Ecological dynamics
Historically, this ecological site was part of a vast forested landscape with processes and functions directly connected to the highly dynamic nature of the Mississippi River (Gardiner and Oliver, 2005). Today, this site is effectively disconnected from the river via the vast network of constructed levees and, in many areas, local drainage controls. Widespread changes to the landscape occurred long before any intensive studies of the historic natural communities were conducted. Accordingly, reference conditions of this ecological site are still under review.
The soils of this site are often associated and grouped with other clayey soils of backswamp or “slackwater” environments, such as the Sharkey and Alligator soil series. However, this ecological site is positioned a little higher in elevation, and the loamy subsoils, where present, have better internal drainage than the very deep, heavy clays of either Sharkey or Alligator soils. Although mapped in a variety of floodplain settings, a characteristic occurrence (or distribution) of these clayey over loamy soils is along the lower and wetter periphery of recent natural levees where they typically extend to the lower and much wetter backswamps, often adjoining Sharkey soils (USDA-SCS, 1958; USDA-SCS, 1961). This ecological site forms a soil and vegetation gradient or transition from the higher riverfront hardwoods of the recent natural levees and point bars to the low, overcup oak – water hickory community of the wet, clayey backswamps (see Ecological Site ID F131AY302MS).
Species occurring on this site consist of a mix of riverfront hardwoods that are tolerant of wet conditions in addition to components that typically occur in low backswamp environments. Tree species listed as frequently occurring on the dominant soils of this site include sweetgum, Nuttall oak, water oak, willow oak, American elm, sugarberry, and red maple. Associates or species occasionally occurring include green ash, eastern cottonwood, cherrybark oak, Shumard's oak (Quercus shumardii), pecan, common persimmon, American sycamore, cedar elm, and black willow (Broadfoot and McKnight, 1961; Broadfoot, 1976). The wettest locations may support occasional occurrences of overcup oak and water hickory (Broadfoot and McKnight, 1961).
The species reportedly occurring on these soils overlap with components that are associated with three major forest types, including their variants: sweetgum – willow oak (Society of American Foresters, SAF, type No. 92), American sycamore – pecan – American elm (SAF type No. 94, Mississippi River Valley variant) and sugarberry – American elm – green ash (SAF type No. 93; Eyre, 1980). An important characteristic that has been repeatedly stressed by forest authorities is the transition of the sweetgum – willow oak (often referred to as sweetgum – water oaks or red oaks) and American sycamore – pecan – American elm types to the sugarberry – American elm – green ash association following major disturbances such as heavy cutting or repeated partial harvests (Putnam and Bull, 1932; Putnam, 1951; Hodges, 1997; Oliver et al., 2005). Today, the prevailing association occurring on this ecological site may be the sugarberry – American elm – green ash forest association or a variant of this type given the intensive land use histories most areas have incurred. Eyre (1980) provides a general description of the sugarberry – American elm – green ash type and several components listed above are associates of that type including species that are highly favored in management on this ecological site, such as Nuttall oak, willow oak, water oak, sweetgum, and green ash. Oliver et al. (2005), however, warns that red oaks (e.g., cherrybark, willow, water, and Nuttall) are not regrowing in sufficient concentrations to sustain their former densities, which could impact other factors such as wildlife and commercial timber values. These concerns are founded on forest composition transitioning to a dominantly shade tolerant community such as the sugarberry – American elm – green ash type. Hodges (1997) emphasized that the latter is long-lived and capable of self-replacement.
Overall, natural cover types on this site are minor compared to other uses. Most areas have been cleared and are used extensively for production, and many areas have been land leveled to meet irrigation needs. A secondary use on this site is pasturage.
Following this narrative, a “provisional” state and transition model is provided that includes the “perceived” reference state and several alternative (or altered) vegetation states that have been observed and/or projected for this ecological site. This model is based on limited inventories, literature, expert knowledge, and interpretations. Plant communities may differ from one location to the next depending on the severity of local land use activities and rates of deposition. Depending on objectives, the reference plant community may not necessarily be the management goal.
The environmental and biological characteristics of this site are complex and dynamic. As such, the following diagram suggests pathways that the vegetation on this site might take, given that the modal concepts of climate and soils are met within an area of interest. Specific locations with unique soils and disturbance histories may have alternate pathways that are not represented in the model. This information is intended to show the possibilities within a given set of circumstances and represents the initial steps toward developing a defensible description and model. The model and associated information are subject to change as knowledge increases and new information is garnered. This is an iterative process. Most importantly, local and/or state professional guidance should always be sought before pursuing a treatment scenario.
State 1
Reference: Wet Bottomland Forest
Removal of the pre-settlement natural communities of this site occurred long before thorough studies and investigations were conducted. Modifications to the Yazoo Basin’s natural hydroperiod and drainage patterns coupled with location-specific land use histories have further complicated species-site relationships. Such complexity across the Yazoo Basin will likely be reflected in much variability in vegetation composition and structure of local forest stands (Stanturf et al., 2001). Accordingly, reference conditions for this site have yet to be confirmed, but they are perceived to consist of mature forest stands that support a diverse mix of southern bottomland hardwoods adapted to the somewhat poorly and poorly drained soils of this site. Once assigned or identified, the reference community will not represent the pre-settlement forest community, but it should identify an assemblage of naturally occurring species that reflects and contributes to regional biodiversity and local forest ecology. Implicated in the latter is that the “local” geomorphic features and drainage patterns of this soil-site environment should not have been drastically altered or removed (e.g., land leveled).
The return or transition pathway from the altered states (currently, only State 2) back to reference conditions is intended to represent the suite of hardwood species that, reportedly, frequently to occasionally occur and are favored in management on this site. Realistically, it may not always be possible to return to a “perceived” reference state from a former altered condition. While planting and establishing trees appropriate for a site may be possible, achieving restoration of the understory and other system functions are challenges that may never be realized (Stanturf et al., 2001; Flinn and Vellend, 2005).
