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This flora of 70 species is dominated by deciduous trees, many with
descendants in China. Precipitation was 890 mm, mean annual
temperature 12.5 C, the annual range 10 C, and freezing rare.
Elevation was about 1000 meters. 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.
This is a study of the Miocene Carmel flora of California, an
evergreen laurel-oak forest that grew in a mild temperate (mean
annual temperature of 15 degrees C), frost-free climate, with
annual precipitation of about 760 mm (30 in.). Collectively, the
Carmel and other Miocene floras like the San Pablo and Temblor
(broad-leafed deciduous trees, with few evergreen species), the
Puente (evergreen oak forest with chaparral species), the Mint
Canyon, Ricardo, and Tehachapi (numerous arid subtropical scrub
associated with oak woodland and chaparral species) suggest they
foreshadowed a similar distribution of the different California
vegetation zones today.
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 1700 m. Most species are allied to those in
the western United States, but a few genera are in China.
Precipitation was near 100 cm yearly, with most in summer.
In this study, nine florules from the Chloropagus Formation near
Fernley, Nevada, are dated at 14.7-13.4 million years. The author
finds that dominant mixed conifer forest and sclerophyll woodland
species of the Sierra Nevada-Klamath region replaced exotic
deciduous hardwoods in the two lowest sites. He concludes that this
change reflects the loss of adequate summer rain as upwelling from
a colder ocean resulted from spreading East Antarctic ice.
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