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Poor growth of black spruce (Picea mariana (Mill.) BSP) has been associated with the presence of Ledum groenlandicum L. (Ledum) on some sites in the eastern boreal forest in Canada. To increase black spruce productivity on lowland sites, a study was carried out to test the effect of mechanical control of Ledum (by clipping) on black spruce growth on forested peatland in northwestern Quebec. We compared the growth and foliar nutrient concentrations of advance-regeneration black spruce seedlings with and without Ledum control. Contrary to our expectations, our results showed that 3-year control of aboveground competition by Ledum decreased rather than increased black spruce growth and had no effect on foliar nutrient concentrations. Ledum grows on a variety of site types; therefore, the mere presence of this species does not necessarily indicate that there will be a problem with conifer regeneration (growth and germination). [ABSTRACT FROM AUTHOR]

This systematic literature review (SLR) provides a comprehensive overview of remote sensing (RS) applications in northern peatlands from 2017 to 2022, utilising various platforms, including in situ, UAV, airborne, and satellite technologies. It addresses the challenges and limitations presented by the sophisticated nature of northern peatland ecosystems. This SLR reveals an in-creased focus on mapping, monitoring, and hydrology but identifies noticeable gaps in peatland degradation research. Despite the benefits of remote sensing, such as extensive spatial coverage and consistent monitoring, challenges persist, including high costs, underexplored areas, and limitations in hyperspectral data application. Fusing remote sensing data with on-site research offers new insights for regional peatland studies. However, challenges arise from issues like the cost of high-resolution data, coverage limitations, and inadequate field validation data in remote areas. This review suggests refining methodologies, validating with high-resolution data, and addressing these limitations for future research. [ABSTRACT FROM AUTHOR]

Northern peatlands are substantial sinks of carbon (C), yet the sources of carbon dioxide (CO2) emitted from peatlands are largely unknown. Since the relationship between roots and peat in C cycling is important, vascular plants growing on the surface of peat deposits should influence CO2 efflux from the peat surface and the overall C balance in peatlands. In our study, 30-cm peat cores were removed from an ombrotrophic bog in boreal, continental western Canada. Surface vegetation in the cores remained intact and included a continuous bryophyte cover dominated by Sphagnum fuscum. In addition, some cores were collected such that either ericaceous shrubs (Ledum groenlandicum) or sedges (Eriopho rum vaginatum) were present. We investigated how the presence of each vegetation type influenced soil respiration and the microbial mineralization of root exudates using a pulse 14C labeling of vegetation in the intact peat cores. The role of root biomass and root respiration in CO2 emission and C allocation was quantified for each type of vegetation and compared through both measurement and modeling. Our results show that vascular plants contributed 35-57% of total CO2 efflux from the peat surface, primarily derived from rhizosphere processes, including root respiration as well as microbial mineralization of root exudates. The mineralization of root exudates contributed 14-53 μmol C-CO2∙m-2d-1 (17- 24% of total) to CO2 efflux, depending on vegetation type and moisture conditions. The type of vegetation present did not influence the total amount of photosynthetic fixation over the course of the study, but did affect how C was allocated within and between both the aboveground and belowground components of the peat column. [ABSTRACT FROM AUTHOR]

Seismic lines are cleared corridors for the location mapping of subsurface bitumen. After use, the lines can be left to regenerate naturally with varying success. Wildfires, another prominent disturbance in the Boreal region, are propagated by continuous fuel distribution (coarse/fine), meteorological variables (e.g., wind speed, temperature, and precipitation), and the moisture content of the fuel and soil. However, little is known about seismic lines and the potential risk and severity of wildfires. This work presents a case study of wildfire variables on two paired (seismic line and adjacent natural area) sites near Fort McMurray, Alberta, Canada. Wind speed was increased on seismic lines, and the dominant wind direction changed. Higher precipitation, air temperature, and soil moisture and reduced water table depths were observed on seismic lines. Coarse fuel distribution was not continuous on seismic lines; however, fine fuels were. Although the Fire Weather Index (FWI) indicated an enhanced wildfire potential on one line (NS orientation), peat smouldering and ignition models (Hcomb/Hign) showed increased smouldering potential on both seismic lines compared to adjacent natural areas. Future work should focus on expanding the diversity of seismic line characterization, working towards the landscape-scale modelling of these variables. [ABSTRACT FROM AUTHOR]

Summary: Ericaceous shrubs adapt to the nutrient‐poor conditions in ombrotrophic peatlands by forming symbiotic associations with ericoid mycorrhizal (ERM) fungi. Increased nutrient availability may diminish the role of ERM pathways in shrub nutrient uptake, consequently altering the biogeochemical cycling within bogs.To explore the significance of ERM fungi in ombrotrophic peatlands, we developed the model MWMmic (a peat cohort‐based biogeochemical model) into MWMmic‐NP by explicitly incorporating plant‐soil nitrogen (N) and phosphorus (P) cycling and ERM fungi processes. The new model was applied to simulate the biogeochemical cycles in the Mer Bleue (MB) bog in Ontario, Canada, and their responses to fertilization.MWMmic_NP reproduced the carbon(C)–N–P cycles and vegetation dynamics observed in the MB bog, and their responses to fertilization. Our simulations showed that fertilization increased shrub biomass by reducing the C allocation to ERM fungi, subsequently suppressing the growth of underlying Sphagnum mosses, and decreasing the peatland C sequestration. Our species removal simulation further demonstrated that ERM fungi were key to maintaining the shrub–moss coexistence and C sink function of bogs.Our results suggest that ERM fungi play a significant role in the biogeochemical cycles in ombrotrophic peatlands and should be considered in future modeling efforts. See also the Commentary on this article by Barel & Robroek, 238: 5–7. [ABSTRACT FROM AUTHOR]

Northern peatlands are globally important long‐term sinks of carbon due to their predominantly saturated conditions. However, these ecosystems are expected to become drier with climate change, potentially leading to shrubification. As such, the response of the shrubification–evapotranspiration (ET) feedback may be of critical importance to future peatland energy, water and carbon dynamics. We examined the effect of multi‐decadal peatland water table (WT) alteration at three adjacent sites with increasing depth to WT (WET, INTermediate, and DRY). In order to better understand the WT–shrubification–ET feedback, we measured peatland vegetation composition, microtopography and ET partitioning, where ET was measured at the ecosystem, microform, and leaf level using eddy covariance (EC), chambers and porometry, respectively. Averaged across microforms and WT treatments, there was a difference in the median measured leaf resistance (rleaf) between plant functional types ranging from 213 s m−1 for erect dwarf shrubs, 325 s m−1 for graminoids/sedges, and 520 s m−1 for prostrate dwarf shrubs. Scaled based on LAI, the low rleaf of erect dwarf shrubs dominated hummocks, where sites with a higher proportion of hummocks had lower median canopy resistance (rv) of 141, 133 and 130 s m−1 at the WET, INT and DRY sites respectively. Nevertheless, ET was highest at the WET site and similar between the INT and DRY sites, with greater evaporation from the moss surface at the WET site. Porometry and EC data along with a three‐source model were used to independently assess the evaporative contribution from the moss surface, which ranged from 17% to 40%. For moderate and persistent changes in WT from land‐use or climate change, our results suggest vegetation succession is minimal, but the microtopographic development and the concomitant differences in LAI for the various plant functional types is key to understanding changes in total ET and partitioning. [ABSTRACT FROM AUTHOR]

