South-east Nelson at the northern end of the Southern Alps was extensively glaciated during the Last Glacial Maximum. For areas not covered by ice the pollen record shows that grassland was the plant cover. Below 500 m a.s.l. and to the west there were refuges of beech (Nothofagus). When the ice retreated, after 12 000 C-14 yr B.P. grassland was colonised by shrubland dominated by Halocarpus and Phyllocladus. By 8000 C-14 yr B.P. beech forest was migrating from refuges into the shrubland by discontinuous population advance. West of the mountains, in the Lake Rotoiti-Lake Rotoroa area, beech forest was established by 6000 C-14 yr B.P. Forest then advanced up the river valleys, into the Southern Alps, to give today's nearly continuous beech forest cover. The process is not yet complete, and grassland on the eastern side is still being colonised by beech.