Natural disasters (high school geography knowledge)

☆ Diseases Common crop diseases include rice blast, wheat rust, cotton wilt and tobacco anthracnose. Common forest diseases are: poplar bark rot, pine blister rust, leaf melting disease, paulownia witches' broom disease and so on. Causes of diseases: A. The adverse environment caused by climate variation reduces the resistance of crops to diseases. B. the invasion of foreign pathogens is also the main cause of disease epidemic. Harmful diseases cause crops and trees to wither or even die, resulting in the destruction of large areas of farmland and forests. Not only caused a large area of crop production reduction, or even no harvest; It also leads to large-scale deterioration of agricultural products, causing serious economic losses. There are many kinds of crop diseases and insect pests in China, and the harm in the east is greater than that in the west. Several diseases and insect pests that are most harmful to crops and their distribution ① Wheat rust (including stripe rust, leaf rust and stem rust) is the most widely distributed and seriously harmful wheat disease in China, which occurs in all wheat areas. ② Rice diseases: mainly distributed in the rice producing areas south of Qinling-Huaihe River ③ Helicoverpa armigera: widely distributed in China's cotton producing areas (especially in the Yellow River basin and Xinjiang cotton producing areas). The control measures include killing drugs, introducing natural enemies, artificial trapping, strengthening quarantine, and preventing pests from entering the country ☆ Pests ☆ Common crop pests include locusts, armyworms, borers, cotton bollworms, etc. Among them, locusts are the most harmful. Common forest pests include pine wood nematode, Dendrolimus punctatus, poplar stem borer and paulownia moth. Among them, Bursaphelenchus xylophilus is the most dangerous forest pest in the world and is listed as the main quarantine object at home and abroad. The harm of forest diseases and insect pests leads to the decrease of forest growth and forest death, which not only causes great losses to China's forestry, but also causes serious damage to forest ecological functions. There are many kinds of crop diseases and insect pests in China, and the harm in the east is greater than that in the west. Dendrolimus punctatus, the main forest pest in China. Frequent areas: areas below 400 meters above sea level with an average temperature above 25℃. The area with an altitude of 400-500m and a temperature of 10-25℃ is the main man-made reason for the frequent occurrence of forest diseases and insect pests. A large number of single plantations have replaced primitive forests with rich species diversity, which has reduced the self-control ability of forests to pests. Prevention and control measures: pesticides, natural enemies, artificial trapping, strengthening quarantine, and preventing pests from entering the country. The concept of sandstorm sandstorm is the general name of sandstorm and sandstorm; It refers to a weather phenomenon that strong winds throw a lot of dust on the ground into the air, which makes the air particularly turbid and the horizontal visibility is lower than 1 km. The basic condition of occurrence time in winter and spring is strong wind, which is the dynamic condition of sandstorm formation; The second is the dust material on the ground-the material conditions for the formation of dust storms; The third is the unstable air state and the thermal conditions in some areas. The basic reason for the formation (used to answer questions) (1) Every March to April, North China is affected by the cold air coming in and out of Siberia, with windy weather. (2) At this time, the vegetation was born, and the influence of spring drought on the restoration of natural vegetation could not completely cover the ground. (3) At this time, the surface has been thawed, and the temperature rise in spring accelerates the surface drought. Dry and loose ground materials are easily lifted by strong winds, forming sandstorm weather. (answer to the college entrance examination: sandstorms are mainly concentrated in (late winter and) spring (February, March, April and May). Rapid warming, loose topsoil (surface) (and sparse vegetation), less precipitation and more windy weather. The main distribution areas are North China, Northwest China and Northeast China (especially in arid and semi-arid areas), which significantly reduces visibility and affects traffic and human health. Defense measures, protect forests and grasslands, return farmland to forests, grasslands and grazing, and prohibit excessive reclamation, deforestation and overgrazing, planting trees and restoring vegetation. Three. Distribution, causes and prevention measures of major environmental problems in the monsoon region of eastern China: the causes of regional problems; Control measures of black soil loss in northeast plain: long-term unreasonable reclamation; Returning farmland to forest and grassland; Stop reclamation of marshlands in the North China Plain (refer