bluuebunny/crossref_metadata_2025_split huggingface dataset:
Insolation Regime of Interglacials
Authors: Kukla George J. , Kukla Helena J. 
Published: December 2004

Seasonal changes in the extent of snow cover and pack-ice were analysed in the satellite-derived maps of the Northern Hemisphere obtained during the last 5 yr. Two intervals were studied in detail: summer 1968 to summer 1969 and summer 1971 to summer 1972. These studies demonstrate that the variation in ground albedo as a result of changing snow and ice cover affects the Earth's energy budget to a far greater degree than any possible extraterrestrial mechanism could do on such a short time scale. However, the rapid expansion of snow cover between late September and November suggests possible feed-back process which could be speeded up or slowed down by minute changes in energy and moisture budget at the snow accretion area. These changes may be of any origin, natural or artificial, and on the time scales ranging from days to millenia.In this context, the close correspondence between the radiometrically dated gross climate changes within the past 150,000 yr and between the curve showing the rate of change in winter insolation for the middle latitudes of the Northern Hemisphere is conspicuous. The periodicity of about 20,000 yr is involved.An insolation chronology is introduced here, which is based entirely on astronomic factors (on the so called Milankovitch mechanism of Earth orbital elements). It is independent of any geologic or geochronologic dating systems. Two alternating units comprise the insolation chronology.The positive insolation regime (PIR)is an episode defined by progressively increasing winter irradiation in the Northern Hemisphere, whereas thenegative insolation regime (NIR)is an episode of progressively decreasing winter irradiation. ThePIRclosely correlates with the generally warm intervals such as interglacials and temperate interstadials, theNIRwith generally cold intervals. This basic pattern interferes with short-term oscillations which may retard or advance the climate response on the scale of centuries.It is observed that the positive insolation regime designated asPIR110, which started at 11,000 YBP, has ended recently. The new negative insolation regime,NIR 0/ + 8, will last for the next 8000 yr. Inasmuch within the last radiometrically dated 150,000 yr noNIRis known to correlate with generally warm interval, the prognosis is for a long-lasting global cooling more severe than any experienced hitherto by civilized mankind.
Fire in the Virgin Forests of the Boundary Waters Canoe Area, Minnesota
Authors: Heinselman Miron L. 
Published: December 2004

AbstractFire largely determined the composition and structure of the presettlement vegetation of the Boundary Waters Canoe Area as well as the vegetation mosaic on the landscape and the habitat patterns for wildlife. It also influenced nutrient cycles, and energy pathways, and helped maintain the diversity, productivity, and long-term stability of the ecosystem. Thus the whole ecosystem was fire-dependent.At least some overstory elements in virtually all forest stands still date from regeneration that followed one or more fires since 1595 A.D. The average interval between significant fire years was about 4 yr in presettlement times, but shortened to 2 yr from 1868 to 1910 during settlement. However, 83% of the area burned before the beginning of suppression programs resulted from just nine fire periods: 1894, 1875, 1863–1964, 1824, 1801, 1755–1959, 1727, 1692, 1681. The average interval between these major fire years was 26 yr. Most present virgin forests date from regeneration that followed fires in these years. Significant areas were also regenerated by fires in 1903, 1910, 1936, and 1971. Most major fire years occurred during prolonged summer droughts of subcontinental extent, such as those of 1864, 1910, and 1936. Many fires were man-caused, but lightning ignitions were also common. Lightning alone is probably a sufficient source of ignitions to guarantee that older stands burned before attaining climax. Dry matter accumulations, spruce budworm outbreaks, blowdowns, and other interactions related to time since fire increase the probability that old stands will burn. Vegetation patterns on the landscape were influenced by such natural firebreaks as lakes, streams, wetlands, and moist slopes. Red and white pine are most common on islands, and to the east, northeast, or southeast of such firebreaks. Jack pine, aspen-birch, and sprout hardwood forests are most common on large uplands distant from or west of such firebreaks.A Natural Fire Rotation of about 100 yr prevailed in presettlement times, but many red and white pine stands remained largely intact for 150–350 yr, and some jack pine and aspen-birch forests probably burned at intervals of 50 yr or less. There is paleoecological evidence that fire was an ecosystem factor before European man arrived, and even before early man migrated to North America. Probably few areas ever attained the postulated fir-spruce-cedar-birch climax in postglacial times. To understand the dynamics of fire-dependent ecosystems fire must be studied as an integral part of the system. The search for stable communities that might develop without fire is futile and avoids the real challenge of understanding nature on her own terms.To restore the natural ecosystem of the Canoe Area fire should soon be reintroduced through a program of prescribed fires and monitored lightning fires. Failing this, major unnatural, perhaps unpredictable, changes in the ecosystem will occur.
A History of Fire and Vegetation in Northeastern Minnesota as Recorded in Lake Sediments
Authors: Swain Albert M. 
Published: December 2004

