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The land use, land-use change and forestry (LULUCF) sector, as a source and a sink of greenhouse gas (GHG) emissions, is critical for achieving carbon neutrality. Many academic journals have published papers on land use carbon emission or sink (LUCES), but LUCES reviews are relatively rare, which poses great challenges in accurately understanding the research progress and future prospects. This work analyzes the research characteristics, hotspots and future perspectives of LUCES research by using a bibliometric analysis (such as DDA, VOSviewer, CiteSpace software) and a review based on the data (6115 scientific papers) during 1991–2023 from the Web of Science (WoS) platform. We found that (1) over the past 33 years, it first presented a steady growth, then fluctuating growth, and finally a rapid growth trend in the yearly number of publications in LUCES research. The USA (17.31%), China (14.96%), and the UK (7.37%) occupy a dominant position in this research field. (2) The related LUCES research is interdisciplinary, which mainly cover science and technology, meteorology and atmospheric sciences, geology, and environmental sciences and ecology disciplines. (3) The research hotspot analysis on LUCES shows that these articles mostly covered the follow three aspects: ecosystem services, climate change, and carbon neutrality. (4) A review of the past LUCES literature suggests that it is mainly focused on exploring the forefront issues in terms of the definition and boundaries, evaluation method and influencing factors, etc. This work suggests that further research could explore the main scientific problems on quantification of land-based carbon neutrality, quantitative analysis of the impact mechanisms, as well as interdisciplinary research and collaborative governance needed for carbon neutrality. [ABSTRACT FROM AUTHOR]

We describe the approach taken to develop the United Kingdom's first community Earth system model, UKESM1. This is a joint effort involving the Met Office and the Natural Environment Research Council (NERC), representing the U.K. academic community. We document our model development procedure and the subsequent U.K. submission to CMIP6, based on a traceable hierarchy of coupled physical and Earth system models. UKESM1 builds on the well‐established, world‐leading HadGEM models of the physical climate system and incorporates cutting‐edge new representations of aerosols, atmospheric chemistry, terrestrial carbon, and nitrogen cycles and an advanced model of ocean biogeochemistry. A high‐level metric of overall performance shows that both models, HadGEM3‐GC3.1 and UKESM1, perform better than most other CMIP6 models so far submitted for a broad range of variables. We point to much more extensive evaluation performed in other papers in this special issue. The merits of not using any forced climate change simulations within our model development process are discussed. First results from HadGEM3‐GC3.1 and UKESM1 include the emergent climate sensitivity (5.5 and 5.4 K, respectively) which is high relative to the current range of CMIP5 models. The role of cloud microphysics and cloud‐aerosol interactions in driving the climate sensitivity, and the systematic approach taken to understand this role, is highlighted in other papers in this special issue. We place our findings within the broader modeling landscape indicating how our understanding of key processes driving higher sensitivity in the two U.K. models seems to align with results from a number of other CMIP6 models. Plain Language Summary: The United Kingdom has taken a community approach to model development and delivery of simulations to the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The papers in this special issue characterize and evaluate the U.K. models and highlight emerging properties of the models, such as the climate sensitivity. Understanding of the reasons for an increase in sensitivity in these new models is highlighted here, and similarities to our findings from other modeling centers are discussed. Key Points: The United Kingdom has developed its first community Earth system model and delivered a traceable hierarchy of models to CMIP6We applied a process‐based evaluation strategy in model development but chose not to use historic trends or measures of climate responseThe U.K. models exhibit higher climate sensitivity than seen in CMIP5 arising in part from more positive cloud feedbacks [ABSTRACT FROM AUTHOR]

