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Transformation of Sitka spruce plantations to continuous cover forestry at Dunranhill Forest, County Wicklow, Ireland. [Scottish Forestry 75(4) 32-39]

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  • Silviculture Research International

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This case study describes recent developments at Dunranhill Forest, County Wicklow, Ireland. The forest was established in the early 1980s as a commercial Sitka spruce plantation. Currently it is being transformed to continuous cover forestry (CCF). The paper presents an overview of past and present forest management, decisions related to stand transformation, and technical information on the silviculture and thinning operations within the forest. Central to the success of stand transformation is the management of light levels in the understorey, through control of basal area, while maintaining stand stability and promoting the quality of the standing trees. An adaptive approach to crown thinning has been implemented, creating a matrix of microsites that support an irregular distribution of natural regeneration. Deer management is a major concern, and a combination of deer exclosures and population control are critical for forest regeneration. Diverse species are being encouraged, to support the development of a mixed-species forest into the future, with seed dispersal from adjoining properties. The owners are among the first to participate in a new CCF Woodland Improvement Scheme launched in 2019 by the Irish Forest Service. Keywords: silviculture; continuous cover forestry (CCF), closer-to-nature forest management, stand transformation, irregular stand structure, adaptation, resilience, sustainable forestry, Ireland.
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32 | SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021
Introduction
There is growing interest in Continuous
Cover Forestry (CCF) in Ireland. In
recent years, a range of new initiatives
and programmes have been introduced
that are stimulating wider engagement
among owners and managers (Wilson
et al., 2020). Many established
productive woodlands are now at a
stage where thinning can take place in
line with technical guidance on stand
transformation to CCF (Teagasc,
2016). In this report we describe recent
experience at Dunranhill Forest, near
Newtownmountkennedy, County
Wicklow, Ireland. This productive Sitka
spruce (Picea sitchensis) woodland has
been under active CCF management
since 2014 and is one of the first
woodlands to join the CCF Woodland
Improvement Scheme (CCF-WIS),
administered since 2019 by the Irish
Forest Service, part of the Department
of Agriculture, Food and the Marine
(DAFM) (DAFM, 2019).
Location and site information
County Wicklow is located in the south
east of Ireland. It is known as the Garden
of Ireland but also has a rich tradition
in forest management. Avondale House
and Forest Park, at Avondale, County
Wicklow, was purchased by the state
in 1904 and is regarded as the historic
home of Irish forestry and silviculture.
The county has a forest area of 6,6ha,
making it the second most-wooded of all
counties in Ireland (.% of land area)
(DAFM, 2020).
Dunranhill Forest (.8°N,
6.°W) is located approximately km
(three miles) south of the village of
Newtownmountkennedy. It is typical
of productive forests in the region,
occupying high ground in a landscape
mosaic of farmland, moors and woods
(Figure 1). Dunran Hill (m) is a
prominent landscape feature, with
farmland to the west and north, and
open moorland to the south. To the east,
the property adjoins a mature woodland,
Dunran Demesne, managed by Coillte,
the state-owned forestry company. To
the east, it adjoins a private woodland
also committed to CCF (Figure 2).
Overall, the altitudinal range for the
forest is m. The climate is relatively
warm and temperate (annual average
.8°C) with annual precipitation of
,mm.
The total area of the Dunranhill
property is 88ha. The majority of the
productive forest is located to the north
and east of the hill, and is relatively
sheltered from prevailing winds. The
soils are mostly shallow brown earths
over shales, with frequent rocky
outcrops. The soil nutrient regime is
moderate, except in Compartment ,
which is richer. The site is free draining
throughout. Slopes are generally
moderate, although there are several
steeper areas that are more challenging
to access with harvesting machinery.
Most of the site was unimproved upland
pasture, except for two fields in the
Transformation of Sitka spruce plantations
to continuous cover forestry at Dunranhill
Forest, County Wicklow, Ireland
By Edward Wilson, Rainer Wirz and Liam Byrne
This case study describes recent developments at Dunranhill Forest, County Wicklow, Ireland. The forest was established in the
early 1980s as a commercial Sitka spruce plantation. Currently it is being transformed to continuous cover forestry (CCF). The
owners are among the first to join the new CCF Woodland Improvement Scheme launched in 2019 by the Irish Forest Service.
Research
THE AUTHORS
Edward (Ted) Wilson* is a silviculturist with interests in tree biology, silvicultural systems and
forest conservation. He is a Walsh Scholar with University College Dublin and Teagasc, Ireland,
and Adjunct Professor of Silviculture at the University of Toronto, Canada. His current research
focuses on transformation of conifer plantations to CCF.
