Assessing soil carbon dioxide and methane fluxes from a Scots pine raised bog-edge-woodland.

Scots pine bog edge woodland is a type of habitat typical on raised bogs where trees cohabitate with bog vegetation to form a low-density stand. Even though nowadays this habitat does not cover large areas, in a future scenario it is possible that this environment will expand, either naturally (drier climate) or anthropogenically, as the result of the application of new restoration strategies that could increase net landscape carbon benefits from both peatland and woodland environments. This study is the first reported investigation in Scotland exploring carbon flux dynamics from sparse woodlands on raised bogs. We examined how Scots pine trees directly or indirectly affected soil temperature and moisture, ground vegetation, and consequently carbon dioxide (CO2) and methane (CH4) soil fluxes. Soil CO2 and CH4 were measured at different distance from the tree and thereafter assessed for both spatial and temporal variability. Our results showed that these low-density trees were able to modify the ground vegetation composition, had no effect on soil temperature, but did affect the soil moisture, with soils close to tree roots significantly drier (0.25 ± 0.01 m3 m-3) than those on open bog (0.39 ± 0.02 m3 m-3). Soil CO2 fluxes were significantly higher in the vicinity of trees (34.13 ± 3.97 µg CO2 m-2 s-1) compared to the open bog (24.34 ± 2.86 µg CO2 m-2 s-1). On the opposite, CH4 effluxes were significantly larger in the open bog (0.07 ± 0.01 µg CH4 m-2 s-1) than close to the tree (0.01 ± 0.00 µg CH4 m-2 s-1). This suggests that Scots pine trees on bog edge woodland may affect soil C fluxes in their proximity primarily due to the contribution of root respiration, but also as a result of their effects on soil moisture, enhancing soil CO2 emissions, while reducing the CH4 fluxes. There is, however, still uncertainty about the complete greenhouse gas assessment, and further research would be needed in order to include the quantification of soil nitrous oxide (N2O) dynamics together with the analysis of complete gas exchanges at the tree-atmosphere level.

Overcoming establishment thresholds for peat mosses in human-made bog pools.

Globally, peatlands have been affected by drainage and peat extraction, with adverse effects on their functioning and services. To restore peat-forming vegetation, drained bogs are being rewetted on a large scale. Although this practice results in higher groundwater levels, unfortunately it often creates deep lakes in parts where peat was extracted to greater depths than the surroundings. Revegetation of these deeper waters by peat mosses appears to be challenging due to strong abiotic feedbacks that keep these systems in an undesired bare state. In this study, we theoretically explore if a floating peat mat and an open human-made bog lake can be considered two alternative stable states using a simple model, and experimentally test in the field whether stable states are present, and whether a state shift can be accomplished using floating biodegradable structures that mimic buoyant peat. We transplanted two peat moss species into these structures (pioneer sp. Sphagnum cuspidatum and later-successional sp. S. palustre) with and without additional organic substrate. Our model suggests that these open human-made bog lakes and floating peat mats can indeed be regarded as alternative stable states. Natural recovery by spontaneous peat moss growth, i.e., a state shift from open water to floating mats, is only possible when the water table is sufficiently shallow to avoid light limitation (<0.29 m at our site). Our experiment revealed that alternative stable states are present and that the floating structures facilitated the growth of pioneer S. cuspidatum and vascular plants. Organic substrate addition particularly facilitated vascular plant growth, which correlated to higher moss height. The structures remained too wet for the late-successional species S. palustre. We conclude that open water and floating peat mats in human-made bog lakes can be considered two alternative stable states, and that temporary floating establishment structures can induce a state shift from the open water state to peat-forming vegetation state. These findings imply that for successful restoration, there is a clear water depth threshold to enable peat moss growth and there is no need for addition of large amounts of donor-peat substrate. Correct species selection for restoration is crucial for success.

Azospirillum palustre sp. nov., a methylotrophic nitrogen-fixing species isolated from raised bog.