Community 1.1
Mixed Bottomland Hardwoods
Components of the reference community are likely to vary by location depending on the local environment. This site mainly occurs as a bridge between the poorly drained periphery of the recent meander belt and the very wet, clayey backswamp environments of the flood basin. Where the site occurs along active tributaries or stream systems, plant composition and structure may be strongly influenced by flooding frequency and duration, deposition or overwash, and pre-existing vegetation along the stream corridor or floodplain. Still, many of the same components are likely to occur in both environments, although dominance patterns may vary.
Species reportedly occurring in older stands of this site include sweetgum, Nuttall oak, water oak, willow oak, American elm, sugarberry, and red maple. Associates or species occasionally occurring include green ash, eastern cottonwood, cherrybark oak, Shumard’s oak (Quercus shumardii), pecan, common persimmon, American sycamore, cedar elm, boxelder (Acer negundo), red mulberry (Morus rubra), and black willow (Broadfoot and McKnight, 1961; Broadfoot, 1976). The wettest locations may support occasional occurrences of overcup oak, water hickory, and bald cypress (Taxodium distichum) (Broadfoot and McKnight, 1961). Species characteristic of local floodplains and active tributaries include river birch (Betula nigra), eastern cottonwood, black willow, American sycamore, boxelder, American elm, sugarberry, and green ash. Understory composition may be quite variable depending on the degree of canopy openings or overstory shade but often consist of seedlings and saplings of the preceding in addition to American hornbeam (Carpinus caroliniana), possumhaw (Ilex decidua), blackberry (Rubus spp.), and giant cane (Arundinaria gigantea). A dense woody vine cover is typically present and often represented by poison ivy (Toxicodendron radicans), grape (Vitis spp.), Virginia creeper (Parthenocissus quinquefolia), peppervine (Nekemias arborea), American buckwheat vine (Brunnichia ovata), greenbrier (Smilax spp.), and trumpet creeper (Campsis radicans) (Eyre, 1980; Meadows and Nowacki, 1996; MMNS, 2015).
It’s important to note that a shift in species composition towards a shade tolerant community such as the sugarberry – American elm – green ash type may occur in some stands depending on local land use history. While a precise reference community of this site has not been determined with field validation, interpretations based on data and field studies produced by regional forest authorities suggest that the sweetgum – willow oak forest type, and its variants, are representative (Putnam and Bull, 1932; Putnam, 1951). Several components of the type are highly prized and valued by industry, wildlife and forest specialists, and enthusiasts for the ecological services they provide (Oliver et al, 2005). Broadfoot (1976) provided the following site index ranges (base age 50 years for all species except cottonwood, which is 30 years) and the measured average for select components that are “favored in management” on the dominant soils, the Tunica soil series: Nuttall oak (90-110; average 98 feet), water oak (80-100; average 88 feet), willow oak (80-100; average 90 feet), cherrybark oak (85-105; average 96 feet), sweetgum (85-105; average 86 feet), American sycamore (90-110 feet), eastern cottonwood (90-110 feet), green ash (70-90 feet), and pecan (80-100 feet).
Dominant plant species
-
sweetgum (Liquidambar styraciflua), tree
-
Nuttall oak (Quercus texana), tree
-
water oak (Quercus nigra), tree
-
willow oak (Quercus phellos), tree
-
American elm (Ulmus americana), tree
-
sugarberry (Celtis laevigata), tree
-
red maple (Acer rubrum), tree
-
green ash (Fraxinus pennsylvanica), tree
-
cherrybark oak (Quercus pagoda), tree
-
American sycamore (Platanus occidentalis), tree
-
possumhaw (Ilex decidua), shrub
-
blackberry (Rubus), shrub
-
eastern poison ivy (Toxicodendron radicans), shrub
-
peppervine (Nekemias arborea), shrub
-
American buckwheat vine (Brunnichia ovata), shrub
-
greenbrier (Smilax), shrub
-
trumpet creeper (Campsis radicans), shrub
-
Virginia creeper (Parthenocissus quinquefolia), shrub
-
grape (Vitis), shrub
State 2
Commercial Forestland
This state consists of two very different community phases and management approaches. Community Phase 2.1 represents forest management and production on this site. A distinguishing feature of this phase is the level of management intensity designed to maximize merchantable goals. Various silvicultural methods are available for selection, and these are generally grouped into even-aged (e.g., clearcutting, seed-tree, and shelterwood) and uneven-aged (e.g., single tree, diameter-limit, basal area, and group selection) approaches (Meadows and Stanturf, 1997). Depending on the method selected, different structural and compositional characteristics of the stand may result. Removal and control of community associates are typically a critical element of production goals. These actions may result in different community or “management phases” (and possibly alternate states) depending on the methods used and desired results. Finding the appropriate approach for a given stand and environment necessitates close consultation with trained, experienced, and knowledgeable forestry professionals. If there is a desire to proceed with this state, it is strongly urged and advised that professional guidance be obtained and a well-designed silvicultural plan developed in advance of any work conducted.
Community Phase 2.2 represents conditions of many stands that have incurred indiscriminate timber harvests (e.g., heavy cutting or diameter-limit harvests of select species) and opportunistic regrowth following such harvests (i.e., no management at any period). Some stands may continue to support a few desirable species and quality stems, but in many instances, affected stands will be comprised of mostly shade tolerant species or trees of desirable species that are defective and fail to meet their maximum potential. (Because of the intensive management required to rehabilitate affected stands, this community phase may warrant elevation to a standalone state. This should be considered in future iterations of this site’s development.)
Although this site is well suited for forest production, seasonal wetness imposes moderate to severe limitations for some forest operations. The principal management concerns are equipment limitations, intense plant competition, and seedling mortality (USDA-SCS, 1990; USDA-NRCS, 2004). Seasonal wetness and periods of heavy precipitation can impose limitations on heavy equipment usage. If possible, equipment operations are best conducted during drier periods of the year, which minimizes soil damage, compaction, erosion, and helps to maintain productivity. A seasonal high water table can kill recently planted seedlings, especially if they are not suited to these wet soils. Conversely, exceedingly long dry periods during the critical “spring flush” in March and April may also lead to seedling mortality, especially on shallow clayey over loamy soils (Mike Oliver, personal communication).
