Figure 5.

Ancient examples of plaid (left) and striped (right) landscapes based on the postglacial distribution of biomes in northeastern North America reconstructed from palaeobotanical records (redrawn from Dyke, 2005). Prior to 9 ka, rapid changes in the locations and extents of biomes occurred, at times with little regard for latitudinal climatic gradients. Palynological records suggest that between 11 and 5 ka the northern limits of a number of tree species in northeastern North America lagged behind their physiological range limits by as much as 1500 years because of dispersal lags (Prentice, Bartlein, & Webb, 1991). After approximately 5 ka, biome positions have remained relatively stable. Note that these biomes are defined by vegetation structure – not by the presence of certain indicator species.