Brief introduction to the characteristics of the upper, middle and lower reaches of the Yangtze River

The upper reaches of the Yangtze River refer to the reach from the source of the Yangtze River to Yichang, Hubei, involving Chongqing, Sichuan, Tibet, Qinghai, Yunnan and Guizhou. The source of the Yangtze River is located in the hinterland of the Qinghai-Tibet Plateau, where the terrain is high, the air is thin, the climate is bad, the traffic is dangerous and inaccessible. The source of the Yangtze River is detached, the Dangqu in the south and the Chuma River in the north all originate from here. After these three sources meet, people call it Tongtian River. Tongtian River flows through Yushu, Qinghai, where the sunshine is abundant, the air is fresh, and there are green and open grass beaches along the river. It is an important animal husbandry area in the Yangtze River basin.

The banded plain in the middle and lower reaches east of the Three Gorges of the Yangtze River in China. Huaiyang Mountain and Huanghuai Plain are in the north, and Jiangnan hills and Zhejiang and Fujian hills are in the south. It is alluvial from the Yangtze River and its tributaries. It covers an area of about 200,000 square kilometers. The terrain is low and flat, and the altitude is mostly about 50 meters. The middle reaches include Jianghan Plain in Hubei, Dongting Lake Plain in Hunan and Poyang Lake Plain in Jiangxi. The downstream plains include the plain along the Yangtze River and Chaohu Lake in Anhui Province (the central plain of Anhui Province), and the Yangtze River Delta between Jiangsu, Zhejiang and Shanghai.

Most of the climate belongs to the north subtropical zone, and a small part belongs to the northern edge of the middle subtropical zone. The annual average temperature is 14 ~ 18℃, the most Leng Yue average temperature is 0 ~ 5.5℃, the absolute minimum temperature is-10 ~-20℃, the hottest month average temperature is 27 ~ 28℃, and the frost-free period is 2 10 ~ 270 days. For agricultural crops, the annual precipitation is 1000 ~ 1400 mm, which is concentrated in spring and summer. Zonal soil is only found in low hills and gentle hills, mainly yellow brown soil or yellow cinnamon soil. The southern margin is red soil, and most of the plains are paddy soil. With developed agriculture and high land reclamation index (62. 1% in Shanghai and 45.6% in Jiangsu), it is an important grain, cotton and oil production base. Rich in rice, wheat, cotton, rape, silkworm, ramie, jute and so on. Rivers and branches crisscross, and lakes are dotted. The lake covers an area of 20,000 square kilometers, equivalent to 10% of the plain area.

Large lakes, including small lakes, have an area of10.3 million square kilometers, accounting for more than 20% of the plain area of the two lakes, which is the place with the largest number of lakes in China. There are fresh water lakes such as Poyang Lake, Dongting Lake, Taihu Lake, Hongze Lake and Chaohu Lake, which are connected with the Yangtze River and have the functions of regulating water volume and reducing flood peak. They produce fish, shrimp, crab, lotus, water chestnut and reed, as well as world treasures such as Chinese sturgeon, Chinese alligator and baiji. Aquatic products occupy an important position in China, known as the land of plenty. It is one of the most economically developed areas, including Shanghai, Nanjing, Wuhan, Changsha, Hefei, Nanchang, Suzhou, Wuxi, Changzhou, Yangzhou, Nantong, Wuhu, Anqing, Jiujiang, Yueyang and Yichang.

The main industries are steel, machinery, electricity, textiles and chemistry, and it is an important industrial base. The plain is located in the hub of China's north-south and east-west transportation networks, with developed land and water transportation. The Yangtze River runs through the middle and becomes an east-west waterway artery, and its many tributaries form a huge waterway network. The middle and lower reaches of the Yangtze River are located on both sides of the Yangtze River and its tributaries east of Wushan, and are divided into four parts by the surrounding low hills (see Jiangnan hills): the two lakes plain, the Poyang Lake plain, the central Anhui plain and the Yangtze River Delta, with an area of 300,000 square kilometers and an altitude of less than 50 meters. The Yangtze River Delta is located in the east of Zhenjiang, Jiangsu Province, north of Hangzhou Bay and south of Toarey Yang Canal, with an area of about 50,000 square kilometers, and the elevation is mostly below 10. Known as "Water Town Zeguo", it is one of the most densely populated areas in China.

