Time trends for genetic parameters of wood density and growth traits in Pinus sylvestris L.

Genetic parameters of wood density in Pinus sylvestris were estimated and c ompared with corresponding parameters for height and diameter increment. Me asurements were made on 10 mm increment cores from a 33-year old non-contig uos single-tree plot progeny trial. Totally 944 trees from 106 full-sib fam ilies were included in the study. REML-estimates of the variance components were obtained by iteration on a mixed model equation system and time trend s for the calculated parameters were plotted. With the exception of the most juvenile wood, which showed higher values, t he additive genetic coefficient of variation (CVA), the environmental coeff icient of variation (CVE), and the phenotypic coefficient of variation (CVP ) for wood density, all showed stable values over time. The heritability wa s high, fluctuating around 0.4 and with no tendency to differ between juven ile and mature wood. Wood density showed lower CVA but higher heritability than height increment. The effect of competition on the estimated genetic p arameters was discussed and the effect seemed moderate for wood density and height increment but strong for diameter increment where CVA, CVE and CVP increased monotonically over time.