The time course of diameter increment responses to selection harvests in Acer saccharum

We used dendroecological techniques to analyze the temporal pattern in diameter growth following selection harvests in stands dominated by Acer saccharum Marsh. in central Ontario and examined differences in growth responses related to tree size, damage, and orientation relative to canopy gaps. While dendroecological studies have commonly assumed that trees show immediate growth responses to gap creation (i.e., within 1–2 years), we found that the growth enhancement in A. saccharum was gradual and did not reach a peak until 3–5 years following gap creation. Trees of intermediate size showed the largest proportional growth increases after gap creation, with the largest responses observed in trees on the north side of gaps. Trees with visible damage to the crown or bole had significantly lower preharvest basal area increments than trees with little or no damage, but showed greater proportional growth responses to gap creation. Both the long observed time delay in tree growth response to canopy opening and the variability in response relative to tree size and damage have important implications for attempts to reconstruct disturbance history using dendroecological methods and to sustainable forest management under selection system silviculture.