Peatland carbon stores are under widespread anthropogenic pressure, resulting in degradation and carbon loss. This paper presents DO14C (Dissolved Organic Carbon) dates from waters draining two eroded blanket peatland catchments in the UK. Both catchments are characterized by severe gully erosion but one additionally has extensive surface erosion on unvegetated surfaces. DO14C values ranged from 104.3 to 88.6 percent modern (present to 976 Before Present). The oldest DOC dates came from the catchment characterized by both gully and surface erosion and are among the oldest reported from waters draining temperate peatlands. Together with peat age‐depth data from across the peatland landscape, the DO14C ages identify where in the peat profile carbon loss is occurring. Source depths were compared with modeled water table data indicating that in the catchment where gully erosion alone dominated, mean water table was a key control on depth of DOC production. In the system exhibiting both gully erosion and surface erosion, DOC ages were younger than expected from the age of surficial peats and measured water tables. This may indicate either that the old organic matter exposed at the surface by erosion is less labile or that there are modifications of hydrological flow pathways. Our data indicate that eroded peatlands are losing carbon from depth, and that erosion form may be a control on carbon loss. Our approach uses point measurements of DO14C to indicate DOC source depths and has the potential to act as an indicator of peatland function in degraded and restored systems.

A diatom record from Moss Lake, Washington, USA spans the last 14,500 cal year and revealed Holocene climate change in the Pacific Northwest (PNW), including evidence for periodicities related to ocean-atmosphere teleconnections and/or variations in solar output. Three main climate phases were identified: (i) Late Pleistocene to early Greenlandian (until 10,800 cal year BP, spanning GI-1, GS-1), with a cold climate and low diatom abundance; (ii) early Greenlandian to Northgrippian (10,800–7500 cal year BP), shifting to a warmer climate; and (iii) late Northgrippian and Meghalayan from 7500 cal year BP onwards, with a cooler, moist climate. These climate shifts are in good agreement with the pollen record from the same core and other regional studies. Fluctuations in Discostella pseudostelligera and Aulacoseira taxa suggest climate cycles of different frequency and amplitude throughout the record. Spectral and wavelet analyses revealed periodicities of approximately 1400 and 400–500 years. We interpret the ~ 1400-year and ~ 400–500-year cycles to reflect alternating periods of enhanced (and reduced) convective mixing in the water column, associated with increased (and decreased) storms, resulting from ocean–atmosphere teleconnections in the wider Pacific region. The ~ 1400-year periodicity is evident throughout the Late Pleistocene and late Northgrippian/Meghalayan, reflecting high-amplitude millennial shifts from periods of stable thermal stratification of the water column (weak wind intensity) to periods of convective mixing (high wind intensity). The millennial cycle diminishes during the Greenlandian, in association with the boreal summer insolation maximum, consistent with suppression of ENSO-like dynamics by enhanced trade winds. Ocean–atmosphere teleconnection suppression is recorded throughout the PNW, but there is a time discrepancy with other records, some that reveal suppression during the Greenlandian and others during the Northgrippian, suggesting endogenic processes may also modulate the Moss Lake diatom record. The large amplitude of millennial variability indicated by the lake data suggests that regional climate in the PNW was characterised over the longer term by shifting influences of ocean–atmosphere dynamics and that an improved understanding of the external forcing is necessary for understanding past and future climate conditions in western North America.

Restoration of eroded blanket peatlands through revegetation and gully blocking is observed to also deliver significant natural flood management (NFM) benefits (reduce and delay floodpeaks). But there is a lack of clear understanding regarding how different catchment processes interact/counteract under each intervention scenario. We seek to provide more insight by rigorously calibrating TOPMODEL rainfall‐runoff model to different experimental catchments each representing an intervention scenario. Through numerical experimentation with the calibrated parameters, we estimate the impact‐magnitude of different processes. Our findings confirm the NFM benefits of these restoration‐focused interventions. In both interventions and in our largest storms, both the delay and reduced floodpeaks are primarily due to surface roughness reducing the floodwave speed thus thickening the overland flow; we conceptualize this as an increase in a “kinematic storage.” Impact of gully blocking in increasing kinematic storage is very significant and comparable to that of revegetation alone. Interventions' impact on “static storage” (interception + ponding + evapotranspiration) becomes important for smaller storms. Although interventions always increase lag times, they can be less effective in reducing peak magnitude when maximum rainfall intensity is sustained for durations longer than mean catchment delay. We propose two approaches to further increase catchment's static and kinematic storage. Finally, while our field‐scale numerical study contributes to the evidence‐base for NFM's effectiveness, it also provides a basis for modeling these interventions in the future. Such catchment‐scale numerical studies are necessary to extend our findings to spatial scales where flooding can cause socioeconomic damage, and to provide a tool for optimizing the distributed configuration of these interventions.

