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Abstract Because of similar astronomical background, Marine Isotope Stage (MIS) 11 is viewed as an analogue of the Holocene, but the evolution of seasonal climatic instability during MIS 11 has not been well investigated. Here we present a time series of land-snail eggs—a recently-developed proxy of seasonal cooling events—from the Chinese Loess Plateau (CLP) to investigate seasonal climatic instability during MIS 11 and adjacent glacials. Due to the impact of low temperatures on egg hatching, egg-abundance peaks document seasonal cooling events. A total of five egg-abundance peaks were recorded in the CLP during MIS 12, MIS 11 and MIS 10. Three peaks are strong and occur close to glacial inception or interglacial-to-glacial transition; two weaker peaks occur during MIS11. These peaks imply seasonal climatic instability intensifies mainly during glacial initiation or transition. All these events correspond to ice-sheet growth and the loss of ice-rafted debris at high northern latitudes. Moreover, they occurred at the minima of local spring insolation during the MIS 12 and MIS 10 glacials, but at the maxima during the MIS 11 interglacial. This may contribute to the difference in the intensity of seasonal cooling events between low-eccentricity glacials and interglacials. Our results provide new evidence for understanding low-eccentricity interglacial–glacial evolution.

Abstract Fluctuations in monsoonal climate on orbital‐ to millennial‐timescales have had a major impact on vegetation change in East Asia since the last deglaciation. However, the influence of centennial‐scale oscillations on the spatio‐temporal characteristics of vegetation and climate during the last deglaciation remains controversial. We present a well‐dated, decadal‐resolution pollen record from the sediments of annually laminated Lake Xiaolongwan in Northeast Asia, which reveals major orbital‐/millennial‐scale and minor quasi‐periodic, that is, ∼500‐year (yr) cyclic, vegetation changes from ∼19.96 to ∼10.79 Kyr ago (covering the last deglaciation). The ∼500‐yr cycles are characterized by alternations in broadleaved forest/boreal coniferous forest with tundra steppe representing warm and humid/cold and dry phases of the monsoonal climate. This cyclicity may be related to El Niño‐like/La Niña‐like state and low‐latitude atmosphere‐ocean processes, against the background of the long‐term trend of the deglacial climatic evolution. Our findings demonstrate a close relationship between ecosystem succession and climate change on centennial scale.

Scientists have been puzzled by the disparity between climate simulations of the past 12,000 years and geological records. Dong et al. reconstructed past annual and seasonal temperatures from land snail records to examine the potential seasonal bias.

Abstract A new, seasonal, laminated ice core pollen record spanning the last 13 years (2000–2012) from Zuoqiupu Glacier (5,600 m a.s.l.), located on the southeastern Tibetan Plateau (TP), reveals clear variations in pollen concentration and assemblage. A total of 117 continuous ice core layers were used for pollen analysis. Samples with high concentrations of Pinus and Tsuga could be identified as layers accumulated in spring, samples with high concentrations of Alnus and Artemisia could be identified as layers accumulated in autumn, and samples rich in herbaceous plant pollen could be regarded as layers deposited in summer. Three peaks of Tsuga pollen concentration accompanied by high Pinus content occurred in the spring of 2003, 2007, and 2010, which corresponded to wetter and warmer conditions modulated by the El Niño decaying phase (April–May in 2003, 2007, and 2010). Thus, pollen grains deposited on the Zuoqiupu Glacier can be used to study the impacts of atmospheric circulations on seasonal climate change over the southeastern TP.

Legumes and cereals, which provide different nutrients, are cultivated as coupled crops in most centers of plant domestication worldwide. However, as the only legume domesticated in China, the spatio-temporal distribution of soybeans and its status in the millet- and rice-based agricultural system of the Neolithic and Bronze Ages remains elusive. Here, archaeobotanical evidence of soybeans (n=254), millet (n=462), rice (n=482), and zooarchaeological evidence of fish (n=138) were synthesized to elucidate the phenomenon of coupled or decoupled cereals and legumes in prehistoric China. During the Neolithic and Bronze Ages, soybeans was mostly confined to northern China and rarely found in southern China, serving as a companion to millet. In contrast, fish remains have been widely found in southern China, indicating a continuous reliance on fish as a staple food besides rice. Thus, an antipodal pattern of millet-soybeans and rice-fish agricultural systems may have been established in northern and southern China since the late Yangshao period (6000–5000 cal BP) respectively. These two agricultural systems were not only complementary in terms of diet, but they also exhibited positive interactions and feedback in the coculture system. Consequently, these two systems enabled the sustainable intensification of agriculture and served as the basis for the emergence of complex societies and early states in the Yellow and Yangtze Rivers.

