Monday, March 31, 2014

SW Ohio Glacial Till Soils: Hamilton/Warren County

Within Hamilton and Warren County, Southwest Ohio has a fairly diverse array of forest variations that occur within what is commonly labeled a mixed mesophytic eco-region. Different topographical, hydrological, climatic, erosional, and glacial influences support Oak-Hickory, Sugar Maple-Beech, Oak-Maple-Ash, Western Mixed Mesophytic, Mixed Mesophytic, Riparian, Pin Oak-Green Ash-Red Maple and other forest types within their specific niches in the landscape.

In reference to your neighborhood, it has probably been built upon a glacial till deposit within these two counties. Residuum soil is shallow soil derived from weathered bedrock and often has survived on steep slopes, which were difficult to develop on. Alluvial soils are often used for agriculture, and at times built upon with proper flood prevention. Aeolian soils are rare in this part of Ohio, which are sandy soils derived from wind action. Loess deposits are shallow in this corner of the state, which are wind transported silt deposits that often cover the glacial till deposits. While the glacial till deposits, which are unsorted materials deposited by glacial ice, are responsible for the deep silt and/or clay based soils upon which the majority of our commercial, residential, and industrial development is built. Lastly, glacial outwash, which is materials deposited directly from a water of melting glaciers, is isolated and often adjacent to alluvial soils. 

A large driver of tree dominance is related to the ph of the soil as the level of acidity and/or alkalinity effects the available soluble nutrients in the soil. Nearly all nutrients are provided to plants in a soluble solution. Weakly acidic, neutral, and alkaline soils (6.8-7.0+ ph) are ineffective at dissolving minerals and releasing their nutrients for the plants. However, if a soil is too acidic (about below 6.0 ph), the nutrients are likely to be dissolved and leached away too rapidly for plant roots to absorb them. Nutrient availability, related to the ph of the soil, therefor is a important factor of tree composition in a forest, yet just one of many.

This blog post will give insight into what these glacial till deposits within our metropolitans may have supported, by comparing 2nd growth forests vegetation with soil surveys using the USDA Web Soil Survey.

A Sharon Woods' silty glacial till varying from weakly acidic to lightly alkaline

Locally, glacial till soils fall between the 4 and 7.8 range on the PH chart. Nearly all within our 2nd and older growth forests fall between 5.0 and and 7.2 PH on average. At this particular site in Sharon Woods above the Gorge Trail, we have deep silty glacial till that still contains a large component of clay particles forming a varying weakly acidic to weakly alkaline soil. The Miamian-Silt Loam which makes up almost 50% of the map above allows tree species that dominate in alkaline soils to mix with species that dominate in acidic soils. Pictured to the right is a Blue Ash (Fraxinus quadrangulata) which is typical of soils that are weakly acidic (6.8) to alkaline (7.0+), rarely occurring in local soils that are below 6.8 ph. But the nature of the Miamian Silt Loam allows it grow with Black Oak (Quercus velutina) pictured below-center, which is typical of soils that are weakly acidic (6.8) to very acidic in the 5 and 4 range.

This sloped pictured to the right is dominated by a variation of our local upland alkaline soil dominant community, the Sugar Maple, Shumard Oak, Chinquapin Oak forest variation. I've devoted a very detailed blog post on the different formations of this variation, that dominates some weakly acidic, and many neutral to alkaline forests in SW Ohio, see here. Here these alkaline dominants such as Chinquapin Oak (Quercus muehlenbergii) and Shumard Oak (Quercus shumardii) are complemented by generalist species that occur in acidic and alkaline soils the same, such as White Ash (Fraxinus americana) and Sugar Maple (Acer sacharrum). This slope is the HEF-Hennepin soil as pictured on the soil survey map with an average ph of 7.3. This promotes the establishment and dominance of the upland alkaline dominants along with the generalists both listed above, over the acidic soil lovers that grow in the Miamian Silt Loam such as Mockernut (Carya tomentosa) and Black Oak (Quercus veultina).

Caesar Creek Gorge-deeply cut valley of alkaline residuum slopes, and acidic glacial till plains
In Southwest Ohio, slopes that run parallel with ancient streams and rivers that have cut gorges, and valleys exposing our Ordovician Limestone/Shale bedrock, often have little to no glacial deposits. What they typically have is residuum soil, which is soil derived directly from weathered bedrock as opposed to being deposited by wind, air, or glacial influences. Our local residuum soils are shallow, varying from 10-55 inches in soil depth, most in the 20-40 inch range. In comparison, our glacial till deposits are most commonly over 80 inches in depth. Around much of the Gorge trail at Caesar Creek State Park, we have the Fairmount-Eden Flaggy Silty Clay loams which is a residuum soil thinly covering the bedrock at depths of 10-40 inches, creating very tough, slightly alkaline, growing conditions promoting our Sugar Maple, Shumard Oak, Chinquapin Oak forest variation with a dominance of Oak-Hickory Species. You can see this stunted slope forest pictured to the right-above, and represented as the shade of blue on the soil map.

