Guidance on dealing with the changing distribution of tree species

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Guidance on dealing with the changing distribution of tree species
Natural England Technical Information Note TIN053

Guidance on dealing with the
changing distribution of tree species
Native tree species are considered to be of higher value than non-native species for
nature conservation because they are a link to the original natural conditions and are
more likely to create and support the conditions needed by other elements of the
natural woodland system. However, the definition of what should be considered
native is the subject of debate. This note explores the issues and recommends a
flexible approach to dealing with non-native species that are native on the near
continent and which may naturalise in England. This approach should help reduce
unnecessary conflicts in woods where there are other objectives, for example
landscape, recreation, historic or wood production, for which the distinction between
native and non-native species is less important.

Background                                              In previous inter-glacial periods a wider range of
From a nature conservation point of view a high         tree and shrub species were present in the
priority is given to maintaining the native trees       British Isles.
and shrubs in our woods, because they provide
a link to original natural conditions and are more      As a consequence of expected climate change
likely to create or support conditions needed by        the distribution of tree species will alter in the
other woodland species in England. For example          future. It is unclear precisely what these changes
in the generic guidance on setting conservation         will be. However, Natural England is
objectives for woodland Sites of Special                encouraging habitat networks and increased
Scientific Interest the target is predominantly         landscape permeability. We are therefore
95% native tree and shrubs, although this can           encouraging species to move between sites.
be varied for particular sites. The same                This could include spread to areas where they
approach is generally applied to other sites of         do not currently occur (ie are not currently locally
high nature conservation value. However, this           native), and this will lead to changes in the
may lead to potential management conflicts with         woods into which they spread. Assisted
visual, cultural, wood-production or historical         migration might also be considered for some
objectives, where the distinction between native        non-mobile species on account of the rate and
and non-native species is often of lesser or no         magnitude of predicted climate change. At the
importance.                                             same time there may be losses of species or
                                                        reduction in their abundance in other regions.
How native is defined depends on what
geographic boundaries and what time periods             Changes in species distribution are seen as part
are considered. Beech is native to Great Britain.       of the process of the nature conservation
At a finer scale it is not native to Scotland, but is   adaptation to climate change. It therefore
to England and Wales. It is native to southern          becomes illogical to automatically rule out the
but not the extreme west of England, to south-          spread of species that are not currently native,
east but not to northern Wales. Similarly Scots         but which do occur on the near continent. Many
pine is native to Great Britain, but there are no       of these have already been introduced into
recent native populations in England or Wales.          gardens and plantations and have
                                                        naturalised to varying degrees.

First edition 5 March 2009
www.naturalengland.org.uk
Natural England Technical Information Note TIN053

Guidance on dealing with the changing distribution of
tree species

While such naturalised stands have almost             may increase the potential richness of the
certainly originated from planted individuals it is   woodland. Alternatively their presence can be
impossible to be sure that sycamore could not         part of the evolution of the site towards a future-
have spread naturally into southern England           natural/future cultural state. Any action taken to
from northern France in the last millennium, for      remove them may create damage or disturbance
example, through seed blown on an exceptional         to the site.
south-westerly gale.
                                                      There is a balance to be struck between more-
Thus, while in most cases it is reasonably clear      or-less intensive intervention to remove the
what is native in any particular area, there are      species and the future losses or gains from
some species whose status is less clear-cut, for      leaving them alone. The same arguments apply
example because:                                      to the treatment of native species whose
                                                      abundance is changing significantly (eg ash) and
 They are very long-established introductions        which have the capacity to alter the character of
  that have naturalised at least at some sites eg     a woodland (eg holly).
  sweet chestnut in Kent.
 The limits of their past native distribution are    The approach set out below is based on
  debateable (beech in the north).                    three elements:
 The species was present in an area but has          1 The nature conservation value of the site
  been absent for many centuries (Scots pine in
  northern England).                                  Management of colonising or spreading species
                                                      should have a higher priority:
 The distribution/range of a species is changing
  or expected to change substantially as a
                                                       In sites notified for a particular woodland type
  consequence of climate change (beech).
                                                        rather than in non-designated sites.
 The current populations are clearly planted or
                                                       In semi-natural woods rather than in
  are derived from plantations in the last 200
                                                        plantations.
  years.
                                                       In ancient woodland rather than in recent
These issues are discussed in more detail for           woodland.
particular species in the section, The status and      Where there is no particular cultural, social or
distribution of selected species in England.            historical value attached to the colonising
                                                        species at that site.
Debate or ambiguity on the status of a species in
an area can lead to inconsistency in the advice       2 The degree to which a particular species
that staff give on how to treat these species.        changes the nature of the site
                                                      Determined by the tree characteristics, rates of
Much effort could be spent on assessing the           regeneration and other factors, for example:
precise status of these species without
necessarily coming to a consensus, because the         Replacement of one dense-shading species by
evidence may be missing or ambiguous. It may            another will have less of an impact than where
therefore be more productive to assess such             the new species casts much more shade than
species primarily in terms of the impact that they      the species it replaces.
are having on the particular site in question in       Conifer replacing conifer is likely to cause less
relation to the nature conservation objectives          change in shade than conifer replacing
(whether formal or informal) for that site.             broadleaf.
                                                       On any particular site a species that
A site-specific framework for dealing with
                                                        regenerates freely is more significant, because
spreading or introduced tree species                    of potential future impacts, than one that is
Tree species whose ranges are increasing will           unlikely to regenerate.
alter the composition of the sites that they
colonise to varying degrees. In some cases they
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Natural England Technical Information Note TIN053