The Zang-Yi Corridor is of pivotal significance for the interactions between northwest China, southwest China, and mainland Southeast Asia. It has been hypothesized that the formation of mixed farming in this region and its surrounding areas was based on multiple waves of crop dispersal, with foxtail millet and broomcorn millet arriving first from northwest China around 5,300 cal. BP and rice from middle Yangtze valley after 4,700 cal. BP. Based on the systematic sampling and direct dating conducted at the Guijiabao site, Sichuan Province, this study demonstrates that by no later than 5,000 cal. BP, mixed farming had already emerged in the south part of Zang-Yi corridor, which was much earlier than expected before. With this new evidence, it is argued that the transformation into farming in Southwest China was based on the dispersal of a crop package comprising foxtail millet, broomcorn millet, and rice instead of different waves of introduction. A further comparison of all archaeobotanical data in this region revealed that crop patterns varied significantly between different sites because of their diverse environmental conditions.

Human activity has transformed the Earth’s landscapes pervasively for thousands of years, and the most important anthropogenic alteration was the clearing of forests and the establishment of agriculture. As a center of rice domestication and early population growth, the lower Yangtze River has been extensively transformed in the Holocene. However, the timing, extent, and process of deforestation and its relationship with the intensification of rice cultivation remain controversial. Here, four representative archaeological sites ranging from 8,100 to 4,300 cal a BP, that is, Jingtoushan, Hemudu, Yushan, and Xiawangdu sites, were selected for detailed palynological analysis, and evidence of anthropogenic deforestation and subsistence strategy were also synthesized to investigate dynamic human–forest interaction. Although natural vegetation had already been altered at the Jingtoushan site around 8,000 cal a BP, it was more likely to be the management of acorns by limiting burning to open habitats and increasing yield. As the subsistence shifted from acorn exploitation toward rice cultivation after 6,000 cal a BP, real deforestation for agriculture may occur at the Yushan and Xiawangdu sites due to conflict on labor input and land use. However, these deforestations were just confined to the archaeological sites at local scale, and no consistent vegetation change occurred at regional scales induced by human activities until the last 3,000 years.

The magnitude and rate of the expansion of the East Asian summer monsoon (EASM) rain belt under future climatic warming are unclear. Appropriate ecological proxy data may provide an improved understanding of the spatial extension of the EASM during past warming intervals. We reconstructed the spatiotemporal pattern of the extension of the EASM since the Last Glacial Maximum (LGM), using six well-dated mollusk fossil sequences from Chinese loess sections located on the modern northern edge of the EASM. The abundance of typical dominant mollusk species indicative of EASM intensity shows a delayed response, from ∼17 ka in the southeastern sections to ∼9 ka in the northwestern sections, during the last deglacial warming. Isoline plots based on a mollusk data synthesis show that the mollusk EASM indicators have a northeast–southwest zonal distribution for both the present-day, the cold LGM, and the warm mid-Holocene, which is consistent with the spatial pattern of modern precipitation. The resulting estimated expansion rate of EASM intensity accelerated during ∼12–9 ka (∼50 km/ka), which corresponds to the early Holocene interval of rapid climatic warming, a northwestward shift of ∼150 km compared to today. This implies that the northern fringe of the EASM in northern China will become wetter in the coming century, under moderate warming scenarios.

