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traits, should be evaluated very carefully when early evaluation of genetic entries is practised in
Douglas-fir, since these traits (budburst timing, lammas growth and free growth) appear to be
plastic in character.
303. Kaya, Z. 1993. Genetic variation in shoot growth components and their correlations in
Pseudotsuga menziesii var. menziesii seedlings. Scandinavian-Journal-of-Forest-Research 8(1):
1-7.
Keywords: genetic tree improvement
genetic relationships
growth
Abstract: Stem-unit measurements could be useful for early selection if these dimensions
were highly heritable and strongly correlated with traits of commercial interest, such as height
growth. Height increments and the number and length of stem segments were measured in the
first and second growth period in predetermined and free growth of Douglas-fir (Pseudotsuga
menziesii var. menziesii) seedlings from 40 families in each of 2 populations from southwestern
Oregon, USA. Populations, or families in populations, exhibited genetic variation in all traits
except number of stem units in predetermined growth. Heritabilities for stem-unit measurements
were higher than those for height increment in the first growing season, but not in the second.
Correlations among measurements of stem units and height increments were only moderate
(generally