MIRES ON THE MOORS Science and Evidence Report 2020 - University of Exeter
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MIRES ON THE MOORS Science and Evidence Report 2020
University of Exeter Acknowledgements
Mires On The Moors Project
Prof Karen Anderson This project received its core funding from
Josie Ashe South West Water, without which none of Science and Evidence Report 2020
Dr Pia Benaud the science described here would have been
Prof Richard E Brazier delivered. We are also incredibly grateful for
Dr Donna Carless the funding and support we have received
Dr Guy Freeman from our external project partners including
Prof Angela Gallego-Sala the Environment Agency, Natural England, South West Water’s Upstream Thinking Programme, working with a multitude of
Dr Naomi Gatis Historic England, Dartmoor National Park and stakeholders, has restored a total of 24.8 km2 (2480 ha) of peatland across Exmoor
Dr Emilie Grand-Clement Exmoor National Park. and Dartmoor since 2010 as it became apparent that much of the peatlands
Anne Hand Additionally, we would like to thank numerous we rely on for vital ecosystem services were in a degraded and worsening state.
Prof Iain P Hartley farmers, Commoners and landowners on Research has been central to the restoration programme; to better understand the
Dr David J Luscombe Dartmoor and Exmoor for granting access for current state of these peatlands, design appropriate restoration plans and evaluate
Dr Edward Malone restoration and monitoring work. the success of restoration, our findings are outlined within this report.
South West Water Thanks are also due to the previous members
Morag Angus of the University of Exeter research team,
This document should be cited as Brazier, R.E., Angus, M., Benaud, P., Gatis, N., Luscombe,
Conrad Barrowclough the South West Peatland Partnership, and the
D.J., Anderson, K., Ashe, J., Barrowclough, C., Carless, D., Freeman, G., Gillard, M., Grand-
Dr David Smith numerous volunteers that have been involved Clement, E., Hand, A., Malone, E., McAleer, A. and Smith, D. (2020) Mires on the Moors:
with the delivery of the project. Science and Evidence Report 2020, University of Exeter, Exeter, UK.
Exmoor National Park Authority
Dr Martin Gillard
University of Bristol
Prof Edward Hornibrook
Dr Adam McAleer
2 Mires On The Moors Science and Evidence Report 3
Foreword and Introduction to this Report
T
he degraded state of UK peatlands has been recognised as a critical problem that should be tackled with
some urgency if the UK is to meet its targets of carbon storage and Greenhouse Gas Removal. The South
West peatlands of Dartmoor, Exmoor and Bodmin Moor are potentially huge carbon stores, with equal
potential to store water at times of heavy rainfall and release cleaner water during times of drought. However, over
a decade ago, pilot work funded by South West Water identified that these peatlands were heavily modified – due
to drainage for agricultural purposes, removal of peat for fuel, historical overgrazing and practices such as burning EXECUTIVE
SUMMARY
or moorland swaling to regenerate vegetation for grazing. Consequently, research began in 2010 to understand
the way in which the South West peatlands are structured, how they function and furthermore how they
might respond to restoration practices which could restore some of the ‘natural’ functioning of these degraded
ecosystems. In addition, given their southerly location, it was hypothesised that these peatlands may be the first in
the UK to respond to changes in climate and thus could be ‘canaries in the coalmine’ to educate us about how the § Up to January 2020, 27.8 km2 (2780 ha) of peatland have been restored following
more extensive, northerly peatlands might respond in decades to come. methods specifically developed for Exmoor and Dartmoor. Page 12.
The following report describes the outcomes of the last 5 years of research into peatland restoration. The report § In shallow peats, water table responses to restoration are complex. In the driest areas,
where drainage had the greatest effect pre-restoration, water tables rose by as much as
is supplemented by a number of peer-reviewed scientific papers which are appendicised and will be updated as 4 cm. Overall, however, water tables remain statistically similar post-restoration. Page 16.
more of the research is published in years to come. These reports and papers can be found here:
§ In deeper peats, restoration increased the permanent deep water storage in the soil by
www.exeter.ac.uk/creww/research/casestudies/miresproject 7.3 cm and increased average water tables by 2.45 cm. Page 20.
Ongoing work over the next 5 § Restoration can significantly alter rainfall runoff regimes in restored catchments; within
years will continue to monitor the deeper peat, gully flow was reduced by around 66 %. In shallow peatlands the flow
structure and function of South response was more complex with storm generated discharge reduced by up to 32 %
West peatlands, building on the in some catchments. Pages 16 and 20.
short-term, post-restoration story § In shallow peats, restoration has not significantly changed water quality, suggesting that
told here, to develop understanding there has not been a significant change in the ecohydrological function of the peatland
to-date. Page 24.
of how peatlands can provide a
wide range of ecosystem services § Post-restoration, the total load of dissolved organic carbon leaving the study site on
to society, if they are managed in Dartmoor during storm events was approximately 1/3 of the pre-restoration loads due
to a significant decrease in runoff. Page 28.
an environmentally progressive
manner, which considers all users § Population densities of the sheep tick, a vector of economically important livestock
diseases, are significantly lower in mires than in drier habitats on the same sites.
and beneficiaries of these common Page 32.
resources.
§ Bog asphodel (Narthecium ossifragum), a potentially toxic plant, contributes up to 20 %
forage value in a transitional bog community and continues to survive but has not
Richard Brazier spread significantly post-restoration. Page 34.
Professor of Earth Surface § In shallow peats, restoration did not significantly alter (heterotrophic) respiration of
Processes and Director of the peat soil or increase methane fluxes (even after 7 years), illustrating how degraded
the Centre for Resilience in these peatlands were and how much intervention is required to restore ecosystem
Environment,Water and Waste. functionality. Page 35 and 36.
§ In deeper peats, raised water tables significantly reduced (heterotrophic) respiration of
the peat store and initially increased methane emissions; both processes are indicative
of a return to more natural functioning in the longer term. Page 40.
§ Dartmoor National Park is estimated to have 158 ±101 km2 (15800 ha) of peat
>0.4 m deep storing 13.1 megatonnes of carbon. Page 42.
§ Functionally intact blanket bog covers just 3.6 km2 (360 ha) of Dartmoor, however it is
fragmented and often surrounded by ecohydrologically degraded peat which covers an
area of 29 km2 (2900 ha). Page 42.
4 Mires On The Moors Science and Evidence Report 5
BACKGROUND
AND CONTEXT
Typical peatland Adder (Vipera berus)
vegetation in the sunning itself on Exmoor.
South West of
England underlain
by a carpet of
Sphagnum mosses.