In the construction industry, a large amount of carbon dioxide is emitted, due to the embodied and operational carbon. RICS Guidance note shows the stages producing the most carbon dioxide is the operational stage and the second significant area is the production stage. Recent studies have investigated reducing the operational emissions, however there is limited research on the embodied carbon. To achieve climate targets by 2050, all operational emissions need to be phased out along with reductions in embodied carbon. This paper aims to analyze the carbon life cycle (LCA) of the case study building in the UK. Further implementing low carbon & clean technologies have been considered to reduce the embodied and operational carbon. Current state of the art carbon assessment is utilized incorporating methodologies such as 'Cradle to grave' from 'British standards' in conjunction with 'RICS Guidance note' and 'RICS Professional statement.' To measure the embodied and operational carbon using the 'cradle to grave' process, requires selecting a case study building and collecting related input data to process calculations such as construction materials and energy consumption. Results conclude that the operational stage is the largest CO₂ contributor of the whole lifecycle, therefore PV Solar panels were chosen to reduce CO₂ emissions. The product stage was the second most significant CO₂ contributor therefore low carbon strategies, such as use of recycled steel, light weight brick, and SCM's for mortar and concrete, were selected. Re-calculation of the embodied and operational carbon of the building after implementing the low carbon strategies and clean technology comparing to initial results show reductions in CO₂ emissions by 22% creating a low carbon building. Therefore, this paper brings awareness and guidance globally to clients, building designers, and the government to design sustainably using suitable low carbon solutions in all construction projects, leading to a low carbon future. [ABSTRACT FROM AUTHOR]

Land surface models are an important tool in the study of climate change and its impacts, but their use can be hampered by uncertainties in input parameter settings and by errors in the models. We apply uncertainty quantification (UQ) techniques to constrain the input parameter space and corresponding historical simulations of JULES-ES-1.0 (Joint UK Land Environment Simulator Earth System), the land surface component of the UK Earth System Model, UKESM1.0. We use an ensemble of historical simulations of the land surface model to rule out ensemble members and corresponding input parameter settings that do not match modern observations of the land surface and carbon cycle. As JULES-ES-1.0 is computationally expensive, we use a cheap statistical proxy termed an emulator, trained on the ensemble of model runs, to rule out parts of the parameter space where the simulator has not yet been run. We use history matching, an iterated approach to constraining JULES-ES-1.0, running an initial ensemble and training the emulator, before choosing a second wave of ensemble members consistent with historical land surface observations. We successfully rule out 88 % of the initial input parameter space as being statistically inconsistent with observed land surface behaviour. The result is a set of historical simulations and a constrained input space that are statistically consistent with observations. Furthermore, we use sensitivity analysis to identify the most (and least) important input parameters for controlling the global output of JULES-ES-1.0 and provide information on how parameters might be varied to improve the performance of the model and eliminate model biases. [ABSTRACT FROM AUTHOR]

Land-surface models (LSMs) are crucial components of the Earth system models (ESMs) that are used to make coupled climate-carbon cycle projections for the 21st century. The Joint UK Land Environment Simulator (JULES) is the land-surface model used in the climate and weather forecast models of the UK Met Office. JULES is also extensively used offline as a land-surface impacts tool, forced with climatologies into the future. In this study, JULES is automatically differentiated with respect to JULES parameters using commercial software from FastOpt, resulting in an analytical gradient, or adjoint, of the model. Using this adjoint, the adJULES parameter estimation system has been developed to search for locally optimum parameters by calibrating against observations. This paper describes adJULES in a data assimilation framework and demonstrates its ability to improve the model-data fit using eddy-covariance measurements of gross primary production (GPP) and latent heat (LE) fluxes. adJULES also has the ability to calibrate over multiple sites simultaneously. This feature is used to define new optimised parameter values for the five plant functional types (PFTs) in JULES. The optimised PFT-specific parameters improve the performance of JULES at over 85% of the sites used in the study, at both the calibration and evaluation stages. The new improved parameters for JULES are presented along with the associated uncertainties for each parameter. [ABSTRACT FROM AUTHOR]

