Blanket Peat Erosion Research Articles

Peatland gully restoration with stone and timber dams (Kinder Plateau, UK)

Blanket peat erosion is widespread in the British Isles. Eroded gullies have formed largely from the action of running water, with anthropogenic influences thought to have initiated and accelerated erosion. Currently, many blanket peatlands are undergoing restoration using aerial applications of lime, seed, fertiliser, and hand spreading of heather mulch (LSFM) on bare peat flats and blocking gullies with dams. Dams help stabilise areas of bare peat, trap sediment, reduce runoff velocities, raise water tables, and promote the re-vegetation of peat-forming plant species. Few studies have examined how gully blocks change over time and what this means for the functions they provide. We randomly sampled 500 of >2500 small stone and timber dams 8–9 years after installation in an eroding blanket peatland. We measured: vegetation cover and abundance, sediment accumulation behind dams, and available water storage capacity in dam pools as determined by gully morphology. On average, 92% and 93% of gully floors and 85% and 95% of gully walls were fully vegetated, while mean sediment depths were 22 and 20 cm, representing 42% and 44% infill for stone and timber dams, respectively. 2% of dams had failed, suggesting that failure is rare within the first decade. Most retained upstream pools, filling 18% (stone) and 44% (timber) of remaining storage. Sediment accumulation depths (and, conversely, available storage) did not differ significantly between stone and timber dams (95% CI) nor with distance down the gully. Results showed broadly consistent storage depth behind blocks independent of gully properties or dam design. These results suggest that sedimentation depths behind dams quickly reach equilibrium with subsequent sediment inputs balanced by the flux over the dam. Runoff attenuation functions from gully blocking were maintained for almost a decade. Therefore, re-vegetated gully blocked systems likely represent a stable equilibrium condition for the restored peatland so that the restored functions are a long-term benefit of peatland restoration.

Erosion of Northern Hemisphere blanket peatlands under 21st‐century climate change

AbstractPeatlands are important terrestrial carbon stores particularly in the Northern Hemisphere. Many peatlands, such as those in the British Isles, Sweden, and Canada, have undergone increased erosion, resulting in degraded water quality and depleted soil carbon stocks. It is unclear how climate change may impact future peat erosion. Here we use a physically based erosion model (Pan‐European Soil Erosion Risk Assessment‐PEAT), driven by seven different global climate models (GCMs), to predict fluvial blanket peat erosion in the Northern Hemisphere under 21st‐century climate change. After an initial decline, total hemispheric blanket peat erosion rates are found to increase during 2070–2099 (2080s) compared with the baseline period (1961–1990) for most of the GCMs. Regional erosion variability is high with changes to baseline ranging between −1.27 and +21.63 t ha−1 yr−1 in the 2080s. These responses are driven by effects of temperature (generally more dominant) and precipitation change on weathering processes. Low‐latitude and warm blanket peatlands are at most risk to fluvial erosion under 21st‐century climate change.

Blanket peat erosion: Theoretical considerations and observations from selected conservation sites in Slieveanorra Forest National Nature Reserve, County Antrim

Geomorphological investigation of blanket peat at three conservation plots in Slieveanorra Forest National Nature Reserve, County Antrim, suggests that various stages of peat erosion are concurrent. The proximity of undisturbed peat, gullies and haggs, peat flats, redistributed peat and regenerated peat is described. Morphological evidence may be interpreted in terms of a natural cycle or system of peat erosion but pollen analysis suggests a linkage between agricultural activity and the commencement of erosion. A C14 date of 2108 BP implies a much earlier date for peat erosion than generally considered. Erosion processes and origins are discussed and related to theories of upland blanket peat erosion.

