Palynology and Paleoecology of Postglacial Sediments from the Lower Fraser River Canyon of British Columbia

1975 ◽  
Vol 12 (5) ◽  
pp. 745-756 ◽  
Author(s):  
R. W. Mathewes ◽  
G. E. Rouse
Keyword(s):  
Tsuga Heterophylla ◽  
Climatic Conditions ◽  
Douglas Fir ◽  
Fraser River ◽  
Pollen Assemblage ◽  
Glacial Ice ◽  
Transitional Area ◽  
Postglacial History ◽  
History Of Vegetation ◽  
History Of

The postglacial history of vegetation in the Yale area of the lower Fraser River Canyon is described from sediments of two lakes using percentage pollen analysis supplemented with macrofossil evidence and radiocarbon dating. Deposition of postglacial sediments, ranging from basal clays to gyttjas, began about 11 500 y B.P. Three distinct pollen assemblage zones are distinguished, reflecting in part the main climatic conditions for the intervals. The oldest zone, with high percentages of pine (Pinus) and alder (Alnus) pollen, suggests cool and moist conditions following withdrawal of glacial ice. This is followed by marked increases in Douglas-fir (Pseudotsuga), grasses and other nonarboreal pollen, suggesting in part, warmer and drier conditions. The third zone, ranging from about the Mt. Mazama ash at 6600 y B.P. to the present, is marked by high alder and Douglas-fir, and increasing cedar (Thuja-Chamaecyparis type), western hemlock (Tsuga heterophylla), fir (Abies) and birch; an assemblage indicating a return to wetter conditions. This sequence contrasts with previously described successions that recognized the classical Hypsithermal in adjacent areas. The sequence of inferred vegetational changes, although similar to those described for the Haney area to the west, suggests that the Yale area has been a biogeoclimatically transitional area for much of postglacial time.

Canopy disturbances over the five-century lifetime of an old-growth Douglas-fir stand in the Pacific Northwest

2002 ◽  
Vol 32 (6) ◽  
pp. 1057-1070 ◽  
Author(s):  
Linda E Winter ◽  
Linda B Brubaker ◽  
Jerry F Franklin ◽  
Eric A Miller ◽  
Donald Q DeWitt
Keyword(s):  
Pacific Northwest ◽  
Variable Density ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Old Growth ◽  
The Pacific ◽  
History Of ◽  
Horizontal Heterogeneity ◽  
Restoration Strategies

The history of canopy disturbances over the lifetime of an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand in the western Cascade Range of southern Washington was reconstructed using tree-ring records of cross-dated samples from a 3.3-ha mapped plot. The reconstruction detected pulses in which many western hemlock (Tsuga heterophylla (Raf.) Sarg.) synchronously experienced abrupt and sustained increases in ringwidth, i.e., "growth-increases", and focused on medium-sized or larger ([Formula: see text]0.8 ha) events. The results show that the stand experienced at least three canopy disturbances that each thinned, but did not clear, the canopy over areas [Formula: see text]0.8 ha, occurring approximately in the late 1500s, the 1760s, and the 1930s. None of these promoted regeneration of the shade-intolerant Douglas-fir, all of which established 1500–1521. The disturbances may have promoted regeneration of western hemlock, but their strongest effect on tree dynamics was to elicit western hemlock growth-increases. Canopy disturbances are known to create patchiness, or horizontal heterogeneity, an important characteristic of old-growth forests. This reconstructed history provides one model for restoration strategies to create horizontal heterogeneity in young Douglas-fir stands, for example, by suggesting sizes of areas to thin in variable-density thinnings.

A postglacial history of vegetation and bog formation at Point Escuminac, New Brunswick

1991 ◽  
Vol 28 (10) ◽  
pp. 1572-1582 ◽  
Author(s):  
Barry G. Warner ◽  
Kimmo Tolonen ◽  
Mirjami Tolonen
Keyword(s):  
New Brunswick ◽  
Radiocarbon Dating ◽  
Coniferous Forests ◽  
Postglacial History ◽  
History Of Vegetation ◽  
Ombrotrophic Bog ◽  
History Of ◽  
Northern Edge ◽  
Woodland Communities

Radiocarbon dating and analyses of fossils contained in peat cliffs establish the history of peatland formation and development at the northern edge of Point Escuminac, New Brunswick. A 532 cm radiocarbon-dated mineral sediment and peat sequence, the oldest of four sections studied, yielded pollen and macrofossils that record bog development from 11 000 BP. The earliest landscape was open Juniperus shrubland. Picea was the first tree to move into the area, forming woodland communities by 10 200 BP and closed coniferous forests with Abies by 9200 BP. An early counterpart of the modern Acadian forests was in place by 6500 BP and was fully developed by 2900 BP when Fagus spread through the area. Shallow freshwater, open wetland communities acted as nuclei for the development of fen near the centre of the peninsula. Transformation into an ombrotrophic bog started around 6500 BP and was completed by 4700 BP, after which time the bog spread laterally by paludification onto higher parts of the peninsula.

scholarly journals Postglacial history of vegetation, human activity and lake-level changes at Jezioro Linówek in northeast Poland, based on multi-proxy data

