scholarly journals Environmental and climatic changes in central Chilean Patagonia since the Late Glacial (Mallín El Embudo, 44° S)

2014 ◽  
Vol 10 (3) ◽  
pp. 1063-1078 ◽  
Author(s):  
M. E. de Porras ◽  
A. Maldonado ◽  
F. A. Quintana ◽  
A. Martel-Cea ◽  
O. Reyes ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Regional Scale ◽  
Late Glacial ◽  
Climatic Changes ◽  
Landscape Configuration ◽  
Effective Moisture ◽  
Nothofagus Forest ◽  
Chilean Patagonia ◽  
Fire Activity ◽  
Southern Westerlies

Abstract. Multi-millennial environmental and climatic changes in central Chilean Patagonia (44–49° S) during the Last Glacial–Interglacial cycle have been of particular interest as changes in the position and strength of the southern westerlies are the major forcing factor conditioning the environmental dynamics. Recent attempts to reconstruct regional environmental and climatic signals from central Chilean Patagonia reveal some discrepancies and unclear issues among the records. This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44° 40' S, 71° 42' W) located in the deciduous Nothofagus forest in the middle Río Cisnes valley. The paper aims to (1) establish the timing and magnitude of local vegetation changes and fire activity since the Late Glacial and (2) integrate these results at the regional scale in order to discuss the discrepancies and depict the environmental and climatic dynamics in central Chilean Patagonia since the Late Glacial. Open landscapes dominated by grasses associated with scattered Nothofagus forest patches dominated the middle Río Cisnes valley between 13 and 11.2 ka suggesting low effective moisture but also indicating that landscape configuration after glacial retreat was still ongoing. At 11.2 ka, the sudden development of an open and quite dynamic Nothofagus forest probably associated with the synchronous high fire activity occurred, suggesting a rise in effective moisture associated with dry summers. Since 9.5 ka, the record reflects the presence of a closed Nothofagus forest related to higher effective moisture conditions than before combined with moderate dry summers that may have triggered a high frequency of low-magnitude crown fires that did not severely affect the forest. The forest experienced a slight canopy opening after 5.7 ka, probably due to slightly drier conditions than before followed by a sudden change to open forest conditions around 4.2 ka associated with fire and volcanic disturbances. Around 2 ka, the recovery of a closed Nothofagus forest related to slightly wetter conditions (similar to present) occurred and persisted under highly variable climatic conditions up to 0.1 ka when massive forest burning and logging due to European settlements occurred. Central Chilean Patagonian climatic and environmental changes at millennial–centennial timescales since the Late Glacial were driven by changes in the southern westerlies latitudinal position and/or intensity, but during the late Holocene fire, volcanism and humans arose as forces contributing to environmental dynamics.

scholarly journals Environmental and climatic changes in Central Chilean Patagonia since the Late Glacial (Mallín El Embudo, 44° S)

2013 ◽  
Vol 9 (5) ◽  
pp. 5747-5784
Author(s):  
M. E. de Porras ◽  
A. Maldonado ◽  
F. A. Quintana ◽  
A. Martel-Cea ◽  
O. Reyes ◽  
...  
Keyword(s):  
Regional Scale ◽  
Late Glacial ◽  
Climatic Changes ◽  
Landscape Configuration ◽  
Effective Moisture ◽  
Nothofagus Forest ◽  
Chilean Patagonia ◽  
Precipitation Seasonality ◽  
Fire Activity ◽  
Southern Westerlies

