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Land degradation during the Bronze Age in Hexi Corridor (Gansu, China)
Abstract
Pollen and charcoal analysis, with high resolution AMS 14C dating, on two sediment sections in the Hexi Corridor track the process of settlement development and abandonment during the Bronze Age. The evidence shows that agricultural activity during the Bronze Age caused an increase in farmland and a decrease in the abundance of Artemisia grassland in the Hexi Corridor. Land degradation is probably the main cause for decreased agricultural activity and settlement abandonment. Agriculture- induced soil fertility loss and land salinization contributed to the process of land degradation. However, increasing climate aridity around 4000–3500 cal BP is probably the main initiating cause for the contraction of arable land and vegetation degradation in the Hexi Corridor.
... A comprehensive understanding of the interaction between humans and their environment is of crucial importance in providing clues not only to ancient cultural responses but also in suggesting social adaption strategies to future climate change Zhou et al., 2016). Therefore, the reconstruction of past vegetation is a significant scientific issue because it reveals how early human activities shaped landforms and the implications of these changes on paleoclimate (Carcaillet, 1998;Delcourt and Delcourt, 1987;Li et al., 2012a;Zhao et al., 2013;Zhou et al., 2012). ...
... In the southeast Hexi Corridor, the Donghuishan site (3800-3400 yr BP) is the focus of this research because of its continuous cultural deposition of c. 140 cm in depth and good recovery of fossil charcoal. Previous research also shows that its agricultural activities exerted a great impact on the local environment (Zhou et al., 2012). A total of 7 samples were floated, and 1583 pieces of charcoal containing 19 taxa were recovered (Figure 4). ...
... In addition, three zones could be identified in the Donghuishan sequence based on the number of taxa and the relative ratios of conifers, broadleaf trees, and shrubs (or herbs; Figure 6). Based on the age-depth model constructed by Zhou et al. (2012), each zone spans about one century. For the first zone, about 15 kinds of woods are identified. ...
Based on identification of fossil charcoals from 11 sites in the Hexi Corridor, we reconstruct the local vegetation community and human impact on it in the period from 4300 to 2400 cal. yr BP. More than 20 broadleaved taxa and 4 coniferous trees are present. The charcoal identifications show that vegetation in the period 4300–2400 cal. yr BP differed regionally because of variations in local topography and water supply, with limited diversity in the northwest Hexi Corridor and relatively rich diversity in the southeast area. In the northwest Hexi Corridor, the oasis woodland consisted mainly of Tamarix sp., Salix sp., and Populus sp. In the southeast region, the vegetation was a mix of coniferous forest and broadleaf woodland. By comparison with modern patterns of vegetation, broadleaf trees were much more abundant and the spruce forest extended down to relatively low altitudes, suggesting greater vegetation cover and richer diversity than today. There was also temporal variation. In the period from 4300 to 4000 cal. yr BP, woodland was relatively scarce, while the greatest diversity of plants appears in the period from 4000 to 3500 cal. yr BP, probably because of better moisture conditions at that time. After 3500 cal. yr BP, there was the appearance of woodland dominated by Morus alba, suggesting that cultivated trees may have played a key role in the lives of local people.
... Early copper smelting transformed the vegetal cover, brought soil and water pollution, and increased the rate of erosion; bringing an overall environmental degradation in Europe and the Near East (Nocete et al., 2005;Pyatt et al., 2000Pyatt et al., , 2002. These modifications can be detected by trace element analysis and paleoecological methods applied to geologic formations, such as Cu, As, and Pb analyses and examination of pollen assemblages in peat bogs, ice cores, and lake sediments (Breitenlechner et al., 2010;Monna et al., 2004;Zhou et al., 2012). However, human activities influenced their surrounding environments before and after the introduction of metal smelting technology; in relation to the changing human settlement intensity, subsistence transition and climate change during Bronze Age have not been a particular focus of investigation. ...
... Bronze wares were probably imported to the area together with wheat and barley cultivated in the Near East around 4000 BP (Brown et al., 2009;Dodson et al., 2013;Lev-Yadun et al., 2000;Linduff and Mei, 2009). Though some scholars discussed the early Bronze smelting activities on environments in Hexi Corridor, these works focused on just a few Bronze sites Li et al., 2011Li et al., , 2013Zhou et al., 2012). In this article, we analyzed Cu concentrations of anthropogenic sediment samples collected from cultural layers provided from 17 sites spanning the late Neolithic and Bronze Age periods, as well as uncontaminated natural sediments exposed in the area were analyzed for Cu. ...
... While the climatic conditions went cold and dry from 4000 to 3400 BP, human settlements remained relatively dense (Figure 5), probably because of a better adaptation of the population to the changing environment. Extensive land use and the increasing number of settlements forced the production of new tools through copper smelting (Zhou et al., 2012). As the windy conditions and cold and dry environment prevail in the Hexi Corridor during 4000-3400 cal ka BP, it is possible that copper deposition of the archaeological site was wind-brought as mine spoil and mineral processing waste. ...
The Hexi Corridor of northwestern China was a principal axis of cultural interchange between eastern and western Eurasia during the prehistoric and historic epochs. Neolithic groups began dense settlements in Hexi Corridor after 4300 BP with millet crops and polychrome pottery from north China and bronze from Central Asia around 4000 BP accompanied by wheat, barley, and sheep. The impact of these activities on the environment during the late Neolithic and Bronze Age is not clearly understood. Therefore, we analyzed the Cu concentrations of samples collected within cultural layers of anthropogenic sediments from 17 Late Neolithic and Bronze Age sites located within the Hexi Corridor. The Cu content is reported in view of the archaeological and paleoclimatic research undertaken in the area. Our results enabled us to explore the variety of human impact on the environment before and after the introduction of bronze technology into Hexi Corridor. During 4300–4000 BP, Cu concentrations of the anthropogenic sediments were constrained within natural background values. However, from 4000 to 3400 BP, they increased substantially and far exceeded the natural background. The Cu concentrations then declined and remained above the natural background from 3000 to 2400 BP. Our work suggests that the introduction of copper melting technology led to human alteration of sediments’ chemical properties in their surrounding environments in Hexi Corridor since 4000 BP; its intensity was closely related to human settlement density, which was further affected by climate change and livelihood transition in the area during Bronze period.
... The sites were associated with archaeological settings with abundant pottery, bone, microliths, charcoal and sometimes bronze and slag showing they were living places of established communities. Zhou et al. (2012) provide evidence that the early sites were abandoned when agriculture caused land degradation and loss of productivity to support farming communities. While the focus of this paper is on the wheat grains, note is made of the associated archaeological settings. ...
... These data confirm that the earliest dates for wheat in China (older than 2000 BCE) appear to be relatively widespread with the oldest ages in Gansu in the Huoshiliang and Gangangwa area. These are ancient agro-pastoral sites that were surrounded by woodland species, and were apparently abandoned when the surrounding woody fuel reserves were spent Zhou et al., 2012). There is not a great difference in the oldest ages measured either west or east of Gansu, although a single date from Xinjiang (Xintala 2006e1694 BCE) is slightly younger than the oldest from Gansu, and significantly younger than the age of wheat identified at Xishanping. ...
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.
... Previously published data have shown that wood used in the western Hexi Corridor was derived from local woodlands during the late Neolithic and early historic periods (Figure 1) and that large-scale settlements and metallurgical activities undertaken beginning ca. 2000 BCE accelerated the degradation of woody vegetation in the Hexi Corridor and led to the sparser distribution of trees (Li et al., 2011;Zhou et al., 2012;Shen et al., 2018;Liu et al., 2019b). In the late Bronze and Iron Ages of the first millennium BCE, both the number of woody taxa and the percentage of xerophytes decreased in the western Hexi Corridor (Shen et al., 2018). ...
... Based on the results of charcoal analysis in archeological sites, it is clear that the wood taxa used by people were not diverse and generally did not exceed five categories in each ancient site located in the western Hexi Corridor (Li et al., 2011;Shen et al., 2018). The relatively simple composition of woody taxa used is likely the result of the gradual emergence of a cold-anddry climate as well as increasing social complexification since the late Neolithic (Li et al., 2011;Zhou et al., 2012). However, our results suggest that the JBR jade mine site preserves a remarkably diverse range of woody taxa, considerably different from that of other archeological sites in the western Hexi Corridor (Figures 4, 5). ...
Charcoal remains from archeological sites are used not only to reconstruct the historical composition of local woodlands but also to examine the history of the human use of wood. Nevertheless, key questions such as how and why people may have selected particular woody taxa from locations long distances from their habitat have rarely been addressed. In the present study, we analyze charcoal remains from the ancient Jingbaoer (JBR) jade mine in the Mazong Mountains (Mazong Shan) of Northwest China to explore patterns in the collection and use of wood by Iron Age people. Factors affecting the choice of wood collected at the JBR site are discussed by combining the results of pollen records and charcoal analysis. Our results suggest that tamarisk (Tamarix L.), a shrub dominant in the local area, was the main source of wood for JBR miners and was used as firewood depending upon its local availability. The miners may also have used wood from species sourced further away, such as Pinus L. and Picea L., because of the local scarcity of these trees in such a dry environment. The agropastoralist subsistence system practiced by the JBR miners supports the hypothesis of the collection of wood from distant locales. This study highlights diverse patterns of wood collection in an area scarce in woody plants and provides new evidence for understanding how Iron Age people adapted to extremely arid environments.
