N deposition :: Scots pine

Impact Type: Deposition of pollutant

Key Concerns:

Direct toxic effects of NH₃ at high concentrations have been observed near farms (Pitcairn et al. 1998, van der Eerden et al. 1998). Responses such as altered growth rates and tissue nitrogen concentration are more likely to be a response to total enhanced N deposition. Although the largest deposition fluxes occur in agricultural areas, impacts from N deposition on Scots pine trees in these areas are possible. Wet deposition of NH₄⁺ and NO₃^- cause acidification leading to a loss of base cations or eutrophication. It also increases the demand for base cations and micronutrients. N additions have also been shown to affect fruit body production in young stands of Pinus sylvestris Termorshulzen (1990).

Additional Comments:                                                                               

Of more concern is the effect of N deposition on the ground flora in Scots pine woodlands. Initial effects will probably increase tree growth which will immediately reduce light reaching the ground. Thereafter, increased litter fall will cover the ground flora and eutrophy the site. NH₄⁺ ions will be bound by organic matter and mineralisation can be stimulated. On less acid sites nitrification may give rise to NO₃^- leaching of base cations.