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For information on Wisconsin's natural communities, contact:
Ryan O'Connor
Natural Heritage Inventory Ecologist

Oak Opening

State Rank: S1     Global Rank: G1   what are these ranks?


Detailed Community Description from Ecological Landscapes of Wisconsin

General natural community overview

Counties shaded blue have documented occurrences for Oak Opening in the Wisconsin Natural Heritage Inventory database.

As defined by Curtis, this is an oak-dominated savanna community in which there is less than 50% tree canopy coverage and more than one tree per acre. Historically, oak openings were very abundant and occurred on wet-mesic to dry sites. Today, very few examples of this type exist. The few extant remnants are mostly on drier sites, with the mesic and wet-mesic oak openings almost totally destroyed by conversion to agricultural or residential uses, or by encroachment of other woody plants due to fire suppression. Bur, white, and black oaks (Quercus macrocarpa, Q. alba and Q. velutina) are dominant in mature stands, typically as large, open-grown trees with distinctive limb architecture. Shagbark hickory (Carya ovata) is sometimes present. American hazelnut (Corylus americana) is a common understory shrub. The herb layer is similar to those found in oak forests and prairies, with many of the same grasses and forbs present. There are some plants (e.g., kitten-tails (Besseya bullii) and animals (e.g., Red-headed Woodpecker, Orchard Oriole, Eastern Bluebird) that reach their optimal abundance in the openings.

Rare animals

Species of Greatest Conservation Need

Wisconsin Wildlife Action Plan graphic

The following Species of Greatest Conservation Need are listed according to their level of association with the Oak Opening natural community type, based on the findings in Wisconsin's 2015 Wildlife Action Plan.

Scores: 3 = high association, 2 = moderate association, and 1 = low association. See the key to association scores for complete definitions.

Ants, wasps, and beesScore
American Bumble BeeBombus pensylvanicus1
Confusing Bumble BeeBombus perplexus1
Rusty-patched Bumble BeeBombus affinis1
Silphium Terminal Gall WaspAntistrophus silphii1
Yellow Bumble BeeBombus fervidus1
Yellowbanded Bumble BeeBombus terricola1

A Pear-shaped WeevilCoelocephalapion decoloratum3
A Leaf BeetlePachybrachis atomarius2
A Leaf BeetleCryptocephalus cuneatus2
A Leaf BeetlePachybrachis peccans1
A Pear-shaped WeevilSayapion segnipes1

Red-headed WoodpeckerMelanerpes erythrocephalus3
Common NighthawkChordeiles minor2
Eastern MeadowlarkSturnella magna2
Eastern Whip-poor-willAntrostomus vociferus2
Greater Prairie-ChickenTympanuchus cupido2
Henslow's SparrowAmmodramus henslowii2
Long-eared OwlAsio otus2
Northern BobwhiteColinus virginianus2
Sharp-tailed GrouseTympanuchus phasianellus2
Vesper SparrowPooecetes gramineus2
American WoodcockScolopax minor1
Bell's VireoVireo bellii1
BobolinkDolichonyx oryzivorus1
Brewer's BlackbirdEuphagus cyanocephalus1
DickcisselSpiza americana1
Grasshopper SparrowAmmodramus savannarum1
Loggerhead ShrikeLanius ludovicianus1

Butterflies and mothsScore
Karner BlueLycaeides melissa samuelis3
Cobweb SkipperHesperia metea2
Regal FritillarySpeyeria idalia2
Silphium Borer MothPapaipema silphii2
Sprague's PygarcticaPygarctia spraguei2
Whitney's Underwing MothCatocala whitneyi2
Abbreviated Underwing MothCatocala abbreviatella1
Byssus SkipperProblema byssus1
Columbine Dusky WingErynnis lucilius1
Cross Line SkipperPolites origenes1
Doll's MeroloncheAcronicta dolli1
Frosted ElfinCallophrys irus1
Gorgone Checker SpotChlosyne gorgone1
Liatris Borer MothPapaipema beeriana1
Mottled Dusky WingErynnis martialis1
Ottoe SkipperHesperia ottoe1
Phlox MothSchinia indiana1
Poweshiek SkipperlingOarisma poweshiek1

