Origine et évolution du marais tourbeux de Keswick, Ontario, par l'analyse pollinique et macrofossile

1986 ◽  
Vol 23 (8) ◽  
pp. 1145-1155 ◽  
Author(s):  
H. Dinel ◽  
P. J. H. Richard ◽  
P. E. M. Levésque ◽  
A. Larouche
Keyword(s):  
Plant Communities ◽  
Mixed Forest ◽  
Climatic Conditions ◽  
Vegetation Changes ◽  
Silty Clay ◽  
Field Site ◽  
Deciduous Species ◽  
Hardwood Species ◽  
History Of ◽  
Lake Simcoe

The objectives of the present study were to explain the origin and to reconstitute the different phases of the paleovegetation of the Keswick marsh, Ontario. Palynological evidence was used to key out the regional and extra-local paleovegetation, and macrofossils analysis served to establish the history of the vegetation at the field site. The data showed that in the vicinity of Lake Simcoe the origin of the marsh was closely associated with the changes in the climatic conditions that favored the development of an environment suitable for peat-forming plant communities; 2.4 m of peat accumulated in the last 4000 years on a washed silty clay. The macrofossils of hardwood species, seeds of Aralia racemosa, and sporangia of Polypodiaceae at the base of the deposit indicated that a mixed forest, composed mainly of deciduous species surrounded by tamaracks, prevailed prior to the initiation of peat accumulation. Furthermore, additional vegetation changes occurred, notably the replacement of an arboreal swamp vegetation by an herbaceous marsh, followed by a shrub–herb marsh and then an herbaceous marsh, recently drained and cultivated.

Hydrological changes in the Rzecin peatland (Puszcza Notecka, Poland) induced by anthropogenic factors: Implications for mire development and carbon sequestration

The Holocene ◽  
2016 ◽  
Vol 27 (5) ◽  
pp. 651-664 ◽  
Author(s):  
Krystyna Milecka ◽  
Grzegorz Kowalewski ◽  
Barbara Fiałkiewicz-Kozieł ◽  
Mariusz Gałka ◽  
Mariusz Lamentowicz ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Plant Communities ◽  
Human Activity ◽  
Accumulation Rate ◽  
Carbon Accumulation ◽  
Anthropogenic Factors ◽  
Poor Fen ◽  
History Of ◽  
Carbon Accumulation Rates

Wetlands are very vulnerable ecosystems and sensitive to changes in the ground water table. For the last few thousand years, hydrological balance has also been influenced by human activity. To improve their cropping features, drainage activity and fertilizing were applied. The drainage process led to an abrupt change of environment, the replacement of plant communities and the entire ecosystem. The problem of carbon sequestration is very important nowadays. A higher accumulation rate is related to higher carbon accumulation, but the intensity of carbon sequestration depends on the type of mire, habitat, and climatic zone. The main aim of this article was an examination of the changes in poor-fen ecosystem during the last 200 years in relation to natural and anthropogenic factors, using paleoecological methods (pollen and macrofossils). The second aim was a detailed investigation of the sedimentary record to aid our understanding of carbon sequestration in the poor fen of temperate zone. This case study shows that fens in temperate zones, in comparison with boreal ones, show higher carbon accumulation rates which have been especially intensive over the last few decades. To reconstruct vegetation changes, detailed palynological and macrofossil analyses were done. A 200-year history of the mire revealed that it was influenced by human activity to much degree. However, despite the nearby settlement and building of the drainage ditch, the precious species and plant communities still occur.

Late-glacial and Post-glacial history of the Chalk escarpment near Brook, Kent

1964 ◽  
Vol 248 (745) ◽  
pp. 135-204 ◽  
Keyword(s):  
Bronze Age ◽  
Iron Age ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Valley Floor ◽  
Glacial Period ◽  
Late Neolithic ◽  
Local Conditions ◽  
Arable Farming ◽  
History Of

