Browsing by Author "Zhao, KL"

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    Climate instability during the last deglaciation in central Asia, reconstructed by pollen data from Yili Valley, NW China
    (Elsevier Science BV, 2013-02-15) Zhao, KL; Li, XQ; Dodson, JR; Zhou, XY; Atahan, P
    An extended pollen record with grain size analysis and AMS C-14 dating is provided for a palaeolake section which is located in an intermountain basin in Yili Valley, Xinjiang, NW China. Covering the late MIS 3, early MIS 2 and the last deglaciation, vegetation variations and climate events are discussed in relation to changes in pollen assemblages and Artemisia/Chenopodiaceae (A/C) ratios. The presence of montane forest-steppe dominated by Picea and Taraxacum indicates a relative humid climate in the study area during late MIS 3 (before 31.5 cal kyr BP). Picea forest disappeared and the vegetation dominated by Chenopodiaceae shows the climate became dry from 31.5 to 14.7 cal kyr BP. The sediments of Last Glacial Maximum (LGM) period are absent in the section probably. Betula-Picea mixed forest occurred at 14.7 cal kyr BP and corresponds to the onset of the warm Bolling period in the North Atlantic. A long dry period was detected from 14.5 to 13.6 cal kyr BP on the basis of the occurrence of Chenopodiaceae desert. A subalpine meadow community dominated by Geranium covered the area during 13.6-13.4 cal kyr BP, suggesting lower temperatures at this time. This may coincide with the Older Dryas (OD). The most humid period in the record occurred between 13.4 and 12.9 cal kyr BP, which coincides with the warm Allerod period. Dry conditions prevailed from similar to 12.9 to 11.7 cal kyr BP in the area, coinciding with the Younger Dryas (YD) in the North Atlantic. Within this period a three-phase climate fluctuation was detected, which can be summarized as follows: a dry early YD (12.9-12.6 cal kyr BP), a slightly moister mid-YD (12.6-12.0 cal kyr BP) and a very dry late YD (12.0-11.7 cal kyr BP). These millennial to century-scale climatic events in Yili Valley correlate well with other palaeoclimate records in North Hemisphere, suggesting that these events probably originate from same mechanisms. © 2013, Elsevier Ltd.
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    Early agricultural development and environmental effects in the Neolithic Longdong basin (East Gansu)
    (Springer Nature, 2011-03-01) Zhou, XY; Li, XQ; Zhao, KL; Dodson, JR; Sun, N; Yang, Q
    Neolithic agricultural development and environmental effects in the Longdong area were reconstructed using a synthetic approach, investigating pollen, charcoal, and seed remains for two cultural layer sections and five flotation sites. Results show that Neolithic agriculture in the Longdong area had a simple organization and was dominated by the production of common millet, especially in the early and middle Yangshao age. After the late Yangshao age, Neolithic agriculture developed into a more complex structure, dominated by both common and foxtail millet and the cultivation of rice and soybeans. The production of foxtail millet gradually increased through the Neolithic period, reaching its highest point during the Qijia culture. Soybeans were first cultivated during the late Yangshao culture, approximately 5000 cal a BP. Rice production began no later than 4800 cal a BP, and continued to exist in the Qijia culture, approximately 4000 cal a BP. Agricultural production in Neolithic Longdong, specifically in the "Yuan" area of the loess plateau, developed as a shrub and grass dominated landscape. Vegetation in the river valleys was partly covered with Picea, Tusga, and Quercus coniferous and broadleaf mixed forests. Agricultural activity during the Neolithic period caused an increase in farmland on the loess tableland and a decrease in the abundance of shrub and grassland in the Longdong area. When farmlands were abandoned, vegetation recovered with Hippophae-, Rosaceae-, Ephedra-, and Leguminosae-dominated shrublands and Artemisia-dominated grasslands. © The Author(s) 2011.
