Northern Moderately Wet Loess Interfluve

Description

The reference state of this ecological site was chosen to represent the breadth of community types that historically occurred across the loess capped uplands of MLRA 134. Exemplary examples of the full range of plant communities and ecological processes that were once commonplace on this ecological site no longer exist. Where trees occur today, they typically form a closed canopy forest comprised of exotic species and an understory entangled by native and non-native vines. Vestiges of this once vast system are primarily relegated to cutover forest blocks, narrow roadway and powerline corridors, and corners of old fields and pastures that now hold the only remaining examples of native prairie vegetation (Estes et al., 2016). Therefore, a complete and exhaustive description and treatment of this system cannot be provided. However, some native plant species that comprised the woodlands, flatwoods, and prairies of long ago still exist. It is from these instances coupled with historical accounts that we project reference conditions of the site.

The name of the reference state, “woodland and prairie,” implies the existence of systems maintained and directly influenced by fire. The accounts provided by Loughridge (1888), Gardner (1876), and many others are testament of the historic importance of fire on the Loess Plains, some natural but most were first induced by Native Americans and second, by early settlers striving to maintain and enhance pasturage.

The “wet-dry” descriptor pertains to the soils’ capacity to perch water during wetter times of the year followed by droughty conditions during the drier period, such as late summer and fall. This site is anticipated to differ from its associated sites, Northern Loess Fragipan Upland and Northern Wet Loess Interfluve, due to its intermediate wetness capacity. This site is anticipated to support wetter species, especially certain herbaceous taxa, than the former and is better drained and has slightly more slope than the latter. With respect to upland flatwoods, this site would potentially support drier conditions and associated species. It must be emphasized that this site is in provisional status at this time and much more investigative work is needed before a clear description can be provided.

It is due to this lack of information that restoration pathways are not provided for this site. In order to reconstruct or establish simulated reference conditions, a Conservation state has been added to the state and transition model.

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Description

Agriculture production is the dominant land use activity on this site, today. Most cropland is relegated to the Loess Plains and in other areas of little topographic relief (generally long, gradual slopes).

Submodel

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 accelerated erosion and colonization sites of undesirable plants or weeds.

Establishing an effective pasture management program can help minimize the rate of weed establishment and assist in maintaining vigorous growth of desired forage. An effective pasture management program includes: selecting well-adapted grass and/or legume species that will grow and establish rapidly; maintaining proper soil pH and fertility levels; using controlled grazing practices; mowing at proper timing and stage of maturity; allowing new seedings to become well established before use; and renovating pastures when needed (Rhodes et al., 2005; Green et al., 2006). 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.

Submodel

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 approaches 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, depending on one’s perspective. The decision to represent these varying approaches and management results 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.

It should be noted that there are some limitations to timber management on this site due to seasonal wetness. To avoid and/or limit rutting, compaction, and erosion of soils, harvests should be relegated to drier periods of the year. An additional limitation to this site may be due to the presence of a fragipan (or root restriction layer) and seasonal dryness. Broadfoot (1976) provided site indices for a list of hardwoods occurring on one of the soils associated with this site, the Calloway series. Most site indices of hardwoods on this site were 20 percent less than the indices of the same species occurring on well drained loessal soils such as Memphis. In general, hardwood productivity of this site is lower relative to production on better drained soils.

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; establishing a suite of suitable forbs for pollinators; establishing select native trees and managing for open woodland/savanna conditions.

Of the options available, the one that best mimics the perceived reference conditions of this site would provide the best case conservation scenario. This action requires a concerted effort to reestablish herbaceous species most common to the prairies (“barrens”) of western Kentucky, West Tennessee and Mississippi with the possible addition of widely spaced hardwoods (e.g., upland oaks from the reference state) mimicking savanna to open 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 prairie system back into a portion of its former range.

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