Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Climate change is shifting the growing seasons of plants, affecting species performance and biogeochemical cycles. Yet how the timing of autumn leaf senescence in Northern Hemisphere forests will change remains uncertain. Using satellite, ground, carbon flux, and experimental data, we show that early-season and late-season warming have opposite effects on leaf senescence, with a reversal occurring after the year's longest day (the summer solstice). Across 84% of the northern forest area, increased temperature and vegetation activity before the solstice led to an earlier senescence onset of, on average, 1.9 +/- 0.1 days per degrees C, whereas warmer post-solstice temperatures extended senescence duration by 2.6 +/- 0.1 days per degrees C. The current trajectories toward an earlier onset and slowed progression of senescence affect Northern Hemisphere-wide trends in growing-season length and forest productivity.

Automated summary

Climate change is altering the growing seasons of plants, affecting species performance and biogeochemical cycles. The timing of autumn leaf senescence in Northern Hemisphere forests is uncertain, but early-season and late-season warming have opposite effects on leaf senescence, with a reversal occurring after the summer solstice. Increased temperature and vegetation activity before the solstice led to an earlier senescence onset, while warmer post-solstice temperatures extended senescence duration. These changes in leaf senescence can impact growing-season length and forest productivity in the Northern Hemisphere.