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The aim of this study was to determine the effect of drainage on peat properties, porewater chemistry, and peat decomposition proxies in an ombrogenous peatland in the Hudson Bay Lowland (HBL). We anticipated that drainage would change peatland hydrology, vegetation, and biogeochemistry, leading to an increase in peat decomposition. As indicators of peat biogeochemical change and potential proxies for peat decomposition, we compared peat porewater chemistry and in situ nutrient availability of different microforms in a pristine ombrogenous bog, with a bog that has been subject to gradual lowering of the water table by 20 to 80 cm for approximately 7 years prior to, and during, our study. We also examined the chemical composition of peat and peat leachates (organic matter) from Sphagnum and lichen-covered hummocks at each site. Nutrient availability was greater in pools at the drained bog, indicating mineralisation of the dry and bare peat surface. However, our results did not show evidence of significant peat biogeochemical change or advanced decomposition in hummocks at the drained bog, with no difference in nutrient availabilities, peat porewater chemistry, or peat leachate chemistry at the drained and pristine bog. We also found no significant difference in enzyme activity (phenol oxidases) in hummocks at each site, proposed to be an important factor for C loss from peatland ecosystems in drier conditions. Overall, the effects of drainage on peat properties, porewater chemistry, and peat chemical composition at our sites were small and varied for different vegetation-microform types. Although decomposition in drained peatlands is likely constrained by cool temperatures in the HBL, our results suggest that ecohydrological feedbacks at the microform scale may also be important in slowing decomposition in these peatlands. [ABSTRACT FROM AUTHOR]

We examined the concentration of nitrogen (N) and δ15N in vegetation and peat in the Mer Bleue bog, Ontario, Canada. Compared with other ecosystems, N concentration in bog plant foliage is low (generally < 1.2%), with more N stored belowground than in foliar tissues. The natural abundance of 15N varies by plant functional type, indicating different strategies for nutrient acquisition. δ15N values of evergreen shrubs and trees are lower (~− 5 to ~− 9‰) than sedges and herbs (~+ 1 to ~− 1‰), likely the result of ericoid mycorrhizal fungi, which retain 15N in fungal biomass, with preferential transfer of 14N to the host plant. Results suggest that N in Sphagnum moss capitula is derived from uptake of N from decomposing peat and litter, with δ15N values of − 8 to − 2‰, rather than from N2 fixation. Soil δ15N varies with depth, related to degree of decomposition and dominant plant species litter. Foliar N plays a critical role in influencing the rate of photosynthesis and CO2 exchange. Despite paucity of available inorganic N in the system, most bog plants (that is, evergreen shrubs) have adapted with conservative growth strategies. Owing to slow decomposition, N is stored in this system tightly bound with organic matter, with C:N ratios in deep peat ranging from 33:1 to 23:1 and small fluxes into, out of and within the system. An increase in N availability, through atmospheric N deposition or water table lowering, could jeopardize the C sink function of bogs by stimulating microbial decomposition of organic matter. In the long term, an increase in N cycling would shift plant community composition from Sphagnum and evergreen dominated to deciduous species, fundamentally altering bog ecosystem function. [ABSTRACT FROM AUTHOR]

