The arctic tree line as a record of past and recent climatic changes

1994 ◽  
Vol 2 (1) ◽  
pp. 78-90 ◽  
Author(s):  
Serge Payette ◽  
Claude Lavoie
Keyword(s):  
North America ◽  
Structural Changes ◽  
The Arctic ◽  
Spatiotemporal Pattern ◽  
Northern Eurasia ◽  
Tree Line ◽  
Vegetative Regeneration ◽  
Nonequilibrium Conditions ◽  
Arctic Climate Change ◽  
Line Positions

Past and recent changes in the position of the arctic tree line and spatial structure of nearby forests are reviewed. The advancing tree line in the arctic tundra in the first half of the Holocene was promoted by sexual regeneration because of warmer climate. The northernmost tree-line positions were reached in early Holocene in western North America and northern Eurasia, and during or after mid-Holocene in central and eastern North America. The position of the arctic tree line remained rather stable across the northern hemisphere from 3500 years BP to the present. General cooling during the late Holocene did not induce significant retreat of the tree line at sites not affected by catastrophic disturbances (fire) because trees and forests were able to survive through vegetative regeneration. Minor displacements deduced from dendroecological data were recorded during the last 500 years, whereas more important structural changes occurred in the nearby northernmost forests and tree groves through the shifting dominance of growth forms in preestablished tree and forest populations. The spatiotemporal pattern of tree-line and forest changes along the arctic border suggests that both equilibrium and nonequilibrium conditions prevailed during the Holocene.Key words: tree line, Arctic, climate change, paleoecology, Holocene.

scholarly journals Evolving perspectives on caribou population dynamics, have we got it right yet?

Rangifer ◽  
1996 ◽  
Vol 16 (4) ◽  
pp. 95 ◽  
Author(s):  
A.T. Bergerud
Keyword(s):  
North America ◽  
Predation Risk ◽  
Open Water ◽  
Tree Cover ◽  
The Arctic ◽  
Tree Line ◽  
Population Limitation ◽  
Wolf Predation ◽  
Annual Range ◽  
George River

The roles of food, weather and predation are compared between sedentary and migratory caribou herds. Sedentary herds disperse (space out) at calving time while the cows of migratory herds move in masse (space away) to calving grounds to reduce predation risk. The sedentary ecotype calves on ranges near open water if tree cover is present or in rugged topography in the absence of tree cover. The migratory ecotype aggregates on calving grounds located on alpine mountain plateaus or on the tundra north of the Arctic tree line. The two herds with the greatest densities in North America, the sedentary Slate Islands Herd and the migratory George River Herd both had changes in abundance that followed summer food problems. The hypothesis that winter lichen supplies determine abundance and set the carrying capacity is rejected. Lichens are not a necessary food for caribou. A review of the mortality of young calves documented in the past 30 years provides no support for the hypothesis that hypothermia is a common mortality problem. Young calves documented can be born inviable at birth if their dams are severely malnourished. The migratory caribou in North America reached peak numbers in the 1980s after wolf populations were heavily harvested in the 1970s. The sedentary ecotype is frequently regulated by wolf predation that affects both recruitment (R) and the mortality of adults (M). The balance between R/M schedules commonly occurs when R (calves) represents, about 15% of the herd and when numbers (prorated to the area of the dispersed annual range) approximate 0.06 caribou/km2. Population limitation of migratory herds by predation has occurred in the NWT and in several herds in Alaska but only when wolf densities were > 6.5/1000 km2. Wolf predation halted the growth of the George River Herd in 1980 but then wolves contracted rabies and the herd again increased and degraded spring/summer ranges. The reduced summer phytomass resulted in lower birth rates and increased the vulnerability of calves and possibly adults to wolf predation. Stabilizing mechanisms for migratory herds include movements between herds above tree line and range contractions/expansions with resultant changes in demography. It is hypothesized that the most important ecological variable in all seasonal distributions of caribou is predation risk rather than to maximize forage supplies.