Rivers sourced on peatlands provide 70 % of all UK drinking water.
globally, they include drainage, peat Exmoor in 2006 as it became for the Environment, Food and
extraction, over-grazing, burning, apparent that many of the peatlands Rural Affairs recognises the need to
disturbance from military use, climate we rely on for vital ecosystem restore and protect our peatlands4,
change and nutrient deposition. services were in a degraded and funding the South West Peatland
These pressures have altered the worsening state. South West Water’s Partnership project to restore
P
natural feedback cycles which Upstream Thinking Programme, 16.8 km2 (1680 ha) of peatland
eatlands are now recognised of carbon which, maintain these ecosystems, leaving working with a multitude of across Bodmin Moor, Exmoor and
nationally and internationally as if not safeguarded, them increasingly vulnerable to stakeholders, has restored a total Dartmoor by 2020.
providing many essential and could be released erosion and ecological/hydrological of 24.8 km2 (2480 ha) of peatland
valuable ecosystem services; they into the atmosphere Research has been central to the
degradation. across Exmoor and Dartmoor
play an important role in water worsening the restoration programme; to better
since 2010. As part of their 25-year
management, act as carbon stores, climate emergency Peatland restoration started on understand the current state of
environment plan the Department
preserve archaeology, and are rare or washed into these peatlands, design appropriate
and important habitats with unique rivers which rise restoration plans and evaluate the
flora and fauna1. In 2011, the IUCN upon the moors success of restoration. The following
identified these landscapes as the reducing water Restoration at document outlines our findings since
single most important terrestrial quality downstream. Hangingstone
2010 working within Dartmoor and
Hill, Dartmoor has
carbon store in the UK and that The water leaving left pools of water Exmoor National Parks.
around 70 % of all UK drinking the uplands not where there were
water comes from upland, peatland only supports erosional pans.
catchments2. aquatic ecosystems
downstream but is
Peatlands form where waterlogged the main drinking
conditions limit decomposition to water source for
such an extent that dead vegetation many people living
accumulates as peat soil. The uplands in the South West.
of the South West have a specific Furthermore, Ecosystem services provided by a functioning peatland.
type of peatland called blanket bog functioning peatlands REFERENCES
which develop in cool and wet regulate water
conditions, forming predominately supply, slowing the The appendices are available to view
at www.exeter.ac.uk/creww/research/
from Sphagnum mosses. Although flow of water from casestudies/miresproject
blanket bog is extensive across the uplands during
the moors of the South West, it is rainfall and gradually 1. Grand-Clement, E. et al. Evaluating
ecosystem goods and services
globally rare, consequently these releasing water Pools of water after restoration of marginal upland
areas are internationally important during dry spells. form behind peat peatlands in South-West England. J. Appl.
ecosystems, with many designated dams, Lanacombe, Ecol. 50, (2013).
The peatlands of
as Sites of Special Scientific Exmoor 2014.
the South West of 2. Bain, C. G., Bonn, A. & Chapman, R.
Interest and/or Special Areas of
England lie at the Erosion at Hangingstone Hill, Dartmoor. IUCN UK Commission of inquiry on
Conservation. Peatlands. IUCN UK Peatland Programme
most southerly and (2011). doi:ISBN 978-0-9570572-1-0
Peat accumulates slowly, mm’s-cm’s westerly limit of the
per year over thousands of years. bio-climatic envelope indicators of what may happen to 3. Gallego-Sala, A. V. et al. Bioclimatic
envelope model of climate change
These gradually accumulated deposits of peat-forming ecosystems3 (i.e. other more northerly peatlands, in impacts on blanket peatland
hold a precious record of past climate, areas with suitable temperature the UK and elsewhere, as the climate distribution in Great Britain. Clim. Res.
land use and ecology as well as and precipitation conditions). warms and rainfall patterns change. 45, 151–162 (2010).
preserving rare organic archaeological Consequently, these bogs are Natural and anthropogenic pressures 4. Department for Environment Food
remains such as the Whitehorse Hill vulnerable ecosystems that must be on the peatlands of the South and Rural Affairs. A Green Future:
cist.They also store huge amounts protected. They are also invaluable West are typical of those occurring
Our 25 Year Plan to Improve the
Environment. (2018).
6 Mires On The Moors Science and Evidence Report 7
EXMOOR SHALLOW PEAT LOCATION INFORMATION
Exmoor: a Shallow Peatland
S
ince the last ice-age, humans
have been using and altering
the moorlands of Exmoor. Peat
cutting by hand has been practised
on Exmoor since medieval times, and
features indicate that large amounts
of peat have been removed for
domestic use1. From the 1820s the
Knight family constructed a dense
network (approximately every 20 m)
of hand dug ditches (about 0.5 m
wide by 0.5 m deep) (Figure 1) to
reclaim the high moors for arable
production2 resulting in 618 km
of drainage ditches3 (Figure 2).
Additional larger ditches (>1.5 m Figure 2 Exmoor National Park showing the fragmented
wide) were machine dug between moorland areas (yellow) and mapped drainage features (blue).
the 1960s and 1980s to drain
specific areas such as springs4. The
moorlands have also been subject
to burning, in a further attempt Peat cutting on Brendon Common in the 1990s.
to improve pasture for grazing. Image courtesy of Rob Wilson-North.
Collectively, these management
practices led to a drying out of the
peatlands and an increase in the Figure 3 Summer in the
dominance of purple moor grass Aclands catchment with a REFERENCES
Figure 5 Post-restoration,
(Molinia caerulea). greenhouse gas monitoring
peat dams create pools of The appendices are available to view
(GHG) location in the at www.exeter.ac.uk/creww/research/
water at Spooners.
foreground and water level casestudies/miresproject
and water quality monitoring
across small (left), large 1. Riley, H. Turf cutting on Exmoor: an
(middle) and medium (right) archaeological and historical study. Exmoor
ditches in the background. Mires Project. (2014).
2. Hegarty, C. & Toms, K. Exmoor National
Park national mapping programme
managment and summary report.
(Exmoor National Park Authority, 2009).
3. Anderson, K. & Cowley, A. Initial project
The cool (minimum of 2 °C in of mire and wet heath communities, report : Exmoor Mires-on- the-Moors
February, rising to 18 °C in July5) and such as Sphagnum spp. and cotton Figure 4 Unmanned Aerial Project for LiDAR Analysis. (2011).
Vehicle borne imagery of
wet (1353 mm per year) conditions grasses (Eriophorum spp.) but are the dry purple moor grass
4. Mills, J. et al. Review of the Exmoor Mires
on the uplands of Exmoor enable dominated by purple moor grass Restoration Project. (Countryside and
(Molinia caerulea) dominated
peat to form. However, peat across (Molinia caerulea). The catchments Community Research Institute, 2010).
