Morphological trends in main stem of Pinus radiata D. Don: Transition between vegetative and reproductive phase

Abstract

Developmental patterns of structural units of the main tree axis of Pinus radiata were investigated in two plantations in Chile growing under different ecological conditions. Environmental characteristics of sites were recorded and structural features of sample trees were measured. Annual shoot length, number of growth units per annual shoot, growth unit length, and number of branches and cones per growth unit were statistically compared between sites and between vegetative and reproductive phases of trees. No clear pattern of stand development was apparent when variables were directly examined in terms of actual dimensions ( cm) and time scale ( years). In contrast, common patterns of development of structural parameters were indicated after dimensions and time were normalized so as to express them on a ontogenetic scale. The number of growth units per annual shoot and average length of annual shoot increased during the juvenile stage of development. Transition from juvenile to mature stages brought about a change in this trend, either stabilizing or reversing the pattern of development and size of these structural elements. The practical consequence of these changes on wood quality for industrial purposes is discussed.