The two lakes plain is bounded by Jingjiang River, which is called Jianghan Plain in the north and Dongting Lake Plain in the south. Jianghan Plain is mainly formed by alluvial deposits of the Yangtze River and the Han River. Since the entrance of Jingjiang North dike into Jianghan Plain was completely blocked around 1300, the sediment carried by Hanjiang River has played a major role in the development of Jianghan Plain, and its delta has become an important part of Jianghan Plain. The terrain of the Hanjiang River Delta is also slightly inclined from northwest to southeast, and there are many lakes in the southeast front. Dongting Lake Plain is mainly formed by the Yangtze River sediment flowing southward through Taiping, Ouchi, Songzi and Tiao County (blocked at 1958) on the south bank of Jingjiang River. The area is about 1 1,000 square kilometers. Most of them are below 50 meters above sea level, high in the north and low in the south, with dense water networks and fertile soil.

The flood plain in the middle of Poyang Lake Plain, except the red mounds at the edge, is mainly formed by the scouring and silting of rivers such as Jiangxi, Fuzhou, Xinjiang, Poyang Lake and Xiushan, among which Ganjiang is the main one. It covers an area of about 20,000 square kilometers. The terrain is low and flat, most of which are below 50 meters above sea level. The water network is dense, and the surface is covered with red soil and river alluvium. The plain along the Yangtze River in Jiangsu and Anhui mainly refers to the long and narrow alluvial plain distributed along the banks of the Yangtze River between Hukou and Zhenjiang, including Wuhu Plain and Chaohu Plain. The width and width of the plain alternate, the river flows in and out, and the velocity is gentle; Since Datong, every time supported by the tide, the flow velocity has slowed down and the sediment deposition has been strengthened. Especially when the river passes through the rock head forced by the rock mound, river branches and sandbars appear between the branches. There are many lakes on both sides of this river. The Yangtze River Delta is developed from the estuary below Zhenjiang.

To the north of the delta is the He Lixia Plain. The plain is a dish-shaped depression with high, middle and low levels in the Zhou Dynasty. The northern edge of the depression is the old course of the Yellow River; The southern margin is the delta on the north bank of the Yangtze River; The west edge is Hongze Lake and Yunxi levee; The eastern edge is the coastal plain of northern Jiangsu. The two lakes and plains are bounded by Jianghan Plain in the north and Dongting Lake Plain in the south. Jianghan Plain is mainly formed by Yangtze River and alluvial sediments. Since the entrance of Jingjiang North dike into Jianghan Plain was completely blocked around 1300, the sediment carried by Hanjiang River has played a major role in the development of Jianghan Plain, and its delta has become an important part of Jianghan Plain. The terrain of the Hanjiang River Delta is also slightly inclined from northwest to southeast, and there are many lakes in the southeast front. Dongting Lake Plain is mainly formed by the Yangtze River sediment flowing southward through Taiping, Ouchi, Songzi and Tiao County (blocked at 1958) on the south bank of Jingjiang River. The area is about 1 1,000 square kilometers. Most of them are below 50 meters above sea level, high in the north and low in the south, with dense water networks and fertile soil. The flood plain in the middle of Poyang Lake Plain is mainly formed by the scouring and silting of rivers such as Jiangxi, Fuzhou, Xinjiang, Poyang Lake and Xiushan, with Jiangxi as the main one. It covers an area of about 20,000 square kilometers. The terrain is low and flat, most of which are below 50 meters above sea level. The water network is dense, and the surface is covered with red soil and river alluvium.

The plain along the Yangtze River in Jiangsu and Anhui mainly refers to the long and narrow alluvial plain distributed along the banks of the Yangtze River between Hukou and Zhenjiang, including Wuhu Plain and Chaohu Plain. The width and width of the plain alternate, the river flows in and out, and the velocity is gentle; Since Datong, every time supported by the tide, the flow velocity has slowed down and the sediment deposition has been strengthened. Especially when the river passes through the rock head forced by the rock mound, river branches and sandbars appear between the branches. There are many lakes along the Yangtze River. According to the causes, there are tectonic lakes and river relic lakes. The Yangtze River Delta is developed from the estuary below Zhenjiang. To the north of the delta is the He Lixia Plain. The plain is a dish-shaped depression with high, middle and low levels in the Zhou Dynasty. The northern edge of the depression is the old course of the Yellow River; The southern margin is the delta on the north bank of the Yangtze River; The west edge is the west dike of He Yun; The eastern edge is the coastal plain of northern Jiangsu.