Spooners catchment, post-
Exmoor is relatively thin, with 53 km2 are currently in use as rough grazing. restoration. 5. Met Office (2019): Met Office
(5300 ha) of the 65 km2 (6500 ha) of MIDAS Open: UK Land Surface
Aclands and Spooners were Stations Data (1853-current).
blanket bog less than 30 cm thick6,7.
restored, by ditch blocking with peat Centre for Environmental Data
Monitoring the effects of restoration and wooden dams, in spring 2013 Analysis, 10/12/2019. Available
has focused on two small headwater and 2014 respectively (Figure 5). at: http://catalogue.ceda.ac.uk/
uuid/dbd451271eb04662
catchments of the River Barle,
Additional monitoring occurred at beade68da43546e1. (Accessed: 10th
within North Exmoor Site of Special December 2019)
Long Holcombe along a gradient
Figure 1 Photograph Scientific Interest. They are located
between wet bog vegetation 6. Merryfield, D. L. Palynological and
from an Unmanned
between 380 and 465 m above sea Stratigraphical studies on Exmoor. Kings
Aerial Vehicle showing (Sphagnum spp. and cotton grasses
level. These catchments, Aclands College Unpublished, (Kings College,
the closely spaced hand- (Eriophorum spp.)) with peat depths
(Figure 3) and Spooners (Figure 4), 1977).
dug drainage features
in excess of 0.5 m, to dry purple
typical of Exmoor and were chosen to be representative 7. Bowes, A. C. Exmoor Blanket bog
moor grass (Molinia caerulea)
water quality and water of the general peatland conditions Inventory and restoration plan for
dominated grassland with peat
table depth monitoring
found across Exmoor. Both English Nature. University of Calgary MSc,
locations at Aclands. depths of less than 0.2 m. (University of Calgary, 2006).
catchments contain vegetation typical
8 Mires On The Moors Science and Evidence Report 9
DARTMOOR DEEP PEAT LOCATION INFORMATION
Figure 6 Extent
of peatland Dartmoor: a Deep Peatland
T
degradation
across he uplands of Dartmoor have A pilot study into the effectiveness thick3, which is above the average
Dartmoor.
also been shaped by human of restoration was established in for Dartmoor (0.81 m)4. Where
hand since the last ice-age. The 2013 in an area of degraded blanket vegetated, Flat Tor Pan has vegetation
uses have been varied and included bog on the north moor: Flat Tor Pan. typical of blanket mire (including
domestic and commercial peat The site was chosen as typical of Sphagnum spp. hare’s-tail cotton grass
cutting, tin and china clay extraction, the extensive areas of blanket bog (Eriophorum vaginatum), purple moor
granite quarrying, drainage for with a pattern of erosional peat pans grass (Molinia caerulea) and deer
agricultural improvement, grazing (generally
BODMIN MOOR, EXMOOR RESTORATION
AND DARTMOOR Reprofiling steep erosional
slopes at Flat Tor Pan,
Dartmoor, December 2019.
Restoration planning, of the slope, the volume of water
that flows down the ditch and the
P
methods and outcomes landscape impact2. Blocks installed
eatland restoration represents an in the ditches can comprise a
opportunity to make a significant combination of peat, wood, stone,
difference to the degrading bales (made out of purple moor Restoration in progress within
peatlands of the South West of grass (Molinia caerulea)) or grey the Spooners monitoring
England.The South West Peatland willow (Sambucus nigra). The wood catchment, Spooners, Exmoor.
Partnership is the umbrella name for the blocks comes from local
that brings together the local delivery plantations, which is then planked to
of peatland restoration across the our requirements and left untreated.
three moors of Bodmin Moor, Peat blocks along a drainage ditch showing water
Dartmoor and Exmoor. Its aim is to Before any restoration takes place, stored behind the blocks, Great Buscombe, Exmoor.
work together with a wide range of the mires staff carry out a variety
partners (see back cover) to restore of in-depth planning, assessment,
these peatlands and bring about research and consultation in order
sustainable hydrological management to compile a Restoration Plan for
in upland river catchments.The each site representing a best practice Willow faggot dam in a steep gully,
Hoar Moor, Exmoor, February 2019.
Exmoor Mires Partnership is the approach to peatland restoration. Willow was used in this situation to
culmination of several projects that Each plan assesses the positive and slow flows, trap sediments and create
have run from 1998-to date, whilst negative impacts of the restoration small areas of wet willow woodland. It
the Dartmoor Mires Partnership has on the ecology, historic environment, was part of wider works to reinstate
had two phases of restoration; a pilot landscape, access arrangements, the River Quarme back into its original
course, having been diverted in the
project (2010-2015) and the current land management practices, and early twentieth century.
phase (2018-2021).The Bodmin estimates the costs associated of
Moor Peatland Partnership has been carrying out the restoration works. damaged peatland has had initial restoration and monitoring works, in the hydrology and ecological
running since 2018. All appropriate government bodies, ditch blocking works carried out – a and indirectly through the effects functioning of the peatland.
landowners, commoners, graziers, total of 25,607 blocks installed in of restoration e.g. payments for
Vegetation monitoring on Exmoor
Restoration work tenants and farmers have input 250 km of drainage ditches. A further ecosystem services provided by
(28 sites) shows an expansion in
The overall aim of restoration is to into the plans and therefore the 7.5 km2 (760 ha) is considered the peatland generating income to
the distribution of Sphagnum 3
raise water tables, decrease peak restoration that happens on the unsuitable for restoration. On farmers via Higher Level Stewardship
years post-restoration. This increase
flows from storms and increase base ground. Dartmoor 1.8 km2 (180 ha) of schemes for moorland maintenance,
is significant (p
RESTORATION
Vegetation monitoring
along a transect,
Squallacombe, Exmoor. A Mesolithic (7000 to Pre-restoration 2006. Post-restoration 2006. Post-restoration 2019.
4000 BCE) hammer
stone found at Horsen
Farm, Exmoor during
mire restoration
field work.
Figure 10 Fixed point photography from Roostichen, Exmoor; pre-restoration (2006), immediately post-restoration (2006) and 13 years post-restoration (2019).
Type Exmoor Dartmoor
Site surveys (combined walkover and desk-based assessment) 18 7 peat. One such study identified at up to centimetre accuracy. These Volunteers are actively involved in
Palaeoenvironmental Assessments 8 3 tephra – volcanic dust deposits that surveys clarify features such as a wide range of activities within the
Watching Briefs 2 5 can precisely date peat deposits individual peat cuttings (Figure 11) project including running, leading
and the evidence of environmental which are often hard to distinguish and organising educational walks,
Landscape Studies 2
change held within them – for the by human eye on the ground. talks and events; practical work
Geophysical Surveys 7 first time in the South West9. such as small-scale ditch blocking;
Measured, earthwork Surveys 9 Communication and survey and research; publicity work
Excavations 7 Landscape Education and office work. Over 1000 days of
5 2 Peatland restoration aims to bring volunteering have been carried out
Research Reports Communicating all the work and
about landscape change. In order to on the project.
