Natural Resources
Conservation Service
Ecological site R108XC511IA
Till Backslope Savanna
Last updated: 11/04/2024
Accessed: 07/18/2026
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Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
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Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 108X–Illinois and Iowa Deep Loess and Drift
The Illinois and Iowa Deep Loess and Drift, West-Central Part (MLRA 108C) encompasses the eastern portion of the Southern Iowa Drift Plain and the Lake Calvin basin of the Mississippi Alluvial Plain landforms (Prior 1991). It lies entirely in one state (Iowa), containing approximately 9,805 square miles (Figure 1). The elevation ranges from approximately 1,110 feet above sea level (ASL) on the highest ridges to about 505 feet ASL in the lowest valleys. Local elevation difference is mainly 10 to 20 feet. However, some valley floors can range from 80 to 200 feet, while some upland flats and valley floors only range between 3 and 6 feet. The MLRA is underlain by Pre-Illinoian glacial till, deposited more than 500,000 years ago and since undergone extensive erosion and dissection. In the northern half of the area the till thickness ranges from 150 to 350 feet and grades to less than 150 feet thick in the southern half. The till is covered by a mantle of Peoria Loess on the hillslopes and Holocene alluvium in the drainageways. Paleozoic bedrock, comprised of limestone, shale, and mudstones, lies beneath the glacial material (USDA-NRCS 2006).
The vegetation in the MLRA has undergone drastic changes over time. Spruce forests dominated the landscape 30,000 to 21,500 years ago. As the last glacial maximum peaked 21,500 to 16,000 years ago, they were replaced with open tundras and parklands. The end of the Pleistocene Epoch saw a warming climate that initially prompted the return of spruce forests, but as the warming continued, spruce trees were replaced by deciduous trees (Baker et al. 1990). Not until approximately 9,000 years ago did the vegetation transition to prairies as climatic conditions continued to warm and subsequently dry. Between 4,000 and 3,000 years ago, oak savannas began intermingling within the prairie landscape, while the more wooded and forested areas maintained a foothold in sheltered areas. This prairie-forest transition ecosystem formed the dominant landscapes until the arrival of European settlers (Baker et al. 1992).Classification relationships
USFS Subregions: Central Dissected Till Plains (251C) Section, Central Dissected Till and Loess Plain (251Cc), Mississippi River and Illinois Alluvial Plains (51Cf), Southeast Iowa Rolling Loess Hills (251Ch) Subsections (Cleland et al. 2007)
U.S. EPA Level IV Ecoregion: Rolling Loess Prairies (47f), Upper Mississippi Alluvial Plain (72d) (USEPA 2013)
National Vegetation Classification – Ecological Systems: North-Central Interior Oak Savanna (CES202.698) (NatureServe 2015)
National Vegetation Classification – Plant Associations: Quercus macrocarpa – (Quercus alba, Quercus stellata)/Andropogon gerardii Wooded Grassland (CEGL002159) (Nature Serve 2015)
Biophysical Settings: North-Central Interior Oak Savanna (BpS 4213940) (LANDFIRE 2009)
Natural Resources Conservation Service – Iowa Plant Community Species List: Opening, Northern Bur Oak (USDA-NRCS 2007)
Iowa Department of Natural Resources: Tallgrass Savanna (INAI 1984)Ecological site concept
Till Backslope Savannas are located within the blue areas on the map (Figure 1). They occur on mid to lower upland hillslopes and high stream terraces. The soils are Alfisols that are somewhat poorly to well-drained and deep, formed from glacial till or valley fill sediments.
