Early Paleogene vegetation units of East Asia and their spatial distribution

Abstract

Early Paleogene vegetation units and their spatial distribution are reconstructed from the palaeobotanical record originating from 73 East Asian localities. A total of 79 microfloras and 31 macrofloras compiled from published sources are analyzed using diversity of plant functional types (PFTs). The spatial patterns obtained from the diversity of PFTs reflect the distribution of major early Paleogene ecosystems. As shown by the analysis different forest associations were most important with trees reaching over 50% of the total diversity in 96% of the localities. Using a data matrix with single PFTs, cluster analysis is performed to interpret the ecospectra of the fossil sites in terms of vegetation units according to their characteristics. As a result, the early Paleogene sites are allocated to four major groups including five subgroups, which can be interpreted in terms of seven vegetation units. The distribution of the units is shown on palaeogeographical maps. The early Paleogene vegetation cover in the study area fundamentally differed from modern, being much more homogeneous and thermophilous. In the early Paleocene, the dominant type of vegetation is typical mixed mesophytic forest (MMF). In the late Paleocene, a pronounced zone of MMF with diverse conifers appeared in high latitudes, the middle latitudes occupied by evergreens and typical MMF. In the early Eocene, MMF with diverse broadleaved evergreens and typical MMF are widespread and dominant. Early Eocene microfloras differ from Paleocene microfloras in the higher participation of temperate warm trees and in their higher contents in tropical PFTs. The early Eocene MMF with diverse evergreens thriving in the high and middle latitudes of East Asia is not equivalent to modern tropical vegetation and can be characterized as extra-tropical, based on the interpretation of their ecospectra. The reconstructed vegetation patterns are well in accordance with results obtained from the climate reconstructions indicating the existence of very warm high latitudes and a shallow latitudinal temperature gradient during the early Paleogene.