Geographical location and scope
The administrative area includes 2/kloc-0 counties (cities) belonging to Jiamusi City, hegang City, Shuangyashan City, qitaihe city City and Jixi City, and yilan county City belonging to Harbin City. There are 52 state-owned farms and 8 forest industry bureaus in China. The total area is about108900 square kilometers, the total population is 8.625 million, and the population density is about 79 people/square kilometers.
It is between 45 01′ ~ 48 27 ′ 56 ″ north latitude and 0/3013 ′ ~135 05 ′ 26 ″ east longitude. Located in the northeast corner of China, it starts from the southeast end of Xiaoxing 'anling in the west, reaches Wusuli River in the east, reaches Xingkai Lake in the north and reaches Xingkai Lake in the south, with a total area of 5.130,000 square kilometers. North-south part
The Wanda Mountain Range divides the Sanjiang Plain into two parts: the northern part of the mountain is a swampy low plain formed by the confluence of Songhua River, Heilongjiang River and Wusuli River, covering an area of 42,500 square kilometers, which is the narrow Sanjiang Plain; Shannan is an alluvial-lacustrine marshy low plain formed by Wusuli River and its tributaries and Xingkai Lake, with an area of 8,800 square kilometers, also known as Muling-Xingkai Plain.
Sanjiang Plain in a narrow sense is a part of the intermountain basin in the middle reaches of Heilongjiang, surrounded by mountains on three sides, with Qingheishan, a branch of Xiaoxing 'an Mountains, a branch of Wandashan Mountain in the south and Nadanhadaling, a main branch of Wandashan Mountain in the east, which belongs to the Mesozoic-Cenozoic inland fault depression. There are Mesozoic and Cenozoic sedimentary caprocks piled up on the composite folded basement, and the thickness of Quaternary system is generally120 ~ 200m, and the maximum thickness can reach 280m. In addition to the cohesive soil layer with a thickness of 3 ~17m on the eastern surface, it is mainly alluvial sand and gravel, making it a porous aquifer rich in groundwater. It is 45-60m above sea level, and the lowest in Fuyuan Delta is only 34m. It slopes slowly from southwest to northeast, with a total gradient of about 0. 10‰. The river meanders on the broad floodplain. The main landform types are terraces and floodplains, with skirt-shaped alluvial and diluvial inclined plains along the western and southern edges, and the transition between different types is slow. The ground fluctuation of the same type is generally only 0.5 ~ 2 meters, and only a few isolated hills are seen on the plains, with disc-shaped and linear shallow depressions widely distributed, and the cutting is weak. Except for Heilongjiang, Songhua River and Wusuli River, all small and medium-sized rivers are plain swamp rivers, and most of them are covered by swamp vegetation.
Muling-Xingkai Plain is bordered by the southern foot of Wanda Mountain in the north and Kent Aling in the west. Quaternary sediments in this area are mainly alluvial, lacustrine sand and gravel, with a thickness of10 ~150m, and a clayey soil cover with a thickness of1~ 4m on the surface. At an altitude of 55-95m, the north and west are undulating with a height difference of10-20m. The general terrain is inclined from west to east with a slope drop of 0.6-0.1‰. The beaches of Muling River and lakeside are wide and the ground is generally swampy.
climate
Sanjiang Plain belongs to temperate humid and semi-humid continental monsoon climate, with annual sunshine hours of 2400 ~ 2500 hours, 1 monthly average temperature of-21~-18℃, average temperature of 21~ 22℃ in July and frost-free period of1. The freezing period is as long as 7 ~ 8 months, and the maximum freezing depth is1.5 ~ 2.1m. The annual precipitation is 500 ~ 650 mm, and 75 ~ 85% is concentrated in June ~1October.
geomorphology
The vast and flat landform of Sanjiang Plain, the cold and humid climate with concentrated precipitation in summer and autumn, the slow runoff, the rivers with sudden flood peaks, and the sticky soil with seasonal freezing and thawing make the surface too wet for a long time and accumulate too much water, forming a large area of swamp water and swampy vegetation and soil, which constitutes a unique swamp landscape. Swamp and swampy land covers an area of about 2.4 million hectares, which is the largest swamp distribution area in China. Hydrophytes and marsh plants mainly include Calophyllum angustifolia, marsh willow, Carex and reed. Among them, Carex bog is the most widely distributed, accounting for about 85% of the total swamp area, followed by reed swamp. Soil types mainly include black soil, albic soil, meadow soil and swamp soil, among which meadow soil and swamp soil are the most widely distributed. Sanjiang Plain is known as the "Great Northern Wilderness". Before the large-scale reclamation in the 1950s, meadows and swamps were boundless, and there were also patches of forests and many wild animals. After reclamation, many large state-owned farms have been built, and the "Great Northern Wilderness" has become a "Great Northern Warehouse" and an important commodity grain base in the country.
