Recent history of fire and vegetation from laminated sediment of Greenleaf Lake, Algonquin Park, Ontario

1978 ◽  
Vol 56 (1) ◽  
pp. 10-21 ◽  
Author(s):  
Les C. Cwynar
Keyword(s):  
Forest Fires ◽  
Drainage Basin ◽  
Forest Composition ◽  
Natural Phenomenon ◽  
Pollen Diagram ◽  
Sediment Samples ◽  
The Past ◽  
Lake Algonquin ◽  
Laminated Sediment ◽  
History Of

Laminated sediment (presumed varved) from Greenleaf Lake was examined for evidence of forest fires. A 500-year section dating approximately 770–1270 A.D. was analysed for influx of pollen, charcoal, aluminum, and vanadium using decadal samples. Intervals showing concurrent peaks in charcoal, aluminum, and vanadium influx, varve thickness, and charcoal:pollen ratio were interpreted as representing major fires within the drainage basin of Greenleaf Lake. By these criteria, six fires occurred within 500 years, or one fire approximately every 80 years. The pollen diagram indicates a stable forest composition for the past 1200 years. This, coupled with abundant charcoal fragments in all sediment samples, suggests that fire has been a frequent, natural phenomenon affecting the landscape during this period. There is a significant positive correspondence between peak charcoal influxes and peak influxes of aluminum and vanadium, indicating that increased soil erosion is responsible for their deposition.

Trends in the frequency, extent, and severity of spruce budworm outbreaks in eastern Canada

1983 ◽  
Vol 13 (4) ◽  
pp. 539-547 ◽  
Author(s):  
J. R. Blais
Keyword(s):  
20Th Century ◽  
Large Scale ◽  
Spruce Budworm ◽  
Forest Composition ◽  
Eastern Canada ◽  
Clear Cutting ◽  
The Past ◽  
Spruce Stands ◽  
History Of

The history of spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks for the past 200 to 300 years, for nine regions in eastern Canada, indicates that outbreaks have occurred more frequently in the 20th century than previously. Regionally, 21 outbreaks took place in the past 80 years compared with 9 in the preceding 100 years. Earlier infestations were restricted to specific regions, but in the 20th century they have coalesced and increased in size, the outbreaks of 1910, 1940, and 1970 having covered 10, 25, and 55 million ha respectively. Reasons for the increase in frequency, extent, and severity of outbreaks appear mostly attributable to changes caused by man, in the forest ecosystem. Clear-cutting of pulpwood stands, fire protection, and use of pesticides against budworm favor fir–spruce stands, rendering the forest more prone to budworm attack. The manner and degree to which each of these practices has altered forest composition is discussed. In the future, most of these practices are expected to continue and their effects could intensify, especially in regions of recent application. Other practices, including large-scale planting of white spruce, could further increase the susceptibility of forest stands. Forest management, aimed at reducing the occurrence of extensive fir–spruce stands, has been advocated as a long-term solution to the budworm problem. The implementation of this measure at a time when man's actions result in the proliferation of fir presents a most serious challenge to forest managers.

Opal phytoliths in some Victorian soils and "red rain" residues

1959 ◽  
Vol 7 (1) ◽  
pp. 64 ◽  
Author(s):  
G Baker
Keyword(s):  
Forest Fires ◽  
Tap Water ◽  
Distilled Water ◽  
Opal Phytoliths ◽  
The Past ◽  
Fundamental Significance ◽  
History Of ◽  
Red Rain ◽  
Sponge Spicules

Opaline bodies in certain Victorian soils have been regarded in the past as sponge spicules. It is now shown that the majority of these opaline bodies are the same as those developed in certain plants, hence they are recorded as opal phytoliths. This corrected identification of the opaline bodies is of fundamental significance in affecting certain aspects of the interpretation of the history of such components of soils. It is no longer necessary to consider these bodies of opal as sponge spicules carried into soils by wind transportation or other means. They are released from plants containing them and shed into the soils on the decomposition, or destruction during grass and forest fires, of phytolith-bearing vegetation, or sometimes via the dung of graminiferous animals. A few smaller phytoliths do become wind-borne, as evidenced by their occurrence in "red rain" and "red snow" residues. It is also shown that distilled water should always be used in treating soils for examination of their phytolith populations, because a small quantity of the smaller phytoliths (and diatoms) occurs in tap-water.

scholarly journals Post-Glacial climatic change on Boothia Peninsula, Nunavut, Canada

2007 ◽  
Vol 68 (2) ◽  
pp. 261-270 ◽  
Author(s):  
Susan Zabenskie ◽  
Konrad Gajewski
Keyword(s):  
Arctic Region ◽  
High Temporal Resolution ◽  
Tree Pollen ◽  
Pollen Diagram ◽  
The Core ◽  
The Past ◽  
Pollen Concentrations ◽  
History Of ◽  
Vegetation And Climate ◽  
July Temperature

