A Strategic Assessment of Afforested peat Resource in Wales

Samantha Broadmeadow*

Elena Vanguelova

Helen Cariss

Russell Anderson, Sirwan Yamulki, Tim Randle, Tom Nisbet & James Morison

04/07/2012 2

Policy background

Seeking greater diversity

within the AGWE including

more native woodland and

open habitats

WA recognises:

• the case for restoration of priority

open habitats within the woodland

estate including the removal of trees

from afforested deep peat

• the need for improved guidance on

habitat restoration and management

on deep peat soils to realise the

potential benefits in terms of carbon,

water resource, water quality and

biodiversity gains

04/07/2012 3

Afforested Peat in Wales

• Aim Strategic assessment of the afforested peat

resource in Wales - the biodiversity, GHG balance and hydrological benefits of various management options to target peatland restoration

• Objectives 1. Improved mapping of deep peat resource in

Wales

2. Literature review of existing evidence on the effects of management of afforested deep peat

3. GIS-analysis to categorise afforested peat and assess the biodiversity, GHG flux and hydrological implications of peatland restoration

4. Develop a rule-based criteria to identify the most suitable management options for afforested peat stands

5. Ground truth GIS mapping, analysis and rule based criteria

04/07/2012 4

Deep peat resource in Wales

NSRI & soil

mapping +

FC soil

survey

plus BGS peat

drift geology

mapping

plus deep peat-

land habitats,

Habitats of

Wales CCW

Spatial datasets of soil,

vegetation and geology were

combined to produce an

improved map of deep peat

in Wales; following the

method developed by

Shepherd for NE in 2010

04/07/2012 5

National map

Previous estimates of deep peat in Wales:

158,800 ha - Taylor & Tucker, 1968

69,530 ha - NSRI soil mapping only

Table 3 Area (ha) of different peat soil classes in Wales, derived using spatial data for soil, geology and habitat maps.

Deep Peaty Soils

Shallow Peaty Soils

Peaty Pockets

Other, mineral soils

116,400

(939 Peat and 225 Modified Peat)

343,800 79,200 1526,800

04/07/2012 6

Afforested deep peat in Wales

Table 6 Area (ha) of different peat soil classes in Wales, derived using spatial data for soil, geology, peatland habitats and the FC soil survey .

Deep Peaty Soils

Shallow Peaty Soils

Peaty Pockets

Other, mineral soils

Including FC soil survey data

116,200 316,900 81,300 1552,200

Excluding FC data ≡ Table 3

116,400 343,800 79,200 1526,800

Difference -0.2% -0.9% +2.7% +1.6%

04/07/2012 7

Afforested deep peat

Area (ha) of afforested deep peat owned and managed by the Welsh Assembly

04/07/2012 8

National priorities for restoration

The objectives:

• to determine which afforested sites in Wales offer the greatest

potential for restoration

• use the best available spatial data to determine the relative

suitability of an afforested site for restoration to an open peatland

Based on a review of the literature and expert

judgement, five criteria where selected:

1. current status of the peat

2. hydrological integrity of the site

3. greenhouse gas balance consequences of restoration

4. ecological integrity of the site

5. climatic integrity of the site

04/07/2012 9

National Assessment

1. National criteria for prioritisation, potential and viability for restoration of afforested land in Wales

advantagous neutral disadvantagous

2 1 0

Current status of

peat 1

Proportion of original

peat profile retained

on site ~ likely depth

to water table

1 NATMAP soil association 1

raw oligo-amorphous

peat soils - 1013b &

1013a + plus other areas

of deep peat identified in

NEW NATIONAL PEAT

MAP that are not earthy

peats

earthy peat soils 1022a

(fibrous grass-sedge

fen peat) & 1024a

(eutro-amorphous

humified peat)

modifed deep peat

plus all other

"peaty" soils

Undisturbed fen peats can potentially be very deep but the

potentially large C-store is considered to have been lost

because of the high fertility which had lead them to have

been extensively drained through history - need to consult

site soil monographs - seek advice from CCW? C reated

raster with 100m grid from reclassified NATMAP vector data

Can you retain water

on site to rewet peat?0.5 Slope 1 <4% 4 - 6% >6%

Slope derived from DTM (10 m grid) aggregated to 100 m

grid (to provide slope information at 'stand' scale) and

reclassed

rc_slope_agg

Hydrological impact

of drain blocking on

adjacent wetlands

0.25

Located upstream of

existing mire/bog/fen

habitat

1

vulnerable habitat

present downstream of

the afforested peat -

opportunity to

significantly improve

water supply to the open

peatland

vulnerable habitat

present in the

catchment - upstream

of the afforested peat -

limited opportunity to

improve water supply

to the open peatland

vulnerable habitats

not present in the

catchment

Vulnerable habitats ≡ SACs with following habitats: 7110

Active raised bogs; 7120 degraded raised bogs still capable

of natural regeneration; 7130 blanket bogsI. A site based

investigation of the consequences of restoration on the

drainage pathways off site is required to assess the

probable impact to adjacent sites.

