Search

The northern edge of the East Asian monsoon region is also a transition zone of temperate continental and monsoon climate, which is a sensitive zone of global climate and ecological environment change. It is an urgent problem to find out the long-term climate change rules of this region. Using 101 tree core samples obtained from 54 trees, a 343-year tree-ring width chronology of the Platycladus orientalis (L.) Franco (1673–2016) in the Wula Mountains, Inner Mongolia, China was established. The analysis shows that the radial growth of P. orientalis is closely related to hydrothermal conditions, the average minimum temperature and relative humidity are the main factors that determine the growth of P. orientalis. Based on the strong correlation between the tree-ring indices and the annual average minimum temperature (r = −0.870, p < 0.001), we reconstructed an average annual minimum temperature series from 1673 to 2016 using a linear regression equation, and the reconstructed equation can explain 75.724% of the variance, respectively. According to the data from the past 343 years, the changes in the annual average minimum temperature series had the cycles of 58.6-, 7.7-, 3.4-, 3.1-, 2.2-, and 2.1-years; the series showed three warm periods (1824–1830, 1909–1922, and 1986–2011) and 4 cold periods (1703–1712, 1731–1738, 1754–1763, and 1937–1951). The low temperature periods recorded in the reconstructed series for the 17th and 18th centuries are consistent with the Little Ice Age that occurred in the northern hemisphere, and the heating rate significantly increased at the end of the 20th century. In addition, the cold and warm periods recorded by the reconstruction result is basically consistent with the extreme climate events recorded in the historical documents of the region and the reconstruction results in other regions. In this paper, the world's first chronology of P. orientalis tree ring width was established. A historical sequence of annual average minimum temperature of 343 years was reconstructed in a typical region of the East Asian monsoon climate. It fills in the blank of reconstruction sequence and variation characteristics of mean minimum temperature in the northern edge of East Asian monsoon and transition zone of temperate continental and monsoon climate in recent four centuries. [ABSTRACT FROM AUTHOR]

The Yiluo region in the middle Yellow River has been a core area of archaeological inquiry for understanding the origins of the first dynastic states in China. In order to investigate the social changes on a regional scale, a systematic full-coverage regional survey project was carried out from 1997 to 2018, covering an area of 1183 km2 in the Yiluo region. This paper analyzes the settlement patterns of 451 sites of the Neolithic and Bronze Ages (ca. 6000–200 cal. BC), providing the most comprehensive pictures yet, of the spatial and temporal relationships of settlement distribution during a nearly 6000-year time span. The paper demonstrates a developmental trajectory from a landscape dotted with scattered, small Neolithic villages to a highly centralized dynastic heartland in early Chinese civilization. The evolutionary pathways were not straightforward, but were characterized by episodic fluctuations in population density, and the rise and fall of complex societies. Holocene climatic fluctuations may have played significant roles affecting human activities, but it is the human responses to external challenges in various ways that ultimately determined the trajectories of social evolution. [ABSTRACT FROM AUTHOR]

The 4.2 ka event was one of Holocene abrupt-change events and characterized by dry and cool climatic conditions in many parts of the world. The event was reported to have played important roles in the collapses of those major ancient civilizations. This paper first attempts to portray a global picture of this "4.2 ka Event" and then reviews those reliably-dated sequences containing "4.2 ka Event" retrieved from the domains of four major civilizations. This review further confirms the proposition advocated by the International Stratigraphy Committee that 4.2 ka was the chronological divider between the warmer-wetter middle Holocene and the cooler-drier late Holocene. This review also lends a further support to early proposals that the declines or disruptions of Ancient Egyptian Culture, Mesopotamian Culture, and Ancient Indian Culture at ∼4.2 ka BP were directly or indirectly associated with the "4.2 ka Event". In Chinese cultural domain, the derailment of nearly all of the well-developed Neolithic cultures at ∼4.2 ka BP was also chronologically correlated with the proxy data-recorded abrupt climatic change at ∼4.2 ka BP. But, it should be admitted that either drying or cooling or drying and cooling at ∼4.2 ka BP might not be sufficient to collapse these well-developed cultures in presently warm and wet southern China. Surely, further studies are needed for constraining the climatic and environmental variables at ∼4.2 ka BP not only in southern China but also in the adjacent Central Plains of China. [ABSTRACT FROM AUTHOR]