Nitrogen-fixing bacterial strain, designated B2T, was isolated from methane-oxidation enrichment originating from a Sphagnum-dominated raised peatland in Tver region, Russia, and its phenotypic, chemotaxonomic and genomic characteristics were investigated. Cells of isolate were Gram-negative, aerobic, rod or spiral-shaped, with motility provided by a single polar flagellum in liquid media and peritrichous flagella on solid media. Strain was able to grow at 15-40 °C, pH 5.5-8.5 and tolerated NaCl to 2.0 % (w/v). Strain B2T gave positive amplification for dinitrogen reductase (nifH gene) and acetylene reduction activity was recorded up to 1250 nmol ethylene h-1 (mg protein)-1. Analysis of 16S rRNA showed that B2T represents a member of the genus Azospirillum and had the highest sequence similarity with A. humicireducens SgZ-5T (97.92 %). The predominant quinone system was ubiquinone Q-10 and the major fatty acids were C18 : 1ω7, C16 : 1ω7 and C16 : 0. The strain was facultative methylotrophic and used methanol and formate for the growth. Genome sequencing revealed a genome size of 8.0 Mbp and a G+C content of 67.8 mol%. The mxaFI genes encoding methanol dehydrogenase were absent, but a homologous xoxF gene was detected. The genes encoding enzymes involved in the biosynthesis of tetrahydromethanopterin (H4MPT) (formaldehyde oxidation) and NAD-linked formate dehydrogenase (fdsABG) were identified. Pairwise determined whole genome average nucleotide identity (gANI) values confirmed that strain B2T represents a novel species, for which we propose the name Azospirillum palustre sp. nov. with the type strain B2T (VKM B-3233T, КСТС 62613Т).

Testate amoebae response and vegetation composition after plantation removal on a former raised bog.

Extensive drainage of peatlands in north-west Europe for the purposes of afforestation for timber production and harvesting has altered the carbon balance and biodiversity value. Large-scale restoration projects aim to reinstate hydrological conditions to keep carbon locked up in the peat and to restart active peat growth. Testate amoebae are an informal grouping of well-studied protists in peatland environments and as microbial consumers play an important role in nutrient and carbon cycling. Using a space for time substitution approach, this study investigated the response of testate amoebae assemblages and vegetation composition after tree removal on a drained raised bog. There was a clear difference in microbial assemblages between open and a chronosequenceof restoration areas. Results suggest microbial recovery after rewetting is a slow process with plant composition showing a faster response than the microbial assemblage. Mixotrophic testate amoebae had not recovered seventeen years following plantation removal and the establishment of Sphagnum mosses in the wetter microforms. These results suggest that vegetation composition and Testate amoeba assemblages respond differently to environmental drivers at forest-to-bog restoration areas. Local physicochemical peat properties were a stronger driver of the testate assemblage compared with vegetation. Complete recovery of microbial assemblages may take place over decadal timescales.

An examination of the influence of drained peatlands on regional stream water chemistry.

Currently, 50% of Irish rivers do not meet water quality standards, with many declining due to numerous pressures, including peatland degradation. This study examines stream water quality in the Irish midlands, a region where raised bogs have been all historically disturbed to various extent and the majority drained for industrial or domestic peat extraction. For the first time, we provide in-depth analysis of stream water chemistry within a heavily modified bog landscape. Small streams from degraded bogs exhibited greater levels of pollutants, in particular: total dissolved nitrogen (0.48 mg/l) and sulphate (18.49 mg/l) as well as higher electrical conductivity (mean: 334 µS/cm) compared to similar bog streams in near-natural bogs. Except for site-specific nitrogen pollution in certain streams surrounding degraded peatlands, the chemical composition of the receiving streams did not significantly differ between near-natural and degraded sites, reflecting the spatio-temporal scales of disturbance in this complex peat-scape. Dissolved organic carbon concentrations in all the receiving streams were high (27.2 mg/l) compared to other Irish streams, even within other peatland catchments. The region is experiencing overall a widespread loss of fluvial nitrogen and carbon calling for (a) the development of management instruments at site-level (water treatment) and landscape-level (rewetting) to assist with meeting water quality standards in the region, and (b) the routine monitoring of water chemistry as part of current and future peatland management activities. Supplementary Information: The online version contains supplementary material available at 10.1007/s10750-023-05188-5.

A comparison of porewater chemistry between intact, afforested and restored raised and blanket bogs.

