ARBORETUM NEWS (NATURALISTSNOTES)

Winter Water

SUNDAY, FEBRUARY 12, 2012

“Can’t complain.” This seems to be the most common retort regarding this winter’s weather in Madison. What does this mean? We are city dwellers. Icy streets and sidewalks make our lives difficult and dangerous. So. sneaking through winter without much freezing and thawing and below zero wind chills is good. Snow? That’s a little more nuanced. Some would like none of that. Other have a sense of need or longing for the white stuff for a picture postcard winter. Some, like myself, look to the heavens to send us to the basement for our cross-country skis – placing a six-inch base of snow at the top of our winter wish list.

I’m not intending to denigrate the wants and needs that I and my fellow city dwellers have, but as a group, people living and working in our rural communities may have a greater kinship and sense of what winter weather means to plants and non-human animals. If the trees in our woods, city streets, and Longenecker Gardens could talk – they may not be complaining, but I imagine they would be engaged in some seriously anxious talk this winter.

Even though they are not as actively taking up water and growing in winter as they are in other times of the year – melting snow in fall, winter, and spring is essential. Last month the precipitation was between one and one and half inches in southern Wisconsin. That’s below normal for the month, which wouldn’t be cause in itself for any alarm. However, we have been running below normal since July of 2011. This has resulted in the cumulative totals sliding progressively further below normal totals, and could eventually result in challenging the growth or survival of various plants.

So, if someone starts complaining about shoveling a little snow – appeal to their eco-logic and tell them that the trees and plants needed some more water. Like the trees, getting enough water in colder months can be a challenge for other creatures too. Walking along the edge of Gallistel Woods, someone pointed to a wide scattering of what looked like chestnut husks in the distance. Had the squirrels been having another party? When all 36 of us trudged over, we started to see lines of long three pointed footprints in the snow leading away like train tracks from this trampled down area underneath the tree. Turkeys! And, quite a feeding party – the area was stomped down so thoroughly, you could barely see the tracks anymore when we got under the tree. They weren’t eating chestnuts though. We soon saw the darkening, rough skinned fruit about the size of a small softball. I carefully picked up the most solid of the gooey remnants and held it up – Osage orange!

Osage orange (Maclura pomifera) trees don’t grow very tall – they average about 40 feet. What is striking about them is their fruit. The fruit grows in size throughout the summer, until it reaches 4-6” across. The distinctive bright yellow-green color sets in as the fruit matures. They remind me of the hues of yellow and yellow-green colors that joggers, bikers, road workers, tennis balls, and golf balls are donning these days to grab our attention so we don’t loose them or run them over. Whose attention is the Osage orange fruit after? In addition to the color, the fruits are designed to be readily noticed by their distinctive largeness and citrus-like smell. They boldly call out: Here we are! But, who is going to reach up twenty feet, pluck them off and eat them? And, it seems they were designed to be eaten whole or in a few bites (explained in next paragraph).

The two animals that will typically eat these fruits are the squirrels and turkeys. But, they need to wait until the fruits are a bit overripe and fall to the ground. Scavenging the fallen fruit, the squirrels and turkeys mostly get water and sugars from the decaying fruit. Even though they may not have read the literature, they are also getting a good dose of antioxidants. Although, the flesh and seeds of osage orange are not palatable to humans and most animals, it is being studied for its medicinal uses. While not palatable to us, the capable digestive tracts of turkeys and squirrels churn away and destroy the seeds of the Osage orange, releasing nutrient oils, proteins and further carbohydrates. Still in afternoon foraging mode, the turkeys had their fill of osage orange and went off to scrape away at the leaves in Gallistel looking for more seeds or other morsels just under the soil and leaf litter. In a sense, they had a good osage snack and walked away without paying their bill.

Typically, plants, pollinators, and foragers co-evolve and provide mutual benefits. The way the turkeys and squirrels eat the fleshy parts and churn up the seeds in their digestive tracts destroys the seeds – so they don’t contribute to spreading of seeds – that’s the payback for the tree. And, the tree is working hard providing each fruit with up to 200 seeds. Osage orange trees will send up suckers from the roots. This helps spread the tree within a limited range. If the original tree or one of the suckers dies, other trees will continue to grow from these suckers – and can gradually spread this way. However, researchers were perplexed at this energy consuming behavior of developing these large, scented, fleshy fruits. Without the right type of forager, the fruits simply fall to the ground and won’t typically extend the tree’s range any further than the suckers already do.

