**2. Materials and methods**

#### **2.1 Study areas**

The study areas are all located in southeastern Missouri, USA. The study area containing the Knobtop, Taumsauk and Irondale Ultisol pedons is located at Taumsauk State Park and was selected because of its variable pedon depths and the presence of loess over igneous residuum/colluvium. The Knobtop (Fine-silty, mixed, active, mesic Aquic Hapludults) pedon is a moderately deep, moderately well-drained soil formed in loess overlying Precambrian rhyolite residuum. The pedon is located on a summit position having a 1 to 2 percent slope. The Irondale (Loamy-skeletal, mixed, active, mesic Typic Hapludults) pedon is moderately deep, well-drained, and moderately permeable soil formed in rhyolite residuum on a steep 35% slope supporting an oak forest. The Taumsauk (Loamy-skeletal, mixed, active, mesic Lithic Hapludults) pedon is a shallow, somewhat excessively-drained, moderately permeable soil formed in rhyolite colluvium. The Taumsauk pedon is located on a 10% convex slope and exhibits a mountain glade area.

The Caneyville and Hildebrecht pedons are in Sam A Baker State Park and were selected because the pedons were formed in loess over limestone residuum, which is a very common occurrence across east-central Missouri. The Caneyville (Fine, mixed, active, mesic Typic Hapludalfs) Alfisol pedon is a moderately deep, well-drained soil formed in a thin silty mantle overlying fine-textured limestone residuum. The Hildebrecht (Fine-silty, mixed, active, mesic Oxyaquic Fragiudalfs) Alfisol pedon is a very deep, moderately well-drained soil on a side slope. The pedon is formed in loess over weathered dolomitic residuum. Permeability is moderate above the fragipan and slow or very slow in the fragipan.

The study area containing the Amagon (Fine-silty, mixed, active, thermic Typic Endoaqualfs) and Calhoun (Fine-silty, mixed, active, thermic Typic Glossaqualfs) pedons are located in the Mingo National Wildlife Refuge. This study area was selected because these poorly-drained pedons were formed in alluvium, which is representative of the Mississippi River Embayment. The Amagon pedon is a very deep, poorly-drained, slowly permeable Alfisol that formed in loamy alluvium. The Calhoun pedon is a poorly-drained, slowly permeable Alfisol formed from loess-like material on a Pleistocene-age terrace.

The Knobtop, Taumsauk and Irondale study area and the Caneyville and Hildebrecht study area have a continental humid climate with winter having dry and cold air masses and summer having moist, warm air masses producing abundant rainfall events. The average annual precipitation 112 cm, whereas the average annual temperature is about 13°C [16]. The Amagon and Calhoun study area has a continental humid climate with an average rainfall of 126 cm. Mean winter temperatures are 4°C and mean summer temperature of 26°C, whereas the mean annual temperature is 13°C [17]. The The Knobtop, Taumsauk and Irondale study area and the Caneyville and Hildebrecht study area does not experience flooding, whereas the Amagon and Calhoun study area annually experiences either flooding or seasonal water saturation.

#### **2.2 Methodology**

Pedons were located, described, and sampled according to Soil Survey Division Staff [18] in undisturbed forest settings using excavated pits. Samples were ovendried, lightly crushed, and sieved to remove materials larger than two mm. Soil pH using equal volumes of soil and water, the NH4-acetate (pH 7.0) extraction of exchangeable bases, the total acidity by slow titration to pH 8.2, and the soil organic matter content (SOM) by loss on ignition were performed using standard methods [19]. The particle size distribution (mechanical analysis) was determined by Na-saturation of the exchange complex, dispersion in Na2CO3 (pH 9.0) and centrifuge fractionation to remove clay and wet sieving of the silt and sand separates [19].

The ecological site descriptions were obtained using the Ecosystem Dynamics Interpretive Tool (EDIT), which is an online information system for the sharing of ecological site descriptions [20] or ([https://edit.jornada.nmsu.edu/], verified February 2021).

#### **3. Results and discussion**

#### **3.1 Knobtop Irondale Taumsauk Ultisol Assemblage**

The Knobtop, Irondale and Taumsauk soils are Ultisols having fine silty or loamy-skeletal textures and exhibiting A-E-Bt-rhyolite rock horizon sequences. The Knobtop pedon resides on a summit position developed in a moderately thick loess mantle overlying rhyolitic residuum, whereas the Irondale and Taumsauk pedons

### *Integrating Ecological Site Descriptions with Soil Morphology to Optimize Forest Management… DOI: http://dx.doi.org/10.5772/intechopen.97251*

occupy side and convex (shoulder) slope positions, respectively. The Irondale and Taumsauk pedons exhibit thin and very thin loess mantles overlying rhyolite colluvium, features attributed to erosion and mass-wasting during and subsequent to loess deposition.

