A reconstruction of the history of a Holocene sand dune on Great Barrier Island, northern New Zealand, using pollen and phytolith analyses

Aim To reconstruct the history of a Holocene sand dune using pollen and phy tolith analyses, and to identify the strengths, weaknesses and compatibilit y of these two methods in the interpretation of Quaternary coastal environm ents. Location Great Barrier Island, northern New Zealand. Methods Pollen and phytolith analyses were carried out on a sequence throug h a Holocene sand dune containing a palaeosol. Results Phytoliths were present throughout the sequence. Grass phytoliths i ncreased at the expense of tree phytoliths following fire disturbance. Poll en (and spores) was preserved only in the palaeosol part of the profile. Pt eridium fern spores increased at the expense of tall tree pollen following the fire disturbance. Main conclusions Lack of phytolith production by many species and problems of taxonomic specificity in many others restricts the usefulness of phytoli th analysis to defining only broad vegetation types. In New Zealand, gymnos perms are invisible in the phytolith record and ferns are extremely under-r epresented. In contrast, pollen analysis usually provides a great deal of i nformation regarding the composition of a particular vegetation type. The l oss of microscopic charcoal fragments during the phytolith extraction proce ss is a disadvantage in the reconstruction of environments where fires have occurred. The greater durability of phytoliths compared with pollen means that phytoliths may be found in sediments where pollen has not been preserv ed. The phytolith record may also provide evidence of wetter environments t hat are not apparent in the pollen record. Unlike grass pollen, which is wi dely dispersed and therefore blurs the spatial record, the presence of gras s phytoliths in sediments indicates a local source. The simultaneous applic ation of both methods potentially provides a powerful tool in ecological in terpretation and the reconstruction of Quaternary coastal environments.