Background. Strongly varying timescales of pyrogenic carbon (PyC) degradation have been observed across depositional settings. To date, PyC degradation in UK peatlands has had limited investigation. Aims. This study aims to evaluate how PyC recalcitrance relates to differing production characteristics, fuels and duration of exposure in UK peatlands. Methods. PyC samples produced from key peatland vegetation types were exposed on a peatland surface to assess molecular (by Fourier-transform infrared), leachable carbon (water-extractable organic carbon) and elemental (C, H, N, O) changes occurring over a year. Key results. PyC degradation phases were observed: (1) very rapid (=1 month) loss of leachable carbon; (2) longer-term (1-12 months) changes to PyC characteristics indicative of soil interactions. 'Severity' had a significant effect on all measured variables. Conclusions. This study indicates that PyC is susceptible to changes within short timescales in UK peatlands, particularly low-temperature PyC, but that stabilisation through soil matrix interactions may occur over longer periods (>1 year). Implications. The findings indicate that UK peatland wildfire carbon cycling research should consider early pulses of carbon to the wider environment, as well as longer-term C storage in PyC. [ABSTRACT FROM AUTHOR]

Stable carbon isotopes in plants can help evaluate and improve the representation of carbon and water cycles in land‐surface models, increasing confidence in projections of vegetation response to climate change. Here, we evaluated the predictive skills of the Joint UK Land Environmental Simulator (JULES) to capture spatio‐temporal variations in carbon isotope discrimination (Δ13C) reconstructed by tree rings at 12 sites in the United Kingdom over the period 1979–2016. Modeled and measured Δ13C time series were compared at each site and their relationships with local climate investigated. Modeled Δ13C time series were significantly correlated (p < 0.05) with tree‐ring Δ13C at eight sites, but JULES underestimated mean Δ13C values at all sites, by up to 2.6‰. Differences in mean Δ13C may result from post‐photosynthetic isotopic fractionations that were not considered in JULES. Inter‐annual variability in Δ13C was also underestimated by JULES at all sites. While modeled Δ13C typically increased over time across the UK, tree‐ring Δ13C values increased only at five sites located in the northern regions but decreased at the southern‐most sites. Considering all sites together, JULES captured the overall influence of environmental drivers on Δ13C but failed to capture the direction of change in Δ13C caused by air temperature, atmospheric CO2 and vapor pressure deficit at some sites. Results indicate that the representation of carbon‐water coupling in JULES could be improved to reproduce both the trend and magnitude of interannual variability in isotopic records, the influence of local climate on Δ13C, and to reduce uncertainties in predicting vegetation‐environment interactions. Plain Language Summary: Carbon has two stable isotopes, 12C and 13C. During the diffusion of carbon dioxide through the stomata of C3 plants, the lighter carbon isotope (12C) diffuses more easily resulting in leaf internal air that is depleted in 13C compared to the ambient air. Tree rings record this discrimination against 13C (noted Δ13C) which is used to decipher information about past climates, including atmospheric CO2 concentration when the rings formed. The Joint UK Land Environment Simulator (JULES) is a land‐surface model that predicts environmental processes (e.g., the carbon and water cycles). Comparing JULES estimates of Δ13C with tree‐ring measurements helps to improve simulations, leading to more accurate projections of ecosystem functioning under different climates. We found that JULES accurately predicted tree‐ring Δ13C in 8 out of 12 UK sites over a 38‐year period, with offsets in mean values of up to 2.6‰, but underestimated interannual variations in Δ13C at all sites. JULES captured the influence of environmental changes on tree‐ring Δ13C relatively well, although the trees' responses at individual sites varied. Results suggest that improvements are needed in JULES to reduce uncertainties in predicting the carbon and water cycles and therefore to produce more accurate projections of future climate‐vegetation interactions. Key Points: Joint UK Land Environmental Simulator (JULES) predicted well the tree‐ring Δ13C of oaks in eight out of 12 UK sites but underestimated inter‐annual variations and mean valuesJULES captured the environmental drivers of Δ13C, but the model failed to reproduce the direction of change in Δ13C at some individual sitesMore tree‐ring chronologies are needed to improve understanding of spatio‐temporal changes in Δ13C for UK broadleaf deciduous trees [ABSTRACT FROM AUTHOR]

