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Highlights • Three revegetation strategies are tested to restore wet depressions in fens. • Moss transfer promotes higher fen species richness and distinct plant assemblages. • Carex spp. revegetation increases vascular species cover. • Plant communities of Scirpus validus -revegetated depressions were similar to control. • Combining moss transfer and Carex transplants should foster restoration success. Abstract Pool margins and wet depressions (hollows) contribute considerably to peatland biodiversity by sheltering specific plant assemblages. In peatlands restored after peat extraction, the typical communities associated with pools generally fail to re-establish if only the moss layer transfer technique is applied, a common approach on flat bare peatlands. To adapt peatland ecological restoration methods for recolonizing shallow wet fen habitats, this study investigates the response of plant communities re-establishing in wet depressions subjected to four revegetation strategies. In a restored fen (southeastern Quebec, Canada), 48 depressions were dug out and revegetated with 1) mosses, 2) Carex species, 3) Scirpus validus , or 4) through spontaneous colonization (control treatment without implanted species). After four growing seasons, plant community structure and composition were surveyed in and outside the revegetated area respectively to test whether reintroduced communities had a propensity to extend beyond the central wet depression. Restoration strategies strongly impacted plant communities. Moss-revegetated wet depressions had higher moss and vascular fen-specialist species richness and distinct species assemblages relative to other treatments. Carex treatment increased only vascular cover compared to control, while Scirpus validus treatment did not differ from control. The positive impact of moss transfer was local and limited to core revegetated areas, as transferred plant material did not colonize any further. Our results suggest that transferring moss in created wet depressions is an effective strategy to foster the recolonization of diverse and distinct plant assemblages, and thereby restore local fen biodiversity hotspots. [ABSTRACT FROM AUTHOR]

There is an increasing interest in considering ecosystem processes after fen restoration, and not solely species composition. To evaluate the success of ecological restoration, comparisons with targets from reference ecosystems are required. We documented net primary production (NPP) and decomposition of the main vegetation components in order to describe a reference data set for ecological restoration of moderately rich to rich minerotrophic peatlands (fens) in southeastern Canada. Data collection included three growing seasons for herbs and shrubs and two growing seasons for belowground biomass, trees and bryophytes. Average NPP for above and belowground biomass of three selected natural basin fens were 450 g m −2  yr −1 . Belowground NPP represented 45% of the total NPP. Sphagnum warnstorfii was the most productive bryophyte (140 g m −2  yr −1 ) and the slowest plant species to decompose (exponential decomposition constant k  = 0.07 yr −1 ). The brown mosses Tomenthypnum nitens , Campylium stellatum and Scorpidium cossonii had a NPP of 79, 69 and 92 g m −2  yr −1 , respectively, and decomposed at the same rate (identical k values of 0.14 yr −1 ). Trees covered a large surface area in the fens, with an average NPP of 73 g m −2  yr −1 . S. warnstorfii contributed to hummocks having a higher peat accumulation potential than lawn vegetation. The graminoid Trichophorum cespitosum significantly increased NPP in lawns and should be targeted in restoration plans for fens. To restore peat accumulating processes (production and decomposition) in fens, bryophytes should be the primary focus for re-introduction, specifically species that are adapted to living in drier conditions, such as hummock species. The range of variability for NPP and decomposition established by this study should be considered as a decision tool in restoration projects to monitor restored ecosystems trajectories and successes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Innovative restoration approach specific to peatlands pools. [•] Ericaceous shrubs transplanted near pools reduce frost heave by 52%. [•] Ericaceae promote Sphagnum majus establishment at water edge of restored pools. [Copyright &y& Elsevier]

