Differences in soil formation and distribution in the north and south of China

1. Zonal latitude, that is, the difference between north and south.

Due to the great difference between the north and south of China, it is distributed in several different temperature zones, and the temperature difference is very different. Different temperatures affect the differentiation of soil parent material, and the form transformation of soil has resulted in zonal differences in soil, from the brick red soil south of Nanling (including Taiwan and Hainan) to the red soil south of the Yangtze River to the yellow brown soil in Jiangxi, Hunan, Jiangsu, Anhui and western Henan - the brown soil in Liaoning, Beijing-Tianjin-Hebei and Shandong - the dark brown soil in Heilongjiang and Jilin.

2: Longitude zonality, that is, the difference between east and west, due to the huge span of east and west in China, from Heilongjiang in the east to Xinjiang in the west, and the distance gap from the Pacific Ocean is different, and the difference in water volume is obvious. Generally, from the coastal to the inland vegetation, humid forests, semi-humid forest-steppes, semi-arid steppe soils, and arid deserts, appear sequentially.

The soil generally appears as follows: dark brown soil east of the Daxing'an Mountains in Heilongjiang Province - chernozem soil west of the Daxing'an Mountains - chestnut lime soil in Inner Mongolia and parts of Ningxia - brown limestone soil in Gansu - gray limestone soil and desert soil in Xinjiang. Due to the decrease in organic matter in the soil, the soil changes from black to white, and the soil is basically fine to coarse.

It's a major east-west strip.

Three: vertical zonality, that is, altitude differences.

There are some differences in different parts of the line, and there are differences between the north and south slopes of the same mountain, but the general trend is similar. With the increase of mountain altitude, the heat decreases, and the precipitation increases within a certain altitude and decreases after exceeding the elevation, resulting in regular changes of vegetation and other soil-forming factors with altitude, and the characteristics of vertical zonation and regular replacement of soil types correspondingly.

Taking the southern slope of the Himalayas as an example, the frozen soil above the ice line - grass felt soil above 4500 meters - brown black felt soil above 4200 meters - brown felt soil above 3800 meters - dark brown soil above 3400 meters - brown soil above 3100 meters - yellow-brown soil above 2600 meters - yellow soil above 2100 meters - yellow brick red soil.

The general trend is that the further down, the more it tends to the southeast of our country, the more it goes up, the more it tends to the northwest.

Fourth, not all soils have zonal laws, and the laws only belong to most soils. Below I will enumerate the non-zonal soils:

1. Paddy soil, as long as there is rice planting, and the planting time is long enough, there is paddy soil distribution.

2. Secondary saline soil.

3. Purple soil in Sichuan.

In short, China's soil has a strong zonality, but China's land is large and wide, the terrain changes greatly, and the agricultural cultivation has a long history, and there are some non-zonal soils embedded in the overall zonality.

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Summary. The characteristics of cultivated land resources in China are as follows:

1. The per capita cultivated land area is small.

Although the total area of cultivated land in China is relatively large, the area of cultivated land per capita is relatively small, only 1 4 of the world's per capita cultivated land area.

2. Uneven distribution.

Based on the factors of climate, biology, soil, topography and hydrology, China's cultivated land is roughly distributed in the humid region in the southeast, the semi-humid monsoon region, the semi-arid region in the northwest, the arid inland region and the Qinghai-Tibet Plateau region in the west. The southeastern humid and semi-humid monsoon regions concentrate more than 90% of the country's cultivated land.

This paper analyzes the distribution characteristics and climatic causes of cultivated land in China.

The characteristics of cultivated land resources in China are as follows: 1. The per capita cultivated land area is smallAlthough the total cultivated land area in China is large, the per capita cultivated land area is relatively small, and only 1 of the world's per capita cultivated land area is unevenly distributed Combined with climate, biology, soil, topography and hydrological factors, China's cultivated land is roughly distributed in the southeastern humid Tuanjiao area, the semi-humid monsoon region, the northwest semi-arid region, the arid inland area and the western Qinghai-Tibet Plateau region. The southeastern humid and semi-humid monsoon regions concentrate more than 90% of the country's cultivated land.

