Since 1987 the Forestry Commission has monitored annual changes in the condition of Britain’s forest trees by assessing the status of:
This is performedvia a network of fixed monitoring plots distributed throughout the country.
Plots consist of 24 trees, located in four sub-plots of 6 trees and each tree is evaluated for a range of health indicators. These include the incidence of flowering and fruiting anddamage by insects or fungi, but the overall assessment of health is based on crown density. This is an estimate of the degree of transparency of the crown (crown density), which is used to provide an index of tree condition.