Rainer Wirz is an independent forestry consultant with over 30 years’ experience in Germany,
South Africa and New Zealand. He has been providing forest management and consultancy
services in Ireland since 2013, specialising in CCF and native woodland projects.
Liam Byrne is a director of Larry Byrne and Sons (Timber) Ltd, a family-run forestry and timber
business based in Glenealy, County Wicklow. He has wide experience in har vesting operations
and a particular interest in CCF. Liam currently serves as Chair of Pro Silva Ireland.
*Corresponding author. Contact: ted.wilson@silviculture.org.uk
SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021 | 33
west and north-west of the property
(Compartments  and ) that were
actively farmed until the property
was converted to forestry. Yield Class
(maximum mean annual increment, m3/
ha/yr) ranges from  (lower, sheltered
areas) to  (upper, exposed areas), with
a significant area of the forest averaging
YC .
Ownership and management policy
The Dunranhill property was owned
by a local farming family until around
1980, then sold to new owners interested
in converting the land use to forestry.
Planning was initiated in 1981 under
the woodland establishment scheme
in operation at that time. The original
objective was to establish a conventional
even-aged forest, which would be
clearfelled on a rotational management
system. However, the forest was sold in
2013 to the present owners, a family with
roots in Germany. The current manager,
Rainer Wirz of Forst Service Wirz, has
experience of German forestry practices
and traditions (Naturgemaeßer Waldbau)
and, in discussion with the owners,
opted to embrace a CCF management
policy following ‘Pro Silva principles’
(Pro Silva Europe, 2012). Pro Silva is a
European confederation of professional
foresters who advocate and promote
‘close to nature’ forest management
as an alternative to rotation-based
plantation systems. The objectives are
to sustain a steady income from timber
and deliver other ecosystem services,
including biodiversity and landscape
conservation.
Continuity of personnel has been
an important feature of management
at Dunranhill Forest. All thinning,
harvesting and timber sales from 2007
onwards have been undertaken by Larry
Byrne and Sons (Timber) Ltd. Road and
other infrastructure operations have
been completed by M and S Ryan Plant
Hire Ltd. Since 2013, Forst Service Wirz
has provided forest management services
and acted as the property manager
on behalf of the owners. Silvicultural
prescriptions and tree marking activities
are jointly implemented by Rainer Wirz
and Liam Byrne (Larry Byrne and Sons
(Timber) Ltd). Both are active members
of Pro Silva Ireland. Deer management
Figure 1 (left). A view of Dunranhill Forest from
the north, 2020. The unplanted area is visible on
the skyline to the left-centre of this scene.
© ER Wilson
Figure 2. Aerial view of Dunranhill Forest showing the boundaries, compartments and main features of the property. The boundary of the area included in the
CCF Woodland Improvement Scheme is identified. Base image: Google Earth.
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34 | SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021
is coordinated by Rainer Wirz, working
closely with the owners and neighbours.
Woodland creation
The site was prepared using a shallow
plough to create suitable microsites for
planting. Furrows were at approximately
1.8m spacing on the lower ground and
slopes. At higher elevations the spacing
was more varied due to the roughness of
the terrain and increased prevalence of
rocky outcrops. The initial plan was to
maximise the productive forest area and
to plant the entire site with Sitka spruce.
A small number of Japanese larch (Larix
kaempferi) seedlings were mixed in with
the spruce during planting. This was a
common practice at the time to enhance
the aesthetic and amenity value of the
woodland.
Compartments  to  were planted
at a spacing of approximately .8m x
8m. Further up the hill this extended
to between m and sometimes m
(particularly in Compartment 8).
Following establishment, trees in this
higher area were adversely impacted by
deer browse and vegetation competition,
which has led to an irregular spacing.
A combination of rocky outcrops and a
shortage of planting stock resulted in an
area of ha of higher ground being left
open and unplanted. Several years after
the initial planting, a grass fire jumped
the fence and into the forest along the
southern margin of the property. This
destroyed a significant area of thicket-
stage woodland, most of Compartment 
and part of Compartment , which was
subsequently re-stocked.
Taking into account roads and landing
areas, the stocked woodland area
amounts to ha.
More recent assessments of the forest
have shown that timber quality is good in
sheltered areas and at lower elevations.
This is likely a function of genetics
(although no nursery records have been
retained) and the high planting density.
At higher elevations, where the trees
are more widely spaced and exposed,
the timber quality is noticeably more
variable. Trees are generally shorter and
coarser in appearance; stem straightness
is lower and branches are often heavier
compared with sheltered areas.