The plain in the middle and lower reaches of the Yangtze River is mainly formed by alluvial sediment carried by the Yangtze River and its tributaries, with a total area of more than 200,000 square kilometers, most of which are below 50 meters above sea level. There are many ports and lakes in the territory, and it is known as "Water Town and Zeguo". About 20 million to 30 million years ago, the Yangtze River estuary below Zhenjiang was like a trumpet-shaped triangular harbor with a vast water surface and strong tides. Supported by the tide, most of the sediment brought by the Yangtze River is deposited. At first, it piled up into a huge sand embankment on the north and south banks. One on the north shore extends eastward from Yangzhou to Nantong. To the north of this sandbar is the He Lixia Plain, which is mainly formed by alluvial sediments of ancient Huaihe River and Yellow River. A sandbar on the south bank of the Yangtze River extends from Jiangyin to Jinshan Caojing in the southeast, and connects with a sandbar on the north bank of Hangzhou Bay to form an encirclement, which encloses the triangle harbor as a lagoon basically isolated from the sea, but there are still some gaps connected with the sea. This is the ancient Taihu Lake. Later, due to the continuous siltation of the tide flowing backward along the gap of the sand dike and the sediment brought by the rivers in the upper reaches of the ancient Taihu Lake, the land continued to expand, and the ancient Taihu Lake continued to shrink and was divided into many small lakes such as Dianshan Lake and Yangcheng Lake. At the same time, the sediment of the Yangtze River continues to accumulate along the coast, forming a new delta. Now in the west of Shanghai, starting from Jiading Waigang in the north, crossing Maqiao in Shanghai County to Jinshan Caojing, you can also see an intermittent ancient shell sand belt, which was the ancient coastline five or six thousand years ago. The land east of this line is a part of the new delta formed by sediment deposition since 5000 years. Today, the land in Nanhuizui in the east of Shanghai and the eastern end of Chongming Island is still growing.

The annual average temperature in the middle and lower reaches of the Yangtze River14 ~18℃; 1 Monthly average temperature 0 ~ 5.5℃; The average temperature in July is 27 ~ 28℃, and the absolute maximum temperature can reach above 38℃. The annual precipitation 1000 ~ 1500mm is evenly distributed in seasons, but there is a "summer drought". The frost-free period is 2 10 ~ 270 days, and the active accumulated temperature above 10℃ reaches 4500 ~ 5000℃. This area belongs to subtropical monsoon climate, with mild winter and little rain, and high temperature and rainy summer. There is more precipitation in spring and summer. From June to July every year, affected by the summer monsoon and the cold air in the north, "Meiyu" is formed, which lasts for a long time. The length of rainy season is greatly influenced by "quasi-static stop before Jianghuai". After the rainy season, due to the influence of the western Pacific subtropical high, typhoon activity decreased, forming a "summer drought".

In the Yangtze River Delta, rivers intersect, rivers are connected, and the water system is developed. Because of the small water level difference and low flow rate in plain area, the direction of water flow is uncertain due to the height control of water conservancy projects and the influence of gate opening and closing and drainage. Rivers and lakes not only bear the local surface water runoff, but also bear about 2 million km^2 of incoming water in the upstream provinces and regions of 15. In flood years, the Yangtze River Delta is the flood corridor of the upstream water system. Because facing the ocean, it is vulnerable to typhoons, rainstorms and storm surges, and floods caused by waterlogging or waterlogging often occur. In the dry season, the lack of upstream water often leads to serious drought and aggravates the deterioration of water quality in rivers and lakes.

In addition, some rivers have high sediment concentration, siltation and slow river bed gradient. Reservoir sediment deposition makes sediment adsorb pollutants, which intensifies water pollution and increases the difficulty of water resources development and utilization. The Yangtze River Basin is located in the middle of China; The three steps across the east and west, across the landform of China, cover an area of 6.5438+0.8 million square kilometers, and the height drops from 5,400 meters above sea level in Jiangyuan to the sea level in Wusongkou.

The basin has a vast area, complex landform types and large ground elevation difference, including extremely high mountains, high mountains, Zhongshan, low mountains, plateaus, hills, basins and plains.

