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We evaluated the feasibility of using testate amoebae to infer the quantitative paleohydrology of ombrotrophic mires during their early stages (fen and fen-bog transition) of development. Two transfer functions, one derived from ombrotrophic and the other from minerotrophic mires, were applied to a peat core from an ombrotrophic mire in a taiga region of west Siberia. An ombrotrophic transfer function was applied to the bog stage of mire development. In contrast, ombrotrophic and minerotrophic transfer functions were applied independently to infer water table depth in the fen and fen-bog transition stages. Results of the two approaches for calculating water table depth during the fen and fen-bog transition stages differed by as much as 38 cm for the same peat sample. The main reason for this discrepancy is presence of testate amoeba taxa (e.g. Centropyxis aculeata, Cyclopyxis eurystoma, Cyclopyxis eurystoma v. parvula) in the peat that inhabit both modern ombrotrophic and minerotrophic mires, but differ substantially, in cases by > 20 cm, in terms of their water table depth optima in the ombrotrophic and minerotrophic mire calibration data sets. This difference in inferred water table depth also stems, to a lesser degree, from the fact that the ombrotrophic mire model does not include taxa that inhabited exclusively minerotrophic mires in the fen and fen-bog transition stages. Given these findings, we propose that different models be used for different stages of development, to reconstruct past water table depth in ombrotrophic mires. We recommend use of a model based solely on the ombrotrophic mire data set for the bog stage, and application of a second model based on the minerotrophic mire data set, for the fen and fen-bog transition stages. Application of an ombrotrophic model to the early stages of bog development can yield erroneous paleohydrological reconstructions.

Geochemical shifts triggered by surface runoff and atmospheric fallout in a Chinese peatland were investigated by using Pb, Sr, and Nd, REE and by SEM mineralogical analysis. Motianling peatland (Northeast China) is located at 1670 m a.s.l., near the China–Mongolia border. Based on division of profile into two phases of different trophy, the total ∑REE value determined for the minerotrophic part of the profile (from 62 to 46 cm) varied from 67 to 31 mg·kg−1 and mineralogical analysis revealed the occurrence of weathered volcanic rocks, supported by a high eNd value (−3.26). After the transition from minerotrophic to more ombrotrophic conditions, the peatland became independent of the local bedrock weathering, which was manifested by a much lower concentration of REE (7–20 mg·kg−1) and lower eNd values (−7.37; −8.11). Moreover, PAAS-normalized pattern of REE distribution in the bottom part revealed the highest Eu/Eu* value (1.24), as well as a slight enrichment in Eu. The anthropogenic effect was visible from 1964, during which period the spheroidal aluminosilicate particles (SAP), produced by coal-fired power-plant activity, appeared for the first time, followed by an abrupt decrease in 206Pb/207Pb isotopic signature to 1.167. The dimensions of SAP (~1.5 μm), as well as the time of first appearance, indicated long-range transport. The REE ratios obtained in this study are characteristic of the eolian deposition signature, which is like the Gobi and northern Chinese deserts. The anthropogenic activity was manifested by a slight enrichment in Gd during reduced delivery of natural dust. Both, North Chinese and Asian part of the Russian industry supply anthropogenic dust. Topography, wind direction, and patterns of precipitation, as well as the initial phases of Asian industrial development, are the most important drivers promoting the deposition of chemical elements.

This study of the Kanna calcareous spring fen on Saaremaa, the largest island of Estonia, elucidates its history of fen development and vegetation diversity over the last 9,200 years. Pollen, spores, non-pollen palynomorphs, macrofossils, loss-on-ignition and humification index analyses were carried out to reconstruct fen succession, vegetation development, environmental changes and human impact. Hierarchical clustering, ordination analysis and linear regression were applied to examine the vegetation composition and richness patterns through time and to identify the potential environmental drivers underlying these patterns. Our results suggest reverse mire development from bog to fen, a rare occurrence and contrary to typical mire autogenic succession from groundwater fed to rainwater fed. Kanna developed as a small bog for the first 2,000 years from 9,200 to 7,200 cal yrs bp. Changes to the hydrological regime around 7,200 cal yrs bp, due to a warmer and drier climate and land uplift, caused a change from an ombrotrophic to a minerotrophic environment. Typical spring fen characteristics developed ca. 5,000 cal yrs bp and continued until ca. 400 cal yrs bp, when the fen was fed by calcareous mineral-rich groundwater and reached very high floristic diversity with various calciphilous and relict plant taxa. We conclude that general changes in the Kanna fen succession, vegetation community and diversity are associated with climatic changes. The present high diversity of the fen is a result of a long-term stable fen environment, which may have been even higher in the past. However, the pollen richness has decreased during the last 400 years, possibly due to human or natural factors.

High-resolution plant macrofossil records were examined alongside geochemical analysis (non-destructive X-Ray fluorescence and carbon stable isotopes), pollen, and micro-charcoal data of an ombrotrophic mountain peatland located in the Harz Mountains, central Germany, Europe. We hypothesize that increased deposition of dust and pollutants across the bog surface causes changes in habitat conditions, which in turn lead to shifts in moss-dominated communities. We observe that increases in the abundance of Sphagnum magellanicum macrofossils – a species with a wider ecological range that occurs even in weakly minerotrophic habitats - coincide with increases of pollutant concentrations in the peat; conversely, increases of Sphagnum rubellum and Sphagnum capillifolium populations – indicators of oligotrophic conditions – coincide with decreases of pollutant concentrations. Pristine Sphagnum populations in the studied ombrotrophic bog have thus repeatedly returned to their original oligotrophic state (an autogenic process) following declines in pollutant input. Modern levels of pollutants should be taken into account in peatland restoration efforts, as they exert a strong control on the composition of present day Sphagnum communities. Moreover, Sphagnum angustifolium in paleoecological studies might be considered as an indicator of water level rise. In this study, the presence of S. angustifolium apparently correlates with wetter moisture conditions.

