Northern Wet Loess Terrace - PROVISIONAL

Description

Exemplary examples of the full range of plant communities and ecological processes that were once commonplace on this ecological site no longer exist. Vestiges of this once vast system are primarily relegated to abandoned woodlots that have undergone numerous impacts since settlement. Still, there appears to be a close correlation between the species reported in earlier state reports (e.g., Loughridge, 1888; Lowe, 1921) and more recent accounts of extant woodlots (Bryant, 1999). One major difference between the historic community and present stands is the absence of fire, which is thought to have been an important disturbance factor (NatureServe, 2009).

Classifying this system with a single plant association name is extremely difficult, if not impossible, due to the variability of species dominance from stand to stand. One characteristic that appears to be similar throughout is the structural profile of a relatively open to moderately open understory, although this may vary due to local gap-scale dynamics. Some areas in West Tennessee are dominated by willow oak (on Adaton soils) while others support a mixed association of species that include post oak, willow oak, white oak, black oak, and hickory (on Routon soils). Some sites in western Kentucky have been observed to support a characteristic post oak flatwood with adjacent stands consisting of a mixture of post oak, black oak, cherrybark oak, hickory, with interspersed stems of overcup oak. Lowe (1921) reported the entrance of loblolly and shortleaf pine within flatwoods systems to the south in Mississippi. Such odd associations and combinations may be due to different inclusions of soil, interspersed micro-highs and depressions, former land use impacts (Bryant, 1999), latitude, or a combination of any or all of these factors.

A single community phase is recognized for representing the range of species occurring on this site. As additional information becomes available, revisions to this site may warrant significant changes. At a minimum, a new site will be developed for areas to the south in Mississippi where loblolly and shortleaf pine are components.

Of concern, portions of this site have incurred tremendous alteration to drainage. Any attempt to reestablish perceived reference conditions of a stand or a local site must first restore the natural hydrology of that location, which may entail removing drainage structures. If not, management may improve stand structure and even composition to a degree, but the site, overall, will remain in an altered state relative to reference conditions. Retaining drainage structures will directly influence the types of vegetation that colonize the site, which may be entirely different than what would occur, naturally.

Submodel

Description

Agriculture production is the dominant land use activity on this site, today, although production is somewhat limited due to seasonal wetness. Many areas in production have some form of drainage structures established due to seasonal saturation of the soil surface.

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Description

This state is representative of sites that have been converted to and maintained in pasture and forage cropland, typically a grass – legume mixture. For pastureland, planning or prescribing the intensity, frequency, timing, and duration of grazing can help maintain desirable forage mixtures at sufficient density and vigor (USDA-NRCS, 2010; Green et al., 2006). Overgrazed pastures can lead to soil compaction and numerous bare spots, which may then become focal points of colonization by undesirable plants or weeds. Soils exhibiting the core concepts of this site have a pronounced period of wetness followed by droughty conditions. Limitations may pertain mainly to periods of extreme wetness.

Planning or prescribing the intensity, frequency, timing, and duration of grazing can help maintain desirable forage mixtures at sufficient density and vigor (USDA-NRCS, 2010; Green et al., 2006). Because of the limitations of this site, grazing may be limited to small intervals within the appropriate season(s). It is strongly advised that consultation with State Grazing Land Specialists and District Conservationists at local NRCS Service Centers be sought when assistance is needed in developing management recommendations or prescribed grazing practices on this site.

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Description

This state represents a broad range of management objectives, options, and stand conditions including woodlots allowed to grow or revert naturally; repeated single-tree harvests (often high-graded); carefully prescribed treatments; and conversion to a monoculture or single-species stand.

Various management or silvicultural methods can lead to very different structural and compositional results. For prescribed management options, methods are diverse, which include even-aged (e.g., clearcut and shelterwood) and uneven-aged (single tree, diameter-limit, basal area, group selection, etc.) approaches. Included within these methods is an option to use disturbance mechanisms (e.g., fire, TSI, etc.) to reduce competition and achieve maximum growth potential of the desired species. Inherently, these various approaches result in different community or “management phases” and possibly alternate states. The decision to represent these varying methods and management strategies into a single state and phase at this time hinges on the need for additional information in order to formulate definitive pathways, management actions, and community responses. Forthcoming inventories of this site will provide more detail on this state and associated management phases.

Of warning, there are significant timber management limitations due to alternating seasonal wetness and dryness; the latter often rendering the soil very hard and compact. These collective impacts could lead to high seedling mortality and/or low productivity of individual trees. Implementing this state or management option on this site should be carefully reviewed and considered.

Submodel

Description

This alternative state is included to represent the range or breadth of conservation actions that may be implemented and established should other land uses be discontinued within a given location. Several actions may be chosen including the standard of establishing: native warm season grasses; suitable forbs for pollinators; select native trees to manage for forest or woodland conditions. If at all possible, the herbaceous species established should be derived from the “wild types” (genetic stock) from the Loess Plains or from adjoining ecoregions. This action would help preserve the unique genetic material from the area and would help to reintroduce the native herbaceous taxa back into a portion of their former range.

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