Late-Glacial Vegetation and Climate Change in Western Oregon

1998 ◽  
Vol 49 (3) ◽  
pp. 287-298 ◽  
Author(s):  
Laurie D. Grigg ◽  
Cathy Whitlock
Keyword(s):  
Pacific Northwest ◽  
Younger Dryas ◽  
Late Glacial ◽  
Warming Trend ◽  
Cascade Range ◽  
Subalpine Forest ◽  
Coast Range ◽  
The Pacific ◽  
Dry Conditions ◽  
Vegetation And Climate

Pollen records from two sites in western Oregon provide information on late-glacial variations in vegetation and climate and on the extent and character of Younger Dryas cooling in the Pacific Northwest. A subalpine forest was present at Little Lake, central Coast Range, between 15,700 and 14,850 cal yr B.P. A warm period between 14,850 and 14,500 cal yr B.P. is suggested by an increase in Pseudotsuga pollen and charcoal. The recurrence of subalpine forest at 14,500 cal yr B.P. implies a return to cool conditions. Another warming trend is evidenced by the reestablishment of Pseudotsuga forest at 14,250 cal yr B.P. Increased haploxylon Pinus pollen between 12,400 and 11,000 cal yr B.P. indicates cooler winters than before. After 11,000 cal yr B.P. warm dry conditions are implied by the expansion of Pseudotsuga. A subalpine parkland occupied Gordon Lake, western Cascade Range, until 14,500 cal yr B.P., when it was replaced during a warming trend by a montane forest. A rise in Pinuspollen from 12,800 to 11,000 cal yr B.P. suggests increased summer aridity. Pseudotsuga dominated the vegetation after 11,000 cal yr B.P. Other records from the Pacific Northwest show an expansion of Pinus from ca. 13,000 to 11,000 cal yr B.P. This expansion may be a response either to submillennial climate changes of Younger Dryas age or to millennial-scale climatic variations.

Postglacial Vegetation and Climate of the Cascade Range, Central Oregon

1995 ◽  
Vol 43 (3) ◽  
pp. 370-381 ◽  
Author(s):  
Debra S. Sea ◽  
Cathy Whitlock
Keyword(s):  
Pacific Northwest ◽  
Large Scale ◽  
Climatic Conditions ◽  
Cascade Range ◽  
Pollen Record ◽  
Climate History ◽  
Vegetational Change ◽  
The Pacific ◽  
Closed Forest ◽  
Vegetation And Climate

AbstractPollen data from two sites provide information on the postglacial vegetation and climate history of the Cascade Range. Indian Prairie in the western Cascade Range was colonized by subalpine forests of Pinus, Picea, and Tsuga and open meadows prior to ca. 12,400 14C yr B.P. The treeline lay 500 to 1000 m below its modern elevation and conditions were cooler than at present. From ca. 12,400 to ca. 9950 14C yr B.P. Abies became important and the forest resembled that presently found at middle elevations in the western Cascade Range. The pollen record implies a rise in treeline and warmer conditions than before. From ca. 10,000 to 4000-4500 14C yr B.P., conditions that were warmer and effectively drier than today led to the establishment of a closed forest composed of Pseudotsuga, Abies, and, at lower elevations, Quercus and Corylus. During this period, Gold Lake Bog in the High Cascades was surrounded by closed forest of Pinus and Abies. The early-Holocene pollen assemblages at both Indian Prairie and Gold Lake Bog lack modern analogues, and it is likely that greater-than-present summer radiation fostered unique climatic conditions and vegetation associations at middle and high elevations. In the late Holocene, beginning ca. 4000-4500 14C yr B.P., cooler and more humid conditions prevailed and the modern vegetation was established. A comparison of these sites with others in the Pacific Northwest suggests that major patterns of vegetational change at individual sites were a response to large-scale changes in the climate system that affected the entire region.

Geochemical and Petrological Characterization of Ash Samples from Cascade Range Volcanoes

1971 ◽  
Vol 1 (2) ◽  
pp. 261-282 ◽  
Author(s):  
Keith Randle ◽  
Gordon G. Goles ◽  
Laurence R. Kittleman
Keyword(s):  
Pacific Northwest ◽  
Volcanic Ash ◽  
Cascade Range ◽  
Crystalline Material ◽  
Refractive Indices ◽  
Crystalline Materials ◽  
The Pacific ◽  
Volcanic Ashes ◽  
Different Sources

Twenty-nine samples of volcanic ash from the Pacific Northwest were analyzed by instrumental neutron activation techniques, with the aim of distinguishing among ashes from different sources. Preliminary results of petrographic studies of 42 ash or pumice samples are also reported. Geochemical characteristics of Mazama ash are defined, and problems induced by winnowing of crystalline material during transport and by weathering are discussed. Contents of La, Th, and Co, and La/Yb ratios are shown to be good discriminants. Data on refractive indices and on proportions of crystalline materials also aid in distinguishing among the various volcanic ashes studied. Ash and pumice found in archaeological contexts at Fort Rock Cave, Paisley Cave, Wildcat Canyon, and Hobo Cave are all from Mount Mazama, presumably from the culminating cruption of 7000 years ago.

