Abstract: The study on lake surface sediment pollen assemblage and flux is of important significance for paleoecological environment reconstruction because it provides the references such as the origin of pollen， pollen representative and environment significance. In order to study the relationship between the lake surface sediment pollen and the regional vegetation landscape， 20 sites are investigated along the southeast-northwest， the southwest-northeast and the south-north transections of the lake Gun Nuur， northern Mongolia， in hope that spatial distributional characters of pollen assemblage， pollen concentration and representation of main pollen genera could be disclosed. Specifically， pollen assemblage and total pollen concentrations of 20 sites were analyzed and the relationships between pollen assemblages and the regional vegetation pattern were multi-variably and statistically discussed， the relationship between total pollen concentration and water depth were explored too. Firstly， pollen assemblage data shows the noticeable differentiations existed along southeast-northwest direction， which is characterized by a decline in [Pinus Diploxylon-type] pollen percentage and increases in [Betula，Artemisia，]Chenopodiaceae and Gramineae pollen percentages， and this differences might be attributed to the influences of the Scots pine forest developed to the east and south of Lake Gun Nuur， and this was also disclosed by the result of detrended correlation analysis （DCA） on those 20 lake surface sediment pollen assemblage， suggesting that sample sites could be distinguished by the enginevalue of axis 1， maybe the axis 1 represent the distance between the sites and the Scots pine forest in the south and east. And over-representation of Scots pine pollen was disclosed or confirmed in the landscape of Scots pine-dominated forest steppe， while under-representation of [Artemisia] and Chenopodiaceae were suggested and this might resulted from the compensation-decline effect （i.e.， Fagerlind effect） of Scots pine pollen percentages. Furthermore， comparison between contour maps of total pollen concentration and the water depth may suggests a positive correlation existed， showing high total pollen concentration at deeper sites and vice versa， suggesting the suspension and redeposition by water flow was notable. The results of the study in this paper provide references to study the distribution of modern pollen and the reconstruction of the ancient environment. On the other hand， this study on pollen of lake surface deposition can be a reference in this research field in northern China.

Key words: northern Mongolia, lake surface sediment, pollen assemblage and concentration, spatial distribution