Another conundrum – fossil pollen records show that at one time, before, during, and for a thousand years or so after the last ice age ended (about 15.000 years ago), osage orange trees were present in what we know as the eastern United States from the Gulf coast all the way up through Minnesota. After that the range gradually became restricted to a river valley located in what is now eastern Texas. And, it remained in that limited range until farmers planted seeds and saplings to use the thorny tree as a natural fencerow for animals. Who planted the tree before humans?

We are looking for a big footprint – made by a creature that would see things up in a medium sized tree and could finish off a six-inch treat in a bite or two. If you see this creature in the Arboretum … uh, oh! There is some evidence and paleo-botanical data that point to creatures you won’t be seeing – extinct mega fauna such as mastodon, mammoth and ground sloth. They roamed the area tens of thousands of years ago. They were all capable of eating the fruit whole or in a few bites – thus would deposit viable seeds wherever they went. As a further enticement to this theory, remnants of an Osage orange seed, along with many other plants, were found in fossilized dung of a mastodon discovered in north Florida. Also, the timing of the disappearance of mega fauna and the near extinction and great contraction in the range of the Osage orange supports this theory.

Who would of thought checking out a bunch of decaying fruit would lead us to all that? The most curious creatures drawn to this fruit – turkeys, squirrels and us. In some ways, I feel we have just as much of a challenge understanding our own species. As we crossed the road and headed into Wingra Woods, we were drawn to thinking about humans’ use of these woods. On top of the drumlin in Wingra Woods, is a ceremonial site that was built and used in a more recent period – about one thousand years ago. It is hypothesized that the group of twelve earthen effigy mounds here served as a place to honor and balance the spirits and forces of nature and life and death. We walked down to an elemental source of life at the bottom of the drumlin – two of the springs that feed Lake Wingra.

Before farming and European settlement of the area, Lake Wingra was fed by more than 30 springs. Currently, there are eight springs that directly feed the lake. The major reason for the drying up of some springs is that less water is seeping into the ground. Depleting ground water and lowering the water table also decreases the rate of flow for springs that are still active. I showed our group a drawing of the area around Lake Wingra from the early 1900’s and a photo of a rowboat in the marsh from that same time period. What you can see is that Lake Wingra was surrounded by an extensive system of wetlands – estimated at 1,500 acres. The current wetland area is 210 acres. This means that the water holding and filtering capacities that these wetlands provided have been reduced by about 86% in the last 150 years.

In addition to this loss of water there is a dramatic increase of undesirable water sources. There is an extensive system of storm water lines leading into Lake Wingra from all the way south of the Beltline, north towards Regent St., east towards Monona Bay, and west past Whitney Way. This water and surface flows have resulted in a five fold estimated sediment load increase over very moderate amounts in pre-European settlement times. The estimated increase in phosphorous is over 100 times what it was in pre-settlement times.

With this information, it is a marvel that the lake still can be enjoyable for us and supportive of the plants and animals that currently live in and around the lake. It has been, and continues to be, to the lake’s advantage that most of the south shore of the lake is Arboretum property. City property areas of Wingra Park and beach are on the north end, and Edgewood College property is on the west end. Many lakes like Wingra that are relatively small and shallow have ceased to be a usable resource within our cities. Lake Wingra’s surface area is 325 acres, and its average depth is about 9 feet and its maximum depth is 14 feet. As you walk around the shore by Edgewood College and in the Arboretum you will see signs up for retention pond restorations to filter and retain runoff. There are various walkways and plantings to improve the aesthetics and the functioning of existing and created wetlands.

Throughout the year, our wetlands are a great resource for all of us. We did see a flock of robins that will stay here all winter, probably in large part due to the availability of water from the springs and the other plant and animal life that depend on wetlands. The area around the springs are also a good place to find flocks of cedar waxwings and the more common winter characters – chickadees, nuthatches, and woodpeckers by the springs. This year, one of our stewards and avid birdwatchers, has been seeing a great blue heron that may have found that our remaining springs can provide enough resources to spend the winter. If you are checking out this area, you will also be sure to notice our earliest winter/spring wildflower has emerged – the skunk cabbage.

Paul Borowsky
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.