environmental aspect
At present, the environmental conditions in the Sanjiang Plain remain good, and the air quality in the vast forest areas, rural areas and most farms is clean. The natural water quality is good except for some river sections. The natural swamp wetland covers an area of1347,000 hectares, which is an important habitat and breeding ground for rare waterfowl. Six national wetland nature reserves have been built, three of which are listed in the list of internationally important wetlands, and the endangered waterfowl protected are red-crowned cranes and swans.
harvest
The harvest season in Sanjiang Plain is the most desirable. In the vast fields, the channels are criss-crossing, the agricultural machinery is roaring, the rice flowers are fragrant, and the wheat waves are rolling. Modern farms leading the national mechanization level are full of vitality, busy and prosperous. The Sanjiang Plain in winter is quiet and leisurely. How long the winter is, how long the slack season is. In this land where countless educated youths have devoted their youth and sweat, there are 10 counties and cities along the Yangtze River open to Northeast Asia as first-class ports, and ordinary people who live comfortably and peacefully begin to dream of a better future ...
One of the top ten "New Tianfu"
Sanjiang Plain was selected as one of the top ten "New Abundances" in China by China National Geographic magazine.
The ranking of the top ten "New Tianfu" is: Chengdu Plain, Taiwan Province Jianan Plain, Yili River Valley, Shandong Peninsula, Minnan Hilly Plain, Sanjiang Plain, Yarlung Zangbo great bend Region, Hulunbeier, Subei Plain and Ningxia Plain. The annual output of grain in Sanjiang Plain is15 million tons, and the per capita cultivated land area and per capita grain output are more than four times the national average. The scale of agricultural production here is huge, and the degree of agricultural mechanization ranks first in the country. At the same time, the regional environment is beautiful and the pollution is very small. The shrinking trend of wetland area in Sanjiang Plain has been obviously curbed, and the number of wetland nature reserves above the municipal level has reached 10, which has attracted the attention and support of international ecological and environmental protection organizations.
North China Plain
China's second largest plain. Located in the lower reaches of the Yellow River. It starts from Taihang Mountain and western Henan Mountain in the west, reaches the Yellow Sea, Bohai Sea and Shandong Hill in the east, starts from Yanshan Mountain in the north, reaches Tongbai Mountain and Dabie Mountain in the southwest, and reaches northern Jiangsu and Anhui in the southeast, connecting with the plain in the middle and lower reaches of the Yangtze River. It extends to the territory of seven provinces and cities including Beijing, Tianjin, Hebei, Shandong, Henan, Anhui and Jiangsu. It covers an area of about 300,000 square kilometers. Mainly from the Yellow River, Huaihe River, Haihe River, Luanhe River alluvial, so it is also called Huanghuaihai Plain. The lower reaches of the Yellow River naturally cross the central part and are divided into two parts: the Huanghuai Plain in the south and the Haihe Plain in the north. Over the past century, the Yellow River has reclaimed land here with an area of 2,300 square kilometers. The plain continues to extend to the ocean, the fastest is the Yellow River Delta, with an average of 2 ~ 3 kilometers per year. The terrain is low and flat, most of which are below 50 meters above sea level, and the eastern coastal plain is below 10 meters above sea level. Slightly inclined from west to east. It mainly belongs to the Cenozoic giant depression, with a sedimentary thickness of1500 ~ 5000m. There are many low-lying areas and lakes and marshes in the plain. Concentrated distribution in the north of the Yellow River alluvial fan between Baoding and Tianjin Dagu. The contact between the eastern edge of alluvial fan and Shandong hills has poor drainage and high groundwater level, which is easily threatened by flood waterlogging and forms saline-alkali land. 1949 years later, it was reformed and treated. It has a warm temperate monsoon climate with obvious changes in four seasons. The Huaihe river basin in the south is in the transition area to subtropical zone, and its temperature and precipitation are higher than those in the north. The average annual temperature in the plain is 8 ~ 1 5℃, the winter is cold and dry, the average temperature in Leng Yue (1month) is 0 ~-6℃, the average temperature in the hottest month (July) in summer is 28℃, and the average annual precipitation is 600 ~ 800 mm; Frost-free period is 6 ~ 8 months; There is plenty of sunshine, and the average sunshine hours in most years are 2300 ~ 2800 hours. Most crops are cropped three times in two years and twice a year in the south. The soil layer is deep and fertile. The main food crops are wheat, rice, corn, sorghum, millet and sweet potato, and the cash crops are mainly cotton, peanuts, sesame seeds, soybeans and tobacco. Rich in mineral resources, such as coal, oil, iron ore, China's famous Dagang Oilfield and Shengli Oilfield. The eastern coast of Bohai Sea and Yellow Sea is flat and suitable for drying sea salt. There are famous Changlu salt area and northern Jiangsu salt area, as well as important saline-alkali industrial base. North China Plain is the cradle of ancient culture in China, and there are many ancient cities, such as Beijing (Ji), Handan, Kaifeng, Shangqiu and Huaiyang.