The Knobtop (Aquic Hapludult), Taumsauk (Lithic Hapludult) and Irondale (Typic Hapludult) pedons reside in MLRA 116 in the St. Francois Knobs and Basins region. The Knobtop pedon exhibited a silt loam texture in the ochric epipedon and silty clay loam texture in the majority of the argillic horizon (**Table 1**). The Taumsauk pedon exhibited a very cobbly silt loam ochric epipedon (A horizon) and very cobbly silt loam (E horizon) transitioning to a very cobbly silty clay loam within the comparatively shallow-to-bedrock argillic horizon. Soil pH in the Knobtop and Taumsauk pedons are extremely acid, with a corresponding base saturation much less than 35% (**Table 2**). The exchangeable calcium concentration is very low, which is reflective of the very small Ca concentration of the analyzed rhyolite samples (rhyolite composition not shown). The Irondale pedon exhibits


*Structure: 1 = weak, 2 = moderate, f = fine, m = medium, gr = spherical, sbk = subangular blocky. Boundary: a = abrupt,, c = clear, s = smooth.*

#### **Table 1.**

*Morphological and physical properties of the Knobtop, Taumsauk, and Irondale pedons.*


**Table 2.** *Chemical properties of the Knobtop, Taumsauk, and Irondale pedons.*

#### *Environmental Management - Pollution, Habitat, Ecology, and Sustainability*

**210**

#### *Integrating Ecological Site Descriptions with Soil Morphology to Optimize Forest Management… DOI: http://dx.doi.org/10.5772/intechopen.97251*

a very acidic reaction, with a relatively greater base saturation; however, the base saturation remains less than 35% as required for the Ultisol order. The soil organic matter content is greatest in the A horizons and declines with increasing soil depth. Given the shallowness of these pedons, especially for the Taumsauk pedon, seasonal dryness during the summer and fall months is presumed to be a limiting factor for tree growth. The extreme soil acidity contributes to the reduced tree growth and limits the vegetational diversity.

For the Knobtop-Irondale-Taumsauk Ultisol assemblage, the corresponding provisional ecological site descriptions are (i) Dry Igneous Upland Woodland (F116CY003MO) having the Knobtop and Irondale soil series, (ii) the Dry Igneous Exposed Backslope Woodland (F116CY011MO) having the Irondale soil series, and (iii) the Shallow Igneous Knob Glade (R116CY006MO) having the Taumsauk soil series. For the Dry Igneous Exposed Backslope Woodland the dominant vegetation is post oak (*Quercus stellate*), black oak (*Quercus velutina*) with scattered blackjack oak (*Quercus marilandica*), northern red oak (*Quercus rubra*) and a ground flora of native grasses and shrubs (fragrant sumac (*Rhus aromatica*) and little bluestem (*Schizachyrium scorparium*)). For the Dry Igneous Upland Woodland, the vegetational community is similar, with exceptions including a slightly greater abundance of northern red oak (*Quercus rubra*) and a greater abundance of the herbaceous species *Danthonia spicata*. The Shallow Igneous Knob Glade has a few species of blackjack oak (*Quercus marilandica*) and the herbaceous species *Schizachyrium scorparium* and *Croton michauxil* var. ellipticus. Canopy closure varies with aspect and soil depth, ranging from 30 to 50% on exposed positions and shallower soil depths to 50–80% on protected positions and deeper soil depths. Fire, including controlled burning, has been present in these vegetational communities, reducing litter accumulation, stimulating grasses and forbs, and reducing the encroachment of woody species.

The Dry Igneous Upland Woodland has post oak (*Quercus stellate*) and northern red oak (*Quercus rubra*) as the dominant tree species in the reference state, with a fire-free interval of 10–15 years witnessing the encroachment of eastern red cedar (*Juniperus virginiana*). The reference state is in quasi-equilibrium with (i) the fire excluded mixed oak woodland state and the (ii) fire excluded and logged mixed oak woodland state based on the contrasting practices of long-term fire suppression and the opposing practice of forest stand improvement using prescribed burning with and without tree species removal. The Dry Igneous Exposed Backslope Woodland reference site and transition sites are similar to that of the Dry Igneous Upland Woodland, with differences attributed to subtle species compositions. The Shallow Igneous Knob Glade has a blackjack oak (*Quercus marilandica*) tree composition with little bluestem (*Schizachyrium scoparium*) and lichens with and associated reference state having eastern redcedar. Fire suppression transitions to a state with the addition of winged elm (*Ulmus alata*). The soil surface cover is variable, but typical estimates are tree basal cover (1%), shrub/vine/liana basal cover (1%), grass and grasslike basal cover (1%), forb basal cover (1%), non-vascular cover (5%), litter (30–50%) and surface fragments (10%).

