Abstract
Recently, the effects of nitrogen (N) deposition on temperate forests have received much interest. Studies recorded several changes in soil carbon (C) and N cycles due to extra reactive N available. However, most of the studies neglected to include the canopy interception in the experiments simulating N addition, notwithstanding tree canopy have shown to change both the amount and the chemical composition of the N deposition, although the underlying mechanisms are not yet clear. Hence, experiments simulating this process by applying fertilization above the canopy are foreseen. The aim of this study is to explore how N deposition influences processes of the N cycle and greenhouse gas (GHG) emissions in temperate mountain forests. The study will be conducted in two experimental sites located is in Monticolo (Bolzano, Italy) and Cembra (Trento, Italy). In each site, a set of three plots was created and replicated three times. Each set includes a control plot, a plot with below-canopy fertilization and a plot with above-canopy fertilization. The fertilization is applied from May to October for a total annual N addition of 20 kg N ha-1. The analysis will regard different processes related directly or indirectly to the soil N cycle: litter and dead wood decomposition, microbial biomass and activity, N mineralisation and nitrification in the soil, soil gas emissions (N2O, CH4, CO2, NH3). The outcomes of the project will contribute to understand the impact of N deposition on temperate mountain forests. It will also contribute to the knowledge about the role of the canopy in the N cycle in forest ecosystems.