Additional HER entry reports 10 6 research undertaken is a vital
demonstrate and monitor landscape element of the partnership, as is
Number and type of historic environment assessments carried out as part of peatland restoration
change associated with restoration learning from those who manage
been observed at two restoration and mitigate fixed point photography is used and work on the peatlands. Involving
sites which previously had none5,6. the impact (Figure 10). There are now over 60 local individuals, community groups, REFERENCES
In the context of there being only of mire
Figure 11 Peat cuttings on pre- and post-restoration locations the farmers who manage the
Exmoor recorded using
eight breeding snipe locations on restoration on processed airborne LiDAR.
across Exmoor and Dartmoor. land and partner organisations The appendices are available to view
at www.exeter.ac.uk/creww/research/
Exmoor in 2011, this is a notable the historic Comparing aerial imagery dating has enabled successful landscape casestudies/miresproject
result. Whilst on Dartmoor, snipe environment from the 1940s to present day peatland conservation to happen
1. Thom, T. et al. Conserving Bogs the
(Gallinago gallinago) have increased we combine images enables us to map and on the ground. A programme of Managment Handbook. (Stationery
considerably and dunlin (Calidris information analyse how that landscape was, is, education, events and publications Office, UK, for Scottish Natural Heritage,
alpine) increased, particularly in the from walkover and has changed through time. At have been delivered in order that 1997).
areas that have been restored e.g. surveys and the same time, this captures modern the numerous people who work in 2. Grand-Clement, E. et al. New
Winney’s Down and Cowsic Head7. desk-based day archaeology in the form of our and visit these landscapes can gain a approaches to the restoration of
assessments restoration work. Airborne LiDAR greater understanding and experience shallow marginal peatlands. J. Environ.
The Exehead/ Blackpitts (Exmoor) Mange. 161, 417-430 (2015).
restored sites have become the best of existing (Light Detection and Ranging) and of peatlands. For example, the
sites in Somerset for black darter knowledge Unmanned Aerial Vehicle (UAV) ‘Bogtastic’ CLOWNS Play Bus and 3. Hand, A. Analysis of Botanical Survey Data
into site plans. photogrammetric surveys record the ‘Bogtastic’ Summer Festival, has 2018 Exmoor Mires Partnership. (2019).
(Sympetrum danae) and common
hawker (Aeshna juncea) dragonflies, Where thought our landscapes in another dimension engaged with over 4000 people. 4. Lunt, P. Dartmoor Mires Project Vegetation
necessary, Survey Data Analysis 2018. (2018).
both upland species which require trackways and Second World War
open water. This success is due to additional work is carried out to 5. Boyce, D. C. A survey of waders and other
military training features. This data
the pools created by the restoration ensure the historic environment Enjoying the ‘Bogstacle Course’ at Bogtastic. birds on mires in Exmoor National Park,
has allowed the existing Historic 2011-12. RSPB South-west Region Report
in 2007 – prior to this there was no is both well-recorded and
Environment Records (HER) to be to South West Water. (2012).
surface water on the site8. understood. Such work includes
expanded and enhanced. 6. Ballance, D. K. Exmoor bird monitoring
palaeoenvironmental studies,
Historic Environment project. (2016).
geophysical and earthwork surveys, In some cases, we have carried
Exmoor and Dartmoor contain excavations and watching briefs. out additional case studies that go 7. Townend C., R., E. & Booker H. Dartmoor
a wide range of historic sites Many previously unrecorded beyond individual sites and represent Mires Project breeding bird survey 2018:
Distribution and Population Breeding of
and features that often survive archaeological features and sites have new research into aspects of the Dunlin and other bird species on Dartmoor
well thanks to the less intensive consequently been identified as a historic environment that may be Blanket Bog. (2018).
agriculture and development consequence of peatland restoration impacted by mire restoration. This 8. Boyce, D.C. Inveterate Survey and
compared to lowland areas. The peat (over 300 on Exmoor), ranging in includes investigations into domestic Monitoring on Exmoor Mire Project
itself often covers archaeological date from around 6000BC to the and industrial peat cutting on both Restoration Sites, 2009-2014. (2015).
sites and deposits, preserving 20th century. The new evidence has moors, the form and dating of 9. Bray, L. S. The Past and The Peat:
organic materials and environmental included prehistoric standing stones deserted field systems on Codsend Archaeology and peatland restoration
evidence that does not survive in and cairns, nineteenth-century Moor (Exmoor) and the soils of on Exmoor. (Exmoor National Park
drier conditions. To further inform mining works, networks of medieval Exmoor before the formation of Authority, 2015).
14 Mires On The Moors Science and Evidence Report 15
EXMOOR SHALLOW PEAT HYDROLOGY
How does the restoration of a shallow peatland affect water
tables, runoff and water storage?
I
n an intact state, peatland landscapes Figure 12 Illustration
§ Restoration can significantly alter rainfall runoff regimes in restored form as wetlands with water at or of a dipwell array
Radio connection for
catchments. near the ground surface for most remote data retrieval
surrounding a restored
Dip well measuring drainage ditch in
§ Peak runoff from comparable rainfall events can be reduced by as much of the year. These areas are home to water table depth Spooners catchment.
as 21 %. specialist plant species adapted to below surface
grow in waterlogged ecosystems. The Ditch in cross-section
§ Total runoff generated from comparable rainfall events can be reduced storage and release of water from
by as much as 32 %, as water leaves the restored catchment more slowly, such landscapes is inherently linked to
increasing catchment baseflow between rainfall events. the way the ecosystem functions as a
§ Rainfall runoff response is catchment specific, smaller rainfall events can store of carbon and regulator of river
result in a limited increase in storm runoff. flow. Peatland restoration aims to
re-establish more natural hydrological
§ In the short term (
EXMOOR: SHALLOW PEAT HYDROLOGY
2000 1,901 Monitoring equipment in pools formed
behind blocks following restoration.
1800
1600
1,367 1,383
Anual Rainfall (mm)
1400 1,289
1200 1,050 1,098 1,108
958 958
1000
800
600
400
200
0 Figure 15 Annual rainfall totals for
Spooners catchment from 2010
2010 2011 2012 2013 2014 2015 2016 2017 2018 to 2018; restoration occurred in
2013. The atypical pre-restoration
Year rainfall of 2012 is notable at nearly
double that of 2017.
restoration has provided significant
Restoration in progress at Spooners. short-term buffering of rainfall
runoff at Spooners, particularly for
small rainfall events that do not
overwhelm the temporary surface
storage created behind peat dams.
Aclands Catchment Runoff
The restoration response within
the smaller catchment (Aclands)
was less pronounced. For larger
rainfall events (>10 mm), total event
quickflow and peak event discharge
were not significantly different 100,000
(p>0.05). Contrastingly, for smaller Pre- 32% Reduction
rainfall events (100 % at pDARTMOOR DEEP PEAT HYDROLOGY
How does the restoration of a deep peatland affect storm runoff
and water storage?