Geochemical records from peatlands are important tools for the interpretation of environmental signals preserved in the peat and the understanding anthropogenic impacts on remote mountain regions. In this paper, six 210Pb-dated peat cores located at 500–1900 m above sea level (asl) in the Changbai Mountains were used to reconstruct the pollution history over the past 150 years in northeastern (NE) China. The cores physicochemical parameters and 10 key chemical elements were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Results from loss on ignition (LOI), total organic carbon (TOC), and lithogenic element (Ti, Fe, and Mn) analysis show that the peatlands (Ch, Yc1 and Jb) over 900 m asl are ombrotrophic and the lower altitude peatlands (Dng, Jc, and Ha) are minerotrophic. There is a decreasing trend of trace element distribution with the altitude, mainly due to the local source input. The content of the magnetic particles and trace elements (Cu, Ni, Pb and Zn) as well as their accumulation rates document 150 years of pollution history in the Changbai Mountain region. There is a significant elevated pattern of the geochemical records after the New China, which might mark the start date of Anthropocene since the 1950s in this region. The peatlands at the lower altitude (i.e., Dng and Ha) record the earliest fingerprints of metal contamination due to the starting period of massive reclaiming and immigrating in the Changbai Mountain region. The major increase of trace elements since the 1980s probably suggests a significant deterioration of the local environment due to the fast industrial and urbanization development after the Reform and Opening up in China.

Microbial-mediated iron (Fe) oxidation and reduction greatly contribute to the biogeochemistry and mineralogy of ecosystems. However, knowledge regarding the composition and distribution patterns of iron redox cycling bacteria in peatlands remains limited. Here, using high-throughput sequencing, we compared biogeographic patterns and assemblies of the iron redox cycling bacterial community between soil and water samples obtained from different types of peatland across four regions in Northeast China. A total of 48 phylotypes were identified as potential iron redox bacteria, which had greater than 97% similarity with Fe(II)-oxidizing bacteria (FeOB) and Fe(III)-reducing bacteria (FeRB). Among them, Rhodoferax, Clostridium, Geothrix, Sideroxydans, Geobacter, Desulfovibrio, and Leptothrix could be used as bioindicators in peatlands for characterizing different hydrological conditions and nutrient demands. Across all samples, bacterial communities associated with iron redox cycling were mainly affected by pH, dissolved organic carbon (DOC), and Fe2+. Distance–decay relationship (DDR) analysis indicated that iron redox cycling bacterial communities in soil, but not in water, were highly correlated with geographic distance. Additionally, null model analysis revealed that stochastic processes substituted deterministic processes from minerotrophic fens to ombrotrophic bogs in soils, whereas deterministic processes were dominant in water. Overall, these observations suggest that bacteria involved in iron redox cycling are widespread in diverse habitats and exhibit distinct patterns of distribution and community assembly mechanisms between soil and water in peatlands.

summary Thorne Waste, S. Yorkshire, is a large raised bog, subject to extensive commercial peat extraction, which retains some re-flooded, revegetated peat cuttings. The composition of the vegetation of some of these cuttings (96 sampled quadrats, each of 25 m2) has been related to a number of environmental variables. Revegetation sequences in the abandoned cuttings (all less than 60 years old and with less than 20 cm peat infill) were established by stratigraphical analyses. In some cuttings a basal layer of ericaceous peat apparently marks temporarily drier conditions preceding deeper inundation. Some former mire species (e.g. Sphagnum imbricatum have not survived the peat-cutting period even on uncut surfaces (baulks) but these have been much drained and burnt. The revegetated cuttings contained species typical of poor-ten (e.g. Carex curta) as well as of ombrotrophic mires (e.g. Andromeda polifolia); chemical analyses indicated weakly minerotrophic peat water. This may favour such species as Sphagnum recurvum. There was no indication of chemical enrichment from inflow from surrounding farmland, from underlying mineral ground or from the clay-lined canals excavated across the bog. Release of cations following drainage and re-flooding may provide some explanation. Only soluble reactive phosphorus (SRP) concentration in peat water samples showed consistent and significant seasonal variation, with the lowest values in summer. There were also only a few consistent differences in water chemistry amongst most of the vegetation units identified by TWINSPAN. Nodum 4 (Eriophorum–Sphagnum) stands (richest in ombrotrophic species) occupied the least minerotrophic conditions. One culling, dominated by Juncus, effuses, had no ombrotrophic species (nodum 6). Water concentrations of Ca2+, Na+, K+ NH4+, SO42 and SRP were significantly larger here than in other cuttings and peat fertility (estimated phytometrically) and K, N and P concentrations in peat extracts were significantly greater than in a Sphagnum-dominated cutting. The J. effuses samples had strong negative loadings on axis 2 of a Principal Components Analysis (PCA) of the Adriatic data; concentrations of NH4+, Na+ and SO42 in the water showed significant negative correlation with axis 2 ordination scores. Seasonal fluctuation of water level was similar in most cuttings (the J. effuses cutting was exceptional) but variation in depth relative to the peat surface (caused by excavation to different depths) was related to floristic variation. PCA axis 1 may reflect a water-table gradient with TWINSPAN noda 2 (Calluna Sphagnum recurvum) and particularly 1 (Pteridium Campylopus) occupying drier conditions than the others. The wetter cuttings (except the J. effusus site) supported most ombrotrophic and poor-fen species. They were not readily segregated into discrete vegetation types and the two TWINSPAN classes (noda 3 and 4) that accommodated them showed much overlap on the PCA ordination. Nodum 4 samples tended to have higher loadings on PCA axis 2 and to be more species-rich than nodum 3 samples. Species-richness was strongly positively correlated with PCA axis 2. This may reflect, in part, stand maturity, vegetation with most species having been disturbed least recently.

Tropical peatlands are globally important carbon reservoirs that play a crucial role in fluxes of atmospheric greenhouse gases. Amazon peatlands are expected to be large source of atmospheric methane (CH4) emissions, however little is understood about the rates of CH4 flux or the microorganisms that mediate it in these environments. Here we studied a mineral nutrient gradient across peatlands in the Pastaza-Marañón Basin, the largest tropical peatland in South America, to describe CH4 fluxes and environmental factors that regulate species assemblages of methanogenic and methanotrophic microorganisms. Peatlands were grouped as minerotrophic, mixed and ombrotrophic categories by their general water source leading to different mineral nutrient content (rich, mixed and poor) quantified by trace elements abundance. Microbial communities clustered dependent on nutrient content (ANOSIM p < 0.001). Higher CH4 flux was associated with minerotrophic communities compared to the other categories. The most dominant methanogens and methanotrophs were represented by Methanobacteriaceae, and Methylocystaceae, respectively. Weighted network analysis demonstrated tight clustering of most methanogen families with minerotrophic-associated microbial families. Populations of Methylocystaceae were present across all peatlands. Null model testing for species assemblage patterns and species rank distributions confirmed non-random aggregations of Methylococcacae methanotroph and methanogen families (p < 0.05). We conclude that in studied amazon peatlands increasing mineral nutrient content provides favorable habitats for Methanobacteriaceae, while Methylocystaceae populations seem to broadly distribute independent of nutrient content.

