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The influence of soil phosphorous (P) content on the N-cycling communities and subsequent effects on N2O emissions remains unclear. Two laboratory incubation experiments were conducted on soils collected from a long-term (est. 1995) P-addition field trial sampled in summer 2018 and winter 2019. Incubations were treated with a typical field amendment rate of N as well as a C-amendment to stimulate microbial activity. Throughout both incubations, soil subsamples were collected prior to fertiliser amendment and then throughout the incubations, to quantify the abundance of bacteria (16S rRNA), fungi (ITS) and Thaumarcheota (16S rRNA) as well as functional guilds of genes involved in nitrification (bacterial and archaeal amoA, and comammox) and denitrification (nirS, nirK, nosZ clade I and II) using quantitative PCR (qPCR). We also evaluated the correlations between each gene abundance and the associated N2O emissions depending on P-treatments. Our results show that long-term P-application influenced N-cycling genes abundance differently. Except for comammox, overall nitrifiers' genes were most abundant in low P while the opposite trend was found for denitrifiers' genes. C and N-amendments strongly influenced the abundance of most genes with changes observed as soon as 24 h after application. ITS was the only gene correlated to N2O emissions in the low P-soils while microbes were mostly correlated to emissions in high P, suggesting possible changes in the organisms involved in N2O production depending on soil P-content. This study highlights the importance of long-term P addition on shaping the microbial community function which in turn stimulates a direct impact on the subsequent N emissions. [ABSTRACT FROM AUTHOR]

Drained organic soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils may reduce GHG emissions and could also create suitable conditions for return of the carbon (C) sink function characteristic of undrained organic soils. In this article we expand on the work relating to rewetted organic soils that was carried out for the 2014 Intergovernmental Panel on Climate Change (IPCC) Wetlands Supplement. We describe the methods and scientific approach used to derive the Tier 1 emission factors (the rate of emission per unit of activity) for the full suite of GHG and waterborne C fluxes associated with rewetting of organic soils. We recorded a total of 352 GHG and waterborne annual flux data points from an extensive literature search and these were disaggregated by flux type (i.e. CO2, CH4, N2O and DOC), climate zone and nutrient status. Our results showed fundamental differences between the GHG dynamics of drained and rewetted organic soils and, based on the 100 year global warming potential of each gas, indicated that rewetting of drained organic soils leads to: net annual removals of CO2 in the majority of organic soil classes; an increase in annual CH4 emissions; a decrease in N2O and DOC losses; and a lowering of net GHG emissions. Data published since the Wetlands Supplement (n = 58) generally support our derivations. Significant data gaps exist, particularly with regard to tropical organic soils, DOC and N2O. We propose that the uncertainty associated with our derivations could be significantly reduced by the development of country specific emission factors that could in turn be disaggregated by factors such as vegetation composition, water table level, time since rewetting and previous land use history. [ABSTRACT FROM AUTHOR]

Rewetting of drained industrial peatlands may reduce greenhouse gas (GHG) emissions and promote recolonisation by peat forming plant species. We investigated carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) dynamics over a three-year period in a rewetted industrial peatland in Ireland. Sample plots were established in bare peat, Juncus effusus-Sphagnum cuspidatum, Sphagnum cuspidatum and Eriophorum angustifolium dominated microsites. The relationships between fluxes and environmental variables were examined and regression models were used to provide an estimate of the annual GHG balance for each microsite. All the vegetated microsites were carbon sinks for the duration of the study. Highest uptake occurred in the Eriophorum microsite (146-583 g C m-2 yr-1), followed by Juncus-Sphagnum (35-204 g C m-2 yr-1) and Sphagnum (5-140 g C m-2 yr-1). The bare peat microsite was a source of 37-82 g C m-2 yr-1. No N2O fluxes were detected. Strong inter-annual variation was observed in all microsites, driven by variation in precipitation and subsequent changes in the position of the water table. In terms of Global Warming Potential (GWP), the microsites had either a cooling effect (Eriophorum), a close to neutral effect (Juncus-Sphagnum, Sphagnum) or a warming effect (bare peat) on the climate. [ABSTRACT FROM AUTHOR]

