The effect of meteorological drought on vegetation cover in the Yellow River basin, China

As a widespread natural disaster, drought has a significant impact on changes in regional vegetation cover. Based on 1-month standardized precipitation index (SPI1), this study took the Yellow River basin (YRB) with frequent droughts as the research object, using NDVI data from 1999 to 2018, Mann-Kendall trend test, and correlation test to study the temporal and spatial characteristics of meteorological drought, explored the response of vegetation cover to meteorological drought, and further discussed the possible factors affecting meteorological drought. The results of the study showed that from 1999 to 2018, the SPI1 in the YRB had not increased significantly in a large area in different months (p > .05). On the monthly time scale, the NDVI of the YRB gradually increased from north to south, showing a significant increasing trend the central area (p < .05). And in the summer months, there was a significant positive correlation between SPI1 and NDVI in some areas (p < .05). In the meantime, sunspots, ENSO, and PDO had significant effects on the SPI1 in the YRB (p < 0.05). Furthermore, in areas with frequent extreme droughts, the average value of NDVI was high, which was mainly because the area was in a cultivated vegetation area with a wide-scale policy of returning farmland to forest and afforestation activities. Returning farmland to forests and afforestation activities will help overcome the impact of meteorological drought and other adverse conditions on vegetation. Therefore, returning farmland to forests can be implemented for ecological restoration in arid areas in the YRB.