Megafloral change across the Cretaceous/Tertiary boundary in the northern Great Plains and Rocky Mountains, U.S.A.

1990 ◽  
pp. 433-444 ◽  
Author(s):  
Kirk R. Johnson ◽  
Leo J. Hickey
Keyword(s):  
Great Plains ◽  
Rocky Mountains ◽  
Northern Great Plains

scholarly journals Pygmy Shrew (Sorex hoyi) in Montana east of the Rocky Mountains with comments on its distribution across the northern Great Plains

2014 ◽  
Vol 128 (2) ◽  
pp. 204
Author(s):  
Paul Hendricks ◽  
Susan Lenard
Keyword(s):  
North Dakota ◽  
Great Plains ◽  
Rocky Mountains ◽  
Riparian Vegetation ◽  
Missouri River ◽  
Northern Great Plains ◽  
Prairie Pothole ◽  
The North ◽  
Pygmy Shrew ◽  
River Bottom

Range maps for Pygmy Shrew (Sorex hoyi) show a large hiatus over much of the northern Great Plains between the Rocky Mountains and eastern North Dakota. We report a new record of the Pygmy Shrew in northeastern Montana, review previous records for the state and adjacent regions bordering Montana to the north and east, and suggest that the range boundary in the northern Great Plains be redrawn farther south to include all of Montana north of the Missouri River. This is consistent with the known range of the Pygmy Shrew in eastern North Dakota and South Dakota, where the species has been documented only north and east of the Missouri River, although records are still lacking from north of the Missouri River in northwestern North Dakota and adjacent regions of Canada. Pygmy Shrews will probably be found at additional localities in prairie regions of Canada adjacent to Montana, most likely in association with prairie pothole wetlands, river bottom riparian vegetation, and hardwood draws.

Climatic and hydrologic variability during the past millennium in the eastern Rocky Mountains and northern Great Plains of western Canada

2008 ◽  
Vol 70 (2) ◽  
pp. 188-197 ◽  
Author(s):  
Thomas W.D. Edwards ◽  
S. Jean Birks ◽  
Brian H. Luckman ◽  
Glen M. MacDonald
Keyword(s):  
Great Plains ◽  
Rocky Mountains ◽  
Ice Age ◽  
Northern Great Plains ◽  
Western Canada ◽  
Medieval Climate Anomaly ◽  
Air Masses ◽  
The Past ◽  
Hydrologic Variability ◽  
Atmospheric Relative Humidity

AbstractModelling of tree-ring δ13C and δ18O data from the Columbia Icefield area in the eastern Rocky Mountains of western Canada provides fuller understanding of climatic and hydrologic variability over the past 1000 yr in this region, based on reconstruction of changes in growth season atmospheric relative humidity (RHgrs), winter temperature (Twin) and the precipitation δ18O–Twin relation. The Little Ice Age (~ AD 1530s–1890s) is marked by low RHgrs and Twin and a δ18O–Twin relation offset from that of the present, reflecting enhanced meridional circulation and persistent influence of Arctic air masses. Independent proxy hydrologic evidence suggests that snowmelt sustained relatively abundant streamflow at this time in rivers draining the eastern Rockies. In contrast, the early millennium was marked by higher RHgrs and Twin and a δ18O–Twin relation like that of the 20th century, consistent with pervasive influence of Pacific air masses because of strong zonal circulation. Especially mild conditions prevailed during the “Medieval Climate Anomaly” ~ AD 1100–1250, corresponding with evidence for reduced discharge in rivers draining the eastern Rockies and extensive hydrological drought in neighbouring western USA.

scholarly journals Drought and vegetation change in the central Rocky Mountains and western Great Plains: potential climatic mechanisms associated with megadrought conditions at 4200 cal yr BP

2018 ◽  
Vol 14 (8) ◽  
pp. 1195-1212 ◽  
Author(s):  
Vachel A. Carter ◽  
Jacqueline J. Shinker ◽  
Jonathon Preece
Keyword(s):  
Great Plains ◽  
Rocky Mountains ◽  
Vegetation Change ◽  
Specific Humidity ◽  
Northern Great Plains ◽  
Study Region ◽  
Normal Heights ◽  
Regional Drought ◽  
Central Rocky Mountains ◽  
Western Great Plains

