Wheat and barley evolved from large-seeded annual grasses in the arid, low latitudes of Asia; their spread into higher elevations and northern latitudes involved corresponding evolutionary ...adaptations in these plants, including traits for frost tolerance and shifts in photoperiod sensitivity. The adaptation of farming populations to these northern latitudes was also a complex and poorly understood process that included changes in cultivation practices and the varieties of crops grown. In this article, we push back the earliest dates for the spread of wheat and barley into northern regions of Asia as well as providing earlier cultural links between East and West Asia. The archaeobotanical, palynological and anthracological data we present come from the Tongtian Cave site in the Altai Mountains, with a punctuated occupation dating between 5,200 and 3,200 calibrated years BP, coinciding with global cooling of the middle-late Holocene transition. These early low-investment agropastoral populations in the north steppe area played a major role in the prehistoric trans-Eurasian exchange.
The issue of the communication and transfer of agricultural practices between the ancient West and East is being increasingly addressed. The Hexi corridor, which lies on the main path of the ancient ...Silk Road, is one of the most important relevant study areas. Here we report the results of an archaeobotanical study based on the analysis of flotation samples and AMS 14C dating of eight sites in the Hexi corridor. The results show that rain-fed millet agriculture in eastern China spread westwards to the Hexi Corridor as early as 2300 BC; and that wheat began to be cultivated at approximately 2000 BC, becoming the dominant crop at approximately 1700 BC. This agricultural transformation in the prehistoric Hexi Corridor occurred over some 200 years. In addition, wild soybeans were probably also cultivated at the same time, and the gathering of fruit (Nitraria) and nuts (Corylus) may have supplemented the food supply.
Based on high resolution palynological investigations and AMS
14C 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 Bølling-Allerød (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 BP. 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.
► New evidence of moisture evolution for the last 15 kyr in central Asia. ► Wettest climatic conditions occurred from 10.6 to 7.6 cal kyr BP. ► Dry conditions arose at 7.6–6.5 cal kyr BP and 5.2–3.3 cal kyr BP. ► Our record correlates well with records from North Atlantic and monsoonal Asia. ► The moisture changes were mainly influenced by the North Atlantic Ocean SSTs.
The bacterial membrane lipid-based continental paleothermometer, the MBT/CBT or MBT′–CBT proxy (methylation index of branched tetraethers/cyclization of branched tetraethers), results in a large ...temperature deviation when applied in semiarid and arid regions. Here we propose new calibration models based on the investigation of >100 surface soils across a large climatic gradient, with a particular focus on semiarid and arid regions of China, and apply them to a loess–paleosol sequence. As reported elsewhere, MBT values exhibit a much higher correlation with MAAT than with summer temperature, suggesting a minimal seasonality bias; however, MBT is apparently insensitive to temperature <5°C or >20°C. Additional complexities are apparent in alkaline and arid soils, which are characterized by different relationships to climatic parameters than those in the complete Chinese (or global) dataset. For example, MBT and CBT indices exhibit a negative correlation in alkaline and arid soils, in contrast to their positive correlation in acid soils. Moreover, the cyclization ratio of bGDGTs (CBT), previously defined as a proxy for soil pH, is apparently primarily controlled by MAAT in these alkaline soils. Thus, we propose (1) a local Chinese calibration of the MBT–CBT proxy and (2) an alternative temperature proxy for use in semiarid and arid regions based on the fractional abundances of bGDGTs; the latter has a markedly higher determination factor and lower root mean square error in alkaline soils than the Chinese local calibration and is suggested to be preferred for paleotemperature reconstruction in Chinese loess/paleosol sequences. These new bGDGT proxies have been applied to the Weinan Holocene paleosol section of the Chinese Loess Plateau (CLP). The fractional abundance calibration, when applied in the Weinan Holocene paleosol, produces a total Holocene temperature variation of 5.2°C and a temperature for the topmost sample that is consistent with the modern temperature. Previously, we showed that the ratio of archaeal isoprenoid GDGTs to bGDGTs (Ri/b) increases at MAP<600mm, and elevated Ri/b values (>0.5) in the CLP suggest the presence of enhanced aridity in the late Holocene in North China. In combination, the high Ri/b ratios (>0.5) and the associated low MBT values (<0.4) reveal the co-occurrence of dry and cold events, especially in the latest Holocene, in the loess–paleosol sequences in CLP, and probably also in cold and arid regions outside of CLP.