P
eatlands form as wetland
§ Average (spatially and temporally) water table depths have increased landscapes with water at or near Pre-Restoration Post-Restoration
Distance from peat pan (m) Distance from peat pan (m)
post-restoration, they are now 2.45 cm nearer to the surface. the ground surface and plant
0 1 2 3 0 1 2 3
§ Pre-restoration, maximum water table drawdown (i.e. depth during dry species adapted to grow in such 30 30
weather) was between 22 and 48 cm below the surface. Post-restoration an environment. The way peatland Edge of
this reduced to between 17 and 37 cm, indicating an average additional landscapes store and release water peat pan
Vertical position (cm)
Vertical position (cm)
20 20
7.3 cm of permanent deep water storage in the peat soil. is inherently linked to the way they
function as stores of carbon and Maximum water level
§ Restoration removed permanently dry areas next to peat pans, which regulators of river flows. Peatland 10 10
above surface
now exhibit water levels >10 cm above the surface during periods of restoration aims to re-establish more
Permanently dry
edge zone
high rainfall. natural hydrological processes in 0 0
§ Diffuse overland flow and deep subsurface flow outside of the main gully, drained or damaged areas, leading
dominate total runoff post-restoration. Runoff through the monitored to more secure carbon storage (or -10 -10 2.45 cm increase in
gully reduced by approximately 66 % post-restoration. accumulation) and reduced variation average water table
in downstream river flows. The -20
§ The average in-gully pooled water storage increased by 32 cm post- monitoring design at Flat Tor Pan
-20
7.3 cm of extra,
restoration. Minimum pooled water within the gully also increased by measured spatial patterns of water permanent deep storage
around 4 cm post-restoration. table depth and runoff from a single -30 -30
Surface Profile Mean Water Table Depth Surface Profile Mean Water Table Depth
Minimum Water Table Depth Maximum Water Table Depth Minimum Water Table Depth Maximum Water Table Depth
gully and its associated drainage Figure 19 Minimum, mean and maximum depth to water table (cm), pre- and post-restoration, relative
area. Water tables, measured as the to the average soil surface level for each of the distance classes measured. The black line ilistrates the
spatialy averaged soil surface height for each of the measured distance classes.
depth of water below the ground
surface, were monitored within
and surrounding dendritic drainage
features, using a network of dipwells Sphagnum growth over
extending 2 metres below the peat monitoring equipment.
surface
Water Storage
Pre-restoration, gully runoff was
characterised by flashy flows, an
ephemerally dry gully and dendritic
erosional “pan” features (Figure 18).
Average water table depths pre-
restoration were ca. 20 cm below
the surface in vegetated areas, but
fell to >40 cm below the soil surface
during dry periods. The pan features
rarely supported water tables
above the surface; only during the
wettest conditions (Figure 19). In
the vegetated areas closest to the
bare peat pans (0 to1 m from the
edge), water tables never rose to
within ca. 5 cm of the surface (Figure
19) which would be considered
normal in a healthy peat bog.
Consequently, the areas of vegetated
peat immediately surrounding the
bare peat pans were permanently
Figure 18 Photos and ilistration of how restoration has altered the hydrological
connectivity of the monitored dendritic landforms from pre-restoration (left) to dry, causing peat collapse and the
immediately post-restoration (right). expansion of the dendritic pan/gully
20 Mires On The Moors Science and Evidence Report 21DARTMOOR: DEEP PEAT HYDROLOGY DARTMOOR: DEEP PEAT HYDROLOGY
4500 Figure 21 Total daily
Pre-restoration rainfall vs total daily
discarge leaving the
4000
Post-restoration R² = 0.5355
monitored drainage/gully
area on Flat Tot Pan. Post-
3500 restoration, the reduction
in total daily runoff for
a similar given rainfall
Total Daily Discharge (m3)
3000 is aproximatly 66 %, as
illustrated by the arrow.
2500
66% Reduction
in runoff
2000
1500
1000
R² = 0.5354
500
0
0 20 40 60 80
Total Daily Rainfall (mm)
Runoff
Post-restoration, runoff production
through the gully was significantly
reduced by ca. 66 % (Figure 21)
and in channel storage (i.e. pooled
water within the gully) increased
by an average of 32 cm. However,
it is important to note that these
changes reflect both increased
temporary storage in the peat soil/
surface pools, and a switch to diffuse
surface flow dominating storm
Figure 20 Conceptual diagram of mechanisims driving dendritic landform expansion across Flat Tor Pan. runoff, post-restoration. This does
not mean that less water is leaving
areas (Figure 20). This suggests that dry pan areas exhibiting an average well above the surface during the moorland, just that it now leaves
areas of bare peat/vegetated haggs of 10.8 cm of additional standing periods of high rainfall (Figure 19), via multiple pathways and much
are active systems that may continue water depth. Similarly, mean water potentially reducing the oxidation more slowly. Diffuse surface flow
to expand without intervention via tables have risen by 2.45 cm and and expansion of these regions leaving the site outside of the gully is
peatland restoration. maximum water table drawdown and providing more suitable habitat not measured here, but this type of
has reduced, providing an average for Sphagnum colonisation. These flow is slower than channel flow and
Restoration has had a profound
of 7.3 cm of permanent, deep water changes represent a step change will, therefore, contribute to flood
effect across the monitored
storage in the peat soil. in the hydrological function of the risk reduction and reduced peatland
locations. Hydrological connectivity
monitored area post-restoration erosion.
has largely been removed by drain The areas of permanently dry soil
which, in the longer term, would be The appendices are available to
blocking, resulting in previously immediately adjacent to the peat
expected to benefit peat forming view at www.exeter.ac.uk/creww/
sparsely vegetated and ephemerally pans now exhibit water tables
plant species and ecology. research/casestudies/miresproject
22 Mires On The Moors Science and Evidence Report 23EXMOOR SHALLOW PEAT WATER QUALITY
Understanding water quality in runoff from degraded, shallow
peatlands on Exmoor and the short-term impacts of restoration
T
he quality of the water running for water treatment as removing
§ Pre-restoration, low water tables were linked to elevated dissolved off Exmoor’s peatlands impacts DOC from water is complicated,
organic carbon concentrations. on aquatic life and drinking costly and can result in carcinogenic
§ Restoration has not had a statistically significant impact on any of the water management downstream. by-products.