The historic pre-European settlement vegetation on this ecological site was dominated by tallgrass prairie interspersed with trees. White oak (Quercus alba L.) and bur oak (Quercus macrocarpa Michx.) are the dominant savanna trees, and big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans (L.) Nash) are the dominant grasses on Till Backslope Savannas. Other grasses and grass-likes that can occur include little bluestem (Schizachyrium scoparium (Michx.) Nash), tapered rosette grass (Dichanthelium acuminatum (Sw.) Gould & C.A. Clark), shortbeak sedge (Carex brevior (Dewey) Mack.), and troublesome sedge (Carex molesta Mack. ex Bright) (Delong and Hooper 1996). Forbs characteristic of an undisturbed plant community associated with this ecological site include whorled milkwort (Polygala verticillata L.), tall cinquefoil (Potentilla arguta Pursh), and stiff sunflower (Helianthus rigidus Nutt. ssp. pauciflorus) (Drobney et al. 2001; Delong and Hooper 1996). Shrubs can occur sporadically across the landscape including New Jersey tea (Ceanothus americanus L.), American plum (Prunus americana Marshall), and prairie willow (Salix humilis Marshall) (Delong and Hooper 1996). Fire is the primary disturbance factor that maintains this site, while herbivory and drought are secondary factors (LANDFIRE 2009).Associated sites
R108XC504IA Loess Upland Savanna
Loess parent material including Downs, Downs variant, Greenbush, Hedrick, Ladoga, and New Vienna soils
R108XC512IA Till Backslope Seep Savanna
Glacial till parent material that is shallow to a perched water table including Rinda soils
F108XC513IA Till Backslope Forest
Glacial till parent and valley fill sediment parent materials that are in fire-protected positions including Bertrand, Douds, Galland, Keswick, Lindley, and Russell soils
F108XC514IA Till Backslope Seep Forest
Glacial till parent material that is shallow to a perched water table including Ashgrove soils
F108XC521IA Colluvial Woodland
Colluvial parent material in a river valley including Coppock, Ely, Judson, Martinsburg, Moingona, Moingona variant, Olmitz, and Olmitz variant soils
Similar sites
R108XC504IA Loess Upland Savanna
Loess Upland Savannas occur higher on the landscape, and parent material is loess
R108XC507IA Sandy Upland Savanna
Sandy Upland Savannas occur in a similar landscape position, but parent material is eolian sandy deposits
R108XC512IA Till Backslope Seep Savanna
Till Backslope Seep Savannas occur in a similar landscape position, but site is shallow to a perched water table
Table 1. Dominant plant species
Tree (1) Quercus alba
(2) Quercus macrocarpaShrub Not specified
Herbaceous (1) Andropogon gerardii
(2) Sorghastrum nutansPhysiographic features
Till Backslope Savannas occur on mid to lower upland hillslopes and high stream terraces (Figure 2). They are situated on elevations ranging from approximately 499 to 1401 feet ASL. The site does not experience flooding, but rather generates runoff to adjacent, downslope ecological sites.
Figure 2. Figure 1. Location of Till Backslope Savanna ecological site within MLRA 108C.
Figure 3. Figure 2. Representative block diagram of Till Backslope Savanna and associated ecological sites.
Table 2. Representative physiographic features
Slope shape across (1) Convex
(2) Linear
Slope shape up-down (1) Convex
(2) Linear
Landforms (1) Upland > Hillslope
Runoff class Medium to high Elevation 499 – 1401 ft Slope 5 – 25 % Water table depth 12 – 80 in Aspect Aspect is not a significant factor Climatic features
The Illinois and Iowa Deep Loess and Drift, West-Central Part falls into the hot humid continental climate (Dfa) Köppen-Geiger climate classification (Peel et al. 2007). In winter, dry, cold air masses periodically shift south from Canada. As these air masses collide with humid air, snowfall and rainfall result. In summer, moist, warm air masses from the Gulf of Mexico migrate north, producing significant frontal or convective rains. Occasionally, hot, dry winds originating from the Desert Southwest will stagnate over the region, creating extended droughty periods in the summer from unusually high temperatures. Air masses from the Pacific Ocean can also spread into the region and dominate producing mild, dry weather in the autumn known as Indian Summers (NCDC 2006).
The soil temperature regime of MLRA 108C is classified as mesic, where the mean annual soil temperature is between 46 and 59°F (USDA-NRCS 2006). Temperature and precipitation occur along a north-south gradient, where temperature and precipitation increase the further south one travels. The average freeze-free period of this ecological site is about 180 days, while the frost-free period is about 165 days (Table 2). The majority of the precipitation occurs as rainfall in the form of convective thunderstorms during the growing season. Average annual precipitation is approximately 38 inches, which includes rainfall plus the water equivalent from snowfall (Table 3). The average annual low and high temperatures are 39 and 60°F, respectively.
