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Methane production usually increases from the acidic sphagnum-dominated ombrotrophic peatlands to minerotrophic ones with more neutral pH and higher coverage of vascular plants. Along this ombrotrophic–minerotrophic gradient, pH, microbial communities, and properties of dissolved organic matter in porewater all vary greatly. The hydrographic change resulted from permafrost thaw and projected global warming can potentially connect the minerotrophic and ombrotrophic sites via porewater and turn acidic bogs to minerotrophic fens. It is thus very important to investigate how the anaerobic carbon degradation processes respond to changes in fundamental factors like pH, temperature, properties of dissolved organic matter, and microbial communities resulted from such hydrographic change. In this study, one ombrotrophic (pH = 3.9) and one minerotrophic peatland site were sampled in Fairbanks, Alaska in Sep 2017 and a 42-day-period anaerobic laboratory incubation was conducted to study the changes in anaerobic carbon degradation processes including primary and secondary fermentation, methanogenesis, and acetogenesis when pH, temperature, and porewater were manipulated individually and a combination of two or three of these factors. The results suggested lowering pH would inhibit many anaerobic carbon degradation processes in the minerotrophic peatland except primary fermentation. Elevating pH in the ombrotrophic site did not stimulate its methanogen community, but primary fermentation responded better with increasing pH than with increasing temperature alone. Replacing the porewater in the minerotrophic site with that from the ombrotrophic site with high aromaticity did not inhibit methanogenesis but potentially brought in highly efficient primary fermenters. Acetoclastic methanogenesis, acetogenesis, and syntrophy only exist in the minerotrophic site but not at the ombrotrophic one. Porewater from the minerotrophic site could potentially introduce acetoclastic methanogens and syntrophs to the ombrotrophic site but would not make them active unless both pH and temperature were increased. When ground water connects ombrotrophic and minerotrophic peatlands due to thawing of permafrost, secondary fermenters and acetoclastic methanogens could be introduced to acidic bogs and cooperate efficiently to degrade the stored carbon in ombrotrophic peatlands especially under elevated temperature conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Typically, restoration goals target a point in history, i.e., the 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 ~1,100 sites was examined in context of hydroperiod, spatial and temporal trends in water quality from the 1940s 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. [ABSTRACT FROM AUTHOR]

Abstract: Peatlands abandoned after being exploited for horticultural materials can be characterized by soil–water deficits that challenge the establishment of appropriate plant species, thus rewetting is an important step to restoring them to naturally functioning ecosystems. A bog section of Bic-Saint-Fabien peatland near Rimouski, QC was vacuum-harvested for peat production and abandoned in 2000. Harvesting activity left topographic elevation differences across the harvested area, creating wetness gradients. In general, the site interior had more available water than peripheral regions. Bic-Saint-Fabien was cut down to minerotrophic sedge peat; therefore it was restored as a fen. Research for this study lasted four years, 2008–2011. A water budget was created for every year of study to determine the importance of different hydrological parameters at Bic-Saint-Fabien. The main loss of water was through evapotranspiration and the principal input was precipitation. The main difference in the water budget between study years was that pre-rewetting was climatologically wetter than post-rewetting. Despite more available water before rewetting, before-after-control-impact design ANOVA indicated the water table was significantly higher at the cutover area after rewetting. In 2011 a wetness gradient remained evident within the cutover section of the peatland; however the mean seasonal water table was close (within 20cm) to the peat surface at all measured wells. An interior section of Bic-Saint-Fabien remained saturated for nearly all of 2011 and had mean seasonal water table of +2.4cm, and volumetric soil moisture content and soil water pressure, measured 5cm below the surface, of 86% and +4mbar, respectively, compared to −15.4cm, 67% and −13mbar, respectively, at a nearby (∼100m) peripheral section. Systematic differences in wetness across the site suggest that a uniform prescription for vegetation re-establishment in the rewetted section may not be appropriate. [Copyright &y& Elsevier]