In this paper the driving factors of carbon dioxide emissions from electricity generation in the European Union are examined for the years 2000–2018, separated into three time periods using decomposition analysis, and particularly LMDI-I. Seven driving factors are examined, namely the economic activity effect, the population effect, the electricity intensity effect, the electricity trade effect, the energy intensity effect, the generation structure effect, and the emissions factor effect. The results showed that the main driving factor leading to increased carbon dioxide emissions is the economic activity effect counterbalanced mainly by the contribution of the generation structure effect. Moreover, a decoupling analysis between economic growth and carbon dioxide emissions was carried out aiming to identify the state of each country for each period. In the third examined period (2013–2018) most countries in the EU-27 are in a state of strong decoupling. • Decomposition analysis of CO2 emissions from the power sector in the EU and the UK. • A decoupling analysis between GDP and CO 2 emissions. • Overall reduction in CO 2 emissions from power generation in the period 2000–2018. • Economic activity effect is the main driving factor for CO2 emissions. • Most countries progressed into a state of strong decoupling. [ABSTRACT FROM AUTHOR]

Estimates of greenhouse gas evasion from rivers have been refined over the past decades to constrain their role in global carbon cycle processes. However, despite 55% of the human population living in urban areas, urban rivers have had limited attention. We monitored carbon dynamics in an urbanized river (River Kelvin, 331 km2, UK) to explore the drivers of dissolved carbon lateral and vertical export. Over a 2‐year sampling period, riverine methane (CH4) and carbon dioxide (CO2) concentrations were consistently oversaturated with respect to atmospheric equilibria, leading to continual degassing to the atmosphere. Carbon stable isotopic compositions (δ13C) indicated that terrestrially derived carbon comprised most of the riverine CH4 and dissolved CO2 (CO2*) load while dissolved inorganic carbon (DIC) from groundwater was the main form of riverine DIC. The dynamics of CH4, CO2*, and DIC in the river were primarily hydrology‐controlled, that is, [CH4] and [CO2*] both increased with elevated discharge, total [DIC] decreased with elevated discharge while the proportion of biologically derived DIC increased with increasing discharge. The concentration of dissolved organic carbon (DOC) showed a weak relationship with river hydrology in summer and autumn and was likely influenced by the combined sewer overflows. Carbon emission to the atmosphere is estimated to be 3.10 ± 0.61 kg C·m−2·yr−1 normalized to water surface area, with more than 99% emitted as CO2. Annual carbon loss to the coastal estuary is approximately 4.69 ± 0.70 Gg C yr−1, with annual DIC export approximately double that of DOC. Per unit area, the River Kelvin was a smaller carbon source to the atmosphere than natural rivers/streams but shows elevated fluxes of DIC and DOC under comparable conditions. This research illustrates the role urban systems may have on riverine carbon dynamics and demonstrates the potential tight link between urbanization and riverine carbon export. [ABSTRACT FROM AUTHOR]

The future status of peatlands as carbon stores/sinks is uncertain given current and predicted environmental change. Several factors can affect the magnitude of the peatland carbon sink including disturbances such as wildfire. There is at present little evidence of how wildfire affects the emission of carbon dioxide (CO2) and methane (CH4) via perturbation to aerobic and anaerobic respiration. The greatest effects, which are likely to vary according to wildfire severity, would be expected in the immediate post-fire stages when little recovery has taken place. Here, we investigate five UK peatland wildfires (2011–2012) in the immediate post-wildfire period measuring CO2 and CH4 fluxes using static chambers. Fire severity was described using a modified form of the composite burn index. A hierarchical partitioning approach indicated time since fire was the most strongly associated variable that fluxes of both CO2, and CH4 followed by soil temperature for CO2 and fire severity for CH4. Using a liner mixed modelling approach to account for repeated measures; fire severity was a significant term for CH4 and borderline significant for CO2. Mean fluxes of CH4 were consistently lower on burnt sites. In contrast, data from a fire in the north of Scotland appeared to show the opposite relationship for CH4 with higher fluxes on the burnt sites. These results suggest that wildfire can affect gaseous carbon fluxes, but the responses can be variable in both space and time and that disruption to anaerobic processes may be site and/or fire dependent. [ABSTRACT FROM AUTHOR]

