the last 280 years.
Maximum values and accumulations of almost all investigated elements (Pb, Zn, Cu, Ni, Cr, Ti, Al, U, Sc, and REE) were identified around the 1970s. The analysis of peat using scanning electron microscopy (SEM) confirmed the occurrence of spheroidal aluminosilicate fly ash particles (SAP) in the topmost 40 cm (from AD 1938) together with a maximum of mullite (3Al2O3·2SiO2), an anthropogenic marker originating from coal-based power plants. The overall 206Pb/207Pb signature ranges from 1.160 to 1.173, indicating a predominant contribution of anthropogenic Pb. Human activities promote the release of mobile 234U, due to the weaker bonds to mineral structure, and cause the radiogenic disequilibrium between 238U and its daughter 234U.
•1.The Sudetes receive broadly-recognized sources of aerosols.•Intense use of coal contribute to the emission of Pb, U and Sc, Al, Ti as well REE.•Cr and Ni release from stainless steel factories is evidenced.•4.The disequilibrium of 234U/238U is attributed to human activity.
Peatlands are major terrestrial stores of carbon (C) of importance to the global climate system. Recent studies have made progress in understanding the climatic controls on the C cycle; however, ...important interactions between volcanic deposition and peatland C stores remain to be addressed. This study uses a 3000-year peatland record from northern Japan to examine the interactions between carbon accumulation, vegetation community succession and volcanic ash deposition. Plant macrofossil and testate amoebae records are presented alongside records of total organic carbon, nitrogen and phosphorous. Age–depth models are developed using a Bayesian approach, with seven AMS radiocarbon dates and two identified historical tephras from Baitoushan (AD 969 (981 cal. BP)), and Hokkaido-Komagatake (AD 1640 (310 cal. BP)) volcanoes. Results show that moderate to high tephra loading can shift peatland plant communities from Sphagnum to monocotyledon domination. This vegetation change is associated with increased peat humification and reduced carbon accumulation. Where tephra deposition and reworking has occurred, the apparent rate of carbon accumulation can be halved while high tephra loading of the mire surface is sustained. Sphagnum species vary in their tolerance to tephra deposition. After each ash fall Sphagnum magellanicum disappeared from the plant macrofossil record, whereas Sphagnum papillosum showed apparent continuity of development through the 1856 (94 cal. BP) Ko-c1 tephra. High rates of carbon accumulation (peaking at >100 g m−2 yr−1), 2–3 times faster than the average for northern peatlands, were recorded in the Sphagnum communities that established after the cessation of tephra deposition and reworking from the AD 969 Baitoushan ash fall (B-Tm tephra). This peak in C accumulation was coincident with a radical shift in mire nutrient cycling most probably caused by the interaction of S. magellanicum with leachates from the underlying tephras. The phase of high C accumulation continued for over 300 years, offsetting the initial negative impact of the B-Tm tephra on peatland C accumulation. These results suggest that management for ash-tolerant Sphagnum species could be a highly effective strategy for minimising volcanic disruption to peatland carbon accumulation. The study also shows that consideration of volcanic impacts on peatlands is essential for development of more realistic terrestrial carbon balance models in volcanically active regions.
► Far-travelled volcanic ash can alter bog carbon stores, succession & nutrient cycles. ► Bog carbon accumulation rates are sharply reduced by heavy ash-fall & re-deposition. ► After ash stabilisation high carbon accumulation occurs when bog mosses re-colonise. ► High carbon accumulation follows shifts in bog nutrient cycles from P to N-limitation. ► Net effect of B-Tm ash on bog C stores was positive 100 years after reworking ended.
The nature and cause of the so-called 2.8 kyr BP event have been a subject of much debate. Peat sequences have provided much of the evidence for this event, but the process link between climate and ...peatland response is not well understood. Multiproxy, high-resolution analysis of a core from Bargerveen in the eastern Netherlands based on pollen, non-pollen palynomorphs, testate amoebae and geochemistry identified an abrupt shift from relatively dry to extremely wet conditions. Radiocarbon-based wiggle-match dating (WMD) and biostratigraphy based on the pollen record show that this shift in local hydrology occurred around 2800 cal. yr BP. We interpret an erosional hiatus lasting up to 950 years immediately prior to this, as the effect of a bog burst after excessive rainfall. This phenomenon was not limited to our sampling location but occurred over a large part of the former Bargerveen. Peat at the hiatus contains microfossils that reflect temporary eutrophication as a consequence of local fires and secondary decomposition because of increased drainage after the erosion event. Our data show how detailed multiproxy analyses can elucidate the past response of peatlands to changing climate and suggest that the climatic change in northwest Europe at this time caused major non-linear disruption to these ecosystems.
