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Abstract：
The effects of prolonged simulated acid rain on percentage cover of ground vegetation, and on growth and reproduction of two dominating dwarf shrubs (Emapetrum nigrum and Vaccinium vaitisidaea) were examined in a field experiment in the Finnish Subarctic, in an area with low ambient levels of sulphur and nitrogen deposition. Acid rain treatments included moderate (pH 3.8) and high (pH 2.9) concentrations of either H2 SO4 , or HNO3 , or a mixture of them, and were compared with irrigated (pH 6) and dry control plots. Long-term application of acid rain caused significant alteration in the cover and composition of ground vegetation. Effects of acid ram depended on the accompanying anion and on pH. Sub-plots under different canopy tree species differed in responses indicating that spatial heterogeneity is important in predicting the effect of acidifying pollution on this plant community. In the bottom layer, acid rain caused significant reduction in cover of the cyanobacterial lichens Nephroma arcticum and Peltigera spp. Decrease in cover of fruticose lichens, mainly composed of Cladina spp., more likely resulted from additional watering. In the field layer, acid rain containing moderate concentrations of NO- 3 caused an increase in cover of graminoid species. There were only slight alterations in growth and cover of the two dominant evergreen dwarf shrubs, Enigrum and V. vitis-idaea, indicating that these species are tolerant to acid rain of as low as pH 3. Even some positive responses of dwarf shrubs were observed, depending on canopy tree. Application of acid rain of pH 3 to plots under pine trees caused an increase in cover of I, vitis-idaea and, when the nitric acid only was applied, a short-term increase in the number of new shoots of E. nigrum. In contrast to vegetative growth, reproduction of the dwarf shrubs was more strongly affected by acid rain, but this also depended on local conditions and anion composition of acid rain. On \'pine\' plots, rain of pH 3 reduced the number of berries and flower buds on terminal current shoot of E. nigrum, however, this was partially compensated by an increase in berry production at the ramet level. Simulated acid rain had mainly negative effects on berry production by V. vitis-idaea.
摘要：
长期模拟酸雨对地面植被覆盖率的影响，并在芬兰北冰区的田间试验中检查了两种主要的矮灌木（Emapetrumnigrum和Vacciniumvaitisidaea）的生长和繁殖，在环境中硫和氮沉积水平较低的地区。酸雨处理包括中等浓度（pH3.8）和高浓度（pH2.9）的H2SO4，或者HNO3，或者它们的混合物，并与灌溉（pH6）和干燥对照地块进行了比较。长期施用酸雨会导致地面植被的覆盖和组成发生重大变化。酸性反应的影响取决于伴随的阴离子和pH。不同冠层树种下的子图响应不同，表明空间异质性对于预测酸化污染对该植物群落的影响很重要。在底层，酸雨导致蓝藻地衣的覆盖率显着降低。fruticose地衣的覆盖减少，主要由Cladinaspp组成。,更有可能是由于额外的浇水。在现场层中，含有中等浓度的NO-3的酸雨导致类线虫的覆盖率增加。两种主要的常绿矮灌木的生长和覆盖只有轻微的变化，Enigrum和V.Vitis-idaea,表明这些物种对pH低至3的酸雨具有耐受性。甚至观察到矮灌木的一些积极响应，取决于树冠。在松树下的地块上施加pH3的酸雨导致I的覆盖率增加，Vitis-idaea和,当仅使用硝酸时，黑曲霉新芽数量的短期增加。与营养生长相反，矮灌木的繁殖受到酸雨的影响更大，但这也取决于当地条件和酸雨的阴离子组成。在“松树”地块上，pH值3的雨水减少了E.nigrum末端当前芽上浆果和花蕾的数量，然而,这在一定程度上被增加的浆果产量所弥补。模拟酸雨主要对葡萄果蝇的生产产生负面影响。