This paper describes the morphology of a small piece of the Chalk escarpment near Brook in east Kent, and reconstructs its history since the end of the Last Glaciation. The escarpment contains a number of steep-sided valleys, or coombes, with which are associated deposits of chalk debris, filling their bottoms and extending as fans over the Gault Clay plain beyond. Here the fans overlie radiocarbon-dated marsh deposits of zone II (10 000 to 8800 B.C.) of the Late-glacial Period. The debris fans were formed and the coombes were cut very largely during the succeeding zone III (8800 to 8300 B.C.). The fans are the products of frost-shattering, probably transported by a combination of niveo-fluvial action and the release of spring waters; intercalated seams of loess also occur. The molluscs and plants preserved in the Late-glacial deposits give a fairly detailed picture of local conditions. The later history of one of the coombes, the Devil’s Kneadingtrough, is reconstructed. The springs have effected virtually no erosion and have probably always emerged more or less in their present position. In the floor of the coombe the periglacial chalk rubbles of zone III are covered by Postglacial deposits, mainly hillwashes. They are oxidized and yield no pollen, but contain rich faunas of land Mollusca, which are presented in the form of histograms revealing changing local ecological and climatic conditions. During most of the Post-glacial Period, from the end of zone III until about the beginning of zone VIII, very little accumulation took place on the coombe floor. But below the springs there are marsh deposits which span much of this interval. They yield faunas of considerable zoogeographical interest. The approximate beginning of zone VII a (Atlantic Period) is reflected by a calcareous tufa, which overlies a weathering horizon, and represents an increase in spring flow. Two clearance phases are deduced from the molluscan record. The first may have taken place at least as early as the Beaker Period (Late Neolithic/earliest Bronze Age); the second is probably of Iron Age ‘A’ date. In Iron Age times the subsoil was mobilized and a phase of rapid hillwashing began. As a result the valley floor became buried by humic chalk muds. The prime cause of this process was probably the beginning of intensive arable farming on the slopes above the coombe; a possible subsidiary factor may have been the Sub-Atlantic worsening of climate. The muds yield pottery ranging in date from Iron Age ‘Kentish first A’ ( ca . 500 to ca . 300 B.C.) to Romano-British ware of the first or second centuries A.D. Evidence is put forward for a possible climatic oscillation from dry to wet taking place at about the time of Christ. In the later stages of cultivation, possibly in the Roman Era, the valley floor was ploughed and given its present-day form.

Effects of long-term protection from grazing on phenotypic expression in geographically separated mountain rough fescue populations

2014 ◽  
Vol 94 (1) ◽  
pp. 33-39 ◽  
Author(s):  
D. J. Thompson ◽  
W. D. Willms
Keyword(s):  
Plant Communities ◽  
Phenotypic Expression ◽  
Highly Sensitive ◽  
History Of ◽  
Genetic Makeup ◽  
Rough Fescue ◽  
Geographic Sources ◽  
Lake Site ◽  
Summer Grazing

Thompson, D. J. and Willms, W. D. 2014. Effects of long-term protection from grazing on phenotypic expression in geographically separated mountain rough fescue populations. Can. J. Plant Sci. 94: 33–39. Whether or not long-term grazing or protection from grazing alters the genetic makeup of grass populations has been debated. Mountain rough fescue [(Festuca campestris (Rydb.)], which is highly sensitive to summer grazing, and becomes dominant in plant communities with long-term protection, was chosen to address this question. Plants from three geographic sites (Stavely in AB, Milroy in the Kootenay trench, BC and Goose Lake on the BC interior plateau) with divergent grazing histories were vegetatively propagated from tillers. Daughter plants were planted into two field nurseries (at Kamloops, BC, and Stavely, AB) and morphological measurements were taken in two field seasons post-establishment. Plants from all three populations were taller, flowered earlier, and were more productive at the Kamloops nursery site. Of the three geographic sources, plants from the Goose Lake site were most distinct with narrower leaves, later flowering, and greater yield. Plants with a long history of grazing had slightly shorter fertile tillers and leaves than plants with a history of long-term protection.

Natural history of a plant trait: branch-system abscission in Paleozoic conifers and its environmental, autecological, and ecosystem implications in a fire-prone world

Paleobiology ◽  
10.1666/12030 ◽  
2013 ◽  
Vol 39 (2) ◽  
pp. 235-252 ◽  
Author(s):  
Cindy V. Looy
Keyword(s):  
Fire Regime ◽  
Climatic Conditions ◽  
Early Permian ◽  
North Central ◽  
Seasonally Dry ◽  
Plant Trait ◽  
Branch System ◽  
Central Texas ◽  
History Of ◽  
Biotic Disturbance

Within conifers, active abscission of complete penultimate branch systems is not common and has been described mainly from juveniles. Here I present evidence for the abscission of penultimate branch systems within early so-called walchian conifers—trees with a plagiotropic branching pattern. The specimens studied originate from a middle Early Permian gymnosperm-dominated flora within the middle Clear Fork Group of north-central Texas. Complete branch systems of three walchian conifer morphotypes are preserved; all have pronounced swellings and smooth separation faces at their bases. The source plants grew in a streamside habitat under seasonally dry climatic conditions. The evolution of active branch abscission appears to correspond to an increase in the size of conifers, and this combination potentially contributed to the restructuring of conifer-rich late Paleozoic landscapes. Moreover, trees shedding branch systems and producing abundant litter have the potential to affect the fire regime, which is a factor of evolutionary importance because wildfires must have been a source of frequent biotic disturbance throughout the hyperoxic Early Permian.

