Eocene vegetation patterns reconstructed from plant diversity — A global perspective

Abstract

Eocene vegetation patterns and continental temperatures are reconstructed from the palaeobotanical record on a global scale. A total of 100 macrofloras and 45 microfloras compiled from published sources is analysed studying diversities of plant functional types and phytosociological types. The spatial patterns obtained from the diversity of plant functional types reflect the distribution of major Eocene ecosystems. As shown by the analysis different forest associations were most important with trees reaching over 50% of the total diversity in 92% of the localities. Using a phytosociological classification scheme employing the ecological requirements of the Nearest Living Relatives of fossil taxa the single floras are analysed by multivariate statistical methods. As a result the Eocene sites are allocated to 7 different groups which can be interpreted in terms of Eocene vegetation units. The distribution of these units is shown in palaeogeographical maps. It is shown that in the Eocene, major vegetation units were zonally arranged. Most of the floras located north and south of 15° latitude are classified as extra-tropical. There is evidence for seasonally drier climate conditions in some regions, but no indication for xerophytic vegetation types. The vegetation of the mid-latitudes is characterized by a very high diversity of evergreen angiosperm woods, especially in the Tethyan realm. The high Northern latitudes were covered by temperate deciduous and mixed deciduous vegetation. The reconstructed vegetational patterns are well in accordance with results obtained from the analysis of various proxy data indicating the existence of very warm high latitudes and a shallow latitudinal temperature gradient during the Eocene.