Ecological dynamics
The core concepts of this site are drawn from occurrences situated on ancient, loess-capped fluvial terraces that are above the active floodplain (i.e., the 100-year flood zone). This site is also mapped on level to nearly level toeslopes and/or valley bottoms. Slope gradients vary but rarely do they extend beyond 8 percent; dominant slopes range from 2 to 5 percent.
The fertile, well drained soils of this site occur on higher elevations and landforms of an otherwise level to nearly level landscape. Landforms represented are generally classed as “rises” on terrace treads. The higher physiographic features of this site coupled with soil fertility create suitable conditions for supporting a rich and varied plant community.
The pre-settlement plant community of this ecological site was removed more than a century ago, and there are no extant examples of those systems remaining. It is plausible that various vegetation types and management conditions existed on this site prior to settlement. Broad, level landscapes situated beside active floodplains would have presented exemplary conditions for habitation. Areas that supported human populations would have exerted tremendous influences on the composition and structure of local plant communities. Food, clothing, building, and cultural materials needed for subsistence were cultivated, harvested, and gathered from surrounding environments. Favored mast and fruit producing trees, in addition to numerous shrubs, vines, and herbs, were selectively produced and managed (Delcourt and Delcourt, 2004). Fire was a critical tool for managing these areas, especially in keeping vegetation regrowth in check. This complex backdrop of human subsistence and influences on the surrounding landscape must have contributed to a “shifting mosaic” of biological communities as human populations moved about, increased, and waned. Plant communities associated with this site likely consisted of deep forest to open woodland to fire-maintained prairies.
Today, nearly the entire distribution of this site has been cleared and is under some form of agriculture production. Minor uses of this site include forest production or timberland and a few localities are in pasture and/or forage production.
Determining and ascribing reference conditions for this site is very challenging. With no example of the pre-settlement plant community remaining (which was likely a mosaic of prairie, woodland, and forest), reference conditions of this site are arbitrarily chosen to reflect the existing plant community that remains on a protected refuge. Those sites support a rich, moist (i.e., mesic) hardwood forest that resembles the composition of two major plant communities: 1) bottomland hardwoods on well-drained positions of active floodplains and 2) the rich, mixed hardwood community of the Loess Hills. Older forests occurring on this site are structurally complex and predominantly comprised of tall hardwoods with overlapping canopies. Loblolly pine may be an additional component of the community farther south.
In addition to the reference state, four alternate states are indicated to represent the range of conditions associated with this site. One of those states, Conservation, is provided to illustrate a conservation alternative to the more intensive management activities on this site. That state involves a discontinuation of production and the alternative to establish native vegetation, whether the establishment is predominantly of woodland or an herbaceous community comprised of native grasses and forbs.
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 the Northern Loess Terrace ecological site. This model is based on limited reconnaissance, literature, expert knowledge, and interpretations. Plant communities will differ due to natural variability in soils and physiography. 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
Mesic Hardwood Forest
The reference conditions of this ecological site are chosen to represent the prevailing characteristics of stands that have been protected from human-induced manipulations and impacts for at least 50 years. Species observed within these stands consists of a mixed hardwood forest with a number of mesophytes as components of the community. Descriptions and detailed studies of these systems are virtually absent in the literature.
From a structural perspective, this site may have supported a mosaic of conditions that included closed forests, open woodlands, and meadows or small prairies either occurring along the fringes or within the site proper. A single community phase is provided to represent current conditions of protected stands, which is a closed canopy, structurally complex forest. Additional reference community phases may be included in subsequent iterations of this ecological site description if warranted.
Community 1.1
Mixed Hardwood – Oak Forest
Canopy species associated with this site include tuliptree, American beech, sweetgum, sugar maple, Shumard’s oak, white oak, cherrybark oak, mockernut hickory, bitternut hickory, black walnut, American elm, and ash. To the south in Mississippi, loblolly pine is a component of the community. The subcanopy or mid-story stratum is represented by smaller canopy species along with hophornbeam, pawpaw, and American hornbeam. Vegetation characteristic of the small to tall shrub strata include pawpaw, spicebush, and red buckeye. The ground layer stratum supports a broad array of herbaceous and woody vine species including broad beech fern, Christmas fern, mayapple, wild comfrey, and several species of grasses and sedges.
State 2
Agriculture Production
Agriculture production is the dominant land use activity on this site, today. Most cropland is relegated to the uplands and broad terraces of the Loess Plains within MLRA 134.