According to the genetic types of landforms and the principle of zoning step by step, the inland landforms of the basin can be divided into high mountainous areas in the western plateau (the first landform level), low mountainous areas in the middle Zhongshan (the second landform level) and hilly plain areas in the east (the third landform level). The plateau mountainous area to the west of Guangyuan-Ya 'an can be further divided into two secondary geomorphic areas, namely, the shallow hilly area of Jiangyuan Plateau and the alpine canyon area of Jinsha River. The plateau of the former is 4500-5000 meters above sea level, and the peak of the latter is generally 3000-4500 meters. A few are extremely high mountains over 5000 meters, covered by glaciers. The Zhongshan area west of Xiangfan-Yichang-Kaili can be further divided into Qinba Mountain area in the north, Hubei-Guizhou Mountain area in the south and Sichuan Basin in the middle.

The altitude of the first two is about 200 meters, while the latter is below 1000 meters. The eastern hilly plain area can be further divided into northern Huaiyang hilly area, southern Jiangnan hilly area and the middle and lower reaches of the Yangtze River plain area between them. In addition, it can be divided into several third-grade landform areas and fourth-grade landform areas in turn, such as Jianghan Plain, Dongting Lake Plain, Poyang Lake Plain, Chaohu Plain, Yangtze River Delta Plain, Hanzhong Basin, Nanyang Basin, Three Gorges Alpine Canyon and so on.

The whole basin is surrounded by mountains, with Mangkang Mountain in the west, Kunlun Mountain, bayan har Mountain, Qinling Mountain and Dabie Mountain in the north and Wuling Mountain, Wuyishan Mountain and Tianmu Mountain in the south. Mountains, hills and plains coexist in the basin, with mountains and hills accounting for 84.7% and plains accounting for 1 1%. The topography of the basin is stepped down to the east, roughly bounded by Guangyuan-Ya 'an East and Xiangfan-Yichang-Kaili. It is divided into three landforms: west, middle and east. The western part is a plateau mountainous area with an area of 6010.9 million square kilometers. The total terrain decreases to the southeast, which can be divided into two parts: the northern part is a shallow plateau valley area with an altitude of 4500-5000 meters. There is still strong activity in the valley of the original surface in the near future. Earthquakes often occur in large active fault zones along the Yangtze River.

From Yichang, Hubei to Jiangyuan, it is the upper reaches of the Yangtze River, crossing the first and second steps of China geography. The Yangtze River originates from Tanggula Mountain Glacier, and the water system above the mouth of Chumar River in Tongtian River is the source of the Yangtze River. The main stream of the Yangtze River below Yibin, Sichuan is called Jinsha River, and it is called "Yangtze River" after the Minjiang River meets. The main stream of the Yangtze River runs from Minjiang Estuary to Yichang, also known as "Chuanjiang", and runs through the southern margin of Sichuan Basin and Badong Canyon. The main stream of the upper reaches of the Yangtze River is 4529 kilometers long, accounting for more than 70% of the total length of the Yangtze River.

The main channel in the middle reaches of the Yangtze River is from Yichang City, Hubei Province to Hukou City, Jiujiang City, Jiangxi Province, including Yidu City, Hubei Province to Chenglingji, Dongting Hukou City, Yueyang City, Hunan Province. Because the Yangtze River flows through the ancient Jingzhou area, it is also called Jingjiang. Jingjiang River has slow twists and turns, more sediment deposition, rising riverbed, and the flood level can reach 10 meters above the ground. It is the most easily flooded section of the Yangtze River, and there is a saying that "a long river travels a thousand miles, and the danger lies in Jingjiang River". In order to reduce the threat of flood, Jingjiang flood diversion project and bend straight project were built.

Wuhan along the middle reaches of the Yangtze River is the largest city in Central China and the center of industry, finance, commerce, science and technology, culture and education in Central China.

The Yangtze River flows downstream from the mouth of Jiujiang Lake in Jiangxi Province to the mouth of the Yangtze River, and the section that passes through Jiujiang and enters Anhui Province is also called "Wanjiang". It generally flows northeast until Nanjing, Jiangsu Province, and then turns eastward to Zhenjiang and Yangzhou, so the vast area on the right bank of this section has been called Jiangdong since ancient times. This section of the river meanders between the hills in southern Anhui, central Anhui and Ningzhen and the north shore plain. There are often stony rocks near the river on the right bank, and the riverbed is narrow first and then wide, forming a lotus-shaped riverbed with alternating width and width. The reach below Datong in Tongling is affected by tides, with gentle water potential and bare sandbars. The main tributaries are Qingyi River-Shuiyangjiang River, Chuhe River and Qinhuai River.

