THE EFFECTS OF SCION MATURATION ON GROWTH AND REPRODUCTION OF GRAFTEDSLASH PINE

Establishment of the University of Florida Cooperative Forest Genetics Research Program's clone banks provided an opportunity to look at sci on maturation effects on growth and reproduction of many grafted slash pine clones. In 1988 and 1989, clone banks were established in nine l ocations in the Southeastern United States. Over 460 scion clones vary ing from 5 to greater than 40 years old from time of seed germination (chronological age) were grafted into the clone banks. Comparisons of diameter growth, height growth, lateral branch number and female and m ale strobili production were made annually for six years after graftin g. Within slash pine clone banks, there were significant effects due t o scion chronological age. Chronologically older scions (backward sele ctions) grew less, had fewer branches and produced only a few more fem ale strobili than chronologically younger material (forward selections ). Forward selections produced significantly more catkin clusters than backward selections. By year six, there was no significant difference in numbers of female strobili per tree between backward and forward s cions, but forward selections produced about 2.5 times as many catkin clusters as the backward selections. Similar effects on growth and rep roduction due to chronological age were also found among clones within the forward selections, with older selections growing more slowly and producing fewer catkin clusters. The size and breadth of this study l ends strong support to the idea that these patterns of growth will occ ur for grafted slash pine in any location throughout its native range.