Fig. 5
Threshold of the ICE-driven NDVI and GPP variation (\(\Delta {NDVI}_{ICE}\) and \(\Delta {GPP}_{ICE}\)) outpace that of eCO2. ICE proportion is the percentage of the change of irrigated cropland area to total vegetation area. a Relationship of the \(\Delta {NDVI}_{ICE}\) and ICE proportion. b Relationship of the \(\Delta {GPP}_{ICE}\) and ICE proportion. The shaded areas represent the 95% confidence intervals of the fitted curves. The red dots in the figure represent ICE proportion and \(\Delta {NDVI}_{ICE}\) (\(\Delta {GPP}_{ICE}\)) of different 0.75° grids in the region. The green dots represent ICE proportion and \(\Delta {NDVI}_{ICE}\) (\(\Delta {GPP}_{ICE}\)) between 1982 and 2018 in the whole region. The “ + ” represent ICE proportion and \(\Delta {NDVI}_{ICE}\) (\(\Delta {GPP}_{ICE}\)) between 1995 and 2018 in the whole region