Browsing by Author "Lees, Cynthia M"
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- ItemLate holocene changes in the vegetation of Western Taranaki investigated by soil palynology : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University(Massey University, 1987) Lees, Cynthia MThe study area in western Taranaki is dominated by the andesitic volcano, Mount Egmont.Palynological study of 22 fossil pollen sites from a vide range of sediments has produced evidence of change in vegetation over last 4000 years.The resilience of the indigenous vegetation ensured survival of temperate lowland forests until the arrival of European settlers about 150 years ago.Within this period,deforestation of the lowlands has been almost complete.Surviving forest is protected within Egmont National Park. There is little evidence of pre-European deforestation,but indications of earlier fires are thought to be due to an increase in the Maori diet of Pteridium rhizomes,dictated by a change of climate about 400yr B.P. Information has been gained in general terms about the effects of older tephras and in detail about damage and recovery after tephras deposited within the last 400 years.A revised tephrochronology for the last 400 years is offered. Palynological evidence suggests that an equable climate existed between 4000-1400yr B.P. A decline of Ascarina from very high values at this time to low values at 400yr B.P. has been interpreted as due to a prevalence of droughts.Since 400yr B.P. the climate has been wetter and cooler.This, together with the availability of newly exposed sites due to volcanic activity,has resulted in a dominance of Weinmannia in the Mount Egmont forests. Such dominance is not seen in pollen profiles of older sites over the last 4000 years.
- ItemSome aranuian (postglacial) organic deposits in the south eastern Ruahine Range, North Island, New Zealand, investigated by palynological methods : a thesis presented in partial fulfilment of the requirements for the Degree of Master of Science in Geography at Massey University(Massey University, 1981) Lees, Cynthia MPalynological methods have been used to investigate Aranuian organic deposits in the south eastern Ruahine Range. The relevant literature was reviewed. Six profiles from five sites ranging in altitude from 80 to 1050 metres and from 13,300 years B.P. to present were sampled and the pollen analysed. Investigation of the palaeoecology of each site included the geomorphology, stratigraphy, present vegetation and pollen rain where relevant. The pollen data as percentages of several pollen sums was presented in pollen diagrams, statistically analysed and an interpretation suggested. An investigation of pollen rain in the Kahuterawa Valley in the Tararua Range and on Mount Ruapehu was made to obtain information on present podocarp-broadleaf forests and about Weinmannia racemosa in particular. The results indicated a succession of dominants, including W. racemosa over a period of up to 1000 years. This information was used in interpreting the pollen spectra of the fossil sites. All sites were reviewed as part of an Aranuian series. It was concluded that a climatic change from a drier cooler climate to a warmer moister one occurred between 13,300 ± and 10,650 (provisional date only). A more equable climate than at present possibly occurred between 3200 ± and 3770 ± with fewer frosts and droughts.These findings are in general agreement with those of palynologists at sites in other parts of New Zealand. Other aspects of climatic change erosional history, plant-land relationships and species representation have been discussed. The decline of W. racemosa at the West Tamaki site was part of a natural stage in the life cycle and not caused by the browsing of the opossum.