The UK supports 15% of the world’s blanket peat cover but much of this vital resource is significantly degraded. In damaged peatlands runoff is quickly evacuated from hillslopes across bare peat surfaces and through erosional gullies, exacerbating downstream flooding. The restoration of damaged UK peatlands is a major conservation concern, and landscape-scale restoration by revegetation and damming of gullies is extensive in areas of upland Britain. There is increasing evidence that the restoration techniques can significantly slow the flow of water in addition to providing other ecosystem service benefits. More recently, focus has shifted from stabilising eroding surfaces to the reintroducing Sphagnum moss as part of multi-benefit restoration initiatives. This paper reports the results of long-term post-restoration monitoring on the Kinder Plateau in the southern Pennines of the U.K. Two sites were revegetated using lime-seed-fertiliser-mulch in 2011 and one of the sites was also gully blocked in 2012 and had a further phase of restoration in the form of intensive Sphagnum planting in 2015. A third unrestored control site was also monitored. We present post-intervention biogeomorphological changes spanning 10 years, showing the long-term trajectories of vegetation cover, runoff, sediment production, and water table. The trajectories of recovery for different functions differ in form and rate. At both treatment sites, vegetation cover increases rapidly then slows as full cover is approached. Sediment production is quickly reduced to levels comparable to intact peatlands within two years and bare peat cover becomes negligible after ~7 years. Key runoff metrics (e.g. peak discharge and lag time) show similar immediate step changes as a result of increased surface roughness from the rapid vegetation expansion, followed by more gradual improvements as species richness develops through time. The addition of gully blocking enhances the impact of re-vegetation alone, amplifying the step change, but there are no further benefits apparent in the longer-term trajectory. The introduction of Sphagnum provides further roughness, leading to marked increases in lag times and attenuation of runoff. There is also preliminary evidence that the Sphagnum inhibits surface drying, providing resilience to future climatic and anthropogenic stressors. This study provides the first evidence that the reintroduction of Sphagnum in degraded headwater peatlands can provide additional Natural Flood Management benefits compared to standard restoration techniques aimed at stabilising eroding surfaces. We also show that water table recovery is not at odds with flow attenuation. We also note the importance of control assessing the impact of restoration interventions and the need for investment in longer-term (>10 year) monitoring to better understand the recovery of restored peatlands.

Over the past 15 years there has been a proliferation of projects aiming to restore the structure and function of UK upland blanket mires, primarily by revegetation of bare peat and the blocking of erosion gullies. These restoration measures have potential to alter stormflow responses and contribute to Natural Flood Management, but their impacts on storm hydrographs are poorly quantified. This paper reports a before-after-control-intervention (BACI) study from three experimental headwater micro-catchments in the South Pennines (UK) representing the first rigorous experimental assessment of the impact of blanket peat restoration on catchment runoff. We evaluate the hydrological impacts of two standard restoration interventions; revegetation of bare peat, and revegetation of bare peat with additional gully blocking. Following revegetation there was a significant decrease in depth to water table and an increase in the prevalence of hillslope overland flow production. There were no significant changes in storm runoff coefficient following either restoration treatment. Storm hydrographs following revegetation had significantly longer lag times (106% increase relative to the control), reduced peak flows (27% decrease relative to the control), and attenuated hydrograph shapes. With the addition of gully blocking the effect is almost doubled. Lag times increased by a further 94% and peak flows reduced by an additional 24% relative to the control. We argue that the primary process controlling the observed changes in storm hydrograph behaviour is retardation of overland stormflow due to increased surface roughness. The significant changes to lag times and peak flow provide evidence that the restoration of degraded headwater peatlands can contribute to Natural Flood Management and the reduction of downstream flood risk, subject to wider catchment scale effects and sub-catchment storm hydrograph synchronicity. (C) 2018 The Authors. Published by Elsevier B.V.

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Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km2) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO2(aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition.

