Ecological dynamics
The MLRA lies within the transition zone between the eastern deciduous forests and the tallgrass prairies. The heterogeneous topography of the area results in variable microclimates and fuel matrices that in turn support prairies, savannas, woodlands, and forests. Organic Sedge Meadow form an aspect of this vegetative continuum. This ecological site occurs on upland backslopes on very poorly-drained organic soils. A shallow water table results in saturated soil conditions throughout the year. Species characteristic of this ecological site consist of hydrophytic herbaceous vegetation.
Organic Sedge Meadows are dependent on consistent groundwater discharge. These conditions are present where surface slopes intersect a perched water table, allowing the groundwater to slowly seep from the hillside (Richardson and Brinson 2001; Dixon 2014). While water levels may fluctuate throughout the year, they generally remain at or near the soil surface (LANDFIRE 2009). The near-constant anaerobic conditions maintain the herbaceous wetland plant community and prevent woody species from encroaching.
Drought and fire have also played a role in shaping this ecological site. The periodic episodes of reduced soil moisture in conjunction with the very poorly-drained soils have favored the proliferation of plant species tolerant of such conditions. Drought can also slow the growth of plants and result in dieback of certain species. Occasional fires reduced plant litter and aided in preventing declines in species richness. Drought coupled with fire would keep woody plants from encroaching (LANDFIRE 2009).
Today, Organic Sedge Meadows have been greatly reduced as sites have been converted to agricultural production lands or converted to ponds. Sites that have not been directly altered show evidence of indirect anthropogenic influences from hydrologic alterations, fire suppression, and non-native species invasion (Pearson and Leoschke 1992). These land conversions and alterations to the natural groundwater flow are considered irreversible, making restoration an improbability. The state-and-transition model that follows provides a detailed description of each state, community phase, pathway, and transition. This model is based on available experimental research, field observations, literature reviews, professional consensus, and interpretations.
State 1
Reference State
The reference plant community is categorized as a groundwater-fed slope wetland community, dominated by hydrophytic herbaceous vegetation. The one community phase within the reference state is dependent on consistent groundwater seepage to maintain the plant community. Drought and occasional fires have more localized impacts in the reference state, but do contribute to overall species composition, diversity, cover, and productivity.
Community 1.1
Upright Sedge – Eastern Marsh Fern
Sites in this reference community phase are dominated by hydrophytic herbaceous vegetation. Upright sedge and eastern marsh fern are dominant species on the site, but other frequently encountered ones include bluejoint, spiked muhly, and sensitive fern (Onoclea sensibilis L.). Forb species richness is often very high in these unique communities and typically includes many species with high conservative values, e.g. yellow marsh marigold, fen grass of Parnassus, tobacco root, and marsh bellflower (Campanula aparinoides Pursh).
State 2
Degraded Woody-invaded State
The expansion of ruderal woody and herbaceous species into Organic Sedge Meadows can arise due to a complex interaction of fire suppression, hydrological alterations, and edge effects. Subsurface water reduction from agricultural tiling, ditching, or off-site development in conjunction with the removal of periodic fires allows woody species to encroach, casting shade on the native plant community and altering the natural light regime. In addition, edge effects can arise from indirect land management practices (e.g., cropping, herbicide drift) on directly adjacent sites that lead to a transition in the herbaceous species composition to taller, ruderal species (Pearson and Leoschke 1992; NatureServe 2015).
Community 2.1
Slippery Elm – Silky Dogwood/Great Ragweed – Stinging Nettle
This community phase represents the initial changes to the natural community following hydroperiod alterations and adjacent land management actions. Reduction in the water table allows woody species, such as slippery elm (Ulmus rubra Muhl.), silky dogwood (Cornus obliqua Raf.), and pussy willow (Salix discolor Muhl.), to establish a significant shrub cover. The herbaceous layer shifts to disturbance-tolerant, opportunistic species including great ragweed (Ambrosia trifida L.), stinging nettle (Urtica dioica L.), Canada lettuce (Lactuca canadensis L.), common milkweed (Asclepias syriaca L.), and common evening primrose (Oenothera biennis L.). Non-native invasive species, including reed canarygrass (Phalaris arundinacea L.), redtop (Agrostis gigantea Roth), and Kentucky bluegrass (Poa pratensis L.), begin to encroach as well (Pearson and Leoschke 1992).
Community 2.2
Slippery Elm/Silky Dogwood – Pussy Willow/Great Ragweed – Stinging Nettle
Sites falling into this community phase represent the natural succession as a result of continuing changes to the hydroperiod and adjacent lands. Slippery elm can mature into a tree canopy, and silky dogwood and pussy willow continue to form the dominant shrubs. The herbaceous layer continues to be simplified and inhabited by ruderal and non-native species.
Pathway 2.1A
Community 2.1 to 2.2
Natural succession as a result of continuing landscape changes.
