Fig. 5: Conceptual summary of the driving mechanisms of the peak of the growing season (POS) timing across the Northern Hemisphere. | Communications Earth & Environment

Fig. 5: Conceptual summary of the driving mechanisms of the peak of the growing season (POS) timing across the Northern Hemisphere.

From: Increased early-season productivity drives earlier peak of vegetation photosynthesis across the Northern Hemisphere

Fig. 5

Potential mechanisms underpinning the changes in POS timing include (1) climate and soil moisture conditions during the early growing season (early-season environmental effects), (2) SOS and early-season GPP effects (intrinsic developmental effects), and (3) climate and soil moisture conditions during the late peak season (late peak season environmental effects), such as soil moisture deficit legacies from earlier in the season or heat stress due to climatic warming (A). Early-season GPP was the strongest driver of POS, with increased early-season GPP leading to earlier POS in more than 93% of the studied areas (Fig. 2A–D). SEMs and variation partitioning analysis indicate that intrinsic developmental effects (GPP and SOS) and early-season temperature, rather than late-peak-season environmental effects, drive the variations in POS timing (Figs. 4, S22). SOS and early-season temperature indirectly affected POS timing by influencing early-season GPP (B), suggesting that early-season plant activity controls POS timing through effects on plant source and sink dynamics.

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