New Evidence of the Late Neopleistocene Peopling of the Lower Ob Valley

2021 ◽  
Vol 49 (1) ◽  
pp. 9-20
Author(s):  
I. D. Zolnikov ◽  
A. A. Anoikin ◽  
E. A. Filatov ◽  
A. V. Vybornov ◽  
A. V. Vasiliev ◽  
...  
Keyword(s):  
Upper Paleolithic ◽  
The Arctic ◽  
Northern Eurasia ◽  
West Siberian Plain ◽  
Faunal Remains ◽  
Human Occupation ◽  
Large Area ◽  
Paleolithic Site ◽  
The North ◽  
Available Information

This study focuses on the early human occupation of the arctic part of the West Siberian Plain and introduces the finds at the Paleolithic site Kushevat (Shuryshkarsky District, Yamal-Nenets Autonomous Okrug), discovered in 2020. Geological and geomorphological characteristics of the Lower Ob region are provided, the chronology of the key Middle and Late Neopleistocene sequences is assessed, and criteria underlying the search for Paleolithic sites in the area are outlined. We describe the discovery and excavations at Kushevat, its stratigraphy and its faunal remains. On the basis of correlation with neighboring key Late Neopleistocene sections with a representative series of absolute dates, the age of the site is estimated at cal 50–35 ka BP. Results of a traceological study of a possibly human-modified reindeer antler are provided. Findings at Kushevat and the available information on the early peopling of northern Eurasia suggest that the boundary of the inhabited part of that region must be shifted ~200 km to the north. The Ob, therefore, is one of the last major Siberian rivers where traces of the Early Upper Paleolithic culture have been found. The discovery of a stratified site in its lower stretch is a milestone in the Paleolithic studies in the region. A large area over which faunal remains are distributed, and the presence of lithics among the surface finds, suggest that Kushevat is a highly prospective site for future archaeological studies of the early stages in the human peopling of the region.

Arctic Science and Technology Information System

2021 ◽  
Vol 23 (2) ◽  
pp. 5-7
Author(s):  
Jane C. Duffy
Keyword(s):  
Information System ◽  
North America ◽  
Science And Technology ◽  
The Arctic ◽  
Free Text ◽  
Bibliographic Database ◽  
Research Projects ◽  
Search Terms ◽  
University Of Calgary ◽  
The University

ASTIS offers over 83,000 records that provide freely available access to publications, including research and research projects, about Canada's north. This database is a product of the Arctic Institute of North America at the University of Calgary, Alberta, Canada which also maintains subsidiary regional, subject, and initiative-based databases. The subsidiary databases are all housed within and accessible through the main ASTIS database. Examples of the smaller databases include: ArcticNet Publications Database, the Nunavik Bibliography, and the Northern Granular Resources Bibliographic Database. ASTIS offers the ability to browse through its access points, including its own thesauri, thus permitting users to select and use a variety of free-text and controlled search terms.

Toward a biogeographic regionalization of the Nearctic region: Area nomenclature and digital map

Zootaxa ◽  
2021 ◽  
Vol 5027 (3) ◽  
pp. 351-375
Author(s):  
TANIA ESCALANTE ◽  
GERARDO RODRÍGUEZ-TAPIA ◽  
JUAN J. MORRONE
Keyword(s):  
North America ◽  
Transition Zone ◽  
Rocky Mountain ◽  
Volcanic Belt ◽  
Neotropical Region ◽  
The Arctic ◽  
Digital Map ◽  
Biogeographic Regionalization ◽  
Sierra Madre ◽  
Nearctic Region