Dragonflies and damselfliesScore
Mottled DarnerAeshna clepsydra3

Grasshoppers and alliesScore
A Spur-throat GrasshopperMelanoplus foedus3
Handsome GrasshopperSyrbula admirabilis2
Plains Yellow-winged GrasshopperArphia simplex2
Short-winged GrasshopperDichromorpha viridis2
Showy GrasshopperHesperotettix speciosus2
Ash-brown GrasshopperTrachyrhachys kiowa1
Blue-legged GrasshopperMelanoplus flavidus1
Club-horned GrasshopperAeropedellus clavatus1
Gladston's Spur-throat GrasshopperMelanoplus gladstoni1
Green-streak GrasshopperHesperotettix viridis1
Grizzly Spur-throat GrasshopperMelanoplus punctulatus1
Mermiria GrasshopperMermiria bivittata1
Obscure GrasshopperOpeia obscura1
Scudder's Short-winged GrasshopperMelanoplus scudderi1
Speckled Rangeland GrasshopperArphia conspersa1
Spotted-winged GrasshopperOrphulella pelidna1
Stone's LocustMelanoplus stonei1

Leafhoppers and true bugsScore
A LeafhopperParaphlepsius maculosus3
A LeafhopperPrairiana angustens3
Yellow Loosestrife LeafhopperErythroneura carbonata3
A LeafhopperCuerna sayi2
A LeafhopperPrairiana kansana2
An Issid PlanthopperBruchomorpha extensa2
Prairie LeafhopperPolyamia dilata2
A LeafhopperMemnonia panzeri1
A LeafhopperDriotura robusta1
A LeafhopperKansendria kansiensis1
A LeafhopperLaevicephalus vannus1
A LeafhopperAttenuipyga vanduzeei1
A LeafhopperParaphlepsius altus1
A LeafhopperPrairiana cinerea1
An Issid PlanthopperFitchiella robertsonii1
Piglet BugAphelonema simplex1
Red-tailed Prairie LeafhopperAflexia rubranura1

Big Brown BatEptesicus fuscus3
Franklin's Ground SquirrelPoliocitellus franklinii3
Tricolored BatPerimyotis subflavus3
Little Brown BatMyotis lucifugus2
Woodland VoleMicrotus pinetorum2
Northern Long-eared BatMyotis septentrionalis1
Prairie Deer MousePeromyscus maniculatus bairdii1
Prairie VoleMicrotus ochrogaster1
Silver-haired BatLasionycteris noctivagans1

Blanding's TurtleEmydoidea blandingii3
GophersnakePituophis catenifer3
Ornate Box TurtleTerrapene ornata3
Prairie Ring-necked SnakeDiadophis punctatus arnyi3
Prairie SkinkPlestiodon septentrionalis3
Six-lined RacerunnerAspidoscelis sexlineata3
Timber RattlesnakeCrotalus horridus3
Gray RatsnakePantherophis spiloides2
North American RacerColuber constrictor2
Slender Glass LizardOphisaurus attenuatus2
Wood TurtleGlyptemys insculpta2
Butler's GartersnakeThamnophis butleri1
Lined SnakeTropidoclonion lineatum1
Plains GartersnakeThamnophis radix1
Western RibbonsnakeThamnophis proximus1

Please see Section 2. Approach and Methods of the Wildlife Action Plan to learn how this information was developed.

Rare plants

The Natural Heritage Inventory has developed scores indicating the degree to which each of Wisconsin's rare plant species is associated with a particular natural community or ecological landscape. This information is similar to that found in the Wildlife Action Plan for animals. As this is a work in progress, we welcome your suggestions and feedback.

Scores: 3 = "significantly associated," 2 = "moderately associated," and 1 = "minimally associated."
Scientific Name Common Name Score
Agalinis gattingeri Roundstem Foxglove 2
Agalinis skinneriana Pale False Foxglove 2
Anticlea elegans ssp. glaucus White Camas 2
Asclepias hirtella Green Milkweed 1
Asclepias ovalifolia Dwarf Milkweed 2
Asclepias purpurascens Purple Milkweed 3
Besseya bullii Kitten Tails 3
Camassia scilloides Wild Hyacinth 1
Carex swanii Swan Sedge 3
Carex torreyi Torrey's Sedge 3
Cuscuta coryli Hazel Dodder 1
Dasistoma macrophylla Mullein Foxglove 3
Desmodium canescens Hoary Tick-trefoil 3
Houstonia caerulea Azure Bluets 2
Lechea mucronata Hairy Pinweed 3
Lespedeza violacea Violet Bush Clover 2
Lespedeza virginica Slender Bush Clover 2
Penstemon hirsutus Hairy Beardtongue 2
Phemeranthus rugospermus Prairie Fame-flower 1
Phlox bifida ssp. bifida Cleft Phlox 2
Piptatheropsis canadensis Canada Mountain Ricegrass 1
Polytaenia nuttallii Prairie Parsley 2
Prenanthes crepidinea Nodding Rattlesnake-root 2
Quercus muehlenbergii Chinquapin Oak 3
Rhamnus lanceolata var. glabrata Lanced-leaved Buckthorn 2
Rhus aromatica Fragrant Sumac 2
Senna marilandica Maryland Senna 2
Spiranthes ovalis var. erostellata October Lady's-tresses 3
Teloschistes chrysophthalmus Gold-eye Lichen 2
Thaspium chapmanii Hairy Meadow Parsnip 2
Thaspium trifoliatum var. flavum Purple Meadow Parsnip 3


