Central Hardwood

habitat photo
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Central hardwoods at Devils Lake State Park, Sauk County. Photo by John Gritt.

Habitat Description

Habitat Crosswalk


The Central Hardwood cover type occurs in Wisconsin south of the Tension Zone (see Curtis 1959).  This cover type is comprised of variable associations of hardwood tree species, typically oaks with common dominants and codominants including shagbark and bitternut hickories, American and slippery elms, black cherry, red and sugar maples, white ash, basswood, hackberry, aspens, white birch, black walnut, and butternut.  Ironwood is often common in the understory and lower canopy.  Other associated species include honey locust, black locust, box elder, white birch, white pine, and beech (WDNR 2010a, Mossman 2011).

Central hardwoods share many characteristics of species composition and structure with several other cover types.  Stands are typed as central hardwood when they do not meet the criteria for these other cover types, particularly Oak (≥50% of the basal area is oak) or Northern Hardwood (≥50% of the basal area is any combination of sugar maple, beech, basswood, white ash, or yellow birch), but also Red Maple and Black Walnut.  As with these cover types, central hardwoods can occur on a variety of sites, ranging from mesic to dry, and stand structure and species composition of canopy, subcanopy, shrub, and herbaceous layers can vary similarly according to site conditions and land use history.  Readers should refer to descriptions of these other cover types, particularly the Oak (Steele 2012) and ‘Southern’ Northern Hardwood (Steele in prep) Habitat Pages, for lists of common understory species.

In general, oaks are the most common overstory dominants in central hardwood stands, although many of these stands are transitioning towards sugar maple, with basswood, white ash, and ironwood increasing in importance as oaks fail to regenerate.  These northern hardwood species are most prominent on dry-mesic and mesic sites.  On sites where northern hardwood seed sources have not become established, central hardwood stands increasingly are dominated by red maple, black cherry, elms, shagbark hickory, bitternut hickory, and ironwood.  Additional detail on the compositional variation of the central hardwood type across the different Ecological Landscapes of southern Wisconsin may be found in the Central Hardwood chapter of the Silviculture and Forest Aesthetics Handbook (WDNR 2010a).

Historical and Present-day Context and Distribution

There is no historical estimate for central hardwood as such, as this cover type is comprised of variable associations of tree species that overlap significantly with other cover types, particularly oak and northern hardwood.  Neither Curtis (1959) nor the Wisconsin Natural Heritage Inventory recognize the central hardwood cover type as a native forest community.  It’s likely that this cover type as currently defined was very limited in extent historically, as it now occurs predominantly in areas formerly dominated by oak forests, woodlands, and savannas (WDNR 2010a).  With Euro-American settlement these areas were subjected to widespread clearing for agriculture, and the trees used as building materials and fuels.  The cutting and burning used to clear the land, subsequent farming and pasturing, and then abandonment of land that was marginal for cultivation created conditions favoring oaks over more shade-tolerant, less fire-adapted species.  Fire suppression, high white-tailed deer herbivory, competition from native and non-native species, and unsustainable logging in the oak forests that regenerated from those conditions have created the situation observed today, where the oak component is steadily being lost from southern Wisconsin forests (WDNR 2011 a, b).  This loss is accelerating as mature oaks, originating from cutting, burning and post-savanna succession 100-150 years ago, are being lost to logging and senescence.  As a result, the composition of these forests is shifting to more shade-tolerant species such as red and sugar maples, basswood, hickories, hackberry, elms, green and white ashes, black cherry, and ironwood, which are characteristic of later-successional central hardwoods.  In locations where sugar maple seed sources exist, central hardwoods are succeeding to northern hardwoods, a trend that is expected to continue (WDNR 2010a).

Central hardwoods are common in every Ecological Landscape in southern Wisconsin save the Central Sand Plains, which does not contain a significant component of this cover type.  Current acreage of central hardwoods in southern Wisconsin is estimated at 691,404 (excluding the Central Sand Plains) (WDNR 2010a).

