A pre‐deforestation pollen‐climate calibration model for New Zealand and quantitative temperature reconstructions for the past 18 000 years BP

Abstract

Wilmshurst, J. M., McGlone, M. S., Leathwick, J. R. and Newnham, R. M. 2007. A pre-deforestation pollen-climate calibration model for New Zealand and quantitative temperature reconstructions for the past 18 000 years BP.ABSTRACT: Quantification of modern pollen rain-vegetation-climate relationships in New Zealand has been complicated by human destruction of at least 75% of the original forest cover since ca. 750 years BP, causing contemporary pollen rain over large areas to bear little resemblance to the pre-human vegetation. We use a pre-deforestation pollen database to circumvent this complication. The relationships between the pre-deforestation pollen assemblages and six climatic variables were explored using principal components analysis and constrained regressions (redundancy analyses). Quantitative estimates of the most significant climate variable (mean annual temperature) were made at seven lowland to montane fossil pollen sites from throughout New Zealand using the modern analogue technique and a transfer function. These showed an initial increase in mean annual temperature after 18 000 cal. yr BP, a cooling at the time of the Antarctic Cold Reversal (centred on 13 500 cal. yr BP) and continuation of warming from ca. 12 000 cal. yr BP across the Younger Dryas chronozone, reaching a Holocene thermal optimum that may have been between 1.5 and 38C warmer than present and lasted from 9000 to 7000 cal. yr BP depending on the site. Cooling to present-day temperatures was well advanced by 4000-3000 cal. yr BP.

Cooling and changing seasonality in the Southern Alps, New Zealand during the Antarctic Cold Reversal

“…Cooling centered on 13,600 cal yr BP is also shown by mean annual air temperature estimates from a recently developed pollen-temperature calibration model (Wilmshurst et al, 2007). These records provide strong evidence of a regional climate cooling event.…”

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

“…We note that near-Holocene temperatures were reached in many parts of eastern New Zealand by about 14,000 years ago (Turney et al 2003). An early-Holocene thermal optimum, between 1.5°C and 3°C warmer than present, is suggested for the New Zealand region from about 9000 to 7000 yr BP (Weaver et al 1998;Wilmshurst et al 2007).…”

“…Tree ferns form a particularly low component of the total (0.7 ± 1.1%) and conifer trees make up 2.8 ± 7.2%, while 88% of all the forest pollen recorded is of Nothofagus. This is a strong contrast with modern late-Holocene pre-deforestation assemblages (135 sites distributed throughout New Zealand; Wilmshurst et al 2007), which average c. 80% tree pollen from conifer (c. 44%) or angiosperm (c. 35%) sources, c. 7% from tree ferns, and low amounts from herbaceous (c. 4%) or shrub (c. 17%) sources.Turning to regional distinctions, some broad patterns are evident. Four northern sites suggest a nearly complete forest cover north of Auckland at the LGM.…”

“…We note that near-Holocene temperatures were reached in many parts of eastern New Zealand by about 14,000 years ago (Turney et al 2003). An early-Holocene thermal optimum, between 1.5°C and 3°C warmer than present, is suggested for the New Zealand region from about 9000 to 7000 yr BP (Weaver et al 1998;Wilmshurst et al 2007).At Prospect Hill (13 km north and 470 m lower), low-montane forest replaced shrubland at 10,000 yr BP. However, forest arrival at Staces Tarn challenges the presumed early-Holocene warmer temperatures, as trees are not dominant at the site until 7500 yr BP.…”

Calibrating vascular plant abundance for detecting future climate changes in Oregon and Washington, USA

“…More recently, Garbolino et al (2007) Finsinger et al, 2007;Li et al, 2007;Neumann et al, 2007;Wilmshurst et al, 2007;St. Jacques et al, 2008).…”