Deposition of ammonia to the forest floor under spruce and beech at the Höglwald site

Abstract

Laboratory and field measurements of the flux of ammonia to forest floor canopies of spruce and beech stands at the Hoglwald site in southern Bavaria are reported. Measurements were performed with an open chamber method. A linearity between ammonia concentration and ammonia flux from the atmosphere to the ground floor canopy was detected. Deposition of ammonia showed no saturation even at air concentrations up to 50 μg NH3 m−3 air. Temperature, water content and the moss layer of the ground floor canopy had a minor influence on the deposition velocity in laboratory experiments. Deposition velocity of ammonia was higher to the spruce (1.3 cm s−1), and limed spruce ground floor canopy (1.17 cm s−1) compared to the beech stand (0.79 cm s−1). In field studies, a diurnal course of the deposition velocity was detected with highest velocities in midday and minor during night times, but not in the climatic chamber. The flux of ammonia to the ground floor canopy was estimated of app. 10 kg N ha−1 yr−1 for the soil under spruce, 9 kg N ha−1 yr−1 for the limed spruce and 6 kg N ha−1yr−1 for the soil under beech. The fluxes are interpreted as fluxes from the atmosphere to the ground canopies of the stands.