Climate and local controls of long-term vegetation dynamics in northern Patagonia (Lat 41°S)

2012 ◽  
Vol 78 (3) ◽  
pp. 502-512 ◽  
Author(s):  
Virginia Iglesias ◽  
Cathy Whitlock ◽  
María Martha Bianchi ◽  
Gustavo Villarosa ◽  
Valeria Outes
Keyword(s):  
Late Holocene ◽  
Vegetation Change ◽  
Late Glacial ◽  
Fire Frequency ◽  
Forest Steppe ◽  
Ecological Change ◽  
Postglacial History ◽  
New Information ◽  
History Of Vegetation ◽  
History Of

AbstractPatagonian vegetation has dramatically changed in composition and distribution over the last 16,000 yr. Although patterns of vegetation change are relatively clear, our understanding of the processes that produce them is limited. High-resolution pollen and charcoal records from two lakes located at lat 41°S provide new information on the postglacial history of vegetation and fire activity at the forest–steppe ecotone, and help clarify the relative importance of local and regional drivers of late-Holocene ecological change. Our results suggest that late-glacial parkland was colonized by shrubs at ca. 11,200 cal yr BP and this vegetation persisted until 4900 cal yr BP, when increased humidity allowed for the establishment of Nothofagus forest. The late Holocene is characterized by oscillations in forest dominance largely driven by changes in humidity, possibly associated with the onset or strengthening of ENSO. In the last 4900 yr, humid periods (4900–3800 and 2850–1350 cal yr BP) have promoted Nothofagus forest, whereas drier times (3800–2850 and 1350–450 cal yr BP) have favored Austrocedrus expansion. At intermediate moisture levels, however, the lower forest supported both taxa, and fire became an important control of community composition, with severe, infrequent fires facilitating Nothofagus regeneration and high fire frequency and intensity supporting Austrocedrus.

Postglacial vegetation and fire history of the southern Cascade Range, Oregon

2015 ◽  
Vol 84 (3) ◽  
pp. 348-357 ◽  
Author(s):  
Alicia White ◽  
Christy Briles ◽  
Cathy Whitlock
Keyword(s):  
Late Holocene ◽  
Large Scale ◽  
Fire History ◽  
Late Glacial ◽  
Fire Frequency ◽  
Cascade Range ◽  
Early Holocene ◽  
Glacial Period ◽  
Holocene Thermal Maximum ◽  
History Of

The Cascade Range of southwestern Oregon contains some of North America's most diverse forests, but the ecological history of this area is poorly understood. A 7900-yr-long pollen and charcoal record was examined to better understand past changes in vegetation and fire activity in relation to large-scale climate variability. From 7900 to 3500 cal yr BP, the dominance of xerophytic species and the frequent fires are consistent with a climate that was warmer and drier than at present. The period from 3500 cal yr BP to present experienced an abundance of mesophytic taxa and reduced fire frequency, suggesting cooler and wetter conditions. The regional history of Abies indicates that it was most widespread during the late-glacial period; its range contracted during the early Holocene thermal maximum, and it steadily expanded during the middle and late Holocene. In contrast, Pseudotsuga was restricted in range during the glacial period, became abundant at low-elevation sites in the Coast and northern Cascade ranges during the early Holocene, and was more prevalent in southern mid-elevation sites as the climate became cooler and wetter in the late Holocene. The sensitivity of these species to past climate change suggests that biogeographic responses to future conditions will be highly variable in this region.

scholarly journals History of Vegetation of Ulyanovsk City and Its Surroundings

2020 ◽  
pp. 3-14
Author(s):  
N. V. Blagoveshenskaya ◽  
Ch. T. Zamaldinova ◽  
G. V. Funk
Keyword(s):  
Late Glacial ◽  
Pine Forests ◽  
Forest Steppe ◽  
Secondary Forests ◽  
Glacial Period ◽  
Residential Areas ◽  
Late Glacial Period ◽  
History Of Vegetation ◽  
History Of ◽  
Grass Meadow