An important caveat of this state is its representation of forest conditions that have retained full site production potential. Currently, transitional pathways to this state originate from another forested state (State 1), only. Former land uses (alternate states) that result in altered conditions of the soil environment (e.g., land leveling) may deleteriously affect predicting and planning for species site selection, tree productivity, and possibly survival of the targeted species. State 6 (Forest Recovery) is representative of forest establishment and growth on locations where soil compaction and reduction of nutrients have occurred due to former land practices. Once a previously affected location has recovered its site potential, transition to this state may be possible. That potential transition is still under review and is currently not shown or addressed in the state and transition model.
Community 2.1
Forest Management
Prescribing a silvicultural system for a given stand depends on species composition and long-term production and postproduction goals (Gardiner et al., 2002). The canopy trees listed in Community Phase 1.1 as “favored in management” are all production options on this site ranging from single species plantations to complex multi-species stands. (Select species favored in management are indicated below under the "Dominant tree species" section for convenience.)
Broadfoot’s (1976) list of species favored in management consists of taxa that are associates of one of the more highly prized forest types of the Southern Mississippi River Alluvium, the sweetgum – willow oak type (Putnam, 1951). Managing for the oaks of this type may be preferred given the multiple values they provide (e.g., timber and wildlife). However, maintaining that component beyond a single rotation (or harvest) may be the most challenging. Creating conditions that promote oak persistence in future stands require a sufficient advance regeneration component. Ensuring that this future crop is established will require close adherence to a well-designed silvicultural plan, which requires programmatic intermediate operations (e.g., improvement cuttings, thinnings, and other partial cuttings). An even-aged silvicultural system that utilizes the clearcutting regeneration method along with brush management to reduce subsequent competition is typically the advocated approach when harvesting bottomland oak stands (Johnson and Shropshire, 1983; Clatterbuck and Meadows, 1993; Hodges, 1995; Meadows and Stanturf, 1997; Oliver et al., 2005). Of caution, some species that are favored in management may not be suitable for planting in every location of this ecological site. Species that are adapted to drier or better drained environments such as cherrybark oak may experience higher seedling mortalities if they are planted in areas that tend to flood or pond for long to very long durations (Mike Oliver, personal communication). Additionally, Broadfoot (1976) cautioned against planting oaks in locations where soil pH is around 7.5. Therefore, each targeted location should be carefully assessed and examined before costs are incurred and seedlings planted.
Except pecan, the remaining trees that are favored in management are light-seeded species. A variety of silvicultural systems may be implemented to promote production of these species including even-aged and group selection (uneven-aged) approaches (see Meadows and Stanturf, 1997). Eastern cottonwood, however, has different challenges due to its extreme shade intolerance and its inability to cast dense shade over the understory. Due to shade intolerance, it cannot succeed itself naturally and requires mechanical site preparation (or scarification) to expose the soil surface prior to establishing and reestablishing following harvests. The relatively “light shading” that its canopy produces permits invasion of shade tolerant species. Many such stands may have dense midstories and understories of American sycamore, pecan, green ash, sugarberry, American elm, boxelder, silver maple, and occasionally sweetgum (Johnson and Shropshire, 1983; Hodges, 1995; Meadows and Stanturf, 1997).
Community 2.2
Non-managed/High-graded
This forest community is directly influenced by former harvesting practices that include repeated single-tree selection or diameter-limit harvests with no additional management activities (i.e., brush management, competitor control, etc.). These practices typically target the highest quality trees of the most desirable species. The result is usually an expansion and in-filling of shade tolerant subcanopy trees. Over time, this practice will lead to a predominantly shade tolerant community that may be comprised of American elm, sugarberry, cedar elm, boxelder, red maple, red mulberry, roughleaf dogwood, and possumhaw (Putnam et al., 1960).
Pathway 2.1A
Community 2.1 to 2.2
This pathway includes heavy cutting of the stand that removes the desired species (typically shade intolerant species) of sufficient diameters or repeated single-tree harvests (e.g., diameter-limit cuts) that removes the desired species followed by no management of the residual stand. The resulting stand is typically comprised of shade tolerant species with low commercial value.
Pathway 2.2A
Community 2.2 to 2.1
Intensive management will be required to push a shade tolerant community into a more commercially desirable and viable system. Actions will likely require a complete clearcut of the stand followed by repeated brush and competitor control (chemical and mechanical). If there is a lack of seed source, artificial regeneration will likely be required to reintroduce heavy-seeded species (e.g., oaks). Continual competitor control will be needed.
State 3
Cropland
This state is representative of the dominant land use activity on this ecological site, agriculture production. Crops reportedly grown on the dominant soils of this site include cotton (Gossypium hirsutum), corn (Zea mays), soybeans (Glycine max) and small grains such as wheat (Triticum aestivum) (Snipes et al., 2005). Minor crops, such as some specialty crops (e.g., fruits, vegetables, and tree nuts such as pecans), may be grown locally.
