Performance of two Picea abies (L.) Karst. stands at different stages of decline : IV. Xylem sap concentrations of magnesium, calcium, potassium and nitrogen.

The nutrient relations (nitrogen, magnesium, calcium, potassium, and manganese) of the xylem sap of spruce trees, Picea abies (L.) Karst., growing at a healthy and a declining site in Northern Bavaria, were followed on a diurnal and seasonal basis between April and October 1985. There were significant differences between the two sites in the xylem sap concentrations of all elements investigated except nitrogen. Nutrient concentrations remained constant diurnally despite changes in transpiration and xylem water potential. However, during periods between precipitation events, concentrations of elements in xylem sap decreased with decreasing xylem water potential. Apparent differences in needle chlorosis of spruce trees at the two sites were associated with consistent differences in nutrient contents of their xylem sap and needles.