The effect of soil nutrient availability on retranslocation of Ca, Mg and K from senescing sapwood in Atlantic white cedar

Nutrient resorption from senescing tissues increases plant nutrient-use eff iciency, and may be an adaptation to nutrient limitation. In some tree spec ies, retranslocation of nutrients from sapwood during heartwood formation i s a comparable process. We measured Ca, Mg and K concentrations in Atlantic white cedar (Chamaecyparis thyoides) stemwood samples taken from two swamp s in the northeastern United States and compared them to soil mineral nutri ent availability at each site. We found that Ca, Mg and K concentrations we re 60-700% higher in sapwood than in the immediately adjacent heartwood, in dicating retranslocation of these nutrients from senescing sapwood. Sapwood nutrient concentrations were similar between the two sites. However, nutri ent concentrations in the heartwood differed significantly between the site s, as did the relative degree of Ca and Mg retranslocation from senescing s apwood. We found these differences between sites to be inversely related to significant differences in exchangeable Ca, Mg and K as well as Al concent rations in the soil. These findings suggest that the degree of nutrient ret ranslocation from senescing sapwood may be influenced by soil nutrient avai lability.