Increased drought effects on the phenology of autumn leaf senescence

Global warming delays the autumn date of foliar senescence (DFS) in recent decades, with positive implications for growing season length and therefore global carbon storage. However, warming-associated drought, leading to water limitation, may conversely stimulate earlier DFS. Using ground observations since 1940s and 34 years of satellite greenness data (1982-2015) over the Northern Hemisphere (>30 degrees N), we show the increased impact of drought on DFS. Earlier DFS is linked to decreased precipitation under warming and weaker drought resistance associated with various plant functional traits. For example, isohydric plants with strict regulation of water status may drop leaves fast during droughts. We derive an improved set of phenology models based on this influence and project earlier DFS by the end of the century, particularly at high latitudes (>50 degrees N). Our results limit uncertainties in the later end of plant growth with warming, aiding estimation of carbon uptake of terrestrial ecosystems.

Automated summary

Global warming has delayed the autumn date of foliar senescence (DFS) in recent decades, which has positive implications for growing season length and global carbon storage. However, warming-associated drought may stimulate earlier DFS due to water limitation. This study uses ground observations and satellite data to show the increased impact of drought on DFS, linking it to decreased precipitation under warming and weaker drought resistance in plants with different functional traits. An improved set of phenology models based on these findings suggests earlier DFS by the end of the century, especially in high latitude areas.