Ecological dynamics
The information in this Ecological Site Description, including the state-and-transition model (STM), was developed based on historical data, current field data, professional experience, and a review of the scientific literature. As a result, all possible scenarios or plant species may not be included. Key indicator plant species, disturbances, and ecological processes are described to inform land management decisions.
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 are able to support prairies, savannas, woodlands, and forests. Ponded Organic Floodplain Shrub Swamps form an aspect of this vegetative continuum. This ecological site occurs on floodplains on very poorly-drained organic soils. Species characteristic of this ecological site consist of hydrophytic shrubs and herbaceous vegetation.
Ponding is the dominant disturbance factor in Ponded Organic Floodplain Shrub Swamps. The depth and duration of ponded water affects species diversity, composition, and productivity. Shallow ponding allows more of a sedge meadow community to dominate while deeper water depths create a shrub swamp structure, often dominated by common buttonbush.
Drought and infrequent fire also play 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 slow the growth of plants and result in dieback of certain species. When coupled with fire, periods of drought can eliminate or greatly reduce the occurrence of woody vegetation, substantially altering the extent of shrubs and trees (Pyne et al. 1996).
Today, Ponded Organic Floodplain Shrub Swamps have been reduced from their historic extent. Some sites have been drained and converted to cropland or have been mined for their peat. Remnants that do exist show evidence of indirect anthropogenic influences from hydrological alterations as non-native species have replaced the natural vegetation. A return to the historic plant community may not be possible due to significant hydrologic and water quality changes in the watershed, but long-term conservation agriculture or habitat reconstruction efforts can help to restore some natural diversity and ecological function. 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 shrub swamp community, dominated by hydrophytic woody and herbaceous vegetation. The two community phases within the reference state are dependent on ponding. The depth and duration of ponded water alters species composition, cover, and extent. Drought and infrequent fire have more localized impacts in the reference phases, but do contribute to overall species composition, diversity, cover, and productivity.
Community 1.1
Common Buttonbush/Hairy Sedge – Common Duckweed
Sites in this reference community phase are dominated by hydrophytic woody vegetation and ponded water up to 6 feet deep. Common buttonbush is the dominant shrub, comprising nearly 90 percent of the shrub layer. Shrub cover range from 20 to 80 percent cover. Hairy sedge can be found in the shallower ponded areas, while common duckweed occupies deeper areas (NatureServe 2015). Characteristic forbs can include halberdleaf rosemallow (Hibiscus laevis All.), broadleaf cattail (Typha latifolia L.), and smallspike false nettle (Boehmeria cylindrica (L.) Sw.) (Eilers and Roosa 2014; NatureServe 2015). A highly scattered tree canopy may be present including silver maple (Acer saccharinum L.), green ash (Fraxinus pennsylvanica Marshall), and American elm (Ulmus americana L.) (NatureServe 2015). Prolonged, deep ponding will maintain this phase, but a reduced water level (below 1 foot) will shift the community to phase 1.2.
Community 1.2
False Wild Indigo – Meadow Willow/Hairy Sedge – Blue Skullcap
This reference community phase can occur when the frequency and depth of ponding are reduced to less than 1 foot. Hairy sedge becomes more prominent, and herbaceous species diversity increases to include such forbs and grasses as blue skullcap (Scutellaria lateriflora L.), swamp milkweed (Asclepias incarnata L.), bluejoint (Calamagrostis canadensis (Michx.) P. Beauv.), rice cutgrass (Leersia oryzoides (L.) Sw.), and sensitive fern (Onoclea sensibilis L.). Common buttonbush may still be present, but other shrubs less tolerant of prolonged inundation dominate including false wild indigo (Amorpha fruticosa L.), silky dogwood, black willow, and meadow willow. Shallow ponded water depths (less than 1 foot) will maintain this phase, but an increase can shift the community back to phase 1.1.
Pathway 1.1A
Community 1.1 to 1.2
Ponded water depths decrease to <12 inches.
Pathway 1.2A
Community 1.2 to 1.1
Ponded water depths increase to >12 inches.
State 2
Degraded Shrub Swamp
Hydrology is the most important determinant of wetlands and wetland processes. Hydrology modifies and determines the physiochemical environment (i.e., sediments, soil chemistry, water chemistry) which in turn directly affects the vegetation, animals, and microbes (Mitsch and Gosselink 2007). Human activities on landscape hydrology have greatly altered Ponded Organic Floodplain Shrub Swamps. Alterations such as agricultural tile draining and conversion to cropland on adjacent lands in addition to stream channelization and damming have changed the natural hydroperiod and rate of sedimentation as well as increased nutrient pollution (Mitsch and Gosselink 2007). Long-term fire suppression has also allowed unnatural succession and dominance by floodplain trees.
