Plant Migrations and Vegetational History of the Southern Appalachian Region

Resumo

The author attempts, for the first time, a chronological account of the different plant migrations, which have resulted in the present flora characteristic of the mountainous regions of the southern Appalachians. It studies the groups of flora and plant migrations that appear to have participated in the evolution of the modern flora of the southern Appalachians, and which are the following:

1) The ancient Paleozoic tlora, composed mainly of Pteridophytes and Pteridosperms, was modified, during the Appalachian Revolution, by the extermination and evolution of forms, to the primitive Mesozoic vegetation.

2) The almost flat Appalachian region was invaded in the early Cretaceous times by the new development and rapid spread of Angiosperms, which were then tropical in their distribution.

3) At the end of the Mesozoic era, the uprising caused the migration of these tropical forms towards the coastal plains that had recently emerged, leaving however numerous colonies, vestiges in the Appalachians.

4) The new high mountains were occupied by the arctotertiary forests, which were then circumboreal in extension, but are now limited to small geographically widely separated regions.

5) In the last Cenozoic era, the climates that became colder, caused the segregation of the originally homogeneous arctoterciary flora, in a coniferous forest in the north and a perishable forest in the south.

6) The Pleistocene glaciation caused migration to the southern mountains in many ways from the north.

7) The retreat of the ice allowed the migration of the coniferous forests to the north, reoccupying their original area, but leaving an extensive residue in the higher and colder southern Appalachian regions.

Note that the individual work of many botanists will be required to fill in the gaps and supply evidence to modify the hypothesis discussed here.