Community 2.1
Cropland
Crops commonly grown include soybean, corn, wheat, and cotton.
State 3
Pastureland/Hayland
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.
Community 3.1
Select Forage/Species Mixture
This community phase represents commonly planted forage species on pasturelands and haylands. The suite of plants established on any given site may vary considerably depending upon purpose, management goals, usage, and soils. Most systems include a mixture of grasses and legumes that provide forage throughout the growing season. Cool season forage may include tall fescue (Schedonorus arundinaceus), orchardgrass (Dactylis glomerata), white clover (Trifolium repens), and red clover (T. pratense), and warm season forage often consists of bermudagrass (Cynodon dactylon), bahiagrass (Paspalum notatum), and annual lespedeza (Kummerowia spp.). Several additional plants and/or species combinations may be desired depending on the objectives and management approaches and especially, local soils.
Should active management (and grazing) of the pastureland be halted, this phase will transition to “old field” conditions, which is the transitional period between a predominantly open, herbaceous field and the brushy stage of a newly initiated stand of trees.
State 4
Timber Management
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. 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.
Community 4.1
Mixed Oak – Pine (Various)
Some of the most desirable timber on this site consists of oak. Depending on the desired end product, management activities will differ. Management for oak dominant stands may be achieved by shelterwood and/or seed tree approaches. Managing for other hardwoods, and pine to the south, may only require timber stand improvement methods or artificial regeneration may be called for where other hardwoods predominate. Of caution, the fertile soils of this site make managing for oak-dominated stands very difficult due to competition from other hardwoods such as sweetgum, ash, elm, and especially tuliptree. Similar competition challenges exist for pine-dominated stands as well. Pine management may be best relegated to southern portions of this site.
Finding the appropriate approach for a given stand and environment necessitates close consultation with trained, experienced, and knowledgeable forestry professionals. It is strongly urged and advised that professional guidance be secured and a well-designed silvicultural plan developed in advance of any work conducted.
State 5
Conservation
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.
Community 5.1
Native Herbaceous or Woodland
This community phase represents the establishment of select native plants to meet conservation objectives on this site. As alluded to above, the best case scenario is the establishment of native species selected from the genetic stock of the Loess Plains or neighboring ecoregions. Herbaceous species suitable for establishing on this site include big bluestem, Indian grass, little bluestem, threeawn, wild oat grasses, panic grass, wild indigo, blazing stars, evening-primrose, asters, black-eyed susans, compass plant, coneflowers, goldenrod, lanceleaf tickseed, tall tickseed, rattlesnake master, sunflowers, flowering spurge, Virginia strawberry, purple milkwort, slender milkwort, Sampson’s snakeroot, mountain mints, agave, New Jersey tea, goat’s-rue, various milkweeds, sedges, among many others (partially derived from Heineke, 1987 and D. Estes). Key to the perpetuation and maintenance of this system is frequent fire, generally on a 1 to 3 year return interval (judgement based on early accounts of frequent burning; e.g., Loughridge, 1888). Although, LANDFIRE (2009) models suggest replacement or surface fire every 10 years maintains the early development characteristics of this system.
Transition T1A
State 1 to 2
Actions include mechanical removal of vegetation and stumps; preparation for and establishment of cultivation (State 2).
Transition T1B
State 1 to 3
This pathway represents an attempt to convert the woodland community to pasture or forage production. Actions include clearing, stump removal, seedbed preparation, and the establishment of desired plants (State 3).
Transition T1C
State 1 to 4
This pathway consists of prescribed silvicultural activities specifically designed to meet stand compositional and production objectives.
Restoration pathway R2A
State 2 to 1
This pathway represents natural succession back to perceived reference conditions. The period required for this transition to take place likely varies by location and is dependent upon local site conditions and the intensity of former land use impacts. LANDFIRE models (2009) suggest that over 80 years is required for a return to a late development community and this pathway is highly dependent upon species present in the developing stand and former disturbances. Significant efforts may be required before a return to reference conditions is achieved (e.g., exotic species control, potential artificial regeneration of community components, etc.).
Transition T2A
State 2 to 3
Seedbed preparation and establishment of desired forage/grassland mixture.
