The Desertification Analysis of Mongolia using Grain Size Index and Vegetation Cover Index

2017 ◽  
Vol 19 (1) ◽  
pp. 73-86
Author(s):  
Sulderdene Erdenesumbee ◽  
Geun Sang Lee ◽  
Yun Woong Choi ◽  
Jang Ki Song ◽  
Gi Sung Cho
Keyword(s):  
Grain Size ◽  
Vegetation Cover ◽  
Size Index

The impact of Dansgaard–Oeschger cycles on the loessic environment and malacofauna of Nussloch (Germany) during the Upper Weichselian

2008 ◽  
Vol 70 (1) ◽  
pp. 91-104 ◽  
Author(s):  
Olivier Moine ◽  
Denis-Didier Rousseau ◽  
Pierre Antoine
Keyword(s):  
Grain Size ◽  
Environmental Changes ◽  
Ice Core ◽  
Schematic Model ◽  
Climatic Fluctuations ◽  
Climatic Oscillations ◽  
The North ◽  
Size Index ◽  
The Impact ◽  
Hygrophilous Species

AbstractA loess sequence has been sampled continuously at high resolution in Nussloch (Rhine Valley, Germany) for malacological and grain-size analyses between ca. 34 and 20 ka. Molluscan abundance and richness, percentage in hygrophilous species and grain-size index show cyclical variations related to the lithological loess–gley alternation. Major molluscan abundance maxima were triggered by temperature increases through an enhancement of the reproduction cycle, whereas cyclical richness fluctuations and percentage in hygrophilous species reflect variations in local humidity and changes in the environmental mosaic. Malacological parameters allow the distinction of four environmental phases organised in cyclical successions correlated with most of the loess–gley doublets. The correlation of the grain-size index of the Nussloch loess sequence with the dust content of the GRIP ice core demonstrates the synchronicity of major molluscan abundance maxima and δ18O increases characterising temperature increases during Dansgaard–Oeschger interstades. A schematic model is proposed to link the North Atlantic Dansgaard–Oeschger climatic oscillations with local environmental changes indicated by both malacofauna and pedostratigraphy. This malacological study of the Nussloch loess sequence thus provides new information about the response of terrestrial loessic palaeoenvironments to millennial-timescale climatic fluctuations during the Upper Weichselian (∼ marine isotope stage 2 (MIS 2) and end of MIS 3).

Mechanical behavior of silty soils of the Venice lagoon as a function of their grading characteristics

2002 ◽  
Vol 39 (4) ◽  
pp. 879-893 ◽  
Author(s):  
Simonetta Cola ◽  
Paolo Simonini
Keyword(s):  
Grain Size ◽  
Mechanical Behavior ◽  
Laboratory Investigation ◽  
Venice Lagoon ◽  
Soil Response ◽  
Regular Trend ◽  
Size Index ◽  
Geological Origin ◽  
Silty Soils ◽  
Historic City

The main feature of the shallowest quaternary basin of the well-renowned historic city of Venice, Italy and its surrounding lagoon, is the presence, apparently without any regular trend in depth and site, of a predominant silt fraction. This is always combined with clay and (or) sand, forming a chaotic and erratic interbedding of different sediments whose mineralogy is however variable in a relatively narrow range due to a unique geological origin and a common depositional environment. After a brief description of the basic soil indexes of the Venice lagoon soil, the present study, based on a comprehensive geotechnical laboratory investigation, describes the range of variation of the most relevant time-independent geotechnical properties. Moreover, a new grain size index, combining the geometrical characteristics of the particle distribution, is introduced. It is shown that the soil response at large and very small strains can be related to this grain size index, which appears to be able to include the influence of the soil grading on the description of the overall mechanical behavior.Key words: silt, mechanical behavior, Venice soil, grain-size index, laboratory investigation, critical state parameters.

scholarly journals North Atlantic abrupt climatic events of the Last Glacial period recorded in Ukrainian loess deposits

2010 ◽  
Vol 6 (5) ◽  
pp. 1959-1990
Author(s):  
D.-D. Rousseau ◽  
P. Antoine ◽  
N. Gerasimenko ◽  
A. Sima ◽  
M. Fuchs ◽  
...  
Keyword(s):  
Grain Size ◽  
North Atlantic ◽  
Western Europe ◽  
Climate Modeling ◽  
Ice Cores ◽  
The North ◽  
Recent Climate ◽  
Size Index ◽  
Loess Deposits ◽  
Western European