Purpose: The global interest in climate change makes carbon information important for decision-making. This study examines to what extent companies voluntarily disclose and manage greenhouse gas (GHG) information and whether board diversity and industry type explain variations in the level of disclosure and management of GHG information. Design/methodology/approach: Cross-sectional data analysis is used for the Financial Stock Exchange 350 (UK FTSE 350) in 2017. Disclosure of GHG information is measured using the scores of the Carbon Disclosure Project (CDP), whereas board diversity is measured using gender diversity, board tenure and board skills. The control variables include firm size, leverage, industry type, board meetings, board size, board independence and CEO duality. Ordinal logistic regression (OLR) is used for data analysis. Findings: The results indicate that representation of female directors in the board of directors positively influences disclosure and management of GHG information. Conversely, a high percentage of directors with a financial and industrial background negatively affects GHG information, while board tenure has no significant effect on GHG information. Concerning the control variables, only firm size and industry type are significant in their relationships to GHG information. Research limitations/implications: The main limitation of the study is investigating only few variables of board diversity. Future studies could investigate other variables such as cultural diversity and age diversity. Furthermore, cross-sectional data analysis cannot capture the dynamic casual impact between the determinants of disclosure and management of GHG information. Future studies could use long-term data, which may yield results that are more significant. Originality/value: The study emphasizes the importance of the role of female directors in ensuring more transparency toward climate change activities. The findings of this study could be of interest to policymakers and stakeholders and could be used to take initiatives to reduce gender bias and increase the percentage of women in the boardroom. It is also likely to be beneficial for investors and stakeholders to evaluate carbon footprint of businesses and to assess the extent to which they meet their environmental responsibility. [ABSTRACT FROM AUTHOR]

In this article, we modify bioenergy model MiscanFor investigating global and UK potentials for Miscanthus × giganteus as a bioenergy resource for carbon capture in the 21st century under the RCP 2.6 climate scenario using SSP2 land use projections. UK bioenergy land projections begin in the 2040s, 60 year average is 0.47 Mega ha rising to 1.9 Mega ha (2090s). Our projections estimate UK energy generation of 0.09 EJ/year (60 year average) and 0.37 EJ/year (2090s), under stable miscanthus yields of 12 t ha−1 year−1. We estimate aggregated UK soil carbon (C) increases of 0.09 Mt C/year (60 year average) and 0.14 Mt C/year (2090s) with C capture plus sequestration rate of 2.8 Mt C/year (60 year average) and 10.49 Mt C/year (2090s). Global bioenergy land use begins in 2010, 90 year average is 0.13 Gha rising to 0.19 Gha by the 2090s, miscanthus projections give a 90 year average energy generation of 16 EJ/year, rising to 26.7 EJ/year by the 2090s. The largest national capabilities for yield, energy and C increase are projected to be Brazil and China. Ninety year average global miscanthus yield of 1 Gt/year will be 1.7 Gt/year by the 2090s. Global soil C sequestration increases less with time, from a century average of 73.6 Mt C/year to 42.9 Mt C/year by the 2090s with C capture plus sequestration rate of 0.54 Gt C/year (60 year average) and 0.81 Gt C/year (2090s). M. giganteus could provide just over 5% of the bioenergy requirement by the 2090s to satisfy the RCP 2.6 SSP2 climate scenario. The choice of global land use data introduces a potential source of error. In reality, multiple bioenergy sources will be used, best suited to local conditions, but results highlight global requirements for development in bioenergy crops, infrastructure and support. [ABSTRACT FROM AUTHOR]