These soils are moderately to well suited to agriculture production depending on local hydrologic regimes, drainage patterns, and the intended crop (USDA-SCS, 1958; USDA-SCS, 1961; USDA-NRCS, 2004). They have moderate to high available water capacity, high natural fertility, and soil reactions that range from mildly acid to moderately alkaline. Applications of fertilizer and lime may not be a necessity everywhere or in every circumstance as these soils are naturally high in phosphorus and potassium and pH levels are generally within a favorable range. Soil tests should be conducted to determine fertilizer, lime, and nitrogen needs on a specific field and for a given crop (USDA-SCS, 1990). Management concerns are largely centered on seasonal high water tables, very slow permeabilities, slow runoff, delayed plantings, soil compaction under equipment traffic, poor tilth, development of a plow pan, and moderate organic matter content (USDA-SCS, 1990; USDA-NRCS, 2004). Areas that are prone to flooding or extended periods of wetness may not be suitable for small grain crops or to crops that require planting in April and May (USDA-SCS, 1990). Management measures to ameliorate some of these issues may include implementing a conservation tillage or management system; subsoiling to breakup plow pans; restricting tillage to appropriate soil moisture content; and establishing a drainage system or network in problematic areas (USDA-NRCS, 2004; USDA-NRCS, 2006b). Of caution, subsurface drainage systems (e.g., pipes or tiles) may not be effective in every situation due to very slow permeability or localized flooding (USDA-SCS, 1990). Major components that producers generally develop and plan are proper selection of crop cultivar, pest control, cropping system, tillage methods, nutrient management, and water management (Snipes et al., 2005). Key practices of some cropping systems often include two or more crops grown in a multiyear rotation, which has been documented to disrupt pest cycles. Leaving crop residue on the surface can help to maintain tilth, fertility, and organic matter content – all critical elements of soil quality and health. For monoculture cropping systems, the implementation of well-designed pest and nutrient management systems are imperative (Pringle et al., 2017). (For assistance, interested parties are advised to visit their local NRCS Field Office.)
Three separate management phases comprise this state: Conservation Management (3.1), Transitional Conservation Management (3.2), and Conventional Management (3.3). The three phases consist of varying tillage methods and approaches to soil health management systems.
Community 3.1
Conservation Management
This cropland phase utilizes long term, continuous conservation management systems that include reduced till and cover crops; no-till with cover crops; crop residue retention; and perennial cropping systems. The guiding principles of this system are minimizing soil disturbance and maximizing soil cover, biodiversity, and the presence of living roots. Implementing diverse crop rotations while maintaining these principles can lend to the development of an integrated pest management plan and contribute to overall system resilience.
Of caution, the above-ground crop growth or yields may not be the best tracking mechanism for assessing the efficacy or presence of this management phase. Indicators of these systems are generally determined via soil-site assessments with outcomes that may include enhanced soil aggregate stability, increased soil biological activity, higher organic matter content, and improved water holding capacity and infiltration rates while also alleviating soil compaction and reducing runoff and erosion (Chessman et al., 2019). Additional advantages to this system that have been noted by some producers are reductions in fuel and labor costs and less wear and tear on machinery and equipment.
There are challenges to this management system, especially in situations where tillage may be considered and/or needed to repair weather damage or other detrimental impacts. Implementation of conventional tillage even after long term conservation practices (e.g., no-till) can reset the affected area back to a conventional cropping system. However, those changes can be reversed and a return to a conservation management system is achievable.
Critical conservation practices associated with this phase include cover crops, no-till, and reduced till as the foundational practices. Additionally, this phase may include supporting and site-specific practices to address conservation needs for a given location.
Community 3.2
Transitional Conservation Management
This cropland phase utilizes a hybrid approach that combines conventional methods with conservation practices at specific periods and under specific situations. Practices under this phase may include a combination of conventional till, reduced till, strip till, and the inclusion of cover crops. For instance, perennial crop species could be in a continuous transitional phase where conventional tillage is implemented at the time of planting followed by reduced tillage during the rotation. Planted forage crops could also be included in this phase, especially when part of a crop rotation that utilizes reduced tillage for one crop followed by conventional tillage for a succeeding crop.
The development, implementation, and refinement of nutrient and pest management plans throughout component operations are imperative. Additionally, this phase may include supporting and site-specific practices to address conservation needs for a given location.
Community 3.3
Conventional Management
This management phase is representative of conventional cropland where tillage is implemented as an annual component of the production system. As crucial elements of the system, conservation practices such as nutrient and pest management are needed to address fertility requirements and pest concerns within the crop cycle. It is important to note that this phase may develop when tillage is implemented to address damage or for other purposes while under a conservation management system (Community Phase 3.1). There could also be associated, supporting, and site-specific practices that are needed to address specific conservation needs. Specific needs may include grade stabilization structures to control gully erosion, grassed waterways to trap sediment from sheet and rill erosion, or implementing reduced till.
Pathway 3.1A
Community 3.1 to 3.2
Soil disturbance (tillage); reduction of soil health.
Pathway 3.1B
Community 3.1 to 3.3
Conventional tillage, seeding, and fertility management for crops.
Pathway 3.2A
Community 3.2 to 3.1
No-till, cover crops, reduced till-soil health improvements.
Pathway 3.2B
Community 3.2 to 3.3
Conventional tillage, seeding, and fertility management for crops.
Pathway 3.3A
Community 3.3 to 3.2
Reduced till, no-till, and cover crops with soil health improvements as a goal.
State 4
Land Formed Cropland
This level to nearly level ecological site oftentimes adjoins gently sloping to undulating landscapes. It is bordered by soils of varying textures and drainage characteristics. Accordingly, inconsistencies in wetness and dryness, ease of operation, and production or yields may occur across a cropped location. An increasingly common practice consists of land forming or leveling surface irregularities into a predetermined and engineered, uniform slope. This practice removes drier and higher features, which are then used to fill wetter and lower positions (e.g., depressions or swales) across the targeted area. Advantages of land leveling may include reduced hazards of erosion and runoff rates, improved surface drainage, and enhanced distribution and conservation of irrigation water. Disadvantages of the practice is a churning of various surface and subsurface materials (former soil horizons) that no longer occur in a predictable or regular pattern. Organic matter content in the surface layer is generally low, and the surface tends to crust and pack after heavy rains (USDA-NRCS, 2006b). One potential hazard that appears to be emerging in some areas is the need for managing surface water runoff. As both irrigated and stormwater runs off leveled fields at uniform rates, surface water tends to collect cumulatively and simultaneously, which places tremendous demands on local drainage systems. Without “in field” structures (natural or artificial) to stagger runoff, the downslope (or lower) ends of some fields tend to back flood thereby contributing to more flooding overall in local watersheds (personal observations).
