MODELING CROWN SHAPE OF PICEA-ABIES - SPACING EFFECTS

A model of branch length increment and inclination was developed for P icea abies (L.) Karst. to describe the dynamics of crown shape. Four t rees belonging to the provenance Istebna, from Poland, were sampled in an experimental plot where density varied continuously from 200 to 10 000 stems/ha. Sampling along the density gradient enabled us to study the effect of spacing on tree morphology and development. The model o f branch extension is based on height growth and on the year of elonga tion of the branch. A second model describes the change in branch incl ination. Branch spread increased with between-tree spacing, whereas br anch inclination was affected by crown contact; competition was then d ivided into two components: (i) direct mechanical contact and (ii) glo bal resource depletion. The sample trees were young (26 years), so hei ght growth was mainly linear and the effect of apical control could no t be tested. This study provides a simple model of crown shape develop ment that can be used in a more detailed process-based model. Simulati ons are presented based only on height growth. For wood quality purpos es, the relationship between branch diameter and branch length is prov ided to give access to the knottiness of the stem. The limitations of the sample are discussed in view of a more general use of these models .