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%&ndash, 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.

Ombrotrophic bogs are widely used to reconstruct the history of atmospheric metal deposition. Minerotrophic fens are potential archives as well but not much attention has been paid to them. This study examined the accumulation of major and trace elements in a poor fen of Fenghuang Mountain, NE China. Peat cores were dated by 210Pb and 137Cs techniques and elemental analyses were conducted after a two-step sequential digestion with HCl. Results suggest no significant pollution for other trace metals but Pb in Fenghuang Mountain area. Atmospheric soil dust flux (ASD) was calculated from the Ti content in the peat, and its decreasing trend over the last 60 years agrees with the East Asian winter monsoon (EAWM) shift, which suggests that ASD could be a potential climatic proxy for the EAWM variability in the region.

It is well established that in ombrotrophic bogs, water-table depth (WTD) is the primary environmental control on testate amoeba distribution. However, the environmental controls on testate amoebae in minerotrophic fens are less well known and successional change in their assemblages associated with fen-bog peatland development has been scarcely investigated. Here we investigate a peatland space-for-time sequence resulting from postglacial rebound on the west coast of Finland, to assess successional patterns in testate amoeba communities and their relationships with environmental variables during peatland development. Sample sites along a 10-km transect from coast to inland ranged from a recently emerged wet meadow to a mature bog. Environmental variables (e.g., peat thickness, carbon and nitrogen content, pH, WTD and vegetation) were measured alongside testate amoeba samples. Results showed that even though the distribution of testate amoebae was to some extent determined by the succession stage, many taxa had wide WTD and pH ranges. The primary environmental control for many taxa changed along the succession. In conclusion, the ecological constraints on testate amoebae in minerotrophic systems are more complex than in bogs. The detected patterns also complicate the use of testate amoebae as a primary proxy in palaeoecological reconstructions where fen-to-bog shifts occur. (C) 2018 Elsevier GmbH. All rights reserved.

The poor fens of the Laforge region, northeastern Canada, have developed under subarctic conditions. They are characterized by a microtopography of large pools and low, narrow strings. Paleorecords suggest some of these systems were once ombrotrophic and relatively dry. Taking account of their current bioclimatic position, we aimed to explore the possible pathways towards the current wet state, a process referred to as “aqualysis”. We combined paleoecological methods applied to a peat core with conceptual modelling to identify factors that might plausibly explain aqualysis. Reconstructions showed the Abeille peatland became minerotrophic with high water tables between 2400 and 2100 cal yr BP. Conceptual modelling, supported by simulations using the numerical DigiBog model, allowed us to identify the effects of cooling and increased precipitation on productivity, decay, peat hydraulic conductivity and vertical peat accumulation. Both cooling and increased precipitation were required for aqualysis to occur and for wet surface conditions to persist to the present day. Increased recharge from the catchment, which also restricted drainage from the peatland center laterally, was likely critical for the development of minerotrophic conditions. The scenario of cooling and wetting in these peatlands is supported by available paleoclimate records for eastern Canada.

Typically, restoration goals target a point in history, i.e., pre-human influence state, however, ecosystems are dynamic and restoration goals must consider the potential evolution of the system, along with primary causes of landscape degradation and the resultant resilience. Using the Everglades as a case study, known disturbances were linked to biogeochemical and vegetation patterns to compare the divergence of the anthropogenically impacted landscape from that expected during natural peatland evolution. Specifically, landscape soil biogeochemistry of ~ 1100 sites was examined in context of hydroperiod, spatial and temporal trends in water quality from the 1940′s through present, elevation, and vegetation communities. This provided a link between carbon (C) accumulation and the influence of anthropogenic alterations. The network of canals created to manage water resulted in a greater ratio of surface water to rainfall contribution to the water budget, restored connectivity of groundwater to surface water, and facilitated overdrainage and mineral and nutrient enrichment of the ecosystem, causing multiple regime shifts and evidence of C loss. This study suggests that restoration can promote the accumulation of minerotrophic peats, but it is difficult to recreate the trajectory towards the ombrotrophic peatland, one of the end members and most C rich portions of the ecosystem, given changes in source waters and connectivity. In addition, a comparison with the literature and paleoecological data confirmed that while phosphorus (P) and C accumulation are positively related, even relatively small increases in P content reduced the proportional C content of peat soils. Overall, this study highlights the need to consider the potential natural trajectories of landscape development, the multiple coexisting resultant regimes, and the importance of soil biogeochemical properties when establishing and prioritizing restoration goals. Given the resilience and feedback loops of the anthropogenically impacted areas, active management of these areas may be necessary if we are to restore the vegetation community composition and biogeochemical characteristics to those of natural regimes, however, some legacy effects will constrain future restoration efforts. This article is protected by copyright. All rights reserved.

The moss layer transfer technique removes the top layer of vegetation from donor sites as a method to transfer propagules and restore degraded or reclaimed peatlands. As this technique is new, little is known about the impacts of moss layer transfer on vegetation and carbon fluxes following harvest. We monitored growing season carbon dioxide (CO2) and methane (CH4) fluxes as well as plant communities at donor sites and neighbouring natural peatland sites in an ombrotrophic bog and minerotrophic fen in Alberta, Canada from which material was harvested between 1 and 6 years prior to the study. Plant recovery at all donor sites was rapid with an average of 72% total plant cover one growing season after harvest at the fen and an average of 87% total plant cover two growing seasons after harvest at the bog. Moss cover also returned, averaging 84% 6 years after harvest at the bog. The majority of natural peatlands in western Canada are treed and tree recruitment at the donor sites was limited. Methane emissions were higher from donor sites compared to natural sites due to the high water table and greater sedge cover. Carbon budgets suggested that the donor fen and bog sites released higher CO2 and CH4 over the growing season compared to adjacent natural sites. However, vegetation re-establishment on donor sites was rapid, and it is possible that these sites will return to their original carbon-cycle functioning after disturbance, suggesting that donor sites may recover naturally without implementing management strategies.

