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 Holocene biogeography of Tsuga mertensiana and other conifers in the Kenai Mountains and Prince William Sound, south-central Alaska

The Holocene ◽  
2016 ◽  
Vol 27 (4) ◽  
pp. 485-495 ◽  
Author(s):  
R Scott Anderson ◽  
Darrell S Kaufman ◽  
Edward Berg ◽  
Caleb Schiff ◽  
Thomas Daigle
Keyword(s):  
Climatic Factors ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Early Holocene ◽  
Ice Age ◽  
Prince William Sound ◽  
Conifer Forest ◽  
The Holocene ◽  
South Central ◽  
Tsuga Mertensiana

Several important North American coastal conifers – having immigrated during the Holocene from the southeast – reach their northern and upper elevation limits in south-central Alaska. However, our understanding of the specific timing of migration has been incomplete. Here, we use two new pollen profiles from a coastal and a high-elevation site in the Eastern Kenai Peninsula–Prince William Sound region, along with other published pollen records, to investigate the Holocene biogeography and development history of the modern coastal Picea (spruce)– Tsuga (hemlock) forest. Tsuga mertensiana became established at Mica Lake (100 m elevation, near Prince William Sound) by 6000 cal. BP and at Goat Lake (550 m elevation in the Kenai Mountains) sometime after 3000 years ago. Tsuga heterophylla was the last major conifer to arrive in the region. Although driven partially by climate change, major vegetation changes during much of the Holocene are difficult to interpret exclusively in terms of climate, with periods of slow migration alternating with more rapid movement. T. mertensiana expanded slowly northeastward in the early Holocene, compared with Picea sitchensis or T. heterophylla. Difficulty of invading an already established conifer forest may account for this. We suggest that during the early Holocene, non-climatic factors as well as proximity to refugia, influenced rates of migration. Climate may have been more important after ~2600 cal. BP. Continued expansion of T. mertensiana at Goat Lake at the Medieval Climate Anomaly (MCA)–‘Little Ice Age’ (‘LIA’) transition suggests warm and wet winters. But expansion of T. mertensiana at both sites was arrested during the colder climate of the ‘LIA’. The decline was more extensive at Goat Lake, where climatic conditions may have been severe enough to reduce or eliminate the T. mertensiana population. T. mertensiana continued its expansion around Goat Lake after the ‘LIA’.

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.

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.

Lateglacial and early Flandrian environmental history of the Isle of Mull, Inner Hebrides, Scotland

1986 ◽  
Vol 77 (1) ◽  
pp. 1-20 ◽  
Author(s):  
J. J. Lowe ◽  
M. J. C. Walker
Keyword(s):  
Environmental History ◽  
Polar Front ◽  
Climatic Conditions ◽  
Plant Succession ◽  
Ice Cap ◽  
South Central ◽  
Tundra Vegetation ◽  
Loch Lomond ◽  
Thermal Maximum ◽  
History Of

ABSTRACTPollen-stratigraphic data, supported by lithological, geochemical and radiocarbon evidence are described from two Late Devensian Lateglacial sites on the Isle of Mull, Inner Hebrides, Scotland. The data suggest that, following the wastage of the Late Devensian ice sheet some time prior to 13,000 BP, an open grass- and sedge-dominated landscape was colonised first by juniper scrub and subsequently by Empetrum heaths. Tree birch development was limited principally, it would seem, by exposure to strong westerly winds, although some scattered birch woodland did become established in more sheltered localities. The thermal maximum of the Lateglacial Interstadial appears to have occurred from c. 13,000 to 12,000 BP after which climate began to deteriorate as the atmospheric Polar Front migrated southwards. The harsh climatic conditions of the Loch Lomond Stadial, the full effects of which were experienced after c. 10,700 BP, led to the break-up of the Interstadial vegetation cover, the development of an ice cap and several smaller cirque and valley glaciers in the hills of south-central Mull, and the establishment of a periglacial regime throughout the island. By c. 10,200 BP, however, climatic amelioration was underway once more, the Loch Lomond Advance glaciers had wasted completely, and a plant succession was initiated which led to the replacement of tundra vegetation communities by Empetrum heath, juniper scrub and eventually hazel-birch woodland within the space of c. 1500 years.

