POSTGLACIAL TRENDS IN PALYNOLOGICAL RICHNESS IN THE NORTHERN FENNOSCANDIAN TREE-LINE AREA AND THEIR ECOLOGICAL INTERPRETATION

The northern Fennoscandian tree-line area consists of fairly distinct vegetation zones. The pollen stratigraphies of two boreal sites and tw o tundra sites were studied and the palynological data analysed numeri cally. The main aim was to measure palynological richness, using raref action analysis, and to assess its value in reflecting patterns of pas t floristic richness. Rates of palynological change were measured usin g both chord distance and Euclidean distance as the dissimilarity coef ficient. The results show low palynological richness during the Younge r Dryas. The values increase rapidly at the transition to the Holocene . During the Holocene the values are in reversed order in relation to present vegetation density, the tundra sires having the highest palyno logical richness. This suggests that differences in the size of the po llen catchment may have an important role in palynological richness es timates and that no straight comparisons of palynological richness sho uld be made between sites from different vegetation zones. Most pronou nced changes in palynological richness take place in the Lake Rautusel ka core, where high Pinus pollen influx is correlated with low palynol ogical richness. At the boreal sites, high rates of change are associa ted with higher palynological richness whereas no similar relationship is observed at the tundra sites.