to the elective course 5P52: "Figure 2.36" for the areas prone to meteorological disasters); The total precipitation in spring drought is less; The seasonal distribution of precipitation is uneven, and the surface runoff is less; The temperature rises rapidly in spring; Less precipitation and vigorous evaporation; Dense population, dense cities and much domestic water; The country's main agricultural commodity production base uses a lot of irrigation water; Comprehensive industrial base, industrial water, etc. ; It is also manifested as water shortage, that is, domestic sewage, industrial sewage, agricultural pesticide and fertilizer sewage, seawater intrusion and a series of polluted water. (serious water pollution and serious waste) repairing reservoirs; Save water and develop water-saving agriculture; The precipitation of pumping wells is concentrated in summer floods; The plain area is low and flat; Soil erosion, river bed elevation in the middle and lower reaches of rivers and flood storage in reservoirs; Soil erosion control in the Loess Plateau; Reinforce dikes, dig new rivers and seas, accumulate water in saline-alkali low-lying areas and have poor drainage; Uneven drought and flood; Flooding, only irrigation without drainage, groundwater rising (see compulsory 3P22 Reading for the principle) and neutralization of acidic substances; Save words, control the movement of water and salt, and desalt the soil; Improve the soil in spring, the wind and sand will heat up quickly, and the precipitation in spring will be less; The wind in winter is still very strong; Land desertification is serious (see "Sandstorm" on the previous page). Returning farmland to forests, grasslands and grazing are prohibited. It is forbidden to plant trees, build shelter forests and restore vegetation. Soil and water loss is serious in the hilly area of the south of the Yangtze River on the Loess Plateau. Summer rainfall is concentrated, loess soil is loose, vertical joints are developed, vegetation is sparse, and unreasonable farming system (such as crop rotation shortage) is adopted to start mining; Hilly mountainous areas (hilly areas in the south of the Yangtze River) are characterized by large topographic relief, concentrated precipitation, heavy rainfall, thin soil layer in hilly areas, long-term deforestation and sparse vegetation. (Loess Plateau) Damming, leveling land, planting trees and grass, soil and water conservation, returning farmland to forests and grasslands, and developing ecological agriculture; (Hilly areas in the south of the Yangtze River) Develop three-dimensional agriculture of "grass on hills, pond between hills, fish and fruit on gentle slopes" and land use structure with fruit as the main part, plant trees, close hillsides to facilitate afforestation, conserve water and soil, and solve the problem of farmers' living energy consumption through various channels according to local conditions. (such as coal, wood-saving stoves, biogas and firewood forests). The flood terrain in the middle and lower reaches of the Yangtze River and Huaihe River basin is low and flat; Precipitation concentration; Serious soil erosion, sediment deposition in rivers and lakes; Reclaiming land from lakes (see P3 "Causes of Frequent Hydrological Disasters in the Middle and Lower Reaches of the Yangtze River in China" for details): building shelterbelts in the upper reaches of the Yangtze River to maintain water and soil; strengthening dikes and dredging rivers in the middle and lower reaches; Returning farmland to lake water pollutes people and cities, and a large number of industrial and agricultural sewage and wastewater are discharged at will to improve people's awareness of environmental protection; Improve laws and regulations, comprehensively control red soil with low organic matter, strong acidity, high soil viscosity, high temperature and rapid decomposition of organic matter in low mountains and hills in the south of the Yangtze River; In case of heavy precipitation and nutrient leaching, more hydrated lime and organic fertilizer should be applied to improve soil acidity; Add more sand to reduce viscosity; Planting tea trees, camellia oleifera, Chinese fir, masson pine and other economic trees, restraining soil erosion, and strengthening the forecast of special coastal shelterbelts with strong development of typhoons and tropical cyclones in the eastern coast of the North Pacific. Four. Distribution of causes, consequences and preventive measures of major environmental problems, preventive measures of regional causes and consequences, greenhouse effect, and a large amount of CO2 gas emitted by burning fossil fuels in the world; Deforestation, global warming, rising sea level and inundation of coastal lowlands; Global evaporation is more vigorous, and the area of arid climate area is expanded to use clean energy; Improve energy efficiency; Carry out cleaner production; Afforestation, greening the earth acid rain almost all over the world, metallurgy and burning fossil fuels emit acid gases such as SO2, forming pH.