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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]

The Changbaishan volcano, located in northeast China, produced a large amount of charcoal during the "Millennium Eruption" (c. 946 CE). In this paper, we report a high-resolution date for the eruption using multiple methods applied to the fossil charcoal and living trees, including wood anatomy, radiocarbon dating and tree-ring cross-dating. In addition, we develop a new floating annual-resolution tree-ring chronology spanning nearly 200 years that provides information about paleoclimate conditions. In our study, we identified 60 samples of charcoal as Larix olgensis based on anatomical characteristics and geographical location. Using these materials, we dated the eruption to the winter of 946 CE based on a combination of radiocarbon dating, traditional dendrochronological cross-dating and cambial cell growth status. This allowed us to develop an L. olgensis tree-ring width chronology covering 764–946 CE and 1715–2016 CE, with significant sensitivities to April–September temperature (p < 0.05). The tree-ring data have great potential to indicate extreme climate events; for example, we identify an extremely cold year in 903 CE. Such marker years can improve the reliability and accuracy of tree-ring data. Our study provides direct and precise tree-ring evidence for volcanic eruptions and anomalous climate years in the Middle Ages. [Display omitted] • Cambial activity enables us to date the Millennium Eruption to winter 946 CE. • The first chronology reaching the Middle Ages so far developed in northeastern China. • The chronology was assembled from volcanic charcoal and living larch. • This chronology is sensitive to temperature. [ABSTRACT FROM AUTHOR]

Disentangling fire and its controls over thousands of years ago is a major challenge in the study of paleofires. In this paper, we synthesize sedimentary charcoal and black carbon from the coastal plain of Laizhou Bay, China to improve our ability to reconstruct fire history in the past 5000 years, and to assess the controls of fire using principal component analysis and multiple regression approach. The results show that there were three distinct fire episodes at the intervals of 5300–5100 yr BP., 1190–1060 yr BP., and 300–0 yr BP., based on the Changyi (CY) profile. A large-scale fire episode was synchronous with a rapid climate variability that occurred 5300 yr BP., which had frequent drought and cold epoch. High fluxes of black carbon and charcoal were closely related to mass migration and the use of fire for land reclamation from 1190 to 1060 yr BP. Subsequently, anthropogenic biomass burning for cereal cultivation has reached a higher level over the past 300 years. However, between 4600 and 4000 yr BP. the shifts in the frequency of high-magnitude floods and climate aridity consequently resulted in the decline of fire-episode frequency and the abandonment of the late Neolithic settlements in the study region. Therefore, climate is still a prerequisite factor for fire occurrence on the southern coast of Laizhou Bay in the past 5000 years. A rapid climate variability was not only responsible for various fire patterns, but also could affect human settlements and the mode of production during middle-late Holocene. In the past 1000 years, human land use has been a more important control of fire. However, temperature has become one of the evidently identified controls of fire across the study area in recent decades. To synthesize the methods of Principal Component Analysis and Multiple Regression Analysis with multi-proxy evidence is necessary for us to better understand fire and its controls on coastal plain of Laizhou Bay at the region. • Charcoal and BC have recorded fire mid-Holocene at the Laizhou Bay of China. • Climate was still a prerequisite control of fire at the Laizhou Bay mid-Holocene. • In the past 1000 years, human land use has been an important control of fire. • Temperature has become one of the identified controls of fire across the study area. • Principal component analysis will contribute to disentangling fire and its controls. [ABSTRACT FROM AUTHOR]