Abstract: Forms and accumulation of soil phosphorus (P) were measured in a subalpine quaking peatland on Mt. Changbai in China that is located 1km from the North Korea border. Peat cores were collected from four sites and radiometrically dated to determine long-term ( 210 Pb-based) rates of peat and P accumulation. Soil P forms at different depths in four peat cores were determined by a modified Hedley fraction method. In the minerotrophic fens (fen-W, fen-S, and fen-E), total P (Pt), organic P (Po), NaOH extractable Po (NaOH-Po) and Residual-P ranged from 809±192 to 1214±530, 455±121 to 736±373, 282±100 to 462±247, and 152±36 to 325±118mgPkg−1, respectively. In an ombrotrophic bog (bog-N), the corresponding values were 705±163, 387±125, 204±103, and 101±15mgPkg−1 respectively. Many of those were higher in the fens than in the bog. Significantly different accumulation rates of peat were determined for the fens (0.063 to 0.081gDMcm−2 yr−1) and bog (0.038gDMcm−2 yr−1). Compared with other peatlands, the accumulation of Pt in the Yuanchi peatland (0.69±0.4 to 2.04±0.6gPm−2 yr−1) was higher, suggesting that the volcanic parent material had an influence on P accumulation. [Copyright &y& Elsevier]

This study investigates the testate amoeba communities of a large peatland in Central China. The ecology and seasonal variability of testate amoeba communities were studied during 2009-2010. Investigation of environmental controls using ordination showed that the relationship between testate amoeba communities and depth to water table (DWT) and pH are extremely weak. The small proportion of variance explained by water table depth here (only 1.9% in the full data) shows that the hydrological control is weaker than we expected in this peatland, and weaker than any study we are aware of using a similar methodology. Attempts to develop species-environment (transfer function) models or identify indicator species for future palaeoecological studies were unsuccessful. Previous large-scale studies of peatland testate amoeba ecology have been largely restricted to Europe and North America and results have been relatively consistent among studies. Our results contrast with this consensus and suggest that at least in minerotrophic peatlands in China testate amoeba communities may be primarily controlled by different environmental variables. In China, testate amoebae have been relatively little studied but may prove to be valuable for a variety of applications in palaeoecology and biomonitoring and much further work is required. [ABSTRACT FROM AUTHOR]

Abstract: In this study we quantify the partitioning of recent assimilates to above- and below-ground carbon (C) pools in two subarctic mire ecosystems – wet minerotrophic and semiwet ombrotrophic mire – using in situ 14C pulse-labelling. Ecosystem C partitioning to rhizomes, coarse roots, fine roots, dissolved organic carbon (DOC) and microbes were quantified twice  during the growing season at three different soil depths. Finally the 14C-partitioning data from this and a previous study were combined to estimate the overall C partitioning of the three main vegetation types of a Scandinavian subarctic mire in early and late summer. The semiwet ombrotrophic ecosystem hosted a much larger root biomass on an area basis compared to the wet minerotrophic ecosystem which might be due to differences in the soil nutrient level. Microbial C was found to be the largest C-pool in both ecosystems. Ecosystem 14C partitioning was poorly related to plant biomass for the semiwet and the wet ecosystem. Overall a higher partitioning of recent assimilates to below-ground compartments was apparent in August–September compared to June–July, while the opposite was found for the above-ground C-pools. In the semiwet ecosystem twice as much 14C was found in DOC compared to the wet ecosystem, where root density, litter and above-ground biomass were important controls of the 14C-recovery in DOC. Plant-derived DOC was estimated to be 15.4 versus 12.9 mg C m−2 d−1 in the semiwet and wet ecosystem, respectively. Graminoid dominated and dwarf shrub dominated vegetation types of the subarctic mire Stordalen differ with respect to the relative amount of recently assimilated C partitioned to C-pools with “slow” versus “fast” decomposition rate. The capacity for sequestration of recently fixed C within “slow” C-pools might affect the ecosystem C balance (NEE) and C-storage. The potential for vegetation changes might therefore be an important factor to consider in studies of response of ecosystem C-dynamics to global change factors in subarctic mires. [Copyright &y& Elsevier]