Thinning strategies
The first thinnings were initiated
in 2007–08. This was later than
recommended practice (Farrelly,
2012), due to logistical difficulties with
establishing roads and infrastructure.
At this time, stand top heights were
m-plus in the sheltered and more
productive areas. This dictated a
conservative thinning policy. The key
consideration was to initiate density
management without adversely affecting
stand stability. Wherever possible,
a harvester and forwarder team was
engaged to fell and extract the timber.
However, manual felling was also
necessary in some of the steeper areas.
The forest has always been nurtured
with an adaptive management
philosophy aimed at keeping options
open for the future. Conventional
thinning regimes were applied in the
early stages, but some consideration
was given to CCF from the start. Rack
spacings are mostly every ninth row
(i.e. 6–m, average 8m), although
there was significant variation due to
site factors and differences in initial
tree spacing. In addition to racking, a
low thinning was applied to the matrix.
Some areas, mostly on the south side of
Dunranhill, remained unthinned at the
first intervention due to their younger
age and poor access.
Since 2013, thinning operations
have been planned on a three to four
year cycle with the aim of extracting
–m3/ha of roundwood at each
intervention (Figure 3). This level
of production provides consistent
quantities of timber that underpin the
economic sustainability of the forest.
The second thinning took place in some
sections in 2011. This was followed by
operations in 2014, 2016, 2018, 2019 and
2020. Further expansion of the road
network in 2015–16 allowed improved
access to the entire forest, so that by
2020 most areas had been thinned two
to four times.
In 2020, Compartment  (6.ha),
one of the most productive areas of the
forest, was clearfelled. Two reasons for
this decision were the strong timber
markets and the poor prospects of
securing natural regeneration. As a
legacy of past land use, dense swards
of grass had taken hold across the
compartment. This represented a barrier
to natural regeneration and the option to
under-plant was considered too costly.
The compartment will be restocked
with a mixture of broadleaf and
conifer species in group planting, with
consideration to the future potential for
CCF.
Operations are timed, as much as
possible, to avoid the active growing
season and wettest period. This
minimises the risk of damage to the
residual standing trees. Extra care is
required with operational racks to
Figure 3. A view of the stand in Compartment 5 after four thinning interventions, 2021. The best-quality
trees have been retained and released from competition. Competitor and poor-quality trees are
gradually being removed. The stand is being managed on a crown thinning regime with a conscious
eort to create a diversity of microsites so that regeneration can be established in small patches at
dierent stages in the transformation. © ER Wilson
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SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021 | 35
Figure 4. A patch of Sitka spruce seedlings established in a small canopy gap in Compartment 5, 2019.
Thinning prescriptions aim to create a diverse forest canopy with variable light levels on the forest floor. It
is anticipated this will support further development of an irregular stand structure. © ER Wilson
minimise soil impact and rutting, as
most racks are used repeatedly into
the future within a CCF management
system.
Crown thinning and natural
regeneration
The first two interventions were
conventional thinnings, with an
emphasis on promoting quality trees.
The more recent policy has been to
adopt crown thinning which is advocated
for transformation of even-aged
plantations to CCF (Vitková and Ní
Dhubháin, 2013; Wilson et al., 2018;
Cameron, 2020). In crown thinning, the
best-quality trees (with good stability
attributes) are selected for retention;
competitors and larger, poor-quality
trees are marked for removal. Other
trees, especially smaller individuals, are
retained for future selection. Release of
the best-quality trees at an early stage in
the transformation has a positive impact
on stability (Price, 2021). Increased
wind forces acting on these trees, along
with increased growth rates, lead to
alterations in photosynthate allocation
to the stems and roots. This adaptive
growth results in lower height:diameter
ratios, a key index of tree and stand
stability (Cameron, 2020; Mason, 2002).
This form of thinning also delivers the
necessary structural differentiation and
irregularity in spacing to facilitate and
control natural regeneration (Malcolm et
al., 2001; Cameron, 2020).
By the third thinning, many trees had
reached maturity and were producing
seed, which is essential for initiating the
transformation. Patches of seedlings
then started to occur in some of the
more open microsites where larger
trees had been removed, most notably
in Compartment  (Figure 4). This
prompted an adaptive strategy for
tree marking. Small gaps are now
being gradually opened to provide the
necessary light for continued seedling
recruitment and growth, effectively a
process of ‘light management’.
