Pollen and sediment analysis of two Holocene cores from Awana, Great Barrier Island, shows that at 7000 calibrated yr B P the local swamp was an estuanne salt marsh dominated by Restionaceae By c 6000 yr B P the water table was lower, and a fresh water swamp (Gleichenta-Leptospermum) had replaced the salt marsh Regional coniferhardwood forest c 7000 yr B P was initially co-dominated by Libocedrus and Dacrydmm cupressinum Libocedrus declined from c 6000 yr B P During the period c 6000-c 2500 yr B P , relatively stable environmental conditions ensued with little change in local or regional vegetation Around 2500 yr B P , the swamp surface became drier and was invaded by Dacrycarpus and Laureha swamp forest This forest was subsequently repeatedly disturbed (not by fire), indicating climatic change to drier and windier conditions Ascanna lucida was periodically a major component of swamp forest Disturbance is also recorded in the clastic (mineral) sediments, where beds of sand within finer-grained sediment and peat are interpreted as wind blown material derived from partly devegetated dunes to seaward The presence of the Kaharoa Tephra allows the timing of major Polynesian deforestation at Awana to be reliably dated to c 600 calibrated yr B P In contrast, we see no evidence in the clastic sediment record of disturbance at Awana since Kaharoa time We attribute this to the maintenance of stable dunes by a herb/scrub cover despite nearby fires, or to the presence of scrub or forest buffering the swamp from ablating dunes
We show results of palynological and phytolith analysis of coprolites from Harataonga Bay, Great Barrier Island. Because human and dog diets may overlap considerably, the microfossil evidence does not with certainty indicate which of these two species deposited them. The coprolites give insights into prehistoric Maori agriculture, gathering of wild plants, diet, and time of year of site occupation. Gourd (Lagenaria siceraria) pollen found in the coprolites shows that this exotic cultigen was being cultivated in the area at the time. The presence of this taxon together with putative truffle spores in the coprolites suggests subsistence components involving both plant domestication and the gathering of wild plants.
Aim To reconstruct the history of a Holocene sand dune using pollen and phytolith analyses, and to identify the strengths, weaknesses and compatibility of these two methods in the interpretation of Quaternary coastal environments.
Location Great Barrier Island, northern New Zealand.
Methods Pollen and phytolith analyses were carried out on a sequence through a Holocene sand dune containing a palaeosol.
Results Phytoliths were present throughout the sequence. Grass phytoliths increased at the expense of tree phytoliths following fire disturbance. Pollen (and spores) was preserved only in the palaeosol part of the profile. Pteridium 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 phytolith analysis to defining only broad vegetation types. In New Zealand, gymnosperms are invisible in the phytolith record and ferns are extremely under‐represented. In contrast, pollen analysis usually provides a great deal of information regarding the composition of a particular vegetation type. The loss of microscopic charcoal fragments during the phytolith extraction process 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 preserved. The phytolith record may also provide evidence of wetter environments that are not apparent in the pollen record. Unlike grass pollen, which is widely dispersed and therefore blurs the spatial record, the presence of grass phytoliths in sediments indicates a local source. The simultaneous application of both methods potentially provides a powerful tool in ecological interpretation and the reconstruction of Quaternary coastal environments.
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