... Wheat cultivation spread to northern China during the transition period between the Neolithic and Bronze Age, 5000-4000 years ago (Betts et al., 2014;Dodson et al., 2013;Dong et al., 2017, Lee et al., 2007Li et al., 2007). The arrival of wheat, naked barley from the West had a long-term impact on the agricultural cultivation, dietary habits and lifestyles of people in China in the following millenniums (Ma et al., 2016;Zhao, 2009;Zhou et al., 2012). At least after the Han Dynasty, wheat began to be the staple food in northern China, and China currently produces ~130 Mt of wheat per year, which is the highest yield of any single country (Atahan et al., 2014;Li et al., 2019). ...
... Climate records from the Hexi Corridor and nearby Qinghai Lake reveal an abrupt cold and dry event ca. 3500 cal yr BP (Shen et al., 2005;Zhang et al., 2000), which caused land degradation in the Hexi Corridor (Zhou et al., 2012). As shown in Figure 6, the wheat yields at the early Bronze Age sites (~4000 cal yr BP) varied widely, within the range of 0.5 to 2.0 Mg ha −1 (Figure 6). ...
The evaluation of ancient crop production and its response to climate change is key to exploring the ancient demographic and social changes. Wheat is currently the third most widely cultivated crop worldwide and was a major component across of the agricultural systems of the ancient Eurasia. In this study, the Δ ¹³ C values of 116 charred wheat grains from 28 archaeological sites, with direct AMS ¹⁴ C dating of 3952 ± 66 to 389 ± 73 cal yr BP, across northern China are reported. The result shows that the Δ ¹³ C values estimated wheat yields ranged from 0.5 to 2.5 Mg ha ⁻¹ , during the past 4000 years. The water supply and grain yield of wheat cultivation is the highest in China during the Bronze Age; however, the water supply and yield were significantly affected by climate fluctuation in the middle-late Holocene. No significant long-term trend of increasing wheat yield is observed over this interval, but a correlation between Δ ¹³ C values estimated wheat yield and cyclical climate changes can be noted.
... Neolithic and Bronze Age cultures existed already in the Hexi Corridor since 5 cal. ka BP, but their impact on water resources was probably still low (Miao et al., 2002;Zhou et al., 2012). Increasing aridity between 4.0 and 3.5 cal. ...
... Increasing aridity between 4.0 and 3.5 cal. ka BP is thought to have caused collapse of Bronze Age societies in the Hexi Corridor (Zhou et al., 2012). The desiccation of Zhuyeze Lake at the QTL02 position ca. ...
Pollen and grain-size data from the Holocene Zhuyeze Lake record in arid Central Asia were re-assessed and combined with new ostracod species assemblage data to improve inferences of the lake history and controlling climate conditions. Zhuyeze Lake was a perennial freshwater–oligohaline lake since its establishment ca. 13 cal. ka BP. The lake level fell below the position of the QTL02 section site at 2.1 cal. ka BP after the beginning of the Han Dynasty, and we assume that significantly intensified land use upstream of Zhuyeze Lake was at least partly causing the lake-level decline. Most stable lake conditions and lowest salinities were recorded in the mid Holocene between 7.5 and 5.5 cal. ka BP, providing additional evidence for the inference of the highest moisture availability in the mid Holocene in arid Central Asia. The most striking feature of analyses of grain-size and ostracod data is the inference of more or less unchanged lake levels and lake water chemistry during a period of aeolian sand accumulation in the lake between 7.8 and 7.5 cal. ka BP. Similar conspicuous and apparently contemporaneously formed sand layers were recorded in other sections in the ancient lake basin and farther upstream, and mobilization of aeolian sands must have occurred for a few hundred years in the region. Indications for the 8.2 ka event from our section and other climate records in Central and eastern Asia support the hypothesis that a short-lived cold-dry climate initiated the increased activation of aeolian sands which was later on gradually enhanced as a result of burial of previously vegetated land by dunes and sand sheets. Further work is required to determine the regional extent of sand mobilization at ca. 7.5 cal. ka BP in the northeastern Tibetan Plateau foreland and to examine the timing and controls of the self-enhancing aeolian sand mobilization, vegetation degradation and subsequent recovery.
... During the Qijia-Xichengyi cultural period, the climate was not as favorable as it was during the Machang cultural period, which triggered a reduction in the number of human settlements (Fig. 2). Subject to the impact of climate change, there was increasing desertification during this time, and agriculture was geographically confined to those river valleys in the Hexi Corridor Zhou et al., 2012;Shen et al., 2018). Furthermore, many Qijia sites were located on mountain ridges, and the high elevation of those sites may reveal that a more complex subsistence strategy was adopted during the time. ...
... After ~1500 BC, the climate became cold and dry, which caused the shrinkage of river systems and land degradation (Shen et al., 2005;Zhou et al., 2012). The agricultural culture was entirely replaced by a pastoral culture (Yang et al., 2019b), and the numbers of archaeological sites of the subsequent Shajing and Shanma Cultures are significantly smaller than that of the Siba Culture ( Figs. 1 and 2). ...
Social responses to climate change over human history have been widely discussed in academia over the last two decades. However, the transformation of the human–environment nexus crossing prehistoric and historic periods and the processes associated with it are not yet clearly understood. In this study, based on published works on radiocarbon dating, archaeobotany, zooarchaeology, and archaeological sites, together with a synthesis of historical documents and high‐resolution paleoclimatic records, we trace the extent to which human settlement patterns in the Hexi Corridor in northwestern China evolved in conjunction with climate change over the last 5,000 years. A total of 129 Neolithic, 126 Bronze Age, and 1,378 historical sites in the Hexi Corridor (n=1,633) were surveyed. Our results show that, in the Late Neolithic and Bronze Age periods (~2800–100 BC), climate change contributed to the transformation of subsistence strategies and the subsequent changes in human settlement patterns in the Hexi Corridor. The warm‐humid climate in ~2800–2000 BC promoted millet agriculture and helped the Majiayao, Banshan, and Machang Cultures to flourish. The cold‐dry climate in ~2000–100 BC resulted in the divergence and transformation of subsistence strategies in the Xichengyi–Qijia–Siba and Shajing–Shanma Cultures and in a shift in their settlement patterns. However, in the historical period (121 BC–AD 1911), human settlement patterns were primarily determined by geopolitics related to the alternating rule of regimes and frequent wars, especially in the Sui–Tang dynasties. We also find that trans‐Eurasian cultural exchange since ~2000 BC improved social resilience to climate change in the Hexi Corridor, mediating the human–environment nexus there. Our findings may provide insights into how human societies reacted to climate change in arid and semi‐arid environments over the long term.
... The adoption of pastoralism and the abandonment of agriculture, or cyclical shifts between agriculture and pastoralism that follow changing environmental conditions, may represent a resilient system, rather than a fragile system as some studies have proposed (Gansu and Peking University, 2011;Wu and Liu, 2004). Nor can we assume, without directly investigating these claims, that the turn away from agriculture indicates a less-developed society (Han, 2008;Zhou et al., 2012), or that reduced agricultural activity necessarily means reduced productivity or abundance (An et al., 2005). ...
... At Zhuyeze paleolake in the middle Hexi Corridor, desert and steppe shrubs and herbs dominated in the mid-Holocene (7.1-3.8 ka BP) and, since around 1800 BCE, the area has been a forest-steppe zone, with the dominant flora being junipers (Sabina spp.), pines (Pinus spp.), grasses (Poaceae), herbaceous plants and shrubs (Artemisia spp.), and goosefoot (Chenopodiaceae) (Chen, Cheng, Zhao, Zhu, & Madsen, 2006). Later, between c. 1800 BCE and c. 1400 BCE, the proportion of Artemisia pollen decreased and the proportion of Chenopodiaceae pollen increased in this area, which suggests a shift from grassland to desert shrubland (Zhou et al., 2012). ...
Objectives:
This study examines human adaptation to the 4000 BP climate change event, which is said to have increased the marginality of Inner Asian environments. We propose to define "marginal" environments not in relation to a specific economic activity (e.g., agriculture), but in relation to whether humans living there are physiologically stressed.
Methods:
Three sites in the Hexi Corridor of Gansu were studied, one from the early and two from the late Bronze Age (N = 125). The study includes three indicators of physiological stress: linear enamel hypoplasias (LEH); tibial periosteal lesions; and fertility. The early and late Bronze Age groups were compared to examine whether human physiological stress increased.