Climate data and analyses are derived from 30-year averages gathered from six National Oceanic and Atmospheric Administration (NOAA) weather stations contained within the range of this ecological site (Table 4).Table 3 Representative climatic features
Frost-free period (characteristic range) 140-150 days Freeze-free period (characteristic range) 160-180 days Precipitation total (characteristic range) 40-40 in Frost-free period (actual range) 130-160 days Freeze-free period (actual range) 150-180 days Precipitation total (actual range) 40-40 in Frost-free period (average) 140 days Freeze-free period (average) 170 days Precipitation total (average) 40 in Characteristic rangeActual rangeBarLineFigure 4. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 5. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 6. Monthly maximum temperature range
BarLineFigure 7. Monthly average minimum and maximum temperature
Figure 8. Annual precipitation pattern
Figure 9 Annual average temperature pattern
Climate stations used
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(1) BURLINGTON 2S [USC00131060], Burlington, IA
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(2) NEWTON [USC00135992], Newton, IA
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(3) GRINNELL 3 SW [USC00133473], Grinnell, IA
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(4) OSKALOOSA [USC00136327], Oskaloosa, IA
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(5) TIPTON [USC00138266], Tipton, IA
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(6) WASHINGTON [USC00138688], Washington, IA
">Influencing water features
Till Backslope Savannas are not influenced by wetland or riparian water features. Precipitation is the main source of water for this ecological site. Infiltration is slow to moderate (Hydrologic Groups B and C), and surface runoff is medium to high. Precipitation infiltrates the soil surface and percolates downward through the horizons unimpeded by any restrictive layer. The underlying Mississippian bedrock aquifer has few creviced openings throughout the MLRA, restricting recharge from this ecological site. However, there are numerous surficial aquifers that are shallow and allow recharge via percolation (Prior et al. 2003). Surface runoff contributes some water to downslope ecological sites (Figure 5).
Figure 10. Figure 5. Hydrologic cycling in Till Backslope Savanna ecological site.
Soil features
Soils of Till Backslope Savannas are in the Alfisols order, further classified as Aquertic Hapludalfs and Mollic Hapludalfs with slow to moderate infiltration and medium to high runoff potential. The soil series associated with this site includes Armstrong, Caleb, Gara, Mystic, and Waubeek (Figure 6). The parent material is glacial till or valley fill sediments, and the soils are somewhat poorly to well-drained and deep. Soil pH classes are very strongly acid to moderately alkaline. No rooting restrictions are noted for the soils of this ecological site (Table 5).
Figure 11. Figure 6. Profile sketches of soil series associated with Till Backslope Savanna.
Table 4. Representative soil features
Parent material (1) Till
Surface texture (1) Loam
(2) Silt loam
(3) Clay loam
(4) Silty clay loam
Family particle size (1) Fine-loamy
Drainage class Somewhat poorly drained to well drained Permeability class Slow to moderately slow Soil depth 80 in Surface fragment cover <=3" Not specified Surface fragment cover >3" Not specified Available water capacity
(Depth not specified)6 – 7 in Calcium carbonate equivalent
(Depth not specified)0 – 25 % Soil reaction (1:1 water)
(Depth not specified)4.5 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)0 – 6 % Subsurface fragment volume >3"
(Depth not specified)0 – 2 % 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. Till Backslope Savannas form an aspect of this vegetative continuum. This ecological site occurs on mid to lower upland hillslopes and high stream terraces on moderately well to well-drained soils. Species characteristic of this ecological site consist of tallgrass herbaceous vegetation with scattered trees.
Fire is a critical disturbance factor that maintains Till Backslope Savannas. Fire intensity typically consisted of periodic 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; White 1994).
Drought and herbivory by native ungulates have also played a role in shaping this ecological site. The periodic episodes of reduced soil moisture in conjunction with the somewhat poorly to well-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. Bison (Bos bison) grazing, while present, served a more limited role in community composition and structure than lands further west. Prairie elk (Cervus elaphus) and white-tailed deer (Odocoileus virginianus) likely contributed to woody species reduction but are also considered to be of a lesser impact compared to the west (LANDFIRE 2009). When coupled with fire, periods of drought and herbivory can further delay the establishment of woody vegetation (Pyne et al. 1996).
Today, Till Backslope Savannas are considered extirpated in the MLRA as a result of being type-converted to agricultural production land (NatureServe 2015). Lands that have not been put into production have had fire suppressed long enough to transition the site from an open savanna to a closed woodland or forest. A return to the historic plant community may not be possible following extensive land modification, but long-term conservation agriculture or savanna reconstruction 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 and transition model
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
States 2 and 5 (additional transitions)
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 5 submodel, plant communities
State 1
Reference StateThe reference plant community is categorized as a mesic oak savanna, dominated by herbaceous vegetation and scattered trees. The two community phases within the reference state are dependent on periodic fires. Surface fires are the dominant fire regime, comprising approximately 96 percent of all fires and occurring every five years. Mixed and replacement fires comprise the remaining 4 percent, occurring approximately every 3 and 1 years, respectively (LANDFIRE 2009). Fire intensity and return intervals alter species composition, cover, and extent, while regular fire intervals keep woody species from encroaching. Episodic droughts and storm damage have more localized impacts in the reference phases, but do contribute to overall species composition, diversity, cover, and productivity.