Upon the hilltops of the valleys we have Till Plains. A Till Plain is an extensive flat plain of glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place, depositing the sediments (glacial till) it carried. One could hypothesis that these ancient stream/river cut valleys, among many other valleys were to steep and wide for a sheet of glacial ice to form the right conditions to deposit the glacial till upon the slopes, which could be a why the glacial till only exists on the hill tops, but I'm no geologist. Nevertheless, the deep glacial till supports a forest variation that is vastly different from the Residuum covered slopes. The glacial till ph ranges from 5.1-5.4 promoting species such as Black Gum-and acid lover, which is the blocky bark tree pictured to the right-above, overlooking the valley. Other acid adapted species on this hill top that also occur in the slightly alkaline residuum soils as minority species, are White Oak (Quercus alba), Shagbark Hickory (Carya ovata), Bitternut Hickory (Carya cordiformis), Sugar Maple and Sweet Pignut (Carya ovalis). Black gum and Black oak only occur in the acidic Glacial till on this site, excluded from the slightly alkaline valley slopes of residuum soil. 

Where the glacial till has developed proper drainage yet, and holds a high water table, it promotes the establishment and long term dominance of the Red Maple-Green Ash-Pin Oak forest type typical of poorly drained till plains. Much of these till plains have been manipulated and drained well enough for housing/commerical development, and agriculture today. A couple of other species that may occur in the poorly drained acidic till plain forests of SW Ohio would be Shellbark Hickory (Carya laciniosa), Swamp White Oak (Quercus bicolor) and Pumpkin Ash (Fraxinus profunda). Habitat pictured above.

Pictured above; well drained area of the hill top acidic till plain supporting an occasional red maple and pin oak, but over all dominance of mixed mesophytic forest type, This well drained area forest includes Black Gum, Black Oak, White Oak, Red Oak, Shagbark Hickory, Bitternut Hickory, Sweet Pignut Hickory, Black Walnut, Slippery Elm, Sugar Maple, American Beech and a few others. This contrasts with the poorly drained glacial till that supports a dominance of the Pin Oak, Red Maple, Green Ash forest type. 

Eroded glacial till deposits at Miami White Water promote many Oak and Hickory Species
The majority of the Timberlake Trails at Miami White Water in Hamilton County have deep, clay based, acidic glacial till deposits. This has promoted an dominant second growth establishment of a Oak Hickory forest type. All hickory species occur here except Shellbark Hickory which grows in the poorly drained glacial till habitat of the Red Maple Pin Oak Green Ash forest type, in bottomlands and riparian habitat. All Oak species native to the county occur here also, but the alkaline dominant oaks; Shumard Oak, Chinquapin Oak, and Bur Oak are restricted to areas where the acidic glacial till has been severely eroded away and exposed our alkaline Ordovician bedrock. This may be the only verified naturally growing populations of Scarlet Oak in Hamilton County which favors excessively drained, drought prone ridges and hilltops and highly acidic soils in the 4-5 range of the appalachian mountain range.  The forest also supports species that occur in all ph ranges such as Sugar Maple, American Beech, Slippery Elm, Tulip Tree, and White Ash. Once again, the acidic glacial till here also supports the beautiful Black Gum stands of the acid loving Sassafras (Sassafras albidum).

Oak Hickory dominated acidic glacial till, mostly clay based here at Miami White Water

Large Sassafras groves can be found thriving in the acidic soil
An up rooted tulip tree reveals the clay heavy, deep glacial till

Oak Hickory forest type growing in Miami White Water's eroded acidic clay based glacial till

The value of our county soil surveys is unimaginably great, having preserved information such as Ph averages, bedrock depth and nature, glacier I.D., soil formation, hydrology data, soil texture, available water capacity, amongst other important information for interpretation. All of this information paired with local climatic conditions, specific topographical observations, while factoring site disturbance can be used to reforest a particular site, neighborhood, or metropolitan with the native species that will most effectively support ecology while providing the many humanitarian benefits that trees do. This would require a well trained professional who knew or had the ability to identify all of the native trees to that region, and also has the ability to interpret the second growth and old growth to compare it with the soil surveys. Compiling all of the different soil/climatic/hydrologic/topographic data for each species, one can create a guide for ecological restoration, and reforestation projects based on how the species have naturally regenerated in the second growth, and older growth forests. 

When we look at a second growth forest, the dominant trees in the canopy are best adapted to the all of the site conditions in most cases. In natural succession, which today is interrupted by invasive species, the clear cutting of our forests that occurred throughout the 18th, 19th and early 20th centuries would have lead eventually to thickets of trees regenerating if the land was not then heavily disturbed by grazing, development or agriculture. While in this thicket stage of regeneration, only the trees that are best adapted to the site, will be able to be outgrow and outlive their competition. Later in succession the thickets thin, as other trees are shaded out or fall to illnesses and other competition induced stress, leaving the best adapted trees to that site. This is a very simplified explanation, and many other factors play into forest regeneration such as animal disturbance from grazers and the lack of or presence of keystone predators that effect grazers. Also, many of our second growth forests are seeing shade tolerant species increase such as  Sugar Maple and American Beech while shade intolerant species decline because of the inability to reproduce effectively enough in those mature forest conditions.

Nevertheless, I urge you to explore your counties soil surveys, compare them with your second growth and old growth forests, and test the ph of your soil in your yard or your reforestation project.

For additional inquires about this blog post, email Solomon Gamboa at-

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  1. Thanks for sharing this information.

  2. Fascinating. Thanks for sharing, Solomon. I grew up in Warren County, Lebanon, OH. :)

    1. I hope you spent much at time at Caesar Creek State Park!