Boreal peatlands of Alberta (Canada) are heavily dissected by a large network of linear disturbances, including seismic lines used for Oil and Gas exploration. Edge effects resulting from these linear disturbances can increase their footprint and affect wildlife habitat, including the quality and quantity of plant and lichen forage. In 2012, seismic line restoration became a priority in Alberta, under the realm of restoration of habitat of threatened boreal woodland caribou. More accurate understanding of biotic and abiotic interactions leading to edge effects can be important in choosing appropriate restoration practices and prompting natural regeneration. We assessed the extent of edge effects of seismic lines on the adjacent boreal peatland near Peace River, northwestern Alberta. We compared plant and lichen community composition and environmental conditions on seismic lines and along 22 transects, which extended perpendicularly 75 m into the peatland from both lines edges. Soil moisture and light were higher on the lines, but frozen ground was less frequent than in the adjacent peatland. Seismic lines were also subsided by approximately 1.2 cm. Lichens were less abundant in the 2–25 m zone from the edge—indicating edge effects. On the lines, Sphagnum constituted a nearly 100% cover while lichens, trees, herbs, and other bryophytes were less abundant than in the peatland. We demonstrate how knowledge of edge effects on plants and lichens could be applied in assessing caribou habitat quality based on forage availability and predation risk, and how such knowledge could inform restoration practices of seismic lines in peatlands. [ABSTRACT FROM AUTHOR]

A checklist of the oribatid mite species from two boreal fens in Northern Ontario, Canada is presented. 174 peat soil samples, collected between 2015–2020, yielded a heterogeneous assemblage of 80 species, 57 genera and 33 families. Species richness and diversity were significantly higher in a Sphagnum-dominated fen (69 species) compared to a Carex-dominated fen (51 species), and although 40 species were found at both sites, overall composition was significantly different between the two sites. We also present an update to the seminal work of Behan-Pelletier and Bissett (1994) on Oribatida of Canadian peatlands with 45 new species records for peatlands. Records for the parthenogenetic families Brachychthoniidae Thor, 1934 and Suctobelbidae Jacot, 1938 were considerably expanded, but other families such as Punctoribatidae, Thor, 1937 remain poorly represented in Canadian peatlands. Taken together, species richness estimates range from 86–105 species based on our sampling and the number of undescribed species recorded suggests that the oribatid mite fauna still need further examination to encompass their actual biodiversity in peatlands. We report that the oribatid mite fauna of Canadian peatlands comprise 186 species that includes all published records as of February 2021 and species presented here. [ABSTRACT FROM AUTHOR]

Melting seasonal ground ice (SGI) in western Boreal Plains (WBP) peatlands can reduce the available energy at the surface by reducing potential evapotranspiration (PET). PET often exceeds annual precipitation in the WBP. Including this effect in hydrological models may be important in assessing water deficits. However, SGI melt and the timing of ice‐free conditions vary spatially, which suggests PET spatial variability could be influenced by SGI. Understanding this potential linkage can help improve site scale PET in peatland hydrological models. The objectives of this paper were (a) to quantify the effect of ice thickness and melt rate on peatland PET; (b) quantify the spatial variability of SGI thickness and melt rate across spatial scales; and (c) assess how/if spatial variability in SGI thickness/melt rate affects site scale PET. Results from the sensitivity analysis indicated that SGI thickness had a bigger impact on reducing PET compared with the melt rate. Two SGI thickness values were used that were observed on site: 0.32 m, which was measured in a more treed area, and 0.18 m, which was in a more open area. The 0.32 m had an average PET reduction of 14 mm (±0.7), over the month of May, compared with 9 mm (±1 mm) when there was 0.18 m of SGI, which are 13.7 and 8.8% reductions, respectively. SGI thickness and melt rate, both exhibited large‐ and small‐scale spatial variability. At the large scale, spatial patterns in SGI thickness appeared to be influenced by extensive shading from the adjacent hillslopes. Small scale, SGI thickness may be a function of tree proximity and the snowpack. Finally, net radiation, rather than SGI, appeared to be the main driver behind PET spatial variability. This work enhances our conceptual understanding of the role of SGI in WBP peatlands. Future work can use the findings to better inform peatland hydrological models, allowing for better representation of peatlands in regional‐scale models. [ABSTRACT FROM AUTHOR]

Boreal peatlands represent a significant global store of soil carbon, which are subject to increasing natural and anthropogenic disturbance. Wildfire is the single largest disturbance to boreal forest and wetlands annually. Critical to the long‐term carbon storage function in peatlands is the (re‐)establishment of a near‐surface water table following wildfire. This has been recently shown to in part be facilitated by post‐fire reductions in water losses via evapotranspiration (ET). However, reduced ET may also have cascade impacts on other ecohydrological processes in recovering peatlands, such as a reduction in carbon sequestration. To investigate the linked cycles of evaporative loss and carbon exchange in burned peatlands, the burned and unburned peatlands in Alberta, Canada, were instrumented with eddy covariance systems to monitor continuous fluxes of energy, carbon dioxide, and water vapour, over two summer seasons (2013 and 2014; 2–3 years post‐burn). The burned site showed significant changes to respiration and productivity and a shift in the partitioning of available energy (significantly larger Bowen ratio; mean values of 1.19 and 1.10 at the burned and unburned sites, respectively), as well as a significant reduction in ET rates. Decreases in respiration did not offset the decrease in primary productivity, and the burned site was significantly less productive than the reference site on a net production basis for the available data period. This provides direct observations of ET and CO2 fluxes at a novel ecosystem scale to show the impacts of fire on short‐term (2–3 years) post‐burn ecosystem ecohydrological function. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geophysical Research. Atmospheres is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The uppermost portion of the peat profile, an area of active diagenetic processes, is exceedingly important for understanding peatland dynamics and the diagenesis and geochemistry of atmospherically-deposited materials. We investigated high resolution carbon (C) accrual and peat decomposition rates at two Sphagnum-rich ombrotrophic bogs and one fen in northern Minnesota, USA by analyzing 1 cm increments from 30 cm thick intact frozen blocks of peat soil. We conducted radiocarbon analysis of Sphagnum cellulose to determine peat age and net C accumulation at each depth interval. Calibrated peat ages were determined using CALIBomb and a compilation of calibration datasets for the pre-bomb period. We fit data with a negative exponential accumulation model and used model-derived parameters to estimate net primary productivity (NPP) and a peat decomposition rate constant k. FTIR spectroscopy and C:N were used to derive humification indices and to chemically characterize the peat. NPP ranged from 180 to 266 g C m−2 year−1, k ranged from 0.015 to 0.019 year−1. Net C accumulation rates ranged from 112 to 174 g C m−2 year−1 at 25 years and 70 to 113 g C m−2 year−1 at 50 years. Mass loss was up to 55% during the first 50 years of peat accumulation. Decomposition is greater at depth in the bogs—where 25 cm of peat correspond to 55 years of peat accumulation—than in the fen, where peat age is approximately 25 years at 25 cm depth. Information on fine-scale variations in peat mass decomposition and loss across ombrotrophic bogs and a fen help interpret other diagenetic processes in peatlands. [ABSTRACT FROM AUTHOR]

