Friday, April 3, 2015

5 Major Forest/Soil Relationships of Southwest Ohio


Residuum is soil formed in place from bedrock breaking down; not transported by wind, water, or glacial ice. Due to the extensive glacial history in southwest Ohio, much of our residuum soil is underneath glacial deposits of soil that originated from Canada and counties north of Hamilton County. Residuum soil locally is mostly preserved on steep valley hillsides created overtime by rivers and streams cutting through our bedrock formations. These hillsides may have been too extreme in slope to hold and retain glacial deposits without the deposits washing away. It is typical, atop the valley hillsides where the hills climax and flatten off, that there are deep glacial deposits preserved mostly on the topography upon which we found most suitable for development.

(Limestone bedrock often breaks the surface of our shallow Eden and Fairmount Soils)

Common names of our residuum soil formations that you will find in soil surveys are Eden, Fairmount, Switzerland, and Pate. They vary in depth, but the bedrock is often near the surface anywhere from 12 inches to 60+ inches from the surface. When shallow residuum soils occur on wide open valley hillsides that face south-east, south, and south-west, we sometimes see the forest unable to fully close. In these stunted stages, they are dominated by our most alkaline drought tolerant species such as Shumard Oak, Chinkapin Oak, White Ash, and Blue Ash. Those partially open/stunted forests would be home to less common herbaceous species if honeysuckle were maintained, as seen in the Gorge of Caesar Creek State Park.

Eden and Fairmount Residuum
In General, our Eden and Fairmount soils promote these alkaline preferring species; Chinkapin Oak, Shumard Oak, Bur Oak, Shellbark Hickory, Ohio Buckeye, Bur Oak, and Blue Ash, as well as these more or less generalist species; Sugar Maple, Black Maple, Red Oak, American Beech, White Ash, White Oak, Bitternut Hickory, Shagbark Hickory, and Sweet Pignut Hickory.  These soils range in the 6.5 ph+ upwards to 7.5 ph.

(Switzerland, acidic upland residuum soil with deep loess deposit overlaying the residuum)

Pate (Colluvium-Residuum) and Switzerland (Loess + Residuum)
Again, in general, our deeper and more complex Pate and Switzerland soils support a mix of acidic soil and alkaline soil preffering species due to their lower ph ranging in the 5-6 range. Not only can you find most of thee above species in these soils, with the alkaline preferring species less dominant and at times absent, you can find an occurrence of species that prefer more acidic soils such as Yellow Buckeye, Scarlet Oak, Black Oak, and Sassafras as seen in Oak Glen Nature Preserve, and the old growth of Ault Park. 


Our alluviual soils of our 3 watersheds; the Little Miami, Great Miami, and Mill Creek Valleys, are of alkaline nature. Alluvial soils are water stratified, meaning the soils were created by first the erosion of soils, or melting of glacial water, then as the water slows down silt and sand sized particles settle out and stratify based on many different factors while most of the clay sized particles are taken long distances away from floodplains as they take the longest amount of time to settle. Because our floodplain soils are all above 7.0 PH and often approaching the 8 range, it wouldn’t be a far out generalization to say most of our upland silt and sand particles are alkaline, while most of upland clay sized particles are acidic as noted by the acidic clay based glacial till deposits throughout southwest Ohio. More on Glacial Till later in the blog post.

Alluvial soils aren’t always on currently flooded floodplains. There are alluvial terraces at higher elevations than the more actively flooded plains, that were once flooded often by either rivers that were here before the last ice age, or today’s rivers which have created and abandoned floodplains naturally as the rivers move, cut, and deposit soil. Also dams have turned more often flooded floodplains, into less often or rarely flooded flood plains and vice versa. Therefor floodplain forest locally can be characterized into frequently flooded, occasionally flooded, and rarely flooded floodplains as the soil surveys characterized the soil formations, which each have a slightly different forest composition.

These following species occur on all different frequencies of flooding; American Sycamore, Green Ash, Box Elder Maple, and Ohio Buckeye. These next species are more restricted to frequently flooded floodplains, and less dominant or absent in occasionally and rarely flooded floodplains; Cottonwood, Willow sp., and Silver Maple. Lastly this long list of species occurs on rarely and occasionally flooded floodplains; Bur Oak, Shellbark Hickory, Black Maple, Blue Ash, Kentucky Coffe Tree, Honey Locust, Tulip Tree, Black Walnut, American Elm, American Linden, and Hackberry.

Lastly, floodplain forests locally have water created niches for different species to find a feasible hydrology in. For example there are swales/depressions, and rises in elevations on floodplains that promote this species over that species. There are soils heavy in sand, and soils heavy in silt, which may promote this species over that species. There are PH estimates closer to 7.0 and PH estimates closer to 8. These subtleties haven’t been studied by myself yet locally, but are on the to-do-list.

(Glacial Outwash Valley at Fort Ancient)

Glacial Outwash

Like alluvial soils, glacial outwash soils are water stratified. So most clay particles have been carried off by water action leaving a predominantly silt and sand composition. Outwash is formed by melting glacier water, and occurs on uplands and slopes, where as the soils formed by melting glacier water that occur parrarell with rivers and streams are classified as alluvial, though both are similar in nature, just not location-locally. These are our most alkaline upland soils locally, and are rich in small pebble sized to large boulder sized glacial erratics in deep deposits of soil with the bedrock well over 80 inches from the surface according to soil surveys. These upland soils, due to their alkalinity, promote a similar forest as our Eden and Fairmount soils, except due to their depth and moisture availability the canopies are more closed, trees can reach greater size, and in general can grow at faster rates. From my observation, glacial outwash is more dominated by alkaline preferring species such as Chinakpin Oak, Blue Ash, and Shumard Oak than some residuum soils, perhaps because of the higher alkalinity. Though the occasional White Oak, Shagbark Hickory, and Red Oak which dominate in acidic soils, may still occur as minority species.  The valley of Randall Run, in Fort Anchient State Park, and some of the valleys in California Woods are some of the best samples of glacial outwash forests studied to date locally. Casco Loam and Fox Loam are two of the most common Glacial Outwash formations studied so far.