Abstract. Multi-millennial environmental and climatic changes in Central Chilean Patagonia (44–49° S) during the Last Glacial–Interglacial cycle have been of particular interest as changes in the position and strength of the Southern Westerlies are the major forcing factor conditioning the environmental dynamics. Recent attempts to reconstruct regional environmental and climatic signals from Central Chilean Patagonia reveal some discrepancies and unclear issues among the records. This paper presents the 13 ka pollen and charcoal records from Mallín El Embudo (44°40' S; 71°42' W) located in the deciduous Nothofagus forest in the middle Río Cisnes valley. The paper aims to (1) establish the timing and magnitude of local vegetation changes and fire activity since the Late Glacial and (2) integrate these results at the regional scale in order to discuss the discrepancies and depict the Central Chilean Patagonia environmental and climatic dynamics since Late Glacial. Open landscapes dominated by grasses associated with scattered Nothofagus forest patches dominated middle Río Cisnes valley between 13–11.2 ka suggesting low effective moisture but also reflecting that landscape configuration after glacial retreat was still ongoing. At 11.2 ka, a sudden development of an open and quite dynamic Nothofagus forest probably associated to the synchronous high fire activity occurred suggesting a rise in effective moisture. Since 9.5 ka, the record reflects the presence of a closed Nothofagus forest related to higher/similar effective moisture conditions than before but under an unmarked precipitation seasonality. The forest experienced a slight canopy opening since 5.7 ka, probably due to slightly drier conditions than before followed by a sudden change around 4.2 ka associated with fire and volcanic disturbances. The recovery of an open Nothofagus forest related to slight wetter conditions (similar to present) occurred around 2 ka and persisted under highly variable climatic conditions up to 0.1 ka when massive forest burning and logging due to European settlements occurred. Central Chilean Patagonian climatic and environmental changes at millennial-centennial time scales since Late Glacial were driven by changes in the Southern Westerlies latitudinal shift and/or intensity but during the Late Holocene fire, volcanism and humans arise as major forcings contributing to environmental dynamics.

Climate and vegetation change during the late-glacial/early-Holocene transition inferred from multiple proxy records from Blacktail Pond, Yellowstone National Park, USA

2013 ◽  
Vol 79 (3) ◽  
pp. 391-402 ◽  
Author(s):  
Teresa R. Krause ◽  
Cathy Whitlock
Keyword(s):  
Climate Change ◽  
Yellowstone National Park ◽  
National Park ◽  
Pinus Contorta ◽  
Vegetation Change ◽  
Environmental Changes ◽  
Regional Scale ◽  
Late Glacial ◽  
Early Holocene ◽  
Fire Activity

AbstractA series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.

scholarly journals Biotic response to rapid climatic changes during the Late Glacial : high resolution biostratigraphies and biological processes

2008 ◽  
Vol 63 (3) ◽  
pp. 160-166 ◽  
Author(s):  
B. Ammann ◽  
U. Eicher ◽  
J. Schwander ◽  
U. von Grafenstein ◽  
K. Nováková ◽  
...  
Keyword(s):  
Climatic Change ◽  
Environmental Changes ◽  
Dimensional Space ◽  
Late Glacial ◽  
Climatic Changes ◽  
Life Cycles ◽  
Ecological Niches ◽  
Biological Processes ◽  
Terrestrial Vegetation ◽  
Biotic Response

Abstract. Organisms can respond to rapid climatic changes in three ways: 1) adaptation by evolution, affecting physiology and morphology), 2) migration and population dynamics including biogeographical changes) and 3) extinction local or global). Here, the focus is on examples of the second type. Organisms, whether algae, trees, or animals, find their ecological niches in a multi- dimensional space of gradients such as temperature winter, summer, means or extremes), humidity soil or air), pH, various nutrients, light. Presence or absence of taxa species, genera, families) can be related to such gradients. With training sets based on current gradients, they can also be related to environmental changes of the past e. g. summer mean temperatures or pH). The relationships between the occurrence of taxa and environmental variables can also be used to examine the biotic response to changes based on other proxies, for example, changes in temperature inferred from oxygen- isotope ratios in carbonates or from the content in organic matter of lake sediments. The groups of organisms referred to here are plants pollen), insects chironomids) and other aquatic invertebrates. The three Late Glacial periods with very high rates of change in temperature estimates are the transition from the Oldest Dryas to the Bölling from GS- 2 to GI- 1 in the Late Glacial, ca. 14 670 cal yr BP), and the beginning and the end of the Younger Dryas ca. 12 600 cal yr BP, 11 500 cal yr BP respectively). The « classical » hypothesis was that trees represented in pollen diagrams) respond more slowly to climatic change than invertebrates aquatic or terrestrial) because of differences in life cycles. But it is shown here that terrestrial vegetation) and aquatic invertebrate) ecosystems may respond synchronously. Three major biological processes are involved in the responses to climatic change: 1) Migration – can be slow if, for example, a longliving tree migrated back from a southern refugium. 2) Build- up of populations – intermediate velocity, for the process needs time depending on the life cycles of the organisms. 3) Productivity – can change rapidly, within a year or a few years e. g. pollen productivity, tree rings). The first two of these processes occur on the organisational level of populations, the last one on the level of the individual. These processes develop also in various combinations.

