ARBORETUM NEWS (NATURALISTSNOTES)

A Record Breaking Year?

MONDAY, JANUARY 9, 2012

On a 40+ degree F January day, we had a great turnout for Sunday’s walk. The theme was “phenology” –the study of natural cycles of plants and animals, as well as weather-related events, in the context of the seasons. The prefix pheno- is familiar from phenomenon or phenotype, for example, and means something like “observable.”
Phenological records from decades and centuries past are now important data sets that are used to understand regional responses to climate change. Freeze and thaw dates for the Madison lakes, for example, show overall changes that correlate to average temperature increases of climate warming. Of course, there’s always been variation from year to year—sometimes huge variation—in the number of days that a lake is frozen. Year to year changes are just related to the reliably unpredictable Madison weather. But the larger set of data gathered since the mid-1800s shows a steady downward trend in the number of days with ice cover.
You may have noticed that this has been a warm late fall and early winter? The median freeze date for Lake Mendota is December 20. And the latest recorded freeze date is January 30 (that was in 1932). As of this writing, Mendota is still not frozen. Perhaps it will be a record-breaking year.
We didn’t see much in the way of feathered and furred animals. We were a large group and the warm day meant lots of visitors on all trails—the animals may have run for cover. We did see a witchhazel (down in Wingra woods, walking between the springs) that still had fresh-looking petals on some of the flowers—that seemed to me to be phenologically notable. We checked in with the willows in Longenecker—just to see what they were up to. These are nonnative bushes, but are some of the very first to open their buds pre-spring. We did, indeed, see some “pussy willows” peeking out—although if cold weather returns, it may just put the “pause” button on these plants’ precocious growth. Our regional native plants tend to rely on photoperiod for spring growth cues, not just temperature. The changing lengths of day/night are much more reliable!
An observant young visitor noted that there were some small rocks along the pathway in Wingra woods that were sunken into the walkway, perfectly outlined—as if they were pressed down into soft ground, with no other disruption to the surrounding area. We speculated that some combination of freeze-thaw cycles plus additional trail material added for maintenance may have produced this. Anyone else notice this? And have any other ideas?
Be it unseasonable warmth or unseasonable cold, the Arboretum is always lovely. Come visit!

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.