Species And Transplant Size Influence Post-Transplant Survival, Growth And Root Regeneration Of Three Oak Species
Three oak species (swamp white oak [Quercus bicolor Willd.], scarlet oak [Quercus coccinea Mϋnchh.], and bur oak [Quercus macrocarpa Michx.]) at three caliper sizes (small - 3.8 cm [1.5 in], medium - 6.4 cm [2.5 in], and large 10.2 cm [4 in]) were transplanted balled and burlapped in spring within a nursery where they were subject to the same environmental conditions over three growing seasons. Nine treatments (the interaction of all species and size variables) were analyzed to determine the influence caliper size and species had on mortality, canopy dieback, canopy growth and root growth. Caliper size had no influence on post-transplant leaf area for all species, while species influence on post-transplant leaf area was difficult to measure due to leaf morphology differences between these oak species. Shoot growth for all treatments was consistently well below that of the control trees over all three growing seasons, with only one exception. In this study, mortality and canopy dieback data provided better measures of post-transplant performance than canopy growth data. Transplanted trees were considered successful if they not only survived but also thrived (had less than 20% canopy dieback). All three species transplanted equally well at the small caliper size. Species significantly influenced transplant survival and success rates for both the medium caliper and large caliper treatments. For both of these caliper size treatments swamp white oaks had higher survival and success rates than either other species, with the exception of the large caliper scarlet oaks that were equal in survival alone to the large caliper swamp white oaks. Additionally, more medium and large caliper scarlet oak transplants survived and thrived than bur oaks at those sizes. Caliper size only significantly influenced post-transplant performance of bur oaks, with smaller caliper trees transplanting with greater survival and success. Although caliper size did not significantly influence post-transplant performance for scarlet oaks and swamp white oaks, both species did trend toward fewer large caliper trees thriving than either other caliper size. This study suggests that the influence of caliper size on post-transplant performance strongly varies between species, even for species within the same genera, due at least in part to root system morphology. The species that had the most fibrous root system, swamp white oak, transplanted with the greatest success and the species with the coarsest root system, bur oaks, transplanted with the least success. There was a strong positive relationship between the number of roots that are cut during the transplanting process and the number of new roots per tree that developed at the ends of those severed roots after transplanting. However, the influence that the number of cut roots had on the number of new roots per tree that were produced differed greatly by species. When the same number of roots per tree were cut, swamp white oaks generally produced more new roots per tree than either other species and scarlet oaks generally produced more new roots than bur oaks.
dissertation or thesis