Origin and spread of wheat in China Dodson, John R.; Li, Xiaoqiang; Zhou, Xinying ...
Quaternary science reviews,
07/2013, Letnik:
72
Journal Article
Recenzirano
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.
•Wheat was introduced into eastern Asia before 3000 BCE.•35 New dates indicates the oldest ages clutter in Gansu.•Wheat appears in areas previously dominated by millet crops.•Wheat appears to spread from Gansu over the next 300–400 years.
Many studies have been carried out to understand the nature of the loess formation and its palaeoenvironmental significance in different parts of Eurasia, especially Europe and China. However, in ...spite of its key position, our knowledge about the loess deposits at the core of the Eurasian loess belt in central Asia is still limited, particularly in terms of absolute dating. This study presents a new luminescence chronology of a loess-palaeosol sequence (Rudak section) in the vicinity of the Gissar Range, Uzbekistan, using both quartz optically stimulated luminescence dating and polymineral post-IR IRSL dating techniques. The dating results suggested a loess accumulation history over the past 180 kyr at Rudak section, characterized by a great depositional hiatus during the entire last glacial period, likely owing to too harsh climate conditions for favouring dust accretion and loess preservation in the piedmont areas of central Asia. Hence, contrasting with the traditional concept of continuous (quasi-continuous) deposition of loess, the direct stratigraphical correlation might be problematic for climatic interpretation of loess-palaeosol sequence in this area. Furthermore, magnetic susceptibility of Rudak section demonstrated the moisture peaks in phase with ice-volume minima over the glacial and interglacial cycles, indicating moisture variation in the Westerlies-dominated central Asia was broadly consistent with that in monsoonal Asia on orbital timescales, but nearly contrasting picture with each other on the suborbital timescales, at least through the Holocene epoch. The Westerlies-dominated central Asia has generally experienced a dry first half and a wet second half of the Holocene, which has likely been driven by solar insolation gradients between mid-latitudes and high-latitudes as well as the melt-water flux.
•This study presents a new luminescence chronology of a loess-palaeosol sequence from Uzbekistan.•The ages are based on both quartz OSL and polymineral post-IR IRSL dating techniques.•A great depositional hiatus during the entire last glacial period is revealed in the loess section.•Moisture peaks of central Asia are in phase with ice-volume minima over the orbital time scales.•Central Asia experienced a contrasting Holocene moisture pattern compared with monsoonal Asia.
The Tibetan Plateau, which is climatically dominated by the westerlies and the Asian monsoon, has a major influence on the atmospheric circulation and water resources of Asia. However, it remains ...unclear of the long‐term (e.g., millennial‐ and orbital‐scale) status and origin of the water resources in the plateau. In this study, we used the presence of a long‐distance pollen component (e.g., Tsuga) in a sedimentary section from eastern Pamir as a tracer to characterize the air movements in the western Tibetan Plateau during the late Holocene. Based on modern backward trajectory analysis, we suggest that the pollen of Tsuga was transported by the paleo‐monsoon from the southeastern Tibetan Plateau to eastern Pamir during the late Holocene (e.g., 3,200–1,750 cal years B.P.). Our findings provide evidence of paleo‐monsoon movement and potential moisture transport paths from the southeastern Tibetan Plateau to eastern Pamir during the late Holocene.
Plain Language Summary
The modern climate of the Pamir area in the western Tibetan Plateau is dominated by the westerlies that supply more than 70% of the precipitation. Several glaciers occur in the Pamir area, and they are an important water source for major rivers such as the Indus, Amudarya, and Yankuet. We conducted a fossil pollen study of late Holocene sediments in the eastern Pamir area and found some airborne pollen types, including several subtropical taxa (e.g., Tsuga, Platycarya, Anacardiaceae, and Meliaceae). Backward trajectory analysis revealed that the Tsuga pollen grains were transported from the southeastern Tibetan Plateau to eastern Pamir by the paleo‐monsoon during the late Holocene. The paleo‐monsoon movement and potential moisture transport paths identified in this study provide a reference for monsoon simulation and atmospheric circulation monitoring in the western Tibetan Plateau.
