Battelle Darby Metro Park

THE CONNECTION OF GEOLOGY AND BOTANY

Sometimes, at least for me, it’s easy to forget about the complex and long-standing history of the Earth and the landscapes found all around us. However, the rock formations, composition, and locations play a major role in influencing what species of plants grow in particular areas. In Ohio, the state can be divided into two parts. One is the glaciated area found in western Ohio. As explained in Jane Forsyth’s article, “Linking Geology and Botany,” she discusses how these are areas underlain with limestone and dolomite that are easily eroded. As a result, the landscape has become very level and flat. On the other hand, eastern Ohio is part of the unglaciated area that has erodible shale that is then capped with sandstone, which is resistant to erosion. This ends up creating deep valleys with steep sandstone hills.

The original sequence for these different kinds of rocks first includes thick layers of limestone, then shale, and then all overlain with sandstone. The crest of these rock strata created an arch better known as the Appalachian mountains, which is super cool! The oldest rocks along the crest consist of predominantly limestone, while the younger rocks are sandstone and contribute to the sandstone hills. The main erosion system for this area was the Teays River. It was present in Ohio for about 200 million years and played a large role in creating the valley and hill landscape that is found in the east. The contribution of this river system came to halt when glaciers from the Ice Age started advancing into the area.

The glaciers were slowed due to the valleys that are part of Ohio’s landscape. Glacial deposition occurred in these valleys and worked to slow down the progress of these huge glaciers, which is honestly pretty impressive.

A sketch of Ohio shows the difference between the glaciated and unglaciated regions of the state.

In Jane Forsyth’s article, the term till is used to describe an “unsorted mixture of sand, silt, clay, and boulders.” Due to different landscapes, the composition of till varies across the state of Ohio. Western Ohio has glacial till that is rich in lime and clay. In eastern Ohio, the glacial till is less limey and clayey. This difference in composition has an impact on what type of plants are able to grow in these areas.

For example, western Ohio has limey and clayey till. This contributes to a soil that is permeable, usually poorly drained, and not adequately aerated. However, there is typically a high supply of available plant nutrients. On the other hand, eastern Ohio is dominated by permeable sandstone bedrock. This results in an acidic and low nutrient substrate that is particularly dry at the top hills.

The connection between geology and botany was a major focus for the field trip we took to Battelle Darby Metro Park and Cedar Bog. While we were there, we saw several examples of trees and shrubs that typically grow in limestone. One of the first ones we saw was hackberry (Celtis occidentalis). This tree is easily recognizable because it has lots of bumps on its bark, making it look like it’s been hacked at. Another tree that loves areas rich in lime is blue ash (Fraxinus quadrangulata). Blue ash is usually easy to identify because it has square branches. On our trip, we also got to see redbud (Cercis canadensis) that is known to grow in the western parts of Ohio. It can be identified due to its heart-shaped simple leaves. Chinkapin oak (Quercus muehlenbergii) is another species of tree that is found growing in areas with high lime content and was observed at Battelle Darby Metro Park. This tree species has alternating simple leaves that are coarsely toothed. Lastly, we observed prickly ash (Zanthoxylum americanum) which is known to grow in areas with concentrations of limestone and likes well-drained soils.

This hackberry tree has very distinctive bark and has alternate, simple leaves.
When looking up through the canopy, these opposite pinnately compound leaves are indicative of a blue ash.

The heart-shaped leaves of redbud are an important distinguishing characteristic!

These chinkapin oak leaves are coarsely toothed and stretch up into the canopy!

The compound leaves of this prickly ash resemble those of other ash trees, but it’s actually in a different family!

Based on the different levels of acidity and nutrient availability, there are some particular plants that only grow in areas of high-lime, clay-rich substrates. One example of this would be hop hornbeam (Ostrya virginiana). Another example would be red-cedar (Juniperus virginiana). Hawthorn (Crataegus mollis) and blue ash (Fraxinus quadrangulata), like seen on our field trip, are also excellent examples of trees that love high lime content. Lastly, fragrant sumac (Rhus aromatica) is another plant example that is found in areas of western Ohio.

On the other end, there are also plants that are well adapted to live in the acidic and low nutrient areas of eastern Ohio. One great example is chestnut oak (Quercus montana). Some other examples include sourwood (Oxydendrum arboreum) and scrub pine (Pinus virginiana). Shrubs that grow in these areas of low limestone content include mountain laurel (Kalmia latifolia) and greenbrier (Smilax glauca). Paying attention to the species of plants that are growing around you can provide a lot of insightful information about natural history and the geology and composition of the area.

