HEIGHT GROWTH OF 12 DOUGLAS-FIR (PSEUDOTSUGA-MENZIESII (MIRB) PARL) SEED SOURCES BETWEEN 1 AND 25 YEARS OLD

Height growth of 12 Douglas fir seed sources has been compared using modelling (height-age curves) and multifactorial analysis. Modelling led to the definition of significantly different seed source groups based on height growth rate (table V). The multifactorial analysis showed that seed sources had different growth patterns (figs 6, 7), linked to genotypic and environmental effects. For example, the 1976 drought slowed down the growth of some but not all seed sources (figs 4, 5). Age-age correlations for height have been investigated (figs 2, 3). The seed sources growth speed and pattern are useful in choosing the seed sources best adapted to different sylviculture type, and in particular, couple spacing-rotation. Respective advantages of multifactorial analysis and modelling have been discussed.