Northern Natric Loess Terrace

Description

The following treatment of the reference state is based on observations and literature review of similar soils in the Western Lowlands ecoregion in eastern Arkansas and southeast Missouri. Field investigations must be conducted to adequately and accurately describe the plant communities and ecological dynamics of this site east of Mississippi River.

The key factors influencing the plant community of this site are the soils. The high exchangeable sodium of the subsoil limits the types of plants that can tolerant these extreme conditions. Heineke (1987) compared the natural community of this site to the “…xeric, acidic, rocky blufftops of the Ozark Plateau.” The trees are stunted, twisted, and small with diameters that seldom reach 12 inches. Heineke reported an instance where trees below 12 inches had ages of 170 years, and the structure of the stand was park-like with much of the ground surface being covered by lichens.

The pre-settlement community of this ecological site may have consisted of a complex of physiognomic characteristics that included meadow or barren-like conditions, savannas, and open woodlands. Fire may have been a key disturbance factor, historically, particularly where fires extended onto this site from adjoining or nearby areas. Barren-like conditions (i.e., local bare spots) may have existed locally where depths to natric horizons were very shallow. Such “bare spots” would represent pedons of extreme root restriction.

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. However, soils exhibiting the core concepts of this site (i.e., a relatively shallow depth to a root restriction layer of high sodium content), are known for producing poor pasturage. Areas where natric horizons are deeper have a much better chance in pasture development and management.

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, further complicating the natural limitations of this site. Because of the limitations of this site, grazing may be limited to small intervals within the appropriate season(s). These soils have low available water capacity, low nutrients, and are prone to droughtiness. 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.

Submodel

Description

Agriculture production on this site is fairly limited. Crops that are or have been grown include soybean and cotton but plants may be stunted and often will not reach maturity (Pettry and Switzer, 1998; USDA-SCS, 1978). Many idle woodlots today were likely cropped at some point in the past and met with disappointing results.

Submodel

Description

Most, if not all, of the woodlots and local patches of woodlands occurring on this site represent this state. Former cropland and pastureland that failed to meet expectations were abandoned and are now considered “idle”. These stands still support some of the components that characterizes the community. The structure of these stands are typically denser than a late development, fire-influenced stand. However, small openings and a ground cover of herbaceous species provide indications of strong edaphic influences. Restoration potential of these sites back to reference conditions may be fairly high, provided the appropriate management regime is initiated and maintained. Where depth to the natric subsoil is much greater, productivity and plant composition may be very different. More work is needed to ascertain the full characteristics of this ecological site.

Submodel