a region , where the cultivation of rice and the breeding of fish flourish(yú mǐ zhī xiāng)

Plain in the middle and lower reaches of the Yangtze River

The synonym of "land of fish and rice" (the middle and lower reaches of the Yangtze River plain) generally refers to the middle and lower reaches of the Yangtze River Plain, Middle and lower refers to the belt plain along the middle and lower reaches of the Yangtze River to the east of the Three Gorges. It is one of the three great plains in China. It straddles seven provinces and cities in China, such as Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Zhejiang and Shanghai. It is known as the "water country". Its main industries include iron and steel, machinery, electric power, textile and chemistry. It is an important industrial base in China with developed water and land transportation.

The middle and lower reaches of the Yangtze River Plain starts from the east foot of Wushan mountain in the west, reaches the Yellow Sea and East seashore in the East, connects Tongbai mountain, the south foot of Dabie Mountain and Huanghuai Plain in the north, and reaches Jiangnan hills and the plain along Qiantang River and Hangzhou Bay in the south. It is about 1000 km long from east to west and 100-400 km wide from north to south, with a total area of about 200000 square kilometers Lixiahe plain and Yangtze River delta plain are composed of 6 plains. Generally, the altitude is 5-100 meters, mostly below 50 meters. The annual average temperature is 14-18 ℃, and the annual precipitation is 1000-1500 mm.

The middle and lower reaches of the Yangtze River Plain is located in the fold fault depression belt of the Yangtze paraplatform. A series of fault basins were formed by the Yanshan movement and then by the Yangtze River cutting, connecting and alluvial. Influenced by the neotectonic movement, the Cretaceous Tertiary red layer and Quaternary red soil layer at the edge of the plain rose slightly and became red soil hills with a relative height of 20-30 meters after being cut by flowing water, while the middle and coastal areas along the river continued to decline, forming flood plain and coastal plain.

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 also an area with the richest water resources in China. The natural water system of the Yangtze River and the crisscross man-made canals make this area the area with the highest river network density in China. At the same time, this area is the most concentrated area of freshwater lakes in China. The famous freshwater lakes are Poyang Lake and Dongting Lake.

physical geography

topographic features

The prominent features of the terrain are low and flat terrain, crisscross rivers and canals, and scattered lakes. Generally, the altitude is 5-100 meters, but most of them are below 50 meters. The flood plain and coastal plain are in the middle and coastal areas along the river. The topography of the Hanjiang Delta also inclines slightly from northwest to Southeast, and lakes gather in groups in the southeast front. Most of the Dongting Lake Plain is below 50 meters above sea level, and the terrain is high in the north and low in the south. Poyang Lake Plain is low and flat, most of which are below 50 meters above sea level, with dense water network, and the surface is covered with red soil and river alluvium. To the north of the delta is Lixiahe plain. The plain is a dish shaped depression of high, middle and low in Zhou Dynasty. The north margin of the depression is the old course of the Yellow River; the south margin is the North Bank of the Yangtze River Delta; the west margin is Hongze Lake and Yunxi dike; and the east margin is the coastal plain of Northern Jiangsu.

Formation process

The middle and lower reaches of the Yangtze River Plain is located in the fold fault depression belt of the Yangtze paraplatform. The Yanshan movement produced a series of fault basins, which were cut, connected and alluvial by the Yangtze River, forming the whole of the present middle and lower reaches of the Yangtze River Plain. Influenced by the neotectonic movement, the Cretaceous Tertiary red layer and Quaternary red soil layer at the edge of the plain rose slightly and became red soil hills with a relative height of 20-30 meters after being cut by flowing water, while the middle and coastal areas along the river continued to decline, forming flood plain and coastal plain. Jianghan Plain is mainly formed by the alluvial deposits of the Yangtze River and Hanjiang River; Dongting Lake Plain is mainly formed by the alluvial deposits of the Yangtze River flowing southward through Taiping, Ouchi, Songzi and Tiaoxin (blocked in 1958) on the South Bank of Jingjiang River; Poyang Lake Plain is mainly formed by the alluvial deposits of Ganjiang River, Fuhe River, Xinjiang River, Xiuhe River and Raohe River, except for the marginal red soil hills; Jiangsu Anhui plain is mainly formed by the alluvial deposits of Ganjiang River, Fuhe River, Xinjiang River, Xiuhe River and Raohe River It used to be a plain formed by the alluvial deposits of Zhenjiang River and Yangtze River, including Wuhu plain and Chaohu plain.

Area covered

Soil condition

The soil in the middle and lower reaches of the Yangtze River Plain is mainly yellow brown soil or yellow cinnamon soil, red soil in the south margin, and paddy soil in most of the flat land. The content of soil organic matter under natural vegetation can reach 70-80 g / kg, but it is greatly affected by soil erosion and farming methods. The content of organic matter in yellow brown soil was also relatively high, but it decreased significantly after cultivation. The content of organic matter in purple soil is generally low, usually in forest grassland farmland. High content of soil organic matter is conducive to the formation of a good structure, enhance the cohesive force of soil particles, and improve the ability of water storage and soil conservation. The red soil, yellow soil, yellow brown soil and calcareous soil in this area are generally of heavy texture, poor water permeability and large surface runoff. If the vegetation disappears and the soil structure is damaged, soil erosion is very easy to occur. Although the purple soil and coarse bone soil have good water permeability, the soil layer is mostly shallow, and they are also prone to strong erosion in the case of losing vegetation protection and high rainfall intensity. from 1940 to 2002, 47% of the rural areas in the middle and lower reaches of the Yangtze River Plain with an area of 86 × 103 square kilometers underwent land use and cover transformation, mainly due to the decrease of cultivated land and the increase of non cultivated land. The area change of different land use and cover types caused the change of soil organic carbon storage, in which the area of paddy field and idle water area decreased by 21.5% and 6.7% respectively, and the soil organic carbon storage of 0-30 cm soil (or sediment) decreased by 41.8 TGC and 12.9 TGC respectively, while the construction land dominated by aquaculture, non leakage surface, perennial woody crops and annual crops 2%, 7. 7%, 3. 5% and 2. 0% respectively, which increased soil organic carbon storage by 32. 2tgc, 22. 2tgc, 12. 2tgc and 6. (Note: TGC is the value of soil organic carbon content, unit < / I > < I >) < / I >

