Causes of land salinization in Jiangsu Province

Question 1: Describe the distribution characteristics of saline-alkali land in China. China is a big country with saline-alkali land, ranking third among the 10 countries in China. Saline-alkali land in China is distributed in northwest, northeast, north China and coastal areas 17 provinces and regions. The total area of saline-alkali wasteland and saline-alkali land affecting cultivated land exceeds 500 million mu, of which the agricultural development potential accounts for more than 10% of the total cultivated land area in China.

1. Saline soil and seawall along the eastern coast

It is estimated that there are 2 1 10,000 mu of shallow water and beaches at the 1.5 m isobath. Coastal saline soil area of Jiangsu, Shandong, Hebei, Tianjin and Liaoning provinces north of the Yangtze River estuary150,000 mu. According to relevant data of Jiangsu Province, the tidal flat area in Jiangsu Province is 9.8 million mu. Coastal saline soil is characterized by high salt content in the whole soil, and chloride is the main salt component.

Zhejiang, Fujian, Guangdong, Guangxi, Hainan and other provinces south of the Yangtze River have small coastal saline soil areas. There is a lot of rainfall here, and the soil has a strong leaching effect. Coastal saline soil formed by seawater soaking land is gradually desalinated into saline soil by rainwater scouring. The average salt content of 1m soil is less than 0.6%. Affected by forest biota, acidic saline-alkali soil is formed, with sulfate as the main salt component and slightly acidic soil.

2. Saline soil in Yellow River, Huaihe River and Sea Plain

According to satellite data, there are about 20 million mu. After long-term management and improvement, the area has been greatly reduced. Salt crust with a thickness of 1-2cm is formed on the surface layer, and the salt content is above 1%, and the salt content in the soil layer below the crust is reduced to about 0. 1%.

3. Saline soil in Northeast Plain

Songnen plain is the most abundant. According to the statistics of three northeastern provinces, * * has 47.959 million mu of saline-alkali land. Among them, 2 1 10,000 mu has been developed and utilized. Saline soil in Songnen Plain mostly belongs to soda alkaline soil, with low salt content, sodium carbonate and bicarbonate, high PH value, great toxicity to plants, and many pieces of bare land. The saline soil and alkaline earth here have high organic matter content, heavy soil quality and good water and fertilizer conservation performance. Once developed and utilized, the crop yield is very high.

4. Semi-desert inland saline soil

Including Hetao Irrigation District in Inner Mongolia, Yinchuan Irrigation District in Ningxia, Hexi Corridor in Gansu and Junggar Basin in Xinjiang. * * * has tens of millions of acres. Saline-alkali composition is complex. There is a large area of alkaline earth in Yinchuan Plain of Ningxia.

5. Fresh and extremely dry saline soil

There are tens of millions of mu of saline-alkali land in Tarim Basin, Turpan Basin and Qaidam Basin in Qinghai. The distribution area is very large. The soil has a high salt content, and a thick and hard salt crust is often formed on the surface. The whole profile has a high salinity measurement.

Question 2: Compulsory Geography 2 1. Population and city

1, population growth model

(1) Know the main characteristics of population growth in different development stages.

(2) Give examples to illustrate the main characteristics of population growth in different regions.

Comparison of population growth stages

Stage Original Low Growth Stage (a) Accelerated Growth Stage (b) Slow Growth Stage (c) Low Growth Stage (d)

Population growth mode "high and low" mode "high and low" mode "transition" mode "low and low" mode

special

The higher the birth rate, the lower it begins to decline, and the lower it further declines, low.

The high mortality rate dropped rapidly, the low mortality rate continued to drop, and the low mortality rate continued to drop.

The natural growth rate is low, the fluctuation is greatly improved, and the high gradually decreases to the low.

Population growth is relatively static or low, and rapid growth begins to slow down to zero or negative growth.

The stage of social development, the initial stage of agricultural industrialization, developed countries, developing countries and developed countries in Europe around the 1950s, and now.

Indigenous people in the depths of tropical virgin forests in typical areas, Tanzania and Kenya in East Africa, and most developing countries such as Germany, Britain and France.