We provide a preliminary nomenclatural proposal and a digital map of the Nearctic region, based on published regionalizations, especially Dice (1943), and applying the International Code of Area Nomenclature. The Nearctic region is comprised of three subregions (one of them with two dominions), one transition zone and 29 provinces. The Arctic subregion, in northern North America and Greenland, includes the Eskimoan, Hudsonian, Aleutian and Sitkan provinces. The Western subregion, in western North America, includes the Californian dominion, with the Californian and Oregonian provinces; and the Rocky Mountain dominion, including the Montanian, Saskatchewan, Palusian, Artemisian, Coloradan, Kansan, Mohavian, Navahonian, Sonoran, Chihuahuan, Comanche, and Baja California provinces. The Alleghany subregion, in eastern North America, includes the Illinoian, Canadian, Carolinian, Texan, Austroriparian, and Tamaulipan provinces. The Mexican Transition Zone, situated in the area of overlap with the Neotropical region, includes the Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur and Chiapas Highlands provinces.  

Chromosome races in Rumex arcticus (Polygonaceae)

1972 ◽  
Vol 50 (2) ◽  
pp. 378-380
Author(s):  
Gerald A. Mulligan ◽  
Clarence Frankton
Keyword(s):  
North America ◽  
North American ◽  
Bering Sea ◽  
Kamchatka Peninsula ◽  
The Arctic ◽  
Chromosome Races ◽  
High Polyploid ◽  
Seward Peninsula ◽  
Northwestern North America ◽  
The Bering Sea

Rumex arcticus Trautv., a species found on the mainland of northwestern North America and in northeastern U.S.S.R., contains tetraploid (2n = 40), dodecaploid (2n = 120), and perhaps 2n = 160 and 2n = 200 chromosome races. Most North American plants are tetraploid and are larger in size and have more compound and contiguous inflorescences than typical R. arcticus. Typical plants of R. arcticus occur in the arctic U.S.S.R., St. Lawrence Island in the Bering Sea, and at the tip of the Seward Peninsula of Alaska, and they all have 120 or more somatic chromosomes. High polyploid plants of R. arcticus that resemble North American tetraploids in appearance apparently occur on the Kamchatka Peninsula. These have been called R. kamtshadalus Komarov or R. arcticus var. kamtshadalus (Kom.) Rech. f. by some authors.

scholarly journals The Interannual Variability of the Haines Index over North America

2013 ◽  
Vol 52 (11) ◽  
pp. 2396-2409 ◽  
Author(s):  
Lejiang Yu ◽  
Shiyuan Zhong ◽  
Xindi Bian ◽  
Warren E. Heilman ◽  
Joseph J. Charney
Keyword(s):  
United States ◽  
Pacific Ocean ◽  
North America ◽  
Interannual Variability ◽  
Large Scale ◽  
Southern Oscillation ◽  
Southeastern United States ◽  
Lower Atmosphere ◽  
The Arctic ◽  
Fire Weather Index

AbstractThe Haines index (HI) is a fire-weather index that is widely used as an indicator of the potential for dry, low-static-stability air in the lower atmosphere to contribute to erratic fire behavior or large fire growth. This study examines the interannual variability of HI over North America and its relationship to indicators of large-scale circulation anomalies. The results show that the first three HI empirical orthogonal function modes are related respectively to El Niño–Southern Oscillation (ENSO), the Arctic Oscillation (AO), and the interdecadal sea surface temperature variation over the tropical Pacific Ocean. During the negative ENSO phase, an anomalous ridge (trough) is evident over the western (eastern) United States, with warm/dry weather and more days with high HI values in the western and southeastern United States. During the negative phase of the AO, an anomalous trough is found over the western United States, with wet/cool weather and fewer days with high HI, while an anomalous ridge occurs over the southern United States–northern Mexico, with an increase in the number of days with high HI. After the early 1990s, the subtropical high over the eastern Pacific Ocean and the Bermuda high were strengthened by a wave train that was excited over the tropical western Pacific Ocean and resulted in warm/dry conditions over the southwestern United States and western Mexico and wet weather in the southeastern United States. The above conditions are reversed during the positive phase of ENSO and AO and before the early 1990s.

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