Fig. 1: Schematic representation of the seasonal greenness trajectory scenarios that capture the strength and directions from enhanced early- and peak-season greenness to late-season greenness.

Warming and CO₂ stimulate enhanced vegetation greenness during the early- and peak- growing season, which can persist into the late growing season through amplifying effects (green line). Alternatively, the increased greenness observed in the early and peak seasons could be inhibited or even reversed in the late season (weak/strong stabilization scenarios, indicated by the orange line). This may result from intrinsic phenological and life history limitations, seasonal climate anomalies, or accumulated soil moisture deficits caused by the intensified greenness in the early-and peak-seasons, which could deplete soil moisture due to enhanced evapotranspiration (ET). The symbols − and + in each bracket represent either a negative or positive effect, respectively, on terrestrial vegetation greenness. Trees icons were designed by and sourced from Vecteezy.com under a Free License: https://www.vecteezy.com/vector-art/8334831-isolated-trees-and-nature-objects-set zheli.