Abstract: [Objective]The purpose of this article is to explore the characteristics of temporal and spatial dynamic changes of vegetation coverage within Pisha sandstone area in Loess Plateau, to analyze the impact of the normalized difference vegetation index (NDVI) under different land use patterns,to discuss the spatial and time-delay relationship between vegetation coverage and hydrothermal factors. It provides ideas for the restoration and reconstruction of degraded vegetation within Pisha sandstone area in the Loess Plateau and the comprehensive management of the coarse sediment of the Yellow River. And it is beneficial to improving local living conditions and ecological environment in the Pisha sandstone area.[Method]Huangfuchuan basin was chosen as the study area, and a total of 192 MODIS13Q1 products between 2000-2015 were used to obtain NDVI values based on ENVI technique. Characteristics of NDVI in temporal dynamics and spatial distribution were investigated with methods of univariate linear Regression (ULR) and Spearman correlation analysis. Spatiotemporal characteristics under different land use types, the resolution of which is 30 m, was statistically analyzed and the responses of vegetation coverage to changes of precipitation and temperature factors during growing season was further emphasized.[Result]The average NDVI value of Huangfuchuan basin is ranged between 0.429 and 0.630, showing a linear increasing trend. The growth rate is 0.004 2·a^-1. Significant difference between the growing and non-growing seasons was detected, and the maximum value appeared in May. The temperature and precipitation also showed an increasing tendency with growth rates of 0.034 8℃·a^-1 and 6.27 mm·a^-1, respectively. Spatially, the NDVI values range between 0.1-0.3 in subbasin of Nalin, and in the range of 0.25-0.4 within subbasin of Shilichangchuan. The vegetation shows a spatial pattern of "high in gully and low on slope" in two subbasins. The NDVI values of different land types were all between 0.2-0.25. The NDVI values in different land use types ranked as forest > cultivated land > grassland > unused land. The growth rate in past 16 years ranked as grassland > unused land > forest > cultivated land. For tributary of Nalin, NDVI near the gully decreased by -0.09-0, while NDVI on slopes far away from the gully increased by 0-0.12. For tributary of Shilichangchuan, NDVI near the gully increased by 0-0.4 while by 0.04-0.12 on slopes. Over the whole basin, variation tendency of vegetation cover shows a spatial increase pattern of "very significant on slope surface nearly significant in the vicinity of gully,non-significant in gully ". During the past 16 years, there was no significant correlation between NDVI and temperature in the growing season. The correlation coefficient between precipitation and NDVI was -0.41~0.87. Compared with the vegetation near the gully, vegetation on the slope was more susceptible to precipitation. Vegetation has 1-year (P=0.036<0.05) and 1-month (P=0.001<0.01) lag time for precipitation, and 2-month (P=0.002<0.01) lag time for temperature.[Conclusion]Temporally, NDVI in Huangfuchuan basin showed a significant decreasing trend of fluctuations, and obvious distinction was detected between the growing season and non-growing season. Spatially, in accordance with the gully-slope distribution, the gully showed high NDVI but low increasing rate and even appeared the phenomenon of degradation; meanwhile, the slopes showed low NDVI but high increasing rate. NDVI with land use types of forest and grassland increased the most, indicating the validity of the returning farmland to forest projects. The correlation between vegetation and precipitation is high, and there is a certain lag.

Key words: spatiotemporal heterogeneity, NDVI, precipitation, temperature, Huangfuchuan basin