UPTAKE OF (NH3)-N-15 BY PICEA-ABIES IN CLOSED-CHAMBER EXPERIMENTS

Above-ground deposition of anthropogenic trace gases like NH3 and NO(x ) is considered as a main factor for nitrogen (N) loading of Picea abi es ecosystems. In order to quantify NH3 deposition, tracer experiments with N-15 labelled NH3 were carried out in fumigation chambers (GSF M unchen). NH3 uptake is linearly related to the gas concentration in th e air, but the relation differs between organs and depends on N-nutrit ion of the organs. Plants well supplied with N have a lower NH3 uptake per g dry weight then plants deprived of N. Only a small amount of th e offered gas deposits to the external plant surfaces. The NH3 uptake rates of spruce indicate that NH3 may be regarded as being just as or even more important as environmental pollutant than NO(x) with respect to N loading of spruce ecosystems.