Guidance on dealing with the changing distribution of
tree species

 Does the species replace another as host for         Where there are other major seed sources in
 a rare or threatened species? (For example old         surroundings such that ongoing work would be
 sycamore trees may be hosts for lichens                needed to prevent further regeneration.
 previously found on elm).                             In minimum intervention stands.
3 Resources                                           Presumption towards management of a
The ease and cost of control needs to be              species in a particular site:
proportionate to the likely impact or threat:         Where the stand being invaded is of high
                                                      conservation value, with species or
 Management before the species has                   assemblages that would be impacted by a
  significantly altered a site is a higher priority   change of species and:
  than where the species is already long-
  established and changes to the woodland              The new species is present in small amounts,
  assemblage have taken place.                          which could be eliminated readily and without
 One-off operations, or management that is part        causing significant damage.
  of work that will be taking place anyway, are        The new species is present in amounts that
  more justifiable than those where extensive           can be eliminated as part of ongoing
  and on-going work will be needed specifically         management that would be undertaken
  to manage the new species.                            anyway.
                                                       Where there are largely young stems or young
None of the above should be taken as absolute           to mature stems showing little regeneration.
presumptions for or against management of a            Where there is no significant seed source in
particular species and most are consistent with         surroundings.
what is already accepted practice in some areas.
For example, it is similar to the approach
                                                       In actively managed sites.
adopted towards sycamore in the LIFE Ravine           The result will be three types of site:
Project Management Handbook.
                                                       Sites where the aim is to maintain the past
Decisions at a site level should therefore be           native tree and shrub composition as closely
along the following lines                               as possible.
                                                       Sites where a change of species is accepted
Presumption towards acceptance of a                     alongside conservation of the main features of
species in a particular site:                           interest.
 Where the impact on characteristic species or        Sites which are managed or allowed to
  assemblages has already happened or is not            develop towards a new state which may
  likely to be significant.                             contain different suites of species.
 Where mature or veteran trees of the new
  species are present, especially if they are part    The status and distribution of selected
  of uneven age structured population.                species in England
 Where the species is already widespread in          This section explores how the approach above
  the stand or wood, having largely replaced the      might apply to particular species in different
  former type, and is showing good                    parts of England.
  regeneration.
 Where high level of management (particularly        Beech in northern and western England
  ongoing management) would be needed to              Past distribution
  remove the species, especially if this would be      The species first appeared in Britain fairly early
  the main reason for having to carry out the           in the post-glacial period, but the records
  management.                                           remain sparse for several thousand years. It
 Where the management to control the species           appears to have not been very competitive in
  would cause significant other disturbance.