The length of the Yangtze River from Zhenjiang to the mouth of the Yangtze River is about 3 12 km. This section of the river that is about to enter the sea is also known as the "Yangtze River" because of the Yangtze River ferry in ancient times. The river below Jiangyin is also called the estuary section. The river near Jiangyin is only1.200m wide, and it widens like a trumpet to the east. The Yangtze estuary is 9 1km wide. The Beijing-Hangzhou Canal intersects the Yangtze River in Yangzhou and Zhenjiang, and 80-90% of the water in the Huaihe River flows into the north bank of the Yangtze River through the Beijing-Hangzhou Canal. Taihu Lake in the south of the Yangtze River is the third largest freshwater lake in China, with dense river networks, forming a huge irrigation system and inland waterway network. Except a small amount of lake water flows into the Yangtze River through some rivers in Jiangyin and Taicang, most of the water flows eastward through Huangpu River, the last important tributary of the Yangtze River.

The Yangtze River carries about 486 million tons of sediment into the sea every year. The western end of the Yangtze River Delta is formed with Zhenjiang and Yangzhou as its vertices, Toarey Yang Canal in the north, Hangzhou Bay in the south and Damaoshan and Tianmu Mountain in the southwest, including parts of Jiangsu and Zhejiang provinces and the whole of Shanghai, covering an area of 40,000 square kilometers. This is a vast plain, and only a few hills stand on the plain like islands. Here, the coastline is straight, the sea water is muddy with yellow sand, and there is an intertidal shoal about several kilometers to dozens of kilometers wide. Since Holocene, the delta has pushed about 40 meters to the sea every year.

There are two central cities in the lower reaches of the Yangtze River: Shanghai, the largest national central city in China, and Nanjing, the fourth regional central city in the Yangtze River basin.

There are many rapids in the upper reaches between the source of the Yangtze River and Yichang City, Hubei Province. Yichang to Hukou County in Jiangxi Province is the middle reaches, with meandering development and numerous lakes (Poyang Lake is the largest, followed by Dongting Lake). From the mouth of the lake to the mouth of the sea, it is downstream, with a wide river and Chongming Island formed by accumulated water in the estuary. The Yangtze River is rich in water resources. During the flood season, 10,000 tons of steamboats can reach Wuhan, and small steamboats can be traced back to Yibin. The Yangtze River Basin is the most densely populated and economically prosperous area in China.

The middle and lower reaches of the Yangtze River are located on both sides of the Yangtze River and its tributaries east of Wushan, and are divided into four parts by the surrounding low hills (see Jiangnan hills): the two lakes plain, the Poyang Lake plain, the central Anhui plain and the Yangtze River Delta, with an area of 300,000 square kilometers and an altitude of less than 50 meters. The Yangtze River Delta includes the areas east of Zhenjiang, Jiangsu, north of Qiantang River and Hangzhou Bay, and south of Toarey Yang Canal, covering an area of about 50,000 square kilometers, with most areas below 10 meters above sea level. Known as "Water Town Zeguo", it is one of the most densely populated areas in China. The climate in this area is the north subtropical monsoon climate, with frequent droughts and floods since ancient times.

The Yangtze River has a large amount of water. Even upstream, the average flow rate exceeds 65,438+0,982 cubic meters per second (70,000 cubic feet per second). After the confluence of Yalong River, a tributary, the flow of the Yangtze River increased sharply, reaching an average of 5,493 cubic meters per second (194,000 cubic feet per second). Further downstream, the Yangtze River receives many tributaries, and its flow gradually increases, reaching 14980 cubic meters per second (529000 cubic feet per second) at the end of the Three Gorges near Yichang, 23984 cubic meters per second (847000 cubic feet per second) near Hankou and 3 1 near Nanjing. The average discharge of the Yangtze River estuary is about 33,980m3/s (1.200 million m3/s), and the total amount of water injected into the sea every year is 1.072 m3/s(244 m3/s), making the Yangtze River the third largest river in the world.

China Yangtze River and Qiantang River are alluvial deltas where they enter the sea. Include Jiangsu province, southeastern Shanghai and northeastern Zhejiang. It is a part of the middle and lower reaches of the Yangtze River. It covers an area of about 50,000 square kilometers.