Results:
The percent of individuals with LEH declined dramatically, indicating fewer growth disruptions. Tibial periosteal reactions also changed, from mostly active to mostly healing at the time of death, indicating that frailty declined. Fertility, which is sensitive to changes in population health and resource availability, did not change significantly.
Conclusions:
Counter to the dominant narrative of environmental deterioration and subsistence system collapse, the Bronze Age residents of the Hexi Corridor show no skeletal evidence that they suffered from resource shortages or struggled to adapt in the fluctuating climate that pertained after the 4000 BP climate event. In fact, this study found that people suffered from less frailty and fewer growth disruptions after the unstable climate had persisted for some time. Therefore, in human biological terms, the Hexi Corridor did not become more marginal for human habitation during the Bronze Age.
... The evolution and chronology of the prehistoric cultures in Hexi Corridor have been well established (Li, 2011;Yang, 2017;Yang et al., 2019a;Li et al., 2021). In addition, a significant body of Hexi Corridor research has focused on different aspects of the past relationship between humans and the environment (Sun et al., 2010;Li et al., 2011Li et al., , 2017Zhou et al., 2012;Yang et al., 2017Yang et al., , 2020Zhang et al., 2017;Shen et al., 2018;Shi et al., 2019;Dong et al., 2021b). Furthermore, reconstruction of human subsistence has been finely reported via archaeobotanic (Zhou et al., 2016;Liu et al., 2019bLiu et al., ,c, 2021Shi et al., 2022), zooarchaeological (Flad et al., 2007;Song et al., 2016;Yang et al., 2019b), geochemical (Dodson et al., 2009), and genetic perspectives (Xiong et al., 2022). ...
Animal husbandry has been an indispensable part of human subsistence since the origin of agriculture. Along with the prehistoric cultural exchange, several kinds of major domestic animals diffused and gradually got popularized across the Eurasia. The specific geographic setting makes the Hexi Corridor in northwestern China one of the key regions to converge various types of major crops and livestock, and to witness the deep impact of novel species on local subsistence. Archeological evidence reveals an emergence of early oriental-occidental cultural communication at the opening of the local Bronze Age in Hexi Corridor, resulting in a significant shift of local subsistence. However, due to the lack of more detailed archeological evidence, the initial timing and trajectory of the transformation of livestock feeding patterns remain unclear. In this study, we reported systematic stable isotope and precise radiocarbon dating analyses on faunal remains unearthed from Huoshiliang and Ganggangwa, two Early Bronze Age settlements (ca. 4,000–3,700 BP) in middle Hexi Corridor. Our results show distinct diversification in livestock feeding patterns at ∼3,850 cal BP; in contrast with previous periods, some omnivorous livestock appear to have consumed mainly C3 foodstuff and some herbivorous livestock primarily consumed C4 plants. Combined with published stable isotope data and other archeological findings in the neighboring region, a clearer trajectory of the evolution of livestock feeding patterns has been revealed with diversified strategy amid the transformation during the Early Bronze Age in Hexi Corridor. We argued that the alteration of the local livestock feeding pattern reflects the attempt to achieve more efficient economy and sustainable society, in order to withstand the harsh arid environment in Hexi Corridor.
... In the IAR, human copper smelting activities in the Hexi Corridor caused heavy metal pollution (Cu, Ni, Pb, Zn, Cr, and As) in sediments at archaeological sites and surrounding lakes around 4000-3000 BP Zhang et al., 2017). Meanwhile, agricultural activities caused land degradation (Zhou et al., 2012) and decreased vegetation diversity . At the local scale, human activities in northern Xinjiang resulted in a reduction of the number of trees at around 3500 BP and an increase in intensity of paleo-fires . ...
It is evident that the origin, development, and expansion of agriculture and animal husbandry during the Neolithic and Bronze Age periods across Eurasia facilitated the increase of the world population and emergence of ancient civilizations, as well as altering human livelihoods, especially in East Asia. However, different areas of China have different histories in terms of the development of agriculture and of extensive human settlement during that period, and the spatial differences in human–environment interaction are not yet well understood. Here, we review up-to-date results of radiocarbon dating, archaeobotanical, and zooarchaeological analysis from Neolithic and Bronze Age sites in China, along with high-resolution paleoclimatic records, to explore the spatiotemporal variation of human settlement and its relationship to the development of agriculture and to climate change in different areas during the period 10,000–2200 BP. The results suggest that human settlement intensities in the northern East Asia Monsoon Region and south China were relatively low during 10,000–6500 BP, with a small peak during ∼8000–7500 BP, and evidently increased since ∼6500 BP, whereas farming groups began to settle intensively on the Tibetan Plateau and the inland arid region since ∼5200 BP and ∼4000 BP, respectively. The spatiotemporal variation in the intensification of human settlement in China during the Neolithic and Bronze Age periods was primarily induced by agricultural intensification and expansion across prehistoric Eurasia; climate change may have influenced the hydrothermal and vegetation conditions for crop cultivation and livestock production. The asynchronous intensive human settlements in different areas of China resulted in spatial differences in the impact of activities by human on the environments surrounding them during 10,000–2200 BP, shedding light on the evolution of the human–land relationship in China during the Neolithic and Bronze periods.
... Settled agricultural economies have traditionally dominated the climatically more moderate areas to the south, and nomadic pastoral or agro-pastoral economies have dominated the more arid steppe areas to the north (Huang and Su, 2009). The location of the boundary between these distinctly different economies appears to have been responsive to past changes in climate, whereby during moist periods when the summer monsoon was strengthened, agricultural societies expanded northwards, while during periods of drought or unstable conditions, the boundary moved southwards (Huang et al., 2002(Huang et al., , 2003Huang and Su, 2009;Zhou et al., 2012). ...
... Farmers in arid and semi-arid areas have faced the challenge of achieving sustainable irrigation for more than 2000 years. The demise of ancient civilizations due partly to crop failures caused by the accumulation of salts in agricultural soils is well known (Jacobsen and Adams, 1958;Letey, 2000;Zhou et al., 2012;Zhao et al., 2013). So too are the long-standing problems of salinity and waterlogging in key production regions of the world (Hillel, 1991;Hillel and Vlek, 2005;Rengasamy, 2006;Proust, 2008;Qadir et al., 2009;Singh, 2009). ...
Salinity and waterlogging have impacted agricultural production in arid areas for more than 2000 years. The causes of the problems are well known, as are the methods and investments required to manage salt-affected soils and shallow water tables. Yet the problems persist in many regions where farmers apply excessive irrigation water, and where farmers and irrigation departments fail to invest in adequate drainage solutions. Long ago, Professor E.W. Hilgard described the inevitability of salinity problems in arid areas and the measures required to prevent or overcome those problems. Hilgard warned of impending salinization in California's Central Valley, based partly on his understanding of salinity and waterlogging problems in India. More recently, Jan van Schilfgaarde, Jim Oster, and others also have described the inevitable environmental impacts of irrigation. These authors suggest that irrigation likely can be sustained, but the cost of reducing the environmental impacts to an acceptable level might be substantial in some areas. We review the perspectives of these authors, and others, with an outlook toward a future in which the goal of achieving sustainable irrigation coincides with the goal of intensifying agriculture more generally, to provide food and fiber for an expanding global population. We propose five activities that might be implemented in a comprehensive program to achieve successful management of salinity and waterlogging. We also introduce the notion of implementing a deposit or bond payment for the salt contained in irrigation water deliveries. Farmers would be reimbursed in accordance with their salt management and disposal practices.
... The Hexi Corridor (short name of the corridor west of the Huanghe River) is located in Gansu Province in northwest China and is composed of a series of alluvial plains that are formed by inland rivers between the Qilian Mountains (margin ranges of the Qinghai-Tibet Plateau) and Gobi Desert (Luo et al. 2014). This region has served as an important junction between the eastern and western regions of China since ancient times and plays an important role in the ancient Silk Road that links the Tianshan Corridor in central Asia with the initial section from Chang'an/Luoyang (Zhou et al. 2012). In 2013, to improve common development and prosperity, China has proposed to build the Silk Road economic belt to better connect Asian and European markets, which would reinvigorate the Silk Road and benefit all of the communities located along the Silk Road economic belt. ...
As a pivotal section of the Silk Road in northwest China, the Hexi Corridor is a popular tourist destination. In this study, the tourism climate conditions in this region were discussed using the Physiologically Equivalent Temperature (PET) and the Climate-Tourism/Transfer-information-Scheme (CTIS) from 1980 to 2012. Overall, cold or cool stress was prevalent in the area, and the optimal travel period was from May to September. With global warming, the annual numbers of cumulative days with relatively cold conditions decreased, and the annual numbers of cumulative days with comfortable and relatively hot conditions increased. Two typical stations, Wushaoling and Dunhuang, were compared and analysed for their tourism climate information according to the frequency of PET and CTIS conditions, respectively. In addition, regional variations in the tourism climate conditions based on geographic information systems (GIS) were investigated during the optimal travel period.
