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You must provide for their own transportation to the University of Wisconsin - Madison's Arboretum. The fieldtrip is designed to supplement Dr. Hotkiss' lectures on ecology with concrete examples. it is also intended to illustrate topics taught earlier this semester. The idea is to bridge the gap between course work and the natural world where our botanical subjects exist. Moss sporophytes, fungi, the early growth of woody stems, strobili of Equisetum, algae and more are all proper subjects for discussion. We will also be opportunistic, and choose things to discuss based on what is encountered. One goal is to discover new and interesting aspects about common, previously unappreciated aspects of our environment that relate to our curriculum. This preview should provide some particulars about the environment along the route that we will follow.
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Introduction:
Everyone meets at Wingra Woods parking lot. At the U.W.-Madison arboretum, most plantings are made to reflect naturally occurring plant communities. Some of these planted communities have been quite successesful (such as the prairie), while others have been disappointing (Leopold Pines). The success or failure of these communities is directly related to climate. Many of the trees in the Ohio Valley lowland forest, for example, were not hardy here because it is too cold in the winter. In the case of the Leopold Pines the attempt at creating a community similar to the pine forests in northern Wisconsin has run into difficulty partly because it is warmer here in the summer and the trees become water stressed. Another important factor, especially here in Wisconsin, is fire.
In Dane county, the temperature and rainfall are such that on an undisturbed site a forest will form, dominated by trees able to reproduce in their own shade. These would include a sugar maple, basswood, and a few other trees such as green ash and hackberry. When European settlement took place in Wisconsin, what was actually found was a patchwork of prairie and savanna, because of the frequent ocurrence of fires. After settlement the landscape was transformed. Some of the areas we will visit have been through more than one transition. From open prairie/savanna, many sites were converted to farmland and open pasture. Those areas that were not subject to agriculture were transformed, by the exclusion of fire, to oak woods. Many of the oak woods seen all through southern Wisconsin are not primeval but date back to settlement days with the suppression of fire.
One of these resulting oak woods is Wingra woods. This site is being managed to convert it from an oak woods into a northern mesic woods community dominated by the shade-tolerant trees, yellow birch (Betula alleghaniensis), sugar maple (Acer saccharum), and hemlock (Tsuga canadensis). This is being accomplished simply by underplanting the oak woods with maple, basswood and hemlock seedlings. Because the oaks do not compete well in their own shade, they are relplaced by the previously-established shade tolerant species. The northern mesic forest is a climax community found on many sites in cenral and northern Wisconsin.
Around the parking lot itself can be found shagbark hickory (Carya ovata), black cherry (Prunus serotina), and crab apple (Pyrus sp.). Note that the black cherry is heavily infected with the disease, black knot, caused by an ascomycete. This parasite will spread from woodlots to infect orchards of European plum, but other cultivated stone fruits seem to be immune.
As you leave the parking lot and descend the hill observe the open-grown oaks dominating the canopy. One can tell these oaks were open grown because the crotch angles of their lower branches are wide. This would not be the case if they had originally been crowded. As you progress through Wingra woods, notice the transition that is occurring: the largest trees are shade-intolerant oaks (white, black, and northern red), and the understory trees and seedlings are mostly the shade-tolerant tree, sugar maple, typical of a northern mesic climax community.
Route Through Wingra Woods :
We will proceed from the parking lot at trail marker N1 down slope to N4 by an Indian mound, and progress down hill to The Booth Courtenay Memorial Overlook by a spring. From the spring, we will follow the trail to the right (east) past K4 to a marshy area with a wooden walk. From the walk, you can see growth of the parasitic angiosperm, dodder (Cuscuta sp.), skunk cabbages, shrubby willows (Salix sp.), wild irises (Iris sp.) and Impatiens. From here, backtrack to K4 where you will see numerous hemlocks (Tsuga canadensis). This remarkable conifer is truly shade-tolerant. Hemlocks can grow suppressed as small trees for over a hundred years. When a large canopy tree falls and creates an opening, one of these old shade-suppressed hemlocks can then quickly grow to occupy that space. Here we only see small specimens, but one day, if undisturbed, they will be among the giant trees in Wingra Woods. From K4 we go up slope past K2 to the road. On this stretch you will again pass by an Indian mound. Also, along this stretch, you will see beech trees (Fagus grandifolia). Beech is distinctive both in the winter condition, with its long buds, as well as in the summer condition with its leaves.
In Wingra woods note that many trees are characterized by their bark. Species easily identified by bark include shagbark hickory with its shaggy bark, black cherry with its scaly bark, cottonwood (Populus deltoides) with its distinctive white bark on younger limbs, and its deeply furrowed bark on the older limbs and trunk, paper birch (Betula paperifera) again with a distinctive white bark and also the distinctive peeling bark of yellow birch. Other characters, perhaps unique to a given species, may be of help. For example, basswood trees will often have suckers coming up from their base. This is true even for large specimens.