scholarly journals A high-altitude peatland record of environmental changes in the NW Argentine Andes (24 ° S) over the last 2100 years

2016 ◽  
Vol 12 (5) ◽  
pp. 1165-1180 ◽  
Author(s):  
Karsten Schittek ◽  
Sebastian T. Kock ◽  
Andreas Lücke ◽  
Jonathan Hense ◽  
Christian Ohlendorf ◽  
...  
Keyword(s):  
High Altitude ◽  
Environmental Changes ◽  
Regional Scale ◽  
Central Andes ◽  
High Accumulation ◽  
Climate Conditions ◽  
Climate Anomalies ◽  
Dry Conditions ◽  
Induced Changes ◽  
The 19Th Century

Abstract. High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies, and sensitivity to climatic and/or human-induced changes. Especially within the Central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP), located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF), stable isotope and element content analyses (δ13C, δ15N, TN and TOC) were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatlands' past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that in situ moisture changes were coupled to the migration of the Intertropical Convergence Zone (ITCZ). A period of sustained dry conditions prevailed from around 150 BC to around AD 150. A more humid phase dominated between AD 200 and AD 550. Afterwards, the climate was characterised by changes between drier and wetter conditions, with droughts at around AD 650–800 and AD  1000–1100. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption) seems to have had an impact on climatic settings in the Central Andes. In the past, the peatland recovered from climatic perturbations. Today, CTP is heavily degraded by human interventions, and the peat deposit is becoming increasingly susceptible to erosion and incision.

scholarly journals Stepwise Weakening of Aeolian Activities During the Holocene in the Gannan Region, Eastern Tibetan Plateau

2021 ◽  
Vol 9 ◽  
Author(s):  
Shengli Yang ◽  
Xiaojing Liu ◽  
Ting Cheng ◽  
Yuanlong Luo ◽  
Qiong Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Environmental Changes ◽  
Climatic Changes ◽  
Early Holocene ◽  
Eastern Tibetan Plateau ◽  
Aeolian Desertification ◽  
The Holocene ◽  
Aeolian Sediments ◽  
Aeolian Activity ◽  
History Of

Aeolian sediments hold key information on aeolian history and past environmental changes. Aeolian desertification and extensive land degradation have seriously affected the eco-environment in the Gannan region on the eastern Tibetan Plateau. Understanding the history of aeolian activities can deepen our understanding of the impacts of climatic changes on aeolian activities in the future. This study uses a detailed chronology and multiple proxy analyses of a typical aeolian section in Maqu to reconstruct aeolian activities in the region during the Holocene. Our results showed that aeolian activities have occurred in the eastern Tibetan Plateau since the early Holocene. Magnetic susceptibility, grain size records, and paleosols formation indicated a trend of stepwise weakening in aeolian activities from the early Holocene to the present. The weakening of aeolian activities was divided into three stages: ∼10.0–8.0 ka BP, ∼8.0–4.0 ka BP, and ∼4.0 ka BP to the present. Paleosols were primarily formed after ∼8.0 ka BP, and episodically interrupted aeolian activities processes in the Gannan region. Aeolian activity may increase in the Gannan region as the climate gradually warms. Climatic changes and local hydrological conditions have jointly affected the history of aeolian activities in this region.

scholarly journals Can the subterranean fauna be used as proxy for past environmental changes? – the example of the Carpathians cave fauna

2018 ◽  
Vol 1 ◽  
Author(s):  
Oana Teodora Moldovan ◽  
Ionut Cornel Mirea ◽  
Marius Kenesz
Keyword(s):  
Environmental Changes ◽  
Regional Scale ◽  
Environmental Parameters ◽  
General View ◽  
Carpathian Mountains ◽  
Small Areas ◽  
The Carpathians ◽  
Cave Fauna ◽  
Historical Processes ◽  
Geological Units

