Midwestern Beech-Maple Forest

This system is found primarily along the southern Great Lakes ranging from central Indiana to southern Ontario. It is typically found on flat to rolling uplands to steep slopes with rich loam soils over glacial till. This system is characterized by a dense tree canopy that forms a thick layer of humus and leaf litter leading to a dense and rich herbaceous layer. Acer saccharum and Fagus grandifolia comprise up to 80% of the canopy. Canopy associates can include Quercus rubra, Tilia americana, and Liriodendron tulipifera with Carpinus caroliniana and Ostrya virginiana common in the understory and subcanopy. The relative dominance of sugar maple compared to other tree species varies across the range of this system based on regional climate and microclimate. The herbaceous layer is very diverse and typically includes spring ephemerals. Some common species include Arisaema triphyllum, Osmorhiza claytonii, Polygonatum biflorum, and Trillium grandiflorum. The primary natural disturbance influencing this system includes wind-driven gap dynamics. Conversion to agriculture has significantly decreased the range of this system, and very few large stands remain intact.

This system is typically found on flat to rolling uplands to steep slopes with rich loam soils over glacial till. It occurs principally on medium- or fine-textured ground moraine, medium- or fine-textured end moraine, and silty/clayey glacial lakeplains. Sand dunes and sandy lakeplains can support these systems where proximity to the Great Lakes modifies local climate (within 10-20 miles of the shore, evapotranspiration conditions are suitable for mesic forest). Prevalent topographic positions of this community are gentle to moderate slopes and level areas with moderate to good drainage. Where mesic southern forest occurs on steeper slopes, it is often associated with northern to eastern exposures which receive low amounts of direct sunlight and are characterized by a cool, moist microclimate.

It can occur on a variety of soil types, but loam is the predominant texture. The diversity of soils which can support this system include sand, sandy loam, loamy sand, loam, silt loam, silty clay loam, clay loam, and clay. Soils are typically well-drained with high water-holding capacity and high nutrient and soil organism content. High soil fertility is maintained by nutrient inputs from the decomposition of deciduous leaves which enrich the top layer of soil (Cohen 2004).

Small-gap development and replacement due to tree death is the prevalent disturbance factor influencing this system. Catastrophic fire and/or wind can impact this system over long return intervals but are rare. Tree canopy tends to be closed so understory plants receive little light after leaf-out in the spring. This system could form large stands or be part of a large forested landscape in conjunction with other forested types, resulting in a relatively high proportion of forest interior to forest edge.

The greatest impacts on this system are due to conversion of the surrounding landscape to agriculture, logging, and grazing. This system occurs on relatively fertile soils and many areas have been converted to or affected by agricultural uses. Other sites have been subject to selective or clearcut logging. Outright conversion to crops or clearcut logging destroys the affected area and has greatly reduced the range of this system. Remaining stands are also impacted by these activities on the surrounding landscape. Agricultural and urban development, road construction, and logging create gaps in formerly large blocks of forest. These serve as vectors or preferred habitat for invasive and aggressive native species, some of which thrive in the forest edge habitat but do not favor the interior of large forested stands (e.g., brown-headed cowbird (Molothrus ater)) (Howell et al. 2005). The structure and composition of stands near the edge is different from the interior (Palik and Murphy 1990). White-tailed deer (Odocoileus virginianus) populations have increased significantly due to their preference for fragmented landscapes and elimination of top carnivores. Browse pressure at these high population levels can have significant effects on forest composition and structure (Rooney and Waller 2003).

Many of the remaining stands are farm woodlots that have been subject to continual anthropogenic pressures. The structure and composition of the remnants have been altered by selective logging, grazing, removal of snags and logs for firewood, deer herbivory, exotic species invasion, and human-introduced diseases (e.g., Dutch elm disease and chestnut blight) (Cain 1935, Curtis 1959, Brewer 1980, Parker et al. 1985, Donnelly and Murphy 1987, Robertson and Robertson 1995). Many fragments are dominated solely by Acer saccharum, which was often left to provide maple syrup and is favored in gaps created by selective logging. In addition, Fagus grandifolia was often culled because of its poor timber value. Conversely, many stands that were high-graded of valuable timber (i.e., sugar maple and red oak) are now beech-dominated (Cohen 2004).

Invasive species often spread after fragmentation and repeated disturbance (i.e., logging). Invasive plant species that threaten the diversity and structure of this system include Acer platanoides, Alliaria petiolata, Berberis thunbergii, Celastrus orbiculata, Elaeagnus umbellata, Frangula alnus (= Rhamnus frangula), Hesperis matronalis, Ligustrum vulgare, Lonicera japonica, Lonicera maackii, Lonicera morrowii, Lonicera sempervirens, Lonicera tatarica, Lonicera x bella, Lonicera xylosteum, Rhamnus cathartica, Rosa multiflora, and Viburnum opulus (Kost el al. 2007).

Beech bark disease can be a threat to the health of this system. This fungal disease can kill up to 50% of Fagus grandifolia trees in newly infected stands and reduces the vigor of remaining trees (Witter et al. 2005).

This system is located in the southern Great Lakes from central Indiana north into southern Ontario, and east to northwestern Pennsylvania and western New York.