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    Early bronze in two Holocene archaeological sites in Gansu, NW China
    (Elsevier, 2009-11) Dodson, JR; Li, XQ; Ji, M; Zhao, KL; Zhou, XY; Levchenko, VA
    Understanding of the origin and development of bronze technology in eastern Asia remains unresolved. Here we report on the distribution of copper and associated cations in sediments from Huoshiliang in northwestern Gansu, China, strontium and lead isotope analyses of ore and slag samples, and some artifact fragments at archaeological sites at Ganggangwa and Huoshiliang in the Black River valley. We conclude that bronze production began perhaps as early as 2135 BC and that the Baishantang modern mine site at Dingxin was a possible source of copper ore. There was at least one other, but currently unidentified, source of ore. The Bronze Age people were also farmers and planted cereals such as wheat, and they may have abandoned the region when wood was exhausted and desertification took over. © 2009, Elsevier Ltd.
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    Impact of agriculture on an oasis landscape during the late Holocene: Palynological evidence from the Xintala site in Xinjiang, NW China
    (Elsevier Ltd., 2013-10-17) Zhao, KL; Li, XQ; Zhou, XY; Dodson, JR; Ji, M
    Pollen and charred seeds from the Xintala site within the Yanqi Oasis of Xinjiang in Northwest China were investigated to understand the impact of early agriculture on an oasis landscapes. The data show the original vegetation was meadow steppe dominated by Asteraceae and Poaceae. Wheat-growing agriculture reshaped the landscape by destroying the original vegetation and expanding the farmland area in ca. 3900-3600 cal BP. The high percentage of Typha pollen is likely to have resulted from selective harvesting of cattail for domestic uses. Persistent and probably over-irrigation may have led to an increase in soil salinity as evidenced by dramatic increases in Chenopodiaceae and Nitraria pollen percentages. The land salinization possibly resulted in the weakening of agricultural activity and later the abandonment of farmland after ca. 3600 cal BP at the Xintala site. © 2013, Elsevier Ltd.
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    The impact of early smelting on the environment of Huoshiliang in Hexi Corridor, NW China, as recorded by fossil charcoal and chemical elements
    (Elsevier, 2011-05-15) Li, XQ; Sun, N; Dodson, JR; Ji, M; Zhao, KL; Zhou, XY
    Recent research has greatly increased our knowledge of early human impacts on the environment. Records of fossil charcoal and chemical elements from a bronze smelting site at Huoshiliang, in the Hexi corridor of northwest China, provide material with which to estimate the extent of smelting activity and its impact on the environment. Analysis of the microstructure of wood fossil charcoal is used to identify the types of charred wood and to reconstruct the local vegetation present during the period of smelting. Four wood types were used as firewood for smelting: Tamarix, Populus, Salix, and Polygonaceae. The assemblages of fossil charcoal showed that Tamarix was the most dominant shrub and was widely used as firewood, as a percentage of charcoal it increased from 89% to 97% over the smelting period. Populus. Polygonaceae and Salix were much less common and finally disappeared completely. When the trees and shrubs were used as fuel, the vegetation cover was reduced and erosion rates increased. This erosion increase was recorded in the higher values of the Rb/Sr ratio in the lacustrine sediment of Tiaohu lake, located near the Huoshiliang site. The deforestation caused by smelting activity sharply reduced the vegetation coverage and had serious impacts on the environment. When the available fuel wood ceased to meet the needs of smelting and human settlement, the Huoshiliang site was eventually abandoned in about 1860 BC. (C) 2011 Elsevier B.V.