Immediately following land leveling, the constituent elements of soil health are likely to be absent. In some areas, producers have initiated practices such as applying organic residues (e.g., poultry litter) or growing rice crops for one to two years to rapidly boost fertility and introduce organic matter (via rice biomass) in the surface layer. Over time, the full complement of the management (or community) phases of State 3 may be possible on land leveled fields. They are not repeated or indicated here.
Currently, this state serves as an endpoint in the state and transition model because the ability to predict vegetation response when transitioning to a different state is no longer possible without soil-site investigations for each area of interest. The former soils of this ecological site, including surface and subsurface horizons, will have been redistributed as particles among other former soils depending on the depth of the initial “grade cuts” and leveling efforts.
Community 4.1
Land Leveled Cropland
Some of the crop species and management practices indicated and discussed in State 3 (including all three management phases) may be suitable for establishing on land leveled areas that once supported the soils of this site. However, the type of crops suited for newly leveled areas may ultimately depend on the prevailing soil particle-size distribution and internal drainage characteristics. Former studies on precision leveled fields have noted variabilities and inconsistencies in soil particle-size distributions, bulk density, soil biological properties, and nutrients (Brye et al., 2003; Walker et al., 2003; Brye et al., 2006). Management concerns for this phase may consist of restricted permeability, low organic matter content, and crusting and packing (USDA-NRCS, 2006b). These impacts may be improved by implementing conservation tillage, cover crops, retaining crop residue, and nutrient and pest management strategies.
State 5
Pastureland/Grassland
This state is representative of areas that have been converted to and maintained in pasture or grassland. In 1991, the soils of this site were placed in Pasture Suitability Group 4a for the State of Mississippi. This group consists of somewhat poorly and poorly drained nonacid clayey soils with a root zone of 20 to 40 inches. Limitations of this state are mainly associated with a seasonally high water table and the flooding of areas that are located along active tributaries. High water tables over long durations will restrict root growth and establishing plants in particularly wet locations may prove challenging. These soils are suited to most commonly grown forage species except bahiagrass (Paspalum notatum), crimson clover (Trifolium incarnatum), and some cool season annual forage plants. Note that bahiagrass and crimson clover do not respond well where soil reactions are above 6.5 (Houck, 2009; Young-Mathews, 2013). Overall, forage production is considered moderate to high when adequately fertilized and properly managed. Lime may not be needed on these nonacid soils.
Given that this ecological site occurs on lower, wetter soils, some forage operations may experience multiple wetness events in a single year. Management concerns are mainly centered on soil compaction due to grazing (USDA-NRCS, 2006b), and overgrazing can lead to numerous bare spots and muddy conditions that effectively reduces or destroys plant establishment and productivity. Planning or prescribing the intensity, frequency, timing, and duration of grazing will be very important on these wetter soils. Of caution, some annual and perennial winter plants naturally growing in wet locations (e.g., sedges, rushes, and some forbs) may be an additional challenge as these are often unpalatable or toxic if consumed.
Flood-prone areas may limit the type of forage suited for this site. In areas that flood on a regular basis, implementing management actions such as planting or overseeding appropriate cool season forage varieties (e.g., ‘Marshall’ ryegrass, Lolium perenne ssp. multiflorum; also known as annual ryegrass) into established warm season grasses at heavy forage rates have been observed to help protect riparian areas from detrimental river or stream scouring (personal observations by Rachel Stout Evans, contributing author). Initiating such remedial actions aid in the recovery and reestablishment of preferred warm season forage following seasonal flooding. (Note that herbicide resistant varieties could be problematic and may warrant reconsideration. Please consult with local NRCS Field Offices for assistance.) Where permissible, a system of artificial drainage or water control structures may be in place to facilitate continued forage production and grazing during wetter periods. Additionally, adjacent higher elevation or protected areas may be needed for the storage of harvested forage or the holding of livestock when wet or flooded conditions occur.
Establishing an effective pasture management program can help minimize degradation of the site and assist in maintaining 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 newly seeded areas to become well established before use; and renovating pastures when needed (Rhodes et al., 2005; Green et al., 2006).
This state consists of four community phases that represent a range of forage management options and pasture and hayland condition scenarios. Options range from establishing a forage monoculture for haying to a broad mixture of forage species for production and grazing. It is strongly advised that consultation with local NRCS Service Centers be sought when assistance is needed in developing management recommendations or prescribed grazing practices.
Community 5.1
Monoculture Grassland
This phase is mainly characterized by planting forage species for hay production. Forage plantings generally consist of a single grass species. Native and non-native forage species can be seeded and is usually harvested as hay or haylage, although grazing may occur periodically. These environments are generally productive for forage and can provide ecological benefits to control soil erosion. Allowing for adequate rest and regrowth of desired species is required to maintain productivity. Maintenance of monoculture stands also requires control of unwanted species, which will require pest and nutrient management.
Forage suited for this community phase include hybrid and common Bermudagrass (Cynodon dactylon), dallisgrass (Paspalum dilatatum), or possibly sorghum-Sudangrass hybrid (Sorghum bicolor ssp. drummondii) in drier locations. Tall fescue (Schedonorus arundinaceus) may be an option in the northern portions of the basin. The application of fertilizer is generally needed to establish and maintain improved desirable hayfields and pastures. An additional measure to aid production may include prescribed grazing. Implementing limited and monitored grazing can promote deeper root penetration of grasses with the added benefit of greater nutrient and moisture uptake. This synergistic approach can lead to increased production of and may sustain desirable forages.
Conservation practices should include prescribed grazing or forage harvest management, nutrient and pest management, and potentially other site-specific practices.