Paleoecology in the Pacific Northwest I. Late Quaternary vegetation and climate

1981 ◽  
Vol 21 (2) ◽  
pp. 730-737
Author(s):  
Matsuo Tsukada ◽  
Shinya Sugita ◽  
Dennis M. Hibbert
Keyword(s):  
Pacific Northwest ◽  
Late Quaternary ◽  
The Pacific ◽  
Vegetation And Climate

Predicting deposition of debris flows in mountain channels

1990 ◽  
Vol 27 (4) ◽  
pp. 409-417 ◽  
Author(s):  
Lee E. Benda ◽  
Terrance W. Cundy
Keyword(s):  
Pacific Northwest ◽  
Debris Flows ◽  
Field Measurements ◽  
Coast Range ◽  
Oregon Coast Range ◽  
Oregon Coast ◽  
Aerial Photos ◽  
The Pacific ◽  
Channel Slope ◽  
Junction Angle

An empirical model for predicting deposition of coarse-textured debris flows in confined mountain channels is developed based on field measurements of 14 debris flows in the Pacific Northwest, U.S.A. The model uses two criteria for deposition: channel slope (less than 3.5°) and tributary junction angle (greater than 70°). The model is tested by predicting travel distances of 15 debris flows in the Oregon Coast Range and six debris flows in the Washington Cascades, U.S.A. The model is further tested on 44 debris flows in two lithological types in the Oregon Coast Range using aerial photos and topographic maps; on these flows only the approximate travel distance is known. The model can be used by resource professionals to identify the potential for impacts from debris flows. Key words: debris flow, deposition, travel, erosion.

Mountain Climates of North America

2000 ◽  
Author(s):  
C. David Whiteman
Keyword(s):  
United States ◽  
North America ◽  
Sierra Nevada ◽  
Rocky Mountains ◽  
Climatic Conditions ◽  
Cascade Range ◽  
Coast Range ◽  
Alaska Range ◽  
Mountain Ranges ◽  
The Pacific

The basic climatic characteristics of the major mountain ranges in the United States—the Appalachians, the Coast Range, the Alaska Range, the Cascade Range, the Sierra Nevada, and the Rocky Mountains—can be described in terms of the four factors discussed in chapter 1. The mountains of North America extend latitudinally all the way from the Arctic Circle (66.5°N) to the tropic of Cancer (23.5°N) (figure 2.1). There are significant differences in day length and angle of solar radiation over this latitude belt that result in large seasonal and diurnal differences in the weather from north to south. Elevations in the contiguous United States extend from below sea level at Death Valley to over 14,000 ft (4270 m) in the Cascade Range, the Sierra Nevada, and the Rocky Mountains. Several prominent peaks along the Coast Range in Alaska and Canada (e.g., Mount St. Elias and Mount Logan) reach elevations above 18,000 ft (5486 m). Denali (20,320 ft or 6194 m) in the Alaska Range is the highest peak in North America. The highest peak in the Canadian Rockies is Mt. Robson, with an elevation of 12,972 ft (3954 m). The climates of the Coast Range, the Cascade Range, and the Sierra Nevada, all near the Pacific Ocean, are primarily maritime. The Appalachian Mountains of the eastern United States are subject to a maritime influence from the Atlantic Ocean and the Gulf of Mexico, but they are also affected by the prevailing westerly winds that bring continental climatic conditions. Only the climate of the Rocky Mountains, far from both the Pacific and Atlantic Oceans, is primarily continental. Each of the mountain ranges is influenced by regional circulations. For example, the Appalachians are exposed to the warm, moist winds brought northward by the Bermuda-Azores High and to the influence of the Gulf Stream. Similarly, the Coast Range feels the impact of the Pacific High, the Aleutian low, and the Japanese Current. A mountain range, depending on its size, shape, orientation, and location relative to air mass source regions, can itself affect the regional climate by acting as a barrier to regional flows.