2013 ◽  
Vol 23 (2) ◽  
pp. 123-152 ◽  
Author(s):  
Mariusz Gałka ◽  
Kazimierz Tobolski ◽  
Edyta Zawisza ◽  
Tomasz Goslar
Keyword(s):  
Human Activity ◽  
Lake Level ◽  
Proxy Data ◽  
Lake Level Changes ◽  
Postglacial History ◽  
History Of Vegetation ◽  
History Of

Holocene vegetation, climate, and lake-level changes in the Interior Douglas-fir Biogeoclimatic Zone, British Columbia

1989 ◽  
Vol 26 (9) ◽  
pp. 1811-1825 ◽  
Author(s):  
Rolf W. Mathewes ◽  
Miriam King
Keyword(s):  
British Columbia ◽  
Tsuga Heterophylla ◽  
Climatic Conditions ◽  
Douglas Fir ◽  
Sediment Type ◽  
Stratigraphic Correlation ◽  
Study Region ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Pollen Influx

Chilhil, Phair, Fishblue, and Horseshoe lakes in the southern interior of British Columbia were cored and analyzed for pollen. Phair Lake was also examined for plant macrofossils and aquatic molluscs. Two dated volcanic tephras (Mazama and Bridge River) are present in three of the four lakes and, together with radiocarbon dates, provide an absolute chronology for pollen-influx calculations and stratigraphic correlation. Abrupt changes in sediment type at Phair Lake about 5650 and 2000 years ago correlate with Neoglacial advances near the coast–interior transition. Pollen changes suggestive of moister conditions and the presence of an aquatic mollusc (Valvata sincera helicoidea) at Phair and Chilhil lakes are consistent with the Neoglacial evidence of cooler and wetter conditions after about 2400 years ago. The driest part of the Holocene was the early, pre-Mazama (ca. 6600–6800 years ago) interval, when the vegetation was more open and herb rich and the lake levels were lower than at present. Wetter climatic conditions appear in post-Mazama time, indicated by regional increases in the pollen of Tsuga heterophylla and other coastal and subalpine trees. Pollen-influx values for the Interior Douglas-fir Zone are broadly consistent at all sites, with values of < 2000 –8000 grains cm−2 year−1. Douglas-fir (Pseudotsuga menziesii) has been an important forest species in the study region throughout the Holocene.

scholarly journals Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective from Kane Basin

2018 ◽  
Vol 14 (12) ◽  
pp. 1991-2010 ◽  
Author(s):  
Eleanor Georgiadis ◽  
Jacques Giraudeau ◽  
Philippe Martinez ◽  
Patrick Lajeunesse ◽  
Guillaume St-Onge ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Sediment Geochemistry ◽  
Glacial Ice ◽  
Isostatic Rebound ◽  
Nares Strait ◽  
Postglacial History ◽  
Marine Sedimentation ◽  
History Of ◽  
Ice Conditions ◽  
Insight Into

Abstract. A radiocarbon-dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that provide new insight into the evolution of ice sheet configuration in Nares Strait. Proglacial marine sedimentation at the core site initiated ca. 9.0 cal ka BP following the retreat of grounded ice. Varying contributions of sand and clasts suggest unstable sea ice conditions and glacial activity, which subsisted until ca. 7.5 cal ka BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. An interval rich in ice-rafted debris (IRD) is interpreted as the collapse of the ice saddle in Kennedy Channel ca. 8.3 cal ka BP that marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between ca. 8.3 and ca. 7.5 cal ka BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at about 8.1 cal ka BP as evidenced by a noticeable change in sediment geochemistry in our core. The gradual decrease in carbonate inputs to Kane Basin between ∼8.1 and ∼4.1 cal ka BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Reduced iceberg delivery from 7.5 to 1.9 cal ka BP inferred by our dataset may be linked to the retreat of the bordering ice sheets on land that decreased their number of marine termini.

Ecosystem development in the Girdwood area, south-central Alaska, following late Wisconsin glaciation

2010 ◽  
Vol 47 (7) ◽  
pp. 971-985 ◽  
Author(s):  
T. A. Ager ◽  
P. E. Carrara ◽  
J. P. McGeehin
Keyword(s):  
Picea Sitchensis ◽  
Coastal Forest ◽  
Postglacial History ◽  
South Central ◽  
Tundra Vegetation ◽  
History Of Vegetation ◽  
Clayey Silt ◽  
Birch Trees ◽  
History Of ◽  
Tsuga Mertensiana