Peatlands are important terrestrial carbon stores and dissolved organic carbon (DOC) is one of the most important contributors to carbon budgets in peatland systems. Many studies have investigated factors affecting DOC concentration in peatland systems, yet hillslope position has been thus far overlooked as a variable that could influence DOC cycling. This study investigates the importance of hillslope position with regard to DOC cycling. Two upland peat hillslopes were studied in the Peak District, UK, to determine what impact, if any, hillslope position had upon DOC concentration. Hillslope position was found to be a significant factor affecting variation in soil pore water DOC concentration, with bottom-slope positions having significantly lower DOC concentrations than up-slope because of dilution of DOC as water moves down-slope and is flushed out of the system via lateral throughflow. Water table drawdown on steeper mid-slopes increased DOC concentrations through increased DOC production and extended residence times allowing a build-up of humic-rich DOC compounds. Hillslope position did not significantly affect DOC concentrations in surface runoff water because of the dilution of near-surface soil pore water by precipitation inputs, while stream water had similar water chemistry properties to soil pore water under low-flow conditions. (C) 2015 Elsevier B.V. All rights reserved.

There is evidence that damaged peatlands can negatively affect the delivery of water related ecosystem services. There is interest in peatland restoration to meet different regulatory targets, including the Water Framework Directive (WFD). A comprehensive assessment of the economic benefits of restoration is missing. This paper synthesises hydrological and bio-geochemical knowledge on peatland restoration, as well as insights in the monetary valuation of water quality improvements in freshwater systems. This is used to identify challenges in valuing water quality related benefits from peatland restoration. The paper concludes that there is strong evidence for rapid ecological responses to peatland restoration related to reduced suspended sediment loads, and sufficient evidence that re-wetting will prevent further decline in water quality. Two main challenges arise for valuation: (1) incomplete evidence of effects of restoration on final ecosystem services and benefits, and (2) the spatial and temporal differences in peatlands' responses. We suggest developing valuation scenarios on a case-by-case basis, using best available evidence of the changes associated with restoration described by a categorization of peatland status similar to the ecological status ladders developed for the WFD. These would need to be tested with the public and should include an element of uncertainty in services provision.

Hydrochemical sampling of South Pennine (UK) headwater streams draining eroded upland peatlands demonstrates these systems are nitrogen saturated, with significant leaching of dissolved inorganic nitrogen (DIN), particularly ammonium, during both stormflow and baseflow conditions. DIN leaching at sub-catchment scale is controlled by geomorphological context; in catchments with low gully densities ammonium leaching dominates whereas highly gullied catchments leach ammonium and nitrate since lower water tables and increased aeration encourages nitrification. Stormflow flux calculations indicate that: approximately equivalent amounts of nitrate are deposited and exported; ammonium export significantly exceeds atmospheric inputs. This suggests two ammonium sources: high atmospheric loadings; and mineralisation of organic nitrogen stored in peat. Downstream trends indicate rapid transformation of leached ammonium into nitrate. It is important that low-order headwater streams are adequately considered when assessing impacts of atmospheric loads on the hydrochemistry of stream networks, especially with respect to erosion, climate change and reduced precipitation.

Atmospheric deposition of trace metals and metalloids from anthropogenic sources has led to the contamination of many European peatlands. To assess the fate and behaviour of previously deposited arsenic and lead, we constructed catchment-scale mass budgets for a degraded peatland in Northern England. Our results show a large net export of both lead and arsenic via runoff (282 +/- 21.3 gPb ha(-1) y(-1) and 60.4 +/- 10.5 gAs ha(-1) y(-1)), but contrasting controls on this release. Suspended particulates account for the majority of lead export, whereas the aqueous phase dominates arsenic export. Lead release is driven by geomorphological processes and is a primary effect of erosion. Arsenic release is driven by the formation of a redox-dynamic zone in the peat associated with water table drawdown, a secondary effect of gully erosion. Degradation of peatland environments by natural and anthropogenic processes has the potential to release the accumulated pool of legacy contaminants to surface waters. (C) 2011 Elsevier Ltd. All rights reserved.

