Influence of herbaceous competition on growth and architecture of young red oak trees (Quercus rubra L.) in plantation

Young red oak trees planted on a former agricultural soil have been submitt ed to two extreme levels of herbaceous competition combined with two levels of fertilization. The herbaceous competition is associated with a decrease of 70% of the mean total height and with a decrease of 18% to 86% of the n umber of growth units produced each year. It induced also a decrease of 50% of the growth units mean number of internodes and leaves and a decrease of 30% up to 60% in its mean internode length. Initial fertilization stimulat ed only diameter growth of weeded trees. The number of branches per growth unit is lower for non-weeded trees (between -20% and -80%), but not differe nt or upper per length unit, and oldest branch mortality is higher in relat ion to light competition. In a general way, weeds competition tends to limi t tree crown expansion and the expression of the architectural sequence of differentiation.