The following Ecological Landscapes have the best opportunities to manage for Oak Opening, based on the Ecological Landscapes of Wisconsin Handbook.

Map of the Ecological Landscapes of Wisconsin.

Major (3 on map)
A major opportunity for sustaining the natural community in the Ecological Landscape exists, either because many significant occurrences of the natural community have been recorded in the landscape or major restoration activities are likely to be successful maintaining the community's composition, structure, and ecological function over a longer period of time.

Important (2 on map)
Although the natural community does not occur extensively or commonly in the Ecological Landscape, one to several occurrences do occur and are important in sustaining the community in the state. In some cases, important opportunities may exist because the natural community may be restricted to just one or a few Ecological Landscapes within the state and there may be a lack of opportunities elsewhere.

Present (1 on map)
The natural community occurs in the Ecological Landscape, but better management opportunities appear to exist in other parts of the state.


Wisconsin Wildlife Action Plan graphic

What are conservation actions?

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for natural communities


The following are additional considerations for Oak Opening in Ecological Landscapes with opportunities for protection, restoration, and/or management. For more information, see the Wildlife Action Plan.

Southeast Glacial Plains

The Southern Unit of the Kettle Moraine State Forest offers some of the best management and restoration opportunities in the upper Midwest, including Eagle Oak Opening (Waukesha County). Other good examples occur at Lulu Lake State Natural Area (Walworth County).

Southern Lake Michigan Coastal

Several Milwaukee County Parks and a few other public lands (e.g., Chiwaukee Prairie State Natural Area in Kenosha County) have small-scale opportunities to manage for this community type.

Southwest Savanna

More refined boundary information is needed. There are pastured savannas here that have never been plowed that have characteristic structural features, and may have retained at least some important understory components.

Western Coulee and Ridges

There are many overgrown sites and restoration opportunities are excellent in this Ecological Landscape. Some examples of this type are found at Avoca Prairie-Savanna (Iowa County), Red Cedar River Savanna State Natural Area and Caryville Savanna (Dunn County), and Lower Chippewa River State Natural Area (Buffalo, Dunn, Trempealeau Counties). Inventory projects that are designed to reveal priority restoration sites would likely yield positive results in this EL.

Western Prairie

Some of the Waterfowl Production Areas and Wildlife Areas in this Ecological Landscape (e.g., Oak Ridge Lake Waterfowl Production Area in St. Croix County) offer restoration potential for this community type.


Oak Opening Photos

Oak Opening Photo

Open-grown bur oaks dominate this remnant oak opening. Grazing has maintained savanna structure but the understory is now dominated almost entirely by non-native plants.

Photo by Eric Epstein.

Oak Opening Photo

Oak Opening with native prairie understory, Monroe County.

Photo by Eric Epstein.

Oak Opening Photo

Oak Opening and diverse tallgrass prairie remnant. Southern Kettle Moraine region, western Waukesha County.

Photo by Eric Epstein.

Oak Opening Photo

Long history of fire supression and heavy grazing caused understory of this oak opening to be choked with shrubs, saplings. Historic regime of periodic wildfire would favor an open understory.

Photo by Eric Epstein.

Oak Opening Photo

Oak opening with groundcover of shooting-star (Dodecatheon meadia) at Lulu Lake State Natural Area.

Photo by Ryan O'Connor.

Note: photos are provided to illustrate various examples of natural community types. A single photograph cannot represent the range of variability inherent in a given community type. Some of these photos explicitly illustrate unusual and distinctive community variants. The community photo galleries are a work in progress that we will expand and improve in the future.

Last revised: Tuesday, August 30, 2022