Search

Depth to water table (DWT, the depth from the water surface to the top of the peat surface) is one of the most important environmental variables related to the habitat types and distribution of vegetation within a subalpine peatland. The distribution of phytolith assemblages and basic environmental data from 43 surface soil samples with significant ecological and hydrological gradients were investigated to generate transfer functions for quantitative reconstruction of paleoenvironmental changes in Dajiuhu peatland, central China. Detrended correspondence analysis (DCA) and redundancy analysis (RDA) were employed to explore the relationship between main environmental variables and phytolith morphotypes and distributions. Our results indicate that the spatial distribution of phytoliths was significantly correlated with the DWT (25% variance), total organic carbon (TOC, 10% variance) and magnetic susceptibility (χ, 7% variance). We established the transfer functions for the significant variables based on modern analogue technique (MAT), weighted averaging techniques (WA) and weighted averaging partial least squares (WA-PLS), and model performance was assessed using bootstrap cross-validation. The high correspondence of the predicted DWT results based on phytolith-environment calibration data with observed data reflects that the phytolith-based WA-PLS is a reliable effective calibration method for the quantitative DWT reconstruction of ombrotrophic (rain-fed) subalpine peatland. [ABSTRACT FROM AUTHOR]

In order to explore the impacts of past climate changes on the origin and evolution of Lake Poyang, the biggest freshwater lake in China, eight periods of palaeoenvironmental changes were constructed to depict the history of climate change over the past 3500 years based on the palynological records and carbon isotopic excursions. The climate regime was associated with the presence of a deciduous and evergreen broad-leaved forest/a mixed needle broad-leaved forest and strong/weak solar variability. Palaeohydrology change reconstructed by the percentage of aquatics and stable carbon isotopes demonstrated that the wet episode was associated with the developed lacustrine facies and enhanced El Niño–Southern Oscillation (ENSO) activities. The presence of the united open lake (Lake Poyang) during 2000–1200 cal. a BP was linked to a long wet period caused by the strong ENSO activities. At the decadal-centennial timescales, climate changes together with the ENSO activities might have played a great role on the regional hydrological condition and sedimentary evolution in southern Lake Poyang. The correlations of the palaeotemperature and palaeohydrology with the multi-proxy data from the Northern Hemisphere all suggest that palaeotemperature change with the monsoon intensity is linked to the solar variations, but palaeohydrology change has a striking consistency with the ENSO activities. The distinct hydrothermal diversification (warm-wet, warm-dry, cold-wet, cold-dry) revealed by the palaeotemperature and palaeohydrology changes will provide important clues about the origin and evolution of Lake Poyang in the Holocene and a better understanding of the interactions between solar radiation, ENSO activity and lake deposition in the middle Yangtze River Valley. [ABSTRACT FROM AUTHOR]

Integrated sedimentological and clay mineral analyses of a 300-m-depth core reveal the history of the palaeo-lake and palaeoclimatic evolution of the southern Datong Basin over the past 800 ka. The sedimentary facies, including deep lake, shallow lake, alternation of lakeside and shallow lake, and the river environment are identified based on the general characteristics of the grain size analysis. Two episodes of warm–humid events are responsible for the palaeo-lake expansion during the period of 800–480 ka, corresponding to the presence of S7, S6, and S5 in the Loess Plateau. A stepwise cooling and drying trend since approximately 480 ka is strongly linked to the gradual shrinkage and extinction of the palaeo-lake. Our results demonstrated that climate change has played an essential role on the palaeo-lake expansion/shrinkage during the Middle Pleistocene. Breaching of Shixia Gorge by active neotectonic movement since the middle Late Pleistocene enhanced the shrinkage and extinction of the palaeo-lake, coupled with a cold–dry climate in the Last Glacial. The climatic changes documented by clay minerals and grain size parameters in the Datong Basin are consistent with the loess–paleosol sequences in the Loess Plateau and fluvio-lacustrine sediments in the Nihewan Basin, mainly controlled by the East Asian Monsoon in response to the regional global change since the Mid-Late Pleistocene. [ABSTRACT FROM AUTHOR]

Abstract: A variety of phytoliths, together with prolific microcharcoal particles, sponge spicules and diatoms were extracted and identified in four cultural layers from an archeological site at Jinluojia, Macheng, Hubei Province, Central China. The warmth (Iw) and aridity (Iph) indices calculated from grass phytoliths reveal warm and wet periods during the West Zhou, early East Zhou, Tang and Song Dynasties whilst cool and dry periods occurred during the late East Zhou, Ming and Qing Dynasties. The paleoclimate conditions reconstructed on the basis of grass phytoliths extracted from archeological sediments are in agreement with those from natural sediments in the Middle Yangtze region. In contrast, the woody phytoliths show a positive correlation with microcharcoal particles, suggesting an anthropogenic contribution to the woody phytoliths from the use of woody plants for fuel during cooking and heating. Two episodes of the enhanced abundance of woody phytoliths and microcharcoal particles were found to occur at East Zhou Dynasty and from Ming and Qing Dynasties to the Present, proposed to be a consequence of the population expansion and/or the frequent wars. [Copyright &y& Elsevier]