This past week we took a field trip to a part not too far from campus! We traveled to Battelle Darby Metro Park, and saw a whole lot of plants that before I would have never known what made them special, but now I know the names and facts about the plants and trees around me. We each got our own focus for the day, and my specific focus – or plants to identify – were invasive species to our parks and habitat. The two species that we saw throughout the park that are considered to be invasive in our state, and country, are the Japanese Honeysuckle and a plant called Autumn Olive.
Limestone Loving Plants
The geology of Ohio can be simplified into two neat sections of Eastern Ohio and Western Ohio. We see in Eastern Ohio land is characterized by sandstone. Sandstone is considered a relatively resistant rock that is commonly accompanied by a shale underlay – particularly more towards the western region of easter Ohio. In contrast to this unforgiving terrain of eastern Ohio, western Ohio is typically characterized by limestone and clay. This portion of our state had broad areas of magnesium deposits that accompany the limestone soil composition. Because millions of years of erosion have worn down this portion of Ohio terrain, western Ohio is typically very flat; this is because the limestone is easily eroded in comparison to the sandstone hills of eastern Ohio. The sandstone found in eastern Ohio soaks in water readily but the composition of sandstone makes the erosion and breakdown process a long time in the making. We see in areas where the shale underlay is not capped or covered by sandstone deep valleys where erosion was made possible. These contrasting portions of easily worn shale valleys and steep slowly eroding sandstone hills makes for a ever changing terrain in eastern Ohio.
Before erosion started millions of years ago, Ohio terrain was characterized by a low arch made of limestone covered by shale, and shale in turn covered by sandstone. These layers we all gently tilted in a way that gave rise this “low arch” about 200 million years ago. The oldest rocks in this low arch would be the limestone we see in the western region of our state. Erosion throughout Ohio of millions of years cut the deepest in the areas where the arch stood tallest; this region is now worn to the oldest limestone rock in the flat plains of western Ohio. In contrast the new and very resistant sandstone layers of western Ohio have withstood erosion, causing the sandstone hills mentioned earlier that characterize most of eastern Ohio. The erosion to a flat plain in western Ohio and the steeply eroded sandstone hills of eastern Ohio were all caused by the Taeys River. This famous preglacial stream was present within Ohio for what is estimated to be 200 million years, it’s eroding forces only being brought to and end with the appearance of the Ice Age glaciers only estimated to have advanced less than a million years ago.
As these glaciers made there slow advances into Ohio terrain they easily made their way over the broad and flat limestone planes of western Ohio. Because there was nothing hindering the advance if the glaciers in this region, they extended as far south as Kentucky. However, they were greatly slowed by the resistant and steep sandstone hills found in eastern Ohio. These steep sandstone hills created a boundary line where Canton now is.
The melting of these glaciers caused a deposition of what is known as glacial till. This glacial till is an unsorted combination of sand, silt, clay, and even boulders deposited by the meltwater of glaciers. The areas of Ohio that were once covered by glaciers is now blanked in a layer of till. The till is further characterized by the material the glaciers once covered. Meaning in western Ohio the till is rich in lime and clay due to the abrasion over the limestone as the glaciers moved across western Ohio. In contrast eastern Ohio till contains very little lime and clay except in the areas where glaciers moved from the limestone to sandstone hills.
The composition of Ohio before the glaciers along with the blanket of till left behind after the glaciers are the characterizing factors in what substrates plants in todays age have to live off of. This means in western Ohio plants have a limey and clayey till to make life out of. This soil is typically impermeable and does not drain or aerate well. While the supply of nutrients is almost considered abundant, this soil does not allow water to soak in making deep parts of this soil/till very low in oxygen ( especially during dry months ). In turn the sandstone bedrock of eastern Ohio creates a soil that is extremely low in nutrients, and tends to be somewhat acidic. Ohio has a third common substrate called glacial gravel that is characterized by is elevation. Glacial gravel that is found at low elevation are normally completely saturated making a high-moisture, low-oxygen substrate. Where as glacial gravel at high elevations is normally extremely dry.
- redbud, red-cedar, hackberry, blue ash, fragrant sumac, and hawthorn all limited to limestone soil.
- sugar maple, beech, red oak, white oak, and white ash all western ohio high lime clay-rich plants
- hemlock, mountain laurel, huckelberry-blueberry, pitch pine, chestnut oak all Eastern Ohio
Sweet Buckey does not occur anywhere inside the glacial boundary lines in Ohio. There is not definitively known reason as to why this is, it is thought perhaps this species struggles to repopulate in the high-lime glacial till of this area. Sweet Buckey also does not extend far north along the glacial boundary either, again the exact reason is unknown but is thought to possibly be because of the climate of this specific region. Hemlock is also present in the unglaciated region of Ohio, but it extends far north of the glaciated region. It is thought that this distribution pattern is due to Hemlock’s restriction to cool and moist environments.
There are some plant species present to the south of the glacial boundary. Rhododendron is one of these species, and is considered to be a mixed mesophytic. Rhododendron is an example of a species that lived in the Appalachian highlands that migrated down through the Teays River drainage, and still survives today in the main valleys where this river once ran.