Sugar Poisons Leaves?

By Richard B. Primack

“In my experience I have found nothing so truly impoverishing as what is called wealth.” 

- Henry David Thoreau in his Journal. 

An innovative recent article in Science proposes that earlier leaf senescence of trees in autumn is promoted by summer condition of high light and warm temperature that favor high levels of photosynthesis.   According to this hypothesis, rapidly photosynthesizing leaves will accumulate sugar in their leaves and deplete nitrogen reserves,  promoting early leaf senescence. This early leaf senescence caused by high levels of summer photosynthesis will tend to cancel the later autumn leaf senescence caused by warmer autumn conditions associated with climate change.  

During sunny dry conditions in Boston, black birch leaves undergo leaf senescence in August. 

This study raises several key questions.  Is their “poison sugar hypothesis” a widely applicable result, or just another additional factor that contributes to variation in leaf senescence?  How can we be sure that their result is really due to high photosynthetic rate and not just due to the well-known effects of  summer drought stress? And finally, do their results apply to other species and other places?  

When their wetland habitats dry out during a drought, the leaves of coast pepperbush wilt and undergo early senescence.  

 

Here is a copy of their article from Science.

Christine Rollinson wrote a Perspective about this topic for Science.

Ula Chrobak reported on the story for Popular Science.

Flood of concerns about Newton's Cheesecake Brook

By Richard B. Primack
 

“A storm is a new, and in some respects more active, life in nature.”

- Henry David Thoreau in his Journal.

 
After a heavy June thunderstorm, Cheesecake Brook on the northern edge of Newton flooded and nearly poured over its banks into the surrounding streets and neighborhoods. With a changing climate, such intense storm events will only get more frequent and flooding danger will get worse. 

Cheesecake Brook flooded during the June 28, 2020 thunderstorm.  
Photos courtesy of CRWA.

 
 
More than a century ago the brook was confined within a narrow stone-lined channel. This straight channel carries sand and other suspended debris directly into the Charles River, along with dissolved phosphorus and nitrogen from lawns and roads, harming water quality.
 

People sampling for aquatic invertebrates in Cheesecake Brook.

 
To address these problems, the Charles River Watershed Association (CRWA) is developing a plan for restoring the sloping banks and natural winding pattern of the brook to increase water retention capacity, reduce flooding, and allow nutrient absorption. The plan includes bioretention basins to trap sand and other debris from streets and outfalls. Large rocks placed in the brook will reduce water velocity and erosion and provide habitat for migratory fish and insect larvae.
 
This is just the first step in a long process of planning, design and fundraising before the project begins and the brook is restored.
 
This is a shorter version of an article that appeared in the Newton Tab.