Climate as a confounding factor in the response of surface water to nitrogen deposition in an area south of the Alps

Climate effects on NO3 concentrations have been investigated for two small rivers south of the Alps draining forested catchments. The Pellino and Cannobino rivers are representative of different stages of N saturation determined by high deposition of inorganic N (2.0–2.5 g N m−2 a−1). Long-term records of air temperature, precipitation, N deposition and stream NO3 concentration were used to assess the relative effect of N deposition and climate on NO3 export from the catchments. The climate signal was more evident in the river with the lower NO3 concentration. Prolonged dry and warm periods were the precondition for the occurrence of the highest peaks of NO3 concentration.