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Guidance on dealing with the changing distribution of
tree species

  the wildwood, possibly because Britain is          its range and abundance declines in southern
  towards the edge of its range.                     Europe.
 The main spread and increase in abundance
  occurred around the Neolithic period and may      Consequences of increased beech in
  have been facilitated by human disturbance        woodland
  and clearance of the wildwood. Even so it may      Beech regenerates well under higher levels of
  never have reached the climatic limits of its       shade than oak or ash and has the potential to
  potential range.                                    become the canopy that is dominant across a
 As a major forest type, beech seems to have         wide range of soil types. The production of
  been limited to southern Britain and there is       beech mast (seed) is irregular which will slow
  evidence for continuity of beech woodland           spread in woods. However, it may become
  presence through to the present in these            more common if summers become warmer.
  regions. Beech woodland conservation is             There is evidence of a high frequency of mast
  therefore focussed on these regions, see maps       years in southern England over the past ten
  of beech woodland types in Rodwell (1991),          years.
  Peterken (1980), Rackham (2003).                   The seed tends not to spread widely from
 There are outlier pollen records further north      parent trees so often there will be clusters of
  and west in England, some of which may have         beech and then relatively large areas with little
  represented local populations, rather than          regeneration. Parent trees outside the site are
  long-distance pollen transport, but with no         therefore less of a concern in assessing impact
  evidence for continuity of beech woodland or        than for some other species.
  veteran trees.                                     Regeneration is limited by grazing (as is that of
 The oldest trees tend to be in designed parks       other species).
  or other situations where the trees seem likely    Beech casts one of the heaviest shades of
  to have been planted.                               broadleaved species. Particularly on acid sites
 Veteran beech trees seldom survive more than        the ground flora and shrub layer (other than
  350 years, so survival of individuals from the      holly) can be greatly reduced in cover and
  early medieval period is unlikely.                  richness.
                                                     There is some overlap between the ground
Future distribution                                   flora and shrub layer found under beech and
 Beech has been widely planted in north and          that found under oak or ash, but but under
  west England (and also in Wales and                 beech there is reduced cover and frequency
  Scotland) over the last 300 years and has           (Rodwell 1991).
  locally naturalised.                               The assemblages that do develop under beech
 Given that beech may not have reached its           beyond its current native range are not
  climatic limit before humans disrupted the          dissimilar (allowing for climatic and soil
  landscape, the natural spread or re-                variations) to those that occur in southern
  colonisation (if the outlier pollen records did     Britain, but some of the rarer beech woodland
  represent past populations) of northern and         specialists may be missing (Wesche and
  western England could still be happening,           others, 2007).
  albeit masked by the effects of planting.          Beech can develop a rich deadwood
 Changing climatic conditions may put beech          invertebrate fauna and in some sites in
  populations in southern England under               northern England (Dunham Massey,
  increased stress and it may not be possible to      Duncombe Park) the veteran beeches are a
  maintain the current levels of beech in some        significant part of the interest.
  sites. Most models suggest that conditions for     Old beech in the north is not particularly rich in
  beech in north-west England will remain             lichens (Francis Rose personal
  favourable or improve. The significance of          communication).
  beech populations in Britain may increase if       Beech woods are considered rich in fungi but
  (as is likely from climate change projections)      there are no known systematic surveys
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Natural England Technical Information Note TIN053

Guidance on dealing with the changing distribution of
tree species

 comparing the richness of northern and                recently it has been a significant part of woods
 southern beech woods.                                 or as trees in the landscape.

