| This experiments took in the Mizhi County in the first Deputy District of the Loess Plateau where soil erosion was serious a, and were made on distribution and migration of soil organic matter and Nitrogen under different vegetation in the restoration of artificial vegetation of degraded slope-land. Also we studied the effected of slope gradient, slope position and slope aspect on the areas of migration and enrichment of Total N and NO-3 -N under artificial locust forest, and the variation of migration of NO3- -N between farmland and Caragana land in the fertilization condition of the same slope gradients, slope positions and slope aspects. Based on the results, we evaluated the areas of migration and enrichment of soil nutrients and its effects in the restoration of artificial vegetation of the first Deputy District in order to provide theory and technique for the ecological environment construction in west China. The results show as follows:1. The difference of soil organic matter content under different vegetation was significant, the contents of organic matter under all broadleaf forest land and grassland were more than them in farmland, especially in 0-20cm soil layer, and that was most (4.84 g·kg-1) in Locust forest of the 12 different vegetation on the soil profile, Caragana, apricot and jujube took the second place. The average levels of organic matter under oriental arborvitae and Chinese pine forest were the minimum. The order of the soil organic matter is the locust> Caragana> apricot> jujube> grassland> Poplar> alfalfa> pear> potatoes> P. miliaceum> Chinese pine> oriental arborvitae. That showed broad-leaved forest contributed to organic matter more than farmland, and farmland contributed to organic matter more than coniferous forest.The organic matter contents of different slope position under the same vegetation were different obviously; and all dates showed the trend organic matter in the foot> in the top> in the middle, this showed the migration of organic matter of slope land on the Loess Plateau was ubiquity, and organic matter had a trend of migration in soil surface, and its direction of migration was from the top to the foot, but the intensity of the migration in the top was less than that in the middle. The migration of soil organic matter was different obviously due to different vegetation types, the migration intensity of Caragana was less than that in the locust, and that in the Locust was less than that in the apricot.2. Under different vegetation the total nitrogen contents vary significantly in soil profile, and they reduced gradually along the vertical direction. The decrement varied due to different vegetation, the nitrogen content in the 0-20cm soil layer in the Peashrub was the largest among the 12 plants. The order of the nitrogen content of the other vegetation was Caragana> Locust> Yang Tree> apricot> potatoes> grassland> oriental arborvitae> pear> jujube> alfalfa> Chinese Pine. The order of the total nitrogen content in of 0-100 cm soil layer different slope position in the same vegetation were in the foot>in the top>in the middle. This showed that the soil total nitrogen was easily lost in the top and in the middle, and enriched in the foot of slope.3. The nitrate nitrogen contents of the soils in degraded slope-land were increased from the top to the foot and the content of nitrate nitrogen in the foot were much higher than them in the top and the middle. The nitrate nitrogen contents in 0-20cm surface layer in the foot of locust was 5.44 mg·kg-1, in the middle was 3.23 mg·kg-1, in the top was 4.44 mg·kg-1, and them in the foot was 68.4% higher than them in the middle, and 22.5% higher than them in the top, that showed movement of nitrate in the area was extremely active. The migration of soil nitrate was related with the slope aspect and slope gradient. The nitrate contents of 0-200cm soil layers in shady slope were 1.55 times as the sunny slope; the slope gradient was greater, the migration was more active.4. Fertilization experiments showed that the migration of NO-3 -N was very active, and its annual migration in the slope was up to 1.5-2m, vertical migration was 60-80cm. When the level of fertilization was more than the absorption of vegetation, the nitrate nitrogen would enrich in the foot of slope gradually. The migration of nitrate nitrogen under artificial Caragana forest was smaller clearly than that under farmland, so we should avoid the migration of NO-3 -N,prevent river water nutritious in the returning land for farming to forestry and fertilization.
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