Abstract

Keywords

crown, southern britain air pollution forest decline european beech twig analysis growth trees morphology ozone waldsterben , above-ground part of trees, Methods: methodology, Plants: Fagus sylvatica, methodology

Abstract

Considerable difficulties exist with the standardization and interpretation of assessments of crown defoliation, the most commonly used index of tree health in Europe. A variety of other measures of crown condition exist and one that has received considerable attention, particularly for beech (Fagus sylvatica L.), is crown architecture. Four stages of crown development are generally recognized, termed the exploration, degeneration, stagnation and resignation phases. An analysis of the available literature suggests that there are a number of problems surrounding the use of these classes to describe trees. Although the classes probably reflect the progressive deterioration of the crown of a tree, there are many factors that affect the assessment and interpretation of the scores, as is the case for defoliation estimates. Measurements of shoot elongation in the upper crown provide a more useful measure, but involve destructive sampling and are very time-consuming. Consequently, while crown architectural assessments should only be incorporated into large-scale inventories of forest health with great care, they may be useful for case studies involving the detailed examination of a small number of sites.

LWF Classification

Network: Sanasilva, Category: ISI,