The influence of taproot shape on stem form in loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.)
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Two studies were completed to evaluate the influence of taproot shape on stem form in loblolly (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.). In the first study, measurements were collected on loblolly pine seedlings after each growing season. These seedlings were comprised of three full-sibling families subjected to five taproot treatments: a straight taproot (control treatment), straight taproot with underground obstruction, taproot planted with J - form, taproot planted at a 45 degree angle, and a straight taproot with the stem guy-wired to a 45 degree angle. Growth and stem form measurements were evaluated to determine the effect family, taproot treatment, or their interaction had on stem form. In the first year, there were significant family and taproot treatment effects on growth and form, while in the second year only family effects were significant. There was a significant interaction of family and taproot for one stem form measurement (amplitude) in year two. Significant growth variation was found among families in a post harvest measurement. A stem form sinuosity index interaction effect was also found to be significant. In the second study, measurements were collected on slash and loblolly pine aged three to six years old planted at six locations throughout Georgia. J, L, and straight taproot treatments were applied to these trees in split plots with fertilization and weed control. Growth and stem form measurements were collected during the winter of 2003. Measurements were evaluated to determine the effects of taproot treatment, split-plot treatment or their interaction for each of the six sites. Significant differences were found among the taproot treatment at two locations. No split-plot or interaction differences were found.