The vegetation evolution on the modern territory of the Ulyanovsk City and its surroundings, beginning from the late glacial period, can be presented as follows. 11,000– 10,300 years ago: a “tundra-steppe” with wormwood-mazy, horsetail, fern, shrubbygreen-green communities. 10,300–9,500 years ago: wormwood-haze-cenotic cenoses, isolated islets of sparse pine forests. 9,500–8,500 years ago: sagebrush-cerebral, cereal steppes and pine forests. 8,500–8,000 years ago: turf-grass, grass-meadow-grass meadow steppes and pine forests. 8,000–6,000 years ago: forbred-cereal, less often turfgrass meadow steppes, birch, and birch-pine forests, the appearance of deciduous species. 6,000–4,500 years ago: pine-broad-leaved, broad-leaved forests, mixed-grassgrass meadow steppes, and the maximum afforestation. 4,500–3,200 years ago: broadleaved, pine-broadleaf forests, and the appearance of agrocenoses. 3200–2500 years ago: pine, pine-birch forests, reduction of broad-leaved species, the expansion of turfgrass steppes and agrocenoses. 2,500–700 years ago: the emergence of secondary forests and meadow steppes (fescue, wormwood-cereal), the expansion of agrocenoses. 700–350 years ago: pine, pine-birch, pine-broadleaf forests, reduction of agrocenoses. 350 years ago till the present time: a sharp decline in forests, the predomination of secondary pine, broad-leaved, small-leaved, mixed forests and secondary meadow steppes, the expansion of agrocenoses and residential areas. Thus, the vegetation of the territory of the Ulyanovsk City and its environs since the late glacial period varied from the steppe one (11,000–8,000 years ago) to the forest-steppe one (8,000–700 years ago) and again to the steppe one (700 years ago – modern time). The least afforestation of the territory was observed from 11,000 to 9,500 years ago (3–4%) and from 350 years ago to the present (6–7%). The greatest afforestation of the forest-steppe was from 6,000 to 3,200 years ago, when the forest-to-steppe ratio was equal.

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.

Late Glacial and Holocene history of Plešné Lake and its surrounding landscape based on pollen and palaeoalgological analyses

Biologia ◽  
2006 ◽  
Vol 61 (20) ◽  
Author(s):  
Vlasta Jankovská
Keyword(s):  
Late Glacial ◽  
Forest Steppe ◽  
Southern Europe ◽  
Pollen Diagram ◽  
History Of ◽  
The Bohemian Forest ◽  
Surrounding Landscape ◽  
Late Glacial And Holocene ◽  
High Degree ◽  
Biostratigraphic Units

AbstractPollen analysis has been carried out on a 549 cm thick sediment profile from lake Plešné jezero (Plešné Lake) in the Bohemian Forest (Šumava, Czech Republic; 1090 m a.s.l.; 48°47′ N; 13°52′ E). Analyses of 67 samples characterise the development of the lake biotope and the surrounding landscape during the last ca. 14,000 years. The pollen diagram shows a very distinct transition between the Late Glacial and the Holocene biostratigraphic units at a depth of ca. 312 cm. In the surroundings of Plešné Lake the vegetation was treeless during the entire Late Glacial. The alpine tree limit, formed by Betula and Pinus with undergrowth of shrubs, might have been at ca. 500 m a.s.l. Pollen transported from long distances was significant due to the openness of the landscape, coming from southern Europe and even Africa, and including high numbers of Artemisia, Poaceae, Chenopodiaceae, and some other herbs and shrubs from steppe and forest-steppe areas in southern Europe or Africa (likely Ephedra, certainly Lygeum spartum). The expansion of shrubs, particularly Juniperus, preceded the expansion of trees near the end of the Late Glacial. Afforestation of the region by thin stands of Betula and Pinus occurred during the Preboreal. Significant warming in the Boreal resulted in the expansion of Corylus, Quercetum mixtum (QM) trees, and probably also Picea and Alnus. Picea as well as QM trees were further expanding during the Early Atlantic. Picea was the dominant tree during the Late Atlantic and Fagus started to spread towards its end. Abrupt expansion of Abies marks the Subboreal. A high degree of afforestation (Abies, Fagus, Picea) was characteristic for the Early Subatlantic. During Late Subatlantic, pollen of synanthropic plants appears. Phases of the lake biotope development were defined on the basis of coccal green algae and Isoëtes.

