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 tallgrass prairie ecosystem of the Midwest, but a variety of environmental and edaphic factors resulted in landscape that historically supported prairies, savannas, forests, and various wetlands. Sand Prairies form an aspect of this vegetative continuum. This ecological site occurs on uplands on well to excessively drained soils. Species characteristic of this ecological site consist of drought-adapted herbaceous vegetation.
Fire is a critical disturbance factor that maintains Dry Sand Prairies. Fire intensity typically consisted of periodic, low-intensity surface fires occurring every 1 to 5 years (LANDFIRE 2009). Ignition sources included summertime lightning strikes from convective storms and bimodal, human ignitions during the spring and fall seasons. Native Americans regularly set fires to improve sight lines for hunting, driving large game, improving grazing and browsing habitat, agricultural clearing, and enhancing vital ethnobotanical plants (Barrett 1980).
Sand blowouts are another disturbance factor that shape this ecological site. The high sand content coupled with increasing slopes allows for localized erosion and shifting from high wind events or following a recent fire. The resulting substrate exposures results in a temporarily reduced vegetative canopy cover, leaving a plant community that resembles a sand barren. Over time site stability increases and the community will shift back to sand prairie (NatureServe 2018).
Drought and grazing by native ungulates have also played a role in shaping this ecological site. The periodic episodes of reduced soil moisture in conjunction with the well to excessively 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. Large mammals, specifically prairie elk (Cervus elaphus), bison (Bos bison), and white-tailed deer (Odocoileus virginianus), likely occurred in low densities resulting in limited impacts to plant composition and dominance (LANDFIRE 2009). When coupled with fire, periods of drought and herbivory can greatly delay the establishment of woody vegetation (Pyne et al. 1996).
Today, Dry Sand Prairies are limited in their extent, having been type-converted to agricultural production land or other human-modified landscapes. Remnants that do exist show evidence of indirect anthropogenic influences from fire suppression and non-native species invasion. A return to the historic plant community may not be possible following extensive land modification, but long-term conservation agriculture or prairie reconstruction efforts can help to restore some biotic 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 prairie community, dominated by herbaceous vegetation. The one community phase within the reference state is dependent on fire and sand blowouts. Short fire return intervals and occasional slope failures alter species composition, cover, and extent, while regular fire intervals keep woody species from dominating. Drought and grazing have more localized impacts on the reference phase, but do contribute to overall species composition, diversity, cover, and productivity.
Community 1.1
Little Bluestem - Tall Blazing Star
Sites in this reference community phase are dominated by a mix of grasses and forbs. Vegetative cover is patchy to continuous (61 to 100 percent) and plants can reach heights greater than 3 feet tall (LANDFIRE 2009). Little bluestem, Indiangrass, porcupinegrass, and big bluestem are the dominant grasses. Characteristic forbs include tall blazing star, flaxleaf whitetop aster, showy goldenrod, birdfoot violet, roundhead lespedeza (Lespedeza capitata Michx), and Carolina puccoon (Lithospermum caroliniense (Walter ex J.G. Gmel.) MacMill.) (NatureServe 2018). Replacement fires every 3 to 4 years or periodic sand blowouts will maintain this phase (LANDFIRE 2009).
State 2
Fire-Suppressed Scrub State
Long-term fire suppression can transition the reference sand prairie community into a woody-invaded shrub-prairie. This state is evidenced by a well-developed shrub layer and sparse trees (LANDFIRE 2009). Proximity to lands that have been altered provide opportunities for non-native species to readily colonize this state, thereby reducing the native biodiversity and changing the vegetative community.
Community 2.1
Eastern Redcedar - Smooth Sumac/Little Bluestem - Smooth Brome
This community phase represents the early stages of long-term fire suppression. In the absence of fire, woody species encroach into the native sand prairie. Shrubs are less than 6 feet tall and can exceed 30 percent cover. Common shrubs likely to be encountered include eastern redcedar (Juniperus virginiana L.) and smooth sumac (Rhus glabra L.). These tall shrubs shade out the understory, reducing the biodiversity. The shade also promotes a moister soil environment, providing suitable condition for invasion by non-native species, such as smooth brome (Bromus inermis L.) (Howard 1996).
Community 2.2
Eastern Redcedar/Smooth Sumac/Little Bluestem - Smooth Brome
Sites falling into this community phase have a well-developed shrub layer, and scattered trees begin to mature as a result of the continued lack of fire. Eastern redcedar continues to grow readily on the dry, nutrient-poor sandy soils, becoming the dominant tree on the site while the clonal smooth sumac continues to expand in the shrub layer (Anderson 2003).
Pathway 2.1A
Community 2.1 to 2.2
Continued fire suppression in excess of 20 years.
Pathway 2.2A
Community 2.2 to 2.1
Single fire event with enough intensity to top-kill trees.
