| widely Referring to information about environment, vegetation, ecology , human activity and so on, the vegetation backgrounds and vegetation succession in Northwest China were studied by delving, deeply analyzing, consideration and scientific reasoning.1 .Study on environment related to vegetationThe paper discussed factors which is closely related to vegetation, such ad environment backgrounds, geology backgrounds and earth tectonic, physiognomy traits and its unit, climate, hydrogeology, agrotype and so on.Factors affecting vegetation were induced to geographic position, climate, terrain and physiognomy, soil and human activities. Influences of human activities on vegetation were generalized five parts, i.e. farming, reclamation, exploitation, manufacture, and human livings. The arid also points out that human farming actions is in places of better water, quantity of heat and soil conditions, where environment rehabilitation ability is better; reclamation action is in places of bad conditions of water and quantity of heat, or rough or steep terrain, or soil difficult to cultivation, where environment rehabilitation ability is bad and humane actions have deep influences on mature ecosystem; mining action is in any places of valuable resources of energy, minerals, medicinal materials and fuel etc., which can be demanded and be acquired by people; manufacturing actions is in all places of industrial production; influences of human livings on vegetation represents contest for living essentials in living space, especially obvious in the region of arid hungriness for water resources.Vicissitude of human factors affecting vegetation concludes flux of population quantity, population distribution in space, science and technology mastered by people and human demands. Flux of population quantity includes population increase as improving of medical treatment and living conditions, and population reduction as battle and murrain. Flux of population distribution in space includes migration from backland to border land, from border land to backland, from South to North and from North to South for some reasons. Flux of science and technology mastered by people represents people wisdom development in the process of continually science exploring and technology innovating, which are applied to every walk of life, such as agriculture, industry and mining etc. Flux of human demands refers to increasingly people demands including in continually city what scale enlargement, improvement of habitation conditions and additional facilities increase, all of which makes natural vegetation previous change to agriculture vegetation, further, to sparse vegetation or to concrete construction without vegetation.2. Study on vegetation type in Northwest China.The vegetation was classified into nine vegetation-type groups, 20 vegetation-types, 37 vegetation subtypes and 86 formation groups in Northwest China, through statistic, analyse and classification for vegetation in Northwest China according to principles of vegetation classification generally adopted by botanist. All of the vegetation and their distribution were showed with tabulation, which are visual, legible and convenient.3. Study on effect of natural vegetatin and agriculture vegetation to environment in Northwest China.The article analyzes effect of natural vegetation and agriculture vegetation to environment in Northwest China from three aspects, viz cover area, soil prehension and consumption for living essentials in space . Assuming cover rate of natural vegetation is regard as 1, the study shows that cover rate of agriculture vegetation is from 0.22 to 1 in the same places according to planting modes in Northwest China. Effect of agriculture vegetation on soil prehension are distinctly less than those of natural vegetation. Consumption of living essentials of agriculture vegetation exceeds that of natural vegetation, especially more badly in hungriness and campo areas in Northwest China.Agriculture vegetation is divided 3 groups, 6 types, 13 combinati...
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