Natural Disturbances and Threats

The oak forests, woodlands, and savannas that once existed in the areas now occupied by central hardwoods were largely maintained by fire, both naturally occurring fires and especially those set by Native Americans.  Periodic fires played an important role in the development and maintenance of oak cover types, with variations in site characteristics and fire intensity and frequency determining structural conditions and species composition.  Other disturbances included wind-throw and the actions of burrowing and grazing animals (WDNR 2011b; Staffen 2010).

Threats to the oak component of central hardwoods are very similar to those for oak-dominated forests.  These are described in detail in the Oak Habitat Page (Steele 2012).  Briefly, they include loss of oaks and lack of oak regeneration due to high-grading, fire suppression, excessive herbivory, competition with native and non-native plant species, detrimental effects of gypsy moth (an exotic insect pest), forest fragmentation, changing land-use and land-ownership patterns, and climate change.

High-grading (selective removal of the largest, highest-quality, most commercially valuable trees, often oaks) is an unsustainable logging practice that has resulted in many genetically or structurally impoverished central hardwood stands characterized by poor-quality trees and dense understory shrubs.  The loss of oaks from central hardwoods due to this and other threats is of concern, as many structural characteristics of oaks are not duplicated in central hardwood stands.  Central hardwood leaf litter is less flammable than oak litter and carries fire poorly, decreasing the chance that fire can be reintroduced and increasing the probability of changes in soil and microbial properties due to loss of fire disturbance.  It is anticipated that the increase in central hardwoods will result in negative consequences for wildlife and ecosystem processes associated with oak forests.  While specific effects are difficult to predict, as central hardwoods were not common historically, there is no known wildlife species that prefers central hardwoods to oak (WDNR 2010a).

As with other forest types in southern Wisconsin, central hardwoods have been affected by fragmentation.  Large parts of southern Wisconsin are characterized by “permanent” fragmentation, or the long-term conversion of native habitats to agricultural, residential, or urban uses.  Rural housing development is an increasing threat to forests, particularly in the Driftless Area which has experienced considerable housing growth in the past several decades (Radeloff et al. 2005).  This rural sprawl reduces the amount of interior forest, degrades and fragments restorable tracts, and limits management options.  Many central hardwood stands are in small, isolated patches or linear configurations with little forest interior and large amounts of edge (WDNR 2010a).

Exotic invasive plants are an ongoing threat to forest composition and structure.  When abundant, they can outcompete and exclude native herbs and shrubs, impede tree regeneration, and affect successional patterns and future forest conditions over large areas.  Among the most aggressive and problematic invaders in central hardwood stands are garlic mustard, common and glossy buckthorns, bush honeysuckles, Japanese barberry, and multiflora rose (WDNR 2010a).

In addition, the ash component of the central hardwood type is threatened by the emerald ash borer, an introduced insect pest.

Wisconsin foresters and land managers typically have considered central hardwoods inferior to the oak type in terms of timber, wildlife habitat, and native plant-animal communities, and generally have worked to stave the ongoing type conversion.  Yet, the central hardwood type is fast becoming dominant in southern Wisconsin despite ongoing efforts to the contrary, and there is an urgent need to determine how it should be managed sustainably where the oak type cannot be reasonably maintained, and to better understand its benefits to birds.  For this we can draw both from management goals farther south where the type is of longstanding importance, and from general management guidelines for forest birds in the Midwest.

As with other forest types, high-quality central hardwoods should be considered at both local and landscape scales.  For forest birds, a high-quality landscape probably will include a mosaic of forest cover types, with oaks being regenerated and maintained on suitable (generally wet-mesic and dry to dry-mesic) sites, northern hardwoods on some mesic sites, and central hardwoods in a variety of sites where oaks cannot reasonably be maintained.  Such a landscape would be largely forested, with large forest tracts, minimal fragmentation, a high degree of connectivity, and a variety of age classes ranging from regenerating stands to many mature stands, with some in old-growth condition.  There should be many large trees (>70 ft. tall where site conditions allow), cavity trees, snags, coarse woody debris, some interior openings filling with desirable shrubs and saplings, and soft edges at boundaries with open habitats.  At the landscape level, there should be a wide variety of site-appropriate tree and understory species, and varied structures at ground, shrub, sapling and canopy layers.  Woody and herbaceous invasives, and deer herbivory should be under control and not limiting healthy, diverse plant community development and desirable tree regeneration.