History of sedimentation in the northwestern Lake Superior basin and its relation to Lake Agassiz overflow

1988 ◽  
Vol 25 (10) ◽  
pp. 1660-1673 ◽  
Author(s):  
James T. Teller ◽  
Paul Mahnic
Keyword(s):  
Lake Superior ◽  
Proximal Part ◽  
Water Levels ◽  
Lake Agassiz ◽  
Nearshore Processes ◽  
Postglacial History ◽  
Thunder Bay ◽  
Clayey Silt ◽  
History Of ◽  
Glacial Advance

Following the Marquette glacial advance, which blocked the eastern outlets of Lake Agassiz and reached northern Michigan about 10 000 years BP, the ice margin wasted back toward the northeast, eventually allowing Lake Agassiz to overflow into the Lake Superior basin through a series of channels. Sediments deposited east of Thunder Bay near the mouth of the Wolf, Wolfpup, Shillabeer, and Black Sturgeon channels reflect three phases in the history of Lake Superior and provide the basis for reconstructing the early postglacial history of the region.The lower part of the sedimentary sequence in the northwestern Superior Basin consists of a distinctive red, stoney, sandy till deposited during the Marquette glacial advance and is overlain by pink rhythmites deposited in Lake Superior when it was a deep proglacial lake at the Minong level. The nearly 300 rhythmites deposited at this time typically consist of 4 cm thick silt + clay couplets, which are punctuated by silt laminae and sandy turbidites that probably represent major thaw periods or storms. These are seasonal rhythmites, deposited prior to the reopening of the Lake Agassiz outlets into the Superior Basin, and they display a decrease in dropstones, grain size, and thickness upsection that reflects a receding ice margin.The first eastern outlets of Lake Agassiz were uncovered around 9500 years BP, and water began overflowing into the Superior Basin in a series of catastrophic floods. Subaqueous fans developed at the Wolf, Wolfpup, and Shillabeer confluence and at the mouth of the Black Sturgeon channel. Large sandy turbidites, 45–65 cm thick, were deposited in the proximal part of these fans, with scouring and large (1 m) trough cross-beds resulting from the largest Lake Agassiz floods. These sediments are transitional to distal, clayey silt rhythmites, 10–22 cm thick. A gradual decrease in flooding from Lake Agassiz is reflected in the upward decrease in rhythmite thickness to 1–3 cm by about 8200 years BP. The final sequence of sediments shows a transition to sandy units as water levels dropped in the Superior Basin and the influence of nearshore processes increased.

scholarly journals The Post-glacial history of vegetation and climate at Ennadai Lake, Keewatin, and Lynn Lake, Manitoba (Canada)

1967 ◽  
Vol 18 (1) ◽  
pp. 176-197 ◽  
Author(s):  
Harvey Nichols
Keyword(s):  
The Arctic ◽  
Radiocarbon Dates ◽  
Tundra Vegetation ◽  
History Of Vegetation ◽  
Northwest Europe ◽  
History Of ◽  
Summer Temperatures ◽  
Cold Episode ◽  
Climatic History ◽  
Lynn Lake

Abstract. Peat from Keewatin and Manitoba contained macrofossil and palynological evidence of former latitudinal movements of the forest — tundra boundary probably in response to the changing location of the mean summer position of the Arctic front. There was very rapid melting of the large late-Wisconsin icesheet between 8000 and 6000 years B. P., and swift immigration of Picea, with no evidence of tundra vegetation after deglaciation. From 6000 to 3500 years B. P. the Boreal forest extended far north of its present limit, with a short-lived cooler phase about 5000 years ago. This generally warm period was followed by cooler and variable climatic episodes after 3500 B. P. and by a climatic deterioration about 2600 years ago. There was an amelioration between 1500 and 600 B. P., followed by a prolonged cold episode which terminated peat growth in the tundra. The approximate mean summer temperatures at Ennadai Lake have been estimated from the changing location of the northern limit of forest. The radiocarbon dates for these climatic events coincide with a number of changes recorded in the climatic history of northwest Europe.

Modern Pollen Rain and Vegetational History of the Malaspina Glacier District, Alaska

1986 ◽  
Vol 25 (1) ◽  
pp. 100-120 ◽  
Author(s):  
Dorothy M. Peteet
Keyword(s):  
Gulf Of Alaska ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Plant Succession ◽  
Coastal Forest ◽  
Modern Pollen ◽  
Pollen Rain ◽  
History Of ◽  
Climatic Cooling ◽  
Coastal Meadow

Seventy surface pollen samples from coastal forest, coastal meadow, muskeg, tree line, and alpine tundra communities form a basis for interpreting fossil pollen assemblages in the Malaspina Glacier district, Alaska. Poflen and macrofossil analyses of three radiocarbon-dated fossil sections from Icy Cape indicate that vegetational changes resulting from plant succession can be distinguished from those of migrational and climatic origin. Vegetation of the early Holocene xerothermic interval (10,000–7600 yr B.P.) was dominated by Alnus communities. Wetter conditions ensued, enabling generative muskeg surfaces to develop and first Picea sitchensis, then Tsuga heterophylla to expand from areas southeastward. Climatic cooling in more recent millennia (3500 yr B.P. to the present) is indicated by the appearance and persistent growth of Tsuga mertensiana and Selaginella selaginoides along this portion of the Gulf of Alaska coastline.

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