A 6 ka BP Reconstruction for the Island of Newfoundland from a Synthesis of Holocene Lake-Sediment Pollen Records

Abstract

A 6 ka reconstruction for the island of Newfoundland is presented in the context of a synthesis of Holocene pollen records for twelve sites within or at the margin of the boreal forest, five of which are new. Climatic reconstruction is based primarily on representation of the major boreal taxa: balsam fir, spruce, birch and pine, with charcoal data for some sites. The period of greatest Holocene warmth began at 6 ka. Although temperatures at inland sites were at or close to modern values as early as 8.5-8.0 ka, it was not until 6 ka on the Avalon Peninsula, in the southeast, and 5.5 ka in the north, that coastal sites registered expansion of more thermophilous taxa. Thus oceanic warming lagged terrestrial warming. Temperatures during the period of greatest warmth were no more than 1.0°C higher than modern, based on fluctuations of the upper forest limit and post-Hypsithermal contraction of the range of indicator taxa. Fire importance increased after 6 ka as pine expanded, but moisture availability also increased. The first indications of cooling occurred on the coast at 4.5-4.0 ka, but at different times after 4.0 ka inland; thus oceanic cooling led terrestrial cooling. The latest Holocene has been cool, moist and relatively free from fire.La reconstitution a été faite à partir des données polliniques holocènes tirées de 12 sites (dont 5 nouveaux) situés à l'intérieur de la forêt boréale ou à sa marge. La reconstitution climatique est d'abord fondée sur la représentation des principaux taxons boréaux : le sapin baumier, l'épinette, le bouleau et de pin, avec données sur charbon à certains sites. La période la plus chaude de l'Holocène a commencé à 6 ka. Si les températures atteignaient les valeurs modernes ou en étaient près dès 8,5-8,0 ka à l'intérieur de l'île, ce n'était pas avant 6 ka dans la péninsule d'Avalon, au sud-ouest, et à 5,5 ka au nord que les sites côtiers ont enregistré l'expansion des taxons plus thermophiles. Ainsi, le réchauffement océanique a suivi le réchauffement terrestre. Les températures au cours de la période la plus chaude étaient plus élevés d'à peine 1°C que maintenant, évaluées sur la base des fluctuations de la limite altitudinale de la forêt et la réduction post-hypsithermale de la gamme des taxons indicateurs. L'importance des feux s'est accrue après 6 ka avec l'expansion du pin, mais l'humidité a aussi augmenté. Les premières indications d'un refroidissement se sont manifestées sur la côte vers 4,5-4,0 ka, et à différentes périodes après 4 ka à l'intérieur. Ainsi, le refroidissement océanique a entraîné le refroidissement terrestre. L'Holocène le plus récent a été frais, humide et relativement exempt de feux de forêts.Die Rekonstruktion wird im Kontext der Synthèse von Holozân-Pollenbelegen von zwôlf Plâtzen innerhalb oder am Rand des nôrdlichen Nadelwaldgùrtels vorgestellt, von denen fùnf neu sind. Die Klima-Rekonstruktion stùtzt sich vor allem auf das Vorkommen der hauptsàchlichen borealen Taxa: Balsam-tanne, Fichte, Birke und Kiefer, mit Kohledaten fur manche Plàtze. Die wàrms...

Unravelling the past to manage Newfoundland’s forests for the future

“…If this hypothesis holds true, it would imply that red pine populations are not in a steady state and would be expected to go through major shifts in abundance and extent through time mediated by the spatial and temporal distribution of fire. This idea of fluctuation of pine populations and fire through time is also consistent with the paleobotanical history of the Holocene by Macpherson (1995). This hypothesis may also hold true for other red pine populations on the mainland and is consistent with observations of Flannigan and Bergeron (1998).…”

“…However, moisture in this area is not as evenly distributed as the western region and is more subject to sporadic high fire hazards. These observations are corroborated by charcoal records from paleobotanical studies (Macpherson 1995 et al (1983) suggested that Abies forests were less flammable than spruce forests, hence creating a feedback mechanism between species composition and fire occurrence. This pattern is clearly reflected in the distribution of balsam fir and black spruce in the less fire-prone region of western Newfoundland compared with central Newfoundland (Fig.…”

Late Quaternary Vegetation History of Northern North America Based on Pollen, Macrofossil, and Faunal Remains*

“…Spruce and fir also predominated in Newfoundland, where larch appears to have become more important than previously. White pine, red pine (Pinus resinosa), and ash -all thermophilous and evidently never abundant in Newfoundland -appeared at this time and attained their greatest abundance during the next 2000 years (Macpherson, 1995). White and black spruce remained exceedingly common in the western boreal forest, though jackpine may have increased somewhat in Saskatchewan and Manitoba (Nichols, 1967;Mott, 1973;Ritchie and Haden, 1975;Ritchie, 1976Ritchie, , 1980Ritchie and Yarranton, 1978;Wilson, 1981;Dredge and Mott, 2003).…”

A Canadian Contribution to the Paleoclimate Model Intercomparison Project (PMIP)

“…From Newfoundland, Macpherson (1995) reconstructs conditions no more than 1.5°C warmer than today and higher forest fire frequencies 6000 yr BP. She also observes a lag in the oceanic warming, as compared with the terrestrial warming.…”