What are the geographical features of Songnen Plain?

Songnen Plain is located in the southwest of Heilongjiang Province, bounded by Songliao Basin in the south, Xiaoxing 'anling in the north, and the eastern mountainous area and Daxinganling in the east and west respectively. The whole plain is slightly rhombic. Songnen Plain and Liaohe Plain are separated by the watershed of Songhua River and Liaohe River, which is located near Changchun City. They are also called Songliao Plain, which is the main part of Northeast Plain. The land area of Heilongjiang Province is 103200 square kilometers, accounting for 2 1.6 1% of the total area of the province. Songnen plain is a geological structural depression area, which belongs to a part of Songliao fault depression zone. The southwest of the depression is still sinking and the northeast is rising.

geographical environment

zone

There are alluvial and diluvial platforms in the piedmont and eastern mountainous areas of Xiaoxing 'anling, such as the wave platforms in Keshan, Baiquan and Bei 'an, the ridge platform between Keluo River and Namur River, the flat and oblique platforms in Hailun and Suihua, and the hilly platform east of Ashe River. The altitude is about 200-300m, and the relative altitude is 30- 100m. The surface erosion is serious, and many places are criss-crossed by running water. In this area of Songnen Plain, the upper part of the composition material is loess loam and the lower part is gravel layer, and black soil is widely developed on the surface. It is formed by the process of black soil, a special meadow, under the conditions of vegetation and loess-like parent material in temperate humid shrub meadow or middle grass meadow. Before reclamation, the organic matter content was as high as 10%. Humic acid is the main component of humus, and the ratio of surface humic acid to fulvic acid is 1.38- 1.6, with a maximum of 2. Soil is rich in nutrients, has strong ability of water and fertilizer conservation, and is suitable for the growth of many crops. It is the main agricultural soil resource in Heilongjiang Province.

In front of the Daxinganling Mountains, the undulating erosion platform is about 200-250 meters above sea level. The relative height is 10-30m. There are many weathered clastic materials and clay in the platform, which belong to Baitushan Formation formed from the end of Tertiary to the beginning of Quaternary. The soil belongs to erosion and leaching type, with thin soil layer, rough texture and acidic reaction.

The middle and lower reaches of Nenjiang River are alluvial plains covered with sand dunes, which cover the floodplain and the first and second terraces on both sides. The terrain is low and the slope is very small. Width of floodplain10km. Tens of centimeters to three or five meters above the river bed. The upper part of the composition material is clayey silt and the lower part is gravel. The first terrace is about10m higher than the riverbed, and the surface is covered with loess loam and clayey silt. The second terrace is 30-50 meters higher than the river bed, and the composition is loess loam or gravel layer. There are aeolian sand dunes, sand dunes, sand ridges and wavy sand fields on the surface of this area. Although these soils can be cultivated, they leak water and fertilizer, and it is easy to bury fertile fields when wind erosion is serious. Therefore, it is advisable to plant trees and grass and apply organic fertilizer as land for forestry and animal husbandry, but not for reclamation.

climate

Changchun, which has the reputation of "Spring City in the North", also has the titles of "International Automobile City", "Green Food City", "Science, Education and Culture City" and "Movie City". Changchun has a pleasant climate with four distinct seasons: spring is short, dry and windy; Summer is warm and rainy, and there is not much hot weather; Autumn is crisp and the temperature difference between day and night is large; Winter is long and cold. Jilin City, the only city in China with the same name as the province, is famous for its beautiful scenery, rime fairyland and ski paradise, and is known as "Guilin in the south and Jilin in the north". Songyuan, known as "granary, meat warehouse, fishing village and oil sea", is a new petrochemical city established in 1992, where Jilin Oilfield is located. There are "three rivers, one river and one lake" (Songhua River, the second Songhua River, Nenjiang River, Lalin River and Chagan Lake), which is one of the few undeveloped hydrophilic cities and riverside cities in China. On July 23, 2007, the National Astronomical Observatory announced the naming bulletin of the International Astronomical Union: Asteroid 1997JZ7 was officially named "Songyuan Star".

