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

Height growth of 12 Douglas fir seed sources has been compared using m odelling (height-age curves) and multifactorial analysis. Modelling le d to the definition of significantly different seed source groups base d 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 sl owed 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 s eed sources growth speed and pattern are useful in choosing the seed s ources best adapted to different sylviculture type, and in particular, couple spacing-rotation. Respective advantages of multifactorial anal ysis and modelling have been discussed.