黑河中游现代孢粉传播过程研究

在位于河西走廊的黑河中游地区选取8个河流沉积样品和7个表土样品进行孢粉分析,通过其孢粉百分含量分别探讨河流与风力搬运对孢粉传播的影响。结果表明：风力对孢粉具有较强的搬运能力,能够将区域外或上游山地植被孢粉搬运至中游地区,但其对当地孢粉贡献较小,一般低于10%;河流搬运孢粉的能力大于风力,能够将上游山地植被孢粉大量的搬运至研究区,外来孢粉含量最高可达39.4%,成为孢粉谱的重要成分。表土孢粉组合能够较好的反映研究区现代植被的分布情况;河床沉积物孢粉组合反映的是上游山地植被和研究区植被混合状况。

Modern Pollen Transportation Process in the Middle Reach of the Heihe River

Modern pollen assemblages in the arid regions and consequently the fossil ones, considerably differ from the modern vegetation and palaeo-vegetation caused by various dispersal agents, depending on the sampled location and the geographical conditions. Fluvial flow and wind are the main agents to influence the pollen transportation in the arid regions. Exotic pollen carried by these two dispersal agents could interrupt the relationship between the pollen and vegetation. Therefore, the influences of these two dispersal agents on the pollen transportation must be taken into account as reconstructing the palaeo-vegetation and the palaeo-environment via fossil pollen data. Moreover, a distinction should be made between the local pollen, which indicate the conditions around the sapling sites; and the exotic pollen, that rather represent far away vegetation, together with the energy and possibilities of the dispersal agents. To do this, we collected 8 riverbed samples and 7 surface soil samples for pollen analysis across the middle reach of Heihe River, located in the Hexi Corridor. The results showed that wind affects the pollen transportation relatively weak, percentages of exotic pollen transported by wind are usually under 10%. The surface soil pollen assemblages can reflect the distribution of local vegetation. While fluvial flow could carry more pollen from the upland to the study area and strongly affect the pollen transportation. Notably, the percentages of exotic pollen transported by fluvial flow reach up to 39.4%, and exotic pollen becomes the dominance of the pollen assemblages, leading an inaccurate relationship between the pollen assemblages and the local vegetation. The pollen assemblages of fluvial sediments mirror the distribution of upland vegetation and local vegetation.