Henan area is climatologically situated in the transition between northern and southern China and the transition is reported to be highly sensitive to climate changes during the Holocene. To better understand the Holocene climatic and environmental changes in Henan area where high-quality data are lacking, this paper first reviewed those published palaeoenvironmental records in attempt to provide a low-resolution framework of the Holocene environmental changes in Henan area, and then synthesized the moisture proxy records from the surrounding areas in attempt to define a high-resolution trend of the Holocene moisture variation for our target site (i.e., Zhengzhou within Henan area). Two major conclusions can be drawn. First, the high-resolution Holocene moisture curve for our target site well follows the general moisture trend of China and the curve is well corroborated by two recently-reported data sets: one from Mangshan loess-palaeosol sequence and another from Laomu-Dongshiya Cave. Second, our synthesis supports an earlier notion stating that the "Holocene Moisture Optimum" in China was a delayed response to the oceanic "Holocene Thermal Optimum". The latter might in turn be a delayed response to the summer insolation peak. [ABSTRACT FROM AUTHOR]

In recent years, archaeologists have studied how ancient humans have shaped, and been shaped by, their surrounding environments in an effort to provide valuable insight into the patterns of human-environment interaction during prehistoric and historical periods. Along the Heihe River in Hexi Corridor of northwest China, archaeologists have found many ancient cities that are good places to explore changes in human settlement patterns in relation to environment change in historical periods. In this paper, we present our investigation of seven ancient cities to clarify the chronology of these cities and their strategy for wood use in the area through the application of radiocarbon dating and charcoal identification. Our results suggest that the ages of many cities are younger than previous estimates, and humans mainly used Tamarix and mixed Tamarix and broad leaf trees in the lower and middle reaches of the Heihe River basin between ∼ AD 240–1380 respectively, and roughly matches the modern spatial distribution of natural woody vegetation in the area. In comparison to the results of archaeological, paleoclimatic and historical studies in Hexi Corridor, we propose that ancient human strategies for wood use and their impact on environment of the Heihe Basin are primarily relevant to human lifestyles rather than climate change. [ABSTRACT FROM AUTHOR]

In northwestern China, many historical nomadic kingdoms and Chinese dynasties sought to control the Heihe River basin, an important location on the eastern part of the ancient Silk Road. Archaeologists have argued that changes in material culture are tied to the frequent turnover in polities in the area, but no published evidence supports these claims. In this paper, we evaluate the relative importance of environmental and political factors in determining the spatiotemporal pattern of archaeological sites in the middle and lower reaches of the Heihe River basin by using previously published high-resolution paleoclimate records and a variety of historical documents. Our results indicate that humans intensively exploited the Heihe River basin during Han dynasty (202BC–AD 220). Following the Han dynasty, during the Wei-Jin (AD 222–589) and Sui-Tang (AD 581–907) periods the number of archaeological sites. In the Western Xia-Yuan period (AD 1038–1368), people mainly settled in the lower reaches of the Heihe River basin and only returned to the middle reaches of the Heihe River basin during the Ming and Qing dynasties (AD 1368–1912). Although climate change and the local environment affected human activities in Heihe River basin, geopolitical events, such as forced mass migrations, are more responsible for influencing the distribution of archaeological sites over the past 2000 years. [ABSTRACT FROM AUTHOR]

