Spatiotemporal variations of NDVI of different land cover types on the Loess Plateau from 2000 to 2016

Understanding the spatial-temporal changes of vegetation and future trends of spatial pattern is of great significance to regional environmental protection and ecological construction. In order to understand the vegetation changes on the Loess Plateau after the implementation of the Grain for Green Project, the spatial-temporal variation characteristics of annual maximum Normalized Difference Vegetation Index (NDVI) (NDVI ymax ) and growing seasonal mean NDVI (NDVI gsmean ) were analyzed based on MOD13A1 data for the Loess Plateau during 2000-2016, supplemented by Sen+Mann-Kendall, coefficient of variation, and Hurst index analysis. The results indicate that: 1) NDVI ymax and NDVI gsmean showed a fluctuating growth trend from 2000 to 2016, with growth rates of 0.0070/a ( *P* <0.01) and 0.0063/a ( *P* <0.01), respectively, and the ecological environment improved continuously. 2) NDVI ymax and NDVI gsmean showed that the area of vegetation coverage on the Loess Plateau with increasing trend were much higher than that with decreasing trend (93.42% and 96.22% versus 6.58% and 3.78%). This means that vegetation coverage was improving. With regard to the trends of change of the two evaluation indices, the performance of different land cover types slightly differed. The area of forest with most significant increasing trend was 73.02% and 82.60%, followed by cultivated land (47.87% and 67.43%) and bare land (47.03% and 61.68%). The coefficient of variation of NDVI gsmean was smaller than that of NDVI ymax , and the stable area was 63.31% and 56.64%, respectively. Of the two evaluation indices, the coefficient of variation of forest was the smallest, representing the best stability. According to the coupling results of NDVI and Hurst index, the areas with increasing trend of NDVI ymax account for 41.35%, and the areas with degrading trend account for 58.65% of the total area in the future. The areas with increasing trend of NDVI gsmean account for 49.19%, and the areas with degrading trend account for 50.81% of the total area. The two evaluation indices show that shrubland has the best growth trend. The areas of forest and cultivated land with degrading trend would be greater than 50%. The vegetation status in the areas of unsustainable increase and sustainable degradation need continuous attention of researchers.