... So far, only the frequency of natural disasters (Lee and Zhang, 2010b, 2011 in relation to climate change has been quantitatively explored. A related line of research is about using archaeological records to trace the changes of subsistence strategy, human settlement pattern, and culture in different climatic episodes (Dong et al., 2012a(Dong et al., , 2012b(Dong et al., , 2013a(Dong et al., , 2013bJia et al., 2012Jia et al., , 2016aJia et al., , 2016bGuan et al., 2014;Jia et al., 2016cJia et al., , 2016dZhou et al., 2016) as well as the human impact on the biophysical environment (Zhou et al., 2012;Zhao et al., 2013;Ren et al., 2015). Given that some important historical events with disastrous social and demographic consequences, such as late Ming peasant rebellions (c. ...
A growing body of quantitative (large-N) studies examines the climateeman nexus in historical agrarian China. Their dominant approach is to take the whole of China as a spatial aggregate, without taking into account the role of regional context. Furthermore, quantitative investigations of the climateeman nexus in northwestern (NW) China remain scarce. This study seeks to address the above issues. We focused on the extent to which periodic fluctuation of precipitation and temperature affected positive checks (famine, epidemics, nomadic invasion, and rebellion) and subsequently population growth dynamics in Sha'anxi, Gansu, and Ningxia, NW China in AD 1500e1911. Multiple Wavelet Coherence and Partial Wavelet Coherence analyses were applied to handle the non-linear and non-stationary nature of the climateeman nexus. Our results show that drought was the common stressor of various positive checks in NW China at the multi-decadal (32e64 year) timescale. In addition, there was a coherence break of the relationship in AD 1700e1820, owing to the tremendous increase of subsistence brought about by land reclamation policy and the introduction of foreign food crops. Yet, the coherence resumed after-wards, resulting in more disastrous demographic consequences. We highlighted that the climateeman nexus is not entirely deterministic in nature, even in environmentally-fragile NW China. The relationship is mediated by social factors, particularly government policies. Still, if those measures are made at the expense of the environment, although humans might be able to win over nature in the short-term, the final outcome could be catastrophic in the long-term. This study substantiates the above notion with empirical quantitative evidence.
... In this paper, we attempt to clarify the spatial and temporal dimensions of smelting activities in the Hexi corridor, a passageway connecting eastern and western Eurasia in northwestern China. Although a number of studies have focused on the environmental signature of metallurgy in the Hexi corridor Yang et al., 2016b;Zhou et al., 2012), these works are independent of one another; here, we synthesize these existing data and supplement them with new datasets to present a comparative analysis of these archaeological sediments across northwestern China. ...
The emergence and diffusion of metallurgical technology had tremendous environmental consequence, however, the spatial-temporal consequences of the metallurgy during Bronze Age are not clear in China. In this paper, X-ray fluorescence (XRF) measurement and principal component analysis (PCA) were conducted on heavy metal element (Cu, Ni, Pb, Zn, Cr and As) concentrations (HMEC) of natural and anthropogenic sediment samples systematically collected from 22 late Neolithic-Bronze Age sites in Hexi corridor to explore the potential for subcontinental-wide changes in soil geochemistry. We place this data within the context of the Cu concentrations in lacustrine sediments located near smelting and mining centers in Bronze Age China. Our results show that variation of HMEC in anthropogenic sediment in Hexi corridor is contemporaneous with the increases of the Cu concentrations in lacustrine sediment around 4000 BP. Comparative data suggests the metallurgical production diffused from the Hexi corridor to central and southwestern China around 3600 BP. We argue that sediment pollution is not an isolated phenomenon during the Bronze Age China, but rather occurred on regional scales and is closely related to the intensity of smelting activities.
... The new waves of migrating tribes did not come from the west or south-west as before, but from Mongolia and China in the south and south-east. A striking example of opposite patterns of climate humidity in northern and southern parts of Eurasia after 2200 cal yr BC is the wet interval 2100e1300 cal yr BC (ending with the marked dry interval at 1100 cal yr BC) in Khakasia that we reconstructed from Lugovoe Mire, which coincided more to the south in China with a period of land degradation due to aridization of climate and had an overwhelming impact on the human populations (Zhou and Li, 2012). This area of China is located on the main path of the ancient Silk Road and was an important eastewest communication route between the Qilian Mts and the Mongolian Highlands. ...
... An early impact of this exchange was the introduction of coppersmelting between 4000 and 3400 BP, resulting in the chemical alteration of anthropogenic sediments in cultural contexts and lacustrine deposition . Agriculture during this time also led to land degradation, soil erosion and forest destruction in the Hexi corridor Zhou et al., 2012). In the nearby northeast Tibetan plateau, human activities during the Bronze Age might have induced the obvious increase of fire frequency (Miao et al., 2017) and the percentages of Stellera in lake sediments (Huang et al., 2017). ...
Exploring prehistoric variation in human-environmental interaction is critical for understanding the historical patterns and mechanisms of long-term human-land evolution. In this paper we review the published radiocarbon and optically stimulated luminescence (OSL) data from Late Paleolithic, Neolithic and Bronze Age sites in China, analyze the spatial-temporal distribution of these sites, and compare it with the results of recent paleoclimatic and archaeological studies. We seek to study the trajectory and influencing factors of human-environmental interactions in late prehistoric China. We detect changing patterns in the relationship between humans and the environment during different phases of the prehistoric era in China. Climate change clearly affected the environment of hunter-gatherer groups between 50,000-10,000 BP (before present, defined as 1950AD), and variation in human population in Neolithic China (*10,000-4000 BP) was likely influenced primarily by the development of agriculture, in addition to substantial climate events. The spatial scale of human settlements expanded in the Bronze Age (*4000-2200 BP) in a period of cooling climate. During this time the impact of human activities on the environment increased significantly, primarily caused by technological innovations related to the onset of prehistoric transcontinental cultural exchange in Eurasia.
... The age of the Siba culture reported by Flad et al. (2010) ranges from 3407 to 3586 cal yr BP. However, an age range of 3560 and 3830 cal yr BP was reported by Zhou et al. (2012). Both the modelled median age boundaries of the Shajing (2700-2100 cal yr BP) and Shanma (2900-2100 cal yr BP) cultures in this work are 300 years younger than previously reported dates (Figure 4). ...
The reconstruction of high-resolution chronologies for prehistoric cultures is a prerequisite for understanding the history of human evolution and its relationship with environmental change, and is valuable for exploring the trajectory of transcontinental cultural exchanges in prehistoric time. The Hexi Corridor of northwest China was one of the earliest centers for long-distance culture exchange in the prehistoric world. The timing and sequence of cultural changes in this area remains poorly understood resulting from the lack of radiometric age control. This paper presents a refined radiocarbon (¹⁴C) chronology to resolve the timing of human occupation and cultural evolution in the Hexi Corridor. Radiocarbon dating of crop remains, which have an annual life cycle, has the advantage of eliminating problems such as the carbon stored in ‘old wood’. As a result, ¹⁴C dates from crop remains are used to test the validity of the ¹⁴C dates derived from charcoal, bone and plant remains. The resultant database of ages is modelled using the Bayesian approach. The updated chronology presented in this paper shows generally good agreement with the original dates used to constrain cultural evolution in the Hexi Corridor. However, the occupation of the corridor by the Shajing and Shanma Late Bronze Age-Early Iron Age cultures appears to have taken place ~300 years later than previously thought. On the basis of comparing this updated chronology of cultural evolution with palaeoclimatic and historical records, it is proposed that the collapse of the Shajing and Shanma cultures occurred as a result of geopolitical impact rather than climate change.
... The evident improvements in social resilience with respect to the living environment facilitated continued human settlement growth in the NETP-CR during 3600-2200 BP (Fig. 3) (Bureau of National Cultural Relics, 1996, 2011, when the climate was relatively cold and dry in comparison to 15,000-3600 BP. Humans altered their living environments in the Hexi Corridor during 3600-2200 BP (Zhou et al., 2012;Yang et al., 2017;. The fir frequency and Stellera flower content of lake sediment in the NETP increased substantially during this period (Fig. 3c) (Huang et al., 2017). ...
