Second, the fourth phase of the "Three North" project focusing on sand prevention and control around Beijing was launched. These two projects have covered more than 90% of the land in the sandy area of China, and constructed a national framework for sand prevention and control. The comprehensive control project of the old Yellow River sandy land and the pilot demonstration of rocky desertification control in the southern wet sandy land are also under way. The ecological construction project of preventing and controlling desertification in Hotan, Xinjiang, and the desertification land control project of one river and two rivers in Tibet have completed the planning work and are under examination and approval. It has formed an overall pattern of promoting national defense and sand control under the guidance of large projects, and opened up a situation of leap-forward development of sand control.
Third, the state's investment in sand prevention and control has increased substantially. In the past two years, the state's investment in sand prevention and control has increased from only 30 million yuan per year in the 1990s to nearly 654.38+billion yuan per mu in projects around Beijing, and 654.38+000 yuan per mu in subsidies for sand prevention and control afforestation, which has eased the pressure of people's unpaid labor and employment in sand areas and provided a strong guarantee for sand prevention and control.
Fourth, a monitoring and early warning system for desertification and desertified land has been initially established. Through 1994 and 1999 national monitoring of desertification and desertified land, the area, distribution, causes and changing trend of desertification and desertified land in China were found out. On this basis, the geographic information database and dynamic change model of desertification and desertification land are established, which provides a strong basis for sandstorm trend prediction and scientific decision-making of sand control.
Fifth, a set of effective prevention and control technologies and models has been formed, which ranks at the leading level in the world and has contributed not only to China but also to the prevention and control of desertification in the world. Many technologies, such as grid sand barrier, aerial seeding, enclosure and biological sand fixation, are initiated by our people and have achieved good results. The edited and published Practical Technologies and Models of Desertification Control in China and Traditional Knowledge and Practical Technologies of Desertification Control in China have been welcomed at home and abroad, and the English version of Traditional Knowledge and Practical Technologies of Desertification Control in China has also won the Best Practice Award of the United Nations Development Programme. The new sand control technologies and products, such as dry water, water-retaining agent and water-absorbing agent, have been popularized and achieved good results. Organize 100 experts to send science and technology to the countryside to train farmers and herdsmen in sand control skills.
Sixth, the implementation of the United Nations Convention to Combat Desertification is progressing smoothly, and the fields of foreign exchanges and cooperation are gradually expanding. Using the international stage of desertification control to publicize China's national defense and desertification control work has been well received by the international community. Last year, the Conference on Supporting China to Implement the United Nations Convention to Combat Desertification was successfully held in Beijing, with more than 40 countries and 20 international organizations participating. The United Nations Development Programme's assistance to China's monitoring capacity building and German assistance to Ningxia's sand control project are actively operating, and the prospects for foreign cooperation and exchanges are broad. The effective implementation of the Convention will enhance China's international status.
Seventh, make full use of propaganda positions to raise people's awareness of sand prevention and control. The "6. 17" World Day to Combat Desertification and Drought was publicized through various channels and media, and a campaign to combat desertification with millions of signatures was organized in 1997. 1998, street publicity was carried out in more than 0/00 cities across the country; 1999 broadcast public service advertisements on CCTV; Last year, he published full-page articles in People's Daily, Science and Technology Daily, Legal Daily and other newspapers. In order to fulfill the promise of "Green Olympics", the great significance of implementing key projects to prevent and control desertification was emphasized, and the confidence of the international community and the people of the whole country in controlling the hazards of sandstorms in Beijing and Tianjin was enhanced. Through a lot of publicity, the public's sense of urgency, responsibility and mission to prevent and control desertification has been improved, and the enthusiasm of all walks of life for sand control has never been higher.
This is China's policy of preventing and controlling desertification.
Yulin people adopt the way of cluster planting, forming a pattern of alternating density and density, which not only resists wind erosion but also solves the problem of insufficient water resources.
(1) Carry out extensive and in-depth publicity and education on environmental awareness to improve the ideological level of the whole nation. Care and care for the environment, consciously participate in the transformation and construction of the environment, and form the fashion of the whole society.
