GROWTH RESPONSES OF GENETICALLY IMPROVED OPEN POLLENATED, FULL-SIBLING, AND CLONAL LOBLOLLY PINE TO THE FLEXSTAND\u3csup\u3eTM\u3c/sup\u3e SILVICULTURAL SYSTEM

ABSTRACT Loblolly pine (Pinus taeda) is often listed as the most commercially important timber species in the southeastern United States and is subject to genetic improvement via breeding programs to increase sawtimber yield, stem quality, and disease resistance. ArborGen has trademarked the FlexStandTM Silvicultural System (a method of interplanting rows of genetically improved trees with less expensive biomass trees) as a more economical solution to growing Loblolly pine. Two studies were conducted to in order to assess the FlexStandTM Silvicultural System. The first study assessed seedling mortality and growth of four different genetic combinations were assessed in the first four growing seasons at the Johnson Experimental Forest. Full-sibling seedlings showed no significant differences in growth or survival in comparison to clones. Although full-sibling seedlings were initially significantly taller than open pollenated (OP) seedlings, growth rates were not significantly different. The second study assessed the growth characteristics of full-sibling trees arranged in FlexStandsTM with elite OP biomass trees in comparison to monocultures in the ninth growing season. Full-sibling and OP monocultures had similar survival, diameter at breast height (DBH), height-to-live-crown, rust incidence, volume, and indices of competition. Full-sibling trees were significantly taller than the lowest grade OP trees, and had significantly less ramicorn branching and forking. In comparison to FlexStandsTM, full-sibling monocultures had significantly higher levels of competition due to closer spacing and significantly lower DBH. Stem quality, rust, ramicorn branching, forking, and volume did not differ significantly between full-sibling trees in monocultures and FlexStandsTM. These results suggest that the FlexStandTM is an economically advantageous option over monocultures, as volume and quality of trees sawtimber are the same as that of monocultures, but initial investment costs are lower in FlexStandsTM