GENETIC-VARIATION IN CARBON-ISOTOPE DISCRIMINATION AND ITS RELATIONSHIP TO GROWTH UNDER FIELD CONDITIONS IN FULL-SIB FAMILIES OF PICEA-MARIANA

Measurements of the stable carbon isotope composition of leaf tissue were made on Picea mariana (Mill.) B.S.P. trees from four full-sit, families grown on three different field sites at the Petawawa National Forestry Institute, Ontario, Canada. The four families chosen exhibited genetic variation for growth characteristics. Genetic variation was also observed for carbon isotopic discrimination (Delta) among the families of P. mariana. In addition, a strong correlation occurred between Delta values measured on trees in 1991 and 1992, two years that had very different precipitation and temperature conditions during the growing season, indicating that the ranking of individual trees remained almost constant between years. A strong, negative correlation was observed between average carbon isotope discrimination and average tree height for the four families on the driest, least productive site, as was expected based on leaf photosynthetic characteristics. There was no significant correlation, however, between Delta values and growth on the other two study sites, where productivity was higher.