Abstract: Mosses are keystone species in peatlands and are an important part of the vegetation of the pre-mined peatlands. Therefore, mosses should be included in rehabilitation projects following oil sands exploitation in north-western Canada. However, mosses growing in post-mined landscapes must tolerate elevated salinity levels found in oil sands process water (OSPW). Knowledge of salinity tolerance and thresholds for fen mosses is needed to place these mosses in the newly created landscapes. We tested the effects of NaCl and Na2SO4 on four fen moss species growing in Petri dishes in growth chambers. We simulated two scenarios: (1) four immersion times (¼, 1, 3 and 7 days) in NaCl (0%, 20%, 60% or 100% of the concentration found in OSPW) mimicking periodic flooding and (2) a permanent saline influence (NaCl or Na2SO4 alone or in combination at 0%, 30%, 50% or 70% of the concentrations found in OSPW) mimicking situations of high water tables with different contamination levels. The effects on moss growth were estimated by counting new innovations of Bryum pseudotriquetrum, Campylium stellatum, Sphagnum warnstorfii and Tomenthypnum nitens. All tested mosses tolerated saline levels typically found in post-mined landscapes (up to 500mgL−1 of NaCl and 400mgL−1 of Na2SO4) for up to 100 days of exposure. Short periods of immersion (up to 7 days independently of salt concentrations) induced the production of innovation in non-Sphagnum species, but S. warnstorfii was more rapidly impacted at higher salt concentrations. Short pulses of salt (from 6h to 7 days) did not influence the formation of new innovations for C. stellatum and T. nitens. Salt type (NaCl and/or Na2SO4) had no effect on moss growth. However, a longer exposure (100 days) with saline water, even at low concentrations, diminished the formation of new innovations for B. pseudotriquetrum and T. nitens. C. stellatum was the least affected by salinity and thus we suggest it is the best species to reintroduce in constructed fens. [Copyright &y& Elsevier]

Fen plant growth in peat contaminated with groundwater discharges of oil sands process water (OSPW) was assessed in a greenhouse over two growing seasons. Three treatments (non-diluted OSPW, diluted OSPW and rainwater) were tested on five vascular plants and four mosses. All vascular plants tested can grow in salinity and naphthenic acids levels currently produced by oil sands activity in northwestern Canada. No stress sign was observed after both seasons. Because of plant characteristics, Carex species (C. atherodes and C. utriculata) and Triglochin maritima would be more useful for rapidly restoring vegetation and creating a new peat-accumulating system. Groundwater discharge of OSPW proved detrimental to mosses under dry conditions and ensuring adequate water levels would be crucial in fen creation following oil sands exploitation. Campylium stellatum would be the best choice to grow in contaminated areas and Bryum pseudotriquetrum might be interesting as it has spontaneously regenerated in all treatments. [Copyright &y& Elsevier]

Abstract: Establishment of specific vascular plants and Sphagnum species, as well as asymmetrical competition and facilitation between the two types of plants are apparently important in the development of microtopography in peatlands. To determine whether peatland vascular plants can facilitate the initiation of Sphagnum hummocks, and consequently the differentiation of bog microtopography, we investigated the effects of vascular plant life form and structure on Sphagnum stem length and biomass. We showed that Sphagnum stem length and biomass were enhanced by low density of vascular plants and other introduced structures, which thus favoured hummock formation. Dense covers of vascular plants also promoted moss height growth, but the Sphagnum stems were etiolated and fluffy, their densities were too low and biomass was too small to initiate clear hummocks. We also showed that vascular plants contributed to microhabitats with stable temperatures and high relative humidity favourable to Sphagnum growth. Stress-gradient hypothesis, predicting that the relative frequencies of facilitation and competition events will vary inversely along abiotic stress gradients, could explain the nature of the interaction between mosses and vascular plants. At the onset of microstructures formation in peatlands, abiotic stress is probably more important and facilitation events could be frequent. Microclimatic effects of vascular plants may be essential for Sphagnum growth. Then, the presence of ericaceous shrubs or young trees enhances the microtopography by physically reinforcing the hummocks. During accentuation of microtopography, the positive interactions between Sphagnum mosses and vascular plants may be replaced by competition as abiotic stress declines. This study introduces new evidence for the role of vascular plants in the formation and maintenance of hummocks, especially under drier growing conditions. [Copyright &y& Elsevier]

Site preparation for restoration of peat-mined bogs in eastern Canada frequently involves the construction of bunds or shallow basins to enhance peat moisture content. As a consequence, Sphagnum reintroduced within restored areas may be subjected to extended periods of flooding, particularly following snow melt or heavy rainfall. This paper examines two aspects of the effect of flooding on growth and development of Sphagnum: (1) the production of innovations (growth buds and shoots) and capitula from plant fragments (six species) under continuous, intermittent or non-flooding conditions, and (2) the growth response of whole plants (10 species) under long-term continuous shallow flooding.The development response of Sphagnum fragments to short-term continuous (8–10 cm), intermittent (−1 to +1 cm) or non-flooding conditions (−3 to 0 cm), was investigated in growth chambers. Environmental parameters were selected to investigate the possible differential effects of early spring flooding (10:7 °C, day:night), or inundation following heavy rainfall events later in the season (20–25:20 °C, day:night). Both temperature regimes yielded similar results. After 1 month of flooding the number of innovations was generally similar to that for non-flooded controls. However, after a further 3 months, fragments that had been flooded for 1 month (either continuously or intermittently) produced more capitula than non-flooded fragments. Although S. fuscum, a hummock-forming species, showed delayed formation of innovations, flooding still increased final capitula production.The growth response of whole Sphagnum plants to long-term continuous flooding in the field (+1 cm), revealed that most species grew well, but that several becoming etiolated. These modifications may result in plants more prone to desiccation during drier events than individual with a regular growth form.It is concluded that limited periods of shallow flooding could enhance Sphagnum development in restored areas. Care must be exercised though, as deep or extensive inundation may result in excessive plant etiolation or cause severe physical disturbances to the restorated areas. [Copyright &y& Elsevier]

