Holocene palaeoecology and climate history of South Georgia (sub-Antarctica) based on a macrofossil record of bryophytes and seeds

Abstract

The results are presented of a detailed plant macrofossil analysis of a 14C dated Holocene organic sequence from a sub-Antarctic island, South Georgia. In the peat infilling of a rock basin 31 bryophyte species and many of the principal species of the present-day angiosperm flora, associated with bog communities, have been identified. The zonation of the bryophytes and the seeds and fruits shows a striking correspondence with the sediment stratigraphy, and indicates five ecological phases. The first four reflect a succession from a minerotrophic shallow pool to an ombrotrophic Warnstorfia-Polytrichum bog. After the deposition of a greyish-brown layer, c. 2200 14C years BP, a wet Deschampsia-Warnstorfia-Sanionia-Rostkovia bog came into existence, which is still present today. The ecological phases are radiocarbon dated. They can be interpreted in terms of climate development during the Holocene. Climate ameliorated rapidly at about 10 000 14C years BP followed by a drier period. Around 7000 14C years BP the climate became wetter and the following c. 2500 years probably represent the climatic optimum. Between 4500 and 2600 14C years BP, drier conditions prevailed at the study site. The most striking change occurred at 2600 14C years BP when a marked change in vegetation and ecology indicates much wetter conditions.