Part I: Batelle-Darby Metropark
All of these questions were answered using information from the article “Linking Geology and Botany…a new approach” by Jane L. Forsyth (1971). Pictures were taken at Batelle Darby Metropark in Columbus, OH.
1. Ohio geology can be divided into two parts so long as you don’t go too in-depth with it. The western half of the state has a base of mostly limestone, which is almost naturally nonexistent in the our humid climate. Since limestone wears down much easier than sandstone due to erosion, the western half of the state is almost completely flattened. In contrast, the eastern part of the state is predominantly the aforementioned sandstone, which weathers much slower, and shale, which like limestone will weather fairly quickly so long as it is not protected by sandstone. Due to this, half of Ohio is almost exclusively flat and plains-like, where the other half is very hilly and rolling due to the different stones that make up the earth.
2. The original sequence of the sedimentary rock strata 200 million years ago was different than today, with soft limestone at the bottom, a layer of shale on top, with it all capped by heavy sandstone to protect it on top. The crest of the arch, on the western half of the state, exposed the oldest rocks (the bottom layer of the strata, the easily-weathered limestone), and further away to the east, the arch tilted so far that at the foot was the much heavier, harder sandstone that was more resistant to weathering. Almost all of the erosion of the limestone in the west, and of the shale and sandstone in the east, was as a result of the Teays River system. The river existed in Ohio for almost 200 million years, and the only thing that could even begin to arrest the power of the river was the arrival of the glaciers, less than a million years ago during the Pleistocene Epoch.
3. Glaciers are awe-inspiring and breathtakingly powerful, but even they must bow to the will of features that are more powerful than they. Sandstone was resistant to weathering of all forms and glaciers are no exception. The steep-sided sandstone hills in the eastern half of the state stood up to the glaciers and, by all accounts, they won. The glaciers were slowed and steered aside by the sandstone, while the limestone put up little fight, so the glacial boundary cuts almost a straight diagonal line down the eastern side of the state below Canton, extending as far south as northern Kentucky.
4. Till is defined as an unsorted mixture of sand, silt, clay, and boulders. It is accumulated directly by the melting glacial ice, as well as the gravel and sand materials deposited by the meltwater. The makeup of the till reflects the nature of the geology and materials present that were exposed to the movement of the glaciers, in turn then moved by the glaciers. Because of this, in western Ohio the till is rich in lime and clay, due to the heavy limestone composition during the glacial period, whereas in eastern Ohio the till contains very little lime and clay except for right near the bases of the sandstone hills, where the glaciers were arrested all those years ago.
5. The differences in the makeup of these tills also changes the substrate that the plants have to grow in. In western Ohio, the soil on the plains is limey and clayey, relatively impermeable, high in lime but poorly drained and badly aerated. The clay and lime are not conducive to immediate absorption of water, instead holding it in puddles at the surface, which creates even lower oxygen availability for plant roots during the wet periods. This also results in bad droughts during the dry periods, since the ground didn’t absorb much of the water when it was wet and has little reserves to utilize. Comparatively, the supply of nutrients for these plants is fairly abundant – if they’re able to get enough water and oxygen, the plants will thrive.
In eastern Ohio, the soil is very acidic, low in nutrients, and extremely dry on the tops of hills, despite the sandstone-bedrock being exceptionally permeable to water. Despite it being very acidic, it provides a supply of moisture to plants that is available year round and also exceptionally cool, as it comes up from springs. Where shale mixes with the sandstone, the cold acidic water cannot extend further downwards, instead building up until it emerges from the ground as a spring. Where the sandstone is mixed with some of the glacial till, the clay and lime in the soil results in it being less acidic while retaining its water-permeable and nutrient-rich properties of the sandstone soil.
6. Plants that are generally limited to limestone or limey substrates are:
- chinquapin oak, Quercus muehlenbergii (try saying that five times fast, or just saying it once, slowly. Bet you can’t.)
