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 dispe...