Fertilization is a common and effective restoration practice for some ecosystems. However, there are still knowledge gaps about the long-term effectiveness and impact of phosphorus fertilization during the restoration of degraded boreal Sphagnum peatlands using the Moss Layer Transfer Technique. Data gathered from 114 peatland sectors restored 1 to 25 years ago, encompassing around 2900 surveyed plots in Eastern Canada, were analyzed to investigate the influence of fertilization on plant re-establishment (cover, height, and aboveground biomass accumulation) and community composition. Fertilization with a low phosphorus dosage (1.64 g P m−2) of granular phosphate rock (P 2 O 5 ; NPK 0–13-0) proved to accelerate peatland vegetation recovery by favoring a shift in plant community composition towards a Sphagnum dominance. This shift was encouraged by the fast colonization of Polytrichum strictum after fertilization, a nurse plant that stabilizes the peat substrate and facilitates the subsequent establishment of Sphagnum. Phosphorus fertilization increased by 42 % Sphagnum cover 25-year post-restoration and increased approximately by 15 % aboveground biomass accumulation 20-year post-restoration. Conversely, without fertilization, the success of restoration and long-term vegetation trajectories were uncertain. Phosphorus fertilization led to an increase in plant richness in the first 5 to 10 years after restoration and enhanced spatial heterogeneity in species composition throughout the later stages of restoration (20–25 years), suggesting that fertilization may foster dynamic, diverse plant communities. This study emphasizes fertilization's key role in restoring boreal Sphagnum peatland plant communities, especially in areas prone to episodes of freeze-thaw cycles, strongly advocating for the mandatory inclusion of phosphorus fertilization in the restoration process. [ABSTRACT FROM AUTHOR]

Scientific knowledge of the wet zone – the lagg – that tends to form at the edge of ombrotrophic peatlands is surprisingly limited. In this study, we aim to improve the understanding of the ecohydrological functions of this transition by describing the form and abiotic controls of the laggs and margins of bog peatlands. Data collected in wells and piezometers along 10 transects (within 6 bogs), of the New Brunswick Eastern Lowlands are used to analyse the hydraulic and hydrochemical gradients, while airborne LiDAR data provides new insight on the geomorphology and the vegetation patterns of the bog–lagg–mineral transition zone. Based on their geomorphic character, the study transects are placed into 2 categories: confined and unconfined. Laggs of confined transition are found in a topographic depression, between the bog and a mineral slope > 1%, while laggs of unconfined transitions are adjacent to a flat (≤ 1%) or receding mineral slope (sloping away from the lagg). Water level (4 ± 9 cm vs. − 3 ± 9 cm), pH (4.8 ± 0.9 vs. 4.2 ± 0.4), electrical conductivity (EC corr ) (105 ± 52 μS cm − 1 vs. 52 ± 28 μS cm − 1 ) and peat depth (55 ± 9 cm vs. 30 ± 9 cm) are found to be higher, respectively, for the confined laggs than for the unconfined. Saturated hydraulic conductivity (K sat ) of the lagg's upper peat layer resembles that of bog environments, but quickly reduces with depth, impeding vertical water flow. The greatest abiotic control of the lagg appears to be topography, which affects water flow rates and direction, thus water chemistry, nutrient transport and availability, hence vegetation characteristics. Our results suggest that the features of the transition zone that include the lagg, influence the quantity and variability of water within the adjacent peatland, and should be considered as integral part of the peatland complex. [ABSTRACT FROM AUTHOR]