The relationship between the evolution of human societies and their living environments has been discussed intensively in recent decades. It is important to understand the patterns and mechanisms of human-environment interaction and evolution in order to cope with rapidly changing environments in the modern world. We reviewed the results of dating, archaeobotanical, and zooarchaeological studies from 139 prehistoric sites in the Northeast Tibetan Plateau (NETP) and contiguous regions (NETP-CR: i.e., the Hexi Corridor and western margin of the Chinese Loess Plateau) and compared them with paleoenvironmental records to study variations in spatiotem-poral patterns of social development in the area and their relationships with climate and vegetation changes. Our results show that hunter-gatherer groups occupied vast areas of the NETP at low intensities during~15,000-5500 BP (years before present). This was directly related to forest cover and climate change. An increase in temperature and precipitation turnover of vegetation from desert steppe to alpine meadow/subalpine shrub, and recovery of animal population on the Tibetan Plateau created more food resources and space for hunter-gatherers. Millet farmers settled extensively below 2500 m a.s.l. (meters above sea level) in the NETP-CR between~5500 and 3600 BP, and might have coexisted with hunting groups above 2500 m a.s.l. via subsistence exchange. The distribution of human settlements during that period was affected by climate change, with the relatively warm and wet climate promoting the expansion of millet agriculture to the NETP-CR during 5500-4500 BP, while climate deterioration caused humans to retreat to lower altitudes. During 3600-2200 BP, a range of livelihoods emerged in different regions of the NETP-CR. This was promoted by early trans-Eurasian exchange and the development of an agro-pastoral economy that utilized cold-tolerant crops and livestock. This eventually promoted the expansion of permanent human settlements to high-altitude areas in the NETP. This study found that human societies adopted various strategies to adapt to the changing living environment throughout late prehistoric times in the NETP-CR. The results provide a long-term perspective on the trajectory of regional socio-environmental co-evolution.
... ple, even the Cambisols owe their diffusion to the loss of the surface horizon richer in organic matter, which characterized the original Phaeozems, Kastanozems and Chernozems present in the same environments. The increase in Cambisols to the detriment of the three soil typologies showing a surface horizon richer in humus and more fertile was due to the erosion that occurred during the centuries of agricultural exploitation, dating back to the Ancient Bronze Age(Costantini et al., 2012;Costantini & L'Abate, 2009;van Andel et al., 2013;Willis et al., 1998;Zhou et al., 2012). ...
Maintaining or recovering soil health is becoming a goal of many policies carried out at national, continental and global scales to promote global health. This viewpoint is aimed at stressing the relevance of a holistic approach to soil health assessment and monitoring, which is not only related to soil functional biodiversity but also considers the genetic horizons of the soil profile and not just the topsoil. We highlight that soil health has different connotations depending on the environmental setting and may show high spatial and temporal dynamics. Although the biological activity is often concentrated in the surficial horizon, we report increasing evidence that deep soil horizons host relevant biological communities, which are regulated by soil conditions that are usually different from those present in the topsoil. The processes responsible for the formation of surface and subsurface soil genetic horizons produce soil features that select the presence of organisms. The natural self‐organization of soil features is at the basis of the soil classification systems and of their ability to differentiate soil taxa and appreciate pedodiversity. Examples are reported of surface and deep soil genetic horizons as an important interpretative tool of soil functional biodiversity and soil health. Therefore, the assessing and monitoring of soil health should not be carried out at fixed depth, but according to soil genetic horizons. We conclude that the loss of the natural self‐organization of genetic horizons is a form of soil health degradation.
The purpose of this report is to clarify land use changes and driving factors in Gansu Province, which is located in an inland area of modern China. The study is based primarily on field observations. Gansu Province has lagged behind the coastal area of China in economic development due to numerous constraints, such as severe natural conditions and a remote location. Moreover, the scarce water resources of the province are being utilized near capacity, with the amount of water consumed at 50–60% of the total water resources available in the province. However, economic development is now progressing more rapidly from urbanization, industrialization, and new economic activities such as renewable energy production. This rapid development, driven by the National Western Development policy, is affecting land use in the region. Cropping patterns have become more diversified, and croplands are advancing into the limited area of arable land. Higher productivity land use expanded following cultivation of fruit trees in the Loess Plateau. Thus, the province has a varied land use for economic gain based on local conditions.
The development and subsistence strategies adopted in ancient settlements are crucial to the understanding of long-term human–environmental interaction in the past. Here, we reassess the chronology of the ancient walled settlement of Sanjiao in the Hexi Corridor in northwestern China through accelerator mass spectrometry radiocarbon (AMS ¹⁴ C) dating and explore the subsistence of the settlers inside through the identification of carbonized seeds and charcoal. In addition, high-resolution paleoclimate records in the Hexi Corridor and nearby regions are employed to explore the reason for the construction of Sanjiao. Our results show that Sanjiao was built around 828 cal BC and remained inhabited through 384–116 cal BC. This indicates Sanjiao is the earliest known walled settlement in the Hexi Corridor. Ancient people at Sanjiao consumed crops such as barley, broomcorn millet, and foxtail millet, and used wood from Tamarix chinensis , Tamarix , Salix , Picea , Hippophae , Betulacea e, and Poaceae as fuel. The construction date of Sanjiao correlates with climate deterioration and social upheavals in the Hexi Corridor, potentially suggesting a defensive purpose for the site.
史前文化高分辨率年代的重建是理解人类演化及其与环境变化关系的前提, 对探索史前跨大陆文化交流的轨迹具有重要意义. 河西走廊是史前世界最早的远距离文化交流中心之一. 由于缺乏14C年代的控制, 该地区史前文化的年代及序列仍不清楚. 本文提供了一个更加精确的14C年代序列以解决河西走廊地区人类定居和文化演化的时间问题. 一年生的炭化农作物遗存14C测年具有避免“老木效应”的优点, 因此被用来检测河西走廊已有的炭屑和骨骼14C年代的可靠性. 在此基础上所得的14C数据集用贝叶斯方法进行建模, 模型年代显示其与河西走廊已有的考古文化年代基本一致. 然而, 青铜时代晚期-铁器时代早期的沙井文化和骟马文化的年代比已有的年代晚约300年. 通过对比模型年代与古气候和历史文献资料, 我们认为沙井和骟马文化的衰落是受地缘格局的影响而不是气候变化导致的.
Understanding past human-environment interactions over a long time-scale offers an analogue to predict, adapt and mitigate the environmental issues caused by global change and human activities in the future. The transient existence of historical cities from arid northern China can provide a valuable reference for this issue. In this study, we investigated a set of sand dunes which accumulated alongside the city wall of South Heishuiguo ancient city (SHC) from the middle Hexi Corridor in arid northern China. Dating these dune sands can provide the timing of both desertification and city abandonment. A series of sand samples (a total of 20) were collected, and their ages were determined by luminescence dating of K-feldspar fraction. The results suggest an abrupt sand dune accumulation between 0.40 ± 0.03 ka and 0.25 ± 0.02 ka, corresponding to 1590–1790 CE. This study confirms a phase of desertification between the late 16th century and the late 18th century in the Hexi Corridor, and the abandonment of the SHC at the ~17th century. In order to assess the anthropogenic influences on desertification, we also reconstructed the population history of the Hexi Corridor over the last 2000 years based on historical literature as a quantitative index of human activity intensity. By comparison of the timing of onset of desertification around the SHC with robust paleoclimate and historical population reconstructions, we conclude that (1) the desertification of 1590–1790 CE was likely the result of considerably enhanced human activities between the late Ming and the early Qing Dynasties, as this period was dominated by a relatively moist climate and could restrain the sand deflation; and (2) the desertification in turn caused abandonment of SHC as the impact of environmental changes on people.
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.
Global climate change and its possible ecological consequences have become the focused issue (IPCC, 2007; Mann et al., 2008; Ding et al., 2009). The Holocene contains the analogous characteristic of future climatic change and the continuous agriculture activity, providing the ideal “similar pattern” for studying the climate change and human adaption and impact in the future. Based on the recent studies of stalagmite, ice core, ocean, and lake etc., the paper introduces the new progress in the Holocene climate and agriculture research in China as follows: (1) Discuss the variability, amplitude, and unstable characteristic of climate, as well as the abrupt events and mechanisms of climate. (2) Analyze the botanical index records for studying the early agriculture. (3) Review the agricultural origin, expanding, and development. (4) Reveal the style and intensity of early agriculture and understand the agricultural impact and adaption to the environmental changes. (5) Introduce ongoing research projects in China and emphasize the significance of increasing the dating precision and the indicative effectiveness of proxies. (6) Realize how the ecosystem and environmental factors respond to the increasing temperature process, understand how the human adapt to the rapid climate change, and provide the scientific basis for assessing the effects of climate change and the human adaption in the future.
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.
It has long been known that leaded bronze, an alloy consisting primarily of copper with the addition of tin and lead, was widely used in early China, starting from around the second millennium BC. The additional lead distinguishes this metal from common bronze, the copper-tin binary alloy, used by most other Early Metal Age civilisations in Eurasia. The reasons behind the use of leaded bronze have not been fully examined in previous literature.
In this thesis, the discussion of metallurgical technologies and the studies on material properties are combined with four case studies of early metal-using communities to reinvestigate the use of leaded bronze in early China. With this approach, the thesis challenges the wide held notion that lead was consciously added by the craftspeople, mainly to facilitate the casting. Instead, I argue that the widespread of leaded bronze objects was mainly due to both the socio-economic concerns in making bronze ritual vessels in Central China and the recycling and reuse of the metals by other communities around Central China. Moreover, the seemingly common use of leaded bronze does not reflect a uniform acceptance of a single set of knowledge and know-how. Rather, people in different communities responded differently to this new material and chose to engage it in different ways.
