A study on topsoil pollens in the east of Qaidam Basin

The features of pollen assemblages are dealt with in this paper using the methods of DCA and correlation analysis. Altogether 23 samples taken from topsoils at 8 sites in the east of Qaidam Basin are studied. In this study area, pollen taxa are mainly shrubs and herbs, whose total percentage is 92.77%～100%. Pteridophyta pollen is found in 5 samples, but the percentage is quite low, only less than 0.38%. This pollen assemblage clearly shows the characteristics of obvious desert and steppe desert area without trees. In the pollens of shrubs and herbs, Artemisia and Chenopodiaceae dominate in desert area, being respectively about 40% and 70% in general and 66.38% and 74.54% at maximum. Comparatively, Ephedra is also commonly seen, whose percentage is usually less than 5%, but in 6 samples the percentage is more than 10% and 49.27% at maximum. Gramineae and Compositae also occupy a certain percentage, the maximum may reach 10.6% and 6.82%. Results of DCA and correlation analysis appear that the features of topsoil pollens in different vegetations are not the same. Different assemblages of pollens can be distinguished and are in accordance with corresponding vegetations and environments. According to the aridity, the vegetation communities are divided into four groups: severe drought group, moderate drought group, slight drought group and slight-drought-and-slight-wetness group and it is found that A/C (Artemisia/ Chenopodiaceae) in the desert can indicate the aridity. A/C value is less 0.2 in the severe drought group, 0.2～0.5 in the moderate drought group, 1.63 in the slight drought group and 5.72 in the slight-drought-and-slight-wetness group with aridities being 8.96, 3.00, 2.98 and 2.82 respectively.