This system occurs on well-drained, coarse-textured sandy soils derived from glacial outwash, end moraine formations, lakeplain dune systems, and broad sandy river terraces in the north-central U.S. into Ontario, Canada. Soils range from almost pure sand, to loamy sand, to sandy loam. The soils have low fertility, organic matter, and moisture-retention capacity. Factors which affect seasonal soil moisture are strongly related to variation in this type. This oak barrens system is a scrubby, open-treed system dominated by graminoids and shrubs. Canopy structure varies from a dominant herbaceous ground layer with sparse, scattered "savanna" canopy (5-30%), through oak-dominated scrub, to a more closed woodland canopy (30-80%). The canopy layer is dominated by Quercus velutina, with some Quercus ellipsoidalis, Quercus macrocarpa, and Quercus alba (the latter more common eastward and in woodland conditions). Occasional Pinus banksiana can occur in the northern parts of the range. Species found in the herb layer include Ambrosia psilostachya, Amphicarpaea bracteata, Artemisia ludoviciana, Andropogon gerardii, Calamovilfa longifolia, Carex pensylvanica, Carex spp., Comandra umbellata, Dichanthelium spp., Hesperostipa spartea, Koeleria macrantha, Lupinus perennis, Schizachyrium scoparium, Sorghastrum nutans, and Tephrosia virginiana. Fire was an important factor in maintaining this system. Oak wilt, droughts and, in some northern sites, frosts during the growing season also reduce tree cover.
Source: NatureServe Explorer
Vegetation
This oak barrens system is a scrubby, open-treed system dominated by graminoids and shrubs. Canopy structure varies from a dominant herbaceous ground layer with sparse, scattered "savanna" canopy (5-30%), through oak-dominated scrub, to a more closed woodland canopy (30-80%). The canopy layer is dominated by Quercus velutina, with some Quercus ellipsoidalis, Quercus macrocarpa, and Quercus alba (the latter more common eastward and in woodland conditions). Occasional Pinus banksiana can occur in the northern parts of the range. Species found in the herb layer include Ambrosia psilostachya, Amphicarpaea bracteata, Artemisia ludoviciana, Andropogon gerardii, Calamovilfa longifolia, Carex pensylvanica, Carex spp., Comandra umbellata, Sorghastrum nutans, Hesperostipa spartea (= Stipa spartea), and Schizachyrium scoparium.
Source: NatureServe Explorer
Environment
This system occurs on well-drained, coarse-textured sandy soils derived from glacial outwash, end moraine formations, lakeplain dune systems, broad sandy river terraces, and sometimes on colluvium below sandstone bluffs. Soils range from almost pure sand, to loamy sand, to sandy loam. The soils have low fertility, organic matter, and moisture-retention capacity. Factors which affect seasonal soil moisture are strongly related to variation in this type.
Source: NatureServe Explorer
Dynamics
Fire was an important factor in maintaining this system. Oak wilt and droughts also reduce tree cover. For more fertile sites, surface fires were very frequent (1- to 5-year return intervals) and important for maintaining the open canopy and herbaceous understory. This system was not as fire-dependent as more mesic savannas and woodlands, due to the relatively infertile and often droughty soils on which it occurred. Some examples retained an open canopy without frequent fires (Whitford and Whitford 1971). Canopy trees were replaced when periodic longer fire-return intervals, due to chance, multi-year wet climatic cycles, or lack of burning by Native Americans, allowed oak seedlings to grow large enough to survive surface fires when they returned. If fire is absent for more than about 20-40 years, a site will transition to oak woodland/forest (Curtis 1959).