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    Moisture dynamics in central Asia for the last 15 kyr: new evidence from Yili Valley, Xinjiang, NW China
    (Elsevier, 2011-11-01) Li, XQ; Zhao, KL; Dodson, JR; Zhou, XY
    Based on high resolution palynological investigations and AMS(14)C dating, the continuous lacustrine sediments contained in Yili Valley, Xinjiang provide an opportunity to reconstruct the effective moisture changes for the last 15 kyr in central Asia. The relatively warm and humid climate of the Bolling-Allerod (15-12.9 cal kyr BP) is a generalization, but it seems to show some fluctuations. The time of the Younger Dryas (YD) interrupted the increasing trend of effective moisture in the study region, the climate was cold and relatively dry in the early YD period (12.9-12.0 cal kyr BP), whereas the desert vegetation community appeared around 11.8 cal kyr BP, almost the driest time since the 15 cal kyr BR A sharp increase in effective moisture marked the beginning of the Holocene in the Yili Valley. The early Holocene (10.6-7.6 cal kyr BP) was the wettest time with a developed temperate steppe. A dry climate with desert vegetation arose in the early mid-Holocene (7.6-6.5 cal kyr BP), spanning 1100 years. A second humid phase emerged between 6.5 and 5.2 cal kyr BP, whose vegetation community was represented by temperate steppe. Moisture was reduced again and the climate became drier between 5.2 and 3.3 cal kyr BP when vegetation was dominated by desert steppe in the Yili Valley. Regional comparisons indicate that the moisture changes in Yili Valley were mainly influenced by the North Atlantic Ocean SSTs through the westerlies. The mean position of the Siberian High Pressure cell probably made a great contribution to the drought between 7.6 and 6.5 cal kyr BP. The climate changes were generally consistent between the westerly-dominant central Asia and Asian monsoon regions since the last deglaciation, possibly forced by summer insolation conditions in the Northern Hemisphere. (C) 2011 Elsevier Ltd.
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    Origin and spread of wheat in China
    (Elsevier, 2013-07-15) Dodson, JR; Li, XQ; Zhou, XY; Zhao, KL; Sun, N; Atahan, P
    Wheat was added as a new crop to the existing millet and rice based agricultural systems of China. Here we present 35 radiocarbon ages from wheat seeds collected from 18 sites between western (Xinjiang Province) and eastern (Henan Province) China. The earliest wheat ages cluster around 2100–1800 BCE in northern China's Hexi corridor of Gansu Province, where millet was already a well-established crop. Wheat first appears in Xinjiang and Henan about 300–400 years later, and perhaps a little earlier than this in Xinjiang, and we hypothesize that the likely route of wheat into China was via Russia through Gansu. © 2013, Elsevier Ltd.
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    Plant diversity of the Tianshui Basin in the western Loess Plateau during the mid-holocene - charcoal records from archaeological sites
    (Elsevier, 2013-10-02) Sun, N; Li, XQ; Dodson, JR; Zhou, XY; Zhao, KL; Yang, Q
    Assessing the potential impact of increased temperature needs examination of robust palaeorecords that contain analogues. The fossil charcoal (anthracological) records from the mid-Holocene archaeological sites can provide palaeo-analogues on the impacts of climate change. The Xishanping and Dadiwan sites were continuously developed during the Neolithic Culture in the Tianshui Basin, western Loess Plateau. A total of 24 samples of were recovered using a floatation method. At least 100 fragments were examined from each sample, and these fragments were identified following standard procedures, and the results were used to reconstruct the vegetation and plant diversity between 5200 and 4300 cal BP, which was a warm period for the region. The charcoal evidence from the Xishanping and Dadiwan sites confirm that woody plants were widely available, including temperate taxa such as Betula, Ulmus, Quercus, Carpinus, Acer, Corylus and Padus, and typical subtropical taxa such as Bambusoideae, Liquidambar formosana, Castanopsis, Pseudotsuga sinensis, and Eucommia ulmoides. The assemblages of fossil charcoal show that mixed forests of north-subtropical evergreen and deciduous broadleaved trees existed. This is a broader range of woody plants than at present in the Tianshui Basin. This leads to the conclusion that the warmer and increasing monsoon precipitation resulted in a northward shift in the southern vegetation zones. And that the natural botanical diversity between 5200 and 4300 cal BP was also greater than at present in the Tianshui Basin, western Loess Plateau. © 2013, Elsevier Ltd and INQUA.
