Late Leaves Live Longer?

Katia Landauer, Richard Primack, and Selby Vaughn

“If time is short then you have no time to waste.” Henry David Thoreau in his Journal.

With a warming climate, trees might become active earlier in the spring, and their new leaves might be at risk for being killed by a late frost. Even if a second crop of leaves is produced later, plant ecologists are concerned that the trees will not be able to grow as much or absorb as much carbon dioxide after losing their leaves. 

Normal leaves of a chestnut tree sapling

In a recent study by Zohner et al., potted tree saplings growing in greenhouse conditions underwent experimental cold treatments to simulate the effects of frost damage. The researchers found the surprising result that the second crop of leaves of beech and oak delayed chlorophyll breakdown in autumn; that is, they remained green longer than leaves on undamaged control plants. The extended longevity of second-crop leaves perhaps reduces the carbon budget effects of spring frost damage. 

Chestnut leaves several days after crushing to simulate the effects of a late frost

We decided to replicate this experiment under more natural conditions using oak, maple, sassafras, birch, and chestnut saplings growing in a forest in Newton, MA. To simulate frost damage, we crushed and later cut off the leaves of experimental plants; in contrast, leaves were left untouched on control plants. 

Over the summer and fall we will monitor plants for new leaves and chlorophyll content using a chlorophyll meter. 

Will second-crop leaves produced later in the summer last longer in the autumn? 

Here is the citation:  

Zohner, C.M., Rockinger, A. and Renner, S.S. (2019), Increased autumn productivity permits temperate trees to compensate for spring frost damage. New Phytol, 221: 789-795.

https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.15445