Plains of the Middle and Lower Reaches of the Yangtze River
The banded plain along the middle and lower reaches east of the Three Gorges of Yangtze River in China. It is bounded by Huaiyang Mountain in the north and Jiangnan hills in the south. The terrain is low and flat, and the ground height is mostly below 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 Anhui Yangtze River coastal plain and Chaohu Plain, and the Yangtze River Delta between Jiangsu, Zhejiang and Shanghai, in which the ground height of the Yangtze River Delta is below 10 meter. Rivers and branches crisscross the plain, and lakes are dotted. The famous freshwater lakes such as Dongting Lake, Poyang Lake, Taihu Lake, gaoyou lake, Chaohu Lake and Hongze Lake are all distributed in this narrow strip. Known as the "Water Town and Zeguo", Xiang is rich in fish, shrimp, crab, water chestnut, lotus and reed. Mild climate, frost-free period 240? In 280 days, double-cropping rice can be planted in the south of the Yangtze River, and grain, cotton and aquatic products occupy an important position in the country, which is known as the "land of fish and rice". The middle and lower reaches of the Yangtze River are economically developed, including Shanghai, Nanjing, Wuhan and other big cities and medium-sized cities such as Suzhou, Wuxi, Changzhou, Zhenjiang, Yangzhou, Taizhou, Nantong, Wuhu, Nanchang and Changsha.
The banded plain along the middle and lower reaches east of the Three Gorges of Yangtze River in China. Huaiyang Hill and Huanghuai Plain in the north, Jiangnan Hill and Zhejiang-Fujian Hill in the south. It is alluvial from the Yangtze River and its tributaries. The area is 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 plains along the Yangtze River in Anhui and Chaohu Plain (the central plain of Anhui), as well as 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 margin of the middle subtropical zone. Average annual temperature14 ~18℃, coldest average monthly temperature 0 ~ 5.5℃, absolute minimum temperature-10 ~-20℃, hottest average monthly temperature 27 ~ 28℃, frost-free period 210 ~ 270 days. Agriculture crops twice or three times a year, and the annual precipitation is1000 ~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 scattered all over the place. The lake area is 20,000 square kilometers, which is equivalent to the plain area10%. On the two lakes plain, there are more than 1300 large lakes, including small lakes, with an area of 1 10,000 square kilometers, accounting for more than 20% of the area of the two lakes plain, 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 function of regulating water volume and reducing flood peak. They produce fish, shrimp, crab, lotus, ling and reed, as well as world treasures such as Chinese sturgeon, Chinese alligator and baiji. Aquatic products occupy an important position in China, and are known as the land of fish and rice. It is one of the most economically developed areas, including Shanghai, Nanjing, Wuhan, Nanchang, Suzhou, Wuxi, Changzhou, Zhenjiang, Yangzhou, Taizhou, Nantong, Wuhu and Changsha.
The main industries are steel, machinery, electric power, textile 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 well-developed land and water transportation. The Yangtze River runs through the central part, becoming an east-west waterway artery, and its numerous tributaries form a huge waterway network.
