Ozark-Ouachita Moist Hardwood Forest

This system is found on lower slopes, toeslopes and valley bottoms within the Ozark and Ouachita regions, as well as on north slopes. In the Ozarks, Quercus rubra increases in abundance compared to dry-mesic habitats, and Acer saccharum is sometimes a leading dominant. On more alkaline moist soils, Quercus muehlenbergii, Tilia americana, and Cercis canadensis may be common. In the Boston Mountains, mesic forests may also be common on protected slopes and terraces next to streams. Here, Fagus grandifolia may be the leading dominant, with codominants of Acer saccharum, Liquidambar styraciflua, Tilia americana, Magnolia acuminata, Magnolia tripetala, and others. Similar habitats occur in the western Ouachita Mountains.

Dominant or characteristic trees in examples of this system may include Quercus alba, Quercus rubra, Acer floridanum (= Acer barbatum), Acer saccharum, Fagus grandifolia, Liquidambar styraciflua, Quercus muehlenbergii, and Tilia americana. The understory may contain Cercis canadensis, Magnolia tripetala, and/or Magnolia acuminata. Some common shrubs include Asimina triloba and Lindera benzoin. Stands will typically have diverse ground layers. Some typical herbs include Podophyllum peltatum and Hybanthus concolor.

This system may be found on a wide range of topographic positions. It includes mixed mesophytic forests, seeps/springs and smaller riparian areas. This system is found on primarily north- and east-facing aspects, lower slopes, toeslopes, small valley bottoms and terraces, as well as other protected slopes and ravines along intermittent and/or ephemeral streams. Distribution is influenced by local conditions affecting moisture, aspect, elevation and soil productivity. Closed conditions are multiple canopy usually late-seral forests. Stands of this system are generally small, isolated, and/or disjunct and are generally "embedded" in a larger landscape matrix. These communities are maintained primarily through naturally occurring circumstances such as aspect, elevation, soil moisture conditions, and soil productivity, except for mortality or other disturbance-induced openings or gaps.

This type has a lower fire frequency than drier (uphill) types and experiences primarily low-intensity surface fire with occasional mosaic (mixed-severity) or replacement fire. Mean fire-return interval (MFI) is about 25 years with wide year-to-year and within-type variation related to moisture cycles, degree of sheltering and proximity to more fire-prone types. Anthropogenic fire is considered and contributes to within-type MFRI variation. Drought and moisture cycles play a strong role interacting with fire and insect and disease damage. Other natural disturbances may include wind and ice (Landfire 2007a).

The most critical anthropogenic threat range-wide is invasive exotic species including Microstegium vimineum and Ailanthus altissima, which can become dominant in the ground and shrub layers following canopy disturbance. In more developed regions, Euonymus alatus, Euonymus fortunei, Ligustrum sinense, Lonicera japonica, and Lonicera maackii are taking over the understory at the landscape scale. For mesic hardwood forests containing Fraxinus species, emerald ash borer (which as of October 2013 has been reported from southeastern Missouri) may also be (or become) a significant stressor. Feral hogs also represent one of the greatest threats to biodiversity in these forests (Engeman et al. 2007). They can be especially difficult to control in sensitive slope forests. Conversion of this type has also resulted from repeated canopy removal through logging, which is a threat on private lands, but less so on public land, particularly in Arkansas, where many examples are known from national forests. Sites for this type were historically less frequently logged than the adjacent uplands, with more desirable species being removed in preference to Fagus grandifolia, which is less desirable in the lumber trade. In addition, some mesic hardwood forests in more moderately dissected terrain have been converted to pine plantations or impacted (destroyed or fragmented) by agriculture. Bluff habitats are often prime sites for development, especially along major rivers. The threat of development is exacerbated by the current surge in population in northwestern and north-central Arkansas. Urban and exurban sprawl into previously forested lands outside the major communities is expected to continue to increase (Arkansas Forestry Commission 2010). This will lead to the conversion of sites to human-created land uses.

The most significant potential climate change effects over the next 50 years include an increase in storms, which would contribute to erosion of the substrate and loss of canopy. Climate change may also bring increased periods of drought, which will affect the health and survival of the moisture-requiring trees, as well as increase the probability of damaging wildfire.

This system is found within the Ozarks and Ouachita Mountains of Missouri, Arkansas, and Oklahoma.