Sphagnum farming refers to the cultivation of Sphagnum mosses to produce Sphagnum biomass sustainably. Some possible uses of these fibers are as ingredients in growing substrates, as floral moss, as plant packaging during transport, or as moss reintroduction material for peatland restoration projects. Because this biomass production is sustainable, Sphagnum farming should reduce human impacts on natural peatlands. Despite its various benefits, research on Sphagnum farming is limited. To determine if Sphagnum farming is feasible on a large-scale basis (on the order of 900–1500 m 2 size basin), 6 yearly production cycles were implemented in trenches of former block-cut peatland in eastern Canada. These sites were monitored over seven growing seasons. Sphagnum cover (67%) and accumulated biomass (787 g m −2 ) from the culture basins were similar or superior to surveys from restored peatlands. However, cover and biomass values differed greatly among production cycles when comparing the time elapsed since the creation of the basins. Differences in productivity during different cycles were largely coupled with variations of water table levels compared to intrinsic properties of plant interactions. We believe that the optimization of water access (for example through automated of irrigation systems) for Sphagnum mosses would greatly improve the productivity of Sphagnum farming. [ABSTRACT FROM AUTHOR]

Abstract: Our earlier study in New Brunswick, Canada showed that Spartina pectinata Link survived very well after transplantation in a barren cutover bog that was contaminated by seawater, in all combinations of salinity and moisture content tested. However, the survival of Juncus balticus Willd. was adversely affected in areas with very high moisture contents. The main aim of this current study was to understand the salinity tolerance of both species grown in salinized peat fields by determining how much salt ions, especially Na+ and Cl− were accumulated in the above-ground and below-ground parts of these plants. A second aim of this paper was to determine the accumulation of potentially toxic metals Fe and Mn. S. pectinata had significantly greater concentrations of Na+ and Cl− in the above- than in the below-ground parts. In contrast, J. balticus had Na+ concentration significantly greater in the below- than in the above-ground parts while for Cl−, there was no significant difference. These contrasting patterns of Na+ accumulation demonstrated typical characteristics of a halophyte (S. pectinata) and a glycophyte tolerant to salinity (J. balticus) described in literature. Fe and Mn concentrations in both species were low but only Fe approached deficiency levels in plants. [Copyright &y& Elsevier]

Abstract: A cutover bog contaminated with seawater in New Brunswick, Canada remained barren 5 years after peat extraction operations ceased despite the proximity of natural seed sources. The aim of the study was to identify abiotic stresses impeding plant establishment and test transplanting of salt-tolerant wetland plants. The site consisted of long cambered rectangular fields that sloped down (2%) to the drainage ditches on both sides. Across this slope, zones were delineated based on moisture gradient as: Up-areas (drier), Mid-areas (moist) and Low-areas (wet). Juncus balticus was transplanted to these zones in August 2004 whereas Spartina pectinata was reintroduced in June 2005. Plant material was collected from nearby marshes. Survival of J. balticus in August 2005 was poorest at the Low-areas probably because of the early season flooded conditions of that zone. S. pectinata survival in June 2006 was good in all zones having better adaptation to early season waterlogged conditions. Early season waterlogged conditions resulted from a perched water table (May–June) and were alleviated only upon the complete thaw of the frozen peat layer on 8 July. Thereafter, important changes in peat characteristics occurred: lowered water table depths that increased redox potentials, decreased moisture content (θ) that increased dry bulk density (ρ), and increased electrical conductivity (EC) that decreased pH. Waterlogged conditions were of greater magnitude and duration at the Low-areas but salinity levels were highest in the Up-areas and Mid-areas. We conclude that local conditions of waterlogging (especially in the Low-areas) and high salinity and low pH (notably in the Up- and Mid-areas) favoured the survival of S. pectinata in all areas and J. balticus in Up- and Mid-areas only. [Copyright &y& Elsevier]

Abstract: Vegetation responses to phosphorus (P) fertilization were assessed on post-vacuum extracted peatlands under ecological restoration. The study aimed to evaluate the importance of P fertilization in promoting plant re-establishment and to delineate fertilization practices. A total of 11 P treatments were tested across three different peatlands under restoration. After three growing seasons, it was found that bryophytes (excluding sphagna) were the main strata benefiting from P fertilization. Mosses like Polytrichum strictum showed positive responses to P addition, provided that the rewetting was optimal and that these bryophytes were present in the donor site. The optimal dose of phosphate rock (PR) to encourage plant re-establishment appears to be in the range of 15–25gPRm−2. Fertilization timing should be investigated further as applications would probably have more impact during periods of high nutrient uptake by target plants in establishment phase than before or after other restoration steps. Furthermore, splitting the fertilization in two applications slightly improves the re-establishment of P. strictum. Fertilization in peatland restoration remains a site-specific decision, considering intrinsic site properties and the effectiveness of restoration measures. [Copyright &y& Elsevier]