The plain in the middle and lower reaches of the Yangtze River is alluvial by the Yangtze River and its tributaries, east of the Three Gorges, south of Huaiyang Mountain and Huanghuai Plain, north of Jiangnan Hilly and Fujian-Zhejiang Hilly. It spans six provinces of Jiangxi, Hubei, Hunan, Anhui, Jiangsu and Zhejiang and is one of the three major plains in China. It includes four parts: the two lakes plain, Poyang Lake plain, the central Anhui plain and the Yangtze River Delta. The middle reaches plain area is relatively wide. The plains in the lower reaches of the Yangtze River are long and narrow in shape. The terrain here is flat, the rivers are curved, and the lakes are densely covered. It is known as the "Water Town Zeguo" and is the main agricultural area in China. Poyang Lake, Dongting Lake, Taihu Lake, Hongze Lake and Chaohu Lake on the plains are the five famous freshwater lakes in China.
form
The plain in the middle and lower reaches of the Yangtze River is one of the three major plains in China. Located along the middle and lower reaches of the Yangtze River to the east of Yichang, Hubei, it consists of two lakes (Jianghan Plain in Hubei and Dongting Lake Plain in Hunan), Poyang Lake Plain, Jiangsu-Anhui Riverside Plain, Lixiahe Plain (Central Anhui Plain) and Yangtze River Delta Plain, covering an area of about 200,000 square kilometers.
(1) The two lakes plain includes the northern part of Hunan and the southern part of Hubei. In ancient times, it used to be a misty cloud and dream, but it was later filled by the sediment washed down by the Yangtze River and its tributaries. It covers an area of 50,000 square kilometers and is divided into Jianghan Plain and Dongting Lake Plain. The plain is densely covered with water nets and is called "the land of fish and rice".
(2) Poyang Lake Plain is located in the northwest of Jiangxi to the southwest edge of Anhui, covering an area of 20,000 square kilometers. The terrain is low and flat, and the altitude is below 50 meters.
(3) The Central Anhui Plain is located along the Yangtze River in central Anhui and near Chaohu Lake, with a small area.
(4) The Yangtze River Delta is located to the east of Zhenjiang, to the south of the Canal and to the north of Hangzhou Bay, covering an area of 50,000 square kilometers. It is alluvial by the Yangtze River and Qiantang River, and the elevation here is only about 10 meter. On the delta, rivers criss-cross and lakes are scattered all over, which is known as "the country of water and land". Here is rich in rice, fish and shrimp, and the grain output occupies an important position in the country. In history, there was a saying that "Suzhou and Shanghai are ripe, and the world is full".
The plain in the middle and lower reaches of the Yangtze River lies on both sides of the Yangtze River and its tributaries to the east of Wushan, and is divided into four parts by the surrounding low hills (see Jiangnan hills): the two lakes plain, the Poyang 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 Tongyang Canal, covering an area of about 50,000 square kilometers, and its elevation is mostly below 10. It is known as the "Water Town and Zeguo" and 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 Yangtze River and Han River. Since the entrance of Jingjiang River north dike was completely blocked around A.D. 1300, the sediment carried by Han 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 Hanjiang Delta is also slightly inclined from northwest to southeast, and lakes are crowded in the southeast front. Dongting Lake Plain is mainly formed by the sediment from the Yangtze River that flows southward through the four ports of Taiping, Ouchi, Songzi and Tiaoxian (blocked by 1958) on the south bank of Jingjiang River. The area is about 1 10,000 square kilometers. Most of them are below 50 meters above sea level, with high terrain in the north and low terrain in the south, dense water networks and fertile soil. In addition to the marginal red earth mounds, the flood plain in the central part of Poyang Lake Plain is mainly formed by the scouring and silting of rivers such as Jiangxi, Fuzhou, Xinjiang, Poyang Lake and Xiushan, among which the Ganjiang River is the main one. It covers an area of about 20,000 square kilometers. The terrain is low and flat, most of them are below 50 meters above sea level, and 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 plains are wide and narrow alternately, and the river flows in and out, with a gentle velocity; Since Datong, every time it is supported by the tide, the flow velocity is slower and the sediment deposition is strengthened. Especially when the river passes over the rocky head which is forced by the rocky mound, the river branches and sandbars appear between the branches. There are many lakes on both sides of the river.
