Late Quaternary landscape and vegetation diversity in a North European perspective

The rarefaction technique applied to fossil pollen sequences for analyzing palynological richness, interpreted as a signal of biological diversity of landscapes and vegetation, has been developed since 1988. Errors including population evenness and vegetation disturbance have been considered in this study. Information from two sites is discussed, one with a pollen diagram covering Late-Glacial (Late Weichselian) Time (14,400–10,500 cal. BP) and another one with a full-Holocene pollen diagram (last 12,500 years), both from southern Sweden. The climate change trend since deglaciation is reflected in a broad-scale biome change, from: (1) Late-Glacial, Arctic–Sub-Arctic open tundra–steppe with high diversity, via (2) Early Holocene, boreal birch–pine woodlands with relatively low diversity, towards (3) Mid-Holocene, nemoral broad-leaved woodlands during a climatic optimum with slightly increasing diversity, and (4) Late Holocene dynamic, human-influenced woodlands with high but fluctuating diversity. Diversity peaks are correlated with deforestation phases which are expansion periods for settlement and human impact. Intervening periods of reduced diversity correspond to forest successions with decreased human impact.