Paleogene vegetation of Eurasia: framework for mammalian faunas
Deinsea , Volume 10 - Issue 1 p. 41- 84
Eurasia is plotted on polar projections of paleogeographic maps. Methods and approaches for reconstructing Paleogene plants and vegetation from fossil floras are briefly outlined. Paleocene and Eocene polar, broad-leaved deciduous forests occurred in the high paleolatitudes and up to the edge of the Arctic Ocean. Relative to subsequent paratropical forests these were very low diversity forests with little habitat variation, very few climbers and more open structure. The environment was warm and equable but with up to three months of winter darkness so that most herbivorous browse and the small, dry fruits and seeds would only have been available seasonally. Late Paleocene and Eocene broad-leaved paratropical to subtropical, evergreen forests are variable in time and space. The most evergreen thermophilic forests are documented in Europe and southern China associated with the Eocene thermal maximum. These forests were highly diverse, multistratal, rich in climbers, with closed structure and would have provided many varied habitats. They would have provided year round herbivorous browse of medium to large evergreen leaves and a wide variety of fruits, including many fleshy fruits. Late Eocene and Oligocene broad-leaved mixed deciduous and evergreen forests developed as climate changed following the thermal maximum from the late Middle Eocene and through the Oligocene. These forests had lower diversity, contained fewer lianas and climbers and would have had a more open structure than the paratropical forests. They would have provided a mixture of evergreen and deciduous leaf browse and a variety of fruits but with fewer fleshy fruits and more large dry fruits. Vegetation with sclerophyllous elements was variably developed in central China, through Kazakhstan and the tethyan islands and into eastern Europe in the Eocene. In the Oligocene it was well-developed in southern Europe and also occurred in Kazakhstan. This vegetation reflects a warm humid temperate climate but with a slightly drier interval where sclerophyllous elements become significant in abundance or diversity. This would have been dominantly a forest vegetation (possibly shrubland in places) but with relatively open structure. In the most sclerophyllous belts, such as the Oligocene of southern Europe, herbivorous browse would have consisted mainly of relatively tough small leaves and the fruits and seeds would have been mainly dry with tough outer coverings. This paper paints only a very general picture of Paleogene vegetation. Paleogene floras provide the potential for detailed interpretation of vegetational, and hence biome, response to global change such as warm climate thermal maxima and tectonic events. Realising this potential requires independent dating of more fossil floras, new physiognomic analyses, rigorous re-investigation of nearest living relative assessments and integrated palynological and macrofossil studies which take account of taphonomic bias.