The EU Nature Restoration Law (NRL) is critical for the restoration of degraded ecosystems and active afforestation of degraded peatlands has been suggested as a restoration measure under the NRL. Here, we discuss the current state of scientific evidence on the climate mitigation effects of peatlands under forestry. Afforestation of drained peatlands without restoring their hydrology does not fully restore ecosystem functions. Evidence on long-term climate benefits is lacking and it is unclear whether CO 2 sequestration of forest on drained peatland can offset the carbon loss from the peat over the long-term. While afforestation may offer short-term gains in certain cases, it compromises the sustainability of peatland carbon storage. Thus, active afforestation of drained peatlands is not a viable option for climate mitigation under the EU Nature Restoration Law and might even impede future rewetting/restoration efforts. Instead, restoring hydrological conditions through rewetting is crucial for effective peatland restoration., (© 2024. The Author(s).)

Despite peatlands' important feedbacks on the climate and global biogeochemical cycles, predicting their dynamics involves many uncertainties and an overwhelming variety of available models. This paper reviews the most widely used process-based models for simulating peatlands' dynamics, i.e., the exchanges of energy and mass (water, carbon, and nitrogen). 'Peatlands' here refers to mires, fens, bogs, and peat swamps both intact and degraded. Using a systematic search (involving 4900 articles), 45 models were selected that appeared at least twice in the literature. The models were classified into four categories: terrestrial ecosystem models (biogeochemical and global dynamic vegetation models, n = 21), hydrological models (n = 14), land surface models (n = 7), and eco-hydrological models (n = 3), 18 of which featured "peatland-specific" modules. By analysing their corresponding publications (n = 231), we identified their proven applicability domains (hydrology and carbon cycles dominated) for different peatland types and climate zones (northern bogs and fens dominated). The studies range in scale from small plots to global, and from single events to millennia. Following a FOSS (Free Open-Source Software) and FAIR (Findable, Accessible, Interoperable, Reusable) assessment, the number of models was reduced to 12. Then, we conducted a technical review of the approaches and associated challenges, as well as the basic aspects of each model, e.g., spatiotemporal resolution, input/output data format and modularity. Our review streamlines the process of model selection and highlights: (i) standardization and coordination are required for both data exchange and model calibration/validation to facilitate intercomparison studies; and (ii) there are overlaps in the models' scopes and approaches, making it imperative to fully optimize the strengths of existing models rather than creating redundant ones. In this regard, we provide a futuristic outlook for a 'peatland community modelling platform' and suggest an international peatland modelling intercomparison project., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

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., Competing Interests: Competing interestThe authors have no relevant financial or non-financial interests to disclose., (© The Author(s) 2023.)

Peatland rewetting has been proposed as a vital climate change mitigation tool to reduce greenhouse gas emissions and to generate suitable conditions for the return of carbon (C) sequestration. In this study, we present annual C balances for a 5-year period at a rewetted peatland in Ireland (rewetted at the start of the study) and compare the results with an adjacent drained area (represents business-as-usual). Hydrological modelling of the 230-hectare site was carried out to determine the likely ecotopes (vegetation communities) that will develop post-rewetting and was used to inform a radiative forcing modelling exercise to determine the climate impacts of rewetting this peatland under five high-priority scenarios (SSP1-1.9, SS1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). The drained area (marginal ecotope) was a net C source throughout the study and emitted 157 ± 25.5 g C m -2  year -1 . In contrast, the rewetted area (sub-central ecotope) was a net C sink of 78.0 ± 37.6 g C m -2  year -1 , despite relatively large annual methane emissions post-rewetting (average 19.3 ± 5.2 g C m -2  year -1 ). Hydrological modelling predicted the development of three key ecotopes at the site, with the sub-central ecotope predicted to cover 24% of the site, the sub-marginal predicted to cover 59% and the marginal predicted to cover 16%. Using these areal estimates, our radiative forcing modelling projects that under the SSP1-1.9 scenario, the site will have a warming effect on the climate until 2085 but will then have a strong cooling impact. In contrast, our modelling exercise shows that the site will never have a cooling impact under the SSP5-8.5 scenario. Our results confirm the importance of rapid rewetting of drained peatland sites to (a) achieve strong C emissions reductions, (b) establish optimal conditions for C sequestration and (c) set the site on a climate cooling trajectory., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