Transition T2B
State 2 to 4
This pathway represents prescribed management strategies for transitioning former cropland and/or cutover woodland to one that meets timber stand composition and production objectives. For enhanced oak production, actions may include artificial regeneration and reduction of oak competition. Managing for mixed hardwood production may require exotic species control and general timber stand improvement practices. The final option of this pathway is the establishment of a pine monoculture or plantation. Establishment of the latter may be most successful on thin loess soils and/or in the southern portions of this site.
Transition T2C
State 2 to 5
This pathway represents the decision to discontinue cultivation/production and establish native grasses/forbs or trees on this site. This action also includes management activities to “guide” natural succession and conservation maintenance. Actions may include prescribed fire for maintaining and enhancing herbaceous establishment and herbicide treatments for controlling exotic species invasions and to ensure select tree establishment.
Restoration pathway R3A
State 3 to 1
This pathway represents natural succession back to perceived reference conditions. The period required for this transition to take place likely varies by location and is dependent upon local site conditions and the intensity of former land use impacts. LANDFIRE models (2009) suggest that over 80 years is required for a return to a late development community and this pathway is highly dependent upon species present in the developing stand and former disturbances. Significant efforts may be required before a return to reference conditions is achieved (e.g., exotic species control, appropriate intensity and return interval of fire, potential artificial regeneration of community components, etc.).
Transition T3A
State 3 to 2
Actions include removal of vegetation; herbicide treatment of residual plants; and preparation for cultivation.
Transition T3B
State 3 to 4
This pathway represents natural succession of former pasture to non-managed “woods” or forest or implementing prescribed management strategies for meeting timber stand composition and production objectives. For enhanced oak production, actions may include artificial regeneration and reduction of oak competition. Managing for mixed hardwood production may require exotic species control and general timber stand improvement practices. The final option of this pathway is the establishment of a pine monoculture or plantation. Establishment of the latter may be most successful on thin loess soils and/or in the southern portions of the site.
Transition T3C
State 3 to 5
This pathway represents the decision to discontinue grazing/non-native forage management and establish native grasses/forbs or trees on this site. This action also includes management activities to “guide” natural succession. Actions may include prescribed fire for maintaining and enhancing herbaceous establishment and herbicide treatments for controlling exotic species invasions and to ensure select tree establishment.
Restoration pathway R4A
State 4 to 1
Natural succession over a period of time may transition a former timber-managed stand to one supporting reference conditions. Based on observations of some reference stands, a period greater than 50 years may be required, unless it was a former pine monoculture. Some question remains whether a return to reference conditions will occur in every situation, especially since some components may have been selectively culled from the stand. Management activities to aide recovery may include exotic species control and silvicultural treatment.
Transition T4A
State 4 to 2
Actions include removal of vegetation; herbicide treatment of residual plants; and preparation for cultivation.
Transition T4B
State 4 to 3
Seedbed preparation and establishment of desired forage/grassland mixture.
Transition T4C
State 4 to 5
This pathway represents the decision to discontinue timber management and establish native grasses/forbs on this site. This decision also includes the implementation of management activities to “guide” natural succession and conservation end goals. Actions may include prescribed fire for maintaining and enhancing herbaceous establishment and herbicide treatments for controlling exotic species invasions.
Restoration pathway R5A
State 5 to 1
This pathway represents natural succession back to perceived reference conditions. The period required for this transition to take place likely varies by location and is dependent upon local site conditions and the intensity of former land use impacts. LANDFIRE models (2009) suggest that over 80 years is required for a return to a late development community and this pathway is highly dependent upon species present in the developing stand and former disturbances. Significant efforts may be required before a return to reference conditions is achieved (e.g., exotic species control, appropriate intensity and return interval of fire, potential artificial regeneration of community components, etc.).
Transition T5A
State 5 to 2
This pathway represents the discontinuation of conservation practices and a return to production.
Transition T5B
State 5 to 3
This pathway represents the discontinuation of conservation practices and a return to pasture and/or hayland management entailing removal of vegetation, seedbed preparation, and establishment of desired forage/grassland mixture.
Transition T5C
State 5 to 4
This pathway represents the discontinuation of conservation practices and establishing prescribed management strategies for timber stand composition and production objectives. For enhanced oak production, actions may include artificial regeneration and reduction of oak competition. Managing for mixed hardwood production may require exotic species control and general timber stand improvement practices. The final option of this pathway is the establishment of a pine monoculture or plantation. Establishment of the latter may be most successful on thin loess soils and/or in the southern portions of the site.