AbstractThe record of charcoal in lake sediments indicates that fire has always been an important ecological factor in the forest history of northeastern Minnesota. The annually laminated sediments of Lake of the Clouds permit precise dating of the charcoal peaks and record the changes in the influx of various pollen types. A detailed record of the past 1000 yr shows that the average frequency of fire is approximately 60–70 yr, with a range of about 20–100 yr. The amount of charcoal in sediments dating between 1000-500 y.a. is consistently higher than that for the last 500 yr, although the fire frequency for the two periods was not appreciably different. Pollen analysis shows no change or only short-term changes in the percentages of major pollen types following charcoal peaks.
The Importance of Fire as a Natural Ecological Factor in Itasca State Park, Minnesota
Authors: Frissell Sidney S. 
Published: December 2004

During the period between 1650 least 32 fires occurred in Itasca and 1922 at State Park. Twenty-one of these fires were of major consequence. A fire occurred on the average of every 8.8 yr with “major” fires every 10.3 yr. Any specific location in the park was affected by fire about every 22 yr.Individual burns varied in size from 580 acres to approximately 31,960 acres (99% of the park). Sixteen of the 21 “major” fires resulted in the regeneration of pine forests.
Fire-Dependent Forests in the Northern Rocky Mountains
Authors: Habeck James R. , Mutch Robert W. 
Published: December 2004

AbstractOne objective of wilderness and parkland fire-ecology research is to describe the relationships between fire and unmanaged ecosystems, so that strategies can be determined that will provide a more nearly natural incidence of fire. More than 50 yr of efforts directed toward exclusion of wildland fires in the Northern Rocky Mountains (western Montana and northern Idaho) have resulted in a definite and observable impact on the forest ecosystems in this region. Fire-ecology investigations in Glacier National Park and the Selway-Bitterroot Wilderness have helped to reveal the nature of this impact and to provide a better understanding of the natural role of fire within these coniferous ecosystems. Such areas provide a unique opportunity to study and test approaches designed to perpetuate unmodified ecosystems. However, we still don't understand all of the long-term consequences of fire control in those forest communities that have evolved fire-dependent characteristics.
The Ecological Role of Fire in the Jackson Hole area, Northwestern Wyoming
Authors: Loope Lloyd L. , Gruell George E. 
Published: December 2004

AbstractFire-history investigations in the Jackson Hole area of northwestern Wyoming reveal that most current stands of aspen and lodgepole pine regenerated following extensive fires between 1840 and 1890 and that widespread fires occurred in the 1600s and 1700s. White man's major effect on the fire incidence has been the successful suppression during the past 30–80 yr. Successional changes in the absence of fire include the deterioration of aspen stands, massive invasions of subalpine fir in lodgepole pine stands, great increase in conifer cover, heavy fuel buildups in lodgepole pine and Douglas fir stands, and increase in sagebrush and other shrubs. Steps are being taken, starting in 1972, to allow fire to play a more natural role in Grand Teton and Yellowstone National Parks. Teton National Forest plans experimental prescribed burning to determine whether fire can stimulate successful aspen regeneration in the presence of large numbers of wintering elk.
Spectral Analysis of Late Pleistocene-Holocene Sediments
Authors: Pisias Nicklas G. , Dauphin J.Paul , Sancetta Constance 
Published: December 2004