Last glacial–interglacial environments in the southern Rocky Mountains, USA and implications for Younger Dryas-age human occupation

2012 ◽  
Vol 77 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Christy E. Briles ◽  
Cathy Whitlock ◽  
David J. Meltzer
Keyword(s):  
Rocky Mountains ◽  
Fire History ◽  
Younger Dryas ◽  
Late Glacial ◽  
Subalpine Forest ◽  
Glacial Period ◽  
Last Glacial ◽  
Southern Rocky Mountains ◽  
Late Glacial Period ◽  
Fire Activity

The last glacial-interglacial transition (LGIT; 19–9 ka) was characterized by rapid climate changes and significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in the continental US today, mountain environments during the late-glacial period are poorly known. Yet, archaeological evidence from the Mountaineer site (2625 m elev.) indicates that Folsom-age Paleoindians were over-wintering in the Gunnison Basin during the Younger Dryas Chronozone (YDC; 12.9–11.7 ka). To determine the vegetation and fire history during the LGIT, and possible explanations for occupation during a period thought to be harsher than today, a 17-ka-old sediment core from Lily Pond (3208 m elev.) was analyzed for pollen and charcoal and compared with other high-resolution records from the southern Rocky Mountains. Widespread tundra and Picea parkland and low fire activity in the cold wet late-glacial period transitioned to open subalpine forest and increased fire activity in the Bølling–Allerød period as conditions became warmer and drier. During the YDC, greater winter snowpack than today and prolonged wet springs likely expanded subalpine forest to lower elevations than today, providing construction material and fuel for the early inhabitants. In the early to middle Holocene, arid conditions resulted in xerophytic vegetation and frequent fire.

Area burned in alpine treeline ecotones reflects region-wide trends

2016 ◽  
Vol 25 (12) ◽  
pp. 1209 ◽  
Author(s):  
C. Alina Cansler ◽  
Donald McKenzie ◽  
Charles B. Halpern
Keyword(s):  
Pacific Northwest ◽  
Subalpine Forest ◽  
Burned Area ◽  
Alpine Vegetation ◽  
Treeline Ecotone ◽  
Northern Rocky Mountains ◽  
Alpine Treeline ◽  
Area Burned ◽  
Alpine Treeline Ecotone ◽  
The Pacific

The direct effects of climate change on alpine treeline ecotones – the transition zones between subalpine forest and non-forested alpine vegetation – have been studied extensively, but climate-induced changes in disturbance regimes have received less attention. To determine if recent increases in area burned extend to these higher-elevation landscapes, we analysed wildfires from 1984–2012 in eight mountainous ecoregions of the Pacific Northwest and Northern Rocky Mountains. We considered two components of the alpine treeline ecotone: subalpine parkland, which extends upward from subalpine forest and includes a fine-scale mosaic of forest and non-forested vegetation; and non-forested alpine vegetation. We expected these vegetation types to burn proportionally less than the entire ecoregion, reflecting higher fuel moisture and longer historical fire rotations. In four of eight ecoregions, the proportion of area burned in subalpine parkland (3%–8%) was greater than the proportion of area burned in the entire ecoregion (2%–7%). In contrast, in all but one ecoregion, a small proportion (≤4%) of the alpine vegetation burned. Area burned regionally was a significant predictor of area burned in subalpine parkland and alpine, suggesting that similar climatic drivers operate at higher and lower elevations or that fire spreads from neighbouring vegetation into the alpine treeline ecotone.

Climatic Change at the End of the Last Glaciation in Japan Inferred from Pollen in Three Cores from the Northwest Pacific Ocean

1990 ◽  
Vol 34 (1) ◽  
pp. 101-110 ◽  
Author(s):  
Linda E. Heusser ◽  
Joseph J. Morley
Keyword(s):  
Pacific Ocean ◽  
Northeast Asia ◽  
Younger Dryas ◽  
Late Glacial ◽  
Northwest Pacific ◽  
Northwest Pacific Ocean ◽  
The Pacific ◽  
Pacific Coast Of Japan ◽  
The Northwest Pacific Ocean ◽  
Pollen Records

AbstractLate-glacial pollen time-series from high-sedimentation-rate marine cores KH79-3-C6, CH84-04, and CH84-14 show the rise of successional vegetation (typified by Betula) during the replacement of boreal forest types (Picea and Pinus) by thermophilous Quercus forests. Variations in these three marine pollen records replicate the trends and timing of pollen records from Japan and the structure and timing of vegetation and climatic changes on the Pacific coast of Japan since the last glacial maximum. In marine cores KH79-3-C6, CH84-04, and CH84-14, oxygen isotope and/or marine faunal data have been interpreted as evidence of a cooling event in the northwest Pacific Ocean which is coeval with the Younger Dryas chronozone. Pollen records from these northwest Pacific cores, like those from Japan, do not exhibit a regionally replicated, statistically robust, pollen assemblage which can be unambiguously interpreted as evidence of a late-glacial climatic reversal between ca. 11,000 and 10,000 yr B.P. The apparent disparity between the terrestrial (pollen) and marine evidence for a climatic oscillation during the Younger Dryas chron in northeast Asia further complicates the variable record of this brief late-glacial event.

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