Global perturbations to the Early Jurassic environment (~201 to ~174 Ma), notably during the Triassic-Jurassic transition and Toarcian Oceanic Anoxic Event, are well studied and largely associated with volcanogenic greenhouse gas emissions released by large igneous provinces. The long-term secular evolution, timing, and pacing of changes in the Early Jurassic carbon cycle that provide context for these events are thus far poorly understood due to a lack of continuous high-resolution δ13C data. Here we present a δ13CTOC record for the uppermost Rhaetian (Triassic) to Pliensbachian (Lower Jurassic), derived from a calcareous mudstone succession of the exceptionally expanded Llanbedr (Mochras Farm) borehole, Cardigan Bay Basin, Wales, United Kingdom. Combined with existing δ13CTOC data from the Toarcian, the compilation covers the entire Lower Jurassic. The dataset reproduces large-amplitude δ13CTOC excursions (>3‰) recognized elsewhere, at the Sinemurian-Pliensbachian transition and in the lower Toarcian serpentinum zone, as well as several previously identified medium-amplitude (~0.5 to 2‰) shifts in the Hettangian to Pliensbachian interval. In addition, multiple hitherto undiscovered isotope shifts of comparable amplitude and stratigraphic extent are recorded, demonstrating that those similar features described earlier from stratigraphically more limited sections are nonunique in a long-term context. These shifts are identified as long-eccentricity (~405-ky) orbital cycles. Orbital tuning of the δ13CTOC record provides the basis for an astrochronological duration estimate for the Pliensbachian and Sinemurian, giving implications for the duration of the Hettangian Stage. Overall the chemostratigraphy illustrates particular sensitivity of the marine carbon cycle to long-eccentricity orbital forcing. [ABSTRACT FROM AUTHOR]

Litter breakdown in the streambed is an important pathway in organic carbon cycling and energy transfer in the biosphere that is mediated by a wide range of streambed organisms. However, most research on litter breakdown to date has focused on a small fraction of the taxa that drive it (e.g. microbial vs. macroinvertebrate‐mediated breakdown) and has been limited to the benthic zone (BZ). Despite the importance of the hyporheic zone (HZ) as a bioreactor, little is known about what, or who, mediates litter breakdown in this compartment and whether breakdown rates differ between the BZ and HZ.Here, we explore the relationship between litter breakdown and the variation in community structure of benthic and hyporheic communities by deploying two standardized bioassays (cotton strips and two types of commercially available tea bags) in 30 UK streams that encompass a range of environmental conditions. Then, we modelled these assays as a response of the streambed compartment and the biological features of the streambed assemblage (Prokaryota, Protozoa and Eumetazoa invertebrates) to understand the generality and efficiency of litter processing across communities.Litter breakdown was much faster in the BZ compared with the HZ (around 5 times higher for cotton strips and 1.5 times faster for the tea leaves). However, differences in litter breakdown between the BZ and the HZ were mediated by the biological features of the benthos and the hyporheos. Biomass of all the studied biotic groups, α‐diversity of Eumetazoa invertebrates and metabolic diversity of Prokaryota were important predictors that were positively related to breakdown coefficients demonstrating their importance in the functioning of the streambed ecosystem.Our study uses a novel multimetric bioassay that is able to disentangle the contribution by Prokaryota, Protozoa and Eumetazoa invertebrates to litter breakdown. In doing so, our study reveals new insights into how organic matter decomposition is partitioned across biota and streambed compartments. [ABSTRACT FROM AUTHOR]

Benthic communities play a major role in organic matter remineralisation and the mediation of many aspects of shelf sea biogeochemistry. Few studies have considered how changes in community structure associated with different levels of physical disturbance affect sediment macronutrients and carbon following the cessation of disturbance. Here, we investigate how faunal activity (sediment particle reworking and bioirrigation) in communities that have survived contrasting levels of bottom fishing affect sediment organic carbon content and macronutrient concentrations ([NH-N], [NO-N], [NO-N], [PO-P], [SiO-Si]). We find that organic carbon content and [NO-N] decline in cohesive sediment communities that have experienced an increased frequency of fishing, whilst [NH-N], [NO-N], [PO-P] and [SiO-Si] are not affected. [NH-N] increases in non-cohesive sediments that have experienced a higher frequency of fishing. Further analyses reveal that the way communities are restructured by physical disturbance differs between sediment type and with fishing frequency, but that changes in community structure do little to affect bioturbation and associated levels of organic carbon and nutrient concentrations. Our results suggest that in the presence of physical disturbance, irrespective of sediment type, the mediation of macronutrient and carbon cycling increasingly reflects the decoupling of organism-sediment relations. Indeed, it is the traits of the species that reside at the sediment-water interface, or that occupy deeper parts of the sediment profile, that are disproportionately expressed post-disturbance, that are most important for sustaining biogeochemical functioning. [ABSTRACT FROM AUTHOR]