Gallistel Woods was planted as a southern mesic forest. Like Wingra Woods, it is an old oak forest that has been under-planted with shade tolerant trees. But in this case with species typically found the southern mesic climax community. The most notable difference here is that yellow birch and hemlock are absent. Sugar maple is still the primary tree underplanted, but you will also see basswood (Tilia americana), and red maple (Acer rubrum).
Route Through Gallistel Woods:
The route we take begins at the road. As you enter Gallistel woods through the gate, note the large basswood tree to the left. Go straight to marker G5 and turn right (west) to G6, from there proceed downhill to your left (south) by an Indian mound. Proceed on to marker G1. From here turn right and you will shortly come to a stone building. At this point there is an intersection. At this intersection can be seen a sapling of Ohio buckeye. Following that route you will come to F6 where you then proceed up slope through a cedar glade, populated by eastern red cedar (Juniperus virginiana). At this point you are leaving Gallistel woods.
Cedar Glade and Conifer Swamp:
Juniperus virginiana often forms pure stands where the soils are thin and limy. This is an example where the bedrock determines the type of community that forms on a given site. Lebanon, Tennessee gets its name because of the predominance of this type ofvegetation around it, and of people's confusing this cedar with the genus of the biblical cedar of Lebanon (Cedrus sp.). If you look for them you may find galls of cedar-apple rust. You should also find violets growing in this area. This is also the site where a blind has been set up for culling deer. The problem of deer in the arboretum will become strikingly apparent as you near the edge of this glade and look across to a conifer swamp community. As you stand on the edge of a glade populated by red cedar (Juniperus), and look across to a swamp populated by white cedar (Thuja), you might want to pause to contmplate the difficulties associated with common names. f someone asked you about the growth requirements of cedar but they didn't know the genus name, you might find it difficult to decide whether to tell them whether cedar typically grows in waterlogged, or in thin dry soils !
While looking across this conifer swamp note the deer damage. Stretching across the tree line is a horizontal boundary below which no leaves are seen. This boundary is determined by the reach of the deer in the arboretum. This is one place where this impact is obvious.
Route Through Wet Land , Pine, and Northern Conifer Communities:
Leaving the cedar glade take a right (go south) at F4, and at marker F3 can be seen an enormous example of a broken old cottonwood. At this marker go left (east) on to a cul-de-sac leading to Teal Pond. Backtrack to F3 and proceed south along the trail past F2 to L3. Along this stretch of path you will be traveling through an open wetland community with conifer swamp growing on the left (east).
A tree of interest here is tamarack (Larix laricina). This is a native, deciduous conifer that grows in northern wetlands. In Wisconsin, one interesting place where they grow is in quaking bogs. The tree has an extensive, but shallow root system that keeps it upright even when growing on a floating mass of Sphagnum moss (which is not the case here).
Along this path another plant of interest is the shrub, alder (Alnus). This shrub, like the legumes, form root nodules with nitrogen fixing bacteria. This arrangement is especially nice for a plant growing in wet nitrogen deficient soils.
Pine Forest
At marker L3 proceed to the right where you will find a pine planting consisting of a group of large white pines (Pinus strobus). All of these trees are probably connected together by root grafts, which would explain the survival of those individuals crowded toward the center with very little photosynthetic area. Photosynthate can move via root grafts between trees, and those plants in the middle may be nourished by their neighbors on the outside.
white pine is not shade-tolerant and, hence, relies on disturbances to repopulate itself. It can live for four hundred years, however, so the rate of disturbance in a habitat does not have to be great for it to be perpetuated. Contrast this with jack pine which you will see latter in the horticultural planting.
The age of these pines can be determined beyond a certain point on the stem, by counting the whorls of branches. Each whorl represents one year's growth. White pine once supported an extensive industry in Wisconsin, which has since collapsed due to over exploitation. Very little of this original forest is left.
On to Curtis Prairie
Beyond L3 proceed to the right to marker L2 . At L2 is an artificial catchbasin designed to protect the arboretum from beltline highway runoff. Since rain doesn't soak into pavement, a tremendous amount of runoff is generated that moves down slope towards the prairie communities. This runoff carries salt, asbestos, rubber, and exhaust residue and poses a serious threat to the communities in the arboretum. This is one example of how natural preserves are invariably affected by the unprotected areas around them. Beyond this is marker L1 beyond which lies a northern boreal forest community. Its most notable member is white spruce (Picea rubens). Past this woods you will encounter Curtis Prairie.
