Nisbet T R, Fowler D, Smith R I
Forestry Authority Research Division, Alice Holt Lodge, Farnham, Surrey, UK, GU10 4LH.
Environ Pollut. 1995;90(1):111-20. doi: 10.1016/0269-7491(94)00081-n.
The impact of conifer afforestation on stream-water chemistry was investigated in the acidified catchment of Loch Dee, SW Scotland. Long-term trends in stream-water chemistry were evaluated during a period of forest growth from age 6 to 17 years. A significant increase was observed for pH (0.2 units) and a significant decline for aluminium (0.05 mg litre(-1)), sulphate (1.2 mg litre(-1)) and nitrate (0.02 mg litre(-1)) concentrations. The long-term decrease in stream-water acidity was ascribed to the marked reductions in sulphur depositions during the 1970s and early 1980s. There was no evidence that this response had been attenuated by afforestation, the improvements in stream-water chemistry being of a similar magnitude to those recorded in nearby moorland lochs and exceeding that in an adjacent moorland-catchment stream. The lack of a clear forest acidification effect is consistent with deposition-model estimates which show the increased scavenging of occult and dry deposition by the growing forest to be small at this site (</=10%). Critical load calculations suggest that planned emission reductions will be sufficient to protect the catchment stream from further acidification by 2003. The additional deposition capture by the continued growth of the forest is predicted to delay this response by approximately 2 years.
在苏格兰西南部洛赫迪酸化集水区，研究了针叶树造林对溪水化学性质的影响。在森林生长6至17年期间，评估了溪水化学性质的长期趋势。观察到pH值显著上升（0.2个单位），铝（0.05毫克/升）、硫酸盐（1.2毫克/升）和硝酸盐（0.02毫克/升）浓度显著下降。溪水酸度的长期下降归因于20世纪70年代和80年代初硫沉降的显著减少。没有证据表明这种响应因造林而减弱，溪水化学性质的改善幅度与附近泥炭地湖泊记录的幅度相似，且超过了相邻泥炭地集水区溪流的改善幅度。缺乏明显的森林酸化效应与沉积模型估计结果一致，该模型表明，在该地点，生长中的森林对隐蔽和干沉降的额外清除作用较小（≤10%）。临界负荷计算表明，计划中的排放减少量将足以在2003年前保护集水区溪流免受进一步酸化。预计森林持续生长带来的额外沉积物捕获将使这种响应延迟约2年。