Community 5.2
Mixed Species System
This community is characterized by mixed species composition of grasses and legumes. Components of this forage system are either planted or they established naturally. Typically, perennial warm-season grasses are the foundation of the stand that are periodically overseeded with adapted cool-season forages. The latter creates an added benefit of extending the grazing season. This community phase can be highly productive for grazing and haying operations and can provide beneficial habitat for some wildlife species.
Maintenance of grass stands also requires a series of management practices such as prescribed grazing, brush management, pest management, and nutrient management to maintain production of the desired species. Prescribed grazing includes maintaining proper grazing or forage heights, timing, and stocking rates. Supporting or facilitating practices such as fences, water lines, and watering facilities could be part of the system that maintains this phase.
Community 5.3
Mixed Species, Non-seeded
This community is characterized by a mixture of native and naturalized non-native species. Forage is usually grazed or harvested as stored forage, hay or haylage. Commonly established species may include Bermudagrass, dallisgrass, and potentially tall fescue in the north.
Stands are generally productive, and forage and grazing management can maintain the community. Healthy stands provide additional benefits by protecting soils from excessive runoff and erosion. However, a common peril associated with this phase is overgrazing, which lowers production and favors less palatable weedy species, especially in areas where livestock congregate. Proper stocking rates or grazing systems that allow for adequate rest and plant regrowth are required to maintain productivity. When forage species are afforded adequate recovery time between grazing intervals, they develop deeper root systems and greater leaf area. Conversely, when plants are not allowed to adequately recover, root development will be restricted leading to lower forage and biomass production. Additionally, maintenance of grass stands requires implementing pest management practices to control unwanted weedy and woody species.
Community 5.4
Early Woody Succession
This community is characterized by a diverse composition of grasses and forbs with an increasing presence of woody species (both native and non-native) that are immature and of low stature. Woody species grow quickly on this site and can be difficult and expensive to control. One potentially problematic species may be honeylocust (Gleditsia triacanthos). Putnam (1951) reported honeylocust as being common on old pastures, and the species can be difficult to remove once established. Management to transition this phase to other forage communities of this state is still possible without excessive inputs and effort, particularly if stem diameters remain below 2 inches and are widely scattered (e.g., a density of less than 100 stems per acre). However, if diameters become greater than 3 inches and densities exceed 300 stems per acre, far more investment, effort, and inputs will be required. If brush management measures are not undertaken, the plant community will transition to the Ruderal/Opportunistic Regrowth (Community Phase 6.1) of State 6.
Of note, this community phase is often very beneficial habitat for some wildlife species, especially a specific guild of resident and Neotropical migratory bird species that are habitat-specific on old field to young tree stand habitats.
Pathway 5.1A
Community 5.1 to 5.2
Seeding and/or management for desired species composition.
Pathway 5.1B
Community 5.1 to 5.3
Species management without overseeding.
Pathway 5.2A
Community 5.2 to 5.1
Seeding, fertilizing, management/removal of undesirable species.
Pathway 5.2B
Community 5.2 to 5.3
Species management without overseeding.
Pathway 5.3A
Community 5.3 to 5.1
Seeding, fertilizing, management/removal of undesirable species.
Pathway 5.3B
Community 5.3 to 5.2
Seeding and/or management for desired species composition.
Pathway 5.3C
Community 5.3 to 5.4
Lack of disturbance; no (or infrequent) mowing, herbivory, or brush management; natural succession of woody species.
Pathway 5.4A
Community 5.4 to 5.3
Brush management/removal of unwanted species.
State 6
Forest Recovery
This state is representative of forest recovery in areas that were once under former intensive land use such as long-term row crop cultivation. Characteristics that distinguish this state from other forest states on this site include a suite of soil-site properties that reportedly affect tree growth such as higher soil bulk density due to compaction, presence of a plow pan, lower organic matter content, and reduced fertility (Baker and Broadfoot, 1979; Groninger et al., 1999). Two community phases are provisionally recognized for this state. Community Phase 6.1 represents natural colonization of tree and shrub species without management. Community Phase 6.2 is representative of intentional forest establishment by artificial regeneration or planting.
For Community Phase 6.2, determining the objectives and goals of the future stand is imperative to increase the probability of successful establishment and production of the afforested area. These decisions will ultimately determine the species to be established, preparation requirements, planting density, and post-planting operations (e.g., competitor control, future improvement cuttings and thinnings, regeneration methods, and overall stand health). Since each area targeted for afforestation may have unique or different land use histories, having a clear understanding of the soil-site conditions is essential. Some areas may necessitate a series of soil improvement actions prior to planting. These actions may include subsoiling or deep plowing to breakup plow pans and fertilizing the targeted area. An additional option is to allow the area to undergo fallowing for a predetermined period (Community Phase 6.1) to potentially increase soil organic matter content, enhance soil aggregate stability, increase soil biological activity, and improve water holding capacity and infiltration rates. Controlling competing vegetation (chemical and mechanical treatment) will most likely be critical. Post-planting operations and maintenance of the stand can enhance survival, future development, and achieve goals and objectives (see Gardiner et al., 2002).
Finding the appropriate approach for a given environment necessitates close consultation with trained, experienced, and knowledgeable forestry professionals. If there is a desire to proceed with this state, it is strongly urged and advised that professional guidance be obtained and a well-designed afforestation and silvicultural plan developed in advance of any work conducted. For an exceptional review and summarization of the afforestation literature, techniques, and practices within the Southern Mississippi River Alluvium, interested parties are directed to Gardiner et al. (2002).
