How did changing climates shift plant communities during deglaciation?

During the deglaciation of the Pleistocene Epoch, shifting climates forced plant communities to undergo significant migration and reorganization to remain within suitable environmental conditions. As glaciers retreated, species—particularly those of the taiga—began a gradual northward expansion in Europe and North America.123

This transition was characterized by several key processes:

• Migration and Dispersal: Plants migrated through seed dispersal, with species capable of longer-distance dispersal gaining a competitive advantage. In some regions, such as western Canada, this movement was rapid, facilitated by strong winds associated with atmospheric circulation around remnant ice sheets.32
• Community Reorganization: Deglaciation created unique, "disharmonious" environments that lacked modern analogues, allowing species with different temperature and moisture requirements to coexist. For instance, cold-tolerant species like spruce were often found alongside temperate hardwoods.14
• Range Shifts: As warming trends progressed, cold-loving plants retreated to higher latitudes or elevations. Conversely, barriers such as mountains or seas led to the extinction of various tree species that could not migrate effectively, resulting in floristically impoverished regions in parts of Europe.52