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Evidence for Lateglacial and Holocene tree-line fluctuations from pollen diagrams from the Subalpine zone on Mt Hauhungatahi, Tongariro National Park, New ZealandCentre for Archaeological Research, New Zealand
School of Environmental and Marine Sciences, University of Auckland, Private Bag 92-019, Auckland, New Zealand Pollen diagrams from four sites along an altitudinal sequence on Mt Hauhungatahi support fossil wood data (Ogden et al., 1997) in suggesting a fluctuating Holocene tree-line not exceeding the altitude reached in the early Holocene. Tree-line forest at 13401390 m during the periods 10 1007500 and 54003800 cal. BP was associated with patchy Subalpine scrub communities above and below this altitude. Rapid decline of this Halocarpus-Phyllocladus forest at c. 7500 cal. BP, and again c. 3800 cal. BP was probably due to volcan ism. During 75005400 and 38001718 cal. BP tree-line forest was replaced by Subalpine scrub. The failure of forest to replace scrub during these two periods implies a long-lasting influence of the event which destroyed the forest, a continuation of disturbance events, or changed environmental conditions. After the Taupo volcanic eruption (1718 cal. BP) expansion of Libocedrus indicates an upwards movement of forest species into Subalpine scrub, followed by a decline. Volcanism has probably affected the vegetation of Mt Hauhungatahi directly and indirectly (through effects on soil drainage) throughout the Holocene. Results are consistent with increased climatic variability since 7500 cal. BP, and support the hypothesis that disturbance events can have persistent long-term effects on community composition and species distribution patterns.
Key Words: Palynology Lateglacial Holocene tree-line disturbance volcanism Taupo Tephra eruption Tongariro National Park
The Holocene, Vol. 10, No. 1,
61-73 (2000) This article has been cited by other articles:
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