Abstract: To investigate the effects of experimental nitrogen additions on the species diversity of the forest understory, the authors measured the plant diversity of the primary and the secondary tropical mountain rain forests, the subtropical evergreen broad-leaved forest, the temperate broad leaf-coniferous mixed forest and the cold temperate coniferous forest before and after N additions. Results showed that 1-year N addition significantly reduced the species richness in the primary and the secondary tropical mountain rain forests and the effects of N additions would be increased with the concentration of N additions (p < 0.05). Meanwhile, the high-concentration N addition also reduced the species richness, but low-concentration N addition increased the species richness in the temperate broad leaf-coniferous mixed forest. In addition, N additions increased species richness in the subtropical evergreen broad-leaved forest and the cold temperate coniferous forest (except for the high-concentration), but not significant. Moreover, the changes of Shannon-Wiener index responded to N additions have the similar trend with the change of species richness. The results suggested that nitrogen deposition changed biodiversity in the understory forests, but effects of N addition on biodiversity differ among the dfferent forests in China. Inconsistent with the general view, N addition reduced biodiversity in some forests but increased biodiversity in the others.

Key words: nitrogen addition, species richness, Shannon-Wiener index, tropical mountain rain forest, subtropical evergreen broadleaf forest, temperate broad leaf-coniferous mixed forest, cold temperate coniferous forest

摘要： 为研究氮沉降对林下植物多样性的影响, 选取4种中国东部典型的森林类型(热带山地雨林原始林及次生林、亚热带常绿阔叶林、温带针阔混交林和寒温带针叶林), 调查林下植物多样性在氮添加处理1年后的变化。结果表明: 氮添加显著降低热带山地雨林原始林和次生林林下物种丰富度, 且下降幅度随氮添加浓度的上升而增加(p < 0.05), 同时氮添加也降低温带针阔混交林高氮样方的物种丰富度, 但低浓度氮添加却增加林下物种丰富度(p < 0.05)。 另外, 在亚热带常绿阔叶林和寒温带针叶林(高氮样方除外), 氮添加增加林下物种多样性, 但变化不显著。Shannon-Wiener指数也显示相似的变化趋势。这些结果表明, 1年的施氮处理对森林生态系统林下物种多样性有显著的影响, 而不同处理水平在不同森林类型下的影响是不同的。这与以往的研究结果并不完全相同。

关键词: 氮添加, 物种丰富度, Shannon-Wiener指数, 热带山地雨林, 亚热带常绿阔叶林, 温带针阔混交林, 寒温带针叶林