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Post glacial vegetation and climate change in Western Southland

Marcus J Vandergoes
Department of Geography, University of Otago, Dunedin, New Zealand

 
Abstract

Pollen diagrams from three peat bogs in western Southland record the vegetation and climate history of the last 12,600 years. Lake glacial to early Holocene vegetation at three sites consisted of grassland-shrubland communities although trees and tree ferns are recorded at one of the sites. These vegetation associations indicate that a cool, low rainfall climate occurred over western Southland during the late Glacial period. Between 9200 and 8600 years BP a coniferous forest of Prumnopitys taxifolia, Dacrycarpus dacrydioides, Prummnopitys ferruginea, and several species of Podocarpus replaced grassland-shrubland communities at lower altitudes, while a coniferous scrub of Phyllocladus alpinus and Halocarpus bidwillii replaced glassland-shrublands at higher altitudes. This expansion of podocarp forest during the early Holocene is likely to be a result of an ameliorating climate, with increasing temperature and rainfall. Nothofagus menziesii became an important component of higher altitude forests by 5000 years BP, and by ca. 4200 years BP it had spread into lowland areas. N. solandri var. cliffortioides forest began to replace the Nothofagus menziesii forest at higher altitudes after ca. 2900 years BP, although it was not until ca. 2200 years BP that this forest expanded into lowland areas. The change in vegetation composition to a Nothofagus dominated forest is likely to be the result of climate deterioration, with decreasing temperatures and increasing rainfall. From 750 years BP Polynesian followed by European burning and forest clearance destroyed the lowland forest communities which were replaced by grasslands. Although some vegetation changes are asynchronous, climate change is the most important forcing mechanism underlying late glacial and Holocene vegetation change in western Southland. Non-synchronous vegetation changes identified by this study are likely to be associated with variations in site characteristics.

 
Reference

Vandergoes, M. 1996. Post glacial vegetation and climate change in western Southland. Unpublished MSc thesis, in Geography, at the University of Otago, Dunedin, New Zealand. 149 pp.

© 2009 Department of Geography, University of Otago, Dunedin, New Zealand