Basal area (BA; the cross-sectional
area of all stems/ha measured at breast
height) in m2/ha is an important metric
used to guide the management of stand
transformation (Page et al., 2001; Kerr,
2008). The mean BA across the forest
is approximately m2/ha (Table 1).
However, there is considerable variation
due to past management and the timing
of thinning operations. Sitka spruce
has intermediate shade tolerance and
natural regeneration typically takes
place in the BA range –m2/ha,
though for more shade tolerant species
the ranges are higher; the optimum
range for establishing seedlings is
–m2/ha and for sustained seedling
growth is –m2/ha (Kerr, 2008). As a
result, some areas are regenerating more
quickly than others.
The basal area is regulated by the
timing, intensity and pattern of thinning
operations. In unthinned stands, BA can
increase to over m2/ha. Getting the
basal area down to the target range for
natural regeneration requires careful
consideration. Removing too much
timber in one operation, or delaying
thinning interventions, can destabilise
the stand. Taking too little does not
facilitate natural regeneration. In most
cases, on windfirm sites, a maximum of
% of the basal area is removed in any
one thinning intervention. However,
as the stand immediately responds and
the basal area increases again, it can
take several thinning interventions to
achieve the target basal area for natural
regeneration to occur and be sustained.
Compartment Mean DBH (and
range) (cm)
Mean top
height (m)
Mean H:D ratio1
(dominant trees)
Stand density
(N/ha)
Mean BA
(m2/ha)
CCF-WIS Area
(4,9,10)
33 (19–48) 24 59 383 34
3 29 (19–35) 25 71 500 34
5 27 (14–42) 24 64 533 33
6 32 (28–36) 22 54 600 47
7 26 (22–33) 16 49 700 38
8 26 (18–39) 18 46 500 29
Forest average 29 (14–48) 21 59 536 36
Table 1. Compartment inventory data for Dunranhill Forest (March 2021). Variation between
compartments is due to dierences in establishment, thinning interventions and site exposure.
Note: 1 Height:Diameter (H:D) ratios for individual compartments are the mean of trees with the largest
DBH in each survey plot. Values <80 are considered stable (see Cameron, 2020).
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36 | SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021
Figure 6. Comparison of natural regeneration in Compartment 5 and the CCF-WIS area at Dunranhill
Forest (March 2021). Sitka spruce was categorised by seedlings (with secondary shoot development)
and germinants (with cotyledons only). Unthinned plots are retained in each area to inform management
of these stands.
How this works in practice can
be demonstrated by comparing the
development of Compartment  with the
CCF Woodland Improvement Scheme
(CCF-WIS) area (Compartments , 
and ) (Figure 5). At an inventory
prior to the 2021 growing season, the
BA in each of these areas was broadly
similar at  and m2/ha, respectively,
but management history was different.
Compartment  was last thinned in
2018–19. Approximately % of the
standing basal area was removed at
that time, giving a residual BA of m2/
ha. Assuming ingrowth of m2/ha/year,
the stand BA increased to m2/ha over
two growing seasons, still within range
for natural regeneration. Nevertheless,
after the 2021 growing season, the BA
will likely rise above m2/ha, and the
potential for natural regeneration is
expected to diminish. If a thinning
operation were to take place in 2021–22,
as planned, the stand BA will remain
within the appropriate range to allow for
sustained seedling recruitment.
Conversely, in the CCF-WIS area, the
most recent thinning operations took
place during winter 2020–2021. Prior
to this, the overall BA was estimated to
be m2/ha (lower in Compartment 
due to more frequent interventions).
As a result, the basal area in growing
seasons 2018, 2019 and 2020 was mostly
above the threshold levels for natural
regeneration of Sitka spruce. Following
the latest thinning the residual basal area
dropped to m2/ha, but it will likely be
another two or more thinning cycles
before the stand can be managed within
the appropriate range for sustained
recruitment and development of Sitka
spruce seedlings.
An understorey survey in March 2021
highlighted the impact of thinning on
natural regeneration in the CCF-WIS
area and Compartment  (Figure 6).
Linked to the adaptive management
philosophy, several unthinned plots
have been retained in the forest to
demonstrate the effect of thinning
and basal area management on stand
regeneration. In Compartment , for
example, the control plot has a basal
area of 6m2/ha, compared with m2/
ha elsewhere. All the regeneration
in Compartment  was Sitka spruce,
recorded as seedlings (with secondary
shoots) or germinants (with cotyledons
only). The seedlings were under cm
tall and not yet free from browse
damage. The profusion of germinants
arose from the mast year in 2020; high
mortality is expected. Under more
shaded conditions in the CCF-WIS area,
there was less natural regeneration, but
greater species diversity. This is due to
dispersal of seed from shade tolerant
species (grand fir and western hemlock)
from the adjoining property.