AbstractSpectral analysis of deep-sea sediments indicates that the fluctuations in compositional parameters are not random fluctuations with time. Spectra show significant peaks representing periodicities in the data of 380, 1300, and 2600 years. Two of these periods are similar to periods reported in 14C fluctuations. Analysis of a paleotemperature curve from the North Atlantic shows that the characteristics of the fluctuations within interglacial and glacial stages of the climate are similar, and that the spectrum has a significant peak at 2600 years.
Time-Transgressive Deglacial Retreat of Polar Waters from the North Atlantic
Authors: Ruddiman W.F. , McIntyre A. 
Published: December 2004

AbstractA 9300 yr-old zone of disseminated volcanic ash in North Atlantic sediments between 45° N and 65° N provides a time-synchronous reference layer against which we have compared the stratigraphic level of deglacial warming of ocean surface waters. In the Atlantic north of 45° N the most prominent feature of this warming is the replacement of low-carbonate glacial marine sediment containing only a single species of polar Foraminifera by calcareous oozes containing a diverse temperate fauna and flora. The local terminations of glacial conditions marked by this change are not synchronous at these latitudes, but range from 13,500 yr B.P. or older in the southeast near Great Britain to 6,500 yr B.P. or younger in the northwest near Greenland. Regionally, these local warmings trace the progressive westward and northward retreat of polar water from the North Atlantic. Since the withdrawal of polar water from the North Atlantic coincides with the northward shrinkage of temperate-latitude continental ice sheets, it is the best oceanic analog to continental deglaciation.Faunal, floral, lithologic, and isotopic parameters showing evidence for a sudden deglacial warming may not be time-synchronous; those parameters are subject to a range of environmental controls and may thus respond differently to the causal mechanism for global warming.
Bottom Water and Benthonic Foraminifera in the North Atlantic—Glacial-Interglacial Contrasts
Authors: Streeter S.Stephen 
Published: December 2004

AbstractToday, below 2500 m, benthonic foraminiferal faunas in the North Atlantic are dominated by a few species. Faunal composition changes slowly with increasing depth and decreasing temperature. Surface sediment and down-core counts of benthonic foraminifera reported by Phleger, Parker, and Peirson (1953) in the reports of the Swedish Deep-Sea Expedition have been supplemented by additional bottom sediment and piston core samples. Present-day benthonic foraminiferal assemblages from the deeper portions of the North Atlantic appear to be controlled more by the distribution of bottom water types than by bathymetry. In most piston cores, the assemblages vary greatly during the last 150,000 yr, suggesting depression and elevation of faunas at the core site through a depth range of several hundred meters. This would indicate that bottom water characteristics have shifted back and forth in this interval of time and, therefore, that bottom circulation partakes in the well-documented shifts recorded for surface waters of the North Atlantic. It appears that dense water, similar to present-day North Atlantic Deep Water, was produced over a wide area north of 45° N during cooler intervals and that it spread widely at depth.
Helium-Uranium Dating of Corals from Middle Pleistocene Barbados Reef Tracts
Authors: Bender Michael L. , Taylor F.T. , Matthews R.K. 
Published: December 2004

AbstractBy He-U dating of corals from elevated Pleistocene reef tracts on Barbados, we have extended back to the Middle Pleistocene the high sea stand chronology previously deduced by Th230-U dating. Six samples from the first major reef tract complex older than the 200,000-yr complex gave ages of 350,000 ± 25,000 yr B.P. Two corals from the crest of Second High Cliff, an unusually large escarpment occurring approximately midway in the terrace sequence, gave concordant ages of 480,000 and 500,000 yr. Unrecrystallized corals from older reefs gave ages ranging back to 650,000 yr.The results date episodes of high sea stands at 350,000 and 500,000 yr B.P.
Paleobotany of Wisconsinan Interstadials, Eastern Great Lakes Region, North America
Authors: Berti Albert A. 
Published: December 2004

