Xin Jia

The transition of human subsistence strategies in relation to climate change during the Bronze Age in the West Liao River Basin, Northeast China

Despite the proposed climate–human connection in the West Liao River Basin during the Bronze Age, the question of how climate change could have affected the subsistence strategies, and consequently, the cultural transformation from the Lower Xiajiadian to the Upper Xiajiadian periods, has never been systematically explored. Based on radiocarbon dating and the analysis of plant remains recovered by flotation, as well as the spatial distribution of archaeological sites, this study investigates the subsistence strategies of ancient people and their influence on cultural development in the West Liao River Basin during the Lower Xiajiadian (3900–3400 cal. yr BP) and Upper Xiajiadian periods (3000–2500 cal. yr BP). Carbonized seeds collected from 13 archaeological sites reveal that people engaged in millet-based agriculture in this area throughout the Bronze Age. Favorable climate during the Holocene Optimum promoted millet farming among the Lower Xiajiadian Culture. The end of the Holocene Optimum and its associated climate deterioration led to agricultural shrinkage in the Upper Xiajiadian period, which is revealed by the reduced amount of carbonized millet seeds and the ratio between foxtail millet and broomcorn millet. Climate deterioration led to diverse subsistence strategies, resulting in the dispersal of human settlements and the differentiation of the spatial distributions of different groups. People with millet-based subsistence strategies retreated southward, while people with animal husbandry and hunting-based subsistence strategies migrated westward. The above findings may offer insights in comprehending how climate deterioration could have affected the multi-facets of human societies in the West Liao River Basin, which is a climatically sensitive region, in Chinese prehistory.

Climate change and epidemics in Chinese history: A multi-scalar analysis

This study seeks to provide further insight regarding the relationship of climate-epidemics in Chinese history through a multi-scalar analysis. Based on 5961 epidemic incidents in China during 1370-1909 CE we applied Ordinary Least Square regression and panel data regression to verify the climate-epidemic nexus over a range of spatial scales (country, macro region, and province). Results show that epidemic outbreaks were negatively correlated with the temperature in historical China at various geographic levels, while a stark reduction in the correlational strength was observed at lower geographic levels. Furthermore, cooling drove up epidemic outbreaks in northern and central China, where population pressure reached a clear threshold for amplifying the vulnerability of epidemic outbreaks to climate change. Our findings help to illustrate the modifiable areal unit and the uncertain geographic context problems in climate-epidemics research. Researchers need to consider the scale effect in the course of statistical analyses, which are currently predominantly conducted on a national/single scale; and also the importance of how the study area is delineated, an issue which is rarely discussed in the climate-epidemics literature. Future research may leverage our results and provide a cross-analysis with those derived from spatial analysis.

Spatial and temporal variations in prehistoric human settlement and their influencing factors on the south bank of the Xar Moron River, Northeastern China

The West Liao River Basin is the hub of ancient civilizations as well as the birthplace of rain-fed agriculture in Northern China. In the present study, based on 276 archaeological sites on the south bank of the Xar Moron River, Northeastern China, we trace the changes in prehistoric cultures as well as the shifts in the spatial and temporal patterns of human settlement in the West Liao River Basin. Location information for those sites was obtained from fieldwork. Factors such as climate change, landform evolution of the Horqin Dunefield, and subsistence strategies practiced at the sites were extracted via the meta-analysis of published literature. Our results show that the Holocene Optimum promoted the emergence of Neolithic Culture on the south bank of the Xar Moron River. Monsoon failure might have caused the periodic collapse or transformation of prehistoric cultures at (6.5, 4.7, 3.9, and 3.0) kyr B.P., leaving spaces for new cultural types to develop after these gaps. The rise and fall of different cultures was also determined by subsistence strategies. The Xiaoheyan Culture, with mixed modes of subsistence, weakened after 4.7 kyr B.P., whereas the Upper Xiajiadian Culture, supported by sheep breeding, expanded after 3.0 kyr B.P. Global positioning system data obtained from the archaeological sites reveal that cultures with different subsistence strategies occupied distinct geographic regions. Humans who subsisted on hunting and gathering resided at higher altitudes during the Paleolithic Age (1074 m a.s.l.). Mixed subsistence strategies led humans to settle down at 600–1000 m a.s.l. in the Neolithic Age. Agricultural activities caused humans to migrate to 400–800 m a.s.l. in the early Bronze Age, whereas livestock production shifted human activities to 800–1200 m a.s.l. in the late Bronze Age.