At the present time, there is little
competing vegetation in the understorey,
and limited evidence of bramble taking
hold. Rhododendron and laurel, which
Figure 5. Basal area dynamics in Compartment 5 and the CCF-WIS area at Dunranhill Forest. The
inventory took place prior to the 2021 growing season, and illustrates past (solid line) and projected
(dashed line) stand development through five growing seasons (2018 to 2022). The estimated ingrowth
is 2m2/ha/yr. The basal area ranges are shown for: 1 seedling establishment (30−35m2/ha) and
2 sustained seedling growth (25−30m2/ha) (Kerr, 2008).
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SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021 | 37
Figure 7. A mini exclosure located around a patch of naturally-regenerating Sitka spruce seedlings in
Compartment 5, 2021. The fences are 1.7m tall and cover an area of approximately 50m2. It is
anticipated the fencing will be moved to other locations in the forest once the seedlings are fully
established and free from the risk of browsing. © ER Wilson
Figure 8. An oak tree finding its way through a boundary wall (Compartment 9), 2019. Landscape and
other natural heritage features are retained wherever possible. They are a source of joy and satisfaction
for the woodland owners, and enhance the overall amenity value of the property. © ER Wilson
are much in evidence throughout County
Wicklow, are not significant issues at
Dunranhill. Slightly heavier thinnings
are now being trialled in some of the
sheltered areas to release established
patches of seedling regeneration. Care
needs to be taken in managing light
levels to facilitate seedling establishment
while minimising the risk of grass and
other competing vegetation dominating
the site (Price, 2021). The absence of
significant wind damage is a source of
cautious optimism with respect to crown
thinning and gap expansion.
Deer management
County Wicklow is noted for the high
number of sika deer (Cervus nippon) now
resident in most woodlands. Ongoing
and active control of deer is an essential
component of a CCF management policy
if natural regeneration is to be secured.
In 2019, a series of mini exclosures
were installed to reduce the risk of
deer browse on natural regeneration
(Figure 7). Monitoring browse damage
is important for designing and planning
the next cycle of thinnings.
Amenity features
The owners have a deep appreciation
of the historic and landscape attributes
of the forest. The ruins of two ancient
farm dwellings have been preserved
and stabilised, several wolf trees have
been retained for habitat and landscape
purposes, and legacy broadleaves
have been given more space to grow
(Figure 8).
CCF Woodland Improvement
Scheme
Dunranhill Forest was among the first
applicants to join the new CCF-WIS.
Details of the scheme are described by
Wilson et al. (2020) and on the Teagasc
Forestry website (Teagasc, 2021). The
most important criteria for entering the
scheme are:
1. Free-draining mineral soils (peats,
deep peats, wet peats, waterlogged
sites and gleys are to be avoided)
2. Capability to grow Sitka spruce to
Yield Class  or greater
3. Sites subject to severe and persistent
threats (e.g. rhododendron, deer)
must have a comprehensive action
plan
4. Elevations above m should
be avoided due to the increased
windblow risk.
In terms of financial support,
the applicant must devise a CCF
Transformation Management Plan that
will run for  years. Three instalments
of up to €/ha can be claimed for
planned activities. The first payment is at
year one with the final payment at year
, based on completion of the approved
schedule of works. The middle payment
can be paid at any stage during the
intervening period. A maximum area of
ha can be included in the plan.
At Dunranhill, the ha block
included in the CCF-WIS incorporates
Compartments ,  and  (part)
(Figure 2). These are located along
the eastern boundary of the property
and adjacent to Dunran Demesne.
One of the reasons for selecting these
compartments is the diverse range of
species in the neighbouring property,
Figure 10. Controlled release of a future quality
tree in the CCF-WIS area (Compartment 9),
shown here in 2021. Gradual removal of
competitors allows for crown development on the
best quality individuals and creates gaps for
natural regeneration. © ER Wilson
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38 | SCOTTISH FORESTRY Volume 75 No. 4 Winter 2021
Table 2. Example management schedule for 2020–2032 in Compartment 9, Dunranhill Forest, which
is part of the area within the designated area of the Woodland Improvement Scheme for CCF.
