XVI International Botanical Congess

Due to patchiness of landscape numerous forest ecosystems are exposed to anthropogenic N input. In spruce forest acidification of the soil, enhanced emission of greenhouse gases to the atmosphere and nitrate leaching into groundwater are observed as a consequence, although autotrophic nitrifiers can usually not be found in the soil. Still autotrophic nitrifiers are present in the phyllosphere of spruce and are reponsible for a significant part of the dry deposition of NH3 in the canopy. Wet deposition of ammonium and nitrate to the soil changes the competition between plant roots and nitrifying bacteria for these nitrogen sources thereby affecting trace gas exchange between the soil and the atmosphere and nitrate availability for leaching.