2. Population migration

(1) Give examples to illustrate the main reasons of population migration in different periods and regions.

Population migration: refers to the phenomenon of population migration in or out of regions, which leads to permanent or long-term changes in residence.

Early human population migration

Reasons for migration during the period

Primitive society pursues means of subsistence.

The attraction or escape of land reclamation to famine, war and religious persecution in agricultural society

15-/kloc-World Population Migration in the 0/9th Century

Migration reason flow direction

Geographical discovery ended the long-term isolation between the "old continent" and the "new continent"

(2) The opening of new air routes has promoted the connection between the old and new continents.

(3) capitalist development and colonial expansion (1) Europeans (Spain, Portugal, Britain, France, the Netherlands and other countries) moved to America and Oceania.

(2) European colonists sold slaves to the United States.

Population migration after World War II

Specific manifestations of migration reasons

Political reasons (1) Some countries in Eastern Europe redraw their national boundaries and their populations migrate to each other.

② The partition of India, the largest international immigrant in Asia.

(3) In African countries that achieved independence, the original colonists were repatriated.

Due to economic reasons, Europe and North America have become the main immigrant areas.

With the development of emerging cities and industries, the population of the United States has moved from the northeast to the emerging industrial cities in the west.

Example: Schematic Diagram of Migrant Workers and Businessmen in China in the Middle and Late 1980s.

Since the end of the 20th century, with the rapid development of China's reform, opening up and economic construction, a large number of rural surplus laborers have flocked to cities, forming a special huge population flow-"migrant workers flow".

3. Environmental carrying capacity and reasonable population capacity

(1) Distinguish the meaning of environmental carrying capacity and reasonable population capacity.

Environmental carrying capacity: refers to the population scale and economic scale that can be accommodated by environmental resources under the premise of maintaining relative stability in a certain period of time. That is, the limit of the number of people who can bear is a warning value.

Population capacity: refers to the reasonable carrying capacity of the earth and its parts to the population, which is an ideal value.

For example, at the end of 1980s, China Academy of Sciences estimated that China's environmental carrying capacity was 654.38+600 million people, while the reasonable population capacity was 800-900 million people.

4. Urban spatial structure

(1) With examples, understand the distribution characteristics of the main functional areas of the city and analyze the spatial structure of the city.

Urban functional area: all activities in the city need to occupy a certain amount of land. Because the urban land area is relatively limited, the traffic accessibility and land price of different plots are also different. Therefore, there must be competition between activities, which leads to the high concentration of similar activities in space and the formation of urban functional areas.

Comparison of three major functional areas in cities

Distribution characteristics of urban functional areas

Business districts with convenient transportation in the city center and on both sides of the street.

This industrial zone is located in the suburb of the city, along the main traffic lines.

Residential areas are the most widely distributed, and high-rise and low-rise residential areas have a backward development trend.

⑵ Understand the causes of urban spatial structure.

The causes of urban functional zoning

① Historical reasons: The original land use status of the city largely determines the present situation of urban functional zoning. For example, the central city of Beijing has become an administrative district. On the other hand, the functional division of cities is dynamic >>

Question 3: Why does the northeast farmland summarize the knowledge of geography required for the college entrance examination to the east and west (perfect)

Chapter II Regional Geographical Environment and Human Activities

1. 1 regional differences

In three natural areas of China:

Reason: the distribution of latitude, land and sea and altitude.

Natural differences between topography and climate

Natural geographical indication of five elements of soil and vegetation: natural region (mirror image)

hydrology

3. Fundamental differences among the three natural fields (P5)

East monsoon region, northwest arid and semi-arid region, Qinghai-Tibet alpine region

400 mm precipitation line, Kunlun mountain-aluminum

Located in Jinshan-Qilian Mountain area, 45% of the eastern coast is quiet inland, the surrounding mountains are 30% high and the Qinghai-Tibet Plateau in the southwest is 25%.

because

or

/& gt； ring

Plateau landform, the landform of plateau, hills, water, mountains and frozen weathering from the plain to the basin.

