GROWTH AND YIELD OF MARITIME PINE (PINUS-PINASTER AIT) - THE AVERAGE DOMINANT TREE OF THE STAND

A stand growth model was developed using 2 attributes, height and basal area of the average dominant tree. The model is based on temporary plots corresponding to different silvicultural treatments, thinning and fertilization experiments. - Regarding the first attribute, dominant height growth: a model using 2 uncorrelated parameters was developed. It was derived from a previous principal component analysis based on data issued from stem analysis. The first parameter is an index of general vigor, which is well correlated with the dominant height h0 (40) at the reference age of 40 years. The second parameter refers to variations in the shape of the curve, particularly for intial growth. The growth curves of the various temporary plots could be accurately described with this model. Phosphorus fertilization at the time the stand was established improved both dominant height h0 (40) and initial growth. - Regarding the second attribute, basal area growth: the basal area increment was described using 4 independent variables: height increment, dominant height h0 (40), age and competition. This model includes the effect of stand density. It was validated considering the error term and its first derivative according to age. The model may therefore be used as a growth function. Nevertheless, residual variance was rather high and could be subdivided into a random component (75% ot the residual variance) and a slight autocorrelation term, ie a correlation between successive deviations due to unknown factors. The relationship between basal area growth and age was assumed to be the result of both increased leaf biomass and dry matter partitioning. The relationship to height increment may result from leaf biomass and morphogenetical components, both number of needles on the leader and the other foliated shoots.