Afforestation is a significant cause of global peatland degradation. In some regions, afforested bogs are now undergoing clear-felling and restoration, often known as forest-to-bog restoration. We studied differences in water-table depth (WTD) and porewater chemistry between intact, afforested, and restored bogs at a raised bog and blanket bog location. Solute concentrations and principal component analysis suggested that water-table drawdown and higher electrical conductivity (EC) and ammonium (NH4-N) concentrations were associated with afforestation. In contrast, higher dissolved organic carbon (DOC) and phosphate (PO4-P) concentrations were associated with deforestation. Drying-rewetting cycles influenced seasonal variability in solute concentrations, particularly in shallower porewater at the raised bog location. WTD was significantly deeper in the oldest raised bog restoration site (~9 years post-restoration) than the intact bog (mean difference = 6.2 cm). However, WTD in the oldest blanket bog restoration site (~17 years post-restoration), where furrows had been blocked, was comparable to the intact bog (mean difference = 1.2 cm). When averaged for all porewater depths, NH4-N concentrations were significantly higher in the afforested than the intact sites (mean difference = 0.77 mg L-1) whereas significant differences between the oldest restoration sites and the intact sites included higher PO4-P (mean difference = 70 µg L-1) in the raised bog and higher DOC (mean difference = 5.6 mg L-1), EC (mean difference = 19 µS cm-1) and lower SUVA254 (mean difference = 0.13 L mg-1 m-1) in the blanket bog. Results indicate felled waste (brash) may be a significant source of soluble C and PO4-P. Mean porewater PO4-P concentrations were between two and five times higher in furrows and drains in which brash had accumulated compared to other locations in the same sites where brash had not accumulated. Creating and maintaining brash-free buffer zones may therefore minimise freshwater impacts.

Annual gaseous carbon budgets of forest-to-bog restoration sites are strongly determined by vegetation composition.

Large areas of naturally open peatland in western Europe were drained and planted with non-native conifers in the twentieth century. Efforts are currently underway to restore many of these sites. Ultimately, forest-to-bog restoration aims to bring back functional peatlands that can sequester carbon but there is a lack of empirical evidence for whether current approaches are effective. Using a chronosequence design, we compared the annual gaseous carbon balance of two forest-to-bog restoration areas with an open area not subject to afforestation. A closed chamber method was used to determine gas fluxes (Net Ecosystem Respiration, Gross Primary Productivity, Net Ecosystem Exchange (NEE) and methane (CH4)) over a twelve-month period for locations spanning the range of peatland microtopography and vegetation communities. Relationships between gas fluxes, vegetation/cover and environmental factors were analysed and regression models used to estimate annual CO2 and CH4 budgets. During the study period, NEE estimates (total gaseous C expressed as CO2-eq) showed a net sink for the unafforested (-102 g C m-2 yr-1) and oldest (-131 g C m-2 yr-1) restoration area (17 years post-restoration 'RES 17 YRS'), whilst the youngest restoration area (6 years post-restoration 'RES 6YRS'), was a net source (35 g C m-2 yr-1). We observed significantly higher CH4 emissions from restoration areas dominated by Eriophorum angustifolium compared with other peatland vegetation types. Sampling points with higher cover of Sphagnum were found to be most effective for C sequestration. Overall, vegetation composition/cover was observed to be an important factor determining C emissions from forest-to-bog restoration areas. These results suggest that restoration is effective in returning the carbon sink function of peatlands damaged by commercial forestry and - depending on restoration techniques - timescales of >10 years may be required.

Data on chemical characteristics of waters in two boreal Sphagnum mires (North-Western Russia).

The dataset contains chemical parameters of waters in different mire water bodies (fen strip, bog stream, Sphagnum hollows, hollow-pools, intra-mire lakes, drainage way). Data were collected once a month from May till September 2012 and in May, July and September 2013 and 2014 in Shichengskoe and Alekseevskoe-1 mires (Vologda Region, Russia). Water samples were kept in a cooling bag and transported to the laboratory within a day. Prior to analyses, water samples were filtered (pore size 90 µm). Colour of water, pH, permanganate value, dry residues, and total iron, manganese, carbonate, phosphate, sulphate and nitrate ion concentrations were measured. Data were obtained by the atomic absorption spectrometry and spectrophotometric and titrimetric methods. The pH values varied from 3.7 in Sphagnum hollows to 6.9 in a bog stream and 7.2 in a primary intra-mire lake. The minimum permanganate value of 5.6 mg O/L was registered in a bog stream, the maximum of 150.4 mg O/L in a weakly waterlogged Sphagnum hollow. Dry residue values varied in a range of 35 mg/L in a large hollow-pool to 315 mg/L in a flow-through fen strip. The data are useful for investigating chemical composition of waters in different mire water bodies and the heterogeneity of these abiotic factors.

