Geobotany Questions (And Answers)

1. The geology of Ohio (if not regarded too closely) may be divided neatly into two parts. Contrast these two parts in terms of their geographic location, types of underlying rocks and their physical properties, and the landscape/topography that characterizes each.

• Ohio can neatly be divided into a western half and an eastern half. On the western half, Ohio is characterized by its limestone, dolomite, and other easily weathered sedimentary rocks leading to smoother and more fertile soils. Its glaciated past leads it to be flatter with rolling plains and fertile farms. The eastern half is typically more rich with shale, siltstone, and sandstone, also sedimentary rocks but much less weathered. This provides rougher soil and therefore more rugged and cliff landscapes.

2. The reason for the difference in kinds of rocks is not difficult to understand. Describe the original sequence of sedimentary rock strata (three types in order from top to bottom), an arch that formed 200 million years ago noting where the crest of the arch was located compared with the low-lying toe of the arch, and an important river system that occupied OH for a long time. (Be sure to give the name of the river, state about how many years it flowed and what effect it had upon the landscape. What curtailed the activities of the river?)

• The sedimentary rock strata from top to bottom is Sandstone, Shale, and Limestone. The arch that formed nearly 200 million years ago was in part a product of the pressures of the rock strata and formed the original Appalachian Mountains. The oldest rock can be found along the arches crest as erosion has cut deepest on the arch’s highest points. The Teays River was responsible for much of the erosion as it flowed for 200 million years and shaped the landscape during this time. The advancement of the Pleistocene glaciers ultimately disrupted the flow of the river by filling it with glacial till.

3. Pleistocene glaciers invaded OH a few hundred thousand years ago or less. What feature of the landscape slowed the glaciers and so caused there to be a glacial boundary cutting across OH? Sketch a map of Ohio and on it place the glacial boundary

• The steep-sided sandstone hills of eastern Ohio slowed the glaciers creating a definitive boundary in Ohio shown in the picture below.

4. Describe “glacial till” in terms of its general composition (a definition of till), and how it differs in eastern and western OH.

• Glacial till is an unsorted mixture of sand, silt, clay and boulders deposited by glaciers. In western Ohio, the glacial till is lime and clay abundant while in eastern Ohio it is composed of mostly sandstone and shale with much more acidic properties.

5. Contrast the basic substrate for plants in western and eastern OH in terms of drainage, aeration, pH (limey versus acid) nutrient availability.

• Western Ohio
• • Drainage: Poor due to clay-rich till
  • Aeration: Lower aeration due to heavy soils
  • pH: Limey and therefore higher pH
  • Nutrient Availability: High due to calcareous soils
• Eastern Ohio
  • Drainage: Better due to sandy soils
  • Aeration: Higher aeration due to looser soils
  • pH: Acidic
  • Nutrient Availability: Low from less fertile sandstone

6. Name 5 species of trees/shrubs that have a distribution generally limited to limestone or limey substrates (such as Ohio’s Lake Erie islands).

• Redbud

  

• Eastern Red Cedar

  

• Hackberry

  

• Hop Hornbeam

  

• Blue Ash

  

7. Name 5 species of trees/shrubs that have a distribution generally limited to high-lime, clay-rich substrates developed in the thick glacial till of western Ohio.

• Sugar Maple
• American Beech
• Shagbark Hickory
• White Ash
• Swamp White Oak

8. Name 5 species of trees/shrubs that have a distribution generally limited to sandstone hill of eastern OH

• Chestnut Oak
• Sourwood
• Blueberry
• Greenbrier
• Easter Hemlock

9. What is the major determinant of the distribution of each of these species: a) sweet buckeye (contrast with hemlock), b) hemlock (contrast with sweet buckeye, c) rhododendron?

a) Sweet Buckeye does not occur within the glacial boundary which is hypothesized to occur because of its trouble repopulating in the high-lime and clayey glacial tills. It is also thought that climate may control the boundaries of this plant as well.

b) Eastern Hemlock is present in unglaciated, eastern Ohio and far north. This dispersion pattern is believed to be because of its need for continuously cool and moist environments as well as acidic soils.

c) Rhododendron grows well in some unglaciated areas in Ohio, as it is believed to have belonged to the mixed mesophytic environment. This plant species is especially unique as it is suspected to have lived in the Appalachian Highlands and traveled down through preglacial Teays River.