Risk of N leaching from forests to surface waters in Norway

Data from soil surveys, lake surveys and deposition measurements for 634 squares of a 12x12 km grid in forest areas of Norway show that leaching of NO3 from forested areas of Norway is strongly related to N deposition but only weakly related to the C/N ratio of the organic soil layer. The survey data for soil are probably too coarse in scale to pick up the expected relationship between nitrate leaching and C/N in soil. These deposition, soil and water data can be used to assess the risk of future N leaching given scenarios of constant N deposition and climate change. The results show that continued accumulation of deposited N in the organic soil will increase the risk for NO3 leaching, and the risk further increases if climate change with increased temperature entails a decrease in the C stored in the soil.Statens forurensningstilsyn (SFT) (Naturens tålegrenser) Commission of European Communities (DYNAMO project