topography

Songnen Plain accounts for more than13 of the province, including 5.59 million hectares of cultivated land. The soil is fertile, with black soil and chernozem accounting for more than 60%. Rich in soybeans, wheat, corn, beets, flax, potatoes and so on. It is an important commodity grain base in Heilongjiang Province and the whole country, with a commodity rate of over 30%. Grassland is relatively concentrated, including Qiqihar, Gannan, Longjiang, Tailai, Dorbert, Fuyu, Lin Dian, Daqing, Anda, Zhaodong, Zhaozhou, Zhaoyuan and other cities and counties, with more than 2 million hectares. The area of the first, second and third grassland composed of Leymus chinensis, Cinnamomum camphora, Vicia faba and Puccinellia tenuiflora is 76%, and the animal husbandry is developed. Rich in petroleum resources, it has the largest crude oil production base in China and the famous Daqing oil region in China. 1the total population at the end of 1992 was 20.03 million, accounting for 56.8% of the total population in the province; Among them, the agricultural population is 6.5438+0.3549 million, accounting for 67.7% of the agricultural population in the province.

Songnen Plain is mainly formed by alluvial of Songhua River and Nenjiang River. Nenjiang, Nehe, Yi 'an, Keshan, Dedu, Wudalianchi, Bei 'an, Kedong, Baiquan, Helen, Suiling, Qing 'an, Suihua, Wangkui, Cyclobalanopsis glauca, Mingshui, Fuyu, Lin Dian, Qiqihar, Gannan, Longjiang, Tailai, Dulbert, Daqing and Zhaoyuan. The Songnen Plain has 5.59 million hectares of arable land and fertile soil, with black soil and chernozem accounting for more than 60%, and is rich in soybeans, wheat, corn, beets, flax and potatoes, making it an important commodity grain base. In addition, grasslands are concentrated, animal husbandry is developed, and underground oil resources are abundant.

The south-central part of Songnen Plain is a relatively flat area, and chernozem is widely developed on the surface, with an organic matter content of 4-8%, humus is mainly humic acid, and exchangeable base ions are mainly calcium and magnesium, which belongs to salt-based saturated soil. Except humus layer, other layers are slightly alkaline, with PH value of 8-8.5, moderate texture and good structure, second only to black soil, which is suitable for agriculture.

There are alluvial and diluvial platforms in the piedmont and eastern mountainous areas of Xiaoxing 'anling, such as the wave platforms in Keshan, Baiquan and Bei 'an, the ridge platform between Keluo River and Namur River, the flat and oblique platforms in Hailun and Suihua, and the hilly platform east of Ashe River. The altitude is about 200-300m, and the relative altitude is 30- 100m. The surface erosion is serious, and many places are criss-crossed by running water. In this area of Songnen Plain, the upper part of the composition material is loess loam and the lower part is gravel layer, and black soil is widely developed on the surface. It is formed by the process of black soil, a special meadow, under the conditions of vegetation and loess-like parent material in temperate humid shrub meadow or middle grass meadow. Before reclamation, the organic matter content was as high as 10%. Humic acid is the main component of humus, and the ratio of surface humic acid to fulvic acid is 1.38- 1.6, with a maximum of 2. Soil is rich in nutrients, has strong ability of water and fertilizer conservation, and is suitable for the growth of many crops. It is the main agricultural soil resource in Heilongjiang Province.

In front of the Daxinganling Mountains, the undulating erosion platform is about 200-250 meters above sea level. The relative height is 10-30m. There are many weathered clastic materials and clay in the platform, which belong to Baitushan Formation formed from the end of Tertiary to the beginning of Quaternary. The soil belongs to erosion and leaching type, with thin soil layer, rough texture and acidic reaction.

The middle and lower reaches of Nenjiang River are alluvial plains covered with sand dunes, which cover the floodplain and the first and second terraces on both sides. The terrain is low and the slope is very small. Width of floodplain10km. Tens of centimeters to three or five meters above the river bed. The upper part of the composition material is clayey silt and the lower part is gravel. The first terrace is about10m higher than the riverbed, and the surface is covered with loess loam and clayey silt. The second terrace is 30-50 meters higher than the river bed, and the composition is loess loam or gravel layer. There are aeolian sand dunes, sand dunes, sand ridges and wavy sand fields on the surface of this area. Although these soils can be cultivated, they leak water and fertilizer, and it is easy to bury fertile fields when wind erosion is serious. Therefore, it is advisable to plant trees and grass and apply organic fertilizer as land for forestry and animal husbandry, but not for reclamation.