To identify the controls on dissolved organic carbon (DOC) production, we incubated soils from 18 sites, a mixture of 52 forest floor and peats and 41 upper mineral soil samples, at three temperatures (3, 10, and 22°C) for over a year and measured DOC concentration in the leachate and carbon dioxide (CO2) production from the samples. Concentrations of DOC in the leachate were in the range encountered in field soils (<2 to >50 mg l−1). There was a decline in DOC production during the incubation, with initial rates averaging 0.03–0.06 mg DOC g−1 soil C day−1, falling to averages of 0.01 mg g−1 soil C day−1; the rate of decline was not strongly related to temperature. Cumulative DOC production rates over the 395 days ranged from less than 0.01 to 0.12 mg g−1 soil C day−1 (0.5–47.6 mg g−1 soil C), with an average of 0.021 mg g−1 soil C day−1 (8.2 mg g−1 soil C). DOC production rate was weakly related to temperature, equivalent to Q10 values of 0.9 to 1.2 for mineral samples and 1.2 to 1.9 for organic samples. Rates of DOC production in the organic samples were correlated with cellulose (positively) and lignin (negatively) proportion in the organic matter, whereas in the mineral samples C and nitrogen (N) provided positive correlations. The partitioning of C released into CO2–C and DOC showed a quotient (CO2–C:DOC) that varied widely among the samples, from 1 to 146. The regression coefficient of CO2–C:DOC production (log10 transformed) ranged from 0.3 to 0.7, all significantly less than 1. At high rates of DOC production, a smaller proportion of CO2 is produced. The CO2–C:DOC quotient was dependent on incubation temperature: in the organic soil samples, the CO2–C:DOC quotient rose from an average of 6 at 3 to 16 at 22°C and in the mineral samples the rise was from 7 to 27. The CO2–C:DOC quotient was related to soil pH in the organic samples and C and N forms in the mineral samples. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and sulfur (S) play important roles in peatlands, through their influence on plant production and peat decomposition rates and on redox reactions, respectively, and peatlands contain substantial stores of these two elements. Using peat N and S concentrations and dry bulk density and210Pb dating, we determined the rates of N and S accumulation over the past 150 years in hummock and hollow profiles from 23 ombrotrophic bogs in eastern Canada. Concentrations of N and S averaged 0.80% and 0.18%, respectively, generally increased with depth in the profile and there was a weak but significant correlation between N and S concentrations. Rates of N and S accumulation over the past 50–150 years ranged from 0.5 to 4.8 g N m−2 yr−1 and from 0.1 to 0.9 g S m−2 yr−1. There were significant but weak correlations between C, N and S accumulation rates over 50-, 100- and 150-year periods. Over the last 50 years, rates of S accumulation showed little differentiation between hummocks and hollows, whereas the pattern for N accumulation was more variable (hummock minus hollow rate ranged from−1 to+1.5 g N m−2 yr−1), with hummocks generally having a larger N accumulation rate, correlated with the rate of carbon (C) accumulation. There was a modest but significant positive correlation between 50-year rates of N accumulation and wet atmospheric deposition of N measured between 1990 and 1996, with accumulation rates about four times that of wet deposition. The difference between deposition and accumulation of N is attributed to organic N deposition, dry deposition and N2 fixation. A weaker, but still significant, correlation was observed between 50-year S accumulation and 1990–1996 wet atmospheric S deposition, with about 75% of the deposited S accumulating in the peat. A laboratory experiment with peat cores exposed to varying water table position and simulated N and S deposition, showed that on average 87% and 98% of the deposited NH4+ and NO3−, respectively, and 58% of the deposited S were retained in the vegetation and unsaturated zone of the cores, supporting the results from the field study. [ABSTRACT FROM AUTHOR]

We showed that sandy subsoils beneath peat near Ramsey Lake, MI, contained 7.5 to 8.0 kg organic C (OC) m-2 to a depth of 70 cm, compared with 1.6 to 3.6 kg m-2 in adjacent forest soils, from which the peatland had evolved through paludification. Compared with the soils beneath the forest, those beneath the peat contained similar amounts of oxalate-extractable Al (Al0) and less Fe, owing to loss of Fe under reduced leached conditions beneath the peat. Most of the extractable Al in the mineral horizons beneath peat was organically bound. Atomic pyrophosphate-extractable (Fep + Alp) Fe + Al/C ratios were smaller (<0.2:1) in the mineral horizons beneath peat than in the forest mineral subsoils (generally >0.2:1), indicating larger inputs and retention in the mineral subsoils beneath peat. Concentration of OC in subsoil samples was strongly (r² = 0.58, p < 0.001) related to the subsoil Al, null-point dissolved organic C (DOC) and clay concentrations. A DOC sorption study using peat pore water ranging from 0 to 117 mg DOC L-1 revealed null-point DOC (DOCnp) concentrations (at which there is neither gain nor loss of OC by the soil) varied from <1 to 417 mg DOC L-1 and was primarily related to Feo (negatively), Alo (negatively), and C (positively). We suggest that the increase in mineral subsoil OC beneath peat is related to the sorption of DOC carried by pore water percolating through the mineral subsoil, combined with slow rates of mineralization of sorbed DOC under anoxic conditions. [ABSTRACT FROM AUTHOR]