Of all the communities attempted at the Arboretum, the prairie restorations are perhaps the most successful (Curtis Prairie seen here), and Green Prairie on the other side of the beltline). This isn't really surprising since these sites were originally occupied by an oak savanna-prairie community. The prairie restorations date back to 1930's when members of the Civilian Conservation Corps transplanted pieces of sod from prairie remnants into the area. While the site was originally occupied by a prairie community, farming and pasturing had eliminated most prairie species. By 1930, the site of Curtis Prairie was a pasture dominated by bluegrass. Transplanting prairie species wasn't enough to establish a prairie. Until the1950s, this site still remained, basically, a bluegrass field. In that decade controlled burning was adopted as a management tool.
Prairie species usually begin growth in the late spring (here, in southern Wisconsin, around May). This late growth may be an adaptation to life in fire swept habitats. Bluegrass (Poa pratensis), on the other hand, commences growth very early in the spring. By burning after bluegrass begins growth and before the prairie species start, fire effectively controls weeds unadapted to prairie life. Today, Curtis Prairie is divided into two parts. In any given year one part will be burned; the following year the other section will be burned. At no time will the entire tract be burned. This staggered burning cycle allows for the survival of populations of invertebrates in the unburned sections.
About Oaks
The trees that occupied the prairie/savanna that preceded settlement here were oaks. Certain oaks are more fire-resistant than other native trees. Also, some oak species can persist indefinitely as root stocks even though their tops are periodically killed by fire. The most fire resistant oak is burr oak (Quercus macrocarpa). Trees of this species can be seen along the path around Curtis Prairie, and its identification is easy even in the winter condition because of the thick corky ridges found on its twigs.
Route Around the Prairie
When you encounter Curtis Prairie go right (north) and follow the pathtowards the MacKay Center. Here are some things to look for as you walk:
Exotic Weedy Shrubs:
In the woods along the path (opposite the prairie), there is an abundance of buckthorn (Rhamnus cathartica) and shrubby honeysuckle (Lonicera tatarica). Both of these are introduced, insidious weeds that seem to be impossible to eliminate.
Vegetative Reproduction from Adventitious Buds Formed by Roots:
Along this trail you will see lots of poplar (Populus sp.). This tree tends to produce sprouts from its roots some distance away from its trunk and gives rise to thickets of trees like the ones all along the trail.The paper industry in Wisconsin has grown dependent on poplar's ability to reproduce from its roots.With this tree, once a woods is clear cut it has been unnecessary to replant (The industry, however, is now jeopardized by a fungus that causes rot in the new sprouts of cut trees. This fungus is the honey mushroom (Armillaria sp.). Its basidiomata can be found growing on wood and are eatable. This is incidentally the same genus of fungus that is thought to be the world's most massive organism. Fairy rings of this fungus miles in diameter have been discovered in Michigan. This same type of vegetative reproduction from roots can be seen along the trail where a big clump of bush plum (Prunus americana) may may be in fruit.
Longnecker Horticultural Gardens:
We pass through this planting area on the way back to the parking lot. In some ways this area is similar to traditional arboretums where plantings are made in a formal manner within taxonomic groupings. However here are planted some interesting, and often bizarre, cultivars, all of which are conveniently labeled. Among my favorites is a Norway maple (Acer platanoides) that grows like a telephone pole (for people with small yards?), and numerous examples of different clones of spruce that grow horizontally along the ground and are reminiscent of the form of trees growing at the tree line of mountains.
One planting which must be seen, is of American chestnut (Castanea dentata). This impressive species was once a dominant tree in forests running from New York south to Georgia. Its population was decimated by chestnut blight caused by the ascomycete Endothia parasitica. This was inadvetently indroduced on Chinese chestnuts planted in New York about 1900. From New York state the disease ran rampant, moving south through the chestnut's range reaching Tennessee and Georgia by the 1930's. So far as the species' ecological importance is concerned, it has been eliminated. However, in areas of its original range, living root systems persist. These continue to produce new trees that seem unaffected by the blight until they reach a size where they are almost sexually mature. Then they invariably become infected and die back to the ground. The specimens we see here are not resistant. They survive only because they are out of the natural range of chestnut, and are not reached by the spores from this on-going cycle of infection. As more chestnuts are planted in the midwest the chances of the disease moving into Wisconsin is increased. In other words, planting chestnuts here may be bad idea.
Before you leave notice the jack pines (Pinus banksiana) near the gate, and check for microsporangiate cones. This pine forms serotinal cones that tend to remain closed until a fire occurs. Jack pine, itself is not fire-resistant, but an acre of trees may have as many as two million seeds that can be released after a fire. Furthermore, the seedlings do very well in habitats that have been recently burned and can reach sexual maturity in five to ten years. Repeated fires of intervals greater than this will tend to perpetuate this species in a given site.
Wingra Woods parking lot is across the road; this is the end of our route.