The apex of the delta is in Zhenjiang and Yangzhou, and the north reaches Xiaoyangkou. South bank of Hangzhou Bay. The elevation is mostly below10m, and the low hills (such as Huishan, Tianpingshan, Yushan and Langshan) are scattered, with an elevation of 200-300m. The annual sediment discharge of the Yangtze River is 400-900 million tons. In general, 28% of the sediment is deposited in the Yangtze River, and in some years it is as high as 78%. The delta continues to extend to the sea. The ancient sand mouths in Changzhou, Changshu, Taicang, Jinshan and other counties south of the Yangtze River are mostly 4 ~ 6 meters above sea level; The ancient sand mouth in Yangzhou, Taizhou, Taixing and Rugao, north of the Yangtze River, is 7-8 meters above sea level.

The ancient sand mouths in Jiangnan and Jiangbei developed gradually after the highest sea level stabilized in the late glacial period. By about 2000, the north bank sand mouth extended to Liaojiaozui, and the south bank sand mouth extended to the southeast with the mainstream of the Yangtze River and connected with the mouth sand mouth of Qiantang River. Sediment continues to accumulate, advancing annually 1958 ~ 1973. It belongs to the northern subtropical monsoon climate, with abundant rainfall, criss-crossing waterways and dotted lakes, and is known as a water town and a country. The land is fertile, and agriculture mainly produces rice, cotton, wheat, rape, peanuts, silk, fish and shrimp. It is one of the most densely populated areas in China. There are many important towns in the lower reaches of the Yangtze River and on both sides of the Shanghai-Nanjing line, such as Shanghai, Suzhou, Changzhou, Wuxi, Zhenjiang, Yangzhou, Taizhou and Nantong. Among them, Shanghai is the largest industrial and commercial city in China and a world-famous foreign trade port, while Suzhou and Wuxi are scenic spots and emerging industrial cities.

In the upper reaches of the Yangtze River, except Chengdu Plain, there are the Three Gorges area in the east, Ganzi and Aba in the northwest, and the ruins of the Anning River and Yalong River basins in the southwest. According to preliminary statistics, there are dozens of sites, the most famous of which is Wushan Daxi Cultural Site. After 1959 and 1975 excavations, a total of 265,438 tombs were excavated. Pots, cans, cups, bowls and other household utensils, as well as earrings and ornaments, represent three different stages of development from the middle to the late Neolithic age.

Neolithic sites in the middle reaches of the Yangtze River are almost all over Jianghan area, especially Jianghan Plain. More than 450 Neolithic sites have been discovered in Hubei alone, and more than 60 sites have been excavated, mostly in Jianghan Plain where the middle and lower reaches of the Han River meet the middle reaches of the Yangtze River. Qujialing culture has three stages of cultural characteristics: early, middle and late, characterized by small painted pottery as thin as eggshells, painted pottery spinning wheels and cross beans. A large number of rice and animal remains have also been unearthed, and animal husbandry has developed accordingly. The species of animals raised have increased, and fisheries have been established. This culture has a wide influence.

Located in the middle reaches of the Yangtze River, Jiangxi Wannian Xianren Cave and Diaotonghuan site have complete and clear stratigraphic accumulation from the late Paleolithic to the early Neolithic. Especially in the 1990s, Sino-US cooperative agricultural archaeology discovered rice planting silica 6,543,800 years ago in the early Neolithic strata of the site, which advanced the world rice planting history by 6,543,800 years and became one of the earliest known rice planting origins in the world. At the same time, a large number of primitive pottery pieces developed in order 17000 years ago were found in this stratum, which is the earliest known birthplace of primitive pottery in the world.

The Neolithic cultural sequence in the lower reaches of the Yangtze River can be represented by Hemudu culture, Majiabang culture and Liangzhu culture. Hemudu Cultural Site in Yuyao, Zhejiang Province, near Hangzhou Bay, found at 1973. It was excavated twice. Among about 7,000 precious cultural relics unearthed, there are piles of rice and rice husk remains, and a large number of "bones" have been unearthed, which proves that it has left the "fire farming" and began to dig the ground with bones. Large-scale wooden structures have also been unearthed, with mortises and tenons, which is the earliest known "dry-column" wooden structure.