Northern Gulf Coast Loess Plain Oak-Hickory Forest

This is the former matrix hardwood system flanking the loess bluffs of the most northern portions of the Upper East Gulf Coastal Plain of western Tennessee, western Kentucky, possibly southern Illinois, and northern Mississippi. The core distribution of this system is mapped as the Loess Plains (EPA Ecoregion 74b). Extensive forests once covered this broad area of generally flat to rolling uplands. Most have been cleared for agriculture due to the rich, productive soils derived from relatively thick loess deposits. The areal extent of this forested system has been so heavily reduced that the component community types remain undocumented and speculative at best. Typical stands would contain oaks and other hardwoods. Some typical canopy dominants include Quercus falcata, Quercus alba, Carya tomentosa, Quercus stellata, Quercus marilandica, and Quercus velutina. Scattered successional stands would be dominated by Juniperus virginiana var. virginiana. In addition, Liquidambar styraciflua and Liriodendron tulipifera may be present.

Typical stands would contain oaks and other hardwoods. Some typical canopy dominants include Quercus falcata, Quercus alba, Carya tomentosa (= Carya alba), Quercus stellata, Quercus marilandica, and Quercus velutina. Scattered successional stands would be dominated by Juniperus virginiana var. virginiana. In addition, Liquidambar styraciflua and Liriodendron tulipifera may be present.

The habitat for this system is a broad area of generally flat to rolling uplands. Soils included in this system in western Tennessee are rich, productive, and silty, being derived from relatively thick loess deposits. Most of the soils have fragipans and some are poorly drained (Springer and Elder 1980).

Most of the landscape in which this was the matrix system was cleared of forests for settlement and agriculture during the nineteenth and early twentieth century and very few sites remain in primary forest condition. Fire frequency and severity are classified as Fire Regime Group I, with frequent, low-intensity surface fires. The mean fire-return interval (MFRI) is about 15 years with wide year-to-year and within-type variation related to moisture cycles, degree of sheltering, and proximity to more fire-prone vegetation types. Anthropogenic fire may have contributed to presettlement fire frequency (Landfire 2007a). When sites are cleared for settlement or agriculture, Liquidambar styraciflua is a major component of the replacement successional forest, in addition to other wind-blown or bird-dispersed trees such as Acer rubrum, Celtis spp., Fraxinus americana, Juglans nigra, Juniperus virginiana, Liquidambar styraciflua, Liriodendron tulipifera, Prunus serotina, Robinia pseudoacacia, Sassafras albidum, Ulmus americana, and the exotic Ailanthus altissima. In addition, Baccharis halimifolia is a native increaser shrub that will colonize disturbed sites.

Conversion of this type has primarily resulted from repeated canopy removal through logging, which is also the most critical anthropogenic threat. Most sites have long ago been cleared for agriculture due to the rich, productive soils derived from relatively thick loess deposits. The areal extent of this forested system has been so heavily reduced that the component community types remain undocumented and speculative at best.

The most critical anthropogenic threats to any remaining examples include removal of the characteristic dominant hardwoods and a lack of fire. Removal of the characteristic dominant hardwoods (primarily Quercus species and Carya species) through logging may result in a stand dominated by wind-blown or bird-dispersed tree species, including Acer rubrum, Celtis spp., Fraxinus americana, Juglans nigra, Juniperus virginiana, Liquidambar styraciflua, Liriodendron tulipifera, Prunus serotina, Robinia pseudoacacia, Sassafras albidum, Ulmus americana, and the exotic Ailanthus altissima. Sites may also be converted to Pinus species plantations. Lack of fire in the system leads to a closing of the subcanopy, and consequent loss of ground layer diversity. Feral hog (Sus scrofa) activity, combined with invasion of exotic species are also major threats. Another major threat is conversion to human-created land uses, including residential development, quarries, industrial development, and infrastructure development. The most significant potential climate change effects over the next 50 years include periods of drought, which will affect the health and survival of any remaining trees.

This system would have occupied the most northern portions of the Upper East Gulf Coastal Plain of western Tennessee, western Kentucky, possibly southern Illinois, and northern Mississippi. Its core distribution is mapped by EPA (2004) as the Loess Plains (EPA Ecoregion 74b). Today it is reduced to remnant forest patches in a largely agricultural landscape.