HW_SAC_DISS

Impact on drainage

water quality0.25

Located within catchment

of potable water supply1

not used for drinking

water

within catchment of

resvoir

know which SWSP are located within catchments of DW

ReservoirsHW_RESERVOIRS_DISS

Above ground carbon

stocks1

Species and YC [Canopy

type] - SPP & YC [NIWT]1 Marketable: High YC≥10 Marginal: YC 8

Uncommercial: Low

YC≤8 plus

Broadleaves

Within FCW estate data taken as principal component of

the subcompartment. Outside the FCW estate use the IFT

from the new NFI map {see table 1 for full query details}

Afforested_Peat_GHG_dissolve

Non-C GHG emission

consequences of

peatland restoration

Sirwan's model [rainfall,

temp, N dep and SW

DOC]

Non-C GHG no trees;

NO2 - low nutrient soil

status/low N deposition

The removal of trees from drained land causes the loss of

CH3 - but because the areas are small CH3 emissions are

unlikely to be a deciding factor in the selection of sites for

restoration

What about geology and peat type

relationship with water quality, e.g. rich

fens agains poor bogs? - ELENA

Current canopy species -

NFI_IFT & BAP0.5 conifer plantation broadleaf

Native wet

woodland BAP

habitat

There is no spatial data avaliable for wet woodland habitat in

Wales: use SACs including 91D0 Bog woodland and 91E0

Alluvial forest to identify areas of afforested peat that can be

retained.

Rarity 0.5

potential lowland raised

bog habitat - Lindsay and

Immirzi (1996) Inventory

of lrb sites in GB - used

to select afforested peat

adjacent to key habitat -

restoration could lead to

expansion of habiat (FC

soil type would be better

data source)

potential fen peat

habitat - fen peat soil

associations

potential blanket

bog habitat

Potential nature

conservation of

restored site

assuming removal of

conifer forest

0.5

Functional connectivity to

combined dataset of

CCW potential wetland

habitat networks1

1

inside core low-cost

conifer bog habitat

network

inside focal low-cost

conifer bog habitat

network

outside bog habitat

network

Data sets for open wetland habitat networks: fens, mires

and bogs to be provided by Dr James Lathan at CCW

(when available - before 22nd July 2011). These data sets

will represent the existing conifer forest as a permeable land

cover i.e. assumed that trees are removed and site is

accessible for colonization.

sac_peatland2

Current climatic

suitability0.75

BBOG-GAM model

output for baseline (61-

90) data

1

0.25 - 1.0 (area covered

contains 75% of the

mapped blanket peat)

0.1 - 0.25 (area

covered contains 90%

of the mapped blanket

peat)

0 - 0.1 (area

covered contains

10% of the mapped

blanket peat)

Clark et. al., (2010) Climate Research 45:131-150.

BBOG_GAM was the single model that best matched the

mapped current distribution of blanket bog across Wales.

The model includes Tmin, continentiality and TMI (modified

Thornthwaite-Mather moisture index). The values represent

the quantile of 'mapped blanket peat area' within the

bioclimatic envelope i.e. the 0.25 - 1.0 class includes 75% of

the mapped blanket peat area across the UK.

rc_bbog_gam

Modelled future

climatic suitability

under predicted

climate change

0.25

Combined model outputs

ESM8_LO.2080 (Clarke

et al 2010)

1 4 - 8 models 1 - 3 models none

Clark et. al., (2010) Climate Research 45:131-150.

Projected changes in bioclimatic space associated with

predicted climate change using 8 bioclimatic envelope

models and UKCIP02 low emission senario for 2080s

rc_esm8_low80

WF Source of information Spatial DatasetSITE POTENTIAL ISSUE Criteria Proxy - FactorWF WF

Threshold values/classes

0.5Rarity of restored

peatland habitat

SCORE: X out of 3.

Score of 3: GOOD

potential for

restoration, highest

priority sites. Score

of 2: considering in

time as part of the

normal forest

planning process.

SCORE of 1:

suitable for

continued use as

conifer forest

1

Hydrological

integrity of site

HYDRO_SUIT

1GHC Balance

Climatic integrity

CLIM_ENV_SUIT1

Ecological integrity

of site1

04/07/2012 10

National assessment

04/07/2012 11

Ground truthing the national assessment

Gwydyr Forest

First rotation Sitka spruce (PY 1966)

basin bog, mapped FC soil type 8c

Juncus effusus (basin) bog.

On site we found the peat depth under

stand typically >1.3 m.

