Common (Translated Scientific) Name: White Oak - Bur Oak - Shagbark Hickory Forest, Woodland & Savanna Macrogroup
Colloquial Name: Central Midwest Oak Forest, Woodland & Savanna
Hierarchy Level: Macrogroup
Type Concept: The vegetation structure of this macrogroup ranges from open savanna or barrens, with at least 10% tree cover, to closed forest. Typical dominant oak species include Quercus alba, Quercus ellipsoidalis, Quercus macrocarpa, Quercus rubra, and/or Quercus velutina. In forest and woodland stands, hickories such as Carya tomentosa, Carya cordiformis, Carya glabra, and Carya ovata are characteristic associates. Forested stands can have a dense shrub understory. Most barrens and savanna examples have understories dominated by prairie graminoids such as Andropogon gerardii, Hesperostipa spartea, Schizachyrium scoparium, Sorghastrum nutans, and Sporobolus heterolepis, and can have a rich forb component. This fire-dependent type is transitional between dry prairies and mesic hardwood forests. This macrogroup is found throughout the glaciated regions of the Midwest, most typically in the tallgrass prairie border-central lowlands region. It can occur on glacial landscape features such as moraines, kettle-kame topography, and outwash plains. Soils are well-drained to excessively drained, with a loamy to sandy texture. Fire suppression leads to more closed-canopy forests and woodlands, and a more mesic understory, and eventually replacement of oak canopy with mesic hardwoods, such as Acer saccharum and Acer rubrum. Periodic strong winds and browsing also impact this type. Many of the stands have been cleared and converted to agriculture.
Diagnostic Characteristics: This macrogroup is found within glaciated regions of the Midwest on loamy to sandy soils. It includes forests, savannas, and barrens, with a tree canopy of 5 m or more and from 10-100% cover, dominated by oak species such as Quercus alba, Quercus macrocarpa, Quercus rubra, and Quercus velutina. Many forests are codominated by Carya spp. Savanna and barrens examples contain a graminoid layer dominated by Andropogon gerardii and Schizachyrium scoparium with diverse herbs. Eastern oaks are not present, including Quercus coccinea and Quercus montana.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: This type includes oak forests, savannas and barrens in the glaciated regions of the Midwest and adjacent Canada. Northeastern U.S., Appalachian and Ozarkian examples are included elsewhere.
Oak barrens are closely related to sand and gravel prairie and barrens, and oak savanna (oak openings) are closely related to loamy tallgrass prairie. Floristically, these stands may strongly resemble open prairie types, but their tree canopy structure places them here [see 1. Forest & Woodland Class (C01)]. This type is, to some degree, the drier counterpart to Central Midwest Mesic Forest Macrogroup (M882), North-Central Beech - Maple - Basswood Forest Group (G021), with which it shares a similar climate, but a very different disturbance regime and topo-edaphic characteristics.
Similar NVC Types:
M016 Southern & South-Central Oak - Pine Forest & Woodland, note:
M159 Laurentian-Acadian Pine - Hardwood Forest & Woodland, note:
M054 Central Lowlands Tallgrass Prairie, note:
M502 Appalachian-Northeastern Oak - Hardwood - Pine Forest & Woodland, note:
M509 Central Interior Acidic Scrub & Grassland, note:
M882 Central Midwest Mesic Forest, note:
M883 Appalachian-Interior-Northeastern Mesic Forest, note:
Physiognomy and Structure: This macrogroup ranges from closed-canopy oak forests (60-100% cover) to open oak savannas and barrens typified by scattered trees (10-60% cover) over a continuous graminoid/shrub layer. Fire suppression in the region has allowed trees to establish more dense canopies.
