Oak Woodlands

Unit Designation Size
5 LIP Oak Woodland Remnant 40.0 acres
8 East Ridge Oak Woodland Remnant 32.5 acres
25 North Oak Woodland Remnant 63.0 acres

Total Area:  135.5 acres

2014 Spring oak woodland burn

As canopy closure increases, oak savanna grades into open oak woodland. Open oak woodland is generally defined as a fire‐dependent tree stand dominated by white oak (Q. alba) with closed canopy structure of 80 – 100%. Periodic wildfire is required for oak regeneration and to prevent succession to mesic forest dominated by maples (Acer spp.) and other fire‐intolerant hardwoods, and Cottam (1949) postulated that periodic drought may also play a role in maintaining oak‐dominated plant communities. The understory species composition of open oak woodland consists of the most shade‐tolerant savanna species and the most fire‐tolerant mesic forest species. Shrubs, such as hazelnut (Corylus americana) and grey dogwood (Cornus racemosa) were dominant understory species in many stands studied by Curtis (1959), who concluded that these species helped stabilize the community by shading out box elder (Acer negundo), slippery elm (Ulmus rubra), and other mesic forest species that would otherwise become established within canopy gaps. Prior to settlement, open oak woodland covered 1.4 million acres of Wisconsin (Henderson 1995). By the time of the Plant Ecology Laboratory (PEL) studies in the mid‐1900s, open oak woodlands in Wisconsin had been so degraded (by timber and firewood harvests, overgrazing, and lack of wildfire with concomitant encroachment by fire‐ intolerant shrub and tree species) that few stands still remained in a undisturbed condition for study. Curtis (1959) considered open oak woodland as a type of southern xeric forest, and only quantified a single stand in Dane County.

Several understory species considered modal to open oak woodlands (southern xeric forests) by Curtis (1959) can be found in abundance in the open oak woodland remnants at the Preserve, including wild geranium (Geranium maculatum), spikenard (Aralia racemosa), Pennsylvania sedge (Carex pennsylvanica), pointed‐leaf tick trefoil (Desmodium glutinosum), woodland anemone (Anenome virginiana), white avens (Geum canadense), elm‐leaved goldenrod (Solidago ulmifolia), bellwort (Uvularia grandiflora), early meadow rue (Thalictrum dioicum), and bottlebrush grass (Elymus hystrix).  Additional understory species that are common in the Preserve’s open oak woodland remnants include rattlesnake plantain (Goodyera pubescens), poke milkweed (Asclepias exaltata), rue anemone (Thalictrum thalictroides), early buttercup (Ranunculus fascicularis), and hooked buttercup (R. recurvatus).

Tree stand composition of the oak woodland remnants grades from oak‐dominated or oak‐hickory associations on the ridge tops and south‐ and west‐facing slopes of the ridges (southern xeric forest consisting of bur, white, red, and black oak, shagbark and yellow bud hickory, and hackberry), to mixed‐oak forest stands covering  much of the east‐facing slopes (southern dry‐mesic forest consisting of red and sugar maple (Acer spp.), basswood (Tilia americana), cherry (Prunus serotina), white ash (Fraxinus americana) and butternut (Juglans cinerea, Special Concern)  in addition to white and black oak). The open oak woodlands at the Preserve are presently in a highly restorable condition, and much of the restoration objectives for these communities can be accomplished with prescribed fire regimes alone.

Bottlebrush grass (Elymus hystrix), Photo by Paul Drobot, UW Steven’s Point Herbarium

Summary of Ecological Management Goals for Oak Savanna and Open Oak Woodland Communities

  • Restore remnant oak savanna and open oak woodland communities to their presettlement condition.
  • Reintroduce periodic wildfire regimes to oak savanna and open oak woodland.
  • Reduce or eliminate populations of high‐impact invasive species.
  • Catalog species richness across all trophic levels and enhance habitat quality to maximize species richness and diversity.
  • Establish and maintain habitat structural elements to benefit wildlife.