Climatic characteristics

Most of the plains in the middle and lower reaches of the Yangtze River belong to the north subtropical zone, and a small part to the north edge of the middle subtropical zone. The annual average temperature is 14-18 ℃, the average temperature of the coldest month is 0-5.5 ℃, the absolute minimum temperature is - 10 ~ - 20 ℃, the average temperature of the hottest month is 27-28 ℃, and the frost free period is 210-270 days. The annual precipitation is 1000-1500 mm. The seasonal distribution is even, but there is "summer drought". The frost free period is 210-270 days, and the active accumulated temperature above 10 ℃ is 4500-5000 ℃.

Regionalization

According to the characteristics of different areas in the middle and lower reaches of the Yangtze River, the plain can be divided into six sub plains

natural resources

plant resources

● terrestrial plants the common wild herbs distributed in the middle and lower reaches of the Yangtze River Plain are Smilax glabra, motherwort, Codonopsis pilosula, Pueraria lobata, Polygonum cuspidatum, Prunella vulgaris, Peucedanum Peucedanum, Wuyao, chrysanthemum indicum, Sanguisorba officinalis, Artemisia capillaris, Phyllostachys pubescens, Polygonum multiflorum, Ligustrum lucidum, nanshashen, Stemona, Trichosanthes, Platycodon grandiflorum, Salvia miltiorrhiza, Arctium lappa, epimedium, Baiqian, Hedyotis diffusa, polygonatum odoratum There are no summer, no Radix pseudoacacia, Caulis spp., Radix Bupleuri, Bupleurum chinense, Bupleurum chinense, Aristolochia Bupleuri, Aristolochia, shedding, Artemisia argyi, Centella asiatica, etc. the arbor species include camphor tree, privet, holly, holly, maple, Wutong, Albizzia, mume and jujube, etc. ● aquatic plants in the plain area of the middle and lower reaches of the Yangtze River, aquatic plants are mainly distributed in lakes, and they are regularly distributed in a ring from the shallow water along the coast to the deep water in the center, followed by emergent plant zone, floating plant zone and submerged plant zone. Emergent hydrophytes refer to the species whose roots are rooted in the bottom mud and whose upper parts or leaves are on the surface of the water. They are mainly distributed in shallow water, shallow ponds, gullies and fields of the inner lake. The main species are Phragmites australis, Shuizhu, Typha Orientalis, lotus, Zizania latifolia, arrowhead, Alisma orientalis, Sparganium nigrum, Acorus calamus, Acorus tatarinowii, Welsh onion, yujiuhua, Hedyotis scandens, Allium chinense, etc The main species are Euryale ferox, rhombia, wild rhombia, Ipomoea aquatica, duckweed, Azolla, Azolla, mangjianghong, Azolla, Eichhornia crassipes, Alternanthera philoxeroides, Brasenia schreberi, water lily, pingpengcao, water fern, water dragon, etc. the submerged plants rooted in the bottom mud or submerged in the water are mostly distributed in the water depth of 4 In the warm and still water area, the main species are Potamogeton crispus, Potamogeton crispus, Potamogeton bambusoides, ceratophyta, Hydrilla verticillata, and Vallisneria, etc. in the plain where the water has accumulated for a long time or where the soil is wet, there are Juncus, oryzae graminea, arrowhead, bovine felt, sarcandra, sarcandra rotundifolia, amaranth, Polygonum, water celery, Scutellaria barbata, perilla, Mentha, etc Chanchu, Vitex trifolia, water centipede, Houttuynia cordata, three white grass, Ranunculus Ranunculus, Lobelia chinensis, Ranunculus ternatus, etc.

Animal resources

In the middle and lower reaches of the Yangtze River, there are mainly toad, earthworm, hedgehog skin, woodlouse bug, turtle shell, tortoise shell, silkworm, cicada, leech, centipede, oyster, green caterpillar, gadfly, grub, dung beetle, mole cricket, gecko (house lizard), Agkistrodon acutus, snakes, and white snake. They wear pangolin, otter, monkey, deer, bear, cat, cricket, bream, carp, carp, silver carp, carp, crucian carp, green grass and grass. In this paper, we have studied the characteristics of the fish, such as, shad, Coilia nasus, shad, Xiangyu, silverfish (including large silverfish, short snout silverfish, fine silverfish, pointed silverfish, etc.), eel, Lateolabrax japonicus and Lateolabrax japonicus (also known as four gilled Lateolabrax), Chinese sturgeon, alligator and so on.

mineral resources

There are many kinds of mineral resources in the middle and lower reaches of the Yangtze River Plain, including fluorite, magnetite, talc, amethyst, Qiushi, qingyishi, Daihe, Hanshuishi, natural copper, actinolite, mica, Yuliangshi, egonite, gypsum, coal, non-ferrous metals, etc. Non ferrous metals play an important role in China. This is mainly due to the fact that the mountains and hills in the south of the Yangtze River had been used in geological history

Chinese PinYin : yú mǐ zhī xiāng