Identifying when agricultural expansion has occurred and how it altered the landscape is critical for understanding human social survival strategies as well as current ecological diversity. In the present study, phytolith records of three profiles from the Baodun site area were dated to the period from 7,500 to 2,500 aBP by optically stimulated luminescence and 14C dating, providing the first evidence that the Asian cultivated rice (Oryza sativa) progenitor was distributed in the Chengdu Plain as early as 7,500 aBP. The percentage of rice bulliform with ≥9 scales and the concentration of rice phytoliths sharply increased by approximately 4,200 aBP, suggesting that rice cultivation occupied a dominant position in survival strategy no later than approximately 4,200 aBP, which might be driven by climate deterioration in eastern China. The results further showed that the proportion of Bambusoideae phytoliths increased synchronously with the increase in the proportion of rice phytoliths, suggesting that the vegetation structure near the site was changed intentionally as a consequence of increasing rice agricultural activity since 4,200 aBP. The present study contributes to a deeper understanding of the distribution of wild rice and rice farming throughout the Baodun culture in the Chengdu Plain, and it also provides a glimpse of how humans intentionally changed the vegetation landscape on a local scale.

Neolithic rice remains were recovered from a mixed rice–millet farming area in China outside the original centers of rice farming. Whether the rice remains were the result of local cultivation or obtained through trade remains unclear. Rice paddy fields are direct evidence of local cultivation. In this study, phytolith samples from the Zhangwangzhuang site were analyzed. The discriminant function distinguished 17 of 30 samples in the suspected paddy field area as rice paddy fields with an average probability of 74%; The proportion of rice bulliform phytoliths with ≥9 scales indicated that rice (Oryza sativa) was still being domesticated and, moreover, six η-type phytoliths from broomcorn millet (Panicum miliaceum) were identified. These results suggested that the suspected paddy field at Zhangwangzhuang might be the earliest rice paddy field (ca. 6000 cal. BP) in northern China and that mixed farming was practiced here since the early Yangshao period. This study adopted discriminant analysis methods to discover ancient rice paddy fields, observed rice paddy fields outside the core rice origin area, and provided the earliest evidence regarding the development of mixed rice–millet farming in the upper Huai River region.

Soil carbon isotopes (d13C) provide reliable insights at a long-term scale for studying soil carbon turnover. The Tibetan Plateau (TP), called “the third pole of the earth” is one of the most sensitive areas to global climate change and exhibits an early warning signal of global warming. Although many studies detected the variability of soil d13C at site scales, a knowledge gap still exists in the spatial pattern of topsoil d13C across the TP. To fill the substantial knowledge gap, we first compiled a database of topsoil d13CC with 396 observations from published literatures. Then we applied a Random Forest (RF) algorithm – a machine learning approach, to predict the spatial pattern of topsoil d13C and ß (indicating the decomposition rate of soil organic carbon (SOC), calculated by d13C divided by logarithmically converted SOC). Finally, two datasets - topsoil d13C and ß with a fine spatial resolution of 1 km across the TP were developed. Results showed that topsoil d13C varied significantly among different ecosystem types (p < 0.001). Topsoil d13C was -26.3 ± 1.60 ‰ (mean ± standard deviation) for forests, 24.3 ± 2.00 ‰ for shrublands, -23.9 ± 1.84 ‰ for grasslands, -18.9 ± 2.37 ‰ for deserts, respectively. RF could well predict the spatial variability of topsoil d13C with a model efficiency of 0.62 and root mean square error of 1.12 ‰, enabling to derive data-driven d13C and ß products. Data-driven topsoil d13C varied from -28.26 ‰ to -16.95 ‰, with the highest topsoil d13C in the north and northwest TP and the lowest d13C in Southeast or South TP, indicating strong spatial variabilities in topsoil d13C. Similarly, there were strong spatial variabilities in data-driven ß, with the lowest ß values at the east and middle TP, indicating a higher SOC turnover in the east and middle TP compared that of other regions in the TP. This study was the first attempt to develop a fine resolution product of topsoil d13C and ß across the TP, which could provide an independent data-driven benchmark for biogeochemical cycling models to study SOC turnover and terrestrial carbon-climate feedbacks over the TP under climate change. The data-driven d13C and ß datasets are public available at https://doi.org/10.6084/m9.figshare.16641292.v2 (Tang, 2021) [ABSTRACT FROM AUTHOR]