Peat deposits of the Muara Siran, East Kalimantan area, were investigated for their vertical and lateral succession, to examine the characteristic variability, particularly its macro- and microtextures. The deposits are situated in the Kutai Basin, in the vicinity of several Cenozoic coal deposits. Peat samples were taken from twenty-seven coring sites in the area, using a MacCaulay peat corer. The Muara Siran peatlands lie between the Kedang Kepala and Belayan Rivers. Siran Lake lies between these rivers and within the peat system. The peat thickness varied from 0.5 m to 12 m. Decomposed sapric peat formed the basal and margins of the deposit, overlain by moderatelydecomposed hemic peat in the central part of the peatlands, though both sapric and hemic peat types are interbedded at the margins of the mire. The fibric peat types were found mostly at the top of the mire and only distal from any active streams. Twenty-four samples of peat were freeze-dried for petrographic analyses of both plant part and maceral analyses using a reflected microscope. On the average, the dominant plant parts were stems and wood (i.e. secondary xylem). Maceral composition was mostly from the huminite group (on the average 89%), particularly the macerals humodetrinite and textinite. Macroscopic peat type and microscopic composition are linked. Fibric peat was found to be rich in wood and textinite. Hemic was mostly composed of stems and wood with textinite and humodetrinite as the most abundant macerals. Sapric peat has near equal proportions of stems, wood, and macerated tissue. Humodetrinite is the most abundant maceral in sapric. The average ash and sulfur content were low, 1.29 wt.% and 0.11 wt.%, respectively. Understanding the physical characteristics of inland peat as in Muara Siran peatland is essential to build knowledge of how inland peat is formed and what makes it different from coastal peat. Muara Siran is a unique, relatively small peatland in the central eastern Kalimantan which is still considerably pristine, hence may serve the aim of this study well. [ABSTRACT FROM AUTHOR]

In this contribution, we report the palynology, organic petrography and carbon isotopes for the #16 Seam in the Lower Cretaceous Yimin Formation of the Hailar Basin, Inner Mongolia, China. Eighteen palynological samples were collected from the coal seam as well as from intraseam partings and the immediate roof. Microfloras comprise a diverse assemblage of ferns, conifers, horsetails, lycopsids, bryophytes, ginkgoes and cycads. Conifer pollen is common, especially representative of Pinaceae (Pinuspollenites) as well as Cheirolepidiaceae (Classopollis) and Araucariaceae (Araucariacites, Chasmatosporite s); however, this material is interpreted as mostly derived from an upland source rather than from the mire-forming vegetation. An overrepresentation of conifer pollen may explain the relatively poor abundance and diversity of ginkgo and cycad pollen, compared to what is found in the macrofossil record. The palynological assemblage found in Seam #16 indicates a Barremian to Aptian age. Maceral composition, ash yields, and δ13C org signature of the coal suggest peat accumulation was controlled by a rising water table from flooding of the mire, coupled with significant ground (peat) fires and/or surface wildfires. These conditions resulted in high levels of detrital mineral matter and charcoal input, the latter represented by inertodetrinite in the coals. The top of the coal seam is characterised by a higher ash yield, lower δ13C org values and increased sphagnacean spores, which suggest the gradual drowning of the palaeomire. Although angiosperms were present in the Hailar Basin during the time that Seam #16 was accumulating, they are absent from the pollen found in this study. This may indicate that they were not yet adapted to the extreme conditions of the mire (e.g., acidity, anoxia), and unable to compete with the established mire vegetation. • Abundant fossil charcoal in the Seam #16 shows fire as an important part of palaeomire ecology. • Ash yields and δ13C org values indicate that flooding terminated the palaeomire. • Some pollen was likely derived from upland conifer forests and transported into the mire. • The absence of angiosperms reflects the harsh, palaeomire conditions. [ABSTRACT FROM AUTHOR]

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here, we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analysed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands. [ABSTRACT FROM AUTHOR]

This study uses life-cycle analysis to examine the net greenhouse gas (GHG) emissions from the Canadian peat industry for the period 1990-2000. GHG exchange is estimated for land-use change, peat extraction and processing, transport to market, and the in situ decomposition of extracted peat. The estimates, based on an additive GHG accounting model, show that the peat extraction life cycle emitted 0.54 × 106 t of GHG in 1990, increasing to 0.89 × 106 t in 2000 (expressed as CO2 equivalents using a 100-y time horizon). Peat decomposition associated with end use was the largest source of GHGs, comprising 71 % of total emissions during this 11-y period. Land use change resulted in a switch of the peatlands from a OHO sink to a source and contributed an additional 15%. Peat transportation was responsible for 10% of total OHO emissions, and extraction and processing contributed 4%. It would take approximately 2000 y to restore the carbon pool to its original size if peatland restoration is successful and the cutover peatland once again becomes a net carbon sink. [ABSTRACT FROM AUTHOR]