Peatlands store substantial amounts of carbon and are vulnerable to climate change. We present a modified version of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model for simulating the hydrology, surface energy, and CO2 fluxes of peatlands on daily to annual timescales. The model includes a separate soil tile in each 0.5° grid cell, defined from a global peatland map and identified with peat-specific soil hydraulic properties. Runoff from non-peat vegetation within a grid cell containing a fraction of peat is routed to this peat soil tile, which maintains shallow water tables. The water table position separates oxic from anoxic decomposition. The model was evaluated against eddy-covariance (EC) observations from 30 northern peatland sites, with the maximum rate of carboxylation (Vcmax/ being optimized at each site. Regarding short-term day-to-day variations, the model performance was good for gross primary production (GPP) (r2 =0.76; Nash-Sutcliffe modeling efficiency, MEF=0.76) and ecosystem respiration (ER, r2 =0.78, MEF=0.75), with lesser accuracy for latent heat fluxes (LE, r2 =0.42, MEF=0.14) and and net ecosystem CO2 exchange (NEE, r2 =0.38, MEF=0.26). Seasonal variations in GPP, ER, NEE, and energy fluxes on monthly scales showed moderate to high r2 values (0.57-0.86). For spatial across-site gradients of annual mean GPP, ER, NEE, and LE, r2 values of 0.93, 0.89, 0.27, and 0.71 were achieved, respectively. Water table (WT) variation was not well predicted (r2 < 0.1), likely due to the uncertain water input to the peat from surrounding areas. However, the poor performance of WT simulation did not greatly affect predictions of ER and NEE. We found a significant relationship between optimized Vcmax and latitude (temperature), which better reflects the spatial gradients of annual NEE than using an average Vcmax value. [ABSTRACT FROM AUTHOR]

Peatlands of the Western Boreal Plains are under stress from oil and gas development and associated infrastructure such as road construction and removal. An improved understanding of nutrient cycling and atmospheric carbon dioxide (CO2) exchange interactions in peatlands can assist in recommending best management practices to industry to minimize the ecohydrological disturbance footprint of road features. Peat nutrient (nitrogen, N, and phosphorus, P) supply, net mineralization, groundwater concentrations, and peatland-atmosphere CO2 exchange rates were quantified within a poor fen bisected by a semi-permanent road located in the Athabasca Oil Sands region of Alberta, Canada, over one growing season. Results demonstrate that the road impeded groundwater movement across the site; however, water table and moisture differences were minimal, likely due to the unusually wet season. No clear impacts of the road on nutrient dynamics were observed, but subtle differences in productivity and respiration resulted in significantly lower net CO2 sequestration (net ecosystem exchange) on the down-flow side of the road. Differences in vegetation composition between sides of the road were apparent and likely indicate longer-term moisture differences at the site. Elevated rates of productivity and respiration coincided with a seasonal change in the relative supplies of N and P (increased N : P ratios), suggesting that the relative availability of N versus P may be important to CO2 fluxes in Western Boreal Plains peatlands. Collectively, these findings demonstrate the need to capture interactions between hydrology, ecology and nutrient biogeochemistry when evaluating peatland carbon cycling response to road disturbances across this region. [ABSTRACT FROM AUTHOR]

Peatlands encode information about past vegetation dynamics, climate, and microbial processes. Here, we used γ15N and γ 13C patterns from 16 peat profiles to deduce how the biogeochemistry of the Marcell S1 forested bog in northern Minnesota responded to environmental and vegetation change over the past -10 000 years. In multiple regression analyses, γ 15N and γ 13C correlated strongly with depth, plot location, C = N, %N, and each other. Correlations with %N, %C, C = N, and the other isotope accounted for 80% of variance for γ 15N and 38% of variance for γ 13C, reflecting N and C losses. In contrast, correlations with depth and topography (hummock or hollow) reflected peatland successional history and climate. Higher γ 15N in plots closer to uplands may reflect upland-derived DON inputs and accompanying shifts in N dynamics in the lagg drainage area surrounding the bog. The Suess effect (declining γ 13CO2 since the Industrial Revolution) lowered γ 13C in recent surficial samples. High γ 15N from -35 to -55 cm probably indicated the depth of ectomycorrhizal activity after tree colonization of the peatland over the last 400 years, as confirmed by the occasional presence of wood down to -35 cm depth. High γ 13C at -4000 years BP (-65 to -105 cm) could re- flect a transition at that time to slower rates of peat accumulation, when 13C discrimination during peat decomposition may increase in importance. Low γ 13C and high γ 15N at -213 and -225 cm (-8500 years BP) corresponded to a warm period during a sedge-dominated rich fen stage. The above processes appear to be the primary drivers of the observed isotopic patterns, whereas there was no clear evidence for methane dynamics influencing γ 13C patterns. [ABSTRACT FROM AUTHOR]

Associated with the development of the oil sands resource in northern Alberta, Canada are elevated emissions of NO and SO from diesel-fueled vehicle and upgrader stack emissions. Ultimately these emissions are returned to regional terrestrial and aquatic ecosystems in the form of elevated atmospheric N and S deposition. About 30 % of the regional landscape is covered with peatlands, including ombrotrophic bogs that receive nutrient inputs solely from the atmosphere. From 2009 to 2014 we examined the effects of N and S deposition on Sphagnum fuscum growth and on recent net accumulation of C, N, and S in peat in six bogs, located between 11 and 251 km from the oil sands industrial center. Averaged across all sites and years, average deposition of NH -N, NO -N, DIN, SO -S, Ca, Mg, and ortho-P was 0.52, 0.64, 1.17, 7.70, 10.04, 3.29, and 0.15 kg ha year. Deposition of NO -N, DIN, SO -S, Ca, and Mg decreased exponentially with distance from the industrial center. Averaged across all sites and years, vertical growth and NPP of S. fuscum was 16.6 ± 0.6 mm and 259 ± 9 g m per growing season, increasing exponentially with proximity to the industrial center. Correlations suggested that climatic factors, and in particular late growing season precipitation and the growing season Aridity Index (potential evapotranspiration to precipitation ratio) may be more important than the chemistry of atmospheric deposition in affecting S. fuscum growth. Across all sites and years, net C, N, and S accumulation in peat over the most recent 25 years averaged 67, 1.29, and 0.30 g m year and increased with proximity to the industrial center. Over the past 25-50 years, net C, N, and S accumulation in peat was lower than in surface peat, with only net S accumulation exhibiting an increase with proximity to the industrial center. In a region where bogs have persisted on the landscape for millennia with low atmospheric deposition of elements, changing precipitation chemistry, and in particular elevated deposition of N, S, Ca and Mg, related to oil sands development is influencing bog function, as evidenced by S. fuscum growth and biogeochemical responses. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent studies have suggested that the hydrologic connectivity of northern headwater catchments is likely controlled by antecedent moisture conditions and land cover patterns. A water storage model ( EWS), based on water levels ( WLs), specific yield ( Sy) and surface elevation ( SE) changes, was compared with a basic water budget of a small, boreal, patterned fen (13 ha) during the ice-free period. Results showed that the EWS model reproduced well storage variations derived from the water budget. These results suggest that storage variations can be properly represented by the fluctuations of WLs when we consider the heterogeneous soil properties. However, storage deviations occurred at the daily scale and could be explained by a lack of information on water retention in unsaturated layers, canopy interceptions and preferential flows. Despite the significant impact of SE changes on the different peatland cover storage budgets (strings and lawns), using Sy mean values had a low impact on storage estimations. This can be explained by the large proportion of pools and high WLs throughout the fen. At the fen scale, high storage in the pools seemed to reduce the Sy difference between strings and lawns. The results of this study provide new insights about the complex hydrological behaviour of northern catchments and allow for conceiving new hydrological modelling perspectives. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Changes in vegetation composition due to nitrogen deposition may influence the role of peatlands in the carbon cycle. The impact of nitrogen (N) on vegetation composition of the Mer Bleue Bog (Ontario) and the underlying mechanisms were studied using a coupled carbon (C) and nitrogen wetland model (PEATBOG). The model was applied to data from a long-term nutrient fertilization experiment and the results were compared with the observed C and N pools in plants, peat, and soil water after 8 years of fertilization with 1.6, 3.2, and 6.4 gN m y and additional phosphorus and potassium. The evaluated model was employed to simulate the vegetation dynamics in the peatland fertilized with different loads and concentrations of N. The model suggested a shift in plant functional types from moss-shrub dominated to graminoid dominated with increasing N load. Suppression of mosses by N fertilization was mitigated by daily deposition of N at a low concentration. Mosses became extinct in the simulations only when the concentration and load of N deposition were high, corroborating empirical results from the fertilization experiment. Tracking the deposited N in the system, the model indicated that it was primarily sequestered in the peat. Dissolved N concentrations in peat and export from the bog increased with N load and decreased with N concentration, leading to higher N uptake by vascular plants. The results further suggested that the observed detrimental effect of N on mosses was most likely due to toxicity caused by N uptake exceeding N assimilation. Exposure of mosses to high N concentrations in precipitation and evaporating water on moss tissues is thus a factor that needs attention when considering critical loads of N deposition on peatlands. [ABSTRACT FROM AUTHOR]

