Analysis of pollen, including the determination of pollen concentrations and of relative pollen values, macrofossil analysis of peat cores from oxbows in river valleys and of pingo melt holes on the upland, and the application of recent surface samples from northern Finland have enabled the establishment of two different lines of vegetational succession, one for the valley and another for the upland. In the valley, the succesion is from Betula-, Betula + Populus-, Betula + Pinus-, Pinus + Betula + Corylus-, Pinus + Corylus to Alnus + Tilia. On the upland, the succesion is from Betula-, + Betula + Corylus-, + Corylus + Quercus to Corylus + Quercus + Ulmus. The order of appearance of pollen of the main forest trees is similar in all the pollen diagrams, but they differ in time of appearance. Radiocarbon dates indicate that Pinus, Corylus, Quercus, Ulmus, Tilia and Alnus appear in the valley 300–700 years earlier than on the upland. Juniperus occurred mainly on the upland. Taxa that were restricted to the upland include Empetrum, Erica tetralix and Arctostaphylos uva-ursi. Populus occurred only on the valleys.