Results from a 1D setup of the European Regional Seas Ecosystem Model (ERSEM) biogeochemical model were compared with new observations collected under the UK Shelf Seas Biogeochemistry (SSB) programme to assess model performance and clarify elements of shelf-sea benthic biogeochemistry and carbon cycling. Observations from two contrasting sites (muddy and sandy) in the Celtic Sea in otherwise comparable hydrographic conditions were considered, with the focus on the benthic system. A standard model parameterisation with site-specific light and nutrient adjustments was used, along with modifications to the within-seabed diffusivity to accommodate the modelling of permeable (sandy) sediments. Differences between modelled and observed quantities of organic carbon in the bed were interpreted to suggest that a large part (>90%) of the observed benthic organic carbon is biologically relatively inactive. Evidence on the rate at which this inactive fraction is produced will constitute important information to quantify offshore carbon sequestration. Total oxygen uptake and oxic layer depths were within the range of the measured values. Modelled depth average pore water concentrations of ammonium, phosphate and silicate were typically 5-20% of observed values at the muddy site due to an underestimate of concentrations associated with the deeper sediment layers. Model agreement for these nutrients was better at the sandy site, which had lower pore water concentrations, especially deeper in the sediment. Comparison of pore water nitrate with observations had added uncertainty, as the results from process studies at the sites indicated the dominance of the anammox pathway for nitrogen removal; a pathway that is not included in the model. Macrofaunal biomasses were overestimated, although a model run with increased macrofaunal background mortality rates decreased macrofaunal biomass and improved agreement with observations. The decrease in macrofaunal biomass was compensated by an increase in meiofaunal biomass such that total oxygen demand remained within the observed range. The permeable sediment modification reproduced some of the observed behaviour of oxygen penetration depth at the sandy site. It is suggested that future development in ERSEM benthic modelling should focus on: (1) mixing and degradation rates of benthic organic matter, (2) validation of benthic faunal biomass against large scale spatial datasets, (3) incorporation of anammox in the benthic nitrogen cycle, and (4) further developments to represent permeable sediment processes. [ABSTRACT FROM AUTHOR]

In-stream processing of allochthonous dissolved organic carbon (DOC) and particulate organic carbon (POC) in peat-sourced headwaters has been shown to be a significant part of the terrestrial carbon cycle, through photo- and bio-degradation, with both DOC and POC converted to carbon dioxide (CO). This study reports a series of 70-h, in situ experiments investigating rates of degradation in unfiltered surface water from a headwater stream in the River Tees, North Pennines, UK. Half the samples were exposed to the normal day/night cycle (ambient); half were continuously dark. The study found that the DOC concentration of samples in the ambient treatment declined by 64 % over the 70 h, compared with 6 % decline for the samples kept in the dark. For POC, the loss in the ambient treatment was 13 %. The average initial rate of loss of DOC in the ambient treatment during the first day of the experiment was 3.36 mg C/l/h, and the average rate of photo-induced loss over the whole 70 h was 1.25 mg C/l/h. Scaling up these losses, the estimate of total organic carbon loss from UK rivers to the atmosphere is 9.4 Tg CO/year which would be 0.94 % of the global estimate of CO emissions from streams and rivers from the 2013 IPCC report. Initial rate kinetics in the light were as high as 3rd order, but the study showed that no single rate law could describe the whole diurnal degradation cycle and that separate rate laws were required for night and day processes. The comparison of dark and ambient treatment processes showed no evidence of photo-stimulated bacterial degradation. [ABSTRACT FROM AUTHOR]

