Pearce I S K, Woodin S J, Van Der Wal R
Centre for Ecology and Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK.
Department of Biological Sciences, University of Aberdeen, AB24 3UU, UK.
New Phytol. 2003 Oct;160(1):145-155. doi: 10.1046/j.1469-8137.2003.00875.x.
• The effects of nitrogen (N) deposition on the moss Racomitrium lanuginosum within montane heath in Scotland were investigated over 5 yr. • Permanent field plots were sprayed with KNO or NH Cl solutions, at doses equivalent to 10 and 40 kg N ha yr , in 3-6 applications each summer. • Racomitrium growth and cover were severely reduced by N addition, whilst the proportion of dead shoots greatly increased. N dose decreased inducibility of shoot nitrate reductase activity (NRA), suggesting that N saturation of Racomitrium occurred, and caused an increase in potassium leakage. At high dosage, effects of NH were more detrimental than NO . • Physiological responses to N indicate that the habitat's critical load (CL) is exceeded by addition of 10 kg N ha yr . The differential toxicity of the two forms of N suggests that predominant ion type in deposition should be taken into consideration when CLs are set. In contrast to tissue N, NRA correlated well with shoot growth, and may thus be a useful biological indicator of moss condition.
• 对苏格兰山地石南灌丛中苔藓毛梳藓受氮（N）沉降的影响进行了为期5年的调查。
• 永久性田间小区在每年夏季分3至6次喷施硝酸钾或氯化铵溶液，剂量相当于10和40千克氮/公顷·年。
• 添加氮使毛梳藓的生长和覆盖度严重降低，而死枝比例大幅增加。氮剂量降低了茎硝酸还原酶活性（NRA）的诱导性，表明毛梳藓发生了氮饱和，并导致钾泄漏增加。在高剂量下，铵的影响比硝酸盐更有害。
• 对氮的生理反应表明，每年添加10千克氮/公顷超过了该生境的临界负荷（CL）。两种氮形式的不同毒性表明，设定临界负荷时应考虑沉降中主要离子类型。与组织氮不同，NRA与茎生长相关性良好，因此可能是苔藓状况的有用生物学指标。
