<正>对上海生态林病虫害及生态林存在问题进行了调查研究，并对其病虫害的发生原因进行了分析。调查表明：上海城市生态系统中的植物种类相对稀少，林分结构较为单一，缺乏病虫害天敌；上海城市森林受人为因素干预程度大，受城市“热岛效应”的影响明显。病虫害发生的主要原因为：城市绿地面积和绿化树种盲目增加，打破了原来城市森林生态环境的平衡发展；不合理引进外来树种，而且树种种植结构不合理或管理粗放，导致一些外来的或原次要的病虫害严重发生。针对存在的问题提出上海杨树生态林病虫害综合治理策略。

Effects of different levels of NaC1 solution (CK:0g/L, S1:1g/L, $2:1.5g/L, S3:2g/L, S4:2.5g/L, S5:3g/L) on plasma membrane permeability, proline content, nitrate reductase activity of leaves and root activity of Pteroceltis tatarinovaii Maxim. seedlings were investigated under hydroponic culture conditions in a greenhouse. The results indicated that the increases in plasma membrane permeability of CK, S1 and $2 were generally lower than those of S3, S4 and $5. The increases in proline contents of CK and S1 were lower than those of S2, S3, S4 and S5, and proline contents of S3, S4 and $5 were significantly higher than those of CK, S1 and S2. Nitrate reductase activity of each treatment fluctuated as stress time progressed. Both the nitrate reductase activity of $4 and that of $5 versus stress time curves appeared the two-bell shape rather obviously; root activity of each treatment fluctuated as stress time progressed, and generally speaking, root activities of $3, $4 and $5 were highly significantly lower than that of CK. The preliminary conclusion was drawn that 2 g/L was the critical concentration of NaC1 solution which obviously affects the plasma membrane permeability, proline content and nitrate reductase activity of leaves as well as root activity of P. tatarinowii seedlings.