Year Compartment Proposed Actions
2020 9- Preparation of a site-specific CCF management plan
- Pre-thinning tree marking
- Improvement felling of malformed trees
- Ground preparation, light scarification
- Deer management
- Enrichment planting where necessary
2026 9- Pre-thinning tree marking
- Improvement felling of malformed trees
- Ground preparation, light scarification
- Deer management
- Enrichment planting where necessary
- Management and respacing of natural regeneration
2032 9- Pre-thinning tree marking
- Improvement felling of malformed trees
- Ground preparation, light scarification
- Deer management
- Enrichment planting where necessary
- Management and respacing of natural regeneration
Figure 9. View of Compartment 9 in 2021 after the completion of a thinning operation in December
2020. The variable size of stumps reflects the evolution of management practices, with some of the
smaller trees being removed in the early thinnings, and larger trees being removed more recently. Care
in all operations is essential to minimise the risk of mechanical damage to residual trees, and also to
minimise damage to the site. © ER Wilson
including Douglas fir, grand fir, western
hemlock, beech, oak and other native
species. Early indications are that seed
is spreading into Dunranhill, which
will help increase species diversity into
the future. In addition, this is the most
sheltered part of the forest and at the
lowest risk of wind damage, making it
possible to apply different intensities
of thinning and to modify gap sizes
in response to the developing natural
regeneration (Figures 9 and 10).
The CCF Transformation Management
Plan was approved in 2020. The schedule
for Compartment  is provided in
Table 2. Most important is support
for the costs of tree marking and deer
management. It is hoped that natural
regeneration will be the primary method
for securing the next generation of trees.
Enrichment planting makes it possible
to diversify the species composition, and
enhances the resilience of the forest to
threats from climate change, pests and
diseases.
Final comments
Dunranhill Forest demonstrates
many features of contemporary forest
management in Ireland. An adaptive
management philosophy has given
the owners and forest management
team an opportunity to respond to
both the forest’s development and
innovations taking place in the forestry
sector. Application of crown thinning
is increasing the diversity and irregular
structure of the forest. The new CCF
Woodland Improvement Scheme is
supporting a range of activities and
interventions that will sustain the
continued production of high quality
timber, facilitate natural regeneration
and deliver additional ecosystem
benefits.
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Acknowledgements
We thank the owners of Dunranhill
Forest for their support and permission
to prepare this report. We also thank
Karen Murray, Padraig O’Tuama,
Jim Ralph and Dr Martin Price for
helpful comments and advice during
preparation of the manuscript. This
is a revised version of an article that
originally appeared in the CCFG
Newsletter (Wilson et al., 2021).
References
Cameron, AD (2020) Transforming even-aged
spruce stands into species-diverse irregular forests.
Scottish Forestry 74(2): 21–29.
Department of Agriculture, Food and the Marine
(2019). Woodland Improvement Scheme (Element 2)
– Continuous Cover Forestry. DAFM, Dublin.
Department of Agriculture, Food and the Marine
(2020) Forest Statistics Ireland 2020. DAFM,
Johnstown Castle Estate, Co. Wexford.
Farrelly, N (2012) The practice of thinning forest
crops. Forestry and Energy Review 2(1): 28–30.
Kerr, G (2008) Operational Guidance Booklet
7: Managing Continuous Cover Forests. Forestry
Commission, Edinburgh.
Malcolm, DC, Mason, WL and Clarke, GC (2001)
The transformation of conifer forests in Great Britain
– regeneration, gap size, and silvicultural systems.
Forest Ecology and Management 151: 7–23.
Mason, WL (2002) Are irregular stands more
windfirm? Forestry 75: 347–355.
Page, LM, Cameron, AD and Clarke, GC (2001)
Influence of overstorey basal area on density and
growth of advance regeneration of Sitka spruce
in variably thinned stands. Forest Ecology and
Management 151: 25–35.
Price, M (2021) Spruce, soils and CCF. CC FG
Newsletter 44 (Summer 2021): 3, 1–9.
Pro Silva Europe (2012) Pro Silva Principles. Pro
Silva Europe: the Association of European Foresters
Practising Management which follows Natural
Processes. Barr, France. Available at: https://www.
prosilva.org/close-to-nature-forestry/pro-silva-
principles/ [Accessed 13 Oct 2021]
Teagasc (2016) Continuous cover forestry
management. Teagasc Forestry Development
Department, Athenry, County Galway, Ireland.
Teagasc (2021) Woodland Improvement Scheme
– Continuous Cover Forestry. Teagasc Forestry
Development Department. Available at: https://
www.teagasc.ie/crops/forestry/grants/management-
grants/wis---continuous-cover-forestry/ [Accessed:
1 July 2021]
Vitková, L, and Ní Dhubháin, Á (2013)
Transformation to continuous cover forestry: a review.