Upland peat soils in close proximity to urban and industrial areas can be contaminated with high concentrations of atmospherically deposited lead. The peat soils of the Peak District (UK) are characterised by extensive eroding gullies. Fine-resolution digital topographic data were used to map the extent and depth of these gullies. Peat samples from eroding gully walls and suspended sediments were collected and analysed for lead content. Variability in lead concentrations of gully wall material and suspended sediments can be explained by differences in mean upslope gully depth. The lead content of suspended sediment exported from catchments characterised by shallow peat gullies is higher than that exported from catchments with deep peat gullies. The empirical relationship between sediment-associated lead concentration and mean upslope gully depth was combined with the gully depth mapping to produce a predictive spatial model of suspended sediment lead concentrations across the Peak District. This model may be particularly useful for catchment managers who are currently involved in the restoration of eroding peat soils in the Peak District uplands.

We assessed the vulnerability of blanket peat to climate change in Great Britain using an ensemble of 8 bioclimatic envelope models. We used 4 published models that ranged from simple threshold models, based on total annual precipitation, to Generalised Linear Models (GLMs, based on mean annual temperature). In addition, 4 new models were developed which included measures of water deficit as threshold, classification tree, GLM and generalised additive models (GAM). Models that included measures of both hydrological conditions and maximum temperature provided a better fit to the mapped peat area than models based on hydrological variables alone. Under UKCIP02 projections for high (A1F1) and low (B1) greenhouse gas emission scenarios, 7 out of the 8 models showed a decline in the bioclimatic space associated with blanket peat. Eastern regions (Northumbria, North York Moors, Orkney) were shown to be more vulnerable than higher-altitude, western areas (Highlands, Western Isles and Argyle, Bute and The Trossachs). These results suggest a long-term decline in the distribution of actively growing blanket peat, especially under the high emissions scenario, although it is emphasised that existing peatlands may well persist for decades under a changing climate. Observational data from long-term monitoring and manipulation experiments in combination with process-based models are required to explore the nature and magnitude of climate change impacts on these vulnerable areas more fully.

This paper presents information on the spatial and seasonal patterns of river water chemistry at approximately 800 sites in North West England based on data from the Environment Agency regional monitoring programme. Within a GIS framework, the linkages between average water chemistry (pH, sulphate, base cations, nutrients and metals) catchment characteristics (topography, land cover, soil hydrology, base flow index and geology), rainfall, deposition chemistry and geo-spatial information on discharge consents (point sources) are examined. Water quality maps reveal that there is a clear distinction between the uplands and lowlands. Upland waters are acidic and have low concentrations of base cations, explained by background geological sources and land cover. Localised high concentrations of metals occur in areas of the Cumbrian Fells which are subjected to mining effluent inputs. Nutrient concentrations are low in the uplands with the exception sites receiving effluent inputs from rural point sources. In the lowlands, both past and present human activities have a major impact on river water chemistry, especially in the urban and industrial heartlands of Greater Manchester, south Lancashire and Merseyside. Over 40% of the sites have average orthophosphate concentrations > 0.1 mg-P l− 1. Results suggest that the dominant control on orthophosphate concentrations is point source contributions from sewage effluent inputs. Diffuse agricultural sources are also important, although this influence is masked by the impact of point sources. Average nitrate concentrations are linked to the coverage of arable land, although sewage effluent inputs have a significant effect on nitrate concentrations. Metal concentrations in the lowlands are linked to diffuse and point sources. The study demonstrates that point sources, as well as diffuse sources, need to be considered when targeting measures for the effective reduction in river nutrient concentrations. This issue is clearly important with regards to the European Union Water Framework Directive, eutrophication and river water quality.

Concentration depth profiles and inventories of solid-phase As, Sb, Pb, and Cu were determined in Pb-210-dated cores from an ombrotrophic peat bog in northwest England. Cores were collected from the peat dome and adjacent to an eroding gully. Down-core distributions of As, Sb, Pb, and Cu in the dome core are almost identical. The water table is close to the dome surface with only short-term draw-down. Under these conditions, As, Sb, Pb, and Cu are immobile, allowing the reconstruction of trends in historical contaminant deposition. The peak in atmospheric deposition of As, Sb, Pb, and Cu (4.59, 2.78, 147, and 26.7 mg m(-2) y(-1), respectively) occurred during the late 19th century. Stable Pb isotope ratios reveal that Pb deposition during this period was from indigenous and foreign sources. The mean water table is much lower at the gully edge, and there are pronounced interannual fluctuations. These conditions have not affected the integrity of the Pb and Cu records but have caused postdepositional mobilization and redistribution of As and Sb. Cumulative inventories show significant loss of As and Sb at the gully edge site. Long-term water table draw-down in ombrotrophic peat bogs has the potential to alter the geochemistry and fate of previously deposited As and Sb.