② Improve laws and regulations, strengthen law enforcement supervision, protect the environment according to law, and promote desertification control.
③ Strictly implement the family planning policy, control the excessive population growth, and constantly improve the quality of the population.
④ Developing various scientific and educational undertakings in desertification areas. Cultivate grassroots scientific and technological forces, improve the rural scientific and technological market as soon as possible, do a good job in scientific and technological services, and improve the cultural and scientific quality of people in desertification areas.
⑤ Establish an effective investment mechanism and a management mechanism in line with the current national conditions.
⑥ Establish an advanced desertification dynamic monitoring and forecasting system, make good decisions, and do a good job in information management and service.
⑦ Carry out a lasting green revolution in desertification areas, accelerate the reversal of desertification process, and gradually improve the basic functions of agricultural ecosystems.
(8) Strengthen international exchanges and cooperation in combating desertification and strive for funds and foreign aid.
(9) Accelerate the adjustment of industrial structure, rationally allocate the proportion of agriculture, forestry and animal husbandry according to market requirements, actively develop aquaculture and processing industries, divert rural surplus labor force, and reduce the pressure of population on land.
(10) Optimize the energy structure in agricultural and pastoral areas, and vigorously advocate and encourage people to use unconventional energy sources such as wind energy and light energy to reduce the damage to forests, grasslands and other resources.
2. Technical measures
(1) biological measures
(1) Seal off sand forests to grow grass and restore natural vegetation.
Implement certain protective measures (fences), establish necessary protection organizations (forest protection stations), prohibit the damage to people and animals, give plants time to thrive and gradually restore natural vegetation. At the same time, the enclosure can be replanted and managed manually to accelerate the ecological reversal.
② Planting trees, grass and fixing sand by airplane.
Aerial seeding has the characteristics of high speed, less labor, low cost and good effect, and is especially suitable for vegetation restoration in remote and barren areas with vast land and sparse population, inconvenient transportation and barren hills. The key technical problems to be solved in aerial seeding are: predicting climate, selecting site conditions, determining suitable sowing area, determining suitable sowing amount, seed treatment technology, preventing and controlling livestock and poultry diseases and insect pests, and enclosure protection.
③ Fixing quicksand by sowing, cutting, raising seedlings and planting grass.
Direct seeding afforestation and sand fixation: Sow on grassland quicksand to ensure that the seedlings reach a certain density (15-20 plants /m2), a certain height (15-20 cm) and a certain area (> 1000m2), and wind erosion can turn into sand-burying plants and fix sand dunes. The successful direct seeding plant varieties are mainly two pioneer plants of sand, namely Huabao and Yangchai. Can be broadcast, can also be broadcast in strips or holes.
Afforestation and sand fixation: in the flowing sand of arid grassland, appropriate deep planting and reasonable close planting are adopted to fix the sand. For example, in Dingbian Changmaotan Forest Farm, Artemisia ordosica is densely planted on sand dunes in autumn to survive and form sand barriers.
Cutting afforestation and sand fixation: In quicksand areas of Shaanxi and Ningxia, sand dunes are directly fixed with Salix cuttings. Yulin people adopt the way of cluster planting, forming a pattern of alternating density and density, which not only resists wind erosion but also solves the problem of water shortage. The row spacing between clusters is 0.5m× 1.5m, and each cluster contains 4-5 cuttings.
(4) Establish a shelter forest system in sandstorm area.
Oasis protection system in arid area: first, fences, shrubs and sand-fixing belts around the oasis; second, backbone sand-prevention belts; third, farmland forest network and other related forest species inside the oasis. The actual situation is much more complicated than the typical introduction, so it should be used flexibly according to the actual situation.
