Marcesence - Photo essay

What: One of my students, Kaleigh Wood, posted about marcescence a couple of years ago. Marcescence, which is common in trees in the oak family, fagaceae (e.g. oaks and beeches), is the process in which the leaves die in the fall before the abscission layer completes the process of releasing the leaf from the tree. I think that these trees just have poor timing and cold weather kills the leave. Others suggest that the dead leaves help protect from the cold, water loss due to wind, or deer browse.

The cost of keeping leaves on is that harsh winter winds could rip the leaves off the tree, exposing the branch to insect predators and pathogens. I suppose another overlooked benefit could be that oak leaves are highly acidic and have high concentrations of tannins. There might be incentive not to drop leaves, where the acids and tannins would leach directly into the soil, making growing conditions for the tree more difficult. By retaining the leaves, the acids and tannins may break down before reaching the soil.

 Whatever the reason may be, the leaf petioles on this red oak (growing along the edge of an open field) had been shredded. Some leaves still barely clung to the branches, but mostly all that remained were the frayed fibers of the petioles.

Turkey Vultures

What: It's FOY (first-of-year) season, and the skies are abuzz with the wing beats of our first returning migrant birds. Apparently, they didn't hear about our record-setting cold weather. I love the first flocks of vultures returning north. They come with the male red-winged blackbirds, the waterfowl (if only our ponds would thaw!!), and the courtship behavior of our over-wintering birds like chickadees.

I spotted this committee of vultures (see my post on collective nouns) over the St Joseph Cemetery on Archibald St in Burlington on Saturday afternoon. There were at least 15 birds.

Over the next few weeks we'll see more and more birds returning to the state. It's an exciting time of year - I'd love to hear what other folks are starting to see as the days get longer and (hopefully) warmer.

Plastic snow

Sastrugi - the sharp features of a windswept snow surface bordering fractured plates of ice in middle of photo.

When I was younger, I had one word to refer to all that white stuff in winter: snow. As I got older and had more experiences with it, particularly through snowboarding, I realized that not all snow is created equal. Snow taxonomy has a history much older than winter ecologists, and much of the rich language found in cold climates to describe snow has been adapted by winter ecologists (like the Russian sastrugi - above, or Innuit qali - below).

Snow can be grouped into three categories:

1. Falling snow
2. Snow on the ground
3. Surface-generated ice features (like ice needles being pushed up from the ground on wet trails, hoar frost, icicles seeping out of cracks in bedrock)

Qali describes snow hanging from trees (like in the image above). Because our snow the other night fell in a frenzy of blustery winds, there wasn't a whole lot of qali left on the trees. Sintering is a natural process where snowflake crystals fuse together. Sintering can happen due to pressure (like stepping on the snow pack) or temperature (melt-freeze together). Because the snow crystals actually bond together, qali will act as a liquid moving in slow motion. Snakes, like in the image above, are common features in northern woods after a good snow storm. We observed a spot today where the sintered snow had bent down around the rock, creating a perfect overhang for a weasel to pop in and out of while hunting.

Getting closer...

What: Sam and went out to the lake yesterday to check in on the progress of the lake freezing over. Boy oh boy did it look frozen all the way across! With the continued cold weather the lake just might be crossable this winter! This would be the first time since 2007. Lake Champlain won't be the only large lake to freeze across. Looks like Superior is on the same trajectory (news story here)!!!

In the afternoon there were people playing hockey out on the ice (specks in bottom left of above photo). Later that evening Jon and I ran out to the light house and followed snowmobile trails. So at least as fall as the break wall, the ice is solidly frozen.

A photo essay in ice

What: Not to inundate the ecstatic beauty with overanalysis, I wanted to cap the week with a photo essay of the things that caught my eye.