We examined the water balance of a forested ombrotrophic peatland and adjacent burned peatland in the boreal plain of western Canada over a 3-year period. Complete combustion of foliage and fine branches dramatically increased shortwave radiation inputs to the peat surface while halting all tree transpiration at the burned site. End-of-winter snowpack was 7-25% higher at the burned site likely due to decreased ablation from the tree canopy at the unburned site. Shrub regrowth at the burned site was rapid post-fire, and shading by the shrub canopy in the burned site approached that of the unburned site within 3 years after fire. Site-averaged surface resistance to evaporation was not different between sites, though surface resistance in hollows was lower in the burned site. Water loss at both burned and unburned sites is largely driven by surface evaporative losses. Evaporation at the burned site marginally exceeded the sum of pre-fire transpiration and interception at the unburned site, suggesting that evapotranspiration during the growing season was 20-40 mm greater at the burned peatland. Although the net change in water storage during the growing season was largely unchanged by fire, the lack of low-density surface peat in the burned site appears to have decreased specific yield, leading to greater water table decline at the burned site despite similar net change in storage. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ecosystems around the world are being subjected to numerous human disturbances. Climate change and land degradation are the most obvious of these disturbances and have received much attention. However, easily overlooked, indirect disturbances can also alter ecosystem structure and function. Dust deposition is a prime example of an easily overlooked disturbance process. We hypothesized that historic European settlement and land-clearance in eastern North America led to widespread wind erosion of upland soils and subsequent dust deposition onto otherwise undisturbed peatlands, potentially fertilizing these naturally nutrient-poor ecosystems and causing shifts in plant communities. We tested these hypotheses by analyzing 11 peat profiles collected across a broad region of eastern North America. We documented a strong correlation between the concentrations of Ambrosia pollen grains and microscopic mineral particles, interpreting this as a signal of dust deposition coincident with European settlement and land-clearance. Analysis of Sphagnum macrofossils revealed substantial site-to-site variability in both the degree and the direction of ecological response to dust deposition, but suggested that increasing magnitude of dust deposition increased the likelihood of a decline in the relative abundance of Sphagnum. Results also suggested that raised bogs were more sensitive to dust deposition than kettle peatlands. We conclude that European settlement and land-clearance resulted in widespread dust deposition on peatlands, leading to ecological changes in some of these ecosystems, and leaving behind a coherent dust horizon in the late-Holocene peatland stratigraphy of eastern North America. This easily overlooked indirect disturbance process could be ongoing today in areas of widespread soil disturbance and could potentially further alter dust-receiving ecosystems. [ABSTRACT FROM AUTHOR]

Subarctic peatlands are increasingly faced with disturbances from resource extraction industries. Their rehabilitation is being required through government regulation, and backed by financial guarantees. A three-year field experiment was conducted to test a modification of existing peatland rehabilitation protocols on winter road clearances in subarctic peatlands of the Hudson Bay Lowland. The experiment was conducted on severely disturbed sections of winter roads with extensive cut hummocks. Sphagnum fragments were not spread on bare peat surfaces, contrary to existing protocols, because of the close proximity to propagules in vast and adjacent, undisturbed peatlands. Factorial combinations of microclimate amelioration (straw mulch) and phosphorus fertilization were applied, as in existing protocols. Rock phosphate fertilization and straw mulch did not increase the recolonization of Sphagnum nor of other bryophytes, lichens or vascular plants. After three years, Sphagnum remained almost absent and bare peat was colonized mostly by lichens and bryophytes typical of disturbed peat surfaces. The spreading of fragments on top of severely disturbed surface peats appears to be required in order to rehabilitate peatlands, even when extensive undisturbed peatlands are found nearby. [ABSTRACT FROM AUTHOR]

The frequency and intensity of drought is projected to increase within the boreal region under future climatic conditions. Peatlands are widely considered to regulate water loss under drought conditions, increasing surface resistance ( rs) and reducing evaporative losses. This maintains peat moisture content, increasing the resilience of these globally important carbon stores. However, the magnitude and form of this important negative feedback response remains uncertain. To address this, we monitored the response of rs to drought within four peat cores under controlled meteorological conditions. When the water-table was dropped to a depth of 0.30 m and the humidity reduced to ≤40%, a step shift in rs from ~50 s m-1 up to 1000 s m-1 was observed within burned and unburned peat, which virtually shuts down evaporation, limiting water loss. We show that measured near-surface tension cannot be used to directly calculate this transition in peat surface resistance. However, empirical relationships that account for strong vertical variations in tension through the near-surface and/or disequilibrium between pore air and near-surface pore water pressure provide the potential to incorporate this negative feedback response into peatland ecohydrological models. Further observations are necessary to examine this response under dynamic atmospheric conditions. We suggest that the link between surface temperature and evaporation provides potential to further examine this feedback in either burned peatlands or peatlands with a low vascular vegetation cover. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

