天山是横亘中国西北的著名山系之一, 将新疆分为南、北两个独立的地理区域, 其自身也构成了一个完整的自然地理单元。因其山体海拔高, 径向跨度大, 纬向延伸长, 气候、土壤和植被等自然地理要素各方面的区域差异, 这对花粉搬运、传播、保存与沉积产生了显著影响。本文根据对西天山北坡采集的 50 个表土样品花粉分析, 结合野外考察资料, 揭示了该区域垂直方向上表土花粉组合与现代植被之间的关系, 并进一步对天山表土花粉组合进行了区域对比。研究表明: (1)西天山北坡表土花粉谱可分为 5 个孢粉组合带, 从山麓到山顶分别为山地荒漠带、草原带、森林带、亚高山草甸带、垫状植被带。(2)当云杉属花粉含量介于 25%–30%时可认为该样品位于云杉林内, 森林植被带花粉组合表现为以云杉属(Picea)–蒿属(Artemisia)–藜科(Chenopodiaceae)–伞形科 (Apiaceae)为优势, 亚高山草甸带和草原带以蒿属–藜科–禾本科(Poaceae)–云杉属–麻黄属(Ephedra)组合为主, 山地荒漠带和垫状植被带以藜科–蒿属高含量为特征。云杉属花粉代表性较好, 含量与现代植被分布相一致, 但受气流影响显著。麻黄属含量和分布同样受气流影响, 其含量不能指示该植被在样点周围存在与否。蒿属、藜科呈超代表性, 只能指示区域生态意义, 而禾本科则由于花粉产量低表现出低代表性。(3)西天山北坡植被带最为复杂, 向东则逐渐简化。
The Tianshan Mountains, one of the famous mountain ranges in northwest China, forms a complete geographic zone f and divides Xinjiang province into two different natural geographic units: southern and northern Xinjiang. These two units display distinct vertical gradient distributions of climate, soil and vegetation types which impact on pollen transportation, dispersion, preservation and deposition. Based upon pollen assemblages of 50 modern pollen samples and the data of vegetation plots, both of which were collected from the northern slope of western Tianshan Mountains, we analyzed the relationship between vegetation and surface pollen assemblages and compared different pollen assemblages of the Tianshan Mountains. (1) We divide the pollen spectra into five pollen assemblage zones, i.e., mountain desert, steppe, forest, subalpine meadow, and alpine cushion, according to major vegetation types of the north slope of the western Tianshan Mountains. (2) When the percentage of Picea pollen is 25%–30%, the sample can be considered coming from the Picea forest. The dominance of Picea-Artemisia-Chenopodiaceae-Apiaceae assemblage indicates the existence of a forest vegetation. The subalpine meadow and steppe are dominated by Artemisia-Chenopodiaceae-Poaceae-Picea-Ephedra assemblage. High percentage of Chenopodiaceae-Artemisia pollen indicates mountain desert and alpine cushion vegetation. Picea pollen is representative, and its proportion in a sample is consistent with the distribution of modern vegetation, but is significantly affected by airflow. The distribution of Ephedra pollen is also affected by airflow, and its percentage cannot be used to infer whether the vegetation exists around the sample site or not. Artemisia and Chenopodiaceae pollen are super representative, but they are only of regional ecological significance, while Poaceae pollen shows low representativeness due to its low yield. (3) The vertical pollen spectra are the most complicated in the north slope of western Tianshan.