## **3.2 Caneyville and Hildebrecht Alfisol Assemblage**

The Caneyville and Hildebrecht soils are Alfisols having fine and fine-silty textures and exhibiting A-E-Bt and A-E-Bt-2Btx-3Bt horizon sequences, respectively (**Table 3**). The consensus of soil scientists who mapped these soils is that the Caneyville series developed in loess, whereas the Hildebrecht series developed in Peoria loess overlying a previous bisequal soil derived from older loess developed on limestone residuum.


*For the Hildebrecht pedon, the 2 Btxl to 3Bt3 horizons are very gravelly to extremely gravelly. Structure; 1 is weak, 2 is moderate, f is fine, m is medium, gr is granular, sbk is subangular blocky.*

#### **Table 3.**

*Morphological and physical properties of the Caneyville and Hildebrecht pedons.*

The Caneyville (Typic Hapludalf) pedon has sandy loam and silt loam textures in the ochric epipedon and silty clay loam in most of the argillic horizon. The pH is neutral to slightly acidic in the near surface horizons and strongly acid in the lower argillic horizons, with exchangeable Ca showing a gradual concentration reduction on transition to the deeper horizons (**Table 4**). The Hildebrecht (Oxyaquic Fragiudalf) pedon shows a silt loam texture in the eluvial horizons and a silty clay loam texture in the illuvial horizons. The fragipan has a loam texture which abruptly transitions to clay in the 3Bt3 horizon. The eluvial and argillic horizons appear to be developed in Peoria Loess, whereas the fragipan and 3Bt3 horizons are apparently developed in older Roxana Loess overlying limestone residuum, thus the Hildebrecht pedon appears to be a bisequal soil. The soil organic matter concentrations are greatest in the A horizons and decline upon soil profile transition.

For the Caneyville-Hildebrecht Alfisol assemblage the corresponding provisional ecological site descriptions are (i) the Fragipan Upland Woodland (F116AY004MO) containing the Hildebrecht soil series, and (ii) the Loamy Limestone/Dolomite Upland Woodlands (F115BY007MO) containing the Caneyville soil series. The dominant vegetation of the reference state of the Fragipan Upland Woodland is post oak (*Quercus stellata*) and black oak (*Quercus velutina*) with native grasses and legumes and other forbs in open canopy areas. Land management practices are related to (i) silvopasture to create a post oak (*Quercus stellata*) -shortleaf pine (*Pinus echinate*) state, (ii) clearcutting to create a *Integrating Ecological Site Descriptions with Soil Morphology to Optimize Forest Management… DOI: http://dx.doi.org/10.5772/intechopen.97251*


*CEC is the cation exchange capactiy, an estimate of the soil organic matter content.*

*Acidity is total acidity.*

#### **Table 4.**

*Chemical properties of the Caneyville and Hildebrecht pedons.*

tall fescue (*Festuca arundinacea*) mixed pasture, and (iii) fire exclusion and logging to create a post oak (*Quercus stellata*), black oak (*Quercus velutina*), and black hickory (*Carya texana*) woodland. The dominant vegetation of the reference state of the Loamy Limestone/Dolomite Upland Woodlands is White Oak (*Quercus alba*), Chinkapin Oak (*Quercus muehlenbergii*) with Red Bud (*Cercis canadensis*), Aromatic Sumac (*Rhus aromatica*), Virginia Wildrye (*Elymus virginicus*) and Little Bluestem (*Schizachyrium scoparium*). Land management practices related to (i) a high graded and grazed woodland to establish a black oak (*Quercus velutina*), post oak (*Quercus stellata*), black hickory (*Carya texana*), (ii) logging creating a tall fescue (*Festuca arundinacea*) pasture, (iii) an even-aged managed woodland establishes a white oak (*Quercus alba*), chinkapin oak (*Quercus muehlenbergii*), and post oak *(Quercus stellata)* community and (iv) an uneven-aged managed woodland establishes a white oak (*Quercus alba*), black hickory (*Carya texana*), and northern red oak (*Quercus rubra*) community.