Climate monsoon climate, temperate continental climate with both rain and heat, arid and alpine climate: low temperature, large temperature difference between day and night, strong wind and strong solar radiation.

Hydrological characteristics: Flowing rivers, mainly rainwater-irrigated flowing rivers outside rivers, artificial lakes, glaciers and lagoons.

Soil, forest and forest grassland soil, meadow soil and desert soil (organic matter, salt) native soil

Coniferous forest in cold temperate zone in northern vegetation

Life of deciduous broad-leaved forest in temperate zone

Move to the most important agricultural areas, agriculture (planting) animal husbandry, irrigation agriculture, oasis agricultural animal husbandry and valley agriculture.

Under unfavorable conditions

There are more people and less water, environmental problems, land desertification, low temperature salinization, thin air, more wind and less water, which have a far-reaching impact on rugged terrain.

Weak culture

Backward economic development

/& gt； Supplement to

Responsible for the inaccessible southwest and Qinghai-Tibet Plateau.

Southwest China (here is the eastern monsoon region): (1) rugged terrain; (2) geological disasters (landslides, mudslides, etc. )

(2) Tibetan alpine region: (1) rugged terrain, cold and lack of oxygen.

Frozen soil development

Internal differences, east (1) monsoon region, north-south differences.

① dividing line: 0℃ isotherm

Qinling-Huaihe warm temperate zone and subtropical zone

800 mm annual precipitation line

Semi-humid area

② North-South differences (as shown in Figure P9)

Human activities in the natural environment

Topographic climate river

Ancient fruit house for planting crops >:

Question 4: Environmental problems and solutions of South-to-North Water Transfer Project 1. Secondary salinization of soil.

At present, the Huang-Huai-Hai Plain has formed a relatively complete drainage system and accumulated rich experience in preventing soil salinization. The East Route Project of South-to-North Water Transfer Project still belongs to the nature of water supplement, and it will not cause secondary salinization of soil in the northern irrigation area under normal circumstances.

2. The schistosomiasis area moved northward.

According to the field experiment of Oncomelania hupensis living and breeding in the natural environment north of latitude 3315' and the practice of South-to-North Water Transfer Project in Jiangsu Province, it is proved that due to climatic reasons, large-scale water transfer will not expand the schistosomiasis epidemic area north of latitude 38.

3. Immigration environment issues

Since Danjiangkou Reservoir has flooded 200,000 mu of cultivated land and 220,000 immigrants (survey 1990), if all the immigrants are resettled locally, the environmental pressure in the reservoir area will increase. In addition to local resettlement of some immigrants, comprehensive measures can be taken to resettle immigrants in new irrigation areas to properly solve the problem.

4. Influence on hydrological situation in the middle and lower reaches of Hanjiang River

Water transfer1.30-1.40 billion cubic meters, accounting for 1/3 of Danjiangkou dam runoff, accounting for 22% of Hanjiang river basin runoff, which may cause changes in hydrological situation in the middle and lower reaches of Hanjiang river. After taking comprehensive compensation measures, the adverse effects can basically be eliminated.

5, the impact on the middle and lower reaches of shipping

Water transfer1.30-1.400 million cubic meters, the water level of the river will drop by 0.6 to 1.0 meters, which will have a certain impact on shipping and water transfer along the river and can be eliminated after the construction of cascade hubs.

6. Influence on bed-building movement of downstream river.

Water transfer1.30-1.400 million cubic meters (the diversion scale is 500 cubic meters per second) will reduce the number of days when 800- 1.00 cubic meters per second appears in the middle and lower reaches of the Hanjiang River by about 20 days, and the number of days when 1.00-3000 cubic meters per second will be reduced/kloc-

Question 5: Why can't you always learn well if you work hard? Have you ever tried new learning methods and looked for a relaxed and happy way of self-study? Maybe it would be better. Maybe you're under too much pressure. Although you study hard every day, have you ever thought about how efficient you are? Can I watch it every time? Pay attention to the combination of work and clothing, and get up in the morning to exercise, which will increase the effect! Give it a try! But this is only my personal opinion!