- hackberry, Celtis occidentalis
- blue ash, Fraxinus quadrangulata
- hop hornbeam, Ostrya virginiana
- redbud, Cersis canadensis
7. Five tree species that are present mostly on the western limey, clayey substrates of Ohio are:
- beech, Fagus grandifolia
- shagbark hickory, Carya ovata
- white oak, Quercus alba
- pin oak, Quercus palustris
- sugar maple, Acer saccharum
8. Some trees and shrubs that are generally limited to eastern Ohio’s sandstone hills are:
- chestnut oak, Quercus montana
- sourwood, Oxydendrum arboreum
- mountain laurel, Kalmia latifolia
- huckleberry-blueberry, Vaccinium ssp.
- mountain maple, Acer spicatum
9. The sweet buckeye is centralized mostly in the southeast corner of Ohio, behind the glacial till line where the soil would be predominantly sandstone and shale, as opposed to clay and lime – it’s completely contained within the unglaciated areas of Ohio. Using the information from above, this distribution makes sense as the sweet buckeye tends to favor slightly acidic environments with higher moisture.
Unlike the sweet buckeye, the hemlock is found both in glaciated and unglaciated areas of Ohio, although it still is mainly localized in the central- and far-eastern portions of the state. The hemlock’s range is mostly dependent on moisture, which is a big factor in why it does not spread further west, but it is clearly unbothered by the presence or absence of sandstone, shale, limestone, or clay.
The rhododendron exists most heavily along the valleys and ancient path of the Teays River, suggesting that it belonged to the mixed mesophytic association in Ohio – that is, they are not more adapted to wet or dry environments than the are to the other. They appear both in the glaciated and unglaciated regions of Ohio, in all sorts of terrains and ecosystems, which suggests that they were moved by the ancient river and simply took root wherever they landed, with no real need to be picky.
Part II: Cedar Bog (that isn’t a bog)
1. Cedar Bog is a 450-acre nature preserve in Urbana, Ohio. It was the first nature preserve in Ohio purchased with state money, and it is a National Natural Landmark – one of only twenty-five places with that title in the state. It ranks highest of any site in the state on the Ohio Floristic Diversity Index due to the massive diversity of flora that grows in its unique swamp forest. In fact, Cedar Bog is home to 40% of Ohio’s most rare species, both flora and fauna alike. Despite the name, Cedar Bog is not actually a bog at all, it is classified as a fen. Groundwater from the Mad River Valley percolates through the gravel left behind by glaciers and in the ancestral Teays River. The glacier facilitated the movement of most of the rare plants into this unique swamp forest (most of which is under a couple inches of water, hence why you should not leave the boardwalk).
2. The assignment I was given was to find two plants with defense mechanisms, which I initially thought would be harder than it ended up being.
The first plant I noticed with defense mechanisms was the multiflora rose, Rosa multiflora. It’s an exotic invasive species introduced to the United States in the late 1800s. One interesting thing I discovered while looking into this plant was that in the 1960s, people were actually encouraged to spread it as far as possible as food for wildlife, as well as on the sides of highways – since this plant has a tendency to quickly form dense thickets, it was thought it could reduce headlight glare from oncoming traffic as well as arrest out-of-control cars as some form of natural “crash barrier” (source), with little regard to the impact on the natural environment.
The hawthorn, family Rosacea (this exact specimen I was not able to identify to species), has long spines that protrude from the bark. The fruit of the hawthorn are important for birds, squirrels, and rabbits, as well as some deer. The sharp-edged leaves and prickly twigs are not high on the list of food the average deer would go for, but when other food is scarce they’ve been known to pick at them. Small hawthorns can be grown and cultivated as bonsai, highly favored for their beautiful white flowers and red fruits. However, the fruits, if too many are ingested, can cause all sorts of problems all the way to cardiac arrhythmia, and pricks from the spines can cause anaphylactic reactions (source).