water quality parameters studied. Due to the carbon-rich nature Prior to this study little was known
of peaty soils, the degradation of about the processes controlling the
§ Average DOC concentrations during runoff events pre-restoration range peatland function has been linked to
from 4.8 to 14.3 mg L-1 and post-restoration (3.5 to 13 mg L-1). quality of water leaving Exmoor’s
elevated dissolved organic carbon peatlands and assumptions about the
§ Water discolouration has not changed significantly post-restoration, and (DOC) concentrations in the water effects of peatland restoration on
remains above EC standards (Abs400 of 1.5 Au m-1). leaving peatland catchments in water quality were largely based on
recent decades. DOC enrichment results from the deeper peatlands
§ Greater improvements to the ecohydrological function, particularly
in water leaving upland catchments of northern England. Rainfall event
vegetation change are needed before significant changes in water quality
represents an important pathway based monitoring of water quality
can be detected following restoration, such as the reduction in carbon
of carbon loss. DOC also discolours at Aclands and Spooners pre-
loads which is only just becoming evident in the Spooners catchment.
water and therefore has implications restoration demonstrated that
increased DOC concentrations
occurred following warmer periods
Water held back by a peat dam with deeper water tables, likely
post-restoration on one of the
monitored ditches at Spooners.
to be due to the aeration of the
peat and stimulation of microbial
decomposition2. This suggests
that encouraging water table
depths to levels more typical of
peatland environments (at or near
the surface) could reduce DOC
concentrations.
Pre-restoration, DOC concentrations
leaving the catchments (4.8 to
14.3 mg L-1) were lower than the
national average (31 mg L-1)1, but
were frequently in excess of the
target of 5 mg L-1(Figure 22A). Up
to 4.5 years post-restoration there
has not been a statistically significant
change in DOC concentrations
(3.5 to 13 mg L-1) leaving either
catchment (Figure 22A), though
mean concentrations have slightly
lowered at both locations.
The amount of carbon lost from the Figure 22 Observations at
the flumes during monitored
catchment (carbon load) is related rainfall events A) flow-
to DOC concentrations and the weighted mean dissolved
total amount of runoff generated organic carbon (DOC)
by rainfall events. Pre-restoration, concentrations B) total mass
carbon loads ranged between of DOC exported rainfall
event, and C) Normalised
3 and 264 kg in the monitored (Log10) relationship between
events, where average loads were DOC Load and rainfall to
30.6 and 76.4 kg at Aclands and account for differences
Spooners, respectively (Figure 22B). in rainfall pre and post-
The reduction in rainfall in the years restoration. ‘x’ marks the
average (mean) value, ‘o’
monitored post-restoration (as indicates observations that
described in the Exmoor hydrology are considered outliers.
24 Mires On The Moors Science and Evidence Report 25EXMOOR: SHALLOW PEAT WATER QUALITY EXMOOR: SHALLOW PEAT WATER QUALITY
Looking downstream Figure 24 Discharge monitoring at
from Aclands flume Spooners catchment.
towards the River Barle.
Figure 23 A) average
water discolouration
(Abs400), B) average
Colour per unit Carbon
relation (ColourAbs400/
CarbonDOC), and
C) Specific Ultra-
violet Absorbance
(SUVA – Abs254nm/
DOC), observed
during monitored
rainfall events at the
flumes pre- and post- changes observed at Aclands more
restoration. ‘x’ marks
robustly, which could be linked to the
the average (mean)
value, ‘o’ indicates disturbances caused by restoration
observations that are efforts, a change in the source of the
considered outliers. DOC, or alterations to flow routing
through the catchment.
If the vegetation communities change
in response to restoration works,
as is likely if higher and more stable
water tables can be achieved and/or
through Sphagnum re-introduction
programs, it is expected that the
amount and chemical characteristics
of the DOC will change; DOC
would be sourced from fresher
section, Figure 15) means that restoration period is needed to see characteristics of the DOC, which material, as seen on Dartmoor (see
a significant decrease in DOC if reductions in DOC concentrations can then be used to infer the type next section). Importantly, this should
loads at Aclands (p=0.04), and a can be achieved in these degraded of carbon being lost (e.g. from the also result in changes to the colour
non-significant (p=0.15) decrease moorlands. decomposition of fresh plant material of the water leaving the catchments.
at Spooners (Figure 22B) were over that from more humified peat).
In the short-term restoration has
observed, with average post- Neither changed significantly post-
not had a statistically significant
restoration loads of 48.9 and 13.2 restoration at Spooners (Figure
effect on the colour of the water (as REFERENCES
kg, respectively. This change becomes 23B and C). In contrast, there was a
measured by UV-Vis spectrometry The appendices are available to view
non-significant at both Aclands and significant change in both parameters
at 400 nm) leaving the catchments at www.exeter.ac.uk/creww/research/
Spooners when normalised for in the Aclands catchment post-
(Figure 23A). Both catchments casestudies/miresproject
total event rainfall (Figure 22C). restoration. The results suggest
discharge water colour which 1. Armstrong, A. et al. The impact of
Normalising for rainfall allows the that post-restoration the more
remains above the European peatland drain-blocking on dissolved
changes in load to be considered humified peat (i.e. old peat) remains
Commission standards (Abs400 of organic carbon loss and discolouration
irrespective of the variation in the primary source of the DOC of water; results from a national survey. J.
1.5 Au m-1)2.
rainfall for pre- and post-restoration leaving the catchments during rainfall Hydrol. 381, 112–120 (2010).
monitored events. Positively, this The colour to carbon ratio events, rather than a shift towards 2. Grand-Clement, E. et al. Antecedent
indicates that restoration activities (ColourAbs400/CarbonDOC) and the DOC arising from fresh material conditions control carbon loss and
have not contributed to a significant Specific Ultra-Violet Absorbance as observed on Dartmoor (see downstream water quality from shallow,
increase in DOC loads. However, it (SUVA -Abs254/DOC) are useful next section). Further research is damaged peatlands. Sci. Total Environ. 493,
does illustrate that a longer post- tools for understanding the chemical needed to attribute the significant 961–973 (2014).
26 Mires On The Moors Science and Evidence Report 27DARTMOOR DEEP PEAT WATER QUALITY
How does restoration effect dissolved organic carbon run-off
from a deep, eroding blanket bog?
