Abstract
Enhanced nitrogen inputs to both terrestrial and aquatic ecosystems affects biodiversity at all its levels. Grasslands provide a
complex range of functions, due to their wide representation throughout terrestrial ecosystems. Numerous studies demonstrate
soil acidification, eutrophication and species richness reduction as a result of elevated reactive nitrogen availability. The present
study aims to assess soil nitrogen stocks and transformations for two Romanian grasslands during November 2011 – November
2013, integrating the microbial population dynamics of two important functional groups involved in terrestrial nitrogen cycle:
ammonifiers and denitrifiers. Our research focused on pristine systems, as well as on an experiment that simulated high nitrogen
inputs of 100 kg N/ha/year (during 2012 and 2013) for one of the two selected study areas.