Wednesday, November 12, 2014

Leaves up and down

Virtually all the leaves are down now, though here and there I run across one that hasn’t dropped its leaves yet. Most of those show brown, crinkled leaves, but a few, like the maple in today’s photo, are still brilliant with color.

I suppose it’s too soon to identify which trees will have marcescent leaves through the winter and which simply haven’t dropped their leaves yet.  Marcescence is the term for trees that hold their leaves all winter, often until the new spring buds push the last of the old leaves off.  Some trees are notorious for marcescence—the American beech is one and oaks are another, both of which surround my cabin. Often, it’s the younger and smaller trees that are marcescent.   And frequently, it’s the lower branches only that retain leaves.
One theory (marcescence has many theories) is that retaining leaves helps protect the smaller branches from being eaten by deer and so helps a young tree retain its both branches and its health.  The idea here is that the leaves make it difficult for deer to nip the twigs. The dried leaves are less nutritious and even make their twigs less so.   Another theory is that oaks and beech trees have not fully mastered being deciduous yet and that marcescence is some evolutionary in-between stage.   Another theory is that marcescence helps smaller understory trees better retain and recycle their nutrients, keeping those goodies to themselves, which could be especially important to small trees with their smaller root systems.    
One thing about marcesence that is not theoretical is that the leaves provide shelter for birds in winter, helping to protect them from the wind.  That’s a result of marcescence, not a cause of course, though clearly the birds know how to take advantage of it.


Pablo said...

Ginkgos are clearly NOT marcescent. The one in my back yard lost all of its yellow leaves in a single day.

Scott said...

I wonder if the leaves that hang on endanger the trees by holding snow, which could threaten to break the branches.

I wasn't aware of all these theories. Aren't I glad I stopped by today?

Sharkbytes said...

I love the beeches in the winter woods. Thanks for a new word!

Carolyn H said...

I love the word marcescence. It just kind of rolls off the tongue. I am somewhat amazed there's even a word for leaves staying on a tree all winter long. And who knew there'd be theories about the process? Not one, but several of them. Something as simple as that.