|Eilers, G; Brumme, R; Matzner, E: Above-ground N-uptake from wet deposition by Norway spruce (Picea abies Karst.), Forest Ecology and Management, 51, 239-249 (1992)|
Nitrogen-uptake from wet deposition, by above-ground plant parts of IO-year-old Norway spruce trees, was studied as a function of the N-form, N-concentration in precipitation and intensity of irrigation by using ‘SN-labelled solutions. The irrigated solutions contained all major cations and anions as present in normal forest rainwater but with varying NH4 and NO3 contents. After 5 months of treatment, the trees were harvested and needles, stems, main stem and roots were analysed for “N content. Nitrogen-uptake was calculated from the sum of “N in all plant compartments. Significant amounts of N were taken up by the above-ground parts of the plants in all treatments. NH4 uptake was higher than NO3 uptake if applied in the same concentration. Nitrogen-uptake increased with increasing N-concentrations and irrigation intensity. Extrapolating these results to mature stands (by extrapolating needle biomass and with the assumption that mature spruces are able to take up N from wet deposition during the winter months at the same rate as determined for the young trees in this experiment) suggests annual uptake rates of N in the range of 9 kg ha-’ under field conditions. Measuring atmospher+ N input by throughfall collection may substantially underestimate actual N inputs to forest ecosystems. Uptake of N by above-ground parts may cause nutritional disturbances indicated by changes of the N: Ca and N: Mg ratios in the needles and thus may contribute to the occurrence of Mg-deficiency symptoms of Norway spruce.