External indicators of living branches with missing rings within a tree crown of Corsican pine

The development and the number of rings of first-order branches on the stem of 17-year-old Corsican pine (Pinus nigra Arnold ssp. laricio Poiret Maire var. corsicana) were studied in order to characterize living branches with missing rings. For the thickest living branch of each tier, the difference between the number of growth units and the number of rings indicated that missing rings at the base of the branch are common in Corsican pine. Such branches can be externally characterized by a decrease in growth unit length associated with a lack of branching. These two architectural features may help to identify non-ring-producing branches, with implications for physiological studies on stem-branch relationships and research into wood quality, as well as for management decisions concerning pruning.