FACTORS AND CONSEQUENCES OF RHYTHMIC GROWTH ON YOUNG AMERICAN RED OAK IN-FIELD CONDITIONS

In field conditions (ex-agricultural soils of south-west France), red oak is able to develop several growth flushes (polycyclism) in the 1st growing period of plantation. Polycyclism occurred only in the weeded treatment, and concerned one-third of weeded plants. NPK fertilization showed no influence on polycyclism. On the other hand, a significantly higher probability of polycyclism arose on small diameter plants or on plants without soil water excess. The consequences of polycyclism were an increase of diameter (+130%), leaf area (+120%) and ramification rate (from 24 to 64%). These advantages are very important for the success of this type of plantation. Polycyclic shoots were frequently basal shoots, and did not increase significantly the total tree height.