干旱区石羊河终闾湖泊孢粉组合中云杉圆柏属环境指示意义探讨

河西走廓东段、石羊河终闾湖泊边缘的三角城剖面下部全新世早期至末次冰消期的292-600cm处155个样孢粉组合显示云杉、圆柏属含量极高，两者之和达40%-60%左右，且百分比互为消长，通过对云杉、圆柏属生态习性、传播性能、与其它组分关系、当地特殊的自然地理条件和表土花粉记录的综合分析，笔者认为剖面中高含量的云杉、圆柏属来自流域上游祁连山，是石羊河搬运的结果，两者含量与区域有效湿度关系密切，云杉丰值指示湿润，圆柏丰值指示干旱。

Environmental Signals of Picea and Sabina of Sediments in Terminal Lake of Shiyang River, Arid Area

The Sanjiaocheng section is located at the end of Shiyang River which is an internal river system in arid area in Northwest China. This study focuses on the lower portion (292 - 600 cm) of the Sanjiaocheng section. Six carbon dates show the strata are bracketed between 7 000 and 13 000 a BP. The time interval represented by 2 cm of deposition between near pollen samples is 50 years. Fossil pollen and spore of 155 samples were extracted and analyzed using standard techniques. The pollen assemblage shows that the percentage of Picea varies inversely with that of Sabina,the combined percentage of the two being as high as 40%-60%. According to modern analogues of relationships among the ecological habits, transporting characteristics, and overall pollen assemblage, it was proposed that both Picea and Sabina were transported by water from the upper reaches of the Shiyang river, being indicative of effective soil moisture in the region. Specifically, high percentage of Picea implies high moisture, while high percentage of Sabinal high aridity. This idea is supported by the pollen data derived from surface samples. Wind has a very limited capacity to carry Picea and Sabina pollen from the mountain to the lowlands. There are several reservoirs in the upper and middle reaches of Shiyang River, without water transporting, the assemblage of pollen is dominated by local xerophyte. Therefore, Picea and Sabina suggest the vegetation of the mountain in the upper reaches of the Shiyang River.