Rising atmospheric CO₂ explains 26–52% of the recent delay in autumnal senescence in important forest and crop species

Abstract

There is strong evidence to suggest that global warming is leading to an extended growing season by altering the timing of autumnal events such as bud set and leaf abscission 1,2,3, with important impacts on ecosystem productivity and global carbon cycling. However, while temperature is an important driver of spring phenological events, the relationship between temperature and autumn phenology is weak4. Here, we present results from three open-air field experiments in which elevated atmospheric CO2 concentration [CO2] at the concentration likely to exist in 2050, extended the growing season of: (1) three abundant North American forest trees; (2) the world’s most extensively grown broad-leaved crop (soybean); and (3) two European poplars. Across experiments and over multiple years, elevated [CO2] delayed autumnal declines in leaf area, chlorophyll concentration, photosynthesis and normalized vegetation difference index (NVDI) by 2-7 days for soybean and 5-15 days for trees. These findings indicate that [CO2] alters growing season length and the rise in atmospheric [CO2] over the past 30 years could explain 26-52% of the extended growing season now ascribed to warming3