A recent paper by Miszczak et al. (2020) examines metal contamination of mires in Poland and Norway. The authors conclude that lead (Pb) records in ombrotrophic peatlands cannot be used to ...reconstruct the chronological history of anthropogenic activities due to post-depositional mobility of the metal. We contest this general conclusion which stands in contrast with a significant body of literature demonstrating that Pb is largely immobile in the vast majority of ombrotrophic peatlands. Our aim is to reaffirm the crucial contribution that peat records have made to our knowledge of atmospheric Pb contamination. In addition, we reiterate the necessity of following established protocols to produce reliable records of anthropogenic Pb contamination in environmental archives.
Drainage is a recognised cause of wetland loss worldwide, and New Zealand is no exception. In the last 200 years drainage has reduced the natural extent of wetlands in New Zealand by c. 90%. Avoiding ...further loss is a national priority. Despite recent reform to restrict new drains within 100 m of existing wetlands in New Zealand, little is known about the extent and effect of existing drains in and near wetlands. Using a national layer of wetland extent (Freshwater Ecosystems of New Zealand) we calculated the area of wetlands currently within a zone of potential drain effects in the North and South Islands, by buffering an existing national drain layer by 100 m and 50 m and stratifying these results by peat/non-peat, and wetland type. We show that 7476 ha (c. 3%) of New Zealand wetlands identified in the national FENZ dataset are potentially affected by drainage when intersected with the national drains layer buffered by 100 m. Of these wetlands near drains, 4387 ha were wetlands with high organic matter (peat) that are vulnerable to drainage-induced subsidence and release of greenhouse gases. We then conducted a case study within the Waituna catchment (Southland, New Zealand) to assess if the national drain data is under-estimating the extent of wetland drainage by comparing the area affected by drainage detected using the national drains layer with an algorithm to identify drains from LiDAR. Our catchment case study revealed that our LiDAR method more than tripled the area of wetland near drains suggesting that the existing national drains layer is underestimating wetland drainage extent. We highlight that further work should be undertaken to develop an accurate stocktake of drains near wetlands, given the increasing availability of LiDAR and the ongoing efforts to improve wetland mapping by territorial authorities.
Due to the scarcity of reliable and highly resolved moisture proxies covering much of the Holocene, there has been increased interest in the study of living and subfossil peatland trees sensitive to ...gradual and extreme changes in hydrology, precipitation, and related environmental processes. Peatland development and the associated carbon accumulation, which are strongly influenced by hydrological fluctuations, are also of prime importance as peatlands represent long-term sinks of atmospheric carbon. Improved knowledge of peatland development and soil moisture variability during the Holocene is therefore essential to our understanding of long-term hydroclimate changes, the terrestrial carbon cycle, and to enable more robust predictions of peatland response to future climate changes.
Here, we review the existing mid- to late Holocene peatland tree-ring chronologies that have been used to study climate variability on (sub-)annual to centennial scales with a primary focus on northern Europe. Since the 1970s, absolutely dated tree-ring chronologies covering substantial parts of the Holocene have been developed from excavated remains of oak (Quercus spp.) and pine (Pinus sylvestris L.). The annual tree-ring patterns of these trees are often characterized by periods of depressed growth reflecting annual to decadal hydroclimatic changes. In addition, changes in the spatio-temporal distribution of trees throughout the Holocene are often found to reflect decadal to centennial climate and hydrological changes. Moreover, synchronicity between tree-ring chronologies and tree-population dynamics over larger geographical areas show periods of coherent regional climate forcing, especially during the mid-Holocene.