Preliminary assessment                                Future distribution
 Long-term dominance by beech is not                  Sycamore has been widely planted particularly
  inevitable in all sites, so concerns about beech      in north and west England (and in Wales and
  takeover should be based on the actual                Scotland) over the last 300 years and has
  regeneration occurring on the site.                   locally naturalised. It is a characteristic feature
 The impact of increasing beech dominance will         of Pennine farmsteads and is likely to remain a
  be most significant where there are rich and          significant part of future landscapes.
  important ground layer communities, whether          It regenerates freely, particularly on moist
  of bryophytes on acid soils or higher plants on       neutral to base-rich soils; it is more likely to
  base rich soils.                                      spread on such soils, rather than on acid soils.
 Veteran beech should be maintained for their         It is relatively shade-tolerant; hence it is
  contribution to the deadwood communities.             capable of spreading within existing woods.
 If the distribution and abundance of beech is         Some studies suggest that regeneration tends
  responding to climate change, accepting more          to follow soil disturbance (work by Neil Riddle
  beech in woods in the north and west is               2005, summarised in Ravine Woodland
  anticipating the process of climate change            Management Handbook).
  adaptation. The changes in ground flora and          Trees seed regularly and spread quite well,
  other woodland components are a further               again encouraging spread. Some studies
  consequence of this.                                  suggest possible alternation of regeneration
 The cultural value of beech varies. On some           with ash (Waters and Savill 1991).
  sites it has been an important contribution to       Regeneration is limited by grazing (as is that of
  the cultural landscape (eg of designed parks)         other species) .
  in other cases it may be diluting the traditional    The growth of sycamore may be reduced
  landscape eg oak coppice landscape.                   under future droughts compared to ash, which
                                                        may encourage co-existence with ash and oak
Sycamore                                                in some sites (Morecroft and others 2008).
Past distribution
 The species is first definitely recorded in         Consequences of increased sycamore in
  Britain in the early medieval period (Jones         woodland
  1945). There are claims for earlier occurrences      Sycamore regeneration tends to develop first
  (Green 2005), but the evidence for this is            into a dense pole-stand understorey and then
  ambiguous and there is a difficulty in                into even-aged patches of mature timber with
  separating its pollen from that of field maple.       little understorey. Existing shrub layers may be
 There are some early archaeological finds.            lost through shading.
  However, these are not convincing, for               The ground flora is often rather uniform under
  example the early medieval leaf carving on St         mature sycamore (eg a carpet of Dog’s
  Frideswides tomb (Oxford) could have been             mercury) but this may be more to do with the
  carved by a French mason, or a local mason            tendency for these to be mature high forest
  who had seen the tree in France. A fourth             stands, rather than the effect of sycamore
  century Roman bucket of sycamore occurs at            shade per se. Ground flora richness may be
  a site which also contains other finds including      maintained in other situations (Taylor 1985;
  silver fir and quern stones from Germany.             Riddle 2005).
 If sycamore did occur pre-Medieval times it          On the continent sycamore is a characteristic
  would appear not to have been abundant                component of the Tilio-Acerion Habitat
  enough for anyone to notice, compared to              Directive type. In some British sites it may
  more regular records from the seventeenth             occupy situations where either lime or elm
  century onward. It is only comparatively              would previously have been dominant.
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Guidance on dealing with the changing distribution of
tree species