Abstract. Droughts are a naturally re-occurring phenomena that result in economic and societal losses. Yet, the most historic droughts that occurred in the 1930s and 1950s in the Great Plains and western United States were both shorter in duration and less severe than megadroughts that have plagued the region in the past. Roughly 4200 years ago, a ∼150-year long megadrought occurred in the central Rocky Mountains, as indicated by sedimentary pollen evidence documenting a brief and unique change in vegetation composition from Long Lake, southeastern Wyoming. Neighbouring the central Rocky Mountains, several dune fields reactivated in the western Great Plains around this time period illustrating a severe regional drought. While sedimentary pollen provides evidence of past drought, paleoecological evidence does not provide context for the climate mechanisms that may have caused the drought. Thus, a modern climate analogue technique was applied to the sedimentary pollen and regional dune reactivation evidence identified from the region to provide a conceptual framework for exploring possible mechanisms responsible for the observed ecological changes. The modern climate analogues of 2002/2012 illustrate that warm and dry conditions persisted through the growing season and were associated with anomalously higher-than-normal geopotential heights centred over the Great Plains. In the spring, higher-than-normal heights suppressed moisture transport via the low-level jet from the Gulf of Mexico creating a more southwesterly component of flow. In the summer, higher-than-normal heights persisted over the northern Great Plains resulting in a wind shift with an easterly component of flow, drawing in dry continental air into the study region. In both cases, lower-than-normal moisture in the atmosphere (via 850 mbar specific humidity) inhibited uplift and potential precipitation. Thus, if the present scenario existed during the 4.2 ka drought, the associated climatic responses are consistent with local and regional proxy data suggesting regional drought conditions in the central Rocky Mountains and western Great Plains.

Postglacial Vegetation and Climate in the Northwestern Great Plains of Montana

1989 ◽  
Vol 31 (1) ◽  
pp. 57-73 ◽  
Author(s):  
Cathy W. Barnosky
Keyword(s):  
Great Plains ◽  
Rocky Mountains ◽  
Northern Great Plains ◽  
Northern Margin ◽  
Mountain Ranges ◽  
Volcanic Ashes ◽  
High Sedimentation ◽  
Poaceae Pollen ◽  
Vegetation And Climate ◽  
Percentage Data

AbstractTwo pollen records from the northern Great Plains of Montana portray vegetational and climatic changes during the last 12,200 yr in a region where few other data are available. A 6.4-m core from Guardipee Lake, east of the Rocky Mountains in the area formerly covered by the Two Medicine glacial lobe, contains the Glacier Peak G and Mt. St. Helens Jy volcanic ashes. Pollen percentage data are dominated byPinus, Poaceae,Artemisia, and Chenopodiaceae/Amaranthaceae. High nonarboreal percentages and small amounts ofJuniperus, Alnus, Salix, andPopuluspollen in sediments deposited between ca. 12,200 and ca. 9300 yr B.P. suggest a temperate grassland with shrubs growing locally in mesic settings. After ca. 9300 yr B.P. an increase in Chenopodiaceae/Amaranthaceae pollen and a concomitant decline inArtemisiaindicate the development of more xerophytic grassland and the beginning of the altithermal period. The lake probably was intermittently dry thoughout the Holocene. A high sedimentation rate and the presence of cereal taxa characterize the last ca. 100 yr of Euroamerican settlement. Lost Lake at the northern margin of the Highwood Mountains yielded a 16.94-m core with no volcanic ashes that spans the last 9400 yr. High amounts of Chenopodiaceae/Amaranthaceae,Artemisia, and Poaceae pollen, from ca. 9400 to ca. 6000 yr B.P., suggest the presence of xeric grassland and a climate drier than at present. After ca. 6000 yr B.P. Chenopodiaceae/Amaranthaceae values declined andArtemisia, Poaceae,Pinus, Picea, Salix, Alnus, andBetulaincreased. The inferred spread of shrubs in wet habitats at this time and the expansion of forest in nearby mountain ranges indicate the end of the altithermal period and the onset of cooler/moister conditions.

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