Irish Forestry 70(1/2): 119–140.
Wilson, ER, O’Tuama, P and Spazzi, J (2020)
Continuous Cover Forestry in Ireland: update
on recent developments and initiatives. CCFG
Newsletter 41 (Winter 2020): 7, 1–7.
Wilson, ER, Short, I, Ní Dhubháin, Á and Purser,
P (2018) Continuous cover forestry: the rise of
transformational silviculture. Forestry Journal 288
(August 2018): 38–40.
Wilson, ER, Wirz, R, and Byrne, L (2021) Continuous
cover forestry at Dunranhill Forest, County Wicklow,
Ireland. CCFG Newsletter 41 (Winter 2021): 4,1–8.
... However, recent studies [45][46][47] suggest that such depletions in wildlife that were evident when these stands were first established are changing much more rapidly than thought possible. Allied to that, new ways of managing them [48] along with expected climate change will, in the long term, have significant effects on both their diversity and (perhaps surprisingly) on their susceptibility to infection and colonisation by H. annosum. Set against this uncertain backdrop, it is instructive to consider what might happen when these relatively young plantations mature as stable ecosystems. ...
Article
Full-text available
The formulation of a Finnish isolate of the saprotrophic wood-rotting fungus Phlebiopsis gigantea into the biocontrol agent (BCA) Rotstop, which is used to prevent infection of Norway spruce stumps by aerial basidiospores of H. annosum, has led to its application to more than 200,000 ha of forest in Scandinavia and North Europe. The success of this treatment opens the possibility of introducing the Rotstop strain into Britain for use on Sitka spruce stumps, which at present (2022) are lacking adequate prophylactic treatment. However, Rotstop is probably non-native to Britain and to North America (the ancestral home of this spruce), and we do not know if this xylem-decaying BCA can invade standing trees. In this paper, we describe a trial into this issue conducted for the U.K. Forestry Commission in Denmark, in a country where both Rotstop and Sitka spruce have been naturalised. It was preliminary to further stump treatment trials, and is relevant to long-term issues surrounding stump treatment in Britain. Inoculations into 44-year-old standing Sitka spruce with 20 mm wooden Scots pine plugs pre-colonised with Rotstop resulted in decay of the S1, S2, S3 and middle lamellae of sapwood above and below the wounds after 11–18 months. In contrast, infection of sapwood occurred in only one of 39 wounds on the same trees challenged with oidial spore inoculants adpressed to undamaged xylem sapwood during the same period. While the results suggest that release of Rotstop into the productive stands of Sitka spruce in Britain would be unlikely to cause long-term commercial losses to wounded trees, the work highlights issues relating to the assessment of risk associated with the introduction of non-native BCAs within the forest environment.
Article
Full-text available
This article provides an overview of the process of transformation of plantations to continuous cover forestry, with an emphasis on conditions in Britain and Ireland.
Article
Full-text available
Continuous cover forestry (CCF) is an approach to forest management that is gaining increasing attention. Although not a new concept, a number of developments have prompted a renewed consideration of this approach. These have centred on societal concerns about the negative impacts of clearfelling as well as broader societal expectations of multipurpose management of forests. With renewed interest in CCF, the process of transforming even-aged stands that are currently managed under the clear-cut system to CCF has begun in a number of countries. The objective of this paper is to present a review of the scientific literature on transformation to CCF. The review is organised according to a series of questions that address the issue of transformation; i.e. where and when is it appropriate to consider transformation; how long does the transformation process take; and what are the drivers to transformation. The review concludes with a brief overview of existing long-term transformation trials in the UK. The review of the literature identified that there was a limited number of papers on the topic of transformation and most of these emanated from the UK and Central Europe. For this reason the review was expanded to include literature on the starting point and end result of transformation which is typically (although not exclusively) an even-aged (regular) structure and an uneven-aged (irregular) structure respectively. The most common themes in the transformation literature concerned the structure of stands being transformed and the initial stages of the transformation process.
Article
The proposed transformation of substantial areas of even-aged plantation forests in Britain to irregular structures ('continuous cover forestry') has raised concerns about the likely wind stability of irregular stands. A review of the literature suggests that the major difference between irregular and regular stands is the lower (i.e. more stable) height : diameter ratio associated with the dominant trees in the former. This appears to be a consequence of the greater wind loading that these dominant trees have to withstand. Wind tunnel studies show no difference in wind profile within or above the two types of canopy. There have been few comparative root investigations in the two types of stand and no differences in rooting depth have been reported, although changes in root architecture could be anticipated as a result of greater wind loading. The implications of these findings upon windthrow risk in regular and irregular Sitka spruce stands has been explored using the Forest GALES wind risk model on sites of different wind exposure. The results suggest no difference in wind risk on sheltered sites. On sites of moderate exposure, an irregular stand at close to 'steady state' conditions could be more wind stable than a conventionally thinned regular stand. However, this advantage disappears with increasing exposure. The conclusion is that the promotion of irregular stands may provide structures with more stable characteristics, but these cannot be considered in isolation from the prevailing wind climate and the local site type.
