中文摘要：

在贵州龙里地区开展降雨连续监测，依据监测结果，配置不同pH值梯度的模拟酸雨；选择杨梅、油茶等10种贵州典型森林群落优势种，对植物叶片开展模拟酸雨喷淋试验；并利用便携式光合仪LI-6400观测喷淋前后叶片的光合作用，研究酸雨对贵州典型森林群落植物叶片的直接伤害作用.实验结果显示：①pH值5.0和4.0的模拟酸雨基本不会影响供试树种冠层叶片的光合作用；pH值3.0的模拟酸雨使小果红椿、枫树冠层叶片的净光合作用速率不同程度地升高，升高率为11.03%和0.62%，其他树种效果不明显；②pH值2.0的模拟酸雨使供试树种冠层叶片的净光合作用速率降低，其中小果红椿、枫树、白栗和香叶树尤为明显，降低率为28.32%、30.32%、12.21%和11.37%；pH值2.0的模拟酸雨使小果红椿叶片出现可见直接伤害，叶缘和脉间出现黄白色斑点，有穿孔，其他树种未发现可见直接伤害症状.研究表明，研究区典型森林群落植物叶片出现可见直接伤害的酸雨pH值阈值在2.0~3.0之间；同时，在酸雨对叶片造成可见直接伤害之前，存在隐性直接伤害，对叶片造成隐性直接伤害的酸雨pH值阈值为3.0.依据试验结果，从研究区监测数据分析，目前酸雨对该区植物冠层叶片的直接伤害有限.

英文摘要：

Continuous monitoring of acid rain was conducted at Longli in Guizhou Province in 2007. Acid rain simulation experiments were performed based on monitoring results. The leaves of 10 dominant tree species were sprayed with simulated acid rain with different pHs and the net photosynthesis rates of leaves before and after spraying were measured using an LI／｜6400 photosynthesis system. The direct damage by acid rain on the foliage was evaluated. The results are summarized as follows： firstly, the net photosynthetic rates of foliages of all trees were not obviously changed by the simulated acid rain with pH 5.0 or 4.0; The net photosynthetic rate of foliage of Toona sinensis and Acer mono increased by 11.03% and 0.62% respectively under simulated acid rain of pH 3.0, while the net photosynthetic rate of the foliage of other trees did not change. Secondly, the net photosynthetic rate of the foliage of all the trees decreasedto a greater or lesser extent when exposed to simulated acid rain with pH 2.0, among which Toona sinensis, Acer mono, Quercus foabri and Lindera communis Hemsl decreased by 28.32%, 30.32%, 12.21% and 11.37% respectively. Simulated acid rain with pH 2.0 caused visible direct damage to the leaves of Toona sinensis. Yellow-white speckles appeared on the edges of the leaves and between the venations, and some leaves were even perforated. Visible damage was not observed on other trees. The results show that the pH threshold that causes visible direct damage to the leaves of a typical forest community of Guizhou province is between 2.0 and 3.0. Invisible direct damage, however, occurs before visible signs appear. The pH threshold that causes invisible direct damage to the leaves is pH 3.0. Considering our simulation experiments and monitoring data, the direct damage to foliage of the typical forest community of the study area is imperceptible.