The paired t-test on temporal trends of heat degree days (HDD) driven by different influencing factors in each sub-region.

Tr.ave, Trmxt.ave and Trphe.ave are the average value of regression coefficients at all stations of each sub-region. S-NMLYtz, single-season rice sub-region in the northern Middle and Lower Reaches of Yangtze River; S-SWP, single-season rice sub-region in Southwest Plateau; DE-SMLYtz, double-season early rice sub-region in the southern Middle and Lower Reaches of Yangtze River; DE-SC, double-season early rice sub-region in Southern China. SR, single-season rice region; DER, double-season early rice region.*, significant at p **, significant at p The paired t-test on temporal trends of heat degree days (HDD) driven by different influencing factors in each sub-region.