  However, it is unlikely to out-compete either       Sweet chestnut
  species where these are healthy.                    Past distribution
 Old sycamore can have a rich lichen flora            Sweet chestnut was probably native originally
  distinct from that on oak on similar sites.           to the Balkans and parts of south-central
 Veteran sycamore can provide valuable dead-           Europe. However, its value as a food source
  wood habitat.                                         as well as for its wood meant that it has been
 Its reputation as poor for invertebrates is           widely spread throughout the rest of Europe,
  based on a particular study of specialist             not least by the Romans.
  faunas. It is richer than some native species        Rackham (2003) discusses the early
  and can carry a high biomass of invertebrates,        controversy over whether or not it was native
  which may be more significant if food for birds       and the eventual conclusion was that it was a
  and mammals is a consideration.                       Roman introduction. However, he treats it as
                                                        an honorary native at least on some sites,
Preliminary assessment                                  particularly in Kent and Essex and locally
 Long-term dominance by sycamore is not                elsewhere in the south-east and the Welsh
  inevitable, so the actual regeneration occurring      borders. The earliest localised record is in the
  on the site should be assessed. Management            reign of Henry II in the Forest of Dean.
  to remove existing trees may create the              Its value, particularly as coppice, led to it being
  disturbance that favours increased sycamore           widely planted throughout the lowlands. It was
  regeneration.                                         also managed as pollards and as ornamental
 The potential impact will be most significant         trees in parks.
  where there are rich and important ground
  layer communities of higher plants on base          Future distribution
  rich soils and where it is replacing ash, rather     Although widely distributed the woods where it
  than former elm sites.                                is abundant are relatively rare. In most
 Its reputation as having a low associated fauna       instances the trees or stools have been
  has been challenged.                                  planted. Natural regeneration and spread tend
 Veteran trees should be maintained for their          to be limited, not least because the nut crop is
  potential lichen and deadwood interest.               not very good in England. With increased
 On the continent sycamore is frequently               summer temperatures nut set and natural
  associated with relatively cool, moist                regeneration may improve.
  situations, such as gorges. Some of these may        The recent advance of chestnut blight
  become under stress under future climate              Cryphonectria parasitica in northern Europe
  scenarios, with an expected range shift to the        suggests strongly that it will extend its range
  north and west. Allowing some spread in               into Britain. If it does the impact could be to
  British woodland is compatible with the               reduce the dominance of chestnut in woodland
  process of climate change adaptation.                 in southern England.
 It has the potential to spread from parent trees     Rackham considers it predominantly a tree of
  in the neighbourhood. However, provided there         acid soils, typically on sandy or silty soils, but
  is little ground disturbance the significance of      Buckley and Howells (2004) suggest that it can
  such spread may be limited. By itself this is not     occur on a wider range of conditions.
  a reason for not managing the species where it
  is considered to be undesirable.                    Consequences of increased sweet chestnut
 The cultural value of sycamore varies: in many      in woodland
  non-woodland situations it is an important part      Chestnut stands are often poor in vascular
  of the local landscape - particularly as non-         plants, partly because of the nature of the soils
  woodland trees in northern England. Also              on which they occur, but also because of the
  sycamore coppices were associated with the            density of its shade, frequently compounded
  bobbin mills of the north-west.                       by its growth as well-stocked coppice. In
                                                        addition its litter, composed of large, slow to
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Guidance on dealing with the changing distribution of
tree species

  decay leaves, may suppress some smaller              provide a better economic crop and the
  ground flora species.                                coppice is more likely to be worked. The aim
 The shrub layer, other than coppice regrowth,        should be to achieve structural diversity
  also tends to be poor, again because of the          through the coppice system.
  competitive nature of chestnut.                     In other stands management should allow or
 The value of chestnut coppice means that it is       encourage the gradual diversification of the
  more likely than many other species still to be      composition through spread of other tree
  worked, and there are benefits from the              species (usually oak and birch).
  diverse structures that this creates.
 There appear to be few species strongly            Holm oak Quercus ilex
  associated with the tree.                          Past distribution
 Veteran chestnuts can provide valuable dead-        This is primarily a Mediterranean species,
  wood habitat and are a significant component         although it occurs into central France.
  of the interest at sites such as Croft Castle.      It has been cultivated in Britain since the 16th
                                                       century, widely planted in the 18th century and
Preliminary assessment                                 was recorded in the wild in 1862 (Preston and
 To date chestnut has not been viewed as a            others 2002).
  particularly invasive species in the way that
  sycamore or beech in the north have been. In       Future distribution
  future this may change, although increased          It currently occurs through much of southern
  invasiveness might be countered by increased         England and appears to be spreading.
  attack by chestnut blight.                          It is likely to be favoured by climate change.
 Where sweet chestnut becomes dominant the           It seeds prolifically and can regenerate freely
  effects are likely to be reduced ground flora        on appropriate soils.
  abundance under the canopy. However, if it is
  managed as coppice this effect may be off-set      Consequences of increased holm oak in
  by increases in ground flora in the recently cut   woodland
  stands.
                                                      As an evergreen species it changes the
 The woods where it seems most likely to              character of the woodland community in a way
  spread are oak-bramble-bracken (W10) and             that the species discussed previously do not.
  oak-wavy hair-grass (W16) woods. However,            The nearest native equivalents are stands of
  its impact on these communities is likely to be      yew and holly.
  less than its impact in ash (W8) woodland.
                                                      There is very limited information on the
 Locally the species has high cultural value. For     ecology of the species in Britain, but casual
  example it is associated with hop production in      observation at Lyme Regis Undercliff suggests
  Kent and the Welsh borders.                          that the ground flora underneath it is likely to
 Where it is a long-established component of          become dominated by ivy, ferns and a scatter
  the wood (>200 years) there is no particular         of other highly shade-tolerant plants.
  reason not to treat it as a naturalised species,
  particularly in the south-east and Welsh           Preliminary assessment
  borders.                                            It is likely that this species will continue to
 Veteran chestnuts should be maintained for           spread under climate change.
  their dead-wood value.                              Where it does not currently occur, or is present
                                                       as only a few trees, it is probably best, if
Where it has been planted and forms dominant
                                                       practical, to try to keep this species out.
stands two approaches should be considered:
                                                      Controlling or removing it where it is
 If it can be effectively managed as coppice          established is likely to involve major felling.
 there may be a case for maintaining the stand         Gradual thinning out is unlikely to be effective
 largely as chestnut since this is likely to           since it may simply increase the regeneration

