2.1 Characteristics of ancient trees
Trees have three stages in their lives – formative, full to late maturity (or veteran), and ancient. The length of these stages can vary depending on the species, the environment in which the tree has lived and what happens to it during its lifetime.
An ancient tree is one which is in the final stage of its life. It is old compared with others of the same species, and often has a wider trunk. (Recall from the clip 'Sherwood Forest' how the age of the tree was estimated by measuring the girth of the trunk.) Table 1 defines the minimum tree girth to distinguish ancient trees for different species. The canopy of an ancient tree is retrenching or 'growing downwards', giving the tree its distinctive squat, fat appearance, often with protruding deadwood and a hollowed trunk (Figure 6).
Table 1 Minimum trunk girths that can be counted as 'very large girth for the species' for a selection of tree species.
|Trunk girth (minimum)||Tree species|
|190 cm||Birch species, hawthorn|
|240 cm||Field maple, rowan, grey and goat willow, hornbeam, holly, cherry, alder|
|310 cm||Oak species, ash, Scot's pine, yew, elm species|
|470 cm||Lime species, sycamore, horse chestnut, poplar species, other pine species, beech, sweet chestnut, white and crack willows|