scholarly journals Three new Cenomanian conifers from El Chango (Chiapas, Mexico) offer a snapshot of the geographic mosaic of the Mesozoic conifer decline

2021 ◽  
Author(s):  
Ixchel Gonzalez-Ramirez ◽  
Sergio RS Cevallos-Ferriz ◽  
Carl Rothfels
Keyword(s):  
Evolutionary History ◽  
Mixed Forest ◽  
Freshwater Ecosystems ◽  
Total Evidence ◽  
Morphological Data ◽  
Phylogenetic Position ◽  
Dominant Group ◽  
Geographic Mosaic ◽  
History Of ◽  
Rare Opportunity

Premise of study: El Chango is a recently discovered quarry that contains extremely well preserved fossils. The Cenomanian age of the locality corresponds to a time when the global flora was transitioning from gymnosperm- to angiosperm-dominated, yet conifers predominate in this locality. These fossils thus provide a rare opportunity to understand the replacement of conifers by angiosperms as the dominant group of plants. Methods: We collected material from El Chango in annual expeditions (2010 to 2014). We selected the three most abundant and best preserved conifer morphotypes and conducted a total-evidence (i.e., including molecular and morphological data) phylogenetic analysis of a sample of 72 extant conifer species plus the three fossils. We use these results to inform our taxonomic decisions. Results: We obtained four equally most-parsimonious trees (consistency index = 44.1%, retention index = 78.8%). Despite ambiguous relationships among some extant taxa, the three fossil conifers had the same phylogenetic position in all four most parsimonious trees; we describe these species as new: Sequoiadendron helicalancifolium sp. nov. (Cupressaceae), and Microcachrys rhomboidea sp. nov. and Dacrydium bifoliosus sp. nov (Podocarpaceae). The ecosystem is interpreted as a coastal humid mixed forest. Conclusions: Our findings contribute to the understanding of Cenomanian equatorialregions, and support the hypothesis of a geographically and ecologically structured rise of angiosperms, with conifers remaining dominant in brackish-water and angiosperms becoming dominant in freshwater-ecosystems. These fossils fill in gaps in the evolutionary history of lineages like Microcachrys, which we demonstrate occurred in the Northern hemisphere before becoming restricted to its current range (Tasmania).

scholarly journals The First Korean Garden in Russia

2021 ◽  
pp. 102-112
Author(s):  
Victor Kuzevanov ◽  
Alexey Ponomarev ◽  
Sergey Kalyuzhny ◽  
Yong-Shik Kim
Keyword(s):  
Science Education ◽  
International Cooperation ◽  
Climatic Conditions ◽  
State University ◽  
Design Development ◽  
Botanic Garden ◽  
Garden Design ◽  
Natural Heritage ◽  
History Of ◽  
Selection Of

The history of the first «Korean Garden» design, development and establishment within the Irkutsk State University Botanic Garden in the harsh climatic conditions of Baikalian Siberia is described. The peculiarities of the selection of plants and landscape arrangements represent this garden as a unique ethnobotanical object – the cultural and natural heritage of Korea, an ecological and humanitarian resource for science, education and international cooperation.

scholarly journals Codling-moth Investigations of the State Entomologist's Office

1922 ◽  
Vol 14 (1-10) ◽  
pp. 219-289 ◽  
Author(s):  
P. A. Glenn
Keyword(s):  
Life History ◽  
Codling Moth ◽  
Climatic Conditions ◽  
The State ◽  
Accurate Data ◽  
Rate Of Development ◽  
History Of ◽  
Seasonal History

To secure accurate data in regard to the life history and the seasonal history of the codling-moth in Illinois, and the relation of climatic conditions to the rate of development and the time of appearance of the various stages of the insect, an investigation was begun in the spring of 1915 under the direction of Doctor S. A. Forbes, then State Entomologist.

scholarly journals Deserters, Spies and Kumanists»: Some Episodes from the Peasants’ Everyday Life in Perm Province in the Second Half of 1919

TECHNOLOGOS ◽  
2021 ◽  
pp. 112-122
Author(s):  
Dolgova Anzhela
Keyword(s):  
Civil War ◽  
Everyday Life ◽  
Climatic Conditions ◽  
Criminal Cases ◽  
Social Phenomena ◽  
Archival Documents ◽  
Long Time ◽  
History Of ◽  
Main Thing ◽  
The Village