Source: NatureServe Explorer
Threats
Before European settlement, oak savanna, essentially a combination of this system and North-Central Interior Oak Savanna (CES202.698), was estimated to have covered 11-13 million ha in the Midwest. The extent in 1985 was estimated at just over 2600 ha and all but 40 ha was on dry or rocky sites (Nuzzo 1986) and likely North-Central Oak Barrens (CES202.727). Fire suppression and conversion to agriculture or urban development have nearly eliminated this system from the landscape. Fire suppression for more than a few years allows woody species to proliferate. This system was most common on infertile, drought-prone, acidic sites, so conversion to agriculture is not as common as other Midwest oak systems, but pasturing and conversion to pine plantations or urban uses still occurs. Livestock grazing can degrade sites, especially when combined with fire suppression. Conversion to urban uses was also common in the industrial and agricultural Midwest. A lack of fire allows native woody species to expand but also allows exotic species into the shrub and herbaceous strata. In Michigan, invasive species that threaten the diversity and structure include Berteroa incana, Celastrus orbiculata, Centaurea biebersteinii (= Centaurea maculosa), Cynanchum louiseae (= Vincetoxicum nigrum), Cynanchum rossicum (= Vincetoxicum rossicum), Elaeagnus umbellata, Hieracium spp., Hypericum perforatum, Leucanthemum vulgare (= Chrysanthemum leucanthemum), Lonicera japonica, Lonicera maackii, Lonicera morrowii, Lonicera sempervirens, Lonicera tatarica, Lonicera x bella, Lonicera xylosteum, Poa compressa, Poa pratensis, Rhamnus cathartica, Rosa multiflora, Rumex acetosella, and Saponaria officinalis.
Source: NatureServe Explorer
Distribution
This system is found in the north-central U.S. from North Dakota to western New York and westernmost Pennsylvania (mostly historic there) and into Ontario, Canada.
Source: NatureServe Explorer
Ecologically Associated Plant Species
Plant species that characterize this ecosystem type, organized by vegetation stratum. These are species ecologically associated with the ecosystem, not confirmed present in any specific area.
Animal species ecologically associated with this ecosystem type based on NatureServe assessment. These are species whose habitat requirements overlap with this ecosystem, not confirmed present in any specific roadless area.
At-Risk Species Associated with this Ecosystem (11)
Species with conservation concern that are ecologically associated with this ecosystem type. G-Rank indicates global conservation status: G1 (critically imperiled) through G5 (secure). ESA status indicates U.S. Endangered Species Act listing.
Plant community associations that occur within this ecological system. Associations are the finest level of the U.S. National Vegetation Classification (USNVC) and describe specific, repeating assemblages of plant species. Each association represents a distinct community type that may be found where this ecosystem occurs.
Subnational conservation status ranks (S-ranks) assigned by Natural Heritage Programs in each state where this ecosystem occurs. S1 indicates critically imperiled at the state level, S2 imperiled, S3 vulnerable, S4 apparently secure, and S5 secure. An ecosystem may be globally secure but imperiled in specific states at the edge of its range.
State
S-Rank
IL
SNR
IN
SNR
MI
SNR
MN
SNR
ND
SNR
NY
SNR
OH
SNR
PA
SNR
WI
SNR
Roadless Areas (3)
Inventoried Roadless Areas where this ecosystem is present, identified from LANDFIRE 2024 Existing Vegetation Type spatial analysis. Coverage indicates the proportion of each area occupied by this ecosystem type.
Ecosystem classification: Ecosystems are classified using the LANDFIRE 2024 Existing Vegetation Type (EVT) layer, mapped to NatureServe Terrestrial Ecological Systems via a curated crosswalk. Each EVT is linked to the USNVC (U.S. National Vegetation Classification) hierarchy through pixel-level co-occurrence analysis of LANDFIRE EVT and NatureServe IVC Group rasters across all roadless areas.
Vegetation coverage: Coverage percentages and hectares are derived from zonal statistics of the LANDFIRE 2024 EVT raster intersected with roadless area boundaries.
Ecosystem narratives and community species: Sourced from the NatureServe Explorer API, representing professional ecological assessments of vegetation composition, environmental setting, dynamics, threats, and characteristic species assemblages.
IVC hierarchy: The International Vegetation Classification hierarchy is sourced from the USNVC v3.0 Catalog, providing the full classification from Biome through Association levels.
Component associations: Plant community associations listed as components of each NatureServe Ecological System. Association data from the NatureServe Explorer API.
State ranks: Conservation status ranks assigned by NatureServe member programs in each state where the ecosystem occurs.