| The Loess Plateau is located in the transitional zone of China’s forest-grassland, once there ecology is good, and is very suitable for agriculture production with fertile soil.But due to the continuing interference of human activity, it has became one of the most serious situation areas of China’s agriculture ecology, income of peasants is very low, therefore, which caused agriculture, rural areas and farmers problems. The natural condition of Loess Plateau give the possibility to produce a variety of agricultural structure, and it is a good place to verify ecological and productive function of different agricultural structure as well. This paper mainly discusses the whole process of agro-grassland and cropland-agriculture occurrence and development in Loess Plateau through the historical research ways, meanwhile, strategic conception of agriculture system which based on agricultural structure improving is carried out. The results show that:(1) The natural ecosystem of loess plateau mainly is grassland, for this reason, its agriculture system showed characteristics of grassland agriculture. The origin sequence of agriculture is the agro-grassland appeared first and cropland-agriculture followed through archaeological discovery.(2) The replacement of the two kinds of agricultural structure is the main history of agricultural structure in the Loess Plateau. Agro-grassland occupied the main position at the historical stage of Prehistoric Times, Xia, Shang and Western Zhou Dynasties, the Eastern Han Dynasty to the Northern and Southern Dynasties, Song and Yuan Dynasties. And the cropland-agriculture was the main agricultural structure at the historical stage of Spring and Autumn Period and the Warring States Period, the Qin Dynasty and the Han Dynasty, the period since Ming and Qing Dynasties. On the other hand, harmonious coexistence of both the agricultural structure was appeared in Sui and Tang Dynasties.(3) The main reason for changing of agricultural structure is cultural influence. Agricultural structure conversion of different agricultural structure embodied in species of crops, livestocks, ways of land use, etc., and which affected the function of agricultural ecosystem.(4) The ecological indicators such as vegetation conditions, agricultural disasters and soil loss are significantly better at the historical stages of agro-grassland than cropland-agriculture through the analysis of the agriculture system in Loess Plateau based on historical data. Some scientific experiments also show that grassland agriculture has more significant effect of ecological protection and economic gain. Combined with the results of two aspects, the grassland agriculture should be the main agricultural structure for Loess Plateau at present.(5) Strategic conception of agriculture system in Loess Plateau is given based on the grassland agriculture structure, which reflects the vegetation types generated from the Comprehensive and Sequential Classification System of Rangeland(CSCS). The scheme contains three strategic development zone which are composite agriculture area, cultivated grassland agriculture area and grazing grassland agriculture area. The composite agriculture area can develops grain production and forestry production, and should pay attention to the grain-grass rotation and tree-grass intercropping at the same time. The cultivated grassland agriculture area can become a modern animal husbandry base by planting grass in arable land. At last, grazing grassland agriculture area should appropriately used as grazing field to protect native vegetation.
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