TREES

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TREES IN HABITAT AS HABITAT

• Issues, considerations, suggestions

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Contents

• Tree habitats
• Trees as habitat
• Management considerations and options

Marble Hill Park, London
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Aims

• To examine the factors which should inform any
  prescription for tree management
• To suggest outline guidance for determining
  management objectives and implementation

Marble Hill Park, London
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Tree habitats

• Trees grow in different habitats. It is
  important to recognise this as the place where a
  tree is growing will have a major influence on
  its future management. Tree habitats divide into
  two main groupings
• Urban i.e. built-up, developed areas
• Rural areas

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Urban areas - towns and cities

• Highways and transport infrastructure areas
• Housing areas
• Parks and gardens
• Commercial and industrial areas
• Schools
• Settings for historic buildings

Champs Elysee, Arc de Triomphe, Paris, 1944
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Urban areas bring man and tree into closest
conflict (1)

• Safety
• Need for management increases with intensity and
  sensitivity of site use (e.g. childrens
  playgrounds)
• Will increase with age of tree
• Will increase according to past tree management
  (e.g. pollarding)
• Interference with services
• Overhead
• Underground
• Highways - sight-lines, sign clearance, street
  lights

Champs Elysee, Arc de Triomphe, Paris, 2005
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Failed Aesculus hippocastanum
High Wycombe, Buckinghamshire, England
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Failed Aesculus hippocastanum

• Tree growing adjacent to a public car park
• Inspected a few weeks earlier by contractor who
  failed to realise urgency of need for work
• Embedded branch junction failed, damaging car and
  injuring driver
• Tree owner completely at fault

High Wycombe
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Urban areas - conflicts (2)

• Inhospitable growing conditions
• Soils
• Pollution air, water
• Mechanical damage
• Poor management/lack of management
• Management costs
• Difficulties of managing a large and changing
  resource, some of which is not in public control

La Defence, Paris
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Urban areas - conflicts (3)

• Pressure for more space development
• Above and below ground pressures
• One tree may be a habitat in itself, rather than
  forming part of a grouping

Notting Hill, London
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The urban situation

• Managed trees
• High maintenance input
• Multiple problems
• Historic considerations

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Trees in urban areas are often the most highly
prized

• They soften the built environment
• They add relevance to development
• They provide visual links between differing
  landscape types and uses
• They provide a scale to which humans can relate
• They contribute to a sense of place
• They influence local micro-climate

Nottingham, England
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Urban areas - clear conflict

• Highly prized trees
• In areas where they are under pressure
• HOLD THIS THOUGHT!!!!!

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Rural areas tree habitats

• Forests (economic)
• Woodlands (amenity and multi-use)
• Farmland
• Hedgerows
• Transport systems
• Roads
• Rail
• Waterways

Suffolk, England
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Rural areas

• Pressures on trees generally less severe
• Land use for people less intensive
• Environmental conditions usually less degraded
• Trees can form part of a habitat grouping, rather
  than being the sole habitat
• THE INDIVIDUAL TREE MAY BECOME LESS IMPORTANT

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Tree habitats - summary

• Urban areas
• fewer trees, each individually prized for its
  landscape, social and wildlife conservation
  values
• need to maintain trees in a safer condition
• greater potential for conflict
• Rural areas-
• more trees, each less valuable individually
• safety parameters expanded
• value as part of a grouping rather than as
  individuals

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Trees as habitat

• A tree may be regarded as a large volume of
  greenspace held conveniently above head level.
  It has the potential to contain a number of
  varied (and in some cases, rare, habitat types).
• Leaves
• Fruit
• Buds
• Flowers
• New growth
• Bark
• Conducting tissue
• Rooting zone
• Cast detritus
• DEAD WOOD

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Trees as habitat

• Trees have a number of features which make them
  particularly valuable as habitat

• They live to considerable age
• They achieve very large sizes
• They have a large surface area to volume ratio
• They offer a range of differing shelter and food
  sites
• These change

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Trees change..as they age, they provide
different, specialised habitat sites

• Holes in branches
• Cavities,
• Dead wood
• Crevices in bark
• Fungal fruiting bodies
• Water pools
• Sites for ephiphytic plants
• Loose bark
• Cast dead wood
• Sap runs

Photo Roy Finch
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Burnham Beeches, Buckinghamshire, England. Photo
Roy Finch
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Old, apparently dilapidated trees are very
valuable in wildlife terms

• An important feature is the presence of dead or
  dying wood this provides the habitat for some
  very specialised invertbrates which cannot
  survive elsewhere they are called saproxylic
  organisms. Some species of beetle are
  particularly important and are threatened because
  of the absence of dead wood.

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We are now faced with a dilemma (1)

• Man requires that trees are kept
• Safe
• In pleasing aesthetic condition
• That landscape features such as avenues are
  maintained
• That infrastructures work
• That risk of disease insect colonisation is
  minimised
• That everything is TIDY!!!!!

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We are now faced with a dilemma (2)

• Wildlife conservation (biodiversity) and the
  conservation of many threatened species requires
• That we allow things to decay and become
  potentially dangerous
• That we leave untidy detritus
• POSSIBLY, that we CREATE conditions for
  colonisation by organisms
• WE HAVE CONFLICT !!!!!!

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Dangerous branches over house
SE, 2006, photo De Gouret
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Suspect, dead pollard close to railway line (DG)
SE, 2006, photo De Gouret
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Stumps in conifer plantation SE responsible for
infestation of bark beetle in standing crop (DG)
SE, 2006, photo De Gouret
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Creating old trees (1)

• There is a current trend towards creating
  habitat niches in healthy trees which would
  otherwise not be there until they aged. This can
  be done by deliberate injury
• Spiking live trunks
• Deliberate tearing of branches when pruning
• Creating pollards from established trees

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Creating old trees (2)

• This may be justified BUT we must consider the
  situation
• Aesthetics
• Landscape
• Historical implications
• Safety
• Position
• Liability

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Photo DG, 2006
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Creating old trees (3)

• Will the process be effective?
• Will the protected organisms colonise the tree?
• Use of native species
• Is the protected species sufficiently threatened?
• Will the wrong species colonise the tree
• Is there a risk that diseases or pests will
  proliferate?
• Ethics
• is it right to damage a healthy organism?
• Is it right to shorten the life of a tree which
  might give pleasure to future generations?

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Need for an assessment methodology

• Unconsidered retention or creation of dangerous
  trees is irresponsible
• There is a clear need for specialised habitats
  for the protection of endangered species
• A methodology for assessment should consider
• The tree
• The landscape
• The people
• The wildlife

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THE END

• Thanks for your attention