In a warming environment, spring continues to get earlier. However, the timing of autumn leaf fall has been more of a mystery. Interestingly, a concentrate by specialists remembering scholar Susanne Renner for Expressions and Sciences at Washington College in St. Louis addresses this secret by uncovering the significant job of the mid-year solstice.
A review distributed in Science shows that warming before the solstice sets off a prior beginning of leaf senescence — the cycle through which plants separate and reabsorb key supplements that had been conveyed in leaves — and declining photosynthesis, while warming that happens after the solstice dials back the leaf staining process.
While warming happens before the late spring solstice, fall begins prior because of sped-up occasional cycles in trees, the specialists found. On the other hand, late warming makes autumn last longer, which causes leaves to fall later. Overall, every degree Celsius (or 1.8°F) of pre-solstice warming advances the beginning of leaf senescence by 1.9 days, while every degree Celsius of post-solstice warming expands the senescence cycle by 2.6 days.
The researchers said that the switch in impacts is a developmental variation that permits trees to synchronize their development rhythms with the changing day length.
More information: Constantin M. Zohner et al, Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice, Science (2023). DOI: 10.1126/science.adf5098