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    Use of coal in the bronze age in China
    (Sage, 2014-03-03) Dodson, JR; Li, XQ; Sun, N; Atahan, P; Zhou, XY; Liu, HB; Zhao, KL; Hu, SM; Yang, ZM
    People in northern and western China were probably the first in the world to use coal as a source of energy in a consistent way. The ages cluster around 1900–2200 BC in modern day Inner Mongolia and Shanxi provinces. These are areas where near-surface coal is abundant today and woody vegetation was scant in the Bronze Age. Since coal is bulky to transport, it was probably not a cost-effective energy source in areas with abundant wood supply. The sites where coal was first used were probably occupied for a century to a few centuries at most and were associated with Bronze Age societies. The earliest age is about 3490 BC from a house site at Xiahe in Shaanxi Province; however, the coal is not securely tied to the radiocarbon ages and is assumed to have been used at this site sometime after 3490 BC. The elemental composition of modern mine and sedimentary coal in nearby archaeological contexts suggests that coal was used from local sources, and that elemental composition of coal may be a useful tool in identifying site origin of coal.
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    Vegetation characteristics in the western Loess plateau between 5200 and 4300 cal. B.P. based on fossil charcoal records
    (Springer, 2013-01-01) Li, XQ; Sun, N; Dodson, JR; Zhou, XY; Zhao, KL
    Understanding terrestrial vegetation dynamics is a crucial tool in global change research. The Loess Plateau, an important area for the study of Asian monsoons and early agriculture, poses a controversial question on the potential vegetation and its pattern. Fossil charcoal as direct evidence of wood provides precision in species identification and hence vegetation reconstruction. Charcoals from the Dadiwan and Xishanping sites suggest a great variety of plants between 5200 and 4300 cal. b.p. in the valley area of the western Loess Plateau. The deciduous broad-leaf wood from Quercus, Ulmus, Betula, Corylus and Acer is very frequent and makes up almost half the total abundance ratio of the represented taxa. Meanwhile, some typical subtropical taxa such as Liquidambar formosana, Eucommia ulmoides, Toxicodendron and Bambusoideae, are present at the two study sites. The high abundance of Picea appearing between 5200 and 4300 cal. b.p. suggests the development of Picea forests in the valley of the western Loess Plateau. The assemblages of charcoal indicate that the mixed forest of evergreen deciduous and conifer-deciduous broadleaved trees developed in the valley of the Loess Plateau during the Holocene optimum. Precipitation is the main controlling factor for forest development. The increasing precipitation is the probable reason for the appearance of north-subtropical forests between 5200 and 4300 cal. b.p. © 2013, Springer.
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    Zonal vegetation change in the Chinese Loess Plateau since MIS 3
    (Elsevier Science, 2014-06-15) Zhou, XY; Li, XQ; Dodson, JR; Yang, SL; Long, H; Zhao, KL; Sun, N; Yang, Q; Liu, HB
    Three pollen records from different regions of the Chinese Loess Plateau (CLP) show that the zonal differentiation of vegetation was not large in late MIS 3 time, all the areas were covered by warm semi-humid grass-shrub land, with some conifer-broad leaf mixed forest in the valleys. It appears that the zonal differentiation of vegetation nearly disappeared in the Last Glacial Maximum (LGM), while the semi-arid steppe expanded to the southern margin of the CLP. During the Holocene Thermal Maximum (HTM), the zonal differentiation became complex, with warm humid forest in the southeastern part and semi-arid steppe in the northern CLP. The zonal degree of vegetation differentiation of the CLP decreased again during the late Holocene as a result of climate change and increasing human influence on the landscape. In recent centuries, the transformation of the grass communities caused by land clearance for agriculture on the loess tablelands has been significant. © 2014, Elsevier Ltd.