As a part of the INQUA project “A Global Digital Database and Atlas of Quaternary Dune Field and Sand Seas”, 337 age records from the desert dunes of China and 20 from Mongolian dune fields have been compiled in the database. This has opened the possibility of exploring and synthesizing the Quaternary environmental changes in the Asian mid-latitudes dune fields directly from the on-site aeolian sand archives. This paper assessed the sand dune chronologies in terms of geographical distribution, data quality and their implications for late Quaternary palaeoenvironmental reconstructions. The available ages are concentrated mainly in the last 20 ka and many are from the fields of stabilized dunes in the eastern portion of the desert belt in northern China. The number of records and the ratio between the records of stable state and the total records could act as a proxy for the palaeoenvironmental interpretation. The aeolian sand activities deciphered from the chronological data in the eastern portion of the desert belt in northern China show a reasonable correlation with the general global climatic curves at the glacial–interglacial timescales. The limited aeolian sand records from the glacial period, however, hamper the understanding of the detailed features (e.g., forms and processes) of the dune fields during glacial times. In the last two millennia, however, there has not been any meaningful correlation between aeolian dune activity and climatic variation at the centennial time scales, probably due to the complexity of the aeolian sand systems and human interventions. Extending the coverage of dune chronology both temporally and spatially is urgently needed for a full understanding of the environmental changes in the dune fields. [ABSTRACT FROM AUTHOR]

Runoff has been in decline in most river basins in China during the last 50 years. The Weihe River, the largest tributary of the Yellow River, has experienced runoff declines as large as 35% in the last century. Little is known regarding the relative contributions of climate and human impact to the observed hydrological trends in the Weihe River Basin. In the present paper, data from seven hydrological stations and 21 meteorological stations are used to analyze the long-term trends of precipitation, temperature, and streamflow. Using the daily climatic data, a Variable Infiltration capacity (VIC) hydrological model is calibrated and verified to a baseline period from 1956 to 1970. Subsequently, natural runoff for the following years (1971–2006) is reconstructed using the VIC model without considering local human impacts. On the basis of observed meteorological data and runoff and the reconstructed runoff data from 1971 to 2006 in the Weihe River Basin, we quantified long-term trends and decadal and annual variations. The results showed that precipitation and runoff have decreased since the baseline decade. We further estimated the relative contributions of human activity and climate change to the hydrological response of the Weihe River Basin and determined that human activity (such as large-scale soil conservation practices and large irrigation areas) has a greater impact on basin runoff than do climate change factors. The percentages in change of runoff due to climate change ( PC ) are 36%, 28%, 53% and 10% in the 1970s, 1980s 1990s and 2000s, respectively. The percentages in change of runoff caused by human activity ( PH ) are 64%, 72%, 47%, and 90%, respectively. [ABSTRACT FROM AUTHOR]

Based on the data of five observed meteorological elements (temperature, precipitation, wind speed, sunshine duration, and relative humidity) from 22 stations, the paper investigated the climate variations in northern Xinjiang over the past 50 years. The analytical results showed that both the temperature and the precipitation have increased significantly (0.35 °C/10 y, 11.2 mm/10 y) during the period of 1960–2011. An abrupt change was detected to have occurred in 1986 for temperature and in 1987 for precipitation. Autumn was the season when the temperature increased most dramatically, and winter and autumn were the seasons when the precipitation increased most dramatically. The twenty years after 1990 were the warmest and wettest two decades of the past ∼50 years, but the warming and wetting paces have slowed down during the same period. The results also showed that the mean annual minimum temperature increased more dramatically than the mean annual maximum temperature, resulting in a greatly reduced diurnal range. The reasons or mechanisms for rising trend of temperature during the past 50 years and also for the faster rising rate of the temperature in northern Xinjiang and the adjacent areas have been reasonably explored in published literature. However, the reasons or mechanisms for the rising trend of the past 50-year precipitation in northern Xinjiang and the adjacent areas have not been reasonably explored. This wetting trend has not extended further to the surrounding areas including Republic of Mongolia, major part of North China, and five republics of the former Soviet Union, and the need is thus pressing to explore the reasons or mechanisms behind this relatively “localized” wetting trend. [ABSTRACT FROM AUTHOR]