Vegetation dynamics and phenological shifts in long-term NDVI time series in inner Mongolia, China

Abstract

To assess the dynamics of vegetation growth and phenology in the Inner Mongolia Autonomous Region in China, a time series of Normalized Difference Vegetation Index (NDVI) data from 1983 to 2013, derived from the Advanced Very High-Resolution Radiometer-Vegetation Health Product (AVHRR-VHP), was applied to detect linear trends, seasonal phenology transition dates, and growing seasons. Overall, Inner Mongolia became warmer and drier during the study period. A significant increasing cumulative NDVI trend was found for 30.30% of the total vegetation covered area. The restored area was mainly in the western desert steppe. The degraded area was primarily located in the northeastern meadow and typical steppe regions. However, a severe drought was delected during 1993-2003, when approximately 27.56% of the total vegetation covered area experienced a significant decreasing NDVI trend. The length of the growing season (LOS) during 1983-2013 was shortened due to the delayed start of the growing season (SOS) and advanced timing of the end of the growing season (EOS). However, this trend was reversed during the more recent decade (2003-2013). The phenology was closely associated with climate change, especially precipitation. The variability of vegetation responses to climate change was also assessed, indicating that most types of vegetation had recently recovered and that the restored areas had a varied spatial distribution.