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Published: 2001

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Genetically improved loblolly pine (Pinus taeda L.) trees under intensive silviculture have demonstrated dramatic increases in wood production. However, increased input intensity has been associated with a higher propensity for certain genotypes to increase stem and branch deformities, as well as reduced disease resistance. The responses of several genotypes of loblolly pine to nutrient additions on stem sinuosity were assessed at three and twelve years of age in two different tests located in South Carolina and North Carolina, respectively. The objectives of the studies were to assess the effect of nutrient additions and genetics on stem form, particularly stem sinuosity, in loblolly pine. Tissue samples from of each newly expanding shoots at the beginning of growing season were taken and analyzed to assess the association between the nutrient concentrations on the tissues and stem sinuosity in five families from two provenances (Atlantic Coastal Plain “ACP†and Lost Pine Texas “LPTâ€). The second study was established at the ArborGen research facility near Summerville, South Carolina, with six different genotypes of loblolly pine to determine whether high N and low Ca availability caused sinuous growth. In early spring, eight blocks were fertilized with N as (NH4)2SO4 and Ca as CaSO4. Nutrient concentrations from flushing shoot tissue were examined and then correlated with measures of stem sinuosity. Results from the study of repeated nutrient additions in North Carolina showed that the addition of nutrients increased stem sinuosity, branch sinuosity, height, and the levels of N, P, K, Mg, Zn, B and S in the woody tissue of newly expanding shoot and decreased the levels of Mn and Cu. Calcium levels were the same in both treatments. Stem sinuosity was positively correlated with tissue nitrogen (N) concentration, while negatively correlated with manganese (Mn) levels. Negative family-mean correlations between N and Mn were found in both treatments (control and.