About 0.3 million km of boreal forests and peatlands and their soils have been flooded through the creation of hydroelectric reservoirs. To establish the effect of flooding on dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) production, we incubated six sample types of boreal forest and peatland soils and litters for 15 weeks under flooded (anoxic and suboxic) and non-flooded (oxic) conditions at three temperatures (4, 12, and 22 °C). Water was sampled at 3-week intervals and analyzed for DOC and TDN concentration. Cumulative DOC and TDN production ranged widely: from 4.4 to 146.2 mg C g C for DOC and 4.4 to 112.2 mg N g N for TDN under flooded conditions, and from 1.3 to 16.6 mg C g C for DOC and 0.7 to 8.5 mg N g N for TDN under non-flooded conditions. Cumulative DOC and TDN production was greater under flooded than non-flooded conditions for all sample types with flooded:non-flooded ratios averaging 10.6 for DOC and 9.5 for TDN. Within the flooded treatments, anoxic conditions produced more cumulative DOC and TDN than suboxic conditions, with average anoxic:suboxic ratios of 1.3 and 5.8 for DOC and TDN, respectively. Raising temperatures increased cumulative DOC and TDN production marginally under both flooded and non-flooded conditions as the average ratios for 22:12 and 12:4 °C were 1.1 for DOC and 1.2 for TDN. Generally, more DOC and TDN were released from litters than soils under both the flooded and non-flooded incubations, with litter:soil ratios averaging 8.5 for DOC and 2.1 for TDN. DOC:TDN ratio was generally higher in the solutions than in the original sample, particularly in the litters. This study thus indicated that DOC and TDN production was largely affected by flooding regime, O concentration, and substrate characteristics and less affected by temperature. [ABSTRACT FROM AUTHOR]

When restoring ecosystems, the simple removal of stresses causing degradation may seem preferable over other more costly and time consuming approaches. However, some restoration techniques can be implemented at reasonable cost and with increased efficiency in certain cases. We examined the successional trajectories of vegetation within abandoned block-cut peatlands in a major peat-producing region of Eastern Canada to evaluate whether the use of rewetting as a restoration technique can assist in the recovery of a typical bog plant community dominated by Sphagnum compared to spontaneous recolonization alone. We surveyed a total of 55 trenches in 6 peatlands twice, ~25 and ~35 years after the cessation of peat extraction. Canonical ordinations evidenced a generalized process of afforestation during the decade studied, partially driven by agricultural drainage in the surrounding landscape. Plant communities were dominated by ericaceous shrubs that hampered the spontaneous recovery of a Sphagnum-dominated system typical of bogs in the short and medium-term. Three of the six peatlands surveyed were partially restored by blocking drainage ditches. There, we surveyed plant composition in rewetted (28) and non-rewetted (26) trenches and observed that rewetting mitigated the increase in tree dominance, decreased the dominance by ericaceous shrubs, and favored the spread of non-vascular species with a wet habitat preference (notably Sphagnum species from the Cuspidata section). We conclude that the use of low intervention restoration techniques in block-cut bogs, such as the blockage of former drainage ditches, can re-orient undesired vegetation trajectories driven by spontaneous recolonization alone. [ABSTRACT FROM AUTHOR]

Northern peatland water table position is tightly coupled to carbon (C) cycling dynamics and is predicted to change from shifts in temperature and precipitation patterns associated with global climate change. However, it is uncertain how long-term water table alterations will alter C dynamics in northern peatlands because most studies have focused on short-term water table manipulations. The goal of our study was to quantify the effect of long-term water table changes (~80 years) on gaseous C fluxes in a peatland in the Upper Peninsula of Michigan. Chamber methods were utilized to measure ecosystem respiration (ER), gross primary production (GPP), net ecosystem exchange (NEE), and methane (CH) fluxes in a peatland experiencing levee induced long-term water table drawdown and impoundment in relation to an unaltered site. Inundation raised water table levels by approximately ~10 cm and resulted in a decrease in ER and GPP, but an increase of CH emissions. Conversely, the drained sites, with water table levels ~15 cm lower, resulted in a significant increase in ER and GPP, but a decrease in CH emissions. However, NEE was not significantly different between the water table treatments. In summary, our data indicates that long-term water table drawdown and inundation was still altering peatland gaseous C fluxes, even after 80 years. In addition, many of the patterns we found were of similar magnitude to those measured in short-term studies, which indicates that short-term studies might be useful for predicting the direction and magnitude of future C changes in peatlands. [ABSTRACT FROM AUTHOR]

We monitored CO2 and CH4 fluxes using eddy covariance from 19 May to 27 September 2011 in a poor fen located in northern Michigan. The objectives of this paper are to: (1) quantify the flux of CH4 from a sub-boreal peatland, and (2) determine which abiotic and biotic factors were the most correlated to the flux of CH4 over the measurement period. Net daily CH4 fluxes increased from 70 mgCH4 m-2 d-1 to 220 mgCH4 m-2 d-1 from mid May to mid July. After July, CH4 losses steadily declined to approximately 50 mg CH4 m-2 d-1 in late September. During the study period, the peatland lost 17.4 gCH4 m-2. Both abiotic and biotic variables were correlated with CH4 fluxes. When the different variables were analyzed together, the preferred model included mean daily soil temperature at 20 cm, daily net ecosystem exchange (NEE) and the interaction between mean daily soil temperature at 20 cm and NEE (R2 = 0.47, p value <0.001). The interaction was important because the relationship between daily NEE and mean daily soil temperature with CH4 flux changed when NEE was negative (CO2 uptake from the atmosphere) or positive (CO2 losses to the atmosphere). On days when daily NEE was negative, 25% of the CH4 flux could be explained by correlations with NEE, however on days when daily NEE was positive, there was no correlation between daily NEE and the CH4 flux. In contrast, daily mean soil temperature at 20 cm was poorly correlated to changes in CH4 when NEE was negative (17 %), but the correlation increased to 34% when NEE was positive. The interaction between daily NEE and mean daily soil temperature at 20 cm indicates shifting environmental controls on the CH4 flux throughout the growing season. [ABSTRACT FROM AUTHOR]

Open top chambers (OTCs) and infrared (IR) lamps have been widely used for experimentally warming ecosystems, especially in high latitude and alpine regions. The efficacy of OTCs and IR lamps is variable, yet there has not been a direct, experimentally controlled comparison of these warming methods. We, therefore, implemented a factorial study in a northern Michigan peatland to test how warming and microtopography interacted to affect micrometeorological parameters and CO and CH flux rates. IR lamps significantly warmed the soil (5 cm depth; P < 0.05) by 1.4 and 1.9°C in 2009 and 2010, respectively, with the majority of warming occurring during nighttime hours. OTCs did not provide any long-term warming increase compared to control plots, which is contrary to OTC studies at high latitudes. By investigating diurnal heating patterns and micrometeorological variables, we determined that OTCs were not achieving strong daytime heating peaks and were often cooler than controls during nighttime hours. Temperate day-length, cloudy and humid conditions, and latent heat loss were factors that may have inhibited OTC warming. Warming treatments created mixed effects on gas flux components. Within drier, hummock plots, IR lamps significantly increased gross ecosystem production (GEP) but not ecosystem respiration (ER), whereas OTCs had no effect on GEP or ER in hummocks. In wetter, lawn plots, warming treatments had no effect on CO flux or CH flux. We show here that IR lamps are more effective than OTCs for studying how temperate peatlands may respond to increased temperatures. [ABSTRACT FROM AUTHOR]

Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem. [ABSTRACT FROM AUTHOR]

Human-induced disturbances and climate-driven warming have resulted in unprecedented permafrost thaw in the zone of discontinuous permafrost. In a peatland environment south of Fort Simpson, NWT, we study the contribution of increases in incoming radiation to the ground surface, caused by removal of the tree canopy along linear disturbances, to changes in the ground thermal regime. A physically based understanding of thaw processes along linear disturbances is required in order to better understand the slow recovery of lines in this environment and to be able to efficiently reduce this impact during future resource exploration. The impact of increases in incoming radiation are examined through the development of a model (seismic incoming radiation model) to quantify these inputs, which are then used to drive the one-dimensional coupled atmospheric-surface-subsurface model COUP. Results of this study show that incoming radiation (shortwave + longwave) is increased by up to 11% in a typical cutline compared to an undisturbed canopy. Relative to potential changes in near-surface soil moisture, these increases in radiation do not appear to be an important control of permafrost thaw along linear disturbances. Field observations confirm that increased permafrost thaw on disturbances often occur irrespective of variations in incoming radiation. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Developing objective tools for tracking progress of restored sites is of general concern. Here, we present an innovative approach based on principal response curves (PRC) and species classification according to their preferential habitats to monitor changes in community composition. Following large-scale restoration of a cut-over peatland, vegetation was surveyed biannually over 8 years. We evaluated whether the establishing plant communities fell within the range of natural variation. We used both general diversity curves and PRC applied on plant species grouped by preferred habitat to compare restored sites and unrestored sites to a reference ecosystem. After 8 years, diversity and richness differed between the sites, with Forest and Ruderal species more prominent in unrestored sites, and Peatland, Forest, and Wetland species dominant in restored sites. The PRC revealed that the restored site became rapidly dominated by typical peatland plants, the main drivers of temporal changes being Sphagnum rubellum, Pohlia nutans, and Mylia anomala. Some differences remained between the restored and the undisturbed species pools: the former had more herbaceous species associated with wetlands such as Calamagrostis canadensis and Typha latifolia and the latter had more forested species like Kalmia angustifolia throughout the study. PRC revealed to be an efficient tool identifying species driving changes at the community level after restoration. In our case study, examining PRC scores after classifying species according to their preferred habitat allowed to illustrate objectively how restoration promotes target species (associated to peatlands) and how lack of intervention benefits ruderal species. [ABSTRACT FROM AUTHOR]

It is anticipated that a lowering of the water table and reduced soil moisture levels in peatlands may increase peat decomposition rates and consequently affect nutrient availability. However, it is not clear if patterns will be consistent across different peatland types or within peatlands given the natural range of ecohydrological conditions within these systems. We examined the effect of persistent drought on peatland nutrient dynamics by quantifying the effects of an experimentally lowered water table position (drained for a 10-year period) on peat KCl-extractable total inorganic nitrogen (ext-TIN), peat KCl-extractable nitrate (ext-NO), and water-extractable ortho-phosphorus (ext-PO) concentrations and net phosphorus (P) and nitrogen (N) mineralization and nitrification rates at natural (control) and drained microforms (hummocks, lawns) of a bog and poor fen near Québec City, Canada. Drainage (water table drawdown) decreased net nitrification rates across the landscape and increased ext-NO concentrations, but did not affect net N and P mineralization rates or ext-TIN and ext-PO concentrations. We suggest that the thick capillary fringe at the drained peatland likely maintained sufficient moisture above the water table to limit the effects of drainage on microbial activity, and a 20 cm lowering of the water table does not appear to have been sufficient to create a clear difference in nutrient dynamics in this peatland landscape. We found some evidence of differences in nutrient concentrations with microforms, where concentrations were greater in lawn than hummock microforms at control sites indicating some translocation of nutrients. In general, the same microtopographic differences were not observed at drained sites. The general spatial patterns in nutrient concentrations did not reflect net mineralization/immobilization rates measured at our control or drained peatlands. Rather, the spatial patterns in nutrient availability may be regulated by differences in vegetation (mainly Sphagnum moss) cover between control and drained sites and possibly differences in hydrologic connection between microforms. Our results suggest that microform distribution and composition within a peatland may be important for determining how peatland nutrient dynamics will respond to water table drawdown in northern peatlands, as some evidence of microtopographic differences in nutrient dynamics was found. [ABSTRACT FROM AUTHOR]

Winter roads across subarctic peatlands are increasingly being used to access remote communities and resource development camps, yet relatively little is known on their ability to recover after abandonment. We evaluated the natural recovery of winter roads abandoned within 7 years on peatlands in the Hudson Bay Lowland, Canada. We sampled 5 winter roads of increasing age of abandonment and compared surface elevation, microtopography, active layer thickness, species cover, diversity, and composition between winter road clearances and adjacent undisturbed peatland. No differences in surface elevation and hummock-hollow microtopography were detected between road clearances and adjacent peatlands, but clearances had significantly thinner active layer, which persisted at least 7 years after abandonment. The cover of lichens, bryophytes, and vascular plants returned within 5 years to similar levels as in undisturbed peatlands, although species richness per quadrat remained lower and species composition differed. The limited recovery of black spruce on these peatlands and their slow growth indicates that the full recovery of vegetation structure on these road clearances will take decades. Future research should focus on the restoration of a Sphagnum carpet and on the interactions between a shallower active layer and the revegetation of abandoned winter roads. [ABSTRACT FROM AUTHOR]

Accurate quantification of soil-atmosphere gas exchange is essential for understanding the magnitude and controls of greenhouse gas emissions. We used an automatic closed dynamic chamber system to measure the fluxes of CO2 and CH4 for several years at the ombrotrophic Mer Bleue peatland near Ottawa, Canada and found that atmospheric turbulence and chamber deployment period had a considerable influence on the observed flux rates. With a short deployment period of 2.5 min, CH4 flux exhibited strong diel patterns and both CH4 and nighttime CO2 effluxes were highly and negatively correlated with friction velocity as were the CO2 concentration gradients in the top 20 cm of peat. This suggests winds were flushing the very porous and relatively dry near surface peat layers, altering the concentration gradient and resulting in a 9 to 57% underestimate of CH4 flux at any time of day and a 13 to 21% underestimate of nighttime CO2 fluxes in highly turbulent conditions. Conversely, there was evidence of an overestimation of ∼100% of CH4 and nighttime CO2 effluxes in calm atmospheric conditions possibly due to enhanced near-surface gas concentration gradient by mixing of chamber headspace air by fans. These problems were resolved by extending the deployment period to 30 min. After 13 min of chamber closure, the flux rate of CH4 and nighttime CO2 became constant and were not affected by turbulence thereafter, yielding a reliable estimate of the net biological fluxes. The measurement biases we observed likely exist to some extent in all chamber flux measurements made on porous and aerated substrate, such as peatlands, organic soils in tundra and forests, and snow-covered surfaces, but would be difficult to detect unless high frequency, semicontinuous observations are made. [ABSTRACT FROM AUTHOR]