The article is devoted to the history of the peasants’ everyday life in 1919. The basis is archival documents presenting four criminal cases: two murders, torture and malfeasance. Using comparative historical and typological methods the author showed how peasants from different districts of Perm province reacted to the events in the village. A causal analysis of the links between historical events made it possible to identify the general patterns of the considered social phenomena and processes among the peasantry. The history of everyday life is relevant to this day. It is impossible to study historical facts without addressing this topic. The peasantry constituted the majority of the country's population, and therefore was a kind of indicator of the ongoing internal political changes in the country. The life of the peasants in each region of the country had its own characteristics. It depended on the natural and climatic conditions, the standard of living, and the social composition of the population. The civil war showed that interference in the life of peasants could change their social appearance. The war imbalanced the life of the village for a long time, destroyed social ties, and led to senseless human casualties. The cited archival documents, in a way, are the episodes from peasants’ life in a certain period of time. As long as the author's goal was to convey the era of war the documents are given in the form in which they have survived to this day: with the preservation of spelling, punctuation and style. Due to the absence of editorial revision in them a picture of complex relationship in the village opens up the tragic events unfold with the forced participation of peasants. It becomes clear what the norm was for them and what was the main thing in their life - justice or legality. The peasants’ attitude towards life and death had been changed during the Civil War. Life lost its value, and death began to be perceived as something ordinary and inevitable.

scholarly journals The fluvial history of Mars

2012 ◽  
Vol 370 (1966) ◽  
pp. 2193-2215 ◽  
Author(s):  
Michael H. Carr
Keyword(s):  
Climatic Conditions ◽  
River Channels ◽  
Erosion And Deposition ◽  
Running Water ◽  
The Earth ◽  
Outflow Channels ◽  
History Of ◽  
Valley Networks ◽  
River Valleys ◽  
Steep Slopes

River channels and valleys have been observed on several planetary bodies in addition to the Earth. Long sinuous valleys on Venus, our Moon and Jupiter's moon Io are clearly formed by lava, and branching valleys on Saturn's moon Titan may be forming today by rivers of methane. But by far the most dissected body in our Solar System apart from the Earth is Mars. Branching valleys that in plan resemble terrestrial river valleys are common throughout the most ancient landscapes preserved on the planet. Accompanying the valleys are the remains of other indicators of erosion and deposition, such as deltas, alluvial fans and lake beds. There is little reason to doubt that water was the erosive agent and that early in Mars' history, climatic conditions were very different from the present cold conditions and such that, at least episodically, water could flow across the surface. In addition to the branching valley networks, there are large flood features, termed outflow channels. These are similar to, but dwarf, the largest terrestrial flood channels. The consensus is that these channels were also cut by water although there are other possibilities. The outflow channels mostly postdate the valley networks, although most are still very ancient. They appear to have formed at a time when surface conditions were similar to those that prevail today. There is evidence that glacial activity has modified some of the water-worn valleys, particularly in the 30–50° latitude belts, and ice may also be implicated in the formation of geologically recent, seemingly water-worn gullies on steep slopes. Mars also has had a long volcanic history, and long, sinuous lava channels similar to those on the Moon and Venus are common on and around the large volcanoes. These will not, however, be discussed further; the emphasis here is on the effects of running water on the evolution of the surface.

Palynology and Paleoecology of Postglacial Sediments from the Lower Fraser River Canyon of British Columbia

1975 ◽  
Vol 12 (5) ◽  
pp. 745-756 ◽  
Author(s):  
R. W. Mathewes ◽  
G. E. Rouse
Keyword(s):  
Tsuga Heterophylla ◽  
Climatic Conditions ◽  
Douglas Fir ◽  
Fraser River ◽  
Pollen Assemblage ◽  
Glacial Ice ◽  
Transitional Area ◽  
Postglacial History ◽  
History Of Vegetation ◽  
History Of

The postglacial history of vegetation in the Yale area of the lower Fraser River Canyon is described from sediments of two lakes using percentage pollen analysis supplemented with macrofossil evidence and radiocarbon dating. Deposition of postglacial sediments, ranging from basal clays to gyttjas, began about 11 500 y B.P. Three distinct pollen assemblage zones are distinguished, reflecting in part the main climatic conditions for the intervals. The oldest zone, with high percentages of pine (Pinus) and alder (Alnus) pollen, suggests cool and moist conditions following withdrawal of glacial ice. This is followed by marked increases in Douglas-fir (Pseudotsuga), grasses and other nonarboreal pollen, suggesting in part, warmer and drier conditions. The third zone, ranging from about the Mt. Mazama ash at 6600 y B.P. to the present, is marked by high alder and Douglas-fir, and increasing cedar (Thuja-Chamaecyparis type), western hemlock (Tsuga heterophylla), fir (Abies) and birch; an assemblage indicating a return to wetter conditions. This sequence contrasts with previously described successions that recognized the classical Hypsithermal in adjacent areas. The sequence of inferred vegetational changes, although similar to those described for the Haney area to the west, suggests that the Yale area has been a biogeoclimatically transitional area for much of postglacial time.

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