R
ain falling on peatlands and in Specific ultra-violet absorbance
§ Post-restoration, the total load of dissolved organic carbon leaving flowing into rivers is a vital (Abs254/DOC)) (Figure 25 middle)
the mire during monitored storm events was roughly 1/3 of the pre- drinking water source. In their suggesting a shift towards carbon
restoration loads. current state, organic carbon is from fresh plant litter, as opposed to
§ Restoration had no statistically significant effect on dissolved organic being flushed from peatlands release of deeper and older carbon
carbon concentrations or water colour. and carried downstream. As this within the peat soil (Figure 27).
dissolved organic carbon reacts with
§ Chemical characteristics of the water (CAbs400/CDOC, SUVA) changed The change in dissolved organic
disinfectants to produce carcinogenic
significantly post-restoration suggesting a shift in the source of dissolved carbon concentration over time
by-products, South West Water has
organic carbon to fresher organic matter. during a storm event (hysteresis
a statutory duty to remove organic
index)4 suggests a step-change in
§ Restoration caused a step-change in hydrological connectivity; post- carbon in drinking water1 at the
the hydrological connectivity (Figure
restoration, dissolved organic carbon took longer to reach the sampler Water Treatment Works. Restoration
28). In a degraded mire, at the onset
as either sources were further away, transport was slower and/or aims to improve ecological
of rain, rapid surface/subsurface
pathways more tortuous. functioning of the peatlands; reducing
flow transports carbon from the
the production of dissolved organic
degraded peat into the gully. As
carbon at the source and therefore
the rainfall continues these sources
the total volumes reaching Water
are depleted leading to dilution.
Treatment Works.
Post-restoration dissolved organic
Water samples collected during carbon concentration increased
storm events pre-restoration over the storm, suggesting carbon
had dissolved organic carbon sources were more distant, pathways
concentrations from 6.2 to were longer or transport slower.
23.1 mg L-1. This was similar to Post-restoration rainfall raised the
concentrations found on Exmoor Figure 27 A change in water level in the pools until they
(4 to 21 mg L-1)2 but lower than water chemistry suggests overflowed (Figure 29). This overland
more northerly peatlands a shift in the dissolved flow, together with slower subsurface
organic carbon source
(20 - 62 mg L-1)3 heightened levels post-restoration to
flow transported dissolved organic
of degradation in response to paler, more hydrophilic, carbon to the gully later in the storm.
environmental change have resulted fresher organic material.
in an increased loss of dissolved
organic carbon (DOC).
Up to 3-years post-restoration there Figure 29 Slower overland flow occurring above
was no significant decrease the water quality monitoring location (at base of
the tube in the foreground) post-restoration. A
(p=0.694) in dissolved organic wooden dam is visible in the foreground.
carbon concentrations (6.9 to
24.9 mg L-1)4 (Figure 25 top).
Although the carbon concentration
did not change post-restoration, the
volume of water flowing though
the gully decreased (Figure 25
middle) and therefore the total
load of carbon being exported
during monitored storm events was
Figure 25 Despite no Figure 26 Restoration
significant effect of had no effect on water significantly (p=0.001) lower (Figure
restoration on dissolved colour (p=0.522) (top) but 25 bottom).
organic carbon significantly decreased
concentrations (p=0.694) specific ultra-violet
Restoration had no significant effect
(top), a significant reduction absorbance (p=0.011) (p=0.522) on water colour (Abs400)
in total sampled event (middle) and carbon (Figure 26 top), however, the carbon
discharge (middle) results discolouration (p=0.048) in the water was significantly paler
in a significant decrease (bottom) suggesting a fresher (p=0.048) (decrease in C Abs400/
(p=0.001) in total cumulative source of organic carbon
carbon load (bottom). post-restoration.
CDOC) (Figure 26 bottom) and more
hydrophilic (p=0.011) (decrease
28 Mires On The Moors Science and Evidence Report 29DARTMOOR: DEEP PEAT WATER QUALITY DARTMOOR: DEEP PEAT WATER QUALITY
Figure 4 Conceptual
model of dissolved
organic carbon
production and transport
pre- and post- restoration
Figure 5 Slower overland
flow occurring above the
water quality monitoring
location (at base of the
tube in the foreground)
post-restoration. A
wooden dam is visible in
the foreground.
Figure 28 Conceptual model
of dissolved organic carbon
production and transport pre- REFERENCES
and post- restoration.
The appendices are available to view at www.exeter.ac.uk/creww/
research/casestudies/miresproject
1. UK Statutory Instruments. The Water Supply (Water Quality) (Amendment)
Regulations 2018 No 706. (2018).
2. Grand-Clement, E. et al. Antecedent conditions control carbon loss and
downstream water quality from shallow, damaged peatlands. Sci. Total
Environ. 493, 961–973 (2014).
3. Wallage, Z. E., Holden, J. & McDonald, A. T. Drain blocking: An effective
treatment for reducing dissolved organic carbon loss and water
discolouration in a drained peatland. Sci. Total Environ. 367, 811–821 (2006).
4. Gatis, N. et al. Evaluating the effects of peatland restoration on storm event
DOC export. In prep.
30 Mires On The Moors Science and Evidence Report 31EXMOOR SHALLOW PEAT AGRICULTURAL
The grazing value of mires: How might restoration affect PRODUCTIVITY
agricultural productivity?
§ The nutritional quality of purple moor grass (Molinia caerulea) declines
between spring and autumn whereas species characteristic of intact
mires (bilberry (Vaccinium myrtillus), heather (Calluna vulgaris) and bog
asphodel (Narthecium ossifragum)) maintain relatively high nutritional
quality.
§ Population densities of the sheep tick, a vector of economically important
livestock diseases, are significantly lower in mires than in drier habitats on
the same sites.
§ Cattle spend little time in either degraded or restored mires, and so
restoration should have a negligible effect on the area used for grazing.
§ Restoration should have a minimal impact on the overall grazing value of
a site.
R
estoration is expected to
drive change in the vegetation
communities of Exmoor’s mires,
and as these lie within areas used for
grazing it is important to establish
what effect these changes might
have on the productivity of livestock
farming.
This study1 assessed the grazing
value of degraded and restored
mires, as well as other typical
Figure 31 Number of ticks found within grouped habitat types and Figure 32 Number of cattle dungs, a proxy for level of use by cattle of each
upland vegetation communities, proportion of the surveyed area assigned to each habitat type, where grouped habitat types and proportion of the surveyed area assigned to each
such as rush pasture and bracken- ‘Mire’ consists of transitional and blanket bog, ‘Degraded Mire’ for areas habitat type, where ‘Mire’ consists of transitional and blanket bog, ‘Degraded
dominated valley sides. The value of dominated by purple moor grass (Molinia caerulea), and Non-Mire for Mire’ for areas dominated by purple moor grass (Molinia caerulea), and Non-
each vegetation type was based on areas including bracken, dry grassland and rush. Mire for areas including bracken, dry grassland and rush.
three key factors: nutritional quality,
prevalence of sheep ticks (vectors of showed a sharp decline between avoided areas of mire and instead
livestock disease) and level of use by spring and autumn. In contrast, the showed a strong preference for drier,
grazing cattle. quality of species such as bilberry partially improved grasslands (Figure
The nutritional quality of a plant is (Vaccinium myrtillus), common 32), although the value of these
determined by a number of different heather (Calluna vulgaris) and bog was diminished by the fact that they
measures, but particularly important asphodel (Narthecium ossifragum), support far higher densities of sheep
from a grazing perspective are crude which are characteristic of ticks than areas of mire (Figure 31).
protein and digestibility, which affect, recovering and intact mire, remained However, as the effects of rewetting
among other things, how rapidly relatively high in both seasons. This are concentrated on areas of
an animal can gain weight. Levels of suggests that rewetting areas of mire degraded mire, these findings would
crude protein and digestibility were could increase the value of a site for suggest that restoration will have a
measured in 17 species of moorland livestock, as the associated increase minimal impact on the overall grazing
plants associated with habitats of
Figure 30 Changes in digestibility and crude in plant diversity ensures that the value of a site.
varying wetness (Figure 30). There
protein (%), measures of nutritional quality, in animals have access to vegetation
the spring and autumn for a range of moorland
was little difference in the overall plants grazed by livestock.
of acceptably high nutritional quality REFERENCES
nutritional quality of habitats, but throughout the grazing season.