This review (i) provides an overview of pioneering and recent studies presenting tree-ring chronologies developed from subfossil peatland trees, and (ii) presents recent developments in the fields of dendroecology (i.e. the response of tree growth and changes in vitality as a result of changes in climatic variables) and dendroclimatology (i.e. the reconstruction of climate fluctuations based on tree-ring analyses) in peatland regions. Moreover, we (iii) use long-term climate reconstructions based on alternative proxies for comparison, and (iv) present different ways to analyse tree-ring records to generate novel information on annual to centennial timescales. This analysis is based on an unprecedented network of tree-ring chronologies from Denmark, Finland, Germany, Great Britain, Ireland, Lithuania, the Netherlands, Poland, Sweden, and Canada, as well as a wealth of old and previously (un) published literature from Scandinavia and Germany, which has not been accessible to a wider audience in the past due to inaccessibility or linguistic barriers. Finally, a map of possible hotspots for the assessment of continuous peatland-tree studies is presented, along with suggestions for new research directions in the field.
•We review extensive peatland tree-ring chronologies from northern Europe covering major parts of the Holocene.•Long distance cross-matches (correlograms) and significant positive correlation point to larger-scale climate signals.•Subfossil peatland trees can be used for detailed palaeoclimatic and palaeohydrological reconstructions.•Warm/dry conditions are favourable for peatland tree growth, but may turn peatlands from carbon sinks to carbon sources.
Peatlands represent a globally important carbon store; however, the human exploitation of this ecosystem is increasing both the frequency and severity of fires on drained peatlands. Yet, the ...interactions between the hydrological conditions (ecotopes), the fuel types being burned, the burn severity, and the charring temperatures (pyrolysis intensity) remain poorly understood. Here we present a post-burn assessment of a fire on a lowland raised bog in Co. Offaly, Ireland (All Saints Bog). Three burn severities were identified in the field (light, moderate, and deeply burned), and surface charcoals were taken from 17 sites across all burn severities. Charcoals were classified into two fuel type categories (either ground or aboveground fuel) and the reflectance of each charcoal particle was measured under oil using reflectance microscopy. Charcoal reflectance shows a positive relationship with charring temperature and as such can be used as a temperature proxy to reconstruct minimum charring temperatures after a fire event. Resulting median reflectance values for ground fuels are 1.09 ± 0.32%Romedian, corresponding to estimated minimum charring temperatures of 447°C ± 49°C. In contrast, the median charring temperatures of aboveground fuels were found to be considerably higher, 646°C ± 73°C (3.58 ± 0.77%Romedian). A mixed-effects modeling approach was used to demonstrate that the interaction effects of burn severity, as well as ecotope classes, on the charcoal reflectance is small compared to the main effect of fuel type. Our findings reveal that the different fuel types on raised bogs are capable of charring at different temperatures within the same fire, and that the pyrolysis intensity of the fire on All Saints Bog was primarily driven by the fuel types burning, with only a weak association to the burn severity or ecotope classes.
Peatland areas provide a range of ecosystem services, including biodiversity, carbon storage, clean water, and flood mitigation, but many areas of peatland in the UK have been degraded through human ...land use including drainage. Here, we explore whether remote sensing can be used to monitor peatland resilience to drought. We take resilience to mean the rate at which a system recovers from perturbation; here measured literally as a recovery timescale of a soil surface moisture proxy from drought lowering. Our objectives were (1) to assess the reliability of Sentinel-1 Synthetic Aperture Radar (SAR) backscatter as a proxy for water table depth (WTD); (2) to develop a method using SAR to estimate below-ground (hydrological) resilience of peatlands; and (3) to apply the developed method to different sites and consider the links between resilience and land management. Our inferences of WTD from Sentinel-1 SAR data gave results with an average Pearson's correlation of 0.77 when compared to measured WTD values. The 2018 summer drought was used to assess resilience across three different UK peatland areas (Dartmoor, the Peak District, and the Flow Country) by considering the timescale of the soil moisture proxy recovery. Results show clear areas of lower resilience within all three study sites, which often correspond to areas of high drainage and may be particularly vulnerable to increasing drought severity/events under climate change. This method is applicable to monitoring peatland resilience elsewhere over larger scales, and could be used to target restoration work towards the most vulnerable areas.
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•Many peatlands are degraded, potentially causing low resilience to climate change.•Drought recovery time can be used to assess peatland resilience.•Soil moisture and drought recovery can be estimated from Sentinel-1 SAR data.•Areas of lower resilience are shown to correlate with areas of high drainage.
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