Abstract. Loess deposits are widely distributed in the Northern Hemisphere, where they have recorded not only the glacial-interglacial cycles, but also millennial-timescale changes resembling those in marine and ice cores. Such abrupt variations are clearly marked in Western European series, but have not yet been evidenced in the east of the continent. Here we present results of the high-resolution investigation of a Weichselian Upper Pleniglacial loess sequence (~38–15 ka) from Stayky, Ukraine. The stratigraphy shows an alternation of loess horizons and embryonic soils, similar to sequences from Western Europe. Similarities are also found between variations of a grain-size index (ratio between coarse and fine material fractions) in Stayky and in Western European profiles. Based on these similarities, and in agreement with the luminescence dates, the embryonic soils are associated to the Greenland interstadials (GIS) 7 to 2, and the Vytachiv paleosol at the base of the sequence, to GIS 8. Pollen analysis indicates a wetter climate for these interstadials, allowing the development of arboreal vegetation, than for the stadials, marked by loess formation. The grain-size index reaches the highest values for intervals correlated with the Heinrich events 3 and 2. Thus, it appears that the North Atlantic abrupt climate changes have extended their influence and modulated the loess sedimentation at least as far as in Eastern Europe. This result is supported by recent climate modeling experiments, and recommends the Stayky sequence as a reference for further comparisons between profiles along the Eurasian loess belt centered at 50° N.

scholarly journals Reconstruction of Holocene hydroclimatic variability in subarctic treeline lakes using lake sediment grain-size end-members

The Holocene ◽  
2018 ◽  
Vol 28 (6) ◽  
pp. 845-857 ◽  
Author(s):  
Andrew L Macumber ◽  
R Timothy Patterson ◽  
Jennifer M Galloway ◽  
Hendrik Falck ◽  
Graeme T Swindles
Keyword(s):  
Grain Size ◽  
Lake Sediment ◽  
Vegetation Cover ◽  
Ice Age ◽  
Coarse Silt ◽  
Climate Trends ◽  
Sediment Grain Size ◽  
The Past ◽  
Hydroclimatic Variability ◽  
End Members

Current climate trends are expected to result in the northward expansion of the subarctic treeline leading to changes in vegetation cover and permafrost distribution, as they did during the Holocene Climate Optimum when the treeline was 150 km north of its current position. The impacts of these changes on the region’s hydrology are still poorly understood. The grain-size distributions of treeline lake sediments provide an important proxy related to spring melt conditions that can be used to reconstruct hydroclimatic variability. End-member mixing analysis was used to model depositional end-members in 55 modern lake sediment samples and two sediment cores spanning the mid- to late Holocene collected from above and below the treeline in the central Northwest Territories, Canada. Cold climatic intervals (e.g. ‘Dark Ages Cold Period’, ‘Little Ice Age’) were characterised by an increase in the very coarse silt and the fine sand end-members. This was interpreted to be a response to degradation of vegetation cover and/or permafrost development. We observed increases in fine and coarse silt end-members during warmer climatic intervals (e.g. Medieval Climate Anomaly) and over the past c. 300 yr BP. This pattern is probably the result of extended melt seasons, with greater losses to evaporation and increased infiltration. The most pronounced palaeo-hydroclimatological change over the past c. 8000 yr BP was the abrupt increase in a very coarse silt end-member (mode = 50–200 µm) at c. 6300 yr BP. We interpreted the sedimentological change as an increase in winter precipitation and more energetic spring melt conditions, leading to the spring melt becoming the dominant lacustrine sediment delivery mechanism. These results place modern hydrological changes in a millennial context and show that analysis of temporal changes in the hydroclimatological system can provide insight into the future states of these sensitive subarctic ecosystems.

scholarly journals Desertification Information Extraction Based on Feature Space Combinations on the Mongolian Plateau

2018 ◽  
Vol 10 (10) ◽  
pp. 1614 ◽  
Author(s):  
Haishuo Wei ◽  
Juanle Wang ◽  
Kai Cheng ◽  
Ge Li ◽  
Altansukh Ochir ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Land Surface ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Feature Space ◽  
Gobi Desert ◽  
Landsat 8 ◽  
Mongolian Plateau ◽  
Size Index ◽  
Modified Soil

The Mongolian plateau is a hotspot of global desertification because it is heavily affected by climate change, and has a large diversity of vegetation cover across various regions and seasons. Within this arid region, it is difficult to distinguish desertified land from other land cover types using low-quality vegetation information. To address this, we analyze both the effects and the applicability of different feature space models for the extraction of desertification information with the goal of finding appropriate approaches to extract desertification data on the Mongolian plateau. First, we used Landsat 8 remote sensing images to invert NDVI (normalized difference vegetation index), MSAVI (modified soil adjusted vegetation index), TGSI (topsoil grain size index), and albedo (land surface albedo) data. Then, we constructed the feature space models of Albedo-NDVI, Albedo-MSAVI, and Albedo-TGSI, and compared their extraction accuracies. Our results show that the overall classification accuracies of the three models were 84.53%, 85.60%, and 88.27%, respectively, indicating that the three feature space models are feasible for extracting information relating to desertification on the Mongolian plateau. Further analysis indicates that the Albedo-NDVI model is suitable for areas with a high vegetation cover or a high forest ratio, whilst the Albedo-MSAVI model is suitable for areas with relatively low vegetation cover, and the Albedo-TGSI model is suitable for areas with extremely low vegetation cover, including the widely distributed Gobi Desert and other barren areas. This study provides a technical selection reference for the investigation of desertification of different zones on the Mongolian plateau.

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