External and internal growth parameters as potential indicators of shake in sweet chestnut (Castanea sativa Mill.)

Growth measurements of individual stems in mature chestnut (Castanea sativa Mill.) stands were taken prior to felling. Stem form, leaf phenology and wood structure were assessed in standing boles, mainly of coppice origin, at five sites on contrasting soil types in Kent, south-east England. The majority of trees exhibiting ring and star shake were older, flushed later in the spring than sound trees and had shorter flushing periods than sound individuals. Traits such as the presence of epicormic shoots, bole curvature and spiral bark pattern were also significantly correlated with shake. Increment cores revealed that shaken trees tended to have narrower rings, but larger diameter spring vessels compared with their sound counterparts. A logistic regression model confirmed that shake could be modelled using relatively few parameters, including age, flushing phenology and the proportion of spring wood, whereas subjective scores based on bark characteristics alone were less reliable.