AbstractA high temporal resolution pollen diagram from a lake in the mid-Arctic region of the Boothia Peninsula, Nunavut, Canada, documents the history of the regional vegetation and climate for the past 7200 yr. Major tundra pollen taxa in the core include Cyperaceae and Salix, with Cyperaceae comprising over 50% of the pollen in the early and late Holocene. Tree pollen, transported from far to the south, comprised a large percentage of the pollen sum, with Pinus accounting for 30% of the pollen in some levels of the core. Pollen percentages and concentrations of taxa typical of the mid-Arctic were highest in the mid-Holocene, corresponding to warm conditions. Decreasing pollen concentrations indicate cooling temperatures, with more rapid decreases occurring around 4200, 3800–3400, and 2500 cal yr BP. Pollen percentages of Salix, Cyperaceae, and Artemisia increased in the past 35 yr in response to global warming. Reconstructions of July temperature using the modern analog technique showed that the mid-Holocene (5800–2800 cal yr BP) was approximately 1 °C higher than during the past 1000 yr.

The Radioactivity of Sediments in Danube Reservoirs in Austria before and after the Chernobyl Accident

1990 ◽  
Vol 22 (5) ◽  
pp. 211-218 ◽  
Author(s):  
D. Rank ◽  
F. J. Maringer ◽  
J. Terlunen
Keyword(s):  
Grain Size ◽  
Major Part ◽  
Mineralogical Composition ◽  
Sediment Samples ◽  
Fine Grained ◽  
The Past ◽  
Before And After ◽  
History Of ◽  
River Reservoirs ◽  
Grain Size Fractions

A major part of pollutants transported by rivers are normally adsorbed to the fine-grained particles in suspension. The coupling between pollutants and particles leads to an enrichment of radionuclides in sediments that settle in river reservoirs and lakes. The concentration of radionuclides is a function of grain-size distribution and of the mineralogical composition. In a survey, sediment samples from the lock area of each Danube reservoir were collected during the spring of 1985. Three grain-size fractions (<20 µm, 20–63 µm, 63–250 µm) were analyzed. On an average the estimated concentration of radionuclides is about 600 Bq/kg for K-40, 50 Bq/kg for Ra-226, and 40 Bq/kg for Th-232. A 17 m depth borehole has allowed us to trace the history of radionu-clide distribution for the past 25 years since the culmination and the end of atomic testing in the atmosphere, which coincides with the damming of the river Danube at Aschach. The content of Cs-137 in freshly deposited Danube sediments rose by two orders of magnitude following the accident at Chernobyl (i.e. up to 3000 Bq/kg).

Vegetation dynamics in relation to late Holocene climate variability and disturbance, Outaouais, Québec, Canada

The Holocene ◽  
2014 ◽  
Vol 24 (11) ◽  
pp. 1515-1526 ◽  
Author(s):  
Karelle Lafontaine-Boyer ◽  
Konrad Gajewski
Keyword(s):  
Late Holocene ◽  
Detailed Comparison ◽  
Ice Age ◽  
Forest Composition ◽  
High Temporal Resolution ◽  
Pollen Record ◽  
Pollen Diagram ◽  
Short Period ◽  
History Of ◽  
Estimated Error

A pollen diagram from Lac Brulé in southwestern Québec (45°43′09″N, 75°26′32″W, 270 m) provides a late Holocene history of the vegetation. The presence of varved sediments permitted the development of a high-resolution (10-year), cross-dated chronology with an estimated error of approximately 1%. During the last 1400 years, the forests were dominated by Tsuga, Fagus, Betula, Acer and Pinus. A peak in microcharcoal and evidence of post-fire succession suggest that the changes in the pollen assemblages around ad 1375 were a consequence of a fire in the region. There was a decrease in pollen influx of several deciduous taxa and Tsuga between ad 1600 and 1700, suggesting a rapid climate change that was significant enough to have affected pollen production of these taxa. This change, associated with the beginning of the ‘Little Ice Age’ in the region, affected the forest composition for the subsequent centuries. A detailed comparison of this pollen record with that from a nearby pollen diagram also prepared at high-temporal resolution shows the ability of pollen records to record short-period climate variations and disturbances.

On The Possibility of an Autonomous History of Modern Southeast Asia

1961 ◽  
Vol 2 (2) ◽  
pp. 73-105 ◽  
Author(s):  
John R. W. Small
Keyword(s):  
Southeast Asia ◽  
Contemporary History ◽  
The Past ◽  
History Of

It is generally accepted that history is an element of culture and the historian a member of society, thus, in Croce's aphorism, that the only true history is contemporary history. It follows from this that when there occur great changes in the contemporary scene, there must also be great changes in historiography, that the vision not merely of the present but also of the past must change.