The appendices are available to view
there were seasonal changes in the Neither prevalence of sheep ticks at www.exeter.ac.uk/creww/research/
relative quality of individual plant (Figure 31) nor level of use by cattle casestudies/miresproject
species, including purple moor-grass (Figure 32) differed significantly 1. Freeman, G. Assessing changes in the
(Molinia caerulea) – the dominant between degraded and restored agricultural productivity of upland
species of degraded mire – which mires. Grazing cattle generally systems in the light of peatland
restoration. (University of Exeter, 2017).
32 Mires On The Moors Science and Evidence Report 33EXMOOR SHALLOW PEAT TOXIC FLORA EXMOOR SHALLOW PEAT
Bog asphodel distribution following peatland METHANE EMISSIONS
restoration on Exmoor How does restoration age, vegetation and water
depth impact methane (CH4) emissions from
restored mires within Exmoor National Park?
T
§ Post-restoration bog asphodel (Narthecium ossifragum) continues to
survive but has not spread significantly. his study1 investigated the gaseous
§ Bog asphodel contributes up to 20 % forage value in transitional bog
Figure 33 A cluster of bog asphodel (Narthecium § Re-establishment of mire vegetation associated with wetter conditions carbon (C) balance of restored
ossifragum) flowers on Aclands July 2017. serves as a useful indicator for increased CH4 emissions, which in turn
habitats. mires in Exmoor National Park
indicates that restored mires on Exmoor are returning to a more natural using a restoration age sequence of
B
state. sites (from 6 months to ~7 years post-
og asphodel (Narthecium of transitional blanket bog habitat, § Annual CH4 emissions from restored sites on Exmoor are low, even restoration), as well as unrestored and
ossifragum) is a common comprising up to 18 % of forage after ~7 years post-restoration, suggesting that the timeline for mire semi-natural sites.
component of blanket bog value (Figure 35). This contribution restoration to a more natural state is likely to exceed 10 years. Increased cover of plants associated with
vegetation, seen as patches of bright may continue throughout the season, wetter conditions (e.g., Sphagnum moss)
green fleshy leaves growing from and its contribution to habitat crude and higher mean annual water levels
patches of rhizomes (underground protein value may even increase in were linked to increased methane (CH4) emissions
stems), with conspicuous yellow the autumn. and site restoration status (Figure 36 and 37). Higher
flowers in early summer1(Figure CH4 fluxes indicate the presence of anaerobic (oxygen
33). The leaves and especially the Figure 35 Bog asphodel (Narthecium deficient) microbial communities where microbial CH4
flowers are readily eaten by grazing ossifragum) forage quality at Aclands
generation (methanogenesis) occurs as a biproduct
livestock but contain toxins that can and Roosthitchen. Aclands (70 %
in the breakdown of organic matter. Therefore, CH4
cause acute photosensitization and bog asphodel cover) shows a steady
15-17 % contribution on 5 measures emissions, and thus methanogenesis, is an indicator that
fatal liver and kidney disease in lambs of quality, in both seasons. There was anaerobic conditions are becoming more dominant
and calves2,3. This research aimed to less bog asphodel at Roosthitchen Figure 34 Post-restoration change in
within the peat soil due to increased water saturation.
address concerns that restoration (18 - 30 %) and this contributes 5 – spread of bog asphodel (Narthecium
would increase the occurrence of 10 % on 5 measures of quality, less in ossifragum) over 18 sites on Exmoor. The Restoration activities on Exmoor seek to increase
x represents mean change (4.5±33.8 % 6
bog asphodel and consequently autumn than spring. Energy represents
to 11 years post-restoration).
water saturation levels within the peat soils, and
metabolisable energy (MJ).
livestock fatalities. therefore CH4 emissions can be viewed as a sign of
restoration success. Figure 37 shows that vegetation
The plant height varies from 10 to data, particularly percentage cover of mire species
40 cm depending on the density associated with wetter habitats, could provide a
of the surrounding vegetation and valuable tool for assessing CH4 emissions and site
possibly on early season grazing. conditions of restored mires.
Growth and flowering rates vary Figure 36 Mean annual water table position and percentage cover of
significantly year on year and may Sphagnum moss for study sites ranging from unrestored and newly Semi-natural sites (those with little or no impact from
account for the annual variations in restored (yellow) through to semi-natural sites/wet controls (blue). drainage and peat cutting) from this study showed
toxicity seen in northern UK and similar properties (i.e. gas emission balance, depth
Scandinavia. profiles of dissolved gases and stable C isotope
analysis) to natural peat soils elsewhere in Europe
Bog asphodel has a life history and North America. However, the semi-natural sites
strategy that enables it to thrive in from this study are likely still in a state of transition,
conditions intolerable to many plants also supported by vegetation survey data. Recovering
i.e. very wet, acidic and nutrient peat soils can transition through a stage of higher
poor soils4. It spreads only slowly CH4 emissions before lowering as the coverage of gas
by rhizoidal growth and does not conductive (aerenchymatous) plant species (e.g. cotton
rely on seed dispersal for survival. It grasses (Eriophorum spp.)) decreases, and conditions
does however persist in the most REFERENCES
within the peat soil stabilise.
challenging conditions. Analysis of The appendices are available to view at www.exeter.ac.uk/creww/research/casestudies/
its distribution at individual sites and miresproject
over 18 restored sites on Exmoor 1. Summerfield RJ. (1974). Narthecium ossifragum(L.)Huds. J. Ecol. 62(1), 325–339.
suggests it continues to survive 2. Angell, J., & Ross, T. (2011). Suspected bog asphodel (Narthecium ossifragum) toxicity in cattle REFERENCES
following peatland restoration, but in North Wales. Veterinary Record, 169(4).
has not spread significantly in the The appendices are available to view
3. Pollock, M. L., Wishart, H., Holland, J. P., Malone, F. E., & Waterhouse, A. (2015). Photosensitisation
at www.exeter.ac.uk/creww/research/
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