Fig. 4 Relationships among plant biomass, plant growth, and phenology. Blue lines represent the significant positive correlations, red lines represent the significant negative correlations, blue boxes represent significantly increased trends over time, red lines represent significantly decreased trends over time, the dashed line represents non-significant correlations, the dashed boxes represent non-significant trends over time. The number in the middle of the line represents Pearson’s correlation coefficient and optimal daylength threshold.