The influence of stem girdling on survival and long term health of English oak (Quercus robur L.) and silver birch (Betula pendula Roth.)

Abstract

Accidental (strimmer, mower) or malicious girdling of ornamental trees is a frequent and underestimated problem in urban landscapes. No guidelines exist for landscape managers on the likelihood of fatal damage according to time of girdle, i.e., season (spring, winter) and extent of girdling. This report investigated the effect of stem girdling (0%, 25%, 50%, 75%, 100%) performed either during winter or spring on semi-mature birch (Betula pendula Roth.) and English oak (Quercus robor L) trees over a five-year period.1.All English oak survived any amount of girdling irrespective if girdled in spring or winter. Silver birch was more sensitive to girdling with 100% and 40% mortality recorded after a 100% winter and spring girdle, respectively.2.Tree vitality (leaf chlorophyll fluorescence, leaf chlorophyll content, crown leaf yellowing, nitrogen content) and growth (girth increment, die-back, number of epicormics above and below the girdle) of both tree species was not detrimentally affected following a 25% and 50% girdle.3.Epicormic production was more pronounced in English oaks compared to silver birch.4.Spring girdled oak typically had lower tree vitality and growth values than winter girdled trees indicating an influence of time of girdling. Such a response was not recorded in silver birch where time of girdling induced similar effects on tree growth and vitality.5.Growth and vitality measurements of surviving trees of both species were, in virtually all cases, statistically comparable with non-girdled trees by the end of the third growing season. Such a result indicates girdling >50% influences growth and vitality of both English oak and silver birch for three years.