Northern peatlands are recognized as globally important stores of terrestrial carbon (C), yet we have limited understanding of how global changes, including land use, affect C cycling processes in these ecosystems. Making use of a long-term (>50 year old) peatland land management experiment in the UK, we investigated, using a CO pulse chase approach, how managed burning and grazing influenced the short-term uptake and cycling of C through the plant-soil system. We found that burning affected the composition and growth stage of the plant community, by substantially reducing the abundance of mature ericoid dwarf-shrubs. Burning also affected the structure of the soil microbial community, measured using phospholipid fatty acid analysis, by reducing fungal biomass. There was no difference in net ecosystem exchange of CO but burning was associated with an increase in photosynthetic uptake of CO and increased transfer of C to the soil microbial community relative to unburned areas. In contrast, grazing had no detectable effects on any measured C cycling process. Our study provides new insight into how changes in vegetation and soil microbial communities arising from managed burning affect peatland C cycling processes, by enhancing the uptake of photosynthetic C and the transfer of C belowground, whilst maintaining net ecosystem exchange of CO at pre-burn levels. [ABSTRACT FROM AUTHOR]

SummaryUnderstanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid-latitude ecosystems in response to global warming. We measured the carbon isotope distributions (12C, 13C and 14C) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2-cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The 13C content and 14C age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil-forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO2 emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2–50 years range, so the soils are fairly ineffective sinks for excess CO2 in the atmosphere. Under the predicted future ‘greenhouse’ climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO2 and are therefore likely to accelerate global warming. [ABSTRACT FROM AUTHOR]

Peatlands are globally‐important terrestrial carbon stores as well as regional sources of potable water supply. Water draining from peatlands is rich in dissolved organic carbon (DOC), which can be problematic for water treatment. However, it is unclear how future climate and sulfate deposition changes may impact DOC in peatland‐derived potable water. The United Kingdom (UK) is a global hotspot that consumes 79% of all potable water derived directly from peatlands. Here, a physically‐based hydrological model and a biogeochemical organic carbon model were used to predict discharge and DOC concentration in nine hotspots of peatland‐derived potable water use in the UK under a range of 21st century climate and sulfate deposition scenarios. These nine catchments supply 72% of all peatland‐derived water consumed in the UK and 57% of the global total, equivalent to the total domestic consumption of over 14 million people. Our simulations indicate that annual discharges will decrease and that mean annual DOC concentrations will increase under all future scenarios (by as much as 53.4% annually for the highest emissions scenario) in all catchments. Large increases (by as much as a factor of 1.6) in DOC concentration in the 2090s over the baseline period are projected for autumn and winter, seasons when DOC concentrations are already high in the baseline datasets such that water treatment works often reach their capacity to cope. The total DOC flux is largely insensitive to future climate change because the projected increase in DOC concentration is mostly counterbalanced by the projected decrease in discharge. Plain Language Summary: Peatlands are important sources of potable water in some parts of the world. The UK is a particular hotspot and consumes around 79% of all drinking water provided by peatlands globally. Water draining from peatlands is rich in dissolved organic carbon (DOC). DOC from peatlands represents an important component of the global carbon cycle and is problematic for water treatment. Using physically‐based hydrological and organic carbon models combined with future climate and sulfate deposition scenarios for the UK, we demonstrate that river DOC concentrations are likely to increase under all future scenarios, particularly in autumn and early winter. These changes will create problems for water treatment because many water treatment plants that remove DOC already reach capacity during these seasons. Furthermore, large decreases in river discharge are projected in future summers for these important catchments, creating additional pressure for UK water resources. Key Points: Mean annual DOC concentrations in nine UK peatland rivers will increase in the future, by as much as 53% for the highest emissions scenarioLarge increases in mean DOC concentrations are projected in future autumn and winter, periods when DOC concentrations are already highLarge decreases in mean discharge are projected for April to September, periods when discharge is already low [ABSTRACT FROM AUTHOR]