Related WBCI Habitats: Oak, ‘Southern’ Northern Hardwood, Bottomland Hardwood (wet-mesic sites).

Overall Importance of Habitat for Birds

As with other forest types, the bird community found in a particular tract of central hardwoods depends on various factors including tree species composition, overstory and understory structure, soils, topography, and past management history, as well as landscape characteristics such as tract size, configuration, and surrounding habitats.  Unlike many other forest types, central hardwood lacks its own distinctive bird community, as it is such a variable cover type and overlaps significantly with other cover types, particularly Oak and ‘Southern’ Northern Hardwood, in many compositional and structural features.

Common breeding species found in central hardwoods across the moisture continuum from dry to mesic include Hairy Woodpecker, Downy Woodpecker, Red-bellied Woodpecker, Eastern Wood-Pewee, Blue Jay, Black-capped Chickadee, White-breasted Nuthatch, Blue-gray Gnatcatcher, Red-eyed Vireo, Ovenbird, Scarlet Tanager, and Rose-breasted Grosbeak.  In general, the similarity of the central hardwood bird community to that of oak or northern hardwood forest increases as oaks or sugar maple, respectively, increase in dominance or co-dominance.  Some species that seem to particularly favor oaks, such as Whip-poor-will, Red-headed Woodpecker, Worm-eating Warbler, and Cerulean Warbler, may be absent in central hardwoods.  Conversely, some birds that prefer mesic microsites within oak forests, such as Acadian Flycatcher, can be more common in central hardwoods than in oak (Mossman 2011).

See Steele (2012) and Steele (in prep) for descriptions of the bird communities of oak and northern hardwood forests in southern Wisconsin, and how they can vary according to disturbance and successional stage.

The widespread loss of oaks in central hardwood stands and succession of those stands to northern hardwoods is a matter of concern.  Oaks provide critical habitat for a diversity of birds, including most breeding forest species of conservation concern in southern Wisconsin.  The significance of oaks to birds is not entirely understood, although some aspects (e.g., importance of oak acorns as a food source) are well-studied and well known.  Recent research has illuminated others, such as the diversity of oak-associated insects, especially Lepidopterans (Tallamy and Shropshire 1999), that support high densities of breeding and migrating birds (Wood 2011).  Certainly the association of many bird species, particularly Priority birds like Red-headed Woodpecker, Worm-eating Warbler, and Cerulean Warbler, with structural or ecological attributes of oaks has been noted by many researchers (e.g., Mossman and Lange 1982, Hamel 2006, Newell and Rodewald 2011, M.J. Mossman pers. comm. 2011), although some aspects of these associations are not well understood.  As many of these features are not duplicated by other tree species when oaks are lost from central hardwood stands, it is reasonable to predict that this loss will result in negative consequences for southern Wisconsin forest birds.

WBCI Priority Bird Species.  Species in boldface are currently proposed as Focal species for southern Wisconsin forests (Mossman 2011).