Community 2.1
Silver Maple – Green Ash/Common Buttonbush/Reed Canarygrass
This community phase represents the changes to the natural wetland hydroperiod, increasing sedimentation, unabated nutrient runoff, and long-term fire suppression. The tree canopy cover increases from scattered individuals to dominance by species such as silver maple and green ash. Common buttonbush is still present in the shrub canopy, but the landscape alterations provide suitable conditions for invasion by non-native species such as reed canarygrass (Phalaris arundinacea L.) and purple loosestrife (Lythrum salicaria L.).
State 3
Forage State
The forage state arises when the site is converted to a farming system that emphasizes domestic livestock production, known as grassland agriculture. Tree removal, 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 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, disturbance-tolerant species.
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 corn-soybean rotations. 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, crop rotation 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, and crop rotation is reduced or eliminated.
Pathway 4.3A
Community 4.3 to 4.2
Cover crop practices are abandoned.
State 5
Reconstructed Shrub Swamp State
Shrub swamp habitats provide multiple ecosystem services including flood abatement, water quality improvement, and biodiversity support (Mitsch and Gosselink 2007). However, many swamp communities have been eliminated as a result of type conversions to agricultural production, changes to the natural hydrologic regime, and invasion of non-native species, thereby significantly reducing these services (Annen et al. 2008). The extensive alterations of lands adjacent to Ponded Organic Floodplain Shrub Swamps or the depletion of the historic organic soils may not allow for restoration back to the historic reference condition. But ecological reconstruction can aim to aid the recovery of degraded, damaged, or destroyed functions. A successful reconstruction will have the ability to structurally and functionally sustain itself, demonstrate resilience to the natural ranges of stress and disturbance, and create and maintain positive biotic and abiotic interactions (SER 2002; Mitsch and Jørgensen 2004).
Community 5.1
Early Successional Reconstructed Shrub Swamp
This community phase represents the early community assembly from shrub swamp habitat reconstruction and is highly dependent on invasive species control, hydroperiod repair, and planting (Adams and Galatowitsch 2006). In addition, adaptive restoration tactics that incorporate multiple restoration methods should be implemented in order to more clearly identify cause-effect relationships of vegetative development (Zedler 2005).
Community 5.2
Late Successional Reconstructed Shrub Swamp
Appropriately timed disturbance regimes (e.g. hydroperiod, invasive species control) and nutrient management applied to the early successional community phase can help increase the species richness and improve ecosystem function, pushing the site into a late successional community phase over time (Mitsch and Gosselink 2007).
Pathway 5.1A
Community 5.1 to 5.2
Maintenance of proper hydrology and nutrient balances in line with a developed wetland management plant.
Pathway 5.2A –
Community 5.2 to 5.1
Reconstruction experiences a setback from extreme weather event or improper timing of management actions.
Transition T1A
State 1 to 2
Hydrological alterations and long-term fire suppression transition the site to the degraded shrub swamp state (2).
Transition T1B
State 1 to 3
Cultural treatments to enhance forage quality and yield transitions this site to the forage state (3).
Transition T1C
State 1 to 4
Installation of drain tiles, tillage, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
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, tillage, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Restoration pathway R2A
State 2 to 5
Hydroperiod restoration, site preparation, non-native species control, and seeding native species transition the site to the reconstructed shrub swamp state (5).
Transition T3A
State 3 to 2
Land abandonment transitions the site to the degraded shrub swamp (2).
Transition T3B
State 3 to 4
Installation of drain tiles, tillage, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Restoration pathway R3A
State 3 to 5
Site preparation, tree planting, invasive species control, and seeding native species transition this site to the reconstructed shrub swamp state (5).
Transition T4A
State 4 to 2
Land abandonment transitions the site to the degraded shrub swamp state (2).
Transition T4B
State 4 to 3
Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
Restoration pathway R4A
State 4 to 5
Site preparation, tree planting, invasive species control, and seeding native species transition this site to the reconstructed shrub swamp state (5).
Transition T5A
State 5 to 2
Fire suppression and removal of active management transitions this site to the degraded shrub swamp state (2).
Transition T5B
State 5 to 3
Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
Transition T5C
State 5 to 4
Tillage, seeding of agricultural crops, and non-selective herbicide transition this site to the cropland state (4).