Key Points
Long‐distance‐transported pollen (e.g., Tsuga) was identified in late Holocene sediments in eastern Pamir
The Tsuga pollen was transported by the paleo‐monsoon from the southeastern Tibetan Plateau to the eastern Pamir
The Tsuga pollen indicates paleo‐monsoon movement and potential moisture transport paths in the western Tibetan Plateau
The question of what the ecology communities of the Loess Plateau looked like before the extensive anthropogenic reshaping processes of the late-Holocene has stirred a long debate. A better ...understanding of these human-induced changes will not only help us understand the extent of paleoeconomic practices, but also inform future conservation actions on this ecologically fragile landscape. This paper presents a systematic study of wood charcoal from a series of archaeological sites, demonstrating that woody plants and woodlands were widely distributed and geographically diverse on the Loess Plateau in response to the East Asian Monsoon. In the Guanzhong Basin, oak (Quercus spp.) woodlands were associated with a few tropical-subtropical taxa, which changed to oak and pine (Pinus spp.) mixed forests on the eastern plateau, while on the northern plateau coniferous woodlands were dominant. On the western Loess Plateau, oak and elm (Ulmus spp.) woodland and spruce (Picea spp.) forests were widespread. The charcoal results suggest that human impacts on the dominant species might have begun as early as ca. 3500 cal yr BP, with oak replaced by Prunus as the dominant taxon, including many economically significant species, such as peaches (P. persica) and apricots (P. armeniaca). Furthermore, the charcoal data show that due to warm and wet climatic conditions in the mid-Holocene, the distribution of tropical-subtropical taxa shifted markedly northwards into the Guanzhong and Tianshui Basins, and the central part of the eastern Loess Plateau, which became characterized by high frequencies of Bamboo.
Increasing lines of evidence question the homogenous response of Asian Summer Monsoon (ASM) precipitation patterns, requiring rethinking of the forcing mechanisms. Here we show a ~15,000‐year ...quantitative precipitation history based on well‐dated lake levels at Lake Chenghai, subtropical China. Lake levels and the inferred precipitation were high during the Bølling‐Allerød, early and late Holocene, but low during the middle Holocene. The orbital scale precipitation trend is out of phase with boreal summer insolation, the later has been widely suggested as the driver of ASM precipitation. Lake Chenghai long‐term lake levels are synchronous with trends in tropical Pacific sea surface temperatures, the related zonal sea surface temperature gradients, and interhemispheric temperature gradients. We propose that changes in either the interhemispheric or zonal Pacific temperature gradients modulate the intensity and location of the western Pacific subtropical high, which is juxtaposed on the ASM, leading to heterogeneous hydroclimatic conditions over subtropical East Asia.
Plain Language Summary
We present a 15,000‐year record of southern China precipitation based on well‐dated (n=130 radiometric ages) lake level variations of a closed basin lake. The reconstructed long‐term southern China precipitation trend is out of phase with boreal summer insolation, which has been shown to drive ASM precipitation, but broadly follows trends in tropical Pacific sea surface temperatures (SSTs), the related zonal SST gradients, and interhemispheric temperature gradients. We propose that changes in either the interhemispheric or zonal Pacific temperature gradients modulate the intensity and location of the western Pacific subtropical high and are juxtaposed on the ASM, leading to heterogeneous hydroclimatic conditions over subtropical East Asia, including an unexpected southern China mid‐Holocene drought. The results of this study are unique in that (1) precipitation was robustly reconstructed from beach evidence, which is a first‐order measure of the balance between rainfall amount and evaporation. (2) A new mechanism driving long‐term precipitation changes over subtropical East Asia is proposed. Providing the mechanism stands, increasing SST gradients under the expected global warming scenario could enhance the role of western Pacific subtropical high and lead to less precipitation over subtropical East Asia.
Key Points
A 15,000‐year precipitation history over subtropical China was reconstructed based on well‐dated (n=130 radiometric ages) lake levels
Subtropical China precipitation trend does not resemble Asian summer monsoon trend but is synchronized with trends in tropical Pacific SST
Juxtaposition of western Pacific subtropical high on Asian summer monsoon could have shaped the subtropical East Asian precipitation
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