An assessment of the movement behaviour of bifurcations in hazel (Corylus avellana L.) under dynamic wind loading using triaxial accelerometers

Abstract

Accelerometers are potentially a valuable tool in analysing the movement behaviour of trees and their component parts. Most previous research using similar tools has assessed the stability of tree stems and roots under wind loading, but accelerometers can assess a wider range of component parts of trees, associated defects and growth forms. In this study, the movement of sixteen bifurcations in semi-mature hazel trees (Corylus avellana L.) was assessed using triaxial accelerometers during seven differing wind loading events. Seven of the bifurcations were normally formed, with the other nine bifurcations containing bark inclusions, of which a subset of five were restricted by being in direct contact with neighbouring branches. Analysis of the acceleration data from the three windiest days showed that synchronised movement of the pairs of branches arising from the normally formed bifurcations reduced the potential acceleration of one branch away from the other by an average of 57.72%, whereas this reduction was found to be only 40.38% for the bark-included bifurcations. The data collected from this study indicate that normally formed bifurcations are not necessarily structural flaws in trees as the synchronised movement of the two branches of a bifurcation means they typically avoid damaging stresses occurring at the join under dynamic wind loading: the presence of rubbing or touching branches may, however, give rise to abnormal movement behaviour and heightened stresses.