Presentation on theme: "Brian Crane, November 2006 TREES – IN HABITAT – AS HABITAT Issues, considerations, suggestions."— Presentation transcript:
Brian Crane, November 2006 TREES – IN HABITAT – AS HABITAT Issues, considerations, suggestions
Brian Crane, November 2006 Contents Tree habitats Trees as habitat Management considerations and options Marble Hill Park, London
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 Urban areas bring man and tree into closest conflict (1) Safety – Need for management increases with intensity and sensitivity of site use (e.g. children’s 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
Brian Crane, November 2006 Failed Aesculus hippocastanum High Wycombe, Buckinghamshire, England
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 The urban situation Managed trees High maintenance input Multiple problems Historic considerations
Brian Crane, November 2006 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
Brian Crane, November 2006 Urban areas - clear conflict……… Highly prized trees In areas where they are under pressure HOLD THIS THOUGHT!!!!!
Brian Crane, November 2006 Rural areas – tree habitats Forests (economic) Woodlands (amenity and multi-use) Farmland Hedgerows Transport systems Roads Rail Waterways Suffolk, England
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 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
Brian Crane, November 2006 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…………
Brian Crane, November 2006 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
Brian Crane, November 2006 Burnham Beeches, Buckinghamshire, England. Photo Roy Finch
Brian Crane, November 2006 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.
Brian Crane, November 2006 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!!!!!
Brian Crane, November 2006 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 !!!!!!
Brian Crane, November 2006 Dangerous branches over house SE, 2006, photo De Gouret
Brian Crane, November 2006 Suspect, dead pollard close to railway line (DG) SE, 2006, photo De Gouret
Brian Crane, November 2006 Stumps in conifer plantation SE – responsible for infestation of bark beetle in standing crop (DG) SE, 2006, photo De Gouret
Brian Crane, November 2006 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
Brian Crane, November 2006 Creating ’old’ trees (2) This may be justified BUT we must consider the situation: Aesthetics – Landscape – Historical implications Safety – Position – Liability
Brian Crane, November 2006 Photo DG, 2006
Brian Crane, November 2006 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?
Brian Crane, November 2006 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
Thanks for your attention THE END Brian Crane, November 2006