Dynamics and underlying processes of N2O and NO soil atmosphere exchange under extreme meteorological boundary conditions Climate models predict an increasing frequency and intensity of summer drought periods with subsequent heavy rainfall or soil frost and thaw events in mountain regions of Central Europe. These indirect effects of global warming may considerably influence soil microbial processes and in consequence emissions of climate relevant trace gases. Regarding the nitrogen cycle N2O and NO emissions are of concern since they are involved in climate warming and soils represent a main source for these two gases. In spite of a growing number of studies on this subject knowledge on effects of climate change on soil N2O and NO emissions is still scarce. This is mainly due to a hitherto poor mechanistic understanding of underlying processes within soil. In this thesis the impact of extreme meteorological boundary conditions on N2O and NO fluxes in a Norway spruce forest and an acidic fen in the Fichtelgebirge area was investigated. The summer drought period and precipitation were experimentally increased in the forest and the fen over a 2 year span. Soil frost was induced in the forest by removal of the natural snow cover. The experiments were run in three replicates each and non manipulated plots served as controls. Throughout the experiments N2O and NO fluxes were recorded in weekly to monthly intervals. In addition N2O concentrations and isotope signatures in soil air were measured along soil profiles to identify and localise the underlying biogenic production and consumption processes. Prolonged drought continuously reduced the N2O emission from the forest soil and even turned the soil temporarily into a sink for atmospheric N2O. Soil freezing and thawing caused a burst of N2O release contributing 84 % of the annual emission ...