Community 1.1
White Oak – Bur Oak/Big Bluestem – IndiangrassSites in this reference community phase are dominated by a mix of grasses and forbs with scattered trees. White oak and bur oak are the dominant trees on the site. The tree layer comprises no more than 20 percent cover and trees size class is medium (9 to 21-inch DBH). Vegetative cover is continuous (up to 100 percent) and plants can reach heights up to 3 feet tall (LANDFIRE 2009). Big bluestem, Indiangrass, little bluestem, tapered rosette grass, shortbeak sedge, and troublesome sedge are common monocots. Forb diversity is high and can include such species as white heath aster (Symphyotrichum ericoides (L.) G.L. Nesom var. ericoides), Virginia strawberry (Fragaria virginiana Duchesne), and palespike lobelia (Lobelia spicata Lam.) (Delong and Hooper 1996). Surface fires every 5 years will maintain this class, but an extended fire return interval will shift the community to phase 1.2 (LANDFIRE 2009).
Community 1.2
White Oak – Bur Oak/New Jersey Tea – American Plum/Big Bluestem – IndiangrassThis reference community phase represents a successional shift as a result of an extended fire return interval. This fire-free period allows woody shrubs to establish, including New Jersey tea, American plum, and blackberries (Rubus L.). Tree cover increases to as much as 60 percent, and tree size class moves from medium to large (21 to 33-inch DBH). Surface fires every 5 years will maintain this class, but mixed or replacement fires will shift the community back to phase 1.1 (LANDFIRE 2009).
Pathway 1.1A
Community 1.1 to 1.2Extended fire return interval in excess of 5 years.
Pathway 1.2A
Community 1.2 to 1.1Mixed or replacement fire.
State 2
Fire-suppressed StateFire suppression can transition the reference plant community from an open savanna to a closed canopy forest. As the natural fire regime is removed from the landscape, encroachment and dominance by shade-tolerant, fire-intolerant species ensues (Asbjornsen et al. 2005). This results in a positive feedback loop of mesophication whereby plant community succession continuously creates cool, damp shaded conditions that perpetuate a closed canopy ecosystem (Nowacki and Abrams 2008). Succession to this closed canopy state can occur in as little as 25 years from the last fire (LANDFIRE 2009).
Community 2.1
White Oak – Bur Oak/Shagbark Hickory – Black Cherry/Pennsylvania SedgeThis community represents the early stages of long-term fire suppression. The lack of fire allows the tree canopy to close (60 to 80 percent cover) and stem density to increase. White oak and bur oak are the dominant trees, but shagbark hickory (Carya ovata (Mill.) K. Koch) and black cherry (Prunus serotina Ehrh.) begins to form a prominent subcanopy (LANDFIRE 2009). The sun-loving herbaceous layer is slowly replaced by more shade-tolerant species. Rare, surface fires that escape suppression efforts will maintain this phase, but a complete lack of fire for 30 years will shift the community to phase 2.2 (LANDFIRE 2009).
Community 2.2
White Oak – Shagbark Hickory/Black Cherry/Pennsylvania SedgeSites falling into this community phase have transitioned into a closed canopy oak-hickory forest. Mature white and bur oaks are still present, but seedings and saplings are generally absent as they do not establish well under the continuous canopies (Tirmenstein 1991a; Gucker 2011). As fire suppression has continued, shagbark hickory saplings have matured and now become co-dominant with the oaks, while black cherry is prevalent in the subcanopy (Tirmenstein 1991b; LANDFIRE 2009). A single, large disturbance event – such as a windstorm – can create open pockets that allow the community to temporarily shift back to phase 2.1.
Pathway 2.1A
Community 2.1 to 2.2Continued fire suppression (+30 years).
Pathway 2.2A
Community 2.2 to 2.1Single large disturbance event.
State 3
Forage StateThe forage state occurs 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, the non-native species were able to spread and expand across the landscape, reducing the native species diversity and ecological function. This state is most common on the steeper slopes on the landscape.
Community 3.1
HayfieldSites 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).
Community 3.2
Continuous Pastured GrazingThis 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, sometimes completely excluding the native vegetation.
Community 3.3
Periodic-rest Pastured GrazingThis 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 3.2Mechanical harvesting is replaced with domestic livestock utilizing continuous grazing.
Pathway 3.1B
Community 3.1 to 3.3Mechanical harvesting is replaced with domestic livestock utilizing periodic-rest grazing.
Pathway 3.2A
Community 3.2 to 3.1Domestic livestock are removed, and mechanical harvesting is implemented.
Pathway 3.2B
Community 3.2 to 3.3Periodic-rest grazing replaces continuous grazing.
Pathway 3.3B
Community 3.3 to 3.1Domestic livestock are removed, and mechanical harvesting is implemented.
Pathway 3.3A
Community 3.3 to 3.2Continuous grazing replaces periodic-rest grazing.
State 4