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Guidance on dealing with the changing distribution of
tree species

  of the species in the gaps created. Hence             Pine regeneration in woods is likely to be
  where it is already well-established and               limited by its need for relatively open
  regenerating, it may be less disruptive to             conditions and some soil disturbance for
  accept it as a future-natural new woodland             seedlings to establish.
  type.                                                 Hotter summers may favour pine spread on
 Holm oak ecology in Britain should be a priority       some soils where other species can currently
  for future research.                                   out-compete it.
                                                        Increased extreme events could provide more
Scots pine in northern England and on                    large scale disturbances that would favour pine
southern heaths                                          regeneration.
Past distribution                                       Increased fires might favour pine spread.
 Scots pine was widespread across England
  during the early Holocene period. There is           Consequences of increased pine in woods in
  debate as to whether these populations were          England
  the same as, or continuous with, those that           In general pine is not likely to spread much in
  spread in Scotland or whether there were               most existing broadleaved woodland,
  different origins and invasion routes.                 particularly if this is managed by minimum
 Subsequently Scots pine declined in the pollen         intervention, coppicing or as high forest using
  record as broadleaved species spread.                  low intervention methods.
  However, from comparisons with its behaviour          Where it occurs as small stands or as a
  elsewhere in Europe pine may have remained             component of woods on acid soils the ground
  a component of high altitude woodland in               flora is not dissimilar to that under oak and
  England, of woodland on dry acid sands and,            birch stands on those soils.
  probably as scattered trees, on acid bogs.            Some pine-specific associated species do
 Past management, particularly coppicing,               occur in such stands from time to time,
  would act against pine as it tends not to regrow       increasing local diversity.
  well after cutting.                                   Oak and birch are able to establish in
 There appears to be little, if any, direct             association with pine, so it is unlikely that pure
  evidence for survival of native pinewoods in           pine stands will remain pure in the long-term
  Britain into the historic period, except in the        without regular disturbance.
  Scottish Highlands. There is apparently a
  medieval record for firs in the Lake District that   Preliminary assessment
  might refer to pine, but these do not seem to         This is a different situation to those considered
  have survived thereafter.                              previously in that it is re-introducing a species
 The occasional occurrence of old native-               south of where it currently survives as a native
  looking pines in northern England and a                species in Britain. The whole of England is
  distinct saproxylic pine beetle assemblage in          within its climatic range and some sites may
  East Anglia and some Surrey heaths have                become more suitable for Scots pine under
  been interpreted as possible continuity of             hotter summers.
  scattered trees, if not woodland, through             If we accept there were woods with a native
  historic times in these areas (Roger Key               pine component (even if not the dominant tree)
  personal communication).                               on some soils and situations in the past then it
                                                         is not unreasonable to consider it as a
Future distribution                                      component of new woodland in such areas
 It has long been planted widely throughout             (although not necessarily pure stands).
  Britain, both within its native Scottish range        Generally pine should not be introduced into
  and elsewhere. Hence it is now almost                  ancient or other long-established woods where
  ubiquitous in England.                                 it does not occur, but there is no need to be
 It spreads naturally very well from planted            assiduous in cutting out natural regeneration if
  stands, particularly on heathy soils.                  the soil and site appear appropriate.
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Guidance on dealing with the changing distribution of
tree species