There are some species that have a very specific distribution in the state of Ohio. Sweet buckeye is one of these species and it actually isn’t found inside the glacial boundary and doesn’t extend north to the boundary. Reasons for this particular restriction are unclear, but may have to do with weather and climate change patterns. In comparison, hemlock is also only present in the unglaciated part of eastern Ohio, but it extends farther north to meet the glacial boundary, unlike sweet buckeye. This is due to the specie’s restriction to cool, moist environments found in deep valleys. Lastly, rhododendron lives in the Appalachian highlands and migrated down through the Teays River system. It now lives south of the glacial boundary.

 

CEDAR BOG FIELD TRIP

One of the things I really enjoyed learning about on our field trip was the differences between bogs and fens and why Cedar Bog isn’t necessarily accurately named. A true bog is clogged which means water enters as rain and only escapes through evaporation. A layer of peat builds up on the bottom as plants die and decay, which makes the water acidic. Cedar Bog is actually a fen because it has small streams that work to drain the area. The limestone that is present in Cedar Bog makes the water alkaline and neutral, allowing for the growing of sedges. When glaciers moved through the western part of Ohio, end moraines were created around Cedar Bog, forming a valley. Water forced to the surface of this valley helps provide cold groundwater to support a number of different species. A combination of these unique characteristics and geology help to create a diverse landscape where a wide variety of plants can grow.

My assignment over the course of this field trip was to find two examples of flowers with radial symmetry! The first one that I found to fit this description was the wavy-leaved aster (Symphyotrichum undulatum). This flower showed all the characteristics of the Asteraceae family and the deviation away from the primitive characteristics of FENSH. Its purple flowers and arrow shaped leaves are great indications to help identify it. A fun piece of information I learned about this species is that since it’s a late blooming flower, it provides a crucial source of nectar to various species of bees and butterflies. Along with this, it is also a host for pearl crescent caterpillars!Look at the pretty purple color of these petals and unique leaves!

The other flower example I found was the common yellow woodsorrel (Oxalis stricta). This plant also exhibited radial symmetry and has some cool features, making it easy to identify. The flowers are yellow with five petals and then are followed by ridged seed pods that grow at 90 degree angles from the stem. Another distinguishable characteristic is the leaves are palmately compound and are divided into three heart-shaped leaflets that resemble a clover. One of the neat things I learned about this species is that every part of the flower is edible and can be added into salads, soups, and teas. This plant has high levels of vitamin C and oxalic acid, which is why one of its common names is sourgrass.

Take a look at these cool heart-shaped leaves!

One of the unique plants we saw on our trip when focusing on coefficients of conservatism was swamp birch (Betula pumila). This specific tree has alternate leaves that are doubly toothed. These trees are also hosts for moth caterpillars and Dreamy duskywing butterflies. Based on the Floral Quality Assessment Index (FQAI), the swamp birch has a value of 10. This is pretty remarkable and means that this species has a very narrow range for ecological tolerances.

The double toothed leaf margins can easily be seen in this photo!

Another really neat plant found at Cedar Bog is the Ohio goldenrod (Solidago ohioensis). This plant in particular is part of the Asteraceae family, helps to support several different species of moths, and has a CC value of 9. It is only found in a few specific areas of Ohio!

 

Here’s some Ohio goldenrod growing alongside some sedges found in Cedar Bog.

One of the other plants that was observed throughout our field trip to Cedar Bog was white snakeroot (Ageratina altissima). This plant is also part of the Asteraceae family and has fuzzy white flower heads that bloom in late summer or early fall. A little tidbit of information I learned is this plant is believed to have killed Abraham Lincoln’s mother. She died of milk sickness, which is a poisoning that results from drinking the milk of cows who have eaten white snakeroot. This plant has a CC value of 4!

This plant consists of small fuzzy white flowers!

Lastly, we came across several examples of poison sumac (Toxicodendron vernix) throughout our field trip. This plant contains the same toxin that is found in poison ivy and poison oak, but is more concentrated and can cause worse rashes if touched. Poison sumac is almost exclusively found in swamps and bogs, however its seeds can be spread by various wildlife. This plant has a CC value of 7.

 

Similar to poison ivy, it’s best to leave this plant alone!