Coniferous interpretation: pine revealed the secrets of China's "golden age"

Based on the analysis of ancient wood, an international group of scientists, including employees of the Siberian Federal University, identified the prerequisites for the rapid flourishing of Chinese statehood at the end of the 3rd century BC (the "golden era") and the formation of the state of Qin, the first centralized empire of China. The research was based on computational models developed by Russian specialists. Experts, studying ancient and modern fragments of Chinese pine, confirmed the information that the increase in climate humidity during the "golden era" gave an impetus to the development of agriculture and, as a result, other areas of public life.

How the Qin Empire influenced the development of the Chinese state

The reason for the flourishing of Chinese civilization about 2.2 thousand years ago could be climatic conditions. Namely, a steady period of increased humidity, which at that time was 15-35% higher than it is now. This is the conclusion reached by an international scientific group of scientists who examined fragments of ancient wood.

Experts from Russia, China, Germany and several other European countries participated in the project. However, the scientific work is based on a computational model created by Russian scientists.

This technique is called the "Vaganov–Shashkin model" after the names of the creators who developed it at the end of the twentieth century. It allows us to analyze how climatic factors such as temperature, precipitation, and light conditions affect tree growth in different historical periods. The model is widely used to reconstruct the climate of the past.

— One of the most striking examples of the application of the technique was the study of natural conditions that existed during the reign of the Qin and Western Han dynasties in China. The research was conducted on the initiative of the Chinese side. Together, these dynasties span a period of about 270 years. It was the time of the most significant rise and prosperity of Chinese civilization," Vladimir Shishov, one of the project participants and director of the Institute of Fundamental Biology and Biotechnology at Siberian Federal University (SibFU), told Izvestia.

He recalled that the Qin Dynasty (259-206 BC) was able to end internecine wars and unite inner China into a single empire. At that time, the ancient state was led by Emperor Qin Shi Huang, known worldwide for an army of more than 8,000 terracotta sculptures of soldiers that were placed with him in the tomb.

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This ruler subjugated the surrounding kingdoms, creating a powerful centralized empire, and in the domestic area initiated the construction of the Great Wall of China, canals and a number of other major infrastructure projects.

At the same time, the period of the Western Han Dynasty (206 BC - 9th AD) is significant for the development of the Great Silk Road, the rise of agriculture, technology, science and art.

— In In the course of our research, we studied samples of Chinese pine — both living trees and half-fossil wood that has been preserved in the ground, as well as in the form of various cultural artifacts. Chinese experts have collected a large amount of data in the vicinity of the city of Xi'an, which was the capital of the Qin and Western Han empires. Next, the specialists measured the width of the annual rings and conducted an isotopic analysis of the wood. Then the data obtained was embedded in the Vaganov–Shashkin computational model," Vladimir Shishov said.

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In particular, he explained, the well-known radiocarbon dating method was used by measuring the ratio of the radioactive carbon isotope 14C to its stable analog 13C. Other more specific methods of wood research were also used.

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According to Vladimir Shishov, the low content of carbon 13C and oxygen 18O isotopes in wood in the past may indicate significant moistening of the empire's territory compared to the modern period, for example, due to heavy monsoon rains at the turn of our era. Moreover, an analysis of the width of the growth rings and the carbon isotope 13C showed that the ancient climate was also more stable than the modern one.

However, carbon isotopes help identify periods of drought. So, when there is a lack of water, trees close stomata — holes in the outer layer of cells through which gas exchange with the environment takes place. This leads to a change in the ratio of carbon isotopes 13C and 12C in plant tissues.

— The main equation of the Vaganov–Shashkin model describes the growth rate of trees as a mathematical function that depends on temperature, soil moisture and sunlight. They influence the processes of formation of wood cells, which, in turn, determine the width of the annual rings. At the same time, the increase in plant mass is limited to the most scarce resource. For example, if the temperature is optimal, but the soil moisture is low, the slowdown in growth will be determined precisely by the lack of water," said Vladimir Shishov.

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As a result, analysis of the obtained primary data and computational experiments have shown that the climate of ancient China during the reign of the Qin and Han dynasties was characterized by stable high humidity, which favorably affected the productivity of woody plants and crops. During this period, the annual precipitation, for example, was 16-34% higher than the current instrumental observations for the period 1951-2015.

This has led to a significant increase in land that is suitable for agriculture. So, they expanded to the north and northwest, by 60-100 km, and in some cases even by 200 km, the scientist said. In turn, the development of the agricultural sector, food production and other agricultural materials contributed to an increase in the population and the development of economic relations.

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Thus, in the course of the study, experts presented new evidence that the stable and humid climate in China played a key role in the socio-economic development and formation of ancient great empires, emphasized Vladimir Shishov.

At the same time, the scientist noted, the Vaganov–Shishkin model is effective not only for analyzing the climate of the past, but also for future research. For example, this tool will help predict the state of forests in conditions of modern and global warming. This will make it possible to understand in advance the consequences of such changes and take measures, for example, for sustainable forest management.

— History knows many examples where regional and global climate changes have had an impact on the development of society. Thus, a favorable period in Mongolia in the 13th century contributed to the growth of livestock, increased forage and, as a result, the formation of the empire of Genghis Khan. On the territory of the Scandinavian Peninsula, warming began in the VI–VIII centuries, which caused the appearance of the Vikings and their expansion," said Alexey Matveev, head of the Window to Asia section of the Irkutsk Regional Museum of Local Lore.

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In both cases, he added, climate change initially led to an increase in agricultural and pasture productivity, and the subsequent scenario depended on the adaptability of society. In the case of the Qin Dynasty, China was unified, which caused rapid urban development and road construction. The study once again confirms the influence of climate on the development of ancient societies.

— It is known from a number of historical sources that a lot of rain fell in China during the reign of Qin Shi Huang. Floods took away crops. For this reason, the emperor pursued a policy of building drainage and irrigation canals. As a result, officials recorded an increase in yields. By coping with the floods, this ruler accelerated the Chinese economy," said Yuri Turkan, Chairman of the Board of the Association for the Promotion of Russian—Chinese Tourism.

He noted that the legacy of Qin Shi Huang — the reform of public administration, equalization of the rights of peoples, standardization of the writing system, weights and measures, and other innovations — are still reflected in the development of China.