Peatlands are globally important ecosystems in terms of biodiversity, hydrology, and for the role they play in the carbon cycle. They store approximately one‐third of the carbon contained in the terrestrial biosphere, whilst covering only approximately 3% of the land and freshwater surface. Tropical peatlands represent an important component of this carbon store and can be found in Asia, Africa, South and Central America. However, tropical peatlands are also under severe threat of destruction from human activities including deforestation, agricultural expansion and resource exploitation. In South America, the Pastaza–Marañon foreland basin (PMFB) in NW Peru represents the most carbon dense landscape in Amazonia due to an abundance of peatlands, including nutrient‐poor ombrotrophic peat domes and river‐influenced minerotrophic swamps. The Aucayacu peatland in the PMFB is a nutrient‐poor peat dome and represents the oldest peatland yet reported in Amazonia. It is a relatively large peatland—it is estimated that Aucayacu has maximum dimensions of 33 km (NW‐SE) by 15 km (NE‐SW) (Fig. 1). The flora of the site is characterized by stunted vegetation due to low nutrient status, known as ‘pole’ and ‘dwarf’ forest, which at Aucayacu grows above a patchy understory of grasses and ferns (Fig. 2). Recent research has shown that Aucayacu has laid down peat up to 7.5 m deep in ∼ 8900 years.

In contrast to the pervasive occurrence of denitrification in soils, anammox (anaerobic ammonium oxidation) is a spatially restricted process that depends on specific ecological conditions. To identify the factors that constrain the distribution and activity of anammox bacteria in terrestrial environments, we investigated four different soil types along a catena with opposing ecological gradients of nitrogen and water content, from an amended pasture to an ombrotrophic bog. Anammox was detected by polymerase chain reaction (PCR) and quantitative PCR (qPCR) only in the nitrophilic wet meadow and the minerotrophic fen, in soil sections remaining water-saturated for most of the year and whose interstitial water contained inorganic nitrogen. Contrastingly, aerobic ammonia oxidizing microorganisms were present in all examined samples and outnumbered anammox bacteria usually by at least one order of magnitude. 16S rRNA gene sequencing revealed a relatively high diversity of anammox bacteria with one Ca. Brocadia cluster. Three additional clusters could not be affiliated to known anammox genera, but have been previously detected in other soil systems. Soil incubations using 15N-labeled substrates revealed that anammox processes contributed about

Peatlands are wetland ecosystems where net primary production exceeds organic matter decomposition. They are characterized by a near-surface water table controlled by a combination of internal and external processes, influenced by short-term meteorological and long-term climate variations among other factors. Site-specific conditions, such as peat hydrodynamic properties, surface vegetation patterns, and hydrogeological setting also substantially influence water table dynamics. The objective of this work was to characterize the influence of hydrogeological setting and meteorological conditions on water table depths (WTD) and on fluctuations therein in seven ombrotrophic peatlands in or near the St. Lawrence Lowlands (southern Quebec, Canada). Up-gradient, mid-gradient, and down-gradient locations were monitored in the seven peatlands, using dipwells with hourly WTD recordings. WTD was also monitored in the marginal minerotrophic zone found in three of the seven peatlands. Additionally, heads in the outflow (i.e., receiving diffused water from the peatland) and inflow (i.e., providing diffused water to the peatland) zones within the adjacent mineral deposits were monitored in seven and three peatlands respectively, using piezometers with hourly hydraulic head recordings. Hydraulic conductivities for the outflow zones ranged between 1.4*10−7 and 8.5*10−3 cm/s, whereas those of the inflow zones ranged between 5.6*10−7 and 3.9*10−6 cm/s. Evapotranspiration was shown to be the dominant factor controlling monthly cumulative water table decreases (MCD), while precipitation dominated the monthly cumulative water table increases (MCI). A strong correlation was found between mean peatland WTD and outflow zone hydraulic conductivity. Peatlands that were identified as being strongly connected with the adjacent mineral deposits in a diffuse underground outflow zone showed the greatest variations in water storage. This study highlights the importance of the connection between peatlands and adjacent mineral deposits in controlling WTD, as found for those located in the St. Lawrence Lowlands. The results show that water table fluctuations are strongly controlled by meteorological conditions, and that hydrogeological setting exerts a strong control on MCI and MCD. Moreover, this work shows that WTD in ombrotrophic peatlands is influenced by the hydraulic conductivity of the outflow zones, and confirms that aquifer – peatland connectivity influences peatland water storage variations, and therefore peatland vulnerability to disturbances in aquifer groundwater levels. Keywords: Peatland, Aquifer, Water table depth, Water table fluctuation, Hydrogeological setting, Meteorological conditions, Climate change, Vulnerability

We measured pH, cations, nutrients, and total organic carbon (TOC) over 3 years to examine weekly to monthly variability in porewater chemistry depth profiles (0–3.0 m) in an ombrotrophic bog in Minnesota, USA. We also compared temporal variation at one location to spatial variation in depth profiles at 16 locations across the bog. Most solutes exhibited large gradients with depth. pH increased by two units and calcium concentrations increased over 20 fold with depth, and may reflect peatland development from minerotrophic to ombrotrophic conditions. Ammonium concentrations increased almost 20 fold and TOC concentrations decreased by half with depth, and these patterns likely reflect mineralization of peat or decomposition of TOC. There was also considerable temporal variation in the porewater chemistry depth profiles. Ammonium, soluble reactive phosphorus, and potassium showed greater temporal variation in near-surface porewater, while pH, calcium, and TOC varied more at depth. This variation demonstrates that deep peat porewater chemistry is not static. Lastly, temporal variation in solute chemistry depth profiles was greater than spatial variation in several instances, especially in shallow porewaters. Characterizing both temporal and spatial variability is necessary to ensure representative sampling in peatlands, especially when calculating solute pools and fluxes and parameterizing process-based models.