Carpathian Mountains were one of the main refuge areas during the climate changes of the Pleistocene and the Holocene in Europe and one of the richest regions in the world in subterranean (caves and associated habitats) endemic species. Nevertheless, the Carpathian Mountains subterranean fauna importance is underestimated especially due to dispersed information on its diversity and the scarcity of molecular studies in the area. Here, we present a first general view of the cave fauna hotspot represented by the Romanian Carpathians and the geological and historical processes that shaped the patterns of subterranean distribution and diversity at regional scale. The Carpathians are an amalgam of various geological units with complex paleogeographical evolution that is reflected in completely different species assemblages dominated by unit specific fauna groups. Phylogeography of Coleoptera and environmental parameters are adding to the general view at regional scale and offer additional explanation for this exceptional subterranean diversification in a non-Mediterranean region. We also use the example of the Carpathians cave fauna as proxy for past environmental changes in the area. Troglobionts are endemic on small areas and by studying their present distributions and phylogeny, past processes of landscape evolution on the surface can be better understood.

The Changing American West

2016 ◽  
Author(s):  
Gregory L. Simon
Keyword(s):  
American West ◽  
Environmental Changes ◽  
Fire Risk ◽  
Urban Fringe ◽  
Analytic Approach ◽  
The West ◽  
Fire Activity ◽  
Social Environmental ◽  
Activity Trends ◽  
Synoptic View

This chapter establishes a conceptual justification for the implementation of an affluence-vulnerability interface analytic approach to manage current and prospective suburban landscapes—indeed a major characteristic of the West is the immense amount of land currently still eligible for suburban and exurban conversion. Along with this important land characteristic, it provides a synoptic view of the rapidly transforming West more generally through a discussion of recent suburbanization, climatic, and fire activity trends. Most importantly “the Incendiary” is introduced as a metaphor for treating the suburban West like a troubled patient (an arsonist) with deeply held and engrained behaviors and characteristics. The chapter suggests that engaging the West as merely a flammable landscape is to confront symptoms of the Incendiary, while confronting the Incendiary itself is to treat the essential character and core mechanisms driving growth and social-environmental changes in high fire risk landscapes at the urban fringe.

scholarly journals Key Environmental Factors Controlling Planktonic Foraminiferal and Pteropod Community’s Response to Late Quaternary Hydroclimate Changes in the South Aegean Sea (Eastern Mediterranean)

2020 ◽  
Vol 8 (9) ◽  
pp. 709
Author(s):  
Christina Giamali ◽  
George Kontakiotis ◽  
Efterpi Koskeridou ◽  
Chryssanthi Ioakim ◽  
Assimina Antonarakou
Keyword(s):  
Environmental Factors ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Eastern Mediterranean ◽  
Planktonic Foraminifera ◽  
Explanatory Power ◽  
Principal Component ◽  
Aegean Sea ◽  
Late Glacial ◽  
The South

A multidisciplinary study was conducted in order to investigate the environmental factors affecting the planktonic foraminiferal and pteropod communities of the south Aegean Sea. Aspects of the Late Quaternary paleoceanographic evolution were revealed by means of quantitative analyses of planktonic foraminiferal and pteropod assemblages (including multivariate statistical approach; principal component analysis (PCA)), the oxygen (δ18O) and carbon (δ13C) isotopic composition of planktonic foraminifera and related paleoceanographic (planktonic paleoclimatic curve (PPC), productivity (E-index), stratification (S-index), seasonality) indices, extracted by the gravity core KIM-2A derived from the submarine area between Kimolos and Sifnos islands. Focusing on the last ~21 calibrated thousands of years before present (ka BP), cold and eutrophicated conditions were identified during the Late Glacial period (21.1–15.7 ka BP) and were followed by warmer and wetter conditions during the deglaciation phase. The beginning of the Holocene was marked by a climatic amelioration and increased seasonality. The more pronounced environmental changes were identified during the deposition of the sapropel sublayers S1a (9.4–7.7 ka BP) and S1b (6.9–6.4 ka BP), with extremely warm and stratified conditions. Pteropod fauna during the sapropel deposition were recorded for the first time in the south Aegean Sea, suggesting arid conditions towards the end of S1a. Besides sea surface temperature (SST), which shows the highest explanatory power for the distribution of the analyzed fauna, water column stratification, primary productivity, and seasonality also control their communities during the Late Quaternary.

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