This study concerns the pollen and plant macrofossils from Mid-Wisconsinan Interstadial sites within the Wisconsinan ice margin in eastern North America. The time period covered is from about 55,000 years BP to 22,500 years BP, an interval much longer than the postglacial. Sediments examined are principally those of large lakes deposited in the Erie and Ontario basins during intervals of ice retreat.The Port Talbot I Interval (from about 55,000 to 50,000 years BP) in the Erie basin is characterized by pollen assemblages alternating from Pinus-dominated zones to ones with abundant Pinus, Quercus, and nonarboreal pollen. These assemblages are interpreted as indicating relatively warm and dry conditions. Mean July temperatures fluctuated between 15 and 21°C.During the succeeding Port Talbot II Interval and Plum Point Interstadial, in both the Erie and Ontario basins, pollen assemblages are characterized by dominant Pinus and Picea. Characteristic macrofossils include needles of the boreal Picea and Larix and leaves of species with a more northerly distribution, such as Dryas integrifolia, Betula glandulosa var. glandulosa, Vaccinium uliginosum var. alpinum, and Salix herbacea. These fossil assemblages are interpreted as indicating cooler and moister conditions in a forest-tundra environment. Mean July temperatures fluctuated between 10 and 15°C during the Port Talbot II Interval and Plum Point Interstadial.
Landform Development on Moraines of the Klutlan Glacier, Yukon Territory, Canada
Authors: Watson R. A. 
Published: December 2004

AbstractThe landform evolution of the Klutlan moraines is described and explained primarily with respect to processes that cause voids in which debris is deposited. Morainal deposits of different ages provide examples of landforms at different stages of development, so that continuous ideal evolutionary sequences can be inferred. Specific features are classified as those on material of the same depositional age that develop mostly in a vertical direction with numerous topographic reversals, and those cross-cutting materials of different depositional age that develop primarily in a horizontal direction. The evolution of slopes is often terminated by their destruction as the underlying ice melts, but former slopes on morainal debris are traceable to ice-ridge slopes on the original glacier surface. The general process of evolution is one of downwasting by surficial icemelt, in which a grand topographic reversal takes place as the original ice mass with a gently convex surface melts to leave a basin floored by a concave mantle of morainal debris. The primary glacial process of melting differs from the primary karst process of solution, but many minor glacial processes and major glacial forms are similar to minor karst processes and major karst forms.
Paleolimnology of Two Lakes in the Klutlan Glacier Region, Yukon Territory, Canada
Authors: Bradbury J. Platt , Whiteside M. C. 
Published: December 2004

AbstractLakes developed on progressively younger end moraines of the Klutlan Glacier were initially assumed to have originated shortly after moraine emplacement and to have persisted to the present. Limnological differences between lakes on old vs young moraines were thought to result from limnological maturation within the lakes and ponds themselves and in response to the development of soils and vegetation on moraine surfaces. This study represents a paleolimnological test of this hypothesis. If true, the first-formed sediments of lakes on old moraines should be comparable to sediments presently forming in lakes on young moraines. Geochemical and paleontological studies of surface sediment to a series of lakes on progressively older moraines provide baseline information for comparing successive levels of lake sediment cores from older moraines. Results indicate that the time of lake initiation seldom reflects moraine age. Even on the oldest moraine (Harris Creek), lake basins are presently forming. Their sediment character more closely relates to the rapidity of basin formation due to melting of buried ice than to age of the lake itself or of the moraine on which it is situated. Vegetation and soil development play an important but secondary role in determining the character of lake sediments; rapid subsidence can convert humic-water lakes surrounded by second-generation spruce forests into turbid-water lakes with unstable, slumping margins. A detailed paleolimnological study of two lakes, one on the unglaciated upland and another in an outwash channel penetrating the oldest moraine, revealed progressive limnologic changes through time, suggesting that their basins were stable for 1200 and 400 yr, respectively. The changes in diatom stratigraphy of these lakes appear to relate to natural limnological changes associated with lake maturation and accumulation of nutrients as well as to changes in the surrounding vegetation and soils.
Environmental Implications of a Beetle Assemblage from the Gervais Formation (Early Wisconsinan?), Minnesota
Authors: Ashworth Allan C. 
Published: December 2004