Sufficiency of potassium (K) is one of the biggest concerns for forestry in boreal peatlands, since the rooting zone stores of K in thick peat soils are generally small and significant proportion of the K in ecosystem is bound in stand biomass. Increased demand for bioenergy may lead to intensified harvesting also in such forests. There is thus an urgent need to study the significance of the nutrients in harvest residues for the next-generation forest productivity. The specific questions in peatland forests are whether the harvest residues are an important source of K to the restock or whether the K in harvest residues is lost by leaching. We quantified K losses from drained peatland forests following management by clear-felling with stem-only harvesting (SOH), whole-tree harvesting (WTH) and whole-tree harvesting plus stump harvesting (WTHS). Calibration period – control area method and mixed modelling approach were used to analyze the ditch-outflow K-concentration and water-borne K-export data from 17 harvested and 5 control catchments in southern and central Finland. K concentrations and runoff were monitored for 1–2 years before and 3–4 years after treatment. Supplementary long-term data from one pair of harvested and non-managed catchments was used to assess the duration of the harvest impact on K export. Mean annual K concentrations in ditch outflow were higher after than before harvesting. The concentrations started to increase during the second or third post-harvest year, reaching the peaks of 1.1–2.2 mg L−1 in WTHS, 0.8–1.7 mg L−1 in WTH, and 1.0–1.9 mg L−1 in SOH. The concentrations correlated positively with the amount of K in the surface peat. In nutrient-poor ombrotrophic sites, the K concentrations were higher for sites with shallower water-table level. Using the supplementary data, the impact of harvesting on K losses was estimated to last for about eight years. The overall estimated K loss was about 28 kg ha−1 from minerotrophic sites, and about 9 kg ha−1 from ombrotrophic sites. There was no significant difference in K losses between the harvest treatments SOH, WTH and WTHS, indicating that the K in harvest residues was largely retained onsite. The role of K losses induced by harvesting in the site K stores in drained peatland forests is discussed.

A 582-cm-long peat core was collected from Baltic Bog, an ombrotrophic peatland in north-eastern Prince Edward Island, Canada. The core was studied for testate amoebae, plant macrofossils, macrocharcoal, peat humification and organic matter content. The results show that Baltic Bog first developed ∼9600 cal a BP as a minerotrophic peatland (fen) dominated by Cyperaceae. At 8200 cal a BP, the fen transitioned into a peat bog dominated by Sphagnum. Between 8200 and 4000 cal a BP, water table depth (WTD) was generally low and the bog surface supported trees such as Picea mariana. From 4000 to 1700 cal a BP, WTD rose and the bog became more open. The macrocharcoal results show that the period ∼2000–1000 cal a BP was characterized by several fire events that may have occurred on the bog surface at the core site. The results presented in this paper correspond closely with previous fossil pollen research done at Baltic Bog and suggest that regional climate change was a key factor in controlling long-term WTD variability and vegetation change at the site.

Wildfire frequency and severity in boreal peatlands can be limited by wet fuel conditions, but increases in burn severity can occur when lower water table positions cause drying of fuels. To date, most studies on northern peatland fires have focused on ombrotrophic bogs. Though minerotrophic fens are the most common type of peatland in North America, the influence of fuel structure and loading on potential fire behaviour in boreal fens is poorly understood. To investigate the potential for widespread flame front propagation across boreal fens, we quantified the fuel components present in three generalized boreal fen types (open, shrub, and treed fens) in northern Alberta, Canada. The loadings of aerial fuels, tall shrubs, and downed woody debris varied significantly among fen types. Fuel loads tended to be smallest in the open fens and largest in the treed fens. Open and shrub fens had larger loads of total surface fuels relative to treed fens, with short-statured shrubs being the dominant contributor to surface fuel load. Based on our observations of available fuel loads, each of the fen types may support moderate- to high-intensity fire following long-term drying, which may not only consume some fraction of the aboveground biomass, but also provide a substantial downward pulse of energy to initiate smouldering in the organic layer.

Ombrotrophic bogs are faithful archive of atmospheric metal deposition, but the potential for fens to reconstruct environmental change is often underestimated. In this study, some new data on the Pb depositional history in northeast China were provided using two 210Pb-dated peat sequences from a poor fen in the Fenghuang Mountain of Heilongjiang province. Anthropogenic, detritic and atmospheric soil sources were discriminated using a two-step sequential digestion (weak acid leaching to liberate mobile Pb which is often regarded as anthropogenic Pb, especially for recent samples) and a ratio of unsupported 210Pb and supported 210Pb with the logic of that the 214Pb mainly represents the residual detritus (constant throughout the core) and the unsupported 210Pb arises from atmospheric fallout. A higher 210Pb/214Pb suggests more contributions from atmospheric deposition to the Pb content in the peat, and a ratio of 10 was defined to indicate the boundary between detritic input and atmospheric deposition. The detritic Pb was estimated to be 10−13 mg·kg−1, the anthropogenic Pb ranged from 10−80 mg·kg−1, and the atmospheric soil-derived Pb ranged from < 5 mg·kg−1 to 30 mg·kg−1. The history of anthropogenic Pb pollution over the last 150 years was reconstructed, and the calculated Pb deposition rate (AR Pb) ranged from 5 to 56 mg·m-2·yr-1. Using Ti as a reliable reference, the enrichment factor of Pb (EF Pb) relative to the upper continental crust was calculated. Both AR Pb and EF Pb increased with time, especially after the foundation of the People’s Republic of China. This is consistent with increasing industrialization and coal burning in the last 60 years in northeast China. The present record of anthropogenic Pb deposition was consistent with the previous reports and an increasing trend of environmental pollution due to anthropogenic activities, in contrasts to Europe and North America which have experienced a major environmental cleanup. For the first time, this work estimates atmospheric Pb deposition via a minerotrophic peat core in China. This will enhance the use of peat archives for studies of environmental change.

Despite their importance as global carbon sinks, peatlands of Southeast Asia have been rarely studied and our current knowledge of the dynamics and ecology of these ecosystems remains incomplete. Paleoecological and palynological multi-proxy analyses including analysis of pollen, spores, charcoal, testate amoebae and sediments were carried out on a 733 cm-long core taken from the Air Hitam peatland in the Jambi Province, Central Sumatra, Indonesia. The radiocarbon chronology reveals that peat formation started ca. 7800 years ago. The site was covered by dipterocarp-swamp mixed rainforest during the first 2000 years, after which freshwater swamp taxa became more important, in particular Durio trees. This lasted until ca. 4500 years ago, when the swamp vegetation shifted to a pole forest with abundant Pandanus thickets in response to a system change from minerotrophic to ombrotrophic conditions. For this period, macro-charcoal analysis reveals that fire frequency increased, possibly as a consequence of climate change linked to the onset of the modern El Nino Southern Oscillation (ENSO) in the late Holocene. The ombrogenous Pandanus-pole forest phases were characterized by lower water table fluctuations and higher peat accumulation rates. The area of Air Hitam has been for thousands of years a highly effective carbon sequestering peatland. Natural climate variability in the past did not affect the carbon storage function as suggested by the general increase in peat accumulation during relatively drier phases and increasing ENSO variability in the late Holocene. However, the recent changes caused by selective logging, drainage and conversion to oil palm plantations, have caused a decline in the peat swamp forest communities changing the ecological functions of the peatland. It is likely that the accumulated carbon will be released in the atmosphere due to exposure to aerobic conditions and its function will be lost unless a better management of the watershed is applied.

