ARBORETUM NEWS (NATURALISTSNOTES)

Halfway to Spring!

SUNDAY, FEBRUARY 5, 2012

This year’s Halfway to Spring walk was Feb 5. Last year it fell on Feb 13. This year, similar to last year, it was low- to mid-40s and sunny. Last year, however, there was deep snow while this year there is plenty of bare ground. There was also plenty of ice and mud on Sunday – a bit treacherous in some places.
We set off to look for the things we tend to observe around the halfway to spring mark: singing cardinals and black-capped chickadees (affirmative!), snow fleas (no, but see below), skunk cabbage points (affirmative!), and “pussy willows” (affirmative!).
We checked in on the shed antlers by the row of Cornus in Longenecker. Status: still there and totally un-gnawed. Mice are known to chew through these quite rapidly and effectively, so the fact that they are still untouched is curious. We then checked on the row of willows. Just short of a month ago, there were only a few little pussy willows (immature catkins) poking out. But the willows have been busy in the last month – some of them more than others. A couple species were in full show, covered in silky catkins. Note, however, that the willows in Longenecker are horticultural varieties that can survive our winter, but not species that evolved in Wisconsin.
The skunk cabbage are up! Some of the maroon flowers are visible, but not yet in their full maturity. These plants have fascinating metabolic tricks that enable the plants to maintain a temperature significantly higher – even 30 degrees F – that the air temperature (I’ve seen varying numbers but you get the general idea). In other words, these plants are thermogenic. Typically, a plant (or animal or other organism) breaks down sugars (and other compounds) converting the chemical energy stored in the sugars into another type of chemical energy that cells can use for cellular activities. And, of course, some energy is released as heat. Skunk cabbage’s thermogenic abilities are because it uses an alternate metabolic pathway and breaks down stored sugars without producing any usable energy compounds. Instead, all of the energy is released as heat. Cool trick.
I had found some “snow fleas,” a type of springtail, the day before but we didn’t find any during our walk – despite many eyes a-looking. We did, however, find a lovely winged insect plodding along the snow. The day before I found another, different type of active winged insect, also unidentified. There are many kinds of insects that are active on these warm(ish) winter days. Some are already out and mating – at least on days when the air temperature reaches about 45 degrees F, if only in one little spot of sunshine. Others just take advantage of warm weather to get out of their protective shelter-spots and hopefully find something to eat. Insects also have fascinating metabolic strategies for coping with freezing weather. Some make cellular changes that allow them to avoid freezing. Others make cellular changes to help them tolerate freezing. (The ability to freeze living tissue and then have it defrost back to a functional state is of particular interest to some in the medical field, as you can imagine, and a hot research topic.)

We heard, but did not see, cardinals. We heard and some folks spotted black-capped chickadees.
I admit that the halfway to spring landmark seems not quite so exciting to me this year, since I’ve barely noticed that it’s winter. That said, I’ve also been greatly enjoying the many warm sunny Arboretum walks this season.

Sara Cohen Christopherson, Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.