Article
The aim of this study was to investigate the effect of the overstorey, as characterised by basal area, on seedling density and growth of advanced regeneration in two irregularly thinned stands of Sitka spruce (Picea sitchensis (Bong.) Carr.) and to investigate whether any relationships found were affected by the method in which basal area was determined. Surveys were carried out in two contrasting Sitka spruce plantations in which the age and height growth (total and current year’s) of advance regeneration was measured and basal area of the crop trees was determined using different methods, including point sampling with a range of basal area factors. The density of young (up to 4-year-old) regeneration was found to be positively correlated with overstorey basal area, with the strongest significant relationship, albeit weak (r2=0.18, P<0.01) found when basal area was determined using point sampling with a basal area factor of 7.5 (metric). Growth of natural regeneration, as determined by total height, leader length and leader/lateral ratio, was found to be negatively correlated with overstorey basal area. The strength of these relationships varied according to how basal area was determined and the significance of this is discussed. In the stand with older regeneration the basal area of the overstorey above those plots where natural regeneration was in check was significantly (P<0.001) higher than where natural regeneration was growing well. It would appear that in order to encourage growth of the advance regeneration, the stand should be kept at a basal area of 30 m2 ha−1 or less. This is less than the value (38 m2 ha−1) for a fully stocked stand [Edwards, P.N., Christie, J.M., 1981. Yield models for forest management. Forestry Commission Booklet 48, HMSO].
Article
There are about 1.5 Mha of conifer high forest in Great Britain composed almost entirely of even-aged plantations of non-native species established since 1900. Recent changes in forest policy require managers to introduce alternative silvicultural systems to clear-felling into windfirm conifer plantations to provide greater structural diversity and so enhance aesthetic, conservation and environmental benefits. There are around 500–750 kha of British forests established on sites which are sufficiently windfirm to be affected by this requirement but only 10–20 kha that are being managed under an appropriate silvicultural system. Expanding the area in the latter category will confront managers and researchers with major ecological, silvicultural and practical challenges.
Woodland Improvement Scheme (Element 2) -Continuous Cover Forestry. DAFM, Dublin. Department of Agriculture, Food and the Marine
  • A D Cameron
Cameron, AD (2020) Transforming even-aged spruce stands into species-diverse irregular forests. Scottish Forestry 74(2): 21-29. Department of Agriculture, Food and the Marine (2019). Woodland Improvement Scheme (Element 2) -Continuous Cover Forestry. DAFM, Dublin. Department of Agriculture, Food and the Marine (2020) Forest Statistics Ireland 2020. DAFM, Johnstown Castle Estate, Co. Wexford.
The practice of thinning forest crops
  • N Farrelly
Farrelly, N (2012) The practice of thinning forest crops. Forestry and Energy Review 2(1): 28-30.
Operational Guidance Booklet 7: Managing Continuous Cover Forests. Forestry Commission
  • G Kerr
Kerr, G (2008) Operational Guidance Booklet 7: Managing Continuous Cover Forests. Forestry Commission, Edinburgh.
M (2021) Spruce, soils and CCF
  • Price
Price, M (2021) Spruce, soils and CCF. CCFG Newsletter 44 (Summer 2021): 3, 1-9.
Teagasc (2021) Woodland Improvement Scheme -Continuous Cover Forestry. Teagasc Forestry Development Department
  • Pro Silva Europe
Pro Silva Europe (2012) Pro Silva Principles. Pro Silva Europe: the Association of European Foresters Practising Management which follows Natural Processes. Barr, France. Available at: https://www. prosilva.org/close-to-nature-forestry/pro-silvaprinciples/ [Accessed 13 Oct 2021] Teagasc (2016) Continuous cover forestry management. Teagasc Forestry Development Department, Athenry, County Galway, Ireland. Teagasc (2021) Woodland Improvement Scheme -Continuous Cover Forestry. Teagasc Forestry Development Department. Available at: https:// www.teagasc.ie/crops/forestry/grants/managementgrants/wis---continuous-cover-forestry/ [Accessed: 1 July 2021]