Whole-tree biomass and carbon allocation of juvenile trees of loblolly pine (Pinus taeda): influence of genetics and fertilization

To assess the contribution of belowground biomass allocation towards total carbon (C) allocation of two provenances of loblolly pine (Pinus taeda L.), we examined the total biomass allocation of a fast- and slow-growing famil y from each provenance. Since planting on a xeric, infertile site in Scotla nd County, N.C., U.S.A., trees in this study have been subjected to one of two nutrient treatments: optimal nutrition or control (no fertilization). T otal biomass of 24 (1 tree/family plot x 2 families x 2 provenances x 2 tre atments x 3 blocks) 5-year-old (juvenile) trees was harvested in January 19 98. Fertilization increased total root, total shoot, and total tree biomass in all families as compared with harvested trees in control plots. Fertili zation also increased biomass of coarse-root, woody-root, taproot, stem, br anch, and foliar components of families as compared with trees in control p lots. Although there were treatment and family differences in standing-crop biomass of the total root, total shoot, total tree, and various individual root and shoot components, the percent biomass (whole-tree) allocation to these tissues remained similar across treatments. Total nonstructural carbo hydrate (TNC) analysis indicated some treatment, family, and provenance dif ferences in TNC concentrations and partitioning to starch and soluble sugar s. At the time of harvest, TNC concentrations of belowground tissues were m uch higher than those of aboveground tissues, and enhanced partitioning tow ards starch in root tissues indicates an important C storage role for below ground tissues at this time. Indeed, more than 90% of the trees starch cont ent was present in root tissue in January. Although constrained by a sample size of three harvested trees per family, this study suggests that biomass allocation on a whole-tree level was similar between fast- and slow-growin g families of different provenances of juvenile loblolly pine and was not a ffected by fertilizer treatment.