Stellar Evolution

1962 ◽  
Vol 11 (02) ◽  
pp. 137-143
Author(s):  
M. Schwarzschild
Keyword(s):  
Solar System ◽  
Stellar Evolution ◽  
Space Craft ◽  
New Techniques ◽  
Substantial Body ◽  
Individual Stars ◽  
The Past ◽  
Evolution Of Galaxies ◽  
History Of ◽  
Fast Flow

It is perhaps one of the most important characteristics of the past decade in astronomy that the evolution of some major classes of astronomical objects has become accessible to detailed research. The theory of the evolution of individual stars has developed into a substantial body of quantitative investigations. The evolution of galaxies, particularly of our own, has clearly become a subject for serious research. Even the history of the solar system, this close-by intriguing puzzle, may soon make the transition from being a subject of speculation to being a subject of detailed study in view of the fast flow of new data obtained with new techniques, including space-craft.

A 200-Year History of the Study of Childhood Language Disorders of Unknown Origin: Changes in Terminology

2020 ◽  
Vol 5 (1) ◽  
pp. 6-11 ◽  
Author(s):  
Laurence B. Leonard
Keyword(s):  
Language Impairment ◽  
Specific Language Impairment ◽  
Scientific Literature ◽  
Language Disorder ◽  
Language Disorders ◽  
Unknown Origin ◽  
Developmental Language Disorder ◽  
The Past ◽  
History Of ◽  
The Many

Purpose The current “specific language impairment” and “developmental language disorder” discussion might lead to important changes in how we refer to children with language disorders of unknown origin. The field has seen other changes in terminology. This article reviews many of these changes. Method A literature review of previous clinical labels was conducted, and possible reasons for the changes in labels were identified. Results References to children with significant yet unexplained deficits in language ability have been part of the scientific literature since, at least, the early 1800s. Terms have changed from those with a neurological emphasis to those that do not imply a cause for the language disorder. Diagnostic criteria have become more explicit but have become, at certain points, too narrow to represent the wider range of children with language disorders of unknown origin. Conclusions The field was not well served by the many changes in terminology that have transpired in the past. A new label at this point must be accompanied by strong efforts to recruit its adoption by clinical speech-language pathologists and the general public.

Suicidal Ideation Among Medical Students in Dammam, Saudi Arabia

Crisis ◽  
2020 ◽  
pp. 1-6
Author(s):  
Mohammed Madadin ◽  
Ritesh G. Menezes ◽  
Maha A. Alassaf ◽  
Abdulaziz M. Almulhim ◽  
Mahdi S. Abumadini ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Medical Students ◽  
Suicidal Ideation ◽  
General Health Questionnaire ◽  
Cross Sectional Study ◽  
Eastern Province ◽  
Cross Sectional ◽  
The Past ◽  
Depression Subscale ◽  
History Of

Abstract. Background: Medical students are at high risk of suicidal ideation. Aim: We aimed to obtain information on suicidal ideation among medical students in Dammam located in the Eastern Province of Saudi Arabia. Method: This cross-sectional study was conducted at the College of Medicine affiliated with Imam Abdulrahman Bin Faisal University in the Eastern Province of Saudi Arabia. Suicidal ideation in the past 12 months was assessed based on responses to four questions in the depression subscale of the General Health Questionnaire 28 (GHQ-28). In addition, data were collected to examine the association of suicidal ideation with various factors. Results: We found that 1 in 3 medical students in the study had suicidal ideation in the past 12 months, while around 40% had lifetime suicidal ideation. Suicidal ideation was associated with feelings of parental neglect, history of physical abuse, and dissatisfaction with academic performance. Limitations: The cross-sectional nature of this study limits its ability to determine causality regarding suicidal ideation. Conclusion: These rates are considerably high when compared with rates from studies in other countries around the world. This study provides a reference in the field of suicidology for this region of Saudi Arabia.

Post-Soviet economy development: From the past to the future

2017 ◽  
pp. 5-21 ◽  
Author(s):  
E. Yasin
Keyword(s):  
Present Situation ◽  
Soviet Economy ◽  
Market Reforms ◽  
Democratic Development ◽  
The Past ◽  
Current Period ◽  
The Future ◽  
History Of ◽  
Working Out ◽  
A Current

The article is devoted to major events in the history of the post-Soviet economy, their influence on forming and development of modern Russia. The author considers stages of restructuring, market reforms, transformational crisis, and recovery growth (1999-2011), as well as a current period which started in2011 and is experiencing serious problems. The present situation is analyzed, four possible scenarios are put forward for Russia: “inertia”, “mobilization”, “decisive leap”, “gradual democratic development”. More than 30 experts were questioned in the process of working out the scenarios.

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