Quantitative analysis of the impact of droughts and floods on internal wars in China over the last 500 years

Although many large-N quantitative studies have evidenced the adverse effects of climatic extremes on social stability in China during the historical period, most of them rely on temperature and precipitation as major explanatory variables, while the influence of floods and droughts on social crises is rarely measured. Furthermore, a comparison of the climate-society nexus among different geographic regions and at different temporal scales is missing in those studies. To address this knowledge gap, this study examines quantitatively the influence of floods and droughts on internal wars in three agro-ecological (rice, wheat, and pastoral) regions in China in AD1470–1911. Poisson regression and wavelet transform coherence analyses are applied to allow for the non-linear and non-stationary nature of the climate-war nexus. Results show that floods and droughts are significant in driving internal wars in historical China, but are characterized by strong regional variation. In the rice region, floods trigger internal wars at the inter-annual and multi-decadal time scales. In the wheat region, both floods and droughts cause internal wars at the inter-annual and multi-decadal time scales. In the pastoral region, internal wars are associated with floods only at the multi-decadal time scale. In addition, the multi-decadal coherence between hydro-climatic extremes and internal wars in all three of the agro-ecological regions is only significant in periods in which population density is increasing or the upper limit of regional carrying capacity is being reached. The above results imply that the climate-war nexus is mediated by regional geographic factors such as physical environmental setting and population pressure. Hence, we encourage researchers who study the historical human-climate relationship to boil down data according to geographic regions in the course of statistical analysis and to examine each region individually in follow-up studies.

A modified depositional hypothesis of the Hanjiang Loess in the southern Qinling Mountains, central China

Geomorphologically, alluvial deposits in river systems are expected to be older on higher terraces than on the lower terraces. However, loess deposits of aeolian origin may also occur on the surface of terrace systems and as seen in the Chinese Loess Plateau (CLP). Such loess is continuously, rather than episodically deposited. This study presents numerous dating results of loess cover on the Hanjiang River terrace system in the southern Qinling Mountains, an atypical loess deposit belt outside of the CLP. We name this “Hanjiang Loess”. Results indicate that the Hanjiang Loess deposited on the high, middle, and low terraces are also the oldest, old, and most recent, respectively, apparently analogous with alluvial expectations. We thus propose a modified depositional hypothesis, whereby terrace loess reflects the deposition of aeolian loess and other material, subsequent fluvial reworking. This depositional hypothesis should also be applicable to loess deposits on the river terraces in the Xiashu Loess, Quaternary Reticulate Red Clay, and Quaternary Red Clay in southern China, and other atypical loess areas outside of the CLP.

Habitat Variability and Ethnic Diversity in Northern Tibetan Plateau

There are 56 officially-recognized ethnic groups in China. However, the distinct geographic patterns of various ethnic groups in relation to the physical environment in China have rarely been investigated. Based on the geo-referenced physical environmental parameters of 455 Han, Tu, Hui, Salar, Mongolian, and Tibetan communities in Qinghai, we found that the communities could be statistically demarcated by temperature and aridity threshold according to their ethnicity, implying that the geographic distribution of each ethnic group is mediated by the physical environment. We also observed that the habitat of each ethnic group is ecologically compatible with current subsistence strategies. Tibetans settle in cold and humid high-altitude regions owing to the cultivation of highland barley and the breeding of yak, dzo, Tibetan sheep and Tibetan goat. Mongolians survive by animal husbandry in cold and dry grassland areas. Han and Tu people settle in the Huangshui River Valley, which offers relatively humid climate and flat land for agriculture. Hui and Salar people occupy the Yellow River Valley with its relatively arid environment and grassland vegetation suitable for animal breeding. Our findings offer a new perspective in explaining the geographic patterns and the varieties of ethnic groups in China and elsewhere.

Relationship between ancient bridges and population dynamics in the lower Yangtze River Basin, China

It has been suggested that population growth dynamics may be revealed by the geographic distribution and the physical structure of ancient bridges. Yet, this relationship has not been empirically verified. In this study, we applied the archaeological records for ancient bridges to reveal the population growth dynamics in the lower Yangtze River Basin in late imperial China. We investigated 89 ancient bridges in Yixing that were built during the Ming and Qing dynasties (AD1368–1911). Global Position System information and structure (length, width, and span) of those bridges was measured during our field investigations. Their distribution density was calculated by ArcGIS. The historical socio-economic dynamics of Yixing was inferred from the distribution and structure of ancient bridges. Based on the above information, the population growth dynamics in Yixing was projected. Our results show that 77 bridges were built in Yixing during the Qing dynasty, which is 6.41 times more than the number built during the Ming dynasty. In the Ming dynasty, bridges were built on pivotal routes; in the Qing dynasty, bridges were scattered across various places. Over the period, the density distribution of bridges shifted northwestward, while the average length and width of bridges decreased. The increasing number of bridges corresponded to population growth, largely attributable to massive clan migration from northern China during the Little Ice Age. The shift in the density distribution of bridges corresponded to the formation of settlements of large clans and the blossoming of Yixing Teapot handicrafts. The scattering and the reduction in average length and width of bridges was due to the dispersal of population and the associated formation of small settlements in the latter period. Our approach is innovative and robust, and could be employed to recover long-term historical population growth dynamics in other parts of China.