The stand was adjacent to open habitat

and had good sphagnum cover

remaining under gaps in the canopy.

* Deemed to be restorable.

04/07/2012 12

Management options for afforested peat sites

Retain

conifers long

term

Restore to

open grazed

heath/acid

grassland

habitat

Remove current

crop & block drains

- plant native XB

on peaty soils and

leave deep peat

open

Restore to

functional

mire habitat

Remove

conifer crop

and convert

to native

bog

woodland

Fell to waste

- use timber

on site to

block drains

Q1:Is it

possible

to raise

and

maintain

water

table?

Q4: Is

there a

significan

t peat

resource

on site?

Q2: Can

crop be

cost-

effectivel

y

removed

from

site?

Q3: Is

open

mire

most

suitable

restoratio

n

objective

for site?

Q5: Is

there

merit in

restoring

open

habitat?

Q5: Is

there

merit in

restoring

open

habitat?

YES: site

flat /

limited

peat

cracking

NO: sloped site - peat severely cracked

or water regime compromised by

drainage system off site

YES

YES: perhaps

in a mosaic of

soil types

NO: mapping

error -

peaty soil

NO: cost of

extraction

too high

No

YES: good connectivity to

existing habitat

YES

No

YES: close proximity

to priority habitat or of

potential value to

important species

No

Remove current

crop, restock in

response to soils

and topography,

leave areas of

deep peat

unplanted

04/07/2012 13

Assessing the merits of peatland restoration on site

Advantageous to

cost effective

restoration

Disadvantageous to

cost effective

restoration

Difficult/expensive

to restore

successfully

Slope Flat sites <4% >4%

Slope / peat crackingFlat sites and/or

no cracking

Peat not cracked

between plough

furrows

Peat cracked

between plough

furrows

Drainage: drain depth & condition

Infilled with

sphagnum? <30

cm

>30 cm

>60 cm/eroded to

mineral layer - flow

suffcient for drains

to be self cleaning:

therefore difficult to

block

Drainage: is it possible to block the

drains by damming the dranage

network at a key point within the

restoration site?

Yes key point for

drain blocking

present on site

No, but few dams

required

No, many dams

required on site

Drainage: is it possible to

modify/control drainage across the

wider landscape to ensure

appropriate water supply to site

water regime on

site near natural

and appropriate

drain network on

upslope/adjacent

sites requires

modification to

mainatain suitable

water supply to peat

on site

unable to maintain

suitable water

regime on site due

to condistions of off

site drainage

Bog Edges Intact Cutaway Eroded

Species - relevant to brash

management during opperations

plus the need to control of regen.

SS or SS/LP Other conifer Broadleaf

YC YC<8 YC 8 - 10 YC>12

Distance to road <1 km > 1km

Tree age End rotation age Mid rotation age Early rotation age

Scarcity of peatland type in Wales

Basin mires,

raised bogs &

bog woodland:

FCST 8, 10 & 9a

unflushed peat: FCST

11Hill peat: FCST 9

Field layer and ground layer

species

Remnant bog

vegetation

including

sphagnum

Juncus Bramble? Mollina?

Sphagnum coverage in adjacent

rideshigh cover scattered cover not present

Proximity to phase 1 peatland

habitat or open wetland habitat

within forest

adjacent <200 m >200 m

Soil Type - FC classification 8a, 8b, 9b, 9e,

10b, 11b8c, 9a, 9c, 9d, 14 14h, 6p

Duration of afforestation - PY of

first rotation< 15 y 15 - 50 y > 50 y

Scheduled Ancient Monument absent presentForest block is a flagship

recreational site e.g. has visitors

centre etc.

present absent

Distance from car park/bike

route/footpath<100 m 100 - 500 m >500 m

Current Water Table depth <50 cm 50- 100 cm >100 cm

Depth of peat oxidated layer <20 cm 20-50 cm >50 cm

DOC/colour of drainage water highly coloured visible colour clear

Threshold values/classes

Hydrological integrity of

site

Are there any

additional

benefits?

Community interest in

forest

GHG Balance

Q4: Is there

still

significant

peat on site?

Q3/Q5: Is

open mire

most suitable

restoration

objective for

site?

Ecological integrity of

site

Q2: Can

conifer crop

be cost

effectively

removed from

site?

Factor

Current status of peat

ISSUE Criteria

Q1: Is it

possible to

raise and

maintain

water table?

Current economic

viability of standing

timber

04/07/2012 14

Summary

Mapping of deep peat resource in Wales has been

improved

National afforested peat map was created

National assessment of afforested peat restoration

potential was successful – as tested by FC Wales

Site assessment based on field observations has been

applied and simplified by Russell Anderson

This work will be used by FC Wales & CCW to assess

site restorability and management options in future

forest design plans and wind farm programme