Abstract: The Bois-des-Bel Sphagnum peatland (Rivière du Loup, QC) was restored in 1999 after 20 years of abandonment. Restoration work included not only the blockage of drainage ditches, but also the reintroduction of plant material including Sphagnum remains. Following restoration, the physicochemical and microbial characteristics (biomass, activity and composition) of the peat were analysed. The goal was to investigate the functional status of the restored ecosystem. The high N:P (>20) and N:K (>15) ratios indicated possible K and P deficiencies in the restored and the cutover sites, which is mainly associated with the intense leaching and the high degree of decomposition of the peat in these sites. The concentrations of , P and K in the top layer of the restored site were closer to those of the natural site, which indicated a possible effect of restoration on the physicochemistry of the restored site. Microbial biomass values derived from the FE technique followed a gradient natural>restored>cutover through the profile, which was not the case with the SIR technique. Values from SIR varied overall between 0.19 and 4.88mg C g−1 and were significantly higher in the natural site. The natural peatland site had significantly (P<0.05) greater cumulative C–CO2 production (surface aerobic: 4.5–8.7μg C–CO2 g−1 h−1). The poor organic matter quality was the main explanation for the low respiration rates of the surface layer in the restored and the cutover site. All CO2 respiration data were plotted against time and the resulting curves were successfully fitted to a global kinetic model. Methane production was detected at low but measurable rates in the natural and the restored samples, but not in the cutover peat. Overall, the results confirmed the existence of a lag between the positive response of vegetation to restoration and that of the microbial compartment. This study also pointed out that some physicochemical dysfunctions remained even after three growing seasons following restoration in the subsurface horizons studied. [Copyright &y& Elsevier]

Highlights • Seed re-introduction success depends on storage conditions that favour seed viability. • Four conditions were tested for storing viable seeds of eight peatland hollow species. • Storage decreased the seed viability of four species. • Dry storage promotes higher viability for Drosera intermedia and Rhynchospora alba. • Choice of conservation actions by direct sowing or dry storage depend on species requirements. Abstract Seed introduction is a current practice for the conservation and restoration of plant populations and communities. In many cases, however, seeds of target wild species must be collected from natural populations and then stored in proper conditions until re-introduction. Peatland pool margin specialists rarely recolonize their habitat once a peatland is restored following peat extraction and therefore must be actively reintroduced. However, little is known about the storage conditions promoting seed viability. In this context, we investigated the effects of four storage conditions on the seed viability of eight species collected from natural peatland pool margins of eastern Canada: 1) room temperature, dry conditions, 2) cold temperature, dry conditions, 3) cold temperature, moist conditions, and 4) cold temperature, submerged. Seeds stored for one year were periodically (3, 6, 12 months) tested for viability using 2,3,5-triphenyltetrazolium chloride staining. Seed viability decreased after storage for four of the eight species investigated (Carex echinata , C. magellanica , C. oligosperma , and C. pauciflora) and increased for Rhynchospora alba , but did not vary significantly following storage for C. limosa and Scheuchzeria palustris. Furthermore, the viability of Drosera intermedia and Rhynchospora alba seeds was higher when stored in dry conditions relative to moist or submerged conditions. Proper seed storage conditions are thus highly species-dependent. Direct sowing after collection should be preferred for most of the Carex species, while seeds of Scheuchzeria palustris , Drosera intermedia and Rhynchospora alba could be stored, preferably in dry conditions, without impacting introduction success due to reduced seed viability. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the recovery of the microbial compartment following active restoration of a North American ombrotrophic peatland extracted for horticultural peat-based substrates and restored by the Sphagnum moss transfer method. We used phospholipid fatty acids (PLFAs) to portrait the microbial community structure and Community Level Physiological Profiles (CLPP) to describe the functional diversity of the microbial communities. Our results indicate that the PLFA profiles were different between the beginning and the end of the growing season, but that it was impossible to distinguish five different vegetation classes found along the disturbance-recovery gradient on the basis of the microbial community structure. The pH, the cover of mosses, Ledum groenlandicum and Eriophorum vaginatum var. spissum were the best environmental predictors for the PLFA composition. The newly formed peat found in aerobic conditions beneath restored Sphagnum carpets had the highest decomposition capacity, whereas the lowest rates were found in the surface samples of non-restored conditions or in the deepest horizons of the natural samples. A large proportion of the variation in the physiological profiles was explained with variables related to the vegetation cover, the physicochemical environment and the microbial structure of the community, which is very promising for future monitoring studies. Overall, this study demonstrates that the recovery of particular plant groups, namely mosses and shrubs in restored peatlands might be the driver of changes occurring in the structure of the microbial communities in restored peatlands. [Copyright &y& Elsevier]