ccfg / bes seminar at rushmore, dorset in april 2017 ... · ccfg / bes seminar at rushmore, dorset...
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Spring 2018Continuous Cover Forestry Group
CCFG / BES Seminar at Rushmore, Dorset in April 2017
Biodiversity effects of ‘irregular’ silviculture in native woodland
Continuous Cover Forestry Group 4.1 Spring 2015
Spring 2015
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On 5th and 6th of April a group of about 70 enthused and inquisitive people met for this two day
seminar in the splendid surroundings of the Rushmore estate, straddling the Dorset/Wiltshire
border. The event started with a presentation about the use of CCF at Rushmore followed by a
series of talks describing new and informative research into the effects of different forms of
irregular silviculture upon biodiversity in native woodlands. Copies of all the presentations can be
found on the CCFG website at http://www.ccfg.org.uk/category/events/2017/
Andy Poore, consultant forester for the Rushmore Estate, provided an overview of the history
and management of the woodlands on the estate, based on nearly 30 years of experience with
these woodlands. The 833 hectares of woodland at Rushmore are 69 per cent broadleaved and
26 per cent conifers with avenues and similar making up the remainder. Annual timber
production is about 1900 m3 of softwood and 1100 m3 of hardwood. 434 hectares are designated
as a SSSI, comprised largely of ancient semi-natural broadleaved woodland. He noted that there
had been a long tradition of coppice management in these woodlands, but this had largely
ceased by the 1970s. For management purposes the woods had been divided into a number of
working circles – those which were the focus of the seminar were; semi-natural broadleaved high
forest managed by CCF, closed stands (mostly managed under minimum intervention) and
coppice-with–standards (either hazel or birch dominated). The key message from this session
was the complexity of stand types across the estate. They did not adhere to standard yield
models. Instead, successful management resulted from highly specific silvicultural interventions.
Management has been, first and foremost, economically driven. Any benefits to biodiversity are
a result of forest management that is all the while, profitable. Underpinning this approach was a
stand monitoring system adopted from the AFI (Association Futaie Irregulaire), which provided
detailed real-time data regarding the performance of individual stands.
Participants were then given a couple of presentations outlining interim findings from the
ongoing ‘Rushmore Biodiversity Research Project’, which was a partnership between the Estate,
Dorset County Council, Dorset Environmental Records Centre and Manchester Metropolitan
University. This five year project aims to uncover the relationships between the different forest
structures and biodiversity in these semi-natural woodlands with a particular aim of seeing if a
forest managed using irregular silviculture can provide favourable conditions for general
woodland biodiversity as well as protecting species of particular environmental concern.
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Continuous Cover Forestry Group 4.1 Spring 2015
Continuous Cover Forestry Group Spring 2015
www.ccfg.org.uk
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Danny Alder (Manchester Metropolitan University) presented his findings from research into the
habitat associations of particular woodland birds and their interactions with the matrix of stand
types at different periods in the year. The results showed a strong correlation between stands of
lower stem densities having a greater array of different species and larger populations of these
species. However this was not the case for every species; with a minority displaying a preference
for denser and closed canopy stands, particularly at certain times of year. Notably, greater
spotted woodpeckers would move into higher density stands in summer in response to increased
food availability. A similar effect was also seen in the research into the abundance of bat
populations in different stand types. The irregular high forest stands contained a significantly
higher average abundance of most bat species, although some species showed a marked
preference for both the minimum intervention and coppiced stands. Dr. Phil Sterling (Dorset
County Council) had examined moth populations within the different stand types. The
abundance of rarer woodland moths was higher in the irregular stands than in either the coppice
woodlands or those with minimum intervention. Numbers of leaf mining moths were also higher
in the irregular stands than in the coppice woods. He concluded by saying that these initial
results suggested that irregular forest management was at least as good as coppice or minimum
intervention in conserving moth biodiversity.
The indoor session was closed by Dr. Rob Fuller (BTO and the University of East Anglia) who
reviewed current understanding of the relationship between forest structure and biodiversity,
with particular emphasis upon broadleaved woodland. He outlined how management actions
(such as the choice of silvicultural system) will influence the structure of the woodland habitat
and consequently the functional resources available for woodland biodiversity. There was general
agreement that the two stages of most importance for woodland bird populations were the early
establishment phases and old growth stands with spatially varied structures and substantial
amounts of deadwood. Neither stage tended to be favoured by conventional even-aged
management. Field studies had shown a major decline in vegetation cover over 20 years in
unmanaged broadleaved stands with substantial decreases in some woodland birds, while results
from irregular conifer stands showed higher number of bird species than in regular stands.
Irregular forest management could be valuable in diversifying woodland habitat, particularly if
using group based silvicultural systems, where the groups could provide adequate habitat for bird
species found in the early successional stages. He concluded by stressing the need for using a
range of silvicultural systems to provide habitat diversity at a landscape scale, and noted the
important interaction with the management of deer.
