Element concentrations and storage in the aboveground biomass of limed and unlimed Norway spruce trees at Höglwald

Twenty years after the application of dolomitic limestone to a well growing, mature Norway spruce stand at Höglwald, Southern Germany an amount of magnesium equal to the input by liming has left the rooting zone. However, 80% of the applied calcium was retained by the ecosystem. A detailed biomass investigation was carried out in order to elaborate whether the stand shows any nutritional benefits and if the aboveground tree biomass represents a sink for calcium and magnesium after liming. Stem wood, bark, branches, twigs, and needles were analysed for the major nutrients. Needles showed higher calcium and magnesium concentrations and significantly lower potassium concentrations on the limed plot. Surprisingly, limed trees had significantly lower magnesium concentrations in the bark but higher concentrations in twigs and needles than unlimed trees. In addition, significantly lower concentrations for potassium, sulphur, and phosphorus were measured in the bark of limed trees, whereas the element concentrations in the wood were rather similar between the two treatments. The low potassium concentrations in bark and needles indicate an impeded potassium uptake after liming presumably due to a calcium potassium antagonism. Magnesium is probably used to compensate the relative lack of potassium. The small differences in the calculated nutrient storage of limed and unlimed trees, however, suggest that the aboveground biomass can be excluded as a relevant sink for the applied calcium and magnesium at the Höglwald site.