| Summary: | Nitrogen (N) deposition is a key driver of global change with significant effects on carbon (C) cycling, species fitness, and diversity; however, its effects on Mediterranean ecosystems are unclear. Here, we simulated N deposition in an N-fertilization experiment with <sup>15</sup>N-labeled fertilizer in a montane evergreen Mediterranean holm oak forest, in central Catalonia, to quantify short-term impacts on leaf, leaf litter elemental composition, and resorption efficiency in three dominant species (<i>Quercus ilex</i>, <i>Phillyrea latifolia</i>, and <i>Arbutus unedo</i>). We found that even under drought conditions, <sup>15</sup>N isotope analysis of leaf and leaf litter showed a rapid uptake of the added N, suggesting an N deficient ecosystem. Species responses to N fertilization varied, where <i>A. unedo</i> was unaffected and the responses in <i>P. latifolia</i> and <i>Q. ilex</i> were similar, albeit with contrasting magnitude. <i>P. latifolia</i> benefited the most from N fertilization under drought conditions of the experimental year. These differences in species response could indicate impacts on species fitness, competition, and abundance under increased N loads in Mediterranean forest ecosystems. Further research is needed to disentangle interactions between long-term N deposition and the drought predicted under future climate scenarios in Mediterranean ecosystems.
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