The first afternoon and the second day saw the delegates make the most of the marvelous spring
weather, with numerous stops around the estate to illustrate the relationship between
management practices and their impact upon biodiversity. One stop at Farnham Woods showed,
in particular, the benefit of regular monitoring, such as that provided by the AFI’s stand
monitoring system. This provided a detailed summary of the stand’s composition, structure and
capital value, thus enabling management to make precise and timely harvesting interventions
specific to that stand. The next intervention in two years’ time would focus on removing mostly
mid-diameter ash trees, with the aim of encouraging more oak regeneration. This intervention
would also see the installation of permanent extraction racks; essential for harvesting in irregular
stands, but also a consequential benefit to biodiversity.
Continuous Cover Forestry Group 4.1 Spring 2015
Continuous Cover Forestry Group Spring 2015
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Fig 1: An ash dominated stand undergoing
transformation to full irregularity. The understorey
has been recently removed and extraction racks have
already been marked in blue
Fig 2: Andy Poore explaining the virtues of the AFI
stand monitoring system
The topic of incorporating a means of measuring biodiversity into the stand monitoring
procedure was also discussed. This might be accomplished by monitoring key indicator species
such as leaf miner moths. Although not currently feasible, it is hoped that this may become a
possibility following the completion of the Rushmore biodiversity project. If successful, this could
provide an effective abbreviated measurement of biodiversity within stands, helping to inform
the type of management intervention that might be taken.
Other stops illustrated issues relating to the practicalities of coppice management when markets
for hazel products are limited and those for birch (e.g. hurdles for horse jumps) may be close to
saturation. One aspiration for the Estate is to reduce management dependence upon uncertain
grant support, so the lack of viable coppice markets is a major reason for the interest in greater
use of irregular forest management. In the last two decades, the woodland account has made a
profit every year, and Andy Poore estimated that the rate of return on the irregularly managed
stands was about 1-2 per cent.
Continuous Cover Forestry Group 4.1 Spring 2015
Continuous Cover Forestry Group Spring 2015
www.ccfg.org.uk
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Fig 3: Rushmore, South Chase, coppice
Fig 4: Rushmore - Irregular high forest
with some mature trees retained to
conserve rare lichen species
The stands in the Continuous Cover working circle have fairly open stand structures with basal
areas generally between 10 and 20 m2 ha-1. In places this open structure has resulted in
appreciable bramble colonization which may limit natural regeneration potential although it will
be beneficial for biodiversity.
One possible problem is that a good proportion of the mature oak trees have very low increment
and are not appreciating in value, so that in strict economic terms they should be felled in the
near future. However, this could risk losing the regeneration niche to competitive vegetation, so
integration of management of the understorey (e.g. hazel) with that of the overstorey would be
critical to successful implementation of irregular forestry. The relatively long thinning cycle
(interventions every 10-15 years) should help to allow the understorey to regrow and dominate
the ground vegetation. Careful deer management would obviously be critical in achieving
successful regeneration and areas of cut hazel coppice are fenced to limit browsing impacts.
Fallow, roe and muntjac are all present, and measures have been taken to reduce deer numbers
and results from deer impact transects suggests that browsing pressure is declining.
Ash dieback may have considerable implications because this species has been a substantial
component of the natural regeneration. Some preemptive felling has been undertaken to remove
susceptible trees and other species are being favoured in thinnings or enrichment planting to
reduce the extent of the risk from this disease. Research is also being carried out by scientists at
York University to see if there is any effect of the more open environment found within the stands in
the Continuous Cover working circle that might limit the impact of this fungal pathogen and how
this might be influenced by tree genotype.
4.1 Spring 2015
Continuous Cover Forestry Group 4.1 Spring 2015
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Continuous Cover Forestry Group June 2015
Spring 20182.1
Some key points from the two days included:
• Variety is crucial. In terms of stand size, density, composition and structure. Although the
irregular high forest working circle demonstrated higher levels of biodiversity (for the species
sampled), the continuing presence of managed coppice stands and areas of minimum
intervention would be crucial for some species.
• Stand monitoring is essential in forming educated decisions when attempting to alter the density,
structure or composition of the stand for both economic and environmental objectives.
• It is important to understand how management actions impact the attributes of the stand and in
turn, the functional resources for biodiversity e.g. thinning intensity/frequency affects the height,
volume and density of the canopy which in turn affects the insect biomass and availability of
nesting sites for birds.
• Profitable forestry does not have to result in poor levels of biodiversity, the two can be
complementary.
It was inspiring to see such a variety of delegates attending the seminar- with foresters, ecologists
and conservationists all sharing ideas and opinions on the topics presented. The seminar was highly
informative and reaffirmed my belief that the benefits of CCF are diverse and far reaching. The
delegates were very grateful to the Trustees of the Rushmore Estate for allowing the meeting to
take place, to the British Ecological Society for helping to sponsor the event, to the various speakers,
and particularly to Andy Poore for organizing the event and for leading the field excursion.
Tom Haynes, University of Cumbria
Modifed by Bill Mason of CCFG
Supplemented with additional information provided by Keith Kirby, University of Oxford
Photographs courtesy of Tom Haynes and Bill Mason