Holocene vegetation and climate of Stewart Island, New Zealand.
Stewart Island is the southernmost of the three main New Zealand islands, and is largely covered with Dacrydium cupressinum/hardwood forest. Pollen analyses from three Holocene sites and a modern pollen rain survey are presented. Stewart Island had a hardwood forest of Weinmannia racemosa, Metrosideros umbellata, and abundant tree ferns from before 9000 BP to 5500-4500 BP when Dacrydium cupressinum and Prumnopitys ferruginea rose to dominate the forest reducing the abundance of Weinmannia racemosa and greatly restricting Metrosideros umbellata. It is suggested that mild, cloudy climates during the early Holocene may have inhibited regeneration of podocarp trees, and that a change in climatic regime in the mid to late Holocene brought sunnier, less cloudy conditions. Several woody species absent from the island but present on the adjacent mainland (Phyllocladus alpinus, Nothofagus spp., Libocedrus bidwillii) probably never grew there, and their absence is attributed to failure to disperse and the limited time that suitable habitats have been available.