State 3
Anthropogenic State
The anthropogenic state occurs when the reference state is cleared and developed for human use and inhabitation, such as for commercial and housing developments, landfills, parks, golf courses, cemeteries, earthen spoils, etc. The native vegetation has been removed and soils have either been altered in place (e.g. cemeteries) or transported from one location to another (e.g. housing developments). Most of the soils in this state have 50 to 100 cm of overburden on top of the natural soil. This natural material can be determined by observing a buried surface horizon or the unaltered subsoil, till, or lacustrine parent materials. This state is generally considered permanent.
Community 3.1
Human-altered land
Sites in this community phase have had the native plant community removed and soils heavily re-worked in support of human development projects.
State 4
Cropland State
The continuous use of tillage, row-crop planting, and chemicals (i.e., herbicides, fertilizers, etc.) has 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 common wheat (Triticum aestivum 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 rotational crop production that utilizes 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 systems. 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 systems 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 systems, 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 Field/Alternative 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 cropland system.
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, crop rotation 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 crop 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 Sand Prairie State
Prairie reconstructions have become an important tool for repairing natural ecological functions and providing habitat protection for numerous grassland dependent species. Because the historic plant and soil biota communities of the tallgrass prairie were highly diverse with complex interrelationships, historic prairie replication cannot be guaranteed on landscapes that have been so extensively manipulated for extended timeframes (Kardol and Wardle 2010; Fierer et al. 2013). Therefore, ecological restoration should aim to aid the recovery of degraded, damaged, or destroyed ecosystems. A successful restoration 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). The reconstructed prairie state is the result of a long-term commitment involving a multi-step, adaptive management process. Diverse, species-rich seed mixes are important to utilize as they allow the site to undergo successional stages that exhibit changing composition and dominance over time (Smith et al. 2010). On-going management via prescribed fire and/or light grazing can help the site progress from an early successional community dominated by annuals and some weeds to a later seral stage composed of native, perennial grasses, forbs, and a few shrubs. Establishing a prescribed fire regimen that mimics natural disturbance patterns can increase native species cover and diversity while reducing cover of non-native forbs and grasses. Light grazing alone can help promote species richness, while grazing accompanied with fire can control the encroachment of woody vegetation (Brudvig et al. 2007).
Community 5.1
Early Successional Reconstructed Sand Prairie
This community phase represents the early community assembly from prairie reconstruction and is highly dependent on the seed mix utilized and the timing and priority of planting operations. The seed mix should look to include a diverse mix of cool-season and warm-season annual and perennial grasses and forbs typical of the reference state (e.g., little bluestem, porcupinegrass, roundhead lespedeza). Cool-season annuals can help provide litter that promotes cool, moist soil conditions to the benefit of the other species in the seed mix. The first season following site preparation and seeding will typically result in annuals and other volunteer species forming a majority of the vegetative cover. Control of non-native species, particularly perennial species, is crucial at this point to ensure they do not establish before the native vegetation (Martin and Wilsey 2012). After the first season, native warm-season grasses should begin to become more prominent on the landscape.
Community 5.2
Late Successional Reconstructed Sand Prairie
Appropriately timed disturbance regimes (e.g., prescribed fire) applied to the early successional community phase can help increase the beta diversity, pushing the site into a late successional community phase over time. While prairie communities are dominated by grasses, these species can suppress forb establishment and reduce overall diversity and ecological function (Martin and Wilsey 2006; Williams et al. 2007). Reducing accumulated plant litter from perennial bunchgrasses allows more nutrients and light to become available for forb recruitment, allowing greater ecosystem complexity (Wilsey 2008).
Pathway 5.1A
Community 5.1 to 5.2
Selective herbicides are used to control non-native species, and prescribed fire and/or light grazing helps to increase the native species diversity and control woody vegetation.
Pathway 5.2A
Community 5.2 to 5.1
Reconstruction experiences a decrease in native species diversity from drought or improper timing of management actions (e.g., reduced fire frequency, use of non-selective herbicides).
Transition T1A
State 1 to 2
Long-term fire suppression transitions the site to the fire-suppressed scrub state (2).
Transition T1B
State 1 to 3
Vegetation removal and human alterations/transportation of soils transitions the site to the anthropogenic state (3).
Transition T1C
State 1 to 4
Tillage, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Transition T2A
State 2 to 3
Vegetation removal and human alterations/transportation of soils transitions the site to the anthropogenic state (3).
Transition T2B
State 2 to 4
Tillage, seeding of agricultural crops, and non-selective herbicide transition this site to the cropland state (4).
Restoration pathway R2A
State 2 to 5
Site preparation, invasive species control, and seeding native species transition this site to the reconstructed sand prairie state (5).
Transition T4A
State 4 to 2
Land abandonment transitions the site to the fire-suppressed scrub state (2).
Transition T4B
State 4 to 3
Vegetation removal and human alterations/transportation of soils transitions the site to the anthropogenic state (3).
Restoration pathway R4A
State 4 to 5
Site preparation, invasive species control, and seeding native species transition this site to the reconstructed sand prairie state (5).
Transition T5A
State 5 to 2
Land abandonment transitions the site to the fire-suppressed scrub state (2).
Transition T5B
State 5 to 3
Vegetation removal and human alterations/transportation of soils transitions the site to the anthropogenic 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).
