Determination of the nitrogen compound balance between the atmosphere and a Norway spruce forest ecosystem

Abstract

Wet, throughfall and stemflow deposition measurements of nitrogen compounds (NH4 +- and NO3 –-ions) were carried out in a Norway spruce forest in Hungary, together with direct dry deposition and emission estimates (NH3, NO, NO2, HNO3, N2O gases, NH4 + and NO3 – particles). The total deposition of nitrogen compounds from the atmosphere to the forest ecosystem, estimated as the sum of the wet deposition and the measured dry flux, was 1.9 g N m–2 yr–1 for the examined period (1996–1998). The net deposition (difference of the deposition and the emission) was 1.8 g N m–2 yr–1. About 61% of the deposition is due to dry deposition processes. Ammonia gas dominates in the dry deposition (48%). Soil emission of nitric oxide (NO) and nitrous oxide (N2O) constitutes only 5% of the total (wet and dry) deposition. From the comparison of directly measured dry deposition figures and the dry deposition calculated as the difference of the throughfall plus stemflow and wet deposition, it is probable that around 60% of the dry deposited nitrogen compounds (36% of the total, dry and wet deposition) are taken up by stomata, mostly in gaseous form. The remaining part (64%) of the deposited nitrogen compounds is leached to the ground where it is partly taken up by the root system, takes part in the soil mineralisation processes, or leaves the ecosystem by ground or surface water run-off.