Species name Status Habitat and/or Special Habitat Features
Ruffed Grouse bw Now uncommon to rare, gone from many former areas; where patches of both early-successional and older forest occur.
Red-shouldered Hawk bmw In extensive tracts of (or adjacent to) floodplain forest; nests in large trees.
Broad-winged Hawk bm In extensive tracts.
American Woodcock bm In early-successional tracts, large openings; may feed in forest.
Black-billed Cuckoo bM Shrubby woods and edge.
Yellow-billed Cuckoo BM Fairly common; prefers large tracts, canopy.
Whip-poor-will bm Disappearing; prefers inclusions of dry oak forest or woodland with open understory, near openings; often in bedrock glades or oak barrens succeeded to forest, sometimes within central hardwood matrix.
Chimney Swift bmf Nests in chimneys, occasionally in large “chimney” snags within any forest type.
Red-headed Woodpecker bmwf Where barkless snags occur due to windthrow, fire, or disease; also in open-canopy patches; more common among oaks.
Yellow-bellied Sapsucker bmw Especially near floodplain forest, in Driftless Area coulees, and where white birch or aspen are present.
Northern Flicker BMw Scattered, where snags, open or semi-open canopy, open herbaceous understory; prefers drier sites.
Acadian Flycatcher bm Occasional along streams, at bases of steep slopes or in well-shaded mesic microsites in interior of extensive forest.
Least Flycatcher BM Fairly common but irregular in both interior and edge, including pole-sized stands; often in colony-like breeding groups.
Warbling Vireo bm Edges, especially wet-mesic sites.
Yellow-throated Vireo BM Common and widespread in mature forest tracts >40 acres.
Veery BM Extensive dry-mesic forest where there are dense shrubs or rank, tall, diverse forest herb layer, especially damp or mesic microsites.
Wood Thrush BM In tracts >40 acres, where closed or semi-open canopy, especially with patches of tall semi-dense saplings.
Brown Thrasher bm Rarely, in open or recently logged woods adjacent to more open habitats; edges.
Blue-winged Warbler BM Dry-mesic to mesic, shrubby forest openings, edges.
Golden-winged Warbler bm Rare; in same sites as Blue-winged Warbler.
Chestnut-sided Warbler bM Rare breeder in shrubby openings and edges of extensive forest; more common northward.
Black-throated Green Warbler bM Rare breeder in large, mature, dry-mesic to mesic tracts that include sugar maple or sometimes conifers (white pine, hemlock).
Cerulean Warbler BM Mature forest with tall (>75 ft. high), diverse canopy species and structure; prefers oaks; extensive tracts.
Worm-eating Warbler bm Mostly in mature oak forest with semi-open canopy on south and west-facing slopes, draws; sometimes in similar microsites within central hardwoods; large tracts.
Louisiana Waterthrush bm Along clear, rocky streams or springs within extensive forest.
Kentucky Warbler bm Uncommon in dry-mesic to mesic forest tracts >240 acres; often in dense or semi-dense damp, shrubby openings of natural or logging origin, and floodplain-upland boundary.
Mourning Warbler bm Similar to Kentucky Warbler, but more common, less restricted to very large tracts, extends into larger open-canopy patches.
Hooded Warbler BM Interior openings with dense shrubs and brambles; large tracts; prefers mesic or dry-mesic sites; uses pine plantations with shrubby understories in the Kettle Moraine.
Rose-breasted Grosbeak BM Common and widespread in forest interior or edge; prefers open or semi-open canopy with moderate sapling/shrub growth.

In addition, some Priority species, such as Common Yellowthroat and Field Sparrow can occur for a few years after heavy logging.


The deciduous forest habitat objectives assigned to southern Wisconsin by the Upper Mississippi River and Great Lakes Joint Venture Implementation Plan (UMRGLJV 2007) are problematic.  They were generated using population estimates for “focal planning species” (Cerulean Warbler, Louisiana Waterthrush, and Kentucky Warbler) that are extremely low because they are based on data from the federal BBS, a survey that does not adequately sample these rare species or their habitats in Wisconsin.  The WBCI Southern Forests Committee recommends generating better population estimates for these species, from which a more realistic habitat objective may be determined.  In addition, the Southern Forests Committee likely will not set a numeric objective for central hardwoods per se, but will integrate maintenance and enhancement recommendations for this cover type into specific identified Forest Conservation Areas as part of an overall strategic implementation plan for the southern forests.

Management Recommendations

Central hardwoods were uncommon in Wisconsin until recently.  This cover type is increasing in abundance, replacing oak-dominated forests as oaks fail to regenerate.  Central hardwood stands are losing their oak component for the same reason.  Central hardwood is becoming the “matrix” forest type in many parts of southern Wisconsin, in which Oak, ‘Southern’ Northern Hardwood, and other types are embedded.  Given the importance of oak to southern forest Priority birds, the principal recommendations for central hardwoods are to: favor management that will convert central hardwoods to oak wherever possible; increase or maintain the oak component in central hardwoods stands where conversion back to the oak type is not possible; or, where neither of these is feasible, retain mature oaks as long as possible and manage central hardwood stands for structural and compositional diversity to improve the “matrix” forest.  See the WBCI Oak Habitat Page (Steele 2012) for detailed oak management recommendations.