Thompson Pond, a bog lake in Pine Plains, New York, has flora indicative of both ombrotrophic and minerotrophic conditions. Distinct community types within this wetland system include a peripheral moat, hummock swamp, floating vegetation mats, peat rafts, aquatic floating-leaved and submergent macrophytes, and open water. A false-bottom of unconsolidated peat overlies the lake bed. Vegetation composition is typically diverse in such lakes, which support species of both acidic and calcareous habitat affinities. We repeated a 1973–74 survey to assess changes in wetland flora after four decades. The recent survey yielded 218 vascular plant species, representing 66 families and 134 genera. The largest genus was Carex with 26 species. Forty species from the original survey were not relocated, and 97 species were found in the recent survey that had not been found in the original survey. Eriocaulon aquaticum, usually associated with oligotrophic waters, was common in the original survey and not found in the recent survey. Aerial photos were used to calculate the change in vegetation cover, revealing that floating vegetation mats and peat rafts expanded between 1970 and 2016. Nutrient loading from agricultural and residential land use within the watershed, in addition to the installation of a dam across the lake's surface water outlet have likely contributed to the floristic and community structure changes seen in Thompson Pond.

Mires, or peat-forming systems, have traditionally been recognised as falling into two broad peat-forming types – minerotrophic fens fed by groundwater or collected surface water, and ombrotrophic bogs fed exclusively by direct precipitation. Different types of fen can then be distinguished based on sources of water and rates of water supply. In contrast, ombrotrophic bogs can be classified according to their morphology, position within the landscape and consequent developmental history. A few ‘mixed’ or ‘intermediate’ mire types can also be identified.

Summary Peatlands are an important component of the global carbon cycle because they comprise huge amounts of terrestrial carbon (C). Different conditions during peat formation and secondary peat decomposition affect the quantity and composition of soil organic matter (SOM) in peats. There are few comparative studies on the chemical composition of SOM in temperate peatland soil. This study investigates compositional changes of SOM functional groups in peats and corresponding peat-forming plants by Fourier transform infrared (FTIR) spectroscopy. Three plant samples and 29 peat samples were taken from seven temperate peatland sites with different genesis and land-use intensity. Site-specific differences, such as genesis of the peat, were found to be reflected in the FTIR spectra. In general, there was more variation in FTIR spectra in samples from fens than in those from bogs and peat-forming plants. The samples from fens have a smaller C–H absorption band than those from bogs and plants, which reflects greater biochemical activity in the minerotrophic than ombrotrophic environments. In addition to peat genesis, drainage and secondary peat decomposition also affect SOM composition substantially. The larger amounts of aliphatic compounds in undrained peats could be explained by selective preservation caused by anaerobic conditions. With increasing drainage of the sites, there was a decrease in the C–H absorption that was accompanied by a relative increase in C=O absorption. These changes in absorption intensities reflect the enhanced aerobic decomposition and mineralization that accompanies drainage and land-use intensity. However, the ‘degree of peat decomposition’, a diagnostic tool used in the field, is not reflected by OM composition determined by FTIR spectroscopy. Our results contribute to further understanding of changes in SOM composition during peat formation and processes of secondary decomposition caused by drainage.

Ombrotrophic peat bogs from Tierra del Fuego are characteristically raised, dome-shaped, fed by precipitation, and nutrient-poor. Their landscape pattern consists of a Sphagnum magellanicum matrix encompassing pools with different morphometric and trophic features. Within the framework of a 2-year limnological survey in five pools from Rancho Hambre peat bog, we analyzed phytoplankton communities under the hypothesis that taxonomic composition would show a spatial pattern driven by ultimately landscape-controlled environmental features such as pH and trophic status, while temperature and weather-dependent features would account for seasonal changes in abundance and structure. Among the 305 taxa recorded, most were Conjugatophyceae and Bacillariophyceae, and were strongly associated to circumneutral pH and minerotrophic conditions, though limited superficial connectivity among pools accounted for dissimilar taxonomic compositions. Despite such differences, phytoplankton of pools with similar morphometry and trophic status showed similar dominant and richest taxonomic groups undergoing paralell changes over time. Seasonal temperature fluctuations were modulated by pool size and modified not only abiotic properties but also phytoplankton abundance, with different taxa showing strong summer peaks in different pools. An interpretative model is proposed which will be tested as a tool for predicting community strategy and temporal variation patterns as responses to different environmental templates. Fil: Mataloni, Maria Gabriela. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. Laboratorio de Biodiversidad, Limnología y Conservación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gonzalez Garraza, Gabriela Carolina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. Laboratorio de Biodiversidad, Limnología y Conservación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Vinocur, Alicia Liliana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina

Mosses are the dominant plants in polar and boreal regions, areas which are experiencing rapid impacts of regional warming. Long-term monitoring programmes provide some records of the rate of recent climate change, but moss peat banks contain an unrivalled temporal record of past climate change on terrestrial plant Antarctic systems. We summarise the current understanding of climatic proxies and determinants of moss growth for contrasting continental and maritime Antarctic regions, as informed by 13C and 18O signals in organic material. Rates of moss accumulation are more than three times higher in the maritime Antarctic than continental Antarctica with growing season length being a critical determinant of growth rate, and high carbon isotope discrimination values reflecting optimal hydration conditions. Correlation plots of 13C and 18O values show that species (Chorisodontium aciphyllum / Polytrichum strictum) and growth form (hummock / bank) are the major determinants of measured isotope ratios. The interplay between moss growth form, photosynthetic physiology, water status and isotope composition are compared with developments of secondary proxies, such as chlorophyll fluorescence. These approaches provide a framework to consider the potential impact of climate change on terrestrial Antarctic habitats as well as having implications for future studies of temperate, boreal and Arctic peatlands. There are many urgent ecological and environmental problems in the Arctic related to mosses in a changing climate, but the geographical ranges of species and life-forms are difficult to track individually. Our goal was to translate what we have learned from the more simple systems in Antarctica, for application to Arctic habitats.

