Genetic and environmental variation of foliar nutrient concentrations and strobilus initiation in fertilized loblolly pine seed orchard ramets.

Fertilizer was applied annually for eight years to individual ramets in a loblolly pine (Pinus taeda L.) seed orchard at rates ranging from 0 to 448 kg nitrogen (N) ha(-1) year(-1). Clonal effects accounted for a major source of variation in both flowering and foliar nutrient concentrations. Foliar N concentrations were generally correlated with the intensity of fertilizer application, but were only weakly correlated with flowering. There was a long-term trend for increasing concentrations of foliar manganese (Mn) and boron (B), and decreasing concentrations of magnesium (Mg) and zinc (Zn) with increasing fertilizer rates, although only the differences in Mn concentration were statistically significant. Fertilizer had little effect on the concentrations of other foliar macro- or micronutrients during the study. The optimum fertilizer rate for flowering was 224 kg N ha(-1) year(-1).