Was not covered by ice during the Pleistocene and served as a refuge for many northern species of plants and animals. Because of the NE-SW orientation of the mountains, some species were able to migrate with the glaciers 20,000 years ago. They migrated southward to escape advancing glaciers. Some species remained after glaciers retreated. Many southern species reach the northern limit of their ranges in the southern Appalachians.
Climate changes with increases in elevation.
Going up 1,000 feet is like traveling north 200-250 miles. The climate on the highest peaks in North Carolina and Tennessee mimics that of southern Canada. Besides having a variety of climates as we travel up the slopes, there are different microhabitats on each slope. Northern slopes are cooler and wetter at the same elevation than a southern slope or even an easterly facing slope. The different aspects of the slopes receive greater or lesser rainfall, and more or less exposure to the drying effects of the sun.