This study focusses on the ecology of testate amoeba species in peatlands of the southern taiga of Western Siberia. To estimate the influence of the trophic state of mires on species optima related to water table depth, a separate study of three calibration datasets including ombrotrophic, minerotrophic and the combined habitats was conducted. In the datasets obtained separately from ombrotrophic and minerotrophic mires, the water table depth was the main factor affecting testate amoeba assemblages. However, the trophic state (specifically pH and ash content) was more important factor in the combined dataset, including all of the studied mires. For 36 testate amoeba species, which were found in the ombrotrophic and minerotrophic mire habitats, their species optima, obtained separately in ombrotrophic and minerotrophic datasets, differed significantly from each other. Some of these species preferred minerotrophic conditions, while others preferred ombrotrophic ones. For all species, the trophic state of the mires affected the values of the species optima related to water table depth, as revealed in the form of a threshold effect. In extreme conditions, the species were more sensitive to the trophic status than to the water table depth, and their optimum related to water table depth was distorted. Variation of the optimum was observed in those species that inhabited both ombrotrophic and minerotrophic mires due to the fact that mires with a different trophic status were included in the training sets. The optima did not vary for species inhabiting only ombrotrophic or only minerotrophic mires.

Minerotrophic fens and ombrotrophic bogs differ in their nutrient status, hydrology, vegetation and carbon dynamics, and their geographical distribution is linked to various climate parameters. Currently, bogs dominate the northern temperate and southern boreal zones but climate warming may cause a northwards shift in the distribution of the bog zone. To more profoundly understand the sensitivity of peatlands to changes in climate, we first used the plant macrofossil method to identify plant communities that are characteristic of past fen–bog transitions. These transitions were radiocarbon dated, to be linked to Holocene climate phases. Subsequently, palaeoecological data were combined with an extensive vegetation survey dataset collected along the current fen–bog ecotone in Finland where we studied how the distribution of the key plant species identified from peat records is currently related to the most important environmental variables. The fossil plant records revealed clear successional phases: an initial Carex-dominated fen phase, an Eriophorum vaginatum–dominated oligotrophic fen phase followed by an early bog phase with wet bog Sphagna. This was occasionally followed by a dry ombrotrophic bog phase. Timing of initiation and phase transitions, and duration of succession phases varied between three sites studied. However, the final ombrotrophication occurred during 2000–3000 cal. BP corresponding to the neoglacial cooling phase. Dry mid-Holocene seems to have facilitated initiation of Eriophorum fens. The peatlands surveyed in the fen–bog ecotone were classified into succession phases based on the key species distribution. In 33% of the studied peatlands, Sphagnum had taken over and we interpret they are going through a final transition from fen to bog. In addition to autogenic processes and direct climate impact, our results showed that ecosystem shifts are also driven by allogenic disturbances, such as fires, suggesting that climate change can indirectly assist the ombrotrophication process in the southern border of the fen–bog ecotone.

We compared carbon (C), nitrogen (N), and phosphorus (P) concentrations in atmospheric deposition, runoff, and soils with microbial respiration [dehydrogenase (DHA)] and ecoenzyme activity (EEA) in an ombrotrophic bog and a minerotrophic fen to investigate the environmental drivers of biogeochemical cycling in peatlands at the Marcell Experimental Forest in northern Minnesota, USA. Ecoenzymatic stoichiometry was used to construct models for C use efficiency (CUE) and decomposition (M), and these were used to model respiration (Rm). Our goals were to determine the relative C, N, and P limitations on microbial processes and organic matter decomposition, and to identify environmental constraints on ecoenzymatic processes. Mean annual water, C, and P yields were greater in the fen, while N yields were similar in both the bog and fen. Soil chemistry differed between the bog and fen, and both watersheds exhibited significant differences among soil horizons. DHA and EEA differed by watersheds and soil horizons, CUE, M, and Rm differed only by soil horizons. C, N, or P limitations indicated by EEA stoichiometry were confirmed with orthogonal regressions of ecoenzyme pairs and enzyme vector analyses, and indicated greater N and P limitation in the bog than in the fen, with an overall tendency toward P-limitation in both the bog and fen. Ecoenzymatic stoichiometry, microbial respiration, and organic matter decomposition were responsive to resource availability and the environmental drivers of microbial metabolism, including those related to global climate changes.

Sphagnum-associated methanotrophs (SAM) are an important sink for the methane (CH4) formed in boreal peatlands. We aimed to reveal how peatland succession, which entails a directional change in several environmental variables, affects SAM and their activity. Based on the pmoA microarray results, SAM community structure changes when a peatland develops from a minerotrophic fen to an ombrotrophic bog. Methanotroph subtypes Ia, Ib, and II showed slightly contrasting patterns during succession, suggesting differences in their ecological niche adaptation. Although the direct DNA-based analysis revealed a high diversity of type Ib and II methanotrophs throughout the studied peatland chronosequence, stable isotope probing (SIP) of the pmoA gene indicated they were active mainly during the later stages of succession. In contrast, type Ia methanotrophs showed active CH4 consumption in all analyzed samples. SIP-derived (13)C-labeled 16S rRNA gene clone libraries revealed a high diversity of SAM in every succession stage including some putative Methylocella/Methyloferula methanotrophs that are not detectable with the pmoA-based approach. In addition, a high diversity of 16S rRNA gene sequences likely representing cross-labeled nonmethanotrophs was discovered, including a significant proportion of Verrucomicrobia-related sequences. These results help to predict the effects of changing environmental conditions on SAM communities and activity.

Climate change is expected to affect biodiversity elements in the Catskill High Peaks subecoregion of New York State with effects that are difficult to predict. The present communication details the species and communities of greatest conservation concern in this portion of the state and makes recommendations for monitoring the most pressing climate change-biodiversity vulnerabilities. Specifically, we present sites for monitoring representative old-growth and successional stands of red spruce/balsam fir and northern hardwood matrix forests, cliff communities, ice cave talus communities, and both minerotrophic inland poor fen and ombrotrophic perched peatlands. The proposed monitoring protocols vary among the various sites, but all are quantitative and are designed to document patterns of change.

