Assessing vigor when tree marking: the importance of crown dieback

Abstract

The silvicultural approaches generally used for uneven-aged northern hardwood stands mostly involve partial cuts. To facilitate the implementation of stand improvement in these cuts, several classification systems have been developed to help tree markers visually assess tree vigour based on the presence of individual defects. However, very few studies have tried to empirically validate such systems. We assessed tree vigour using repeated measurements collected as part of long-term silvicultural trials conducted in 615 permanent plots throughout the northern hardwood forest of Quebec, Canada. Our results confirmed that crown dieback is by far the best indicator of tree vigour. They also showed that the rate that vigorous trees develop defects increased with increasing diameter.