The ability of peatlands to remove and store atmospheric carbon (C) depends on the drainage characteristics, which can be challenging to accommodate in biogeochemical models. Many studies indicate that restoration (by rewetting) of damaged peatlands can re-establish their capacity as a natural C sink. The purpose of this research was to improve the biogeochemical modelling of peatlands using the ECOSSE process-based model, which will account for the effects of drainage and rewetting during simulation, and potentially contribute towards improved estimation of carbon dioxide (CO 2 ) fluxes from peatlands, using the IPCC Tier 3 approach. In this study, we present a new drainage factor with seasonal variability Dfa (i) developed specifically for ECOSSE, using empirical data from two drained and rewetted Irish peatlands. Dfa(i) was developed from the Blackwater drained bare-peat site (BWdr), and its application was tested at the vegetated Moyarwood peatland site under drained (MOdr) and rewetted conditions (MOrw). Dfa(i) was applied to the rainfall model inputs for the periods of active drainage in conjunction with the measured water table (WT) inputs. The results indicate that Dfa(i) application can improve the model performance to predict model-estimated water level (WL) and CO 2 fluxes under drained conditions [WL: r 2  = 0.89 (BWdr) and 0.94 (Modr); CO 2 : r 2  = 0.66 (BWdr) and 0.78 (MOdr)] along with model-ability to capture their seasonal trends. The prediction of WL for the rewetted period was less successful at the MOrw site, where the simulation was run for drained to rewetted, which would suggest that additional work on the water model component is still needed. Despite this, the application of Dfa(i) showed successful model simulation of CO 2 fluxes at MOrw (r 2  = 0.75) and model ability to capture seasonal trends. This work hopes to positively contribute towards potential future development of Tier 3 methodology for estimating emissions/sinks in peatlands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Ireland reported the highest non-compliance with respect to total trihalomethanes (TTHMs) in drinking water across the 27 European Union Member States for the year 2010. We carried out a GIS-based investigation of the links between geographical parameters and catchment land-uses with TTHMs concentrations in Irish drinking water. A high risk catchment map was created using peat presence, rainfall (>1400 mm) and slope (<5%) and overlain with a map comprising the national dataset of routinely monitored TTHM concentrations. It appeared evident from the map that the presence of peat, rainfall and slope could be used to identify catchments at high risk to TTHM exceedances. Furthermore, statistical analyses highlighted that the presence of peat soil with agricultural land was a significant driver of TTHM exceedances for all treatment types. PARAFAC analysis from three case studies identified a fluorophore indicative of reprocessed humic natural organic matter as the dominant component following treatment at the three sites. Case studies also indicated that (1) chloroform contributed to the majority of the TTHMs in the drinking water supplies and (2) the supply networks contributed to about 30 μg L -1 of TTHMs., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils is considered an important climate change mitigation tool to reduce emissions and create suitable conditions for carbon sequestration. Long-term monitoring is essential to capture interannual variations in GHG emissions and associated environmental variables and to reduce the uncertainty linked with GHG emission factor calculations. In this study, we present GHG balances: carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) calculated for a 5-year period at a rewetted industrial cutaway peatland in Ireland (rewetted 7 years prior to the start of the study); and compare the results with an adjacent drained area (2-year data set), and with ten long-term data sets from intact (i.e. undrained) peatlands in temperate and boreal regions. In the rewetted site, CO 2 exchange (or net ecosystem exchange (NEE)) was strongly influenced by ecosystem respiration (R eco ) rather than gross primary production (GPP). CH 4 emissions were related to soil temperature and either water table level or plant biomass. N 2 O emissions were not detected in either drained or rewetted sites. Rewetting reduced CO 2 emissions in unvegetated areas by approximately 50%. When upscaled to the ecosystem level, the emission factors (calculated as 5-year mean of annual balances) for the rewetted site were (±SD) -104 ± 80 g CO 2 -C m -2  yr -1 (i.e. CO 2 sink) and 9 ± 2 g CH 4 -C m -2  yr -1 (i.e. CH 4 source). Nearly a decade after rewetting, the GHG balance (100-year global warming potential) had reduced noticeably (i.e. less warming) in comparison with the drained site but was still higher than comparative intact sites. Our results indicate that rewetted sites may be more sensitive to interannual changes in weather conditions than their more resilient intact counterparts and may switch from an annual CO 2 sink to a source if triggered by slightly drier conditions., (© 2016 John Wiley & Sons Ltd.)