Annual shoot growth components related to growth of Pinus brutia

Shoot elongation patterns of Pinus brutia Ten. were studied in six natural populations and 10 open-pollinated families within each population. The data were collected from a provenance-progeny trial that was thinned at Ages 13 and 17 years. Annual height increment was partitioned into first flush (spring shoot) and subsequent flushes (summer shoots) and the contribution of each to annual height increment was measured from Ages 7 to 17. Spring shoot elongation patterns were similar in all populations and families for 9 out of 10 years. In contrast, at all ages, populations differed significantly in total summer shoot growth and number of summer flushes. Families within populations differed in number of summer flushes in 7 out of 10 years. Summer shoot growth was the major cause of the differences in annual height growth among the six populations. Significant and high correlations were observed between summer shoot growth at Ages 7 to 12 and height at Age 13. A population from near the middle of the species' altitudinal range had more summer flushes than populations from higher or lower elevations, indicating an opportunistic growth pattern. Compared with mid-elevation populations, low- and high-elevation populations had more conservative growth patterns that depended mainly on growth of spring shoots. We conclude that summer shoot growth can serve as an explanatory variable to predict height growth of populations. Differences in shoot elongation patterns among Pinus brutia populations may be useful for selecting seed sources and for gene conservation programs.