Estimating the foliage area of Maritime pine (Pinus pinaster Ait.) branches and crowns with application to modelling the foliage area distribution in the crown

Abstract

Destructive measurements of architecture and biomass were performed on 63 trees from three Pinus pinaster stands (5, 21 and 26 year-old) in order to determine the quantity and distribution of foliage area inside the crown. Allometric equations were developed per site and needle age, which allowed to correctly calculate (R2 = 0.71 to 0.79) the foliage area of a branch, knowing its basal diameter and its relative insertion height in the crown. Using these equations, we estimated total crown foliage area. A non-linear function of tree diameter and tree age was fitted to these data (R2 = 0.82 and 0.88). On the 5 and 26 year-old stands, we combined the branch level models and the architectural measurements to develop probability functions describing the vertical and horizontal foliage area distributions inside the crown. The parameters of the beta functions varied with needle and stand age, foliage being located mostly in the upper and outer part of the crown for the adult tree, whereas it was more abundant in the inner and lower parts of the crown in the 5 year-old trees. A simple representation of crown shape was added to the study, so that knowing tree age and diameter, it could be possible to fully describe the quantity of foliage area and its localisation inside a maritime pine crown.