The Yangtze River Delta has developed from the estuary below Zhenjiang. To the north of the delta is Lixiahe Plain. The plain is a dish-shaped depression with high, middle and low levels in Zhou Dynasty. The northern edge of the depression is the old course of the Yellow River; The southern margin is the north bank of the Yangtze River in the delta; The west edge is Hongze Lake and Yunxi levee; The eastern edge is the coastal plain of northern Jiangsu.
geomorphology
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 the Yangtze River and alluvial deposits. Since the entrance of Jingjiang River north dike flowing into Jianghan Plain was completely blocked around A.D. 1300, the sediment carried by Hanjiang River played a major role in the development of Jianghan Plain, and its delta became an important part of Jianghan Plain. The terrain of Hanjiang Delta is also slightly inclined from northwest to southeast, and lakes are crowded in the southeast front. Dongting Lake Plain is mainly formed by the sediment from the Yangtze River that flows southward through the four ports of Taiping, Ouchi, Songzi and Tiaoxian (blocked by 1958) on the south bank of Jingjiang River. The area is about 1 10,000 square kilometers. Most of them are below 50 meters above sea level, with high terrain in the north and low terrain in the south, dense water networks and fertile soil.
In addition to the marginal red earth mounds, the flood plain in the central part of Poyang Lake Plain is mainly formed by the scouring and silting of rivers such as Jiangxi, Fuzhou, Xinjiang, Poyang Lake and Xiushan, among which the main one is Jiangxi. It covers an area of about 20,000 square kilometers. The terrain is low and flat, most of them are below 50 meters above sea level, and 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 plains are wide and narrow alternately, and the river flows in and out, with a gentle velocity; Since Datong, every time it is supported by the tide, the flow velocity is slower and the sediment deposition is strengthened. Especially when the river passes over the rocky head which is forced by the rocky mound, the river branches and sandbars appear between the branches. There are many lakes along the banks of the Yangtze River. According to their causes, there are tectonic lakes and river trace lakes.
The Yangtze River Delta has developed from the estuary below Zhenjiang. To the north of the delta is Lixiahe Plain. The plain is a dish-shaped depression with high, middle and low levels in Zhou Dynasty. The northern edge of the depression is the old course of the Yellow River; The southern margin is the north bank of the Yangtze River in the delta; The west edge is the Heyun West Embankment; The eastern edge is the coastal plain of northern Jiangsu.
terrain
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 numerous ports and lakes in the territory, and it is known as the "Water Town and Zeguo". About 20 to 30 million years ago, the mouth of the Yangtze River below Zhenjiang was still like a trumpet-shaped triangular harbor with a vast surface and strong tides. Under the support of the tide, most of the sediment brought by the Yangtze River was deposited. At first, it piled up into a huge sand dike on the north and south banks.
One on the north shore extends eastward from Yangzhou to Nantong. To the north of this sandbank is the Lixiahe Plain, which is mainly formed by the alluvial sediment from the ancient Huaihe River and the Yellow River. A sandbank on the south bank of the Yangtze River extends southeast from Jiangyin to Caojing in Jinshan, and connects with a sandbank on the north bank of Hangzhou Bay to form an encirclement, enclosing the triangular harbor into a lagoon which is basically separated from the sea, but there are still some gaps communicating with the sea. This is the ancient Taihu Lake. Later, due to the continuous deposition of tidal water flowing backward along the gap of sand embankment and the sediment brought by the rivers in the upper reaches of ancient Taihu Lake, the land continued to expand, and the ancient Taihu Lake was shrinking and 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 to form a new delta.
Nowadays, in the west of Shanghai, starting from Waigang in Jiading in the north, passing Maqiao in Shanghai County to Caojing in Jinshan, you can also see an intermittent ancient shell sand belt, which is the ancient coastline five or six thousand years ago. The land to the 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 average annual temperature in the middle and lower reaches of the Yangtze River is14 ~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 is1000 ~1500mm, which is evenly distributed in seasons, but there is a "summer drought". The frost-free period is 210 ~ 270 days, and the active accumulated temperature above 10℃ reaches 4500 ~ 5000℃. Crops can be harvested twice a year, and the triple cropping system of double cropping rice can be developed in the south of the Yangtze River. The plain in the middle and lower reaches of the Yangtze River is an important production base of grain, oil and cotton in China, and it is also the region with the richest water resources in China. The natural water system of the Yangtze River and criss-crossing artificial canals make this area the densest river network in China. This area is the most concentrated area of freshwater lakes in China. The famous freshwater lakes are Poyang Lake, Dongting Lake and Chaohu Lake. The lake and marsh area is rich in aquatic biological resources, which is the most widely distributed and productive area of aquatic plants in China. Freshwater aquatic animals are also the highest in China, except for static water, bream, bream, silver carp, carp, crucian carp, green grass, and many kinds of migratory fish in the estuary, mainly silver carp, bream, fragrant fish, whitebait (including whitebait and whitebait) As for Chinese sturgeon, Chinese alligator and baiji, they are even more world treasures.
