中文摘要：

汶川是“五·—二”特大地震的中心地带，也是受灾最为严重的区域．本文基于震前3a的实地调查资料，对龙门山脉主峰——九顶山西坡汶川段的植物区系进行了系统分析，以期为灾后生物多样性的监测评估提供依据．在对九顶山西坡汶川雁门沟的野外调查中共发现维管植物11科、363属、733种，其中有种子植物94科、333属、687种．科的物种丰富性很高，含10种以上的种子植物科有19个，含216属、455种植物，分别占该区维管植物总属数和总种数的59．50％和62．07％，是该区植物区系构成的主导成分．种子植物区系成分复杂，15种分布类型在该区均有分布；温带分布的属和种远远超过热带分布类型，体现了该植物区系明显的温带性质．在东亚分布类型中，属于中国-喜马拉雅类型的属和种所占比例远远高于中国-日本成分，说明九顶山虽处于中国-喜马拉雅森林植物亚区与中国-日本森林植物亚区的交界线附近，但其西坡汶川段依然属于中国-喜马拉雅森林植物亚区的范畴．有367个中国特有种分布于该区，占物种总数的53．42％，其中半数以上的物种属于中国西南特有种或横断山区特有种，进一步证明中国西南高山区特别是横断山地区是温带植物物种的分化中心这一事实．图1表5参11

英文摘要：

Wenchuan County of Sichuan Province is the epicenter of the ＂5.12＂ Earthquake and it was terribly stricken by that disaster, including not only its infrastructure, but also its natural ecosystems due to the frequent aftershocks, debris flows and landslides. Mt. Jiuding with an elevation of 4 998 m a.s.1, is the main peak of the Longmen Mountains, where the famous fault line occurs from southwest to northeast, while very rich biodiversity is found and several nature reserves are located in this region. Just before the catastrophic earthquake, we explored the flora and plant diversity on Mt Jiuding. Now, this paper aims to summarize the investigation and provide background information for post-earthquake biodiversity conservation and ecological restoration. According to our field investigation on the west slope of Mt. Jiuding on Wenchuan side, there were 733 species of vascular plants, belonging to 363 genera and 111 families, of which 687 seed plants belonged to 333 genera in 94 families. The advantage of the dominant families was very obvious; 19 families with more than l0 species contained totally 455 species and 216 genera, which made up 59.50% and 62.07% of the total number of vascular plant species and genera, and formed the majority of the flora in this region. Although the floristic components in the region were very complicated, the temperate elements played a dominant role in the whole flora and greatly exceeded the tropic elements in terms of both genera and species. The floristic characteristics revealed its temperate feature. The genera and species belonging to Sino-Himalayan areal-type were much more than those of Sino-Japanese components, indicating that Mt. Jiuding should be included in the Sino-Himalaya forest subregion although it is located on the transitional belt of the Sino-Himalayan and Sino-Japanese area. In addition, the seed plant flora was rich in endemic species. There were 367 endemic species to China, accounting for 53.42% of the total seed plants on the west slopes of Mt. Jiuding.