FOLIAR DEFICIENCIES OF MATURE SOUTHERN APPALACHIAN RED SPRUCE DETERMINED FROM FERTILIZER TRIALS

A field fertilization study employing additions of Ca, Mg, and N to a mature red spruce (Picea rubens Sarg.) stand was conducted at a high-elevation site in southwestern Virginia. Statistically significant increases in needle weight (20% larger than controls) were observed after two growing seasons in treatments receiving Ca or Ca plus Mg. Significant foliar growth responses were accompanied by significant increases (20-60%) in foliar concentrations of Ca, Zn, Mg, acid Mn in current-year and 1-yr-old needles. Both Ca and Mg addition, alone or together, appear to have alleviated antagonisms by Al towards the uptake of these four cations. Both the foliar growth response (negative) and the foliar N concentration response to N addition were nonsignificant, a response consistent with the evidence for N saturation at this site. Vector analysis, correlation analyses, and literature evidence all provide support at this site for a foliar deficiency of Zn at a foliar concentration of 14 mg kg(-1) and for a foliar and/or root deficiency of Ca at a current-year needle concentration of 1700 mg kg(-1). Foliar concentrations of Ca and Zn at or below these thresholds are common in southern Appalachian red spruce and may be related to its apparent growth decline in the higher elevations.