Sandy farmland shelterbelt: Semi-humid areas have more rainfall and better conditions, which can be dominated by trees. The main belt distance is about 350m, and the eastern part of semi-arid areas is slightly better, while the western part is on the edge of dry farming, with poor conditions and the most serious desertification. Generally, sandy grassland will not be eroded by wind, but large-scale dry farming and wind erosion need forest protection very much. Trees in the east can still grow, the height can reach 10m, and the main belt distance is 200 ~ 300m；. In the vast arid areas in the west, arbor forests can be planted in areas with good conditions, while drought-tolerant shrubs are the main ones in other areas, with the main belt distance of only about 50 m, and there are many sandstorms in arid areas, so small grid narrow forest belts are used. The main belt distance in northern Xinjiang is 170 ~ 250 m, and the auxiliary belt distance is1000 m; South Xinjiang is windy and dusty, with a grid of 250 m× 500 m; The front of sandstorm adopts (120 m ~ 150 m) × 500 m grid, and there are many tree species to choose from, mainly trees.
⑤ Sandy grassland shelterbelt
Construction technology of grazing forest: the selection of tree species should pay attention to feeding value, with arbor as the main species in the east and irrigation as the main species in the west. The main belt distance depends on the degree of sandstorm damage. The maximum protection distance can be 25 hours for those who are not serious, 15h for those who are serious, and10h for the grazing land of sick young girls. Sub-band spacing depends on the actual situation, generally 400 ~ 800 m, and there is no sub-band in mowing land. The main shrub belts are about 50m apart, the main forest belt is 10 ~ 20m, and the auxiliary belt is 7 ~ 10~20m. Considering that the grassland Guang Lin is few, dry and windy, in order to form a forest environment, the forest belt can be wider, with 6-8 rows of forest belts in the east and 4-6 rows of trees, and one row on each side is sparse. It is a sparse structure or ventilation structure without shrubs, and the biological fence should be compact. Afforestation density depends on water conditions, which can be higher in good conditions and lower in bad conditions.
(2) Engineering measures
Sand-blocking and sand-fixing: Using branches, firewood, straw, gravel, clay, slats, plastic plates and other similar materials, various obstacles are set on the sand surface to control the direction, speed and structure of wind-blown sand flow, so as to achieve the purpose of sand-fixing, sand-blocking, wind prevention and terrain change. Sand barriers play an important role, which cannot be replaced by biological measures.
According to the different principles and setting methods of sand prevention, sand barriers can be divided into two types: plane sand barriers and vertical sand barriers. The tiled sand barrier is a sand barrier, which uses straw, pebbles, clay and so on. Pave the sand surface in an omni-directional or banded way to isolate the contact between the wind and the sand surface, resulting in the effect of no sand without wind. Fixing quicksand in situ can protect plant growth, but it has little effect on sand retention in sandstorm flow. This measure has played an important role in the eastern region, affecting the water content in the western region, but it is beneficial to the improvement of sandy soil. A vertical sand barrier is a sand barrier. When the wind-blown sand flow encounters any vertical sand barrier, the wind speed will drop, and some sand particles carried by the wind will be deposited before and after the sand barrier, thus reducing the sand transport. Multiple rows of vertical sand barriers can fix the sand surface between sand barriers and intercept quicksand. Because most of the moving sand particles are within 30cm near the surface and within 10cm, it is unnecessary to set too high sand barriers to fix sand, control sand flow and prevent sand damage.
Chemical sand fixation measures: the diluted chemicals with a certain glue structure are sprayed on the surface of quicksand, and the water quickly penetrates downwards, while the chemicals are left in the cracks of the sand layer with a certain thickness (1 ~ 5 mm) to form a hard protective shell, thus enhancing the wind erosion resistance of the sand surface and achieving the purpose of sand fixation. At present, dozens of chemical sand-fixing materials have been developed, but they have not been popularized because of their high cost.
Wind-driven sand control: it is a sand control measure based on output, which reduces roughness, strengthens wind power, makes sand flow unsaturated, and produces sand pulling and surface wind erosion.
Agricultural measures: first, develop water conservancy, expand irrigation area, increase fertilizer and improve soil; Second, measures to prevent wind erosion and dry farming, such as strip farming, intertillage and planting tall crops.