Testate amoebae are common proxy for water table depth in peatlands and are commonly used to reconstruct past hydroclimatic conditions. In northeastern America, previous transfer function development was mostly limited to ombrotrophic peatlands from continental and/or oceanic contexts. This study provides a greater range of modern analogues (n ¼ 206) from ombrotrophic to poor minerotrophic peatlands along an ecoclimatic gradient from boreal to subarctic in both continental and oceanic regions. Multivariate analysis confirmed that water table depth is the dominant control on species distribution, and a new transfer function was developed for this environmental parameter. The WA.inv model has a RMSEP of 5.44 cm and R

Paleoclimate and paleoenvironmental studies in the north-eastern Italian Alps have been hampered by the rarity of well-preserved high-altitude deposits and the lack of high-resolution multi-proxy records with adequate chronological control. This paper presents the first complete Late Glacial to Holocene peat succession from the Dolomites (Danta di Cadore, Belluno, Italian Alps). A 7 m core was used to evaluate the potential of the ombrotrophic Val di Ciampo peat deposit (1400 m a.s.l.) as an archive of environmental and climate change. The depth–age scale is based upon independent 14 C and 210 Pb dates and combined with peat stratigraphy demonstrates that the peat core covers more than 13,200 cal BP, extending to the end of the last part of the Late Glacial. Bulk density, inorganic matter content, pore water pH, conductivity, Ca/Mg ratios, and Ca, Sr and Ti trends were used to identify changes in trophic conditions through the bog. The boundary between ombrotrophic and minerotrophic conditions occurs at approximately 400 cm below the surface and demonstrates that this core is the longest Eastern Alpine ombrotrophic record yet obtained, corresponding to 7000 cal BP. The high-resolution chemical data of this peat archive improves our understanding of European Alpine Holocene climate variability and the relationship between natural climate fluctuations and anthropogenic climate change during the present interglacial in the Dolomites.

Multi-proxy analysis (sedimentological, palaeobotanical, geochemical data and results of radiocarbon dating) of the biogenic sediments from a small mire ecosystem in the Sandomierz Basin (SE Poland) is presented. The ecosystem contains a full hydroseral sequence from minerotrophic to ombrotrophic wetland. It is one of the few sites in this region which is so thoroughly investigated in terms of the palaeoenvironmental record. Changes in the water supply of the mire area, and consequently the changes in the plant and sediment succession, were well correlated with the regional tendencies in precipitation and temperature during the Late Glacial/Holocene transition and in the Holocene. Human impact is very well recorded in pollen diagram from the Subboreal period.

[1] Variations to the global wetland CH4 source strength in response to changes in orbital insolation patterns and atmospheric CO2 concentration ([CO2]a) are hypothesized to play an important role in determining glacial-interglacial variations in atmospheric CH4 concentration ([CH4]a). Here the interactive effects of temperature, a major controlling variable determining wetland CH4 flux, and the low [CO2]a of glacial intervals are investigated for the first time. We measured the temperature dependence of CH4 emissions from replicated mesocosms (n = 8 per CO2 treatment) collected from a minerotrophic fen and an ombrotrophic bog incubated in either ambient (c. 400 ppm) or glacial (c. 200 ppm) [CO2]a located in the United Kingdom. CH4 fluxes were measured at 5 � C, 10 � C, 15 � C, 20 � C, and 25 � C and then in reverse order over a 20 day period under each [CO2]a treatment. Results showed that the Q10 temperature response of CH4 emissions from the Carex/Juncus-dominated fen declined significantly by approximately 39% under glacial [CO2]a (ambient [CO2]a = 2.60, glacial [CO2]a = 1.60; P 0.05). This contrasting response may be linked to differences in plant species assemblage and the varying impact of CO2 starvation on plant productivity and carbon availability in the rhizosphere. Furthermore, our results provide empirical evidence to support recent model-based indications that glacial-interglacial variations in [CH4]a may be explained by changes in wetland CH4 source strength in response to orbitally forced changes in climate and [CO2]a.

Ombrotrophic peatlands are those that are purely fed by precipitation and are unconnected to groundwaters. Identification of ombrotophic peatlands is of interest because of their utility as a depositional archive, their unique botanical characteristics, and their sensitivity to climate change. Seven high elevation peatlands in the Catskill Mountains of New York state are investigated in this paper; six of these are identified as ombrotrophic bogs and one is determined to be a minerotrophic (groundwater-fed) poor fen. In order to identify these peatlands as ombrotrophic, concentrations of major ions in surface pools are examined; the proportion of calcium and magnesium in surface pools is particularly indicative of ombrotrophy. Average Ca/Mg (mg L−1) ratios in bogs, precipitation, and springs are 4.3, 5.0, and 6.7, respectively. Stable isotopes of water (deuterium and 18O) are examined as well and may provide a novel method of determining the water source to peatlands; peatland isotopic data plot along what appears to be a local evaporation line.

The mean cell sizes of microalgae vary in relation to the abiotic factors, such as nutrients, temperature, or water transparency. This study focused on the community cell size of desmids and diatoms, two dominant groups of the peatland phytobenthos. Forty samples from various temperate European peatlands were investigated. The species composition and the species richness were controlled mainly by the pH levels. Purely spatial factors also significantly affected the species composition. Interestingly, diatoms were more strongly geographically restricted than desmids. The spatial control of the species composition was limited mostly to the large taxa, which indicated that dispersal limitation may be an important structuring factor for phytobenthos at a regional scale. The mean cell sizes of desmids were related to the ombro-minerotrophic gradient, pH, and Ca concentration. Acidic, ombrotrophic bogs typically contained small cells, whereas minerotrophic fens had larger desmids. By contrast, the diatom size structure did not depend on the ombro-minerotrophic gradient. Thus, the cell sizes of desmids in peatlands may be used as a proxy for important environmental processes, such as transition from minerotrophy to ombrotrophy, or acidification, whereas diatoms did not primarily respond to these processes and their size structure is driven by different factors, such as conductivity.

Methane (CH4) production varies greatly among different types of peatlands along an ombrotrophice minerotrophic hydrogeomorphic gradient. pH is thought to be a dominant control over observed differences in CH4 production across sites, and previous pH manipulation experiments have verified the inhibitory effect of low pH on CH4 production. In this experiment, we asked (i) if the major effect of low pH is direct inhibition of one or both pathways of methanogenesis and/or inhibition of ‘upstream’ fermentation that provides substrates for methanogens, and (ii) to what extent is pH sufficient to explain differences in CH4 production relative to other factors that co-vary across the gradient. To address these questions, we adjusted the pH of peat slurries from 6 peatlands to 4 levels (3.5, 4.5, 5.5, and 6.5) that reflected their range of native pH, maintained these pH levels over a 43-day anaerobic laboratory incubation, and measured a suite of responses within the anaerobic carbon cycle. Higher pH caused a significant increase in CO2 production in all sites. Regardless of site, time, and pH level, the reduction of inorganic electron acceptors contributed to