Spatial variability of fluvial blanket peat erosion rates for the 21st Century modelled using PESERA-PEAT

Many peatlands across the world suffer from degradation. Blanket peatlands are found mainly in high latitude oceanic areas and subpolar islands. Exacerbated erosion of blanket peatlands is common particularly where they have been disturbed by human influence or where climate has become more marginal for their functioning. A recently developed fluvial blanket peat erosion model, PESERA-PEAT was applied across 845km2 of blanket peatlands in the North Pennines of northern England. The aim was to evaluate the spatial and temporal variability of erosion rates under climate change and land management scenarios. Climate change data to the end of the 21st Century, derived from UKCP09 median emission projections aligned to the UK Met Office's historical meteorological dataset, were downscaled to 100m cells. Land management scenarios were developed which included intensified and extensified grazing, artificial drainage and prescribed burning. The modelling results showed that under current management, 21st Century climate change would slightly increase the overall fluvial erosion rates for the study region from the climatic baseline (2.2tha−1yr−1) to the 2080s (2.3tha−1yr−1). However, the predicted response to climate change was spatially very variable. Predicted erosion rates decreased at locations that are currently wet and cold while they increased in some warmer and drier locations by >50%. Summer desiccation was found to become more important for the study region under climate change. Thus, predicted autumn sediment yields became the biggest component of the annual budget by the 2080s. Less intensive management was shown to reduce blanket peat erosion but potentially enhance wildfire severity. The results demonstrated that land management change will be useful in mitigating the impact of 21st Century climate change on the amount and spatial pattern of blanket peat erosion. The results of our study can be used within blanket peatland regions to inform spatially-targeted management strategies.

PESERA‐PEAT: a fluvial erosion model for blanket peatlands

AbstractIn peatlands, fluvial erosion can lead to a dramatic decline in hydrological function, major changes in the net carbon balance and loss of biodiversity. Climate and land management change are thought to be important influences on rates of peat erosion. However, sediment production in peatlands is different to that of other soils and no models of erosion specifically for peatlands currently exist. Hence, forecasting the influence of future climate or spatially‐distributed management interventions on peat erosion is difficult. The PESERA‐GRID model was substantially modified in this study to include dominant blanket peat erosion processes. In the resulting fluvial erosion model, PESERA‐PEAT, freeze–thaw and desiccation processes were accounted for by a novel sediment supply index as key features of erosion. Land management practices were parameterized for their influence on vegetation cover, biomass and soil moisture condition. PESERA‐PEAT was numerically evaluated using available field data from four blanket peat‐covered catchments with different erosion conditions and management intensity. PESERA‐PEAT was found to be robust in modelling fluvial erosion in blanket peat. A sensitivity analysis of PESERA‐PEAT showed that modelled sediment yield was more sensitive to vegetation cover than other tested factors such as precipitation, temperature, drainage density and ditch/gully depth. Two versions of PESERA‐PEAT, equilibrium and time‐series, produced similar results under the same environmental conditions, facilitating the use of the model at different scales. The equilibrium model is suitable for assessing the high‐resolution spatial variability of average monthly peat erosion over the study period across large areas (national or global assessments), while the time‐series model is appropriate for investigating continuous monthly peat erosion throughout study periods across smaller areas or large regions using a coarser‐spatial resolution. PESERA‐PEAT will therefore support future investigations into the impact of climate change and management options on blanket peat erosion at various spatial and temporal scales. Copyright © 2016 John Wiley & Sons, Ltd.

Prediction of blanket peat erosion across Great Britain under environmental change

A recently developed fluvial erosion model for blanket peatlands, PESERA-PEAT, was applied at ten sites across Great Britain to predict the response of blanket peat erosion to environmental change. Climate change to 2099 was derived from seven UKCP09 future projections and the UK Met Office’s historical dataset. Land management scenarios were established based on outputs from earlier published investigations. Modelling results suggested that as climate changes, the response of blanket peat erosion will be spatially very variable across Great Britain. Both relative changes and absolute values of sediment yield were predicted to be higher in southern and eastern areas than in western and northern parts of Great Britain, peaking in the North York Moors of eastern England. Areas with high precipitation and low temperature were predicted to have low relative erosion changes and absolute sediment yield. The model suggested that summer desiccation may become more important for blanket peat erosion under future climate change, and that temperature was more dominant than precipitation in controlling long-term blanket peat erosion change. However, in the North York Moors, precipitation appeared to be more dominant in driving long-term erosion change. Land management measures were shown to provide a means to mitigate against the impacts of climate change on blanket peat erosion.

