No abstract

<p>In the last decades, 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. For instance, past studies reported that N deposition, may influence CO<sub>2</sub> emission, lower CH<sub>4</sub> consumption by the soil and increase the emission of N<sub>2</sub>O. Nevertheless, the mechanistic understanding of these ecological responses is still far to be reached. 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. Hence, experiments simulating this process by applying fertilization above the canopy are needed.</p><p>The aim of this study is to explore how N deposition influences greenhouse gas (GHG) emissions in a temperate oak forest (Quercus petraea Liebl.) located in Monticolo (Bolzano, Italy). In this site, a set of three plots was created and replicated three times. Each set includes a control plot, a plot with below-canopy fertilization (N<sub>BL</sub>) and a plot with above-canopy fertilization (N<sub>AB</sub>). The fertilization is applied, since 2015, from May to September, for a total annual N addition of 20 kg N ha<sup>-1</sup>.</p><p>Since April 2018, CO<sub>2</sub> emission has been monthly measured with a portable infrared gas analyzer. Measurements were performed on three points per plot, for a total of 27 measurement points. During measurements, soil moisture and soil temperature at 10 cm depth were measured as well.</p><p>The measurements of CH<sub>4</sub> and N<sub>2</sub>O started during the growing season in 2019 and are performed on a monthly basis by a static chamber method. Three chambers were installed per plots, for a total of 27 chambers.</p><p>We will present the preliminary results of this study. The results showed that the 5-year N fertilization did not lead to significant differences between plots in terms of GHG fluxes. The sensitivity of CO<sub>2</sub> emission to temperature was not influenced by extra N. The differences were not significant between fertilized and unfertilized plots, nor between the two fertilization methods.</p>