Community 6.1
Ruderal/Opportunistic Regrowth
This community phase is representative of former working lands (e.g., cropland and possibly high concentration areas of former pastureland) that have fallowed and subsequently undergone natural colonization by vegetation. Depending on location, a profusion of growth may initiate within five to ten years of becoming idle – one that typically includes grasses, forbs, woody seedlings and shrubs, and an increasing presence and covering of vines. Initial colonization may be dominant in annuals followed by a shift to perennial vegetation. Shrubs and tree seedlings may appear very early following abandonment, however the rate of colonization and period to stand establishment likely depends on the proximity of established mature stands (Battaglia et al., 1995; Battaglia et al., 2002). If established stands consisting of light-seeded species adjoin fallow fields, colonizing tree species will likely be comprised of those taxa (e.g., elm, sycamore, and cottonwood) (Allen, 1990; Stanturf et al., 2001). Some areas may be far removed from established forest stands. Under this scenario, establishment of woody species (especially overstory tree species) may be very slow, and years may be required before stand establishment is reached (Battaglia et al., 1995; Allen, 1997). In fact, natural colonization by some species may be delayed indefinitely with some stands or areas being understocked (Allen, 1997; Battaglia et al., 2002; Groninger, 2005). Heavy-seeded species like pecan or oaks may not have an opportunity to colonize available areas due to distance and lack of a dependable dispersing agent (e.g., wildlife and water). Non-native invasive species may become part of the developing stand given the proliferation of exotic plant species over the past century.
It is extremely difficult, if not impossible, to predict the future composition and structure of an abandoned field on this site. Many different environmental factors will influence initial colonization and development trajectories. The following projections are simply based on native plant species reported to occur on the soils of this site. As the young stand matures and eventually enters the stem exclusion stage (crown or canopy closure), eastern cottonwood or black willow may be the dominant species if the stand began on bare mineral soils. Otherwise, the developing stand may be largely comprised of associates of the riverfront hardwoods including American sycamore, American elm, sugarberry, green ash, sweetgum, silver maple, boxelder, and eastern cottonwood as a secondary component. Problematic non-native species that may occur include Japanese honeysuckle (Lonicera japonica), Chinese privet (Ligustrum sinense), Chinese tallow (Triadica sebifera), and possibly Callery pear (Pyrus calleryana). Vines in the young, developing stand may include greenbrier (Smilax spp.), eastern poison ivy, trumpet creeper, grape, Virginia creeper, peppervine, and American buckwheat vine. As the stand matures decades into the future and the overstory stratifies (i.e., the understory reinitiation stage), shade tolerant species may dominate the stand.
Dominant plant species
-
American sycamore (Platanus occidentalis), tree
-
American elm (Ulmus americana), tree
-
green ash (Fraxinus pennsylvanica), tree
-
sugarberry (Celtis laevigata), tree
-
boxelder (Acer negundo), tree
-
silver maple (Acer saccharinum), tree
-
sweetgum (Liquidambar styraciflua), tree
-
eastern cottonwood (Populus deltoides), tree
-
greenbrier (Smilax), shrub
-
eastern poison ivy (Toxicodendron radicans), shrub
-
peppervine (Nekemias arborea), shrub
-
American buckwheat vine (Brunnichia ovata), shrub
-
trumpet creeper (Campsis radicans), shrub
-
Virginia creeper (Parthenocissus quinquefolia), shrub
Community 6.2
Afforestation
This community phase is representative of areas planted in tree species that are suited for and favored in management on this ecological site. Preparation of this phase may be initiated immediately following a former landuse activity (e.g., State 3) or it may be started following a fallow period (Community Phase 6.1). If afforestation is initiated immediately following years of conventional tillage without soil-site preparation and improvement efforts, potential productivity of the targeted area could be less than optimal (Baker and Broadfoot, 1979; Groninger et al., 1999; Gardiner et al., 2002).
Groninger et al. (1999) utilized the Baker and Broadfoot (1979) model for site evaluation to predict potential productivity of green ash, Nuttall oak, American sycamore, sweetgum, swamp chestnut oak, water oak, and cottonwood on what they termed “marginal soybean lands.” These are croplands occurring on frequently flooded areas that typically produce low soybean yields under conventional tillage. Soils associated with these areas are generally poorly drained, clayey, and typically classified as hydric. Two of the principal soil series of this site, Newellton and Tunica soils, were included for evaluation. Based on information presented in Groninger et al. (1999), site index predictions on Newellton soils that had undergone extensive conventional tillage ranged 5 to 20 percent lower than what are generally reported in soil survey manuscripts for eastern cottonwood, green ash, Nuttall oak, sweetgum, and water oak. The estimated site index values for those species were listed as 80, 77, 61, 81, and 72 for cottonwood, green ash, Nuttall oak, sweetgum, and water oak, respectively. The same site index predictions on Tunica soils indicated a 17 to 19 percent reduction for eastern cottonwood and sweetgum, respectively. Estimated site index values on Tunica soils were 75 for eastern cottonwood and 73 for green ash. Comparing the Baker and Broadfoot (1979) estimated site index values of former conventional tilled cropland to the site index values generated from long established forestland are noteworthy (see Community Phase 1.1 for Tunica soils). The site index predictions in Groninger et al. assumes that no soil-site improvement actions were undertaken. (Note that site index is the height in feet of select tree species at 50 years of growth except for eastern cottonwood which is height in 30 years of growth.)
Over the years, various afforestation innovations have increased the likelihood of success in addition to soil-site amelioration such as planting large, high-quality seedlings with well-developed root systems in an appropriate cover crop (Dey et al., 2010); interplanting seedlings within a fast-growing pioneer species nurse crop (e.g., cottonwood) (Gardiner et al., 2001); and planting companionable species combinations for mixed species stands (Lockhart et al., 2008). The cover crop and nurse crop approaches reportedly help to control rapid overtopping and crowding by competing vegetation and wildlife herbivory (Dey et al., 2010). A completely different approach must be taken if eastern cottonwood is the sole targeted species for planting. For eastern cottonwood, all potential competitors must be removed and the soil surface scarified via mechanical site preparation (Johnson and Shropshire, 1983; Hodges, 1995; Meadows and Stanturf, 1997). Finding the appropriate strategy for a given location requires matching the species to the local hydrologic and soil-site environment; determining short- and long-term objectives and goals; and implementing the appropriate management actions at the required intervals.
