Persistent Oak Leaves

I went down to Cambridge today, the rare Charitable Research Reserve to be exact.  I wanted to see what waterfowl might be hunkering down in the few areas of open water on the Grand; alas the open water I remembered seeing last week has been reduced to a few very small strips and the day's bird sightings were limited.

During my stroll along the Walter Bean Trail I noticed that many, perhaps most, of the Red Oak (Quercus rubra) had maintained much of their foliage into the winter.  This phenomenon, known as  marcescence, occurs to a few species in the beech family including several species of oak and American Beech (Fagus grandifolia), as well as Hop Hornbeam (Ostrya virginiana).

So why does this happen?  Normally, as cooler temperatures set in throughout the fall, an abscission layer will form at the base of each leaf (where the petiole adjoins the branch) which produces a fragile 'break-point'.  In the following weeks, this break point will give way and the curbs in the 'burbs will be lined with Home Depot leaf bags (and I'll be making the rounds picking them up to supplement the leaf litter in my woodland garden - people just give this stuff away!).  In marcescent trees this fragile layer fails to form and the leaves persist into the winter, often only disappearing come spring with new growth.  There is alot of speculation as to why this occurs, often in young trees or on lower brances.  Is it an advantage?  Is it some sort of evolutionary trait?  This short article provides some interesting insight.

To shed the leaf, an abscission layer forms at the base of the leaf stem or petiole. In marcescent trees, this abscission layer fails to form.

Read more : http://www.ehow.com/info_8114983_do-longer-other-leaves-fall.html

abscission layer forms at the base of the leaf stem or petiole. In marcescent trees, this abscission layer fails to form.

Read more : http://www.ehow.com/info_8114983_do-longer-other-leaves-fall.html

abscission layer forms at the base of the leaf stem or petiole. In marcescent trees, this abscission layer fails to form.

Read more : http://www.ehow.com/info_8114983_do-longer-other-leaves-fall.html

Enough about marcescence, check out this walnut poorly/temporarily cached 10m up a tree.

This Downy Woodpecker (Picoides pubescens) was busy working on the dead ash along the trail.

The limestones cliffs adjacent to the Grand are always neat to explore.

 Some of the cracks are home to the regionally rare fern Maidenhair Spleenwort (Asplenium trichomanes).  There are two subspecies, subsp. quadrivalens and subsp. trichomanes.  The earlier prefers calcareous substrates while the latter prefers acidic substrates.

"Marc sucks" "DANTE is the MAN" and "Tree frogs are cool".  One of these Cambridge youth is going somewhere!  Tree Frogs (Hyla versicolor) are pretty cool.  They produce glycerol which allows them to tolerate a freeze-thaw cycle.  What can you do Dante?