1. Further understand the causes of soil erosion, especially the destruction of the Loess Plateau by human factors, understand the relationship between human activities and the natural environment, and understand the reason that human beings should care for the environment in the process of transforming nature.

2. It is imperative to further understand the work of soil and water conservation and take corresponding measures.

3. To further understand the effective method of soil and water loss control in the Loess Plateau-small watershed comprehensive control and its effect, we can master the ideas and methods of analyzing soil and water loss and its control.

Knowledge expansion contact

In the review, we can focus on the idea of "the cause of soil erosion-the characteristics of soil erosion-the harm of soil erosion-the treatment of soil erosion", so that we can fully contact with knowledge and improve our geographical thinking ability.

(A) the causes of soil erosion

The causes of soil erosion are natural factors and human factors. Before human society, soil erosion in the Loess Plateau was mainly caused by natural factors. After entering human society, with the development of production activities, human factors have become the main cause of soil erosion.

1. The Loess Plateau is located in the second step of China, which is the transition zone from the second step to the third step.

2. The Loess Plateau is also a marginal area affected by the southeast monsoon and southwest monsoon in China, which makes the precipitation decrease from southeast to northwest or from southwest to northeast. The north and south of the Loess Plateau span three temperature zones: subtropical zone, warm temperate zone and temperate zone. East and west span semi-humid, semi-arid and arid areas, and the regional differences and transitions of climate are very significant. This area is located at the tail of monsoon, with a wide range of drought and semi-drought, unstable precipitation, frequent droughts and sandstorms, and low and unstable productivity of natural grassland and dry farming. The climate drought and the instability of precipitation, loess and sandstorm make the ecological environment in this area very fragile.

3. Soil erosion caused by human factors such as vegetation destruction, unreasonable farming system and mining.

(2) Characteristics of soil erosion

1. High erosion strength.

2. Spatial and temporal distribution is concentrated. The sediment yield from June to September accounts for more than 80% of the annual sediment yield.

3. Sediment mainly comes from river erosion. Gully development and gully erosion are very serious in this area.

(C) the harm of soil erosion

Serious soil erosion not only causes the deterioration of local ecological environment, poverty of the masses and economic backwardness, but also poses a great threat to the downstream flood control safety.

1. Deteriorate the ecological environment and restrict economic and social development. Soil erosion leads to the decrease of cultivated land area, soil fertility and land productivity.

2. Sediment silted the downstream riverbed, threatening the flood control safety of the Yellow River.

3. Affect the rational and effective utilization of water resources.

Control soil erosion

The control of soil erosion should aim at the causes of soil erosion, especially the man-made causes, and put forward the measures to be taken for soil and water conservation.

1. Compress agricultural land, improve land productivity and build basic farmland.

2. Expand the planting area of forest and grass.

3. Improve grassland vegetation, rationally graze and protect grassland.

4. Retain the topsoil of the mining area and vigorously reclaim it.

5. Comprehensive management of small watershed.

(1) Insist on taking small watersheds (equivalent to gullies or river ditches) as a unit, taking the construction of basic farmland such as horizontal terraces and ditches and dams as a breakthrough, and comprehensively apply engineering measures, biological measures and farming (agricultural technology) measures to control soil erosion.

(2) adhere to the policy of returning farmland to forests and grasslands and take the road of comprehensive management.

(3) Adhere to the combination of governance and development, highlight economic benefits, and take the road of high quality and high efficiency.

(4) Adhere to the combination of management and development with prevention and protection to stop the momentum of destroying forest and grass vegetation.

(5) Governance policy: protecting platform, protecting slope and fixing ditch.

Analysis of typical test questions

For example, read the Schematic Diagram of the Relationship between Population, Agricultural Production and Ecological Environment in the Loess Plateau and answer the following questions.