Several species that frequently occur and are favored in management are likely appropriate for planting on this ecological site. Broadfoot (1976) listed sweetgum, Nuttall oak, green ash, eastern cottonwood, and American sycamore as species suitable for planting. He also listed cherrybark oak, water oak, and willow oak as species to favor in management. The desirability and importance for establishing oaks have prompted many to attempt plantings on sites that were not conducive to oak production. Some of these former attempts likely targeted high pH soils (i.e., nonacid or alkaline) or species selections that were site incompatible (Mike Oliver, personal communication). Broadfoot warned against planting oaks on locations where soil reactions are pH 7.5 or higher. If oaks are planted on this site, intensive plant competition will likely dictate the need for scheduled competitor control efforts that cannot be delayed or postponed. If cherrybark oak is chosen to be planted, then targeted locations should be better drained than low-lying areas that remain wet for long periods, and even then, productivity may be lower than anticipated.
Pathway 6.1A
Community 6.1 to 6.2
Remove undesirable competitors; final soil preparation; establish site-appropriate species (favored in management and suitable for planting).
State 7
Conservation (Herbaceous)
This state is representative of the range of conservation actions that may be implemented and established on this ecological site. Apart from planting trees and managing for forest, one may elect to establish native herbaceous species and manage for predominantly a native grassland; a complex mixture of native grasses and forbs; or a pollinator planting whereby native forbs dominate the mix. In each of these options, it is strongly advised (possibly a programmatic requirement) that the species comprising the planting or seed mix consist of spring, summer, and fall flowering species. Depending on goals and objectives, various conservation programs and practices may be available. For additional information and assistance, please contact or visit the local NRCS Field Office.
Community 7.1
Pollinator Planting/Native Grasses
This community phase represents the establishment of native forbs or wildflowers for pollinator habitat or native grasses. The seed mix for planting may be quite varied depending on objectives and goals. Ideally, the mix includes a wide range of species that flower at various times of the growing season (spring, summer, and fall). Plant species in some pollinator mixes may include but are not limited to beebalm (Monarda spp.), milkweeds (Asclepias spp.), beardtongue (Penstemon spp.), vervain (Verbena spp.), various legumes such as native lespedeza (Lespedeza spp.), Illinois bundleflower (Desmanthus illinoensis), partridge pea (Chamaecrista fasciculata), and a broad assortment of composites such as asters (Symphyotrichum spp.), tickseed (Coreopsis spp.), blazing star (Liatris spp.), coneflower (Rudbeckia spp.), sunflower (Helianthus spp.) among many others. If goals and objectives are to establish native grasses within a forb mix or in a grass-dominant stand, species suitable for planting may include switchgrass (Panicum virgatum), eastern gamagrass (Tripsacum dactyloides), big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium) and Indiangrass (Sorghastrum nutans). Of caution, if eastern gamagrass is chosen to be planted, soil pH must be below 8.0 as the species’ productivity falters under alkaline conditions (Henson, 2012).
Key to the establishment of this phase is initial preparation, seeding rate, planting period, follow-up treatment, and maintenance of the planting. The selection of species to establish on any given area may ultimately depend on size and conditions of the location where the planting will occur, landowner/manager goals and objectives, and the advice and knowledge of the conservation practitioner.
Transition T1A
State 1 to 2
Stand composition is heavily altered and managed to favor select species for production (Community Phase 2.1). This transitional pathway also includes heavy timber cutting and/or repeated partial harvests (high-grading) leading to Community Phase 2.2.
Transition T1B
State 1 to 3
Actions include mechanical removal of vegetation and stumps; herbicide treatment of residual plants; and preparation for cultivation.
Transition T1C
State 1 to 5
Actions include mechanical removal of vegetation and stumps; herbicide treatment of residual plants; seedbed preparation; and establishment of desired forage.
Transition T2A
State 2 to 1
This transition represents a return to perceived reference conditions and involves the reestablishment of missing species; the control or removal of exotic species (herbicide and mechanical); stand improvement practices that favors a return of more shade intolerant components.
Transition T2B
State 2 to 3
Actions include mechanical removal of vegetation and stumps; herbicide treatment of residual plants; and preparation for cultivation.
Transition T2C
State 2 to 5
Actions include mechanical removal of vegetation and stumps; herbicide treatment of residual plants; seedbed preparation; and establishment of desired forage.
Transition T3A
State 3 to 4
Precision land leveling
Transition T3B
State 3 to 5
Vegetation/stump removal (mechanical/chemical); seedbed preparation; establishment of desired forage; manage for grazing.
Transition T3C
State 3 to 6
Natural succession (Community 6.1) or prep area (plow pan breakup, fertilizing, etc.); planting species appropriate for site (Community 6.2).
Transition T3D
State 3 to 7
Establish select native species suitable for site; prep area for planting (herbicide and/or mechanical).
Transition T5A
State 5 to 3
Actions include mechanical removal of vegetation; herbicide treatment of residual plants; and preparation for cultivation.
Transition T5B
State 5 to 6
Natural succession (Community 6.1) or prepare area (e.g., plow pan breakup, fertilizing, etc.) for planting tree species appropriate for site (Afforestation - Community 6.2).
Transition T5C
State 5 to 7
Establish select native species suitable for site and prepare area for planting (herbicide and/or mechanical).
Transition T6A
State 6 to 3
Cropland establishment: vegetation removal (mechanical/chemical) and preparation for cultivation.
Transition T6B
State 6 to 5
Mechanical removal of vegetation and stumps; herbicide treatment of residual plants; establish desired forage species and manage for grazing.
Transition T7A
State 7 to 3
Cropland establishment: vegetation removal (mechanical/chemical) and preparation for cultivation.
Transition T7B
State 7 to 5
Establish desired forage species and manage for grazing.
Transition T7C
State 7 to 6
Natural succession (Community 6.1) or prepare area (e.g., plow pan breakup, fertilizing, etc.) for planting tree species appropriate for site (Afforestation - Community 6.2).