Loess Deposits

Loess is wind deposited silt. Silt, as witnessed in the dust bowl, can become airborne for thousands of miles while sand tends to travel very short distances, and clay tends to clump together and resist being suspended in air the most. What we generally call “Topsoil” are loess deposits overlaying our subsoil which locally is most often acidic clay based glacial till deposits in glaciated soils. Loess is the icing on the cake, of most of glacial till deposits and even some of our residuum soils such as Switzerland. It tends have collected least upon the steep valley hillsides upon which our residuum soils are preserved and un-glaciated, perhaps due to the inability to remain at such a slope without being eroded after the last ice age.  Where we have deep loess deposits, sometimes the soil formations are acidic, sometimes they are closer to neutral, perhaps meaning the origin of our loess deposits varies and is not uniform nature/source. Switzerland for example features a deep loess deposit overlaying our residuum soil, and commonly tests in the 5 range supporting Scarlet Oak and Sassafrass. Where as Hennepin and Miamian soils range from the high 6 to low 7 range featuring a deep loess deposit overlaying glacial till.  In Sharon Woods, where the Miamian-Hennepin formation occurs, alkaline preferring species such as Shumard Oak, Chinkapin Oak, and Blue Ash grow side by side with acidic preferring species such as Black Oak, and Black Gum with an average PH estimated at 6.8. I’m told Butler County features some of our deepest loess deposits, but I haven’t yet studied remnant forests upon those soils yet.

For much of Southwest Ohio, Loess deposits aren’t neccesairly a soil formation alone, rather once again “icing on the cake” representing a 3” to 12” deposit of silt ontop of glacial till which is the most expansive soil formation in the glaciated parts of Southwest Ohio.

Web Soil Survey insight to the Glacial Till (Bonnell), Outwash (Casco), and Alluvial (Langier) formations of California woods. Theses are Generalized Ph Estimates of which the forest canopy agrees with. 

Glacial Till

Glacial Till is soil deposited by retreating glaciers, and is unsorted containing whatever the glacier happened to drop while in retreat. Locally they are mostly clay based soils and acidic. What we typically refer to “subsoil” underneath “topsoil” is most often the glacial till deposit underneath the Loess deposit of silt. When glaciers moved through the landscape, they filled in many valleys with rocks, sand, silt and clay. Since the drainage of the land had to start back from square one, upon some glacial till plains there exists seasonally high water tables as the water has no direct path to drain from the land and must seep slowly through bedrock and towards the newly born streams post glaciation.  Upon poorly drainage glacial till deposits with high water tables, the forest becomes dominated by the Pin Oak, Red Maple, Green Ash Forest type also containing Black Gum, Shagbark Hickory, American Elm, Sassafras, Pumpkin Ash, Sweet Gum, and a few other species. The better drained glacial till plains have more of an Oak Hickory dominance with Sugar Maple and Beech succeeded them as the forest reaches its climax in maturity.

(Poorly Drained acidic glacial till at Culberson State Nature Preserve)

Glacial Till represents the majority of our agricultural, residential, and commercially developed areas, as we tend to build and cultivate the flatter land that glaciers helped to create throughout Southern and Central Ohio. The depth of the soil is also more safe to build on than shallow hillside residuum soils, of which can slip if compromised by road cuts like seen annually above the Columbia Parkway in Cincinnati. Glacial Till soils are also the most numerous in soil formations locally, so there’s no way to generalize them in a single blog post. There are Ava Silt Loams from the Kansan glacier that range in the 4 ph range, Cincinnati Silt loams of the Wisconsin glacier in the 5 ph range, and Hennepin Glacial Till in Warren County in the 7 PH range with deep loess influence. Speaking most generally, the glacial tills could be most basically categorized by loess content which effects the PH and moisture availability, and hydrology effecting how well it drains. Then one could generalize different sub-climax and climax forest vegetation for these soils locally, but more studying still needs to be done on the many glacial till soils of Southwest Ohio.

Seeing Forests from the Soils Workshop - Link to full size flyer

Pioneer Landscapes will hold 3, 3 hour lecture-hikes in Cincinnati Metro area-2nd growth, and older growth forests this summer. Our goal is to show how to read the county soil surveys and compare them with the topography, past land use, and current forest vegetation to gain site specific insight for projecting where native trees truly want to be planted. In these 3 forest hikes, we’ll learn the nature of our most common Glacial Till, Glacial Outwash, Alluvial, Residuum, and Loess deposits, and how their characteristics dictate the structure of a high quality forest, and/or a reforestation project. 

You’ll also receive a custom made Youtube video showing you how to use the USDA web soil survey, to survey your own property with, as well as a simple how-to-guide accompanied with spreadsheets that allow you to use the information already compiled by Pioneer Landscapes to choose the right trees for your soil/hydrology/topography. Price is $15 a hike (18 years old or under FREE), or 40$ per person to attend all 3 hike-lectures. Dates are Sat. June 20th, Sun. June 21st, and Sat. June 27th at (9:30 A.M-12:30 P.M.). Locations including maps will be received upon pre-registering through email. Pre-registration is required due to the 50 person cap. Email to register.

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