Late Quaternary vegetation, climate, and fire history of the Southeast Atlantic Coastal Plain based on a 30,000-yr multi-proxy record from White Pond, South Carolina, USA

2019 ◽  
Vol 91 (2) ◽  
pp. 861-880 ◽  
Author(s):  
Teresa R. Krause ◽  
James M. Russell ◽  
Rui Zhang ◽  
John W. Williams ◽  
Stephen T. Jackson
Keyword(s):  
South Carolina ◽  
Vegetation Change ◽  
Fire History ◽  
Late Quaternary ◽  
Late Glacial ◽  
Atlantic Coastal Plain ◽  
Proxy Records ◽  
Dry Conditions ◽  
History Of ◽  
Mississippian Culture

AbstractThe patterns and drivers of late Quaternary vegetation dynamics in the southeastern United States are poorly understood due to low site density, problematic chronologies, and a paucity of independent paleoclimate proxy records. We present a well-dated (15 accelerator mass spectrometry14C dates) 30,000-yr record from White Pond, South Carolina that consists of high-resolution analyses of fossil pollen, macroscopic charcoal, andSporormiellaspores, and an independent paleotemperature reconstruction based on branched glycerol dialkyl tetraethers. Between 30,000 and 20,000 cal yr BP, openPinus-Piceaforest grew under cold and dry conditions; elevatedQuercusbefore 26,000 cal yr BP, however, suggest warmer conditions in the Southeast before the last glacial maximum, possibly corresponding to regionally warmer conditions associated with Heinrich event H2. Warming between 19,700 and 10,400 cal yr BP was accompanied by a transition from conifer-dominated to mesic hardwood forest.Sporormiellaspores were not detected and charcoal was low during the late glacial period, suggesting megaherbivore grazers and fire were not locally important agents of vegetation change.Pinusreturned to dominance during the Holocene, with step-like increases inPinusat 10,400 and 6400 cal yr BP, while charcoal abundance increased tenfold, likely due to increased biomass burning associated with warmer conditions. Low-intensity surface fires increased after 1200 cal yr BP, possibly related to the establishment of the Mississippian culture in the Southeast.

scholarly journals A Holocene pollen record of savanna establishment in coastal Amapá

2008 ◽  
Vol 80 (2) ◽  
pp. 341-351 ◽  
Author(s):  
Mauro B. de Toledo ◽  
Mark B. Bush
Keyword(s):  
Vegetation Change ◽  
Human Impacts ◽  
Detrended Correspondence Analysis ◽  
Fire Frequency ◽  
Pollen Record ◽  
Human Occupation ◽  
Sample Distribution ◽  
River Flooding ◽  
History Of ◽  
Tremendous Impact

The main goal of this study was to investigate how climate and human activities may have influenced ecotonal areas of disjoint savannas within Brazilian Amazonia. The fossil pollen and charcoal records of Lake Márcio (Amapá) were used to provide a Holocene palaeoecological history of this region. Detrended correspondence analysis (DCA) was used to enhance the patterns of sample distribution along the sediment core. A marked vegetation change from closed forests with swamp elements to open flooded savanna at c. 5000 yrs BP was evident from the pollen record. Charcoal analysis revealed a pattern of increased accumulation of particles coincident with the establishment of savannas, suggesting higher fire frequency and human impacts near the lake. A 550-year sedimentary hiatus suggests that the lake depended heavily on floodwaters from the Amazon River, and that it became suddenly isolated from it. When sedimentation restarted in the lake, the environment had changed. A combination of factors, such as reduced river flooding, palaeofires and human occupation may have had a tremendous impact on the environment. As there are no other major changes in vegetation, after 4700 yrs BP, it is plausible to assume that the modern mosaic vegetation formed at that time.