Peatlands are ecosystems that accumulate carbon (C) over long periods of time. The anoxic conditions created by prevailing water saturation, coupled with vegetation litter slow to decompose, reduces organic matter decay and allows net C accumulation. Open-water pools that cover many boreal and maritime peatlands are, however, net C sources to the atmosphere. Like lakes but contrary to the surrounding peat, pools are oxygenated environments and enhance the decomposition of organic matter. They are functionally different than peat but also than lakes, because of the organic nature of the matrix in which they are embedded. Using data from an undisturbed ombrotrophic bog of southern Canada, we show that pools are biogeochemical hotspots governed by internal processes and that they influence peatland structure. We also show that pools, while being net C sources to the atmosphere, may be key to sustaining the C accumulation function of peatlands by acting as hydrological buffers for the surrounding peat. [ABSTRACT FROM AUTHOR]

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release. [ABSTRACT FROM AUTHOR]

We examined aerobic and anaerobic microbial carbon dioxide (CO2) and methane (CH4) exchange in peat samples representing different profiles at natural, mined, mined-abandoned, and restored northern peatlands and characterized the nutrient and substrate chemistry and microbial biomass of these soils. Mining and abandonment led to reduced nutrient and substrate availability and occasionally drier conditions in surface peat resulting in a drastic reduction in CO2 and CH4 production, in agreement with previous studies. Owing mainly to wetter conditions, CH4 production and oxidation were faster in restored block-cut than natural sites, whereas in one restored site, increased substrate and nutrient availability led to much more rapid rates of CO2 production. Our work in restored block-cut sites compliments that in vacuum-harvested peatlands undergoing more recent active restoration attempts. The sites we examined covered a large range of soil C substrate quality, nutrient availability, microbial biomass, and microbial activities, allowing us to draw general conclusions about controls on microbial CO2 and CH4 dynamics using stepwise regression analysis among all sites and soil depths. Aerobic and anaerobic decomposition of peat was constrained by organic matter quality, particularly phosphorus (P) and carbon (C) chemistry, and closely linked to the size of the microbial biomass supported by these limiting resources. Methane production was more dominantly controlled by field moisture content (a proxy for anaerobism), even after 20 days of anaerobic laboratory incubation, and to a lesser extent by C substrate availability. As methanogens likely represented only a small proportion of the total microbial biomass, there were no links between total microbial biomass and CH4 production. Methane oxidation was controlled by the same factors influencing CH4 production, leading to the conclusion that CH4 oxidation is primarily controlled by substrate (that is, CH4) availability. Although restoring hydrology similar to natural sites may re-establish CH4 dynamics, there is geographic or site-specific variability in the ability to restore peat decomposition dynamics. [ABSTRACT FROM AUTHOR]

Peat depositional environments, the sites where and conditions under which peat accumulates, significantly influence a resultant coal's physical properties, chemical composition, and coal utilization behavior. Recognition of peat depositional environments for coal is a challenging endeavor because coal's observed compositional properties not only result from a variety of geological processes operating during peat accumulation, but also reflect the influence of adjoining or external depositional sedimentary environments and alteration during later diagenesis and/or epigenesis. The maceral or microlithotype composition of any one layer of peat can be the product of years or decades of plant growth, death, decay, and post-burial infiltration by roots in addition to the symbiotic, mutualistic, parasitic, and saprophytic relationships with non-plant biota, such as arthropods, fungi, and bacteria. The overprint of increasing thermal maturation and fluid migration through time on the resulting coal can make these relationships difficult to recognize. Therefore, published models based on maceral composition alone must be used with great caution. Lipid compositions, even from lipid-poor low-rank coals, can provide important information about depositional environments and paleoclimate, especially if combined with the results of organic petrography and paleontological studies. Just as sulfur derived from seawater provides environmental clues, the ratios of two particularly relevant trace elements rather than a single trace element can be used to interpret peat depositional environments. Epigenetic minerals, as well as their corresponding chemical compositions should not be used for such a purpose; similarly, resistant terrigenous minerals deposited during peat accumulation in many cases should be used with considerable caution. The interactions of the biota present in the peat-forming ecosystem, often determined using palynological and geochemical proxies, and their interpretation in the context of geography and paleoclimate are important means for deciphering peat depositional environments. Overall, a combination of evidence from geochemistry, mineralogy, palynology, and petrology of coal and from stratigraphy, sedimentology, and sedimentary facies of related rocks is necessary for accurate and comprehensive determination of depositional environments. The need for interdisciplinary studies is underscored by peat compositional properties, which have been greatly affected by various processes during the syngenetic, diagenetic or epigenetic stages of coal formation. [ABSTRACT FROM AUTHOR]