Earlier spring onset and autumn warming increase the discrepancy between leaf coloration and photosynthetic cessation

Climate change is shifting the timing of autumnal phenology, with potentially different impacts on leaf coloration and photosynthetic cessation. Here we derive the end of the growing season across northern ecosystems from 2001 to 2021 using satellite-based measures of vegetation greenness, indicating leaf coloration, and solar-induced chlorophyll fluorescence, indicating photosynthetic activity. We examine temporal changes in the difference between these two metrics and the factors driving these trends. Leaf coloration generally occurred later than photosynthetic cessation, and the difference increased significantly over time. This growing discrepancy was primarily driven by earlier starts of the growing season and rising autumn temperatures. Earlier spring onset influenced autumn timing through its effects on peak growth timing and seasonal carbon uptake, with a stronger impact on photosynthetic cessation than on leaf coloration. Warmer autumn further increased the discrepancy by delaying both processes, slightly more for leaf coloration. This mismatch can intensify respiratory carbon loss, with implications for climate-adaptive forest management. Leaf coloration is found later than photosynthetic cessation in autumn across northern ecosystems, and the discrepancy grows from 2001 to 2021, which is primarily due to earlier starts of growing seasons and autumn warming, as revealed by remote sensing and climate data