This study on leaded bronze provides us with a new perspective to recognise the complexity and diversity of technology and material culture in early Chinese communities. Meanwhile, through the active discussion on the theoretical frameworks and research methods for archaeometallurgy and material culture studies, I also suggest approaches which may be useful in future studies of early metallurgy and other craft production.
The reconstruction of fruit collection and cultivation based on plant remains plays an important role in understanding the subsistence strategies of ancient societies. Here, we report the identification of fossil charcoal from eight sites in the Hexi Corridor to give a clue to the early exploitation of fruit resources in the period 2300–400 bc. Charcoal assemblages show that millet farmers may have collected some tree fruits including bird cherry (Padus sp.), pear (Pyrus sp.) and whitebeam (Sorbus sp.) in the period 2300–2000 bc. From 2000 to 1500 bc there was continuing utilization of Padus sp., Sorbus sp. and cotoneaster (Cotoneaster sp.), at a time when cereal agriculture of wheat and barley had been introduced from outside. Based on analysis of ecological distribution, reproductive biology and the history of utilization, we infer that these fruits were gathered from the wild rather than cultivated. Later, the cultivation of non-native mulberry (Morus alba) began around 1500 bc in the context of an established high-yield wheat agriculture, probably indicating the earliest sign of horticulture in the Hexi Corridor. As with the beginning of agriculture, the horticulture is associated with cultivation of non-native species. In short, the variations in the presence of charred wood of fruit trees indicate that people might have collected wild fruits over a period of time, and that horticulture occurred much later than the spread of a variety of cereal and other crops in the Hexi Corridor.
A high-resolution pollen record, c. 50 yr/sample, from terminal lake sediments in the Shiyang River drainage basin on the present margin of the summer monsoon was used to reconstruct vegetation and climate history during the Holocene. Forest trees from mountainous areas of the drainage, including Sabina, Picea and Pinus, dominated pollen assemblages in the early Holocene (11.6 Á7.1 cal. ka). In the mid-Holocene (7.1 Á3.8 cal. ka) desert and steppe shrubs and herbs around the lake, including Nitraria, Poaceae, Compositae and Artemisia, were dominant. The late Holocene (3.8 Á0 cal. ka) was again dominated by alternation of Pinus ÁSabina tree pollen and desert-steppe pollen. The early Holocene forest expansion in the mountains and subsequent increase in the river transport of tree pollen corresponds with maximum precipitation during the East Asian summer monsoon maximum. The timing of these changes in our record from arid China is different from that of East China, where the Holocene monsoon maximum appeared in the middle Holocene. This difference indicates that the extent and development of summer monsoon circulation in the Holocene was complex. Changes in the pollen record appear to show pervasive and persistent centennial-to millennial-scale oscillations throughout both wet and dry periods of the Holocene. Our results imply the continental interior was sensitive to changing moisture conditions and responsive to Holocene climatic events.
A comprehensive record of lake level changes in the Dead Sea has been reconstructed using multiple, well dated sediment cores recovered from the Dead Sea shore. Interpreting the lake level changes as monitors of precipitation in the Dead Sea drainage area and the regional eastern Mediterranean palaeoclimate, we document the presence of two major wet phases (∼ 10–8.6 and ∼ 5.6–3.5 cal kyr BP) and multiple abrupt arid events during the Holocene. The arid events in the Holocene Dead Sea appear to coincide with major breaks in the Near East cultural evolution (at ∼ 8.6, 8.2, 4.2, 3.5 cal kyr BP). Wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions, suggesting a parallelism between climate and Near East cultural development.
A severe drought in parts of low-latitude northeastern Africa and southwestern Asia ∼4200 yr ago caused major disruption to ancient civilizations. Stable isotope, trace element, and organic fluorescence data from a calcite flowstone collected from the well-watered Alpi Apuane karst of central-western Italy indicate that the climatic event responsible for this drought was also recorded in mid-latitude Europe. Although the timing of this event coincides with an episode of increased ice-rafted debris to the subpolar North Atlantic, the regional ocean-atmosphere response seems atypical of similar Holocene ice-rafting events. Furthermore, comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longerterm climate anomaly.
The archaeological and historical record shows many instances of societal collapse. These events have traditionally been explained by a combination of social, political, and economic factors. In their Perspective, [Weiss and Bradley][1] argue that there is increasing evidence for climate as the primary agent in the collapse of prehistoric and early historic societies. They also consider the possible effects of future anthropogenic climate change.
[1]: http://www.sciencemag.org/cgi/content/full/291/5504/609
Although human-induced changes to the global environment and natural biotic resources, collectively labeled "global change" and the "biodiversity crisis," have accelerated with industrialization over the past 300 years, such changes have a much longer history. Particularly since the rise of agriculturally based societies and associated population expansion during the early Holocene, humans have had cumulative and often irreversible impacts on natural landscapes and biotic resources worldwide. Archaeologists, often working closely with natural scientists in interdisciplinary projects, have accumulated a large body of empirical evidence documenting such changes as deforestation, spread of savannahs, increased rates of erosion, permanent rearrangements of landscapes for agriculture, resource depression and depletion (and in many cases, extinction) in prehistory. In some areas and time periods, environmental change led to long-term negative consequences for regional human populations, whereas in other cases, changes favored intensification of production and increased population sizes. Drawing upon case studies from North America, Mesoamerica, the Mediterranean, Near East, India, Australia, and the Pacific Islands, the diversity of types of prehistoric human-induced environmental change is assessed, along with the kinds of empirical evidence that support these interpretations. These findings have important implications both for the understanding of long-term human socioeconomic and political changes and for ecologists who need to assess current environmental dynamics in the context of longer-term environmental history.
The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and other carbonates and for quantification of uncertainty in both the 14C and calendar timescales as established in 2002. No change was made to the curves from 0–12 cal kBP. The curves were constructed using a Markov chain Monte Carlo (MCMC) implementation of the random walk model used for IntCal04 and Marine04. The new curves were ratified at the 20th International Radiocarbon Conference in June 2009 and are available in the Supplemental Material at www.radiocarbon.org.
Progressive changes in soil salinity and sedimentation contributed to the breakup of past civilizations.
The paper investigates the historical agricultural exploitation in Northwest China, and its social benefits in the context of historical documents and their relationship with temperature and humidity backgrounds. Results show that during the Western Han Dynasty (206 BCJ25 AD) and the early stage of Tang Dynasty (ca.7th century) climate was suitable for agriculture, leading to the success of large-scale wasteland reclamation in Gansu Province (called Hexi area in history), however during the late stage of the Tang Dynasty (ca. 8thJ9th century) and the middle of the Ming Dynasty (ca.16th century), the climate there went into a cold stage, leading to the decline of stationing troops who opened up wasteland in the region; the prosperity of the Tarim Basin at the beginning of the Christian Era and its subsequent decline were linked to changes in water resources; and historically, the reclamation and later desertion were responsible for accelerating land desertification, and its typical examples are the formation of the Wulanbuhe Desert and the frequent occurrence of severe sand storm events in the warmer 13th century as the bad aftermath of the desertification.
Long-term climate cycles related to gradual shifts in solar insolation, as well as shorter-term shifts in volatility and equability, are important components of cultural evolution. However, major rapid climate change episodes related to Dansgaard-Oeschger cycles and Heinrich Events apparently had the most dramatic impact on cultural change in arid China during the Late Quaternary. We propose three models relating environmental change with human adaptive shifts in the region: (1) a shift to broad-spectrum foraging may be related to a reduction in high-ranked resources during the Last Glacial Maximum (LGM); (2) millet domestication probably began in the northern margin of wild millet distribution as it began to contract during the Pleistocene/Holocene transition; and (3) desertification may have been accelerated and enhanced during the Late Holocene in some areas of arid China by the development of camel-based pastoralism. We propose a number of possible tests of these models.
During the first century B.C. the Chinese built cities along the Hexi Corridor to protect the ancient Silk Road from raids by Huns. A Hun ruler reciprocated by founding his own city and later Chinese dynasties repeated the process. Urban populations were fed by cultivating oases and by harnessing melt-water streams to irrigate and reclaim areas of grassland. Where tree feeling and cultivation broke surface layers of alluvium and clay, water and wind began to erode and expose underlying beds of sand. Blowing sand encroaching upon the cultivated area and eventually drifted across the ruins of former cities. Sites of cities that once housed tens of thousands of people are now being explored scientifically. Research into the recurrent history of desertification throws light on present-day problems faced by one-sixth of the world's population living in arid regions and by one-third of the earth's land surface covered by deserts. By learning from past events we may be able to halt future advances by deserts.
