Appendix 3 - definitions

Arboriculture – the management of trees in the urban environment

Arboricultural officer (tree officer) – This can also be the tree and maintenance team leader or tree and landscape officer who deputises for the arboricultural officer.

Good arboricultural practice – appropriate tree surgery operations carried out at suitable times to promote the quality of trees and their enduring relationship with the urban environment.

Geographical Information System (G.I.S) – Computer database usually represented as a map with linked tables of data.

Dead, dying, diseased – see Dangerous

Dangerous – a tree can be classified as dangerous, posing a more than acceptable risk to persons or property, having been assessed of its chance of collapse and the potential damage that may result if it collapsed.

Failure risk assessment – An assessment based on how could the tree fail, what defects are present, probability of failure? Followed by

Consequential damage – what damage would the failure cause? Followed by

Hazard reduction – if more than acceptable risk present, tree pruning, removal, or relocate targets appropriate to each situation.

Decay detection equipment – a range of tools specifically designed to measure the extent of decay or remaining healthy timber in an individual tree.

Pollarding – the removal of all branches, leaving a trunk from which new branches will grow in successive seasons. Usually on a 5 – 15-year cycle, limited to a small number of species.

Physical damage – damage, usually cracking, to structures caused by incremental growth of stems or roots, or soil shrinkage due to water extraction.

Presence of live roots – taken from test boreholes dug in the area adjacent to property damage as evidence towards proving subsidence of a property.

Seasonal movement – physical damage to structures that increases with annual growth relating to direct damage. If subsidence is present the cracking will increase in summer and reduce in winter. (Deciduous trees extract large volumes of water during summer months and dramatically less in winter when trees are without leaves).

Cyclical works – removal or adjustment of stakes and ties from young trees, removal of basal or epicormic growth, crown lifting to clear footpaths or highway vision splays