Pollen analysis of two cores with discontinuous records from a peat bog near Girdwood, in south-central Alaska, provides the basis for reconstructing the first radiocarbon-dated outline of postglacial history of vegetation in the upper Turnagain Arm area of Cook Inlet. Pollen data from clayey silt underlying peat at one site indicate that the earliest known vegetation in the Girdwood area was shrub–herb tundra. Tundra vegetation developed by ∼13 800 cal years BP, soon after local retreat of glacial ice from the maximum position of the Elmendorf glacial advance (∼15 000 – 11 000 cal years BP). By ∼10 900 cal years BP, the tundra vegetation became shrubbier as Betula nana , Salix , and Ericales increased, and scattered Alnus shrubs began to colonize Turnagain Arm. By ∼9600 cal years BP, Alnus thickets with Polypodiaceae ferns became the dominant vegetation. By ∼6600 cal years BP, birch trees ( Betula neoalaskana , B. kenaica ) from the Anchorage and Kenai lowlands began to spread eastward into eastern Turnagain Arm. Mountain hemlock ( Tsuga mertensiana ) began to colonize the Girdwood area by ∼3400 cal years BP, followed soon after by Sitka spruce ( Picea sitchensis ), both Pacific coastal forest species that spread westward from Prince William Sound after a long migration from southeastern Alaska. For at least the past 2700 cal years, Pacific coastal forest composed mostly of Tsuga mertensiana , Picea sitchensis , and Alnus has been the dominant vegetation of eastern Turnagain Arm.

scholarly journals Deglacial to postglacial history of Nares Strait, Northwest Greenland: a marine perspective

2018 ◽  
Author(s):  
Eleanor Georgiadis ◽  
Jacques Giraudeau ◽  
Philippe Martinez ◽  
Patrick Lajeunesse ◽  
Guillaume St-Onge ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Sea Surface ◽  
Glacial Ice ◽  
Baffin Bay ◽  
Isostatic Rebound ◽  
Nares Strait ◽  
Postglacial History ◽  
Marine Sedimentation ◽  
Core Site ◽  
History Of

Abstract. A radiocarbon dated marine sediment core retrieved in Kane Basin, central Nares Strait, was analysed to constrain the timing of the postglacial opening of this Arctic gateway and its Holocene evolution. This study is based on a set of sedimentological and geochemical proxies of changing sedimentary processes and sources that translate into ice sheet configuration in the strait. Proglacial marine sedimentation at the core site initiated ca. 9.0 cal. ka BP following the retreat of grounded ice. Unstable sea surface conditions subsisted until 7.5 cal. ka BP under the combined influence of warm atmospheric temperatures and proglacial cooling induced by the nearby Innuitian (IIS) and Greenland (GIS) ice sheets. The collapse of the ice saddle in Kennedy Channel at 8.3 cal. ka BP marks the complete opening of Nares Strait and the initial connection between the Lincoln Sea and northernmost Baffin Bay. Delivery of sediment by icebergs was strengthened between 8.3 and 7.5 cal. ka BP following the collapse of the buttress of glacial ice in Kennedy Channel that triggered the acceleration of GIS and IIS fluxes toward Nares Strait. The destabilisation in glacial ice eventually led to the rapid retreat of the GIS in eastern Kane Basin at 8.1 cal. ka BP as evidenced by a noticeable change in sediment source in our core. The gradual decrease of carbonate inputs to Kane Basin between 8.1 and 4.1 cal. ka BP reflects the late deglaciation of Washington Land. The shoaling of Kane Basin can be observed in our record by the increased winnowing of lighter particles as the glacio-isostatic rebound brought the seabed closer to subsurface currents. Our dataset suggests reduced iceberg delivery from 7.5 to 1.9 cal. ka BP in relation to the Neoglacial cooling that likely enhanced sea ice occurrence, thus suppressing calving and/or the drifting of icebergs in Nares Strait.

Climate and local controls of long-term vegetation dynamics in northern Patagonia (Lat 41°S)

2012 ◽  
Vol 78 (3) ◽  
pp. 502-512 ◽  
Author(s):  
Virginia Iglesias ◽  
Cathy Whitlock ◽  
María Martha Bianchi ◽  
Gustavo Villarosa ◽  
Valeria Outes
Keyword(s):  
Late Holocene ◽  
Vegetation Change ◽  
Late Glacial ◽  
Fire Frequency ◽  
Forest Steppe ◽  
Ecological Change ◽  
Postglacial History ◽  
New Information ◽  
History Of Vegetation ◽  
History Of

AbstractPatagonian vegetation has dramatically changed in composition and distribution over the last 16,000 yr. Although patterns of vegetation change are relatively clear, our understanding of the processes that produce them is limited. High-resolution pollen and charcoal records from two lakes located at lat 41°S provide new information on the postglacial history of vegetation and fire activity at the forest–steppe ecotone, and help clarify the relative importance of local and regional drivers of late-Holocene ecological change. Our results suggest that late-glacial parkland was colonized by shrubs at ca. 11,200 cal yr BP and this vegetation persisted until 4900 cal yr BP, when increased humidity allowed for the establishment of Nothofagus forest. The late Holocene is characterized by oscillations in forest dominance largely driven by changes in humidity, possibly associated with the onset or strengthening of ENSO. In the last 4900 yr, humid periods (4900–3800 and 2850–1350 cal yr BP) have promoted Nothofagus forest, whereas drier times (3800–2850 and 1350–450 cal yr BP) have favored Austrocedrus expansion. At intermediate moisture levels, however, the lower forest supported both taxa, and fire became an important control of community composition, with severe, infrequent fires facilitating Nothofagus regeneration and high fire frequency and intensity supporting Austrocedrus.

Sign in / Sign up

Export Citation Format

Share Document