Floristics: Dominant tree species in forest and woodland examples of this macrogroup include Quercus alba, Quercus rubra, and/or Quercus velutina. Common associates include Carya tomentosa (= Carya alba), Carya cordiformis, Carya glabra, and Carya ovata. Quercus macrocarpa and Quercus ellipsoidalis may be common in these examples as well. Conifers (e.g., Pinus banksiana, Pinus strobus) occasionally occur but at less than 25% cover, and a dense shrub layer is common. In savanna and barrens examples, canopy cover of tree species ranges from 10 to 60%, and Quercus macrocarpa is the most common tree. Occasional associates include Populus tremuloides (northern portion of the range), Quercus alba, Quercus bicolor, and Quercus stellata (southern part of range). The understory is dominated by graminoids, including Andropogon gerardii, Hesperostipa spartea (= Stipa spartea), Schizachyrium scoparium, Sorghastrum nutans, and Sporobolus heterolepis. There can be a rich forb component (which may increase in dominance with more closed-canopy examples). Some common forb species include Amorpha canescens, Antennaria spp., Calamagrostis canadensis (in moist stands), Carex spp., Lespedeza capitata, Ratibida pinnata, Silphium laciniatum, and Zizia aurea (Curtis 1959, Anderson and Bowles 1999, Leach and Givnish 1999). Sandy oak barrens are dominated by Quercus velutina, with some Quercus ellipsoidalis, Quercus macrocarpa, and Quercus alba. Pinus banksiana can occur in the northern parts of the range. In the southern part of the range in central Illinois, sand savannas may be dominated by Quercus marilandica and Quercus velutina, with Carya texana. Common herbaceous species include Ambrosia psilostachya, Amphicarpaea bracteata, Artemisia ludoviciana, Andropogon gerardii, Calamovilfa longifolia, Carex pensylvanica, Comandra umbellata, Hesperostipa spartea, Schizachyrium scoparium, and Sorghastrum nutans. Fire is required to maintain the species composition and structure of this type. Fire suppression can increase the number of mesic tree and understory species and can increase the woody canopy cover in barrens and savanna examples.
Dynamics: Fire, especially in combination with drought, is extremely important in maintaining this macrogroup. Historically, fires in the landscape varied from annual to 30-year intervals depending on topography, soils and firebreaks (Grimm 1984,Leitner et al. 1991). The 1- to 5-year fire cycle maintained the savanna and barrens portions of this macrogroup and also prevented more mesic species from invading oak forests and woodlands (Curtis 1959). Mesic, loam savannas may have burned more frequently or intensely than sandy oak barrens. Fire suppression allows the oak trees to establish more dense canopies and, over time, replacement by mesic tree associates, such as Acer saccharum, Acer rubrum, Celtis occidentalis, Ostrya virginiana, and Fraxinus americana. Periodic, strong wind disturbances and browsing also impact this type as can drought alone and oak wilt. Much of this type has been converted to agriculture.
Environmental Description: This macrogroup occurs on rolling landscapes and many glacial features such as outwash plains, hills and ridges, rolling glacial moraines, kettle-kame topography, end moraine formations, and outwash plains. It can also occur on uplands within a prairie matrix and near floodplains. Soils range from almost pure sand to richer loams. Typical soils include well-drained to excessively drained Mollisols or Alfisols. Savanna and barrens examples have soils with low fertility, organic matter, and moisture-retention capacity. Factors which affect seasonal soil moisture are strongly related to variation in this type. Historically, the oak-hickory forests to savannas were quite extensive in the Midwest.
Geographic Range: This macrogroup is found throughout the glaciated regions of the Midwest to southern Ontario and western New York.
Nations: CA, US
States/Provinces: IA, IL, IN, KS, MI, MN, MO, ND, NE, NY, OH, OK, ON, QC?, WI
|US Forest Service Ecoregions (2007)|
Prairie Parkland (Temperate) Province
Confident or certain
Wisconsin Central Sands Section
Confident or certain
Confidence Level: Moderate
Confidence Level Comments:
Synonomy: > Black Oak: 110 (Eyre 1980) [Apart from its extension into the Ozarks, the concept of this cover is quite similar to the group concept.]
> Northern Red Oak: 55 (Eyre 1980) [The concept of this cover type is quite similar to the group concept, though the montane portions are excluded.]
> Oak Barrens (Curtis 1959)
> Oak Openings (Curtis 1959)
> White Oak - Black Oak - Northern Red Oak: 52 (Eyre 1980) [The concept of this cover type is quite similar to the group concept.]
< White Oak: 53 (Eyre 1980) [The concept of this cover type is more broad, especially southward that the group concept.]
Concept Author(s): J.T. Curtis (1959); F.H. Eyre (1980)
Author of Description: S.E. Menard and D. Faber-Langendoen
Version Date: 15Oct2014
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