AbstractThe Gervais Formation of northwestern Minnesota is the oldest known Quaternary stratigraphic unit in the Red River Valley. Wood from the fossiliferous silt and peat member is > 46,900 yr old. The age of the unit is uncertain but may be early Wisconsinan. A well-preserved beetle assemblage consisting of extant species is described from the fossiliferous horizon. Presently, most of the species are widely distributed and occur in Minnesota. The remainder have restricted northern distributions. Included in this group is the weevilVitavitus thulius, known only from two localities in Northwest Territories. The sedimentary environment indicated by the beetles was a small lake, rich in aquatic and semi-aquatic vegetation. The margins were characterized by open areas and spruce woodland. Species with arctic-alpine distributions indicate a cold environment, but whether it was regional or local in extent could not be determined. If regional, a climate similar to that of the tundra-forest transition zone is postulated with mean July temperatures in the range 11° to 14°C. If the cold environment was restricted, however, the climate may have been similar to that of the Lake Superior region with a mean July temperature of 17°C.
Destructive Effects of Oxygen Starvation and Ash Falls on Benthic Life: A Pilot Study
Authors: Cita Maria Bianca , Podenzani Massimo 
Published: December 2004

AbstractA quantitative study on faunal density and faunal diversity was carried out on benthic foraminifers from 15 samples of two eastern Mediterranean deep-sea cores. Samples were taken beneath, within, and above three distinctive levels well correlatable for over 1000 km: (a) Sapropel S-5, late Pleistocene in age, correlative with marine isotopic stage 5e and with the Tyrrhenian transgression, with an interpolated age of ∼ 125,000 yr: (b) the “Ischia” tephra Y-5, the most widespread ash layer of the eastern Mediterranean, correlative with the transition from isotopic stages 3 to 2 and having an interpolated age of ∼ 35,000 yr; and (c) Sapropel S-1, Holocene in age, correlative with the Flandrian transgression, radiometrically dated at ∼8000 yr B.P. The most severe effects on benthic life were induced by stagnation (a). Deglaciation corresponding to Termination II was so rapid that the benthic assemblages could not adapt themselves to the too-rapidly decreasing oxygen levels and were entirely destroyed. More than 1000 yr after the termination of stagnant conditions no recolonization had yet started. The lesser disturbance was induced in the benthic community by the ash fall (b). The faunal destruction was ephemeral in duration and the colonizing population did not differ from that predating the ash fall. A progressive faunal change, with increasing abundance of taxa tolerant to low oxygen levels, was recorded beneath Sapropel S-1 (c). The recolonizing assemblage differs from the previously existing one, and is more similar to those recorded from the floor of the Mediterranean.
Clinal Variation of Some Mammals During the Holocene in Missouri
Authors: Purdue James R. 
Published: December 2004

AbstractEastern cottontail (Sylvilagus floridanus), fox squirrel (Sciurus niger), and gray squirrel (Sciurus carolinensis) were examined for clinal variation during the Holocene. Modern samples of all three species displayed strong east-west patterns along the western edge of the eastern deciduous forest:S. floridanusandS. nigerdecrease andS. carolinensisincreases in size. Archeological samples ofS. carolinensisfrom Rodgers Shelter (23BE125), Benton County, Missouri, and Graham Cave (23MT2), Montgomery County, Missouri, indicated an increase in size from early to middle Holocene.Sylvilagus floridanusfrom Rodgers Shelter decreased in size from early to middle Holocene and then increased during the late Holocene to modern proportions. A literature survey reveals that clinal variation is a common phenomenon among modern homeotherms. In introduced species, clinal variation has developed after relatively few generations, indicating rapid adaptations to environmental conditions; often winter climatic variables are implicated. Morphological variation in the study species during the Holocene is interpreted as a response to changing climates. Studies of morphological clines may lead to another valuable data source for reconstructing past ecologies.