Abstract: The change of vegetation in Maili region over the last 3 400 14C years has been reconstructed based on a high-resolution pollen record. It was thought that the contrast between arboreal and herb plants in different periods might well reflect the change in relative extent of the fixed sand dunes and active sand dunes, and the evolution history of the sand dunes could be thus investigated. Before 3 100 a BP, the sand dunes around Maili bog supported a denser vegetation, with Quercus mongolica Fisch., Tilia L., Ulmus L. as its dominating taxa. Declination of the open forest and increase of major herb taxa since 3 100 a BP suggest an increasing area of semi-fixed and partly active sand dunes mainly supporting Artemisia L. and Chenopodiaeeae. Such a changing process has generally been continued through the last 3 000 years. However, the period from 1 000 a BP to 660 a BP was unique in that it witnessed a lush growth of nearly all of the taxa in the region, with the expanding of Quercus mongolica population being especially obvious. The desertification process starting at 3 100 a BP ceased during that time, and the different types of sand dunes were supporting a much denser vegetation covered in the period than any others.

Key words: Horqin sand land, Pollen analysis, Vegetational changes, Late Holocene