scholarly journals Holocene history of fire, vegetation and land use from the central Pyrenees (France)

2012 ◽  
Vol 77 (1) ◽  
pp. 54-64 ◽  
Author(s):  
Damien Rius ◽  
Boris Vanniére ◽  
Didier Galop
Keyword(s):  
Land Use ◽  
Late Holocene ◽  
Landscape Management ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Subsequent Reduction ◽  
Human Land Use ◽  
History Of ◽  
In Fire ◽  
Central Pyrenees

Located on a mountain pass in the west-central Pyrenees, the Col d'Ech peat bog provides a Holocene fire and vegetation record based upon nine 14C (AMS) dates. We aim to compare climate-driven versus human-driven fire regimes in terms of frequency, fire episodes distribution, and impact on vegetation. Our results show the mid-Holocene (8500–5500 cal yr BP) to be characterized by high fire frequency linked with drier and warmer conditions. However, fire occurrences appear to have been rather stochastic as underlined by a scattered chronological distribution. Wetter and colder conditions at the mid-to-late Holocene transition (4000–3000 cal yr BP) led to a decrease in fire frequency, probably driven by both climate and a subsequent reduction in human land use. On the contrary, from 3000 cal yr BP, fire frequency seems to be driven by agro-pastoral activities with a very regular distribution of events. During this period fire was used as a prominent agent of landscape management.

Late Weichselian Environmental History in Southeastern Sweden during the Deglaciation of the Scandinavian Ice Sheet

1987 ◽  
Vol 28 (1) ◽  
pp. 1-37 ◽  
Author(s):  
Svante Björck ◽  
Per Möller
Keyword(s):  
Environmental History ◽  
Vegetation Change ◽  
Time Lag ◽  
Ice Sheet ◽  
Late Glacial ◽  
Climatic Data ◽  
Basal Ice ◽  
Tundra Vegetation ◽  
History Of ◽  
Late Weichselian

AbstractLate Weichselian litho-, bio-, and chronostratigraphy (14C and varves) in southeastern Sweden provide a detailed picture of the deglaciation pattern and dynamics, shore displacement, late-glacial sedimentation, and history of the landscape, vegetation, and climate. Two plausible glacial models were tested against lithologic, chronologic, and climatic data. Permafrost at and outside the ice margin and topographic conditions beneath the ice apparently caused inward spread of frozen glacier-bed conditions. This led to a buildup of a large zone of debris-rich basal ice. A climatic amelioration about 12,700 yr B.P. changed the temperature profile in the ice sheet. Deposition of basal melt-out till began at the previously frozen glacier bed, and a rapid recession of the clean ice set in; thin exposed debris-rich basal ice which was separated from the active ice margin about 150 yr later. In this zone of stagnant ice there followed a 200– 300-yr period marked by subglacial and supraglacial melt-out and resedimentation, forming a large hummocky/transverse moraine. The mild climate favored rapid plant immigration, and a park-tundra was established. The gradual closing of the landscape was interrupted by a 100- to 150-yr period of tundra vegetation and a cool, dry climate, with local vegetational differences caused by differences in soil moisture. About 12,000 yr B.P. a second climatic amelioration set in, and during the next 1000 yr a birch (and pine) woodland gradually developed. Soils stabilized and Empetrum heaths became abundant as the climate gradually deteriorated at the end of this period. By 11,000 yr B.P. the area had become a tundra again with scattered birch stands, dominated by herbs such as Artemisia, Chenopodiaceae, grasses, and sedges. Some 500 yr later a birch/pine woodland again succeeded, and within about 500 yr the vegetation changed to a rather closed woodland as the climate ameliorated further. However, the time lag between climatic and vegetation change was considerable.

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