Wind erosion of blanket peat during a short period of surface desiccation (North Pennines, Northern England)

AbstractStrong winds are a characteristic feature of UK upland areas. Despite this, understanding of aeolian processes in upland environments of the UK is limited. This paper presents direct measurements and observations of blanket peat erosion by wind action during a two week period of desiccation in the North Pennines, Northern England. A circular configuration of mass flux sediment samplers was used to collect peat eroded by wind action from 16 cardinal compass directions. Meteorological conditions (wind speed, wind direction, precipitation and temperature) were recorded by an automatic weather station set up adjacent to the site. Surface desiccation led to peat crust erosion and dust deflation. During short (≤1 hour) periods of precipitation, wind‐driven rainfall also caused erosion. Typically, dust flux rates were up to two orders of magnitude lower than recorded during periods of sustained wet weather. Measurements demonstrate the hitherto unreported rapid switch in process regime between wind‐driven rainfall and dry blow deflation in blanket peat environments. Dry blow processes of blanket peat erosion may become more important in UK upland areas if climate change promotes more frequent surface desiccation. Copyright © 2006 John Wiley & Sons, Ltd.

Blanket peat erosion and sediment yield in an upland reservoir catchment in the southern Pennines, UK

AbstractThis paper investigates temporal variations in fluxes of peat and other sediment in the catchment of March Haigh Reservoir, West Yorkshire. Long‐term estimates of sediment yield were derived from a study of reservoir sediments. Magnetic properties were used to correlate ten cores to a master profile dated using 210Pb and 137Cs. A 14C date suggests that most of the organic component of the sediment is allochthonous and derived from peat eroded from the catchment. Organic sediment yields suggest low catchment erosion rates between 1838 and 1963. Blanket peat erosion increased significantly after 1963, and peaked between 1976 and 1984. Estimates of total sediment yield range between 2 and 28 t km−2 a−1. These yields are significantly lower than those from some previous studies examining reservoir sedimentation in other blanket peat‐covered catchments. The low yield estimates may be due to relatively low rates of erosion in the basin, but may also be partly explained by maintenance of silt traps during the early life of the reservoir and removal of sediment by scouring. Sedimentation within the reservoir is spatially variable, and bathymetry and sediment source appear to be the dominant controls on sedimentation patterns within the reservoir. Copyright © 2005 John Wiley & Sons, Ltd.

Fluorescence microscopy of pollen and spores: a tool for investigating environmental change

Fluorescence microscopy of fossil pollen and spores has only been exploited by palynologists for geological time scales. A reconstruction of ecological change, blanket peat erosion and consequent sediment flux within an area of moorland in the north of England during the late Holocene has provided an opportunity to evaluate whether fluorescence microscopy of pollen and spores can be used as a tool for reconstructing environmental change at shorter and more recent timescales. The fluorescence properties of pollen and spores in samples of blanket peat (sediment source) and reservoir sediments (sediment sink) were assessed during routine pollen counts. Fluorescence varied with taxon. Bog surface processes such as moorland fire and dessication were observed to have no visible effect on fluorescence, but air pollution deposition (indicated by Pb) did have an effect, although exactly which pollutant(s) is responsible is unclear. The effect on fluorescence of the physical processes associated with peat erosion and re-sedimentation in reservoirs was examined. Spores of lower plants found in reservoir sediment samples with a high content of eroded peat were well preserved (fluorescing at blue-green wavelengths), suggesting that the eroded peat was transported from the bog surface to the reservoir as peat fragments containing pollen and spores. There is a direct correlation between the proportions of pollen and spores with extinguished fluorescence (very poor preservation state) in sediment samples, and sediment accumulation rate. This relationship is probably not applicable for quantitatively estimating sedimentation rate at other sites due to the effect of local factors. However, the relationship can provide the basis for a simple, quick and relatively inexpensive method of examining qualitative shifts in sediment flux, which can be conducted during routine pollen counts.