Seasonal variations in pore water and solid phase geochemistry were investigated in urbanized minerotrophic peat sediments located in southwestern Michigan, USA. Sediment pore waters were collected anaerobically, using pore water equilibrators with dialysis membranes (“peepers”) and analyzed for pH, alkalinity, dissolved ΣPO4 −3, ΣNH4 +, ΣS−2, SO4 −2, Fe+3, Fe+2, and Mn+2 at 1-2 cm intervals to a depth of 50 cm. Cores collected adjacent to the peepers during all four seasons were analyzed for reactive solid phase Fe according to extraction methods proposed by Kostka and Luther (1994). The association of Fe and trace metals (Mn, Pb, Zn, Cu, Cr, Co, Cd, U) with operationally defined solid phase fractions (carbonates, iron and manganese oxides, sulfides/organics and residual) was assessed for cores extracted during winter and spring using extraction methods proposed by Tessier et al. (1979, 1982). Pore water Fe and S data demonstrate a clear seasonal variation in redox stratification of these sediments. The redox stratification becomes more compressed in spring and summer, with relatively more reducing conditions closer to the sediment water interface (SWI), and less reducing conditions near the SWI in fall and winter. In the upper 10–15 cm of sediment, the pool of ascorbate extractable Fe, thought to be indicative of reactive Fe(III) oxides, diminishes during spring and summer, in agreement with seasonal changes in redox stratification indicated by the pore water data. Tessier extractions indicate that the total extractable quantity of all metals analyzed in this study decrease with depth, and that the majority of the non-residual Fe, Pb, Zn, Cu, Cr, Co, Cd, and U is typically associated with the sulfide/organic fraction of the sediments at all depths. Non-residual Mn, in contrast, is significantly associated with carbonates in the upper 15–25 cm of the sediment, and predominantly associated with the sulfide/organic fraction only in deeper sediments. [ABSTRACT FROM AUTHOR]

Minerotrophic sedge fens are common in sub-arctic regions and are a significant source of atmospheric methane (CH4), yet they have received less attention than other peatlands, such as boreal ombrotrophic bogs, which are smaller sources of CH4. At the process level, CH4 fluxes in sub-arctic systems are limited primarily by cold temperatures, and thus are sensitive to potential climate change. This study examined CH4 dynamics in a temperate sedge-fen to determine controls on the spatial and temporal variability in CH4 fluxes and, therefore, how the biogeochemistry of CH4 in sedge-fen peatlands may respond to predicted changes in climate. We used flux chambers and laboratory peat incubations over a six to seven-year period (1994-2000) to study fluxes, pools, and potential production of CH4 in a peat-forming wetland in central New York State, USA. Results showed that precipitation (i.e., dry years and depth to water table) exerted an important control on annual and seasonal patterns of CH4 fluxes. Mean summer flux rates ranged from 2258 nmol m-2 s-1 in the wettest year to -934 nmol m-2 s-1 (net consumption) in the driest year. CH4 concentrations in the surface peat were as low as 0.01 μatm and as high as 10 matm in the summer months depending on precipitation patterns. In contrast, CH4 concentrations were consistently two to three times greater in sub-surface than in surface peat, and pools persisted during dry years and were temporally less variable. Fluxes were only weakly associated with potential CH4 production rates, which showed little seasonal variation. In-vitro measurements of potential CH4 production did not sufficiently explain fluxes, suggesting a need for improved in-situ methods for measuring CH4 production. Site differences associated with different dominant vegetation had a significant effect on CH4 cycling in all years except the driest, suggesting sensitivity to vegetation changes. These results indicate that predicting responses of fen peatlands to environmental requires an improved understanding of the underlying microbial processes and mechanisms that control CH4 cycling. [ABSTRACT FROM AUTHOR]

The structure of peatland vegetation in Minnesota is affected by trophic conditions, the soil-water regime, and the disturbance history. Trophic conditions have a major effect on the species composition. Structurally, this results in the exclusion of most tall shrubs, hardwood trees, and forbs from ombrotrophic sites and a greater biomass of mosses and ericad shrubs on those sites than on minerotrophic sites. Classification of peatland vegetation into physiognomic groups provides reasonable estimates of total aboveground biomass. Trophic conditions per se, however, have a minor effect on aboveground biomass; on both ombrotrophic and minerotrophic peatlands, biomass increases from less than 10 Mg ha on the wettest sites to over 100 Mg ha on the driest, undisturbed sites. Peatland sites that have comparatively dry, well-aerated soils support dense forests if they have not recently been disturbed; shrubs dominate on those sites after disturbance. Excessively wet sites are dominated by mosses (particularly on ombrotrophic peatlands) or graminoids (on minerotrophic peatlands). On ombrotrophic sites, the relatively dry conditions that lead to higher tree and total biomass also lead to lower pH resulting in an inverse relationship between biomass and pH. [ABSTRACT FROM AUTHOR]