Enhanced vegetation productivity driven primarily by rate not duration of carbon uptake

Abstract

Climate change is altering both the duration and the rate of carbon uptake in plants, thereby affecting terrestrial gross primary productivity (GPP). However, little is known about the relative strengths of these processes or underlying mechanisms. Here, using satellite and carbon-flux data, we show that the duration and mean daily rate of carbon uptake (GPP_rate) have both increased in recent decades, enhancing total GPP with a rate of ~0.56% per year during the growing season across the Northern Hemisphere. Notably, the mean daily GPP_rate, driven primarily by rising CO₂ concentrations and temperatures, contributed ~65% to the changes in total GPP during the growing season over time, with higher contributions in early season (~83%) compared with late season (~55%). These findings highlight the importance of vegetation physiology in driving temporal changes in terrestrial GPP and suggest that the asymmetric changes in productivity across seasons will exacerbate under ongoing climate change.