Abstract
Understanding vegetation evaluation is critical for exploring changes in
terrestrial ecosystems and identifying upcoming challenges. However,
analyses that simultaneously examine abrupt changes in vegetation
greenness at the national, regional, biome and pixel scales in China are
still rare. Using long-term (1982–2015) satellite time series data in
conjunction with the Breaks for Additive Season and Trend (BFAST)
technique, we identified breakpoints in the Normalized Difference
Vegetation Index (NDVI) in China. Results showed that the annual mean
NDVI gradually increased during the 34-year period. 68.8% of the
vegetated area exhibited upward trends in NDVI, most of which was
distributed in Southeast China and the Loess Plateau. Changes in NDVI
trends occurred in 78.7% of the total vegetated areas, while hotspots
were concentrated in Northwest and North China. A rapid increase in
breakpoints was detected after 1999, mainly concentrated in North and
Northwest China, and corresponding to the times and areas with the
highest ecological engineering efforts. Positive shifts in NDVI trends
were more common and generally distributed on the eastern side of the Hu
Huanyong line, while browning (negative) shifts were mainly distributed
on the western side and were gradually expanding, indicating a possible
tendency towards environmental degradation. Although unstable vegetation
areas had higher frequencies of breakpoints, the proportion of stable
vegetation experiencing NDVI trend shifts was higher after 2000,
probably because human intervention buffered external disturbances in
unstable areas. Identifying hotspot areas of shifts in vegetation
greenness can provide scientific reference for sustainable land
development and carbon neutrality target achievements.