Blanket peat erosion in a Mid-Wales catchment during two drought years : Francis, I S Earth Surf Process LandV15, N5, Aug 1990, P445–456

Blanket peat erosion in a Mid-Wales catchment during two drought years : Francis, I S Earth Surf Process LandV15, N5, Aug 1990, P445–456

Blanket peat erosion in a mid‐wales catchment during two drought years

AbstractThe rate of blanket peat erosion was measured at an upland site in central Wales during the 1983‐1984 drought years. Erosion pins, a peat surface sediment trap, and sediment sampling in the effluent stream, were used to estimate the rate of peat surface recession and the rate of organic sediment loss from the catchment. An overall rate of surface recession of 16 mm y−1 on exposed peat faces was recorded; this differed between faces of different aspects, with the greatest recession on southwest faces. Eroding peat surfaces exhibited maximum recession during the summer, but the peat surface sediment trap indicated that the highest rates of sediment loss from peat faces due to rain wash occurred during the autumn and early winter. Stream sediment sampling showed that the yield of organic sediment from the catchment was 34·4 t km−2 yr−1, with greatest losses also during the autumn and early winter. The evidence suggested that the surface recession, as measured on erosion pins, included a ‘wastage’ or shrinkage component, which possibly accounted for as much as 80 per cent of the apparent loss. Direct and circumstantial evidence suggested that peat wastage during the summer months was the most important agent of surface recession in the study period, which encompassed the two dry summers. Desiccation provided available sediment during the autumn, but organic sediment supply became limited as the winter progressed, despite the occurrence of frost heave.

The cause of peat erosion: a palaeolimnological approach

SUMMARYPalaeoecological analyses of two lake sediment cores from the Round Loch of Glenhead, Galloway, S.W. Scotland and Loch Laidon, Ratinoch Moor, Central Scotland have been conducted to elucidate the cause of the observed blanket peat erosion in their catchments. Both simple physical measurements such as percentage loss on ignition and the pollen and diatom record reveal clearly the onset of peat erosion in these catchments. Accurate dating of erosion is still problematical. Nevertheless, some of the competing hypotheses that have been advanced to explain blanket peat erosion are evaluated. Acid deposition cannot be responsible for the peat erosion in these two catchments since the combined use of 211Pb and 14C dating suggests that erosion was initiated between c. AD 1500 and AD 1700, an age well before the effects of atmospheric deposition are documented by the core. However, it remains to he resolved what the effects have been of land‐management changes such as grazing, burning and climatic effects, such as the Little Ice Age.

The extent and time-course of mountain blanket peat erosion in Ireland.

Erosion of upland blanket pent is widespread in Britain and Ireland and suggestions for its initial causes have included recent human disturbance and changes in the mechanical stability of the peat masses through time. A survey of blanket peat in five mountain areas in Ireland revealed extensive erosion in all areas, and two cores of mountain lake sediment contained inwashed peat in their upper sections. Detailed analysis of the core from the Wicklow Mountains revealed pollen evidence for initial peatland development, tree clearance and eventual peat erosion. The inwashed peat contained abundant Sphagnum leaves. Peat inwash began 1500 years ago in Donegal, N.W. Ireland and 3000 years ago in Wicklow near the east coast. The occurrence of erosion over these time periods does not suggest that recent human activity and changes in land-use are the original causes of erosion. Recent human activity has merely intensified erosion that probably originated from peat flows or the development of natural drains in mature peat masses developing on sloping ground.

RECENT ACCUMULATION AND EROSION OF BLANKET PEAT IN THE WICKLOW MOUNTAINS, IRELAND.

Active peat erosion is widespread in the Wicklow mountains, and it has been suggested that peat accumulation has slowed or ceased in the area associated with the erosive processes. Analysis of the recent deposition of pollen and magnetic minerals at three sites shows that significant quantities of peat (6.5 to 16.5 cm) have accumulated within the last 150 years. The fallout of magnetic pollutants is far below that found in the Pennine peats, ruling out certain hypotheses about the causes of montane blanket peat erosion.

Blanket peat erosion: Theoretical considerations and observations from selected conservation sites in slieveanorra forest national nature reserve, county Antrim

Geomorphological investigation of blanket peat at three conservation plots in Slieveanorra Forest National Nature Reserve, County Antrim, suggests that various stages of peat erosion are concurrent. The proximity of undisturbed peat, gullies and haggs, peat flats, redistributed peat and regenerated peat is described. Morphological evidence may be interpreted in terms of a natural cycle or system of peat erosion but pollen analysis suggests a linkage between agricultural activity and the commencement of erosion. A C14 date of 2108 BP implies a much earlier date for peat erosion than generally considered. Erosion processes and origins are discussed and related to theories of upland blanket peat erosion.