Landscape-level Recommendations

  1. Plan forest management on a landscape scale to determine the most appropriate sites for management favoring oaks and management focused on maintaining and enhancing central hardwoods (with little or no oak component).  Refer to the Oak Habitat Page (Steele 2012) for detailed oak management recommendations.
  2. Protect and connect existing forest tracts.  Modeling has shown that the percentage of forest cover is an important landscape-level habitat suitability feature for many priority forest birds (Thogmartin and Knutson 2007; Thogmartin et al. 2004).
  3. Older forest is currently lacking, and provides important habitat for various priority birds (WDNR 2005).  Retain some patches across the landscape where managed old-growth is the goal or where harvest is excluded and the forest is allowed to mature naturally (Bakermans and Rodewald 2009).
  4. Educate private landowners on the conservation importance of oak and central hardwoods (Knoot et al. 2010).
  5. Encourage cross-boundary cooperation among landowners in order to more effectively and efficiently manage oak and central hardwoods (Knoot et al. 2010).

Site-level Recommendations

  1. Articulate clear site-level management objectives that have been developed within a landscape context (see Recommendation #1, above).
  2. Wherever feasible, convert central hardwoods to oak or maintain/increase the oak component in central hardwood stands.  Refer to the Oak Habitat Page (Steele 2012) for detailed oak management recommendations.
  3. In stands containing mature oaks where management to regenerate oak is not feasible, consider deferring management, or apply extended rotation or old-growth management to retain oaks as long as possible (WDNR 2010a, b).
  4. Where oak management is not feasible, manage central hardwoods for compositional and structural diversity by:
    • Applying extended rotation or managed old-growth management to some stands.
    • Retaining some large-diameter trees as well as living and dead cavity trees, snags, and coarse woody debris.
    • Maintaining or increasing tree species diversity.
    • Creating and maintaining a diversity of size- and age-classes (WDNR 2010a, b).
  5. Reduce deer densities whenever feasible, especially where implementing management to maintain or favor oaks.  Excessive deer herbivory may be the limiting factor for oak regeneration in many areas, and must be addressed in order for regeneration to succeed.  No regeneration technique is likely to work if deer browse is too high (WDNR 2011b).
  6. Control invasive species, especially garlic mustard, buckthorn, and honeysuckle, and eliminate where possible; employ management practices that limit the spread of invasives.  Refer to WDNR Forestry Best Management Practices (BMPs) for invasive species (WDNR 2009).
  7. Limit or exclude livestock grazing within forests.  Heavy grazing can alter understory plant composition, damage trees, hinder regeneration, and cause soil compaction.  Cattle also lead to increased nest parasitism by attracting Brown-headed Cowbirds (Knutson et al. 2001).

Ecological Opportunities

Ecological Landscape Opportunity Management Recommendations
Central Sand Hills Major All
Southeast Glacial Plains Major All
Western Coulee and Ridges Major All
Central Lake Michigan Coastal Important All
Southern Lake Michigan Coastal Important All
Southwest Savanna Important All
Western Prairie Important All
Central Sand Plains Present All

Research Needs


Key Sites

Key Partners

Funding Sources

Information Sources


Contact Information

Steele, Y.  2013.  Central Hardwood Habitat Page.  In Paulios, A. and K. Kreitinger (eds.).  2007-2013.  The Wisconsin All-Bird Conservation Plan, Version 2.0.  Wisconsin Bird Conservation Initiative.  Wisconsin Department of Natural Resources, Madison, WI.

Kreitinger, K., Y. Steele and A. Paulios, editors. 2013.
The Wisconsin All-bird Conservation Plan, Version 2.0. Wisconsin Bird Conservation Initiative.
Wisconsin Department of Natural Resources. Madison, WI.

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