Abstract: Since the start of returning cropland to forest and grassland project, vegetation in the Loess Plateau has grown rapidly. To clarify the vegetation variation and change trends in this region, trend analysis, standard deviation analysis, and Hurst index were applied to analyze the MODIS 250 m resolution NDVI in Yulin from 2000 to 2017. The NDVI was increased by 88.56% from 2000 to 2017, with an annual rate of 4.92%. The NDVI of cultivated land, woodland, grassland and unused land were all obviously increased. The NDVI in different elevations and slope ranges also increased significantly. NDVI was positively correlated with rainfall but not with temperature. Increased grain yield, the total number of domestic animals, and the total area of returning cropland to forest and grassland had a significant correlation with NDVI, suggesting that after the transformation and upgrading of agricultural production, ecological environment governance and rural economy had achieved coordinated development. According to the forecast results of Hurst index, the returning cropland to forest and grassland project in this area was close to its carrying potential, but NDVI index had about 10% growth potential. In the extreme drought years of future, vegetation would experience the threat of droughtinduced death and the risk of NDVI index reduction, mainly concentrated in the hilly and gully areas with better NDVI recovery. In the period of after returning cropland to forest and grassland, it is an important task to coordinate the rational allocation of soil and water resources for realizing ecological construction in this area.

Key words: southeast Pacific, longline, bycatch, vertical distribution.