中文摘要：

山地生态系统对气候变化的敏感性和预警作用，使其成为全球变化领域里的重要研究内容之一，但是目前能够敏感记录山地生态系统变化的环境指标非常有限。对青藏高原东南缘的贡嘎山东坡海拔高度1200～4600m不同植被带以约50m间距采集的70个表土样品进行植硅体分析，结合PCA（Principal Component Analysis）研究结果，发现表土植硅体组合沿海拔变化明显。植硅体类型和数量变化很好地反映了垂直植被带的变化：1）低海拔山地亚热带常绿阔叶林带（1200～2200m）为阔叶木本“Y”字型-哑铃型-十字型-短鞍型植硅体组合；2）山地暖温带针阔叶混交林带（2200～3200m）为阔叶木本“Y”字型-针叶树类型-方型-扇型-长鞍型的组合；3）山地寒温带暗针叶林带（3200～3700m）为针叶树类型-帽型-齿型-尖型-针茅哑铃型组合；4）亚高山亚寒带灌丛草甸带（3700—4600m）为帽型-齿型-团块型-针茅哑铃型组合。表土植硅体组合PCA分析的第1轴得分较好地指示了植被沿海拔的分布及其与温度的关系，反映山地植被带及其对应的植硅体组合变化可能主要受控于温度的影响。研究表明，植硅体分析可以作为恢复山地古植被演替和古环境变化的重要指标。

英文摘要：

Mountain ecosystem is sensitive to climate change and of great importance in the global change research, but there are only a few environmental proxies which could indicate the changes of mountain ecosystem. The integrated vegetation belts in Gongga Mountain, southeastern Qinghai-Tibetan Plateau（ in the area of 29°20＇ - 30°20＇N and 101°30＇- 102°15＇E）are considered ideal for montane environment change and proxy tests. The present work analyses phytoliths assemblages from 70 topsoil samples collected at an altitudinal interval of about 50m between 1200m and 4600m a. s. 1. on the east slope of Gongga Mountain. Phytolith grains were carefully separated from soils and concentrated, accomplished by heavy-liquid flotation, then identified （28 types）and counted under microscope （at least 300 grains per sample）. Results show that the topsoil phytolith assemblages can differentiate the altitudinal vegetation belts： （1）In mountainous subtropical evergreen broad-leaf forest belt, at 1200 -2200m a. s. 1., the phytolith assemblages are mainly comprised of broad-leaf-type （6.8%）, dumbbell （24.1%）, cross （5.7%） and short-saddle types; （2） Phytolith assemblages from warm temperate mixed needle-leaf and broad-leaf forest belt, at 2200 - 3200m a. s. 1.,are characterized by abundant broad-leaf-type, conifer-type, square, fan and long-saddle types. Broad-leaf-type decreased （2.3%） and conifer-type increased （ 2. 1% ）. And Stipa-dumbbell appeared ; （3） Phytolith assemblages from cold temperate dark coniferous forest belt, at 3200 -3700m a. s. 1., have abundant conifer-type （4.5%）, rondel,trapezoid, point and Stipa-dumbbell types. Percentage of broad-leaf-type （0.6%） reduced dramatically; （4） In subalpine shrub and meadow belt at 3700 -4600m a. s. 1., the phytolith assemblages are mainly composed of rondel, trapezoid, gobbet and Stipa-dumbbell types. The percentage of Stipa-dumbbell（ 4. 0% ）and gobbet（ 3.6% ） reach maximum value. Sample scores of first axis