Distribution of traditional Chinese medicine resources
The plains in the middle and lower reaches of the Yangtze River are mainly composed of low hills, basins, lake depressions and coastal beaches, including Jianghan Plain, Dongting Lake Plain, Poyang Lake Plain, Jiangsu-Anhui Plain along the Yangtze River, Yangtze River Delta and Lixiahe Plain. There are many lakes on the plain, and rivers and lakes are connected in series. The vast alluvial plains and basins have deep and fertile soil, which provides good growth conditions for domestic and wild medicinal organisms. In terms of climate conditions, there are some differences between Jiangnan and Jiangbei: the temperature in Jiangnan is slightly higher than that in Jiangbei in winter, and Jiangnan has obvious subtropical characteristics, while Jiangbei has a climate characteristic of transition to warm temperate zone.
(1) Types of Common Medicinal Materials
There are some important and commonly used medicinal materials distributed in this area, which can be supplied to the whole country and exported. Among them, the wild herbs with high yield and good quality include Smilax glabra, motherwort, Radix Codonopsis, Radix Puerariae, Polygonum Cuspidatum, Prunella vulgaris, Peucedanum praeruptorum, Linderae, Flos Chrysanthemi Indici, Sanguisorba officinalis, Herba Artemisiae Scopariae, Polygonum Multiflori Radix, Fructus Ligustri Lucidi, Radix Adenophorae, Stemonae, Fructus Trichosanthis, Radix Platycodi, Radix Salviae Miltiorrhizae, Fructus Arctii, Herba Epimedii, Rhizoma Cynanchi, and Herba Hedyotidis Diff Trees include Cinnamomum camphora, Ligustrum lucidum, Ilex pubescens, Ilex cornuta, Liquidambar formosana, Platanus acerifolia, Albizia Albizia, Mume Fructus, Zizyphus jujuba, etc. Shrubs include raspberry, beech, Rosa laevigata, hibiscus mutabilis, palm, mountain pepper, frozen green, wild hawthorn and so on; The cultivated medicinal materials include Eucommia ulmoides, Magnolia officinalis, Cornus officinalis, Pinellia ternata, Radix Isatidis, Carthami Flos, Fructus Psoraleae, Radix Platycodi, etc.
(2) Aquatic medicinal plants
The middle and lower reaches of the Yangtze River have the eastern plain of China, which is also the area with the highest lake density in China. The five famous freshwater lakes in China-Dongting Lake, Poyang Lake, Taihu Lake, Hongze Lake and Chaohu Lake are all located here. This area is close to the ocean, located in the southeast Asian monsoon belt, with warm and humid climate, abundant precipitation, large area and many kinds of aquatic vegetation in the lake area. In the lake, aquatic medicinal plants are distributed in a regular ring from shallow coastal water to deep central water, followed by emergent plants, floating plants and submerged plants. Emergent aquatic plants refer to the species whose roots are rooted in the mud at the bottom of the water, and whose upper parts or Ye Ting are born on the water surface. They are mostly distributed in shallow water, shallow ponds, gullies and paddy fields in inner lakes. The main medicinal species are reed, water candle, Typha orientalis, lotus, water chestnut, arrowhead, Alisma orientalis, Sparganum burmannii, Acorus calamus, Acorus gramineus, Allium fistulosum, and Yujiu. Most of them are distributed in still water areas such as lake edge, ponds and gullies. The main medicinal species are Euryale ferox, Trapa natans, Wild Trapa natans, Duckweed, Azolla, Manjianghong, Ye Ping, Eichhornia crassipes, Alternanthera philoxeroides, water shield, water lily, Eupatorium adenophorum, water fern, Polypodia and so on. The main medicinal species are POTAMOGETON POTAMOGETON, POTAMOGETON POTAMOGETON, Ceratophyllum japonicum, Sargassum japonicum, Sophora alopecuroides, etc., and there are also aquatic medicinal species, such as Juncus efflorescence, Pennisetum, Sagittaria sagittatum, Cynanchum rotundifolia, Amaranthus syringae, and Oenanthe javanica. The important cultivated medicinal materials in the lake area are Euryale ferox, Alisma orientalis, and water chestnut, water chestnut, lotus, water spinach and so on.