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Natural peatlands are an important source of berries in northern countries. One possible avenue to improve crop yield in natural peatlands is to apply fertilizers, ombrotrophic peatlands being very low in nutrients. In order to reduce the impact of this practice on an otherwise natural habitat, slow-release organic fertilizers might be more appropriate than mineral fertilizers. However, mineralization and dispersion of organic fertilizers in peatlands need to be determined along with their impact on crop yield. In the present study, we focused on cloudberry fruit that despite a high commercial potential is limited by low and variable yield. We thus tested the effect of an organo-mineral fertilizer in two peatlands on nutrient dispersion, plant growth, flowering frequency and fruit yield of cloudberry. The organo-mineral fertilizer, composed of crab and fish meal supplemented with potassium chloride, was applied annually for three years. The treatment was repeated in two natural ombrotrophic peatlands: one covered with lichen and the other a more typical sphagnum bog. The dispersion study indicated very limited dispersion of most nutrients. There was no effect of the fertilizer on cloudberry growth and fruit yield or on the nutrient concentrations of its tissues. We concluded that the fertilizer did not mineralize to sufficient extent. Mineralization of potential organic fertilizers would need to be tested in natural peatlands before being applied to cloudberry patches. [ABSTRACT FROM AUTHOR]

Bauer, I. E. & Vitt, D. H. 2011: Peatland dynamics in a complex landscape: Development of a fen-bog complex in the Sporadic Discontinuous Permafrost zone of northern Alberta, Canada. Boreas, 10.1111/j.1502-3885.2011.00210.x. ISSN 0300-9483. The development of a peatland complex in the Sporadic Discontinuous Permafrost zone of northwestern Alberta, Canada was reconstructed using a series of dated profiles. Peat-forming communities first established c. 10 230 cal. a BP, and by 8000 cal. a BP the site supported monocot fens or marshes in several isolated topographic depressions. Most of the current peatland area initiated between c. 8000 and 4000 cal. a BP, and involved the replacement of upland habitats by shrubby or treed fen and, in some areas, the establishment of Sphagnum on mineral terrain. Ombrotrophic hummock communities had established by c. 7000 cal. a BP, and permafrost was present at 6800 cal. a BP in at least some peat plateau areas. Macrofossil-based reconstructions show considerable local diversity in vegetation succession and permafrost dynamics, with cyclic collapse and aggradation in at least one profile and relative stability in others. Lichen-rich peat is rare in deep-peat plateau cores, and where charcoal was recovered, fire effects on vegetation trajectories varied between cores. Organic matter accumulation was high in the early Holocene and declined after permafrost formation, with low rates especially over the past 4000 years. The site was burned in a wildfire in 1971, and by 1998 permafrost had disappeared from almost all peat plateau areas. In this part of the discontinuous permafrost zone, peat plateaus are likely to be unsustainable under a warming climate. The hydrology and carbon dynamics of former plateau areas following large-scale permafrost degradation require further investigation. [ABSTRACT FROM AUTHOR]

The Mer Bleue peatland is a large ombrotrophic bog with hummock-lawn microtopography, poor fen sections and beaver ponds at the margin. Average growing-season (May-October) fluxes of methane (CH) measured in 2002-2003 across the bog ranged from less than 5 mg m d in hummocks, to greater than 100 mg m d in lawns and ponds. The average position of the water table explained about half of the variation in the season average CH fluxes, similar to that observed in many other peatlands in Canada and elsewhere. The flux varied most when the water table position ranged between −15 and −40 cm. To better establish the factors that influence this variability, we measured CH flux at approximately weekly intervals from May to November for 5 years (2004-2008) at 12 collars representing the water table and vegetation variations typical of the peatland. Over the snow-free season, peat temperature is the dominant correlate and the difference among the collars' seasonal average CH flux is partially dependent on water table position. A third important correlate on CH flux is vegetation, particularly the presence of Eriophorum vaginatum, which increases CH flux, as well as differences in the potential of the peat profile to produce and consume CH under anaerobic and aerobic conditions. The combination of peat temperature and water table position with vegetation cover was able to explain approximately 44% of the variation in daily CH flux, based on 1097 individual measurements. There was considerable inter-annual variation in fluxes, associated with varying peat thermal and water table regimes in response to variations in weather, but also by variations in the water level in peripheral ponds, associated with beaver dam activity. Raised water level in the beaver ponds led to higher water tables and increased CH emission in the peatland. [ABSTRACT FROM AUTHOR]

Information about the impact of nitrogen (N) deposition on the fate of deposited N in peatland ecosystems is lacking. Thus we investigated the fate of experimentally added N in long-term N-fertilized treatments in a Sphagnum-dominated ombrotrophic bog. Fertilization significantly stimulated vascular plant and suppressed Sphagnum and Polytrichum moss growth. N content in peat, mosses, and vascular plants was raised by the fertilizer addition and reached a maximum at 3.2 g m N input level with phosphorus (P) and potassium (K) addition. Most of N was retained in the vegetation and upper 10 cm of the peat. When N deposition equalled 1.6 g m and less, or 3.2 g m N with P and K addition, no inorganic N leaching was observed on the plots. This result indicates that co-fertilization with P and K raised the N retention capacity and that critical N loads with respect to N saturation depend on P and K availability. Most of the deposited N was recovered in the bulk peat, which may be related to a rapid immobilization of inorganic N by microorganisms and mycorrhizal assimilation. Increase of N, P, and K fertilization increased the contribution of vascular plants to N retention significantly and reduced those of mosses. The increase was mainly related to enhanced productivity, vascular biomass and N content in tissues; the reduced retention by mosses resulted from both reduced moss biomass and assimilation. The study shows that the N filter function of ombrotrophic bogs will be influenced by interactions with other nutrients and shifts in plant community structure. [ABSTRACT FROM AUTHOR]

Ombrotrophic peatlands depend on airborne nitrogen (N), whose deposition has increased in the past and lead to disappearance of mosses and increased shrub biomass in fertilization experiments. The response of soil water content, temperature, and carbon gas concentrations to increased nutrient loading is poorly known and we thus determined these data at the long-term N fertilization site Met Bleue bog, Ontario, during a two month period in summer. Soil temperatures decreased with NPK addition in shallow peat soil primarily during the daytime (t-test, p < 0.05) owing to increased shading, whereas they increased in deeper peat soil (t-test, p < 0.05), probably by enhanced thermal conductivity. These effects were confirmed by RMANOVA, which also suggested an influence of volumetric water contents as covariable on soil temperature and vice versa (p < 0.05). Averaged over all fertilized treatments, the mean soil temperatures at 5 cm depth decreased by 1.3 °C and by 4.7 °C (standard deviation 0.9 °C) at noon. Water content was most strongly affected by within-plot spatial heterogeneity but also responded to both N and PK load according to RMANOVA (p < 0.05). Overall, water content and CO2 concentrations in the near-surface peat (t-test, p < 0.05) were lower with increasing N load, suggesting more rapid soil gas exchange. The results thus suggest that changes in bog ecosystem structure with N deposition have significant ramifications for physical parameters that in turn control biogeochemical processes. [ABSTRACT FROM AUTHOR]