Pathway 2.2A
Community 2.2 to 2.1
Limited woody species removal.
State 3
Forage State
The forage state arises when the site is converted to a farming operation that emphasizes domestic livestock production, known as grassland agriculture. Fire suppression, periodic cultural treatments (e.g., clipping, drainage, soil amendment applications, planting new species and/or cultivars, mechanical harvesting) and grazing by domesticated livestock transition and maintain this state (USDA-NRCS 2003). Early settlers seeded non-native species, such as smooth brome (Bromus inermis Leyss.) and Kentucky bluegrass (Poa pratensis L.), to help extend the grazing season (Smith 1998). Over time, as lands were continuously harvested or grazed by herds of cattle, these species were able to spread and expand across the landscape, reducing the native species diversity and ecological function.
Community 3.1
Hayfield
Sites in this community phase consist of forage plants that are planted and mechanically harvested. Mechanical harvesting removes much of the aboveground biomass and nutrients that feed the soil microorganisms (Franzluebbers et al. 2000; USDA-NRCS 2003). As a result, soil biology is reduced leading to decreases in nutrient uptake by plants, soil organic matter, and soil aggregation. Frequent biomass removal can also reduce the site’s carbon sequestration capacity (Skinner 2008). This phase may not be prevalent on this ecological site due to the high soil moisture making it difficult to run large equipment across it.
Community 3.2
Continuous Pastured Grazing
This community phase is characterized by continuous grazing where domestic livestock are allowed to graze a pasture for the entire season. Depending on stocking density, this can result in lower forage quality and productivity, weed invasions, and uneven pasture use. Continuous grazing can also increase the amount of bare ground and erosion and reduce soil organic matter, cation exchange capacity, water-holding capacity, and nutrient availability and retention (Bharati et al. 2002; Leake et al. 2004; Teague et al. 2011). Smooth brome, Kentucky bluegrass, and white clover (Trifolium repens L.) are common pasture species used in this phase. Their tolerance to continuous grazing has allowed these species to dominate, greatly reducing the native species diversity to only low palatability species such as woolly sedge and sawtooth sunflower (Helianthus grosseserratus M. Martens) (Pearson and Leoschke 1992).
Community 3.3
Periodic-rest Pastured Grazing
This community phase is characterized by periodic-rest grazing where the pasture has been subdivided into several smaller paddocks. Subdividing the pasture in this way allows livestock to utilize one or a few paddocks, while the remaining area is rested allowing plants to restore vigor and energy reserves, deepen root systems, develop seeds, as well as allow seedling establishment (Undersander et al. 2002; USDA-NRCS 2003). Periodic-rest pastured grazing includes deferred periods, rest periods, and periods of high intensity – low frequency, and short duration methods. Vegetation is generally more diverse and can include orchardgrass (Dactylis glomerata L.), timothy (Phleum pretense L.), red clover (Trifolium pratense L.), and alfalfa (Medicago sativa L.). The addition of native prairie species can further bolster plant diversity and, in turn, soil function. This community phase promotes numerous ecosystem benefits including increasing biodiversity, preventing soil erosion, maintaining and enhancing soil quality, sequestering atmospheric carbon, and improving water yield and quality (USDA-NRCS 2003).
Pathway 3.1A
Community 3.1 to 3.2
Mechanical harvesting is replaced with domestic livestock utilizing continuous
grazing.
Pathway 3.1B
Community 3.1 to 3.3
Mechanical harvesting is replaced with domestic livestock utilizing periodic-rest grazing.
Pathway 3.2A
Community 3.2 to 3.1
Domestic livestock are removed, and mechanical harvesting is implemented.
Pathway 3.2B
Community 3.2 to 3.3
Periodic-rest grazing replaces continuous grazing.
Pathway 3.3B
Community 3.3 to 3.1
Domestic livestock are removed, and mechanical harvesting is implemented.
Pathway 3.3A
Community 3.3 to 3.2
Continuous grazing replaces periodic-rest grazing.
State 4
Cropland State
The cropland state is the dominant land condition throughout the MLRA today. Agricultural tile drains used to lower the water table and the continuous use of tillage, row-crop planting, and chemicals (i.e., herbicides, fertilizers, etc.) have effectively eliminated the reference community and many of its natural ecological functions in favor of crop production. Corn and soybeans are the dominant crops for the site, and oats (Avena L.) and alfalfa (Medicago sativa L.) may be rotated periodically. These areas are likely to remain in crop production for the foreseeable future.
Community 4.1
Conventional Tillage Field
Sites in this community phase typically consist of monoculture row-cropping maintained by conventional tillage practices. They are cropped in either continuous corn or alternating periods of corn and soybean crops. The frequent use of deep tillage, low crop diversity, and bare soil conditions during the non-growing season negatively impacts soil health. Under these practices, soil aggregation is reduced or destroyed, soil organic matter is reduced, erosion and runoff are increased, and infiltration is decreased, which can ultimately lead to undesirable changes in the hydrology of the watershed (Tomer et al. 2005).