(3) Animal medicinal materials
Animal medicinal materials in this area include pearls, mother-of-pearl, toad venom, earthworm, hedgehog skin, Eupolyphaga Seu Steleophaga, Carapax Trionycis, Tortoise Shell, Bombyx Batryticatus, Periostracum Cicadae, Hirudo, Endothelium Corneum Gigeriae Galli, Scolopendra, Concha Ostreae, Nymphaea, tabanus, grub, dung beetle, dung beetle and so on. There are Agkistrodon, Zaocys, Agkistrodon, Pangolin, Otter, Leopard, Monkey, Deer, Bear and Civet in the mountainous area.
(4) Mineral medicinal materials
There are not many kinds of mineral drugs, mainly fluorite, magnetite, talc, purple Shi Ying, Qiu Shi, Anonymous, Halloysitum rubrum, Lapis chlorite, Daiheshi, mirabilite, native copper, actinolite, mica, Halloysitum rubrum, Yuliang stone, amber, Eguanshi and gypsum.
Present situation of water environment
(1) Water environment characteristics of the Yangtze River Delta
The geographical range of the Yangtze River Delta region is between 28 45' and 33 25' north latitude and118 20'-kloc-0/23 25' east longitude, and its administrative regions include Shanghai, Nanjing, Hangzhou, Zhenjiang, Yangzhou, Taizhou, Nantong, Suzhou and Wuxi. The total land area of the Yangtze River Delta is 99,600 km^2, accounting for about1%of the national land area. The total population of the whole region is about 7 404.7110,000, accounting for 6.05% of the total population in China. The Yangtze River Delta is adjacent to the ocean in the east, with low and flat terrain, woven river networks and numerous lakes. Its water systems include the Yangtze River estuary, Taihu Lake, Canal, Qiantang River and Yongjiang River, which constitute the unique delta water system of the water town Zeguo.
The main lake in the Yangtze River Delta is Taihu Lake, which is the third largest fresh water lake in China. There are more than 220 rivers around the lake, including more than 70 human lakes, and more than 50 out of the lake/kloc-0, with a storage capacity of 4.67 billion m 3.
In the Yangtze River Delta, rivers and canals intersect, rivers are connected, and the water system is developed. Due to the small water level difference and low flow rate in plain area, the water flow direction 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 the incoming water in the upstream 15 provinces and regions with an area of about 2 million km^2. In the flood year, the Yangtze River Delta is the flood corridor of the upstream water systems. Because it faces the ocean, it is vulnerable to typhoon, rainstorm and storm surge, and there are often floods caused by external flood, waterlogging or external waterlogging. In dry season, the lack of upstream water often causes severe drought and aggravates the deterioration of water quality in rivers and lakes. In addition, in some rivers, the sediment concentration is high, the river channel is silted up, and the river bed slope decreases slowly. The sediment deposition in the reservoir makes the sediment adsorb pollutants, which aggravates the pollution of the water environment and increases the difficulty of developing and utilizing water resources.
(2) The present situation of water pollution in the Yangtze River Delta.
The Yangtze River Delta is a well-known water town. Water resources are a big advantage, and it should not be short of water. However, with the rapid economic development, the environmental quality of water, soil and atmosphere in the Yangtze River Delta has generally declined a lot compared with 20 years ago. Taihu Lake Basin is the heart of the Yangtze River Delta and the "heart" of the region. The water quality of Taihu Lake was Class I-II in 1960s, Class II in 1970s, Class II-III in early 1980s, Class III in the end of 1980s, and Class IV-V locally, with an average of Class IV in the mid-1990s. The water quality of1/3 Lake area was Class V or worse, with frequent cyanobacteria and Alternanthera philoxeroides, serious eutrophication of the lake, and it was difficult to guarantee the safety of drinking water.