This paper reviews recently published literature, most of which was published in Chinese, and searches for regional patterns of Holocene changes useful in depicting global patterns. The Holocene in the Xinjiang region can be divided into three stages: a warming and dry early stage (from 11 10 to 8-7 ka BP), a warm and wet middle stage (from 8-7 to 4.5-3 ka BP) and a fluctuating cool and dry late stage (since 4.5-3 ka BP). The Holocene in the northern Tibetan Plateau can also be divided into three stages: a warming and wet stage (from 10.5-10 to 5-4 ka BP), followed by a variable drying and probably warm stage (5-4 to 3 ka BP) and ending with a cool and dry stage (since 3 ka BP). In the Inner Mongolian Plateau, the early Holocene (from 10.5-9.5 to 8-7.5 ka BP) was warming and dry, and a warm and wet climate occurred from 7.5 to 3.5, during which the best time was 6.3-3.8 ka BP; the climate has been variably drying and probably cooling since 3.5 ka BP. In the northwestern part of the Loess Plateau, several Holocene palaeosols have been identified (10-9, 7.5-5, 4-3 and 2.7-2 ka BP) with the 7.5-5 ka BP palaeosol being most strongly expressed. The best-developed palaeosol-equivalent in major valleys is a swamp-wetland facies deposited between 8885 and 3805 14C yr BP under an extremely wet regime. The climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp-wetland facies-depositional period. Our summary shows that the Holocene Climatic Optimum occurred nearly contemporaneously (8-5 ka BP) at all sites in the Xinjiang region, in the Inner Mongolian Plateau and in the northwestern part of the Loess Plateau. A warming and wet early Holocene (10-8 ka BP) in the northern Tibetan Plateau is most likely related to high effective soil moisture resulting from snow and ice melting. We propose here that the middle Holocene Climatic Optimum (8-5 ka BP) in arid to semi-arid China was primarily a delayed response of the low latitude oceans to high latitude peak insolation (9-8 ka BP).
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.
The history of climatic changes during the interval 8500–3000cal. yr B.P. has been reconstructed from stratigraphical and chronological studies and the results of Total Organic Carbon (TOC), Total Inorganic Carbon (TIC), element composition, pollen, and stable isotope analyses of a section along the Hongshui River, in the southern Tengger Desert, NW China. The record suggests that from 8450 (bottom of the studied section) to 7500yr B.P., the climate was characterized by instability. From 7500 to 5070yr B.P., the climatic conditions improved and can be divided into two parts: a warm–humid spell between 7290 and 6380yr B.P., during which the average temperature was 3–4°C higher than that of today, and a warm–dry spell lasting from 5950 to 5720yr B.P. The climate deteriorated between 6380 and 5950yr B.P. From 5720 to 5070yr B.P., the temperature decreased, but humidity increased. An abrupt temperature drop occurred between 5340 and 5290yr B.P. that indicated the decline of the warmer and humid Mid-Holocene climate. From 5070yr B.P. onward, the climate oscillated significantly and there were three large temperature decreases coinciding with high mountain glacier advances between 5070–4670yr B.P., 4300–3740yr B.P. and 3410–3230yr B.P. (top of the section), respectively. The climatic fluctuations recorded in the southern Tengger Desert appear in-phase with climatic changes recognized in the Tibetan Plateau, suggesting that the period between 7290 and 6380yr B.P. was the most warm–humid spell. One extremely dry event occurred at ca. 3000yr B.P., and subsequently the fluvial–lacustrine depositional process terminated and wind action prevailed in the area; both of these features can be attributed to the rapid strengthening and weakening of the summer monsoon circulation, which are closely connected with global changes.
The earliest direct dates of wheat in East Asia come from Donghuishan in Gansu Province, China. Few other dates of wheat in East Asia are direct dates. The previous direct dates at Donghuishan were obtained from wheat without secure context. New samples were taken from a stratigraphic profile at Donghuishan and directly dated. The wheat remains are earlier than any other directly dated wheat east of the Xinjiang Autonomous Region, but considerably later than the previously dated specimen from the same site. These new dates, from the early second millennium BC, are the earliest evidence of significant wheat and barley production and show that the Hexi Corridor played a critical role in the introduction of wheat to China.
New data suggest that dramatic environmental change in the Western Loess Plateau of China corresponded with substantial changes in human demography ca. 4000 cal yr B.P. These data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr B.P. The sudden reduction in the number of archaeological sites during this period, namely a reduction in the total number of sites and a contraction of the areal distribution of sites, points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr B.P.
Dietary patterns at two Bronze Age sites in the Hexi Corridor are investigated by the analysis of stable carbon and nitrogen isotopes in faunal bone collagen. The findings are compared with archaeobotanical remains from one of the sites which include high proportions of millet (Panicum miliaceum and Setaria italica) as well as the western derived cereals wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa). The isotopic data indicate domestic omnivores (Canis and Sus) had diets dominated by millet. Minimally offset δ15N values between herbivore and omnivore fauna suggest low consumption of animal protein by omnivores. Diets of herded animal (Bos and Caprinae) included only low proportions of C4 foods, suggesting that these animals were not regularly foddered with millet plants, and that their grazing areas were mostly beyond the agricultural zone. The wide range in δ15N values amongst herbivore fauna (4.1‰–11.8‰) suggests grazing occurred in a variety of ecological zones, and this would be consistent with the occurrence of long-distance transport of livestock in the region.Highlights► Subsistence was based on millet in the Bronze Age Hexi Corridor. ► Herded animals were mostly grazed beyond the agricultural zone. ► Ecologically distinct grazing areas suggest long-distance transport of livestock.
Age–depth models form the backbone of most palaeoenvironmental studies. However, procedures for constructing chronologies vary between studies, they are usually not explained sufficiently, and some are inadequate for handling calibrated radiocarbon dates. An alternative method based on importance sampling through calibrated dates is proposed. Dedicated R code is presented which works with calibrated radiocarbon as well as other dates, and provides a simple, systematic, transparent, documented and customizable alternative. The code automatically produces age–depth models, enabling exploration of the impacts of different assumptions (e.g., model type, hiatuses, age offsets, outliers, and extrapolation).
AimTo explore the relationship between modern pollen precipitation and vegetation patterns in an arid region of the Middle East.LocationData come from the central Jordan Rift from 1700 m elevation in the highlands to 300 m below sea level in the Dead Sea basin.Methods
Modern pollen samples and descriptive vegetation data were collected from twenty-one locations at 100 m elevational intervals from the highest elevations on the eastern side of the rift valley, where woodlands grow, to the lowest elevation desert on earth, characterized by drought and salt tolerant plants. Pollen percentage data from each vegetation zone are compared descriptively and numerically using cluster and Principal Components Analyses (PCA).ResultsThree major vegetation zones: woodland, shrub steppe, and desert scrub, are identified by their dominant plant species. The widely spaced tree, Quercus calliprinos Webb, defines the Quercus L. woodland that grows above 1500 m elevation. The shrub steppe can be divided into two subzones found between about 1500 and 900 m elevation: Artemisia herba-alba Asso shrub steppe and Artemisia L. shrub steppe with Juniperus phoenica L. Desert scrub dominates the lower elevation landscape with Hammada salicornia (Moq.) Iljin the dominant shrub between 900 and 200 m and Haloxylon persicum Bge. found below 200 m elevation.Pollen spectra reflect the elevational vegetation zones. In particular, Quercus L., Juniperus L. and Tamarix L. pollen are abundant where the trees grow. Highly variable amounts of non-arboreal pollen taxa – primarily Artemisia L. and Chenopodiaceae Vent. – differentiate shrub steppe from desert scrub vegetation. Cluster and PCA of pollen data support the qualitative vegetation zonation.Main conclusionsThe main vegetation zones along the Jordan Rift from 1700 to –300 m elevation can be distinguished by their modern pollen precipitation. Open vegetation types, in particular, can be recognized by their pollen spectra. High amounts of Artemisia L. pollen distinguish the moister upper elevations where Artemisia L. steppe grows. In contrast, greater amounts of Chenopodiaceae Vent. pollen characterize the drier, lower elevation deserts.
The concept of an arid pleniglacial in the Middle East depends primarily on the interpretation of pollen diagrams including those of Lake Zeribar in the Zagros Mountains of western Iran. It has been assumed that Lake Zeribar was surrounded by a Chenopodiaceae-Artemisia steppe and that the climate was therefore dry. Both assumptions are questioned. The environment of Pleistocene Lake Zeribar may have been similar to the tragacanthic or alpine zone of the modern Zagros Mountains. The dominance by pollen of Chenopodiaceae and Artemisia is explained by low pollen production of high-altitude vegetation, preferential incorporation of pollen of late-blooming plants into the sediments, and high production and long-distance transport of lowland pollen. In any case, high percentages of Chenopodiaceae and Artemisia pollen do not necessarily indicate low annual precipitation but a highly seasonal climate with cold winters and hot, dry summers. Such a climatic regime was in effect continuous except for a period beginning about 10600 B. P. during which summer rainfall or reduced summer drought occurred. This change in seasonality resulted in the dominance of Poaceae pollen and the initial increase in arboreal pollen. A moisture curve based on the ratio between Chenopodiaceae and Artemisia pollen indicates a pleniglacial climate with wet winters and a late-glacial and early-Holocene climate with periods of intense aridity. The climatic history presented here is compatible with non-palynological evidence of regional late Pleistocene climates and with seasonality changes suggested by climatic modelling based on orbital parameters.