 In northern England, if new pine stands are       North American species most widely spread
  being created there is a case for considering     through the countryside are the dense shading
  using a mixture of provenances from the native    conifers which change the character of our
  pinewoods (albeit there will be some risk to      woods and wildlife significantly. The broad-
  this from moving them south, against the          leaved tree Robinia also has the potential to
  climate change trend).                            spread more than it has to date under climate
 In the south no particular provenance selection   change projections.
  is recommended from a nature conservation
  point of view.                                    Rhododendron, snowberry, laurel
                                                    These species spread to form dense thickets
Species this approach does not apply to!            replacing existing understories, shading out
The following are examples only of species          ground flora.
where the presumption should remain that,
                                                    Eucalypts
where nature conservation is important, they
should be removed if they occupy a significant      These produce a very different type of woodland
area of the wood or are spreading.                  structure and composition (albeit there is very
                                                    limited data from UK conditions) and are
Norway spruce, European larch and silver fir        taxonomically very different to British or
These species do occur on the continent but at      continental species.
present the arguments against them are:
                                                    Further information
 They are not particularly suited to the current   Natural England Technical Information Notes are
  or future climates in Britain.                    available to download from the Natural England
 They do not appear to have naturalised            website: www.naturalengland.org.uk . Other
  regularly, despite several hundred years of       notes on woodland include:
  being planted in woods.
                                                     TIN001 - The historic environment and
 They change the character of the woods
                                                      woodland management
  significantly, through the nature of the shade
  that they cast and their litter type.             For information on other Natural England
                                                    publications contact the Natural England Enquiry
Turkey oak
                                                    Service on 0845 600 3078 or e-mail
This species is alternate host for the knopper      enquiries@naturalengland.org.uk.
gall which attacks the acorns of native oaks.
Hence it should not be encouraged.                  Author
                                                    This note was developed by Keith Kirby, Natural
North American species
                                                    England.
The basic assumption behind this approach is
that our woods are part of a broader continental
continuum and hence species on the continent
might spread in time to them anyway. This does
not apply to North American species. In addition

References
BUCKLEY, G.P. and HOWELLS, R. 2004. The ecological impact of sweet chestnut coppice
silviculture on former ancient, broadleaved woodland sites in south-east England. English Nature
Research Report, Peterborough.

GODWIN, H. 1975 The history of the British flora. Cambridge University Press, Cambridge.

GREEN T. 2005 Is there a case for the Celtic maple or the Scots plane? British Wildlife, 16, 184-188.

                                                                                              Page 9
Natural England Technical Information Note TIN053

Guidance on dealing with the changing distribution of
tree species

KENNEDY, C.E.J. and SOUTHWOOD, T.R.E. 1984. The number of species associated with British
trees - a re-analysis. Journal of Animal Ecology 53, 455-478.

LINHART Y.B. and WHELAN R.J. 1980. Woodland regeneration in relation to grazing and fencing in
Coed Gorswen, North Wales. Journal of Applied Ecology, 17, 827-840.

MORECROFT M.D., STOKES V.J., TAYLOR M.E. and MORRISON J.I.L. 2008. Effects of climate
and management history on the distribution and growth of sycamore Acer pseudoplatanus L. in a
southern British woodland in comparison to native competitors. Forestry, 81, 59-74.

PETERKEN, G.F. 1980 Woodland conservation and management. Chapman and Hall, London.

PRESTON C.D., PEARMAN, D.A., and DINES, T.D. 2002. New atlas of the British and Irish flora.
Oxford University Press, Oxford.

RACKHAM, O. 2003. Ancient woodland. Second edition, Castlepoint Press, Dalbeattie.

Ravine Woodland Management Handbook 2007. Produced by Ravine WoodLIFE Project.

RODWELL, J. 1991. British plant communities. 1 woodland and scrub. Cambridge University Press,
Cambridge.

TAYLOR, N.W. 1995. The sycamore Acer pseudoplatanus in Britain - its natural history and value to
wildlife. Discussion papers in conservation 42, University College, London.

WATERS T.L. and SAVILL P.S. 1991. Ash and sycamore regeneration and the phenomenon of their
alternation. Forestry, 65 (4), 417-433.

WESCHE, S., KIRBY, K.J. & GHAZOUL, J. 2006. Plant assemblages in British beech woodlands
within and beyond native range: Implications of future climate change for their conservation, Forest
Ecology and Management 236, 385-392.

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