It can be summarized as follows: there are more branches in the east and less in the west, and the overall distribution is uneven. The reason for the climate attack: the eastern part is mainly humid and semi-humid area, with large precipitation, which can meet the demand for cultivated land.

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1. Black soil - Northeast Plain.

Black soil is the black soil in the temperate humid and semi-humid areas, which is only found in Heilongjiang and Jilin provinces in China, mainly distributed on both sides of the Xiaoxing'an Mountains, the natural fertility of the black soil is very high, it is one of the most fertile soils in China, and it is the most important grain base in Northeast China. However, due to improper management, soil erosion is often caused, and soil fertility is quickly reduced. Moreover, there are hazards of spring drought, autumn flood and early frost. In order to ensure that various crops cultivated on the black soil can obtain high and stable yields, it is necessary to take measures such as soil conservation and fertilization and reasonable drainage and irrigation.

2. Loess - Loess Plateau.

The loess particles are fine, loose in texture, upright and contain calcium carbonate, and the water is easy to dissolve and collapse. The ground slope is large, the vegetation is sparse, and there are many heavy rains in summer, resulting in micro-landforms such as strange peaks, steep walls, karst caves, pits, and Tiansheng bridges, which also contribute to the expansion of gullies and accelerate soil erosion.

3. Saline-alkali land - North China Plain.

In the arid and semi-arid areas of northeast, northwest and north China, the precipitation is small, the evaporation is large, and the salt dissolved in the water is easy to accumulate on the soil surface. In summer, the rain is abundant and concentrated, and a large amount of soluble salt seeps into the lower layer or flows away with the water, which is the "desalination" season; In spring, the surface water evaporates strongly, and the salt in the groundwater accumulates on the surface of the soil as the capillary water rises, which is the main "salinity" season.

In some places, large water floods when watering, or low-lying areas are only irrigated but not discharged, so that the groundwater level rises quickly and salt accumulates, so that the original good land becomes saline-alkali land, this process is called secondary salinization. In order to prevent secondary salinization, water conservancy facilities should be drained and irrigated, and flood irrigation is strictly prohibited.

It is necessary to plow and hoe in time.

The root cause of the formation of saline-alkali soil is the poor water condition, so in the early stage of improvement, the focus should be on improving the soil water condition.

Generally, it is carried out in several steps, first of all, salt discharge, salt washing, and soil salt content reduction; replanting salinity-tolerant plants to fertilize the soil; Finally plant the crop. Specific improvement measures are: drainage, irrigation, salt washing, dredging improvement, rice planting, fertilization improvement, land leveling and chemical improvement.

4. Marshland - Northeast.

Topographic factors: 1. The topography of Northeast China is mainly the vast Northeast Plain, which is surrounded by mountains on three sides, which is not easy to drain and easy to form swamps, which is a prerequisite;

Climatic factors: 1. The Northeast Plain has abundant annual precipitation, low temperature and low evaporation, resulting in large soil water content and easy to form swamps;

2. There are many rivers in the Northeast Plain, and at the confluence of the rivers, especially the Sanjiang Plain is located at the confluence of the Songhua River, Heilongjiang River and Ussuri River, the water volume is abundant, the drainage is not smooth, and it is easy to form swamps.

3. The temperature in the Northeast Plain is low and the freezing period is long, so it is not easy to drain, resulting in excessive soil water content and easy to form swamps.

The Northeast Plain is rich in plant species, and a large number of plants lock in a large amount of water, making the soil have a large water content and are easy to form swamps.

The distribution of soil zonality includes horizontal zonality (including latitudinal zonality and longitudinal zonality) and vertical zonality.

For example, the zonal distribution of soil longitude in temperate regions of China from east to west is as follows: black soil-chernozem-chestnut limestone-brown limestone-gray desert soil-gray desert soil.