Linear infrastructures are known to facilitate the spread of undesirable species in ecosystems. Compared with other types of infrastructure, the role of power line rights-of-way (ROWs) as dispersal vectors remains poorly understood, especially with regard to peatlands. The aim of our study was to evaluate their impacts on the vegetation of ombrotrophic (bog) and minerotrophic (fen) peatlands. The vegetation communities within and adjacent to power line ROWs were sampled in 23 bogs and 11 fens in southern Québec. In fens, invasive species were found in abundance along the first 250 m within ROWs, while native non-peatland species were able to spread into entire ROWs. Invasive species were also able to colonize the adjacent fen habitats but were mostly concentrated in the first 4 m from ROW edges. Some species were, however, able to establish at more than 43 m from ROWs. Invasive and native non-peatland species were mostly restricted to the first 31 m within ROWs intersecting a bog and almost none dispersed in the adjacent bog habitats. Overall, the average cover of native non-peatland and invasive species in ROWs was mostly related to intrinsic abiotic conditions such as water pH, water conductivity, and water table level, while landscape surrounding the peatland and historical variables (e.g., time elapse since the construction of the ROW) had few impacts in both bogs and fens. Les infrastructures linéaires peuvent faciliter la dispersion des espèces indésirables. Comparativement aux autres types d'infrastructures, le rôle des emprises de lignes électriques comme vecteurs de dispersion demeure peu connu, surtout dans les tourbières. L'objectif de notre étude était d'évaluer les impacts de ces emprises sur la végétation des tourbières ombrotrophes «bogs» et minérotrophes «fens». Nous avons échantillonné la végétation de 23 emprises de lignes électriques traversant des bogs et de 11 autres traversant des fens, dans le sud du Québec. Nous avons également échantillonné la flore des habitats tourbeux adjacents à ces emprises. Dans les emprises traversant les fens, les espèces envahissantes étaient présentes en abondance dans les 250 premiers mètres, alors que les espèces indigènes non-tourbières pouvaient se propager dans l'ensemble des emprises. Les espèces envahissantes étaient également présentes dans les habitats adjacents aux fens, mais surtout dans les quatre premiers mètres en bordure des emprises. Certaines de ces espèces étaient toutefois encore présentes à plus de 43 mètres des emprises. À l'inverse, les espèces envahissantes et non-tourbières étaient surtout confinées le long des 31 premiers mètres dans les emprises traversant les bogs et pratiquement aucune n'était présente dans les habitats adjacents aux bogs. Dans l'ensemble, la susceptibilité des tourbières à l'envahissement dans les emprises est surtout liée aux conditions abiotiques des sites comme le pH et la conductivité de l'eau, et le niveau de la nappe phréatique, tandis que le paysage qui entoure les tourbières et les variables historiques (p. ex., le temps écoulé depuis la construction de l'emprise) ont peu d'effets sur les bogs et les fens. [ABSTRACT FROM AUTHOR]

nthropogenic nitrogen (N) loading has the potential to affect plant community structure and function, and the carbon dioxide (CO) sink of peatlands. Our aim is to study how vegetation changes, induced by nutrient input, affect the CO exchange of a nutrient-limited bog. We conducted 9- and 4-year fertilization experiments at Mer Bleue bog, where we applied N addition levels of 1.6, 3.2, and 6.4 g N m a, upon a background deposition of about 0.8 g N m a, with or without phosphorus and potassium (PK). Only the treatments 3.2 and 6.4 g N m a with PK significantly affected CO fluxes. These treatments shifted the Sphagnum moss and dwarf shrub community to taller dwarf shrub thickets without moss, and the CO responses depended on the phase of vegetation transition. Overall, compared to the large observed changes in the vegetation, the changes in CO fluxes were small. Following Sphagnum loss after 5 years, maximum ecosystem photosynthesis (Pg) and net CO exchange (NEE) were lowered (−19 and −46%, respectively) in the highest NPK treatment. In the following years, while shrub height increased, the vascular foliar biomass did not fully compensate for the loss of moss biomass; yet, by year 8 there were no significant differences in Pg and NEE between the nutrient and the control treatments. At the same time, an increase (24–32%) in ecosystem respiration (ER) became evident. Trends in the N-only experiment resembled those in the older NPK experiment by the fourth year. The increasing ER with increasing vascular plant and decreasing Sphagnum moss biomass across the experimental plots suggest that high N deposition may lessen the CO sink of a bog. [ABSTRACT FROM AUTHOR]

The article presents a study on the Holocene Peat Model (HPM), a simulation model designed to determine peat accumulation tested at a temperate bog in Ontario. It states that the HPM was made and evaluated considering factors such as hydrology, peat properties and the nature of plant communities. It adds that peat decomposition and dynamic peat accumulation models were combined in HPM. Moreover, it asserts that the HPM is capable of demonstrating balances in peatland carbon and watecycles.

The chronostratigraphy of a coastal bog was studied in order to distinguish the roles of autogenic and allogenic factors in peatland development. Well-dated stratigraphical sequences from a peat cliff were used. The peatland shows three main vegetation phases: rich fen, poor fen and bog. Peat formation started around 9500 yr BP and the first expansion phase of rich fen occurred between 8550 and 7400 yr BP. The rich fen gradually changed to a poor fen through autogenic processes between 7620 and 5500 yr BP. It then became a bog in two major development phases, possibly in response to climate change, around 5250 yr BP (central part) and 2800 yr BP (margins). Expansion resumed after 5500 yr BP and terminated shortly after 2500 yr BP when the peatland had filled the basin. Although autogenic succession is the dominant process by which the peatland has evolved, climatic variability has also affected peat expansion and vegetation change. The influence of fire was very limited but topography played a major role in peat expansion. One major find is that climate change can trigger simultaneous but various responses in local vegetation, depending upon its position on the bog surface. [ABSTRACT FROM AUTHOR]

Peatland-margin habitats with organic matter accumulation of 40–150 cm make up a significant but poorly quantified portion of Canada’s boreal forest region. Spanning the transition between non-wetland forest and fen proper, these ecosystems represent a zone of complex environmental and vegetation change, yet little is known about their ecological function or development. We here use vegetation and macrofossil analysis, traditional 14C, bomb-spike 14C, and 210Pb dating to investigate the development, organic matter accumulation, and recent vegetation history of peat margin communities at two sites in central Saskatchewan, Canada. Although similar in general shape, bomb-spike 14C and 210Pb chronologies show limited agreement in three of the four profiles examined, with 210Pb generally producing younger ages than 14C. Peat initiation and long-term organic matter accumulation at the Old Black Spruce (OBS) transect were probably driven mainly by the dynamics of Sphagnum, whereas at the Sandhill Fen (SF) transect, they were controlled by water level fluctuations in the neighboring fen. Bryophyte macrofossils suggest a recent drying of the vegetation surface at both sites, most likely triggered by regional drought in the late 1950s and 1960s. At OBS, the shift from Sphagnum- to feather moss-dominated communities continued in the 1990s, possibly reflecting effects of direct disturbance on local drainage patterns. Overall, our results suggest that community composition and C dynamics of peat-margin swamps respond dynamically to climatic and hydrologic fluctuations. However, uncertainties regarding the reliability of different chronologies limit our ability to link observed community changes to specific causal events. [ABSTRACT FROM AUTHOR]