Revegetation of peat excavations in a derelict raised bog.

Thorne Waste, S. Yorkshire, is a large raised bog, subject to extensive commercial peat extraction, which retains some re-flooded, revegetated peat cuttings. The composition of the vegetation of some of these cuttings (96 sampled quadrats, each of 25 m2 ) has been related to a number of environmental variables. Revegetation sequences in the abandoned cuttings (all less than 60 years old and with less than 20 cm peat infill) were established by stratigraphical analyses. In some cuttings a basal layer of ericaceous peat apparently marks temporarily drier conditions preceding deeper inundation. Some former mire species (e.g. Sphagnum imbricatum have not survived the peat-cutting period even on uncut surfaces (baulks) but these have been much drained and burnt. The revegetated cuttings contained species typical of poor-ten (e.g. Carex curta) as well as of ombrotrophic mires (e.g. Andromeda polifolia); chemical analyses indicated weakly minerotrophic peat water. This may favour such species as Sphagnum recurvum. There was no indication of chemical enrichment from inflow from surrounding farmland, from underlying mineral ground or from the clay-lined canals excavated across the bog. Release of cations following drainage and re-flooding may provide some explanation. Only soluble reactive phosphorus (SRP) concentration in peat water samples showed consistent and significant seasonal variation, with the lowest values in summer. There were also only a few consistent differences in water chemistry amongst most of the vegetation units identified by TWINSPAN. Nodum 4 (Eriophorum-Sphagnum) stands (richest in ombrotrophic species) occupied the least minerotrophic conditions. One culling, dominated by Juncus, effuses, had no ombrotrophic species (nodum 6). Water concentrations of Ca2+ , Na+ , K+ NH4 + , SO4 2 and SRP were significantly larger here than in other cuttings and peat fertility (estimated phytometrically) and K, N and P concentrations in peat extracts were significantly greater than in a Sphagnum-dominated cutting. The J. effuses samples had strong negative loadings on axis 2 of a Principal Components Analysis (PCA) of the Adriatic data; concentrations of NH4 + , Na+ and SO4 2 in the water showed significant negative correlation with axis 2 ordination scores. Seasonal fluctuation of water level was similar in most cuttings (the J. effuses cutting was exceptional) but variation in depth relative to the peat surface (caused by excavation to different depths) was related to floristic variation. PCA axis 1 may reflect a water-table gradient with TWINSPAN noda 2 (Calluna Sphagnum recurvum) and particularly 1 (Pteridium Campylopus) occupying drier conditions than the others. The wetter cuttings (except the J. effusus site) supported most ombrotrophic and poor-fen species. They were not readily segregated into discrete vegetation types and the two TWINSPAN classes (noda 3 and 4) that accommodated them showed much overlap on the PCA ordination. Nodum 4 samples tended to have higher loadings on PCA axis 2 and to be more species-rich than nodum 3 samples. Species-richness was strongly positively correlated with PCA axis 2. This may reflect, in part, stand maturity, vegetation with most species having been disturbed least recently.

PLANTS AND PEAT CUTTINGS: HISTORICAL ECOLOGY OF A MUCH EXPLOITED PEATLAND - THORNE WASTE, YORKSHIRE, UK.

Although many lowland raised bogs have been much modified or completely destroyed by agricultural reclamation, peat cutting, unaccompanied by reclamation, is not necessarily so destructive, and abandoned workings may provide a range of habitats that can support some of the original wetland plant species. Thome Waste, a much exploited raised bog in Eastern England, has a varied and well-documented management history and comparatively good botanical records. It thus provides an exemplary site to assess the effect of peat exploitation upon its flora. The origin and development, and subsequent drainage, reclamation and peat extraction history of the site are described, and their impact upon the past and present flora is evaluated. Some ombrotrophic mire species have been lost from the site, but one section of peat cuttings (the Dutch canal system, abandoned about 1920) has revegetated and supports an important range of these plants. Fen species, which once occupied the marginal lagg, have been almost completely eliminated from their original sites (which have mostly been reclaimed) but many have become re-established in various new habitats created within the peat-cutting complex. This illustrates the potential of artificial modification of worked-over peatland sites to sustain a range of wetland plants.