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

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Description/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
abscission1,2,3, 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.