In the Tertiary, beginning around 65 million years ago [Ma], a temperate forest prevailed unlike any other in Earth’s history. Referred to as the Arcto-Tertiary forest—existing on a landmass that would soon become North America, Europe, and Asia—a blending of conifers and broad-leaved trees dominated the landscape. With continental drift and climate change, the offspring of these great forests were fragmented. Over time, ice ages came and went, causing a change in flora as increasingly dry conditions became more common. The descendants of the Arcto-Tertiary forest became less extensive and more isolated. These progenitors have remained, finding refuge in the higher and cooler regions which maintained a climate more similar to that of the early Tertiary and creating, today, a strong Klamath-Appalachian Connection (see R. H. Whittaker 1961).
Today, North America holds two of the most species-rich temperate forests in the world: those of the southern Appalachian and Klamath Mountains. What do these locations have in common? Glaciers and seas did not completely cover them during the Cenozoic and the mountains were monadnocks, or islands above the plains, offering temperate refuges to plants and animals over time. Both locations have historically maintained a moderated climate. These areas are beyond the southern terminus of the enormous continental ice sheets of the Pleistocene. Some plants undoubtedly remained in these regions through historic climatic change, while other species repeatedly moved in as climate cooled and glaciers pushed southward and then moved out following glaciers northward. These dynamic fluctuations have cradled plant diversity in these two unique regions.
The current consequences of these historical patterns are that the Klamaths and southern Appalachians have grand floristic diversity, a concentration of endemic plants, and a fundamental importance to the forest floras of nearby regions (Whittaker 1961). Per unit area, the Klamath Mountains and the southern Appalachian Mountains hold more plant taxa than any others in North America. Plant genera such as Cornus (dogwoods), Asarum (wild ginger), and various conifers (Pinus, Abies, Thuja, Chamaecyparis) grow a continent apart while providing a comparative glimpse of an ancient flora.
What follows is a pictorial comparison of a few of the plants we saw this summer in the southern Appalachians compared to a Klamath Mountain relative.
Appalachian plants on the left and Klamath plants on the right
The first comprehensive regional natural history is here!
Edited by Michael Kauffmann and Justin Garwood.