Bøger af Daniel I. Axelrod

The Pyramid flora (15.8 m. years) is wholly dominated by broadleaved deciduous hardwoods of eastern alliance that indicate ample summer rain. Deciduous hardwoods are largely absent from slightly younger nearby floras (less than 15.8 m. years) that are dominated by mixed conifer and broadleaved evergreen forest species. The change is attributed to reduced summer rain that reflects global climatic change influenced by spreading antarctic ice.

A study of the Miocene Carmel flora of California, an evergreen laurel-oak forest that grew in a mild temperate, frost-free climate, with annual precipitation of about 760mm.

Oligocene Haynes Creek flora of Eastern Idaho of 70 species is dominated by deciduous trees, many with descendants in China. Comparison with the Horse Prairie flora, 30 miles east and across the present continental divide, indicates that the divide was then low and discontinuous, with warmer climate to the east.

An Eocene (45 Ma) flora from Thunder Mountain caldera shows that montane conifer forest species from upper slopes descended to interfinger with mixed conifer-deciduous hardwood forest on the caldera floor then near 1700m. Most species are allied to those in the USA, but a few genera are in China.