TNC Land Steward Beth Mizell led a brief but informative two-hour hike through a variety of plant communities, discussing the active management that is taking place at the property while we walked. While I would have loved to spend more time botanizing the entire 92-acre property, I very much enjoyed scratching the surface in the savanna and fen communities of this outstanding preserve. The photograph directly below shows a Black Oak (Quercus velutina), White Oak (Quercus alba), and Shagbark Hickory (Carya ovata) -dominated savanna located on a kame (a gravelly mound deposited by a glacier). This community is characterized by large, open-growth trees and an open understory, and it is dependent upon fire to maintain this structure.
Below is a photograph typical of the fen community. Fens are generally grassy and sedgy communites. This time of the year, grasses and sedges such as Big Bluestem (Andropogon gerardii), Bluejoint Grass (Calamagrostis canadensis), Twig Rush (Cladium mariscoides), and Indian Grass (Sorghastrum nutans) are obvious, as are composites including Bristly Aster (Aster puniceus), Flat-topped Aster (Aster umbellatus), Swamp Thistle (Cirsium muticum), Spotted Joe-Pye Weed (Eupatoriadelphus maculatus), Giant Sunflower (Helianthus giganteus), Dense Blazing Star (Liatris spicata), Riddell's Goldenrod (Oligoneuron riddellii), and Swamp Goldenrod (Solidago patula). Fens are amazing, particularly because it seems that there is something different in bloom every week of the growing season. They are particularly exciting for me in the early summer, when the sedges (Carex spp.) are in fruit.
Without active management including selective shrub removal and burning, this fen would undergo natural succession and become a shrub-dominated (often called shrub-carr) system. We saw evidence of this succession in pockets of shrubs including Poison Sumac (Toxicodendron radicans), Gray Dogwood (Cornus racemosa), Red-osier Dogwood (Cornus stolonifera), Pussy Willow (Salix discolor), and Sageleaf Willow (Salix candida).
One of the most charismatic fen species this time of the year is Lesser Fringed Gentian (Gentianopsis procera), shown directly above and below. There aren't many flowering plants that can match the gorgeous blue of this four-petaled crowd-pleaser. To see my post at Get Your Botany On! on the differences between this species and the very similar Fringed Gentian (Gentianopsis crinita), click here.
Another late-flowering fen species is Grass of Parnassus (Parnassia glauca), shown in the photograph below. Contrary to what the common name suggests, this species is traditionally placed in the Saxifrage family (Saxifragaceae), or sometimes in the Grass of Parnassus family (Parnassiaceae). The egg-shaped leaves and mesmerizing pattern of venation on the petals make this quite an attractive plant. I have to believe that the green veins on the white petals, coupled with the golden false nectaries inside the flower, have evolved for the sole purpose of guiding insects to the center of the flower, where they then collect and disperse pollen.
A less conspicuous but regular component of fens in northern Indiana is Kalm's Lobelia (Lobelia kalmii), which is treated as a member of the Bellflower family (Campanulaceae) and sometimes of the Lobelia familiy (Lobeliaceae). Pictured below, this species has narrow stem leaves and slightly broader, spatulate basal leaves. The two upper petals remind me of the ears of a jackrabbit.
What makes a wetland a fen is the fact that it is a groundwater-driven system; this groundwater has often become calcareous after flowing through adjacent uplands with limestone substrate. Many scientists consider a fen a system with neutral to alkaline water chemistry, as opposed to a bog, which is acidic. However, I have also read scientific papers that define a fen as a groundwater fed wetland, regardless of chemistry, and a bog as a former kettle lake with no groundwater influence. Using the latter definition, a fen can be a rich fen (neutral to alkaline, nutrient rich) or a poor fen (acidic, nutrient poor). I tend to use the second definition, and Swamp Angel seems to be a good example of a fen with both rich and poor components. While much of the area we saw at Swamp Angel was dominated by fen plants that grow in neutral to alkaline conditions, Beth also took us to a portion of the fen where plants that grow in soils with lower pH values were dominant. This area still was groundwater fed, and was not located in a depression. There are, however, also kettle lakes at Swamp Angel, which muddies the waters a bit, so to speak. The photograph below shows one of these acidic areas bordering a kettle lake.
Within this area, we were rewarded with three parasitic plants: Round-leaved Sundew (Drosera rotundifolia), Flatleaf Bladderwort (Utricularia intermedia), and Purple Pitcher Plant (Sarracenia purpurea). That's right, these species actually get most of their nutrients from insects that they capture! They have adapted this method of attaining nutrients because they live in nutrient poor habitats. All three of these species have different mechanisms for capturing prey.
Round-leaved Sundew has small green leaves with tiny sugary mucilaginous glands on short red stalks. The bright color and tasty glands attract insects, which then become stuck to the leaf. The plant then uses enzymes to digest its prey. That just doesn't seem fair.
Flatleaf Bladderwort has tiny bladders attached to its leaves. These bladders have miniscule hairs surrounding a trap door that is triggered when the hairs are touched. Because of negative pressure within the bladder, when the trap door opens, water and prey rush into the bladder, and the opening quickly slams shut, trapping the prey within the bladder in the blink of an eye. The prey is then digested. This is the black hole of the plant world, I guess.
Because Purple Pitcher Plant flowers from May to July, we weren't able to see its bloom during our field trip. Below is a photograph of the intriguing purple-red flower that I took at another site in northern Indiana in May 2006.
In the brief time that we were at the site, I recorded 68 plant species within the fen, and another 30 on the kames. Nutrient rich fens are typically also very rich floristically.