This is due to the fact that China is moving from east to west, farther and farther away from the ocean, the climate is becoming more and more arid, and the vegetation has evolved from meadow-grassland-steppe-desert-desert in turn, resulting in different soil types due to the content of soil organic matter and the leaching and deposition of substances in the soil.

The northern plains are vast, with more arable land, but lower heat and less precipitation, mainly dryland, and the main food crop cultivated is wheat; The south is hilly and mountainous, but the heat is high, the precipitation is abundant, mainly paddy fields, and the main food crop is rice Among them, the main reason is the significant difference in climatic conditions Therefore, d

Due to the difference of water conditions, the vegetation and soil are replaced from east to west in the direction of longitude, and the zonal distribution law of longitude is more significant in the temperate zone and warm temperate zone north of the Qinling Mountains and Huaihe River, from east to west, there are: temperate forest steppe, meadow steppe black soil zone, mainly distributed in the eastern plateau plain of the Northeast Plain, the community is mainly composed of grasses and weeds, the building species are Baikal needlegrass, L. chinensis, the seasonal changes of the grassland are obvious, and the shady slope in the hilly area is generally deciduous broad-leaved forest, It shows the characteristics of the transition from forest belt to grassland, and the zonal soil is black soil series, including black soil, chernozem, gray black soil, etc., and the soil has a deep humus layer, which has good conditions for the development of agriculture, animal husbandry and forestry. The warm temperate forest-steppe brown soil zone is mainly distributed in the Loess Plateau, and the deciduous trees are represented by Quercus liaotungensis, poplar and birch, as well as conifers such as Pinus tabuliformis and Arborvitae, and the understory develops into neutral to alkaline brown soil. The temperate dry steppe chestnut calcareous soil zone is mainly distributed in the southeast of the Inner Mongolia Plateau, the eastern part of the Ordos Plateau and the northwest of the Loess Plateau. The brown calcareous soil zone of desert steppe is mainly distributed in the western part of the Inner Mongolia Plateau, the western section of the Yinshan Mountains, and the west of the western foot of Helan Mountain, the typical vegetation is mainly composed of xerophytic strong needlegrass and S. sapiotrope, etc., the appearance is monotonous, the coverage is not more than 15 30, the development is alkaline brown limestone soil under the vegetation environmental conditions of temperate desert steppe, and the development of gray limestone soil under the vegetation environmental conditions of warm temperate desert steppe, compared with the brown limestone, the humus accumulation process is slightly stronger, and the calcification process is slightly weaker; The desert desert land zone is mainly distributed in the temperate desert zone such as the Alxa High Plain, Hexi Walkway, Junggar Basin, warm temperate desert zone such as the Kashun Gobi and Tarim Basin, as well as the Qaidam Basin, with very poor plant species and ecological characteristics adapted to arid habitats, mainly shrubs or semi-shrubs, among which the species of Chenopodaceae are the most. The zonal desert series includes gray desert soil, gray brown desert soil and brown desert soil, among which gray brown desert soil and brown desert soil are typical desert soils in temperate and warm temperate zones, and gray desert soil is the transitional soil at the edge of temperate desert.

Longitudinal zonal distribution of soil Influencing factor: The distribution of sea and land leads to the decrease of water from coastal to inland. Temperate zone of China (from east to west): leaching soil (dark brown soil) - wet soil (black soil) - calcareous soil (...).

Answer]: Soil horizontal zonality: The zonal distribution of soil parallel to latitude or longitude in the plain area is high and high.

Latitudinal zonality: refers to the distribution regularity of soil changes with different latitudes. Classification conditions: humid and hot bioclimate dominated by heat.

Longitudinal zonality: refers to the distribution law of soil changes with different longitudes. Classification conditions: changes in soil types due to distance from the ocean, precipitation due to mountain range, wind direction, and biological differences. Spring celebration.