Community 4.2
Conservation Tillage Field
This community phase is characterized by periodically alternating crops and utilizing various conservation tillage methods to promote soil health and reduce erosion. Conservation tillage methods include strip-till, ridge-till, vertical-till, or no-till planting operations. Strip-till keeps seedbed preparation to narrow bands less than one-third the width of the row where crop residue and soil consolidation are left undisturbed in-between seedbed areas. Strip-till planting may be completed in the fall and nutrient application either occurs simultaneously or at the time of planting. Ridge-till uses specialized equipment to create ridges in the seedbed and vegetative residue is left on the surface in between the ridges. Weeds are controlled with herbicides and/or cultivation, seedbed ridges are rebuilt during cultivation, and soils are left undisturbed from harvest to planting. Vertical-till operations employ machinery that lightly tills the soil and cuts up crop residue, mixing some of the residue into the top few inches of the soil while leaving a large portion on the surface. No-till management is the most conservative, disturbing soils only at the time of planting and fertilizer application. Compared to conventional tillage operations, conservation tillage methods can improve soil ecosystem function by reducing soil erosion, increasing organic matter and water availability, improving water quality, and reducing soil compaction.
Community 4.3
Conservation Tillage with Cover Crop Field
This community phase applies conservation tillage methods as described above as well as adds cover crop practices. Cover crops typically include nitrogen-fixing species (e.g., legumes), small grains (e.g., rye, wheat, oats), or forage covers (e.g., turnips, radishes, rapeseed). The addition of cover crops not only adds plant diversity but also promotes soil health by reducing soil erosion, limiting nitrogen leaching, suppressing weeds, increasing soil organic matter, and improving the overall soil ecosystem. In the case of small grain cover crops, surface cover and water infiltration are increased, while forage covers can be used to graze livestock or support local wildlife. Of the three community phases for this state, this phase promotes the greatest soil sustainability and improves ecological functioning within a row crop operation.
Pathway 4.1A
Community 4.1 to 4.2
Tillage operations are greatly reduced, alternating crops occurs on a regular interval, and crop residue remains on the soil surface.
Pathway 4.1B
Community 4.1 to 4.3
Tillage operations are greatly reduced or eliminated, alternating crops occurs on a regular interval, crop residue remains on the soil surface, and cover crops are planted following crop harvest.
Pathway 4.2A
Community 4.2 to 4.1
Intensive tillage is utilized, and monoculture row-cropping is established.
Pathway 4.2B
Community 4.2 to 4.3
Cover crops are implemented to minimize soil erosion.
Pathway 4.3B
Community 4.3 to 4.1
Intensive tillage is utilized, cover crops practices are abandoned, monoculture
row-cropping is established on a more-or-less continuous basis.
Pathway 4.3A
Community 4.3 to 4.2
Cover crop practices are abandoned.
State 5
Pond State
A small percentage of historic Organic Sedge Meadows in the MLRA have been impounded or excavated for ponds in order to support watering livestock, creating waterfowl habitat, and establishing fisheries (Pearson and Leoschke 1992). Through excavation, the native vegetation is removed, and groundwater seepage can rapidly fill the exposed area and transition the diverse organic sedge meadow into an open water habitat. Over time, sediments may accumulate along the edges of the pond where emergent vegetation, introduced by wind or wildlife, can germinate and establish.
Community 5.1
Cattail – open water
This community phase is characterized mostly by open water. Along the shallow edges of the water, a limited diversity of emergent vegetation may establish. Cattails (Typha L.) and bulrushes (Scirpus L., Bolboschoenus (Asch.) Palla) are the most commonly encountered species.
Transition T1A
State 1 to 2
Changes to the natural hydroperiod and edge effects from adjacent land uses transition this site the degraded woody-invaded state (2).
Transition T1B
State 1 to 3
Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
Transition T1C
State 1 to 4
Installation of drain tiles, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Transition T1D
State 1 to 5
Removal of natural vegetation and excavation transition the site to the pond state (5).
Transition T2A
State 2 to 3
Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
Transition T2B
State 2 to 4
Installation of drain tiles, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Transition T3A
State 3 to 2
Land is abandoned and left fallow; natural succession by opportunistic species transition this site the degraded woody-invaded state (2).
Transition T3B
State 3 to 4
Installation of drain tiles, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Transition T3C
State 3 to 5
Removal of natural vegetation and excavation transition the site to the pond state (5).
Transition T4A
State 4 to 2
Agricultural production abandoned and left fallow; natural succession by opportunistic species transition this site to the degraded woody-invaded state (2).
Transition T4B
State 4 to 3
Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