205 surface pollen samples from different communities in Northern China were analyzed to understand the quantitative relationship
between pollen and its original vegetation. Pollen analysis and vegetation investigation show that the pollen assemblages
differ a lot in different vegetation regions. Arboreal pollen account for more than 30% in temperate broad-deciduous forests
region. In temperate steppe regions, herb pollen percentages are more than 90%, where Artemisia and Chenopodiaceae are dominant pollen types with Artemisia percentages more than 30%. In temperate desert, Chenopodiaceae pollen percentages are more than Artemisia, where ferns are rare. Cyperaceae pollen percentages are more than 20% in sub-alpine or cold meadows. The relations between
pollen percentages and vegetation cover indicate that most arboreal pollen shows a close relationship with parent plant covers,
most shrubby pollen types have more or less correlations, but most herbs do not show clear correlations. For arboreal pollen
types, Picea pollen shows the closest correlation with spruce trees coverage, then is Quercus and Carpinus. Betula, Larix and Juglans have also high correlation coefficients with their plants coverage, but Betula pollen is of overrepresented pollen type and more than 40% in birch forest, while Larix and Juglans pollen is underrepresented and pollen percentages are more than 10% in Larix or Juglans pure forests. Pinus is of overrepresented pollen type, and pollen percentages have some relations with plants cover. Pine forest might present
when Pinus pollen percentages are more than 30%. The relations between Ulmus and Populus pollen percentages and vegetation cover are not close, where they are mixed with other arbors, they cannot be recorded easily,
but if their pollen percentages are more than 1%, Ulmus or Populus trees should exist. For shrubby pollen types, the correlation between Vitex pollen percentages and vegetation cover is the highest, then is Corylus, Tamariaceae and Nitraria, and their pollen percentages are less than 1% where original plant are absent. Caragana and Spiraea pollen percentages have some relations with vegetation cover. The relations between pollen percentages and vegetation cover
are not clear for Rosaceae and Saxifragaceae. For herb pollen types, Cyperaceae pollen has the closest correlation with vegetation
cover, where pollen percentages are more than 20% when Cyperaceae are constructive or dominant species in vegetation, and
pollen percentages are less than 5% where Cyperaceae are not constructive or dominant species (cover less than 30%). Artemisia and Chenopodiaceae pollen percentages mainly have close relations with ecological regions. The relations between pollen percentages
and cover are not clear for Gramineae, Leguminosae and Compositae.
Based on multi-proxy analysis of pollen, carbonate, TOC, TN and δ 13C of organic matters, a high-resolution climatic evolution of Qinghai Lake since the Late Glacial Age is reconstructed. The
results indicate that the boundary between the Last Glacial Maximum and the Late Glacial Age is at about 18.2 cal.ka BP. The
warm and wet period, which began at about 15.4 cal.ka BP, culminated at 7.4 cal.ka BP and came to its end at about 4.5 cal.ka
BP. After that, the climate gradually became cold and dry. The multi-proxy analysis indicates that the climate fluctuated
greatly during the transitional period from the Late glacial Age to the Holocene, and this is in good accordance with that
reflected by deep sea cores of North Atlantic, ice cores of Greenland, lake sediments in Europe, loess sequences and Guliya
ice core in China. The climatic evolutional characteristic of the Qinghai Lake since the Late Glacial Age shows that the driving
force of the East-Asia Monsoon correlates with solar radiation on the ten-thousand-year scale.
The polarization signature of a given pixel in a radar image represents scattering mechanisms from various scattering elements. This paper presents an analysis of maximum and minimum polarizations of five kinds of polarization signatures: co-polarized, cross-polarized, completely polarized, completely unpolarized, and total available power signatures. We propose a new algorithm of target classification based on these maximum and minimum polarizations, then, conduct the experiment on the measured polarimetric SAR data. Experimental results show that this algorithm is robust to pixel-by-pixel target classification in radar images
We present lithology and fossil pollen data from a 384 cm sediment section from Qingtu paleolake in arid northwest China and discuss their environmental interpretations. The chronology was controlled by four accelerator mass spectrometry (AMS) radiocarbon dates on peat and bulk lake sediments. Lithology changes suggest a general sequence of local environment shifts from a non-lake environment before 7200 cal yr BP, through a shallow lake during 7200–3500 cal yr BP and a marsh during 3500–3000 cal yr BP, to a sandy desert after 3000 cal yr BP. Fossil pollen assemblages suggest a steppe desert during 7200–5200 cal yr BP, a period of rapid switches between upland and lowland pollen types from 5200 to 3000 cal yr BP, and a desert since 3000 cal yr BP. Both lithology and pollen data indicate that in a generally arid context, climate was extremely dry in the early Holocene, relatively wet at 7200–5200 cal yr BP, highly variable during 5200–3000 cal yr BP, and dry again after 3000 cal yr BP. The climate change around Qingtu Lake was likely controlled by the interplay of the East Asian summer monsoon, the mid-latitude westerlies and local topography around the Tibetan Plateau.
Pollen data from 30 sites in arid and semi-arid regions of China were reviewed to document regional patterns of Holocene vegetation and climate change and to understand the large-scale controls on these changes. Vegetation at most sites in eastern Inner Mongolia switched between forest, forest steppe, and typical steppe, showing maximum moisture conditions before 6 ka (1 ka=1000 cal yr BP) and a dry climate after ∼6 ka. Vegetation in the northwestern Loess Plateau changed between desert steppe, forest steppe and steppe, suggesting wet–dry oscillations, from an initial dry to wet climate at ∼9–4 ka and then back to a dry climate. In the northern Tibetan Plateau, vegetation was characterized by steppe desert, steppe or desert, indicating a wet climate in the early and mid-Holocene until 6–4.5 ka. In western Inner Mongolia and Xinjiang, pollen assemblages show changes between desert, steppe desert and steppe, with a wet period occurring during 8.5–5.5 ka at most sites. All the four regions show a drying trend during the late Holocene. The complex climate patterns suggest that regional climate responses to large-scale climate forcing were controlled by interactions of competing factors, including the monsoons, westerlies and topography-induced regional atmospheric dynamics. The role of human activity in vegetation change requires further investigation.
Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene–Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23–18 ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean–atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth's climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17–16 ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15–14.5 ka BP and 11.5–11 ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4–8 ka and 4.2–4 ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally.
The temporal relationship between rapid climate shifts in the Northern and Southern Hemispheres at the end of the last glacial is crucial to understanding how the global climate system functions during periods of major transition. A detailed Southern Hemisphere mid-latitude pollen record from a climatically sensitive and well-dated upland site in New Zealand, unlike previous interpretations, shows clear evidence of late-glacial climate changes similar in structure to those in the Northern Hemisphere, including a cooling interval from ca. 11 600 to 10 700 14C yr B.P. Because the cooling interval occurred ca. 600 14C yr before the Younger Dryas chron, our record thus also suggests that some global climatic events during the last deglaciation may have registered earlier in the Southern Hemisphere The full paper was published in The Geological Society of Americas journal Geology
VariationinlateQuaternarycentralAsianclimatesand the nature of human response
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Early copper-based metallurgy in China: old question, new perspec-tive
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INTCAL09 and Marine 09 radiocarbon age calibration curves, 0-50,000 years cal BP A high-resolution climatic change since the Late Glacial Age inferred from multi-proxy of sediments in Qinghai Lake
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Excavation report of Huangniangniangtai site in Wuwei Acta Archaeologlica Sinica 2, 53e71. in Chinese The Archaeology of Donghuishan in Minle e Research and Interpretation of the Siba Culture Cemetery
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Point count estimation of charcoal in pollen preparations and thin sections of sediments. Pollen Spores 24 Climate change and the collapse of the Akka-dian empire Modern pollen precipitation from an elevation transect in central Jordan and its relationship to vegetation
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Subsistence and the isotopic signature of herding in the Bronze Age Hexi Corridor, NW Gansu Methods and code for 'classical' age-modelling of radiocarbon sequences Holocene environmental change inferred from a high-resolution pollen record
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Managing salinity: lessons from the past
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Late Holocene drought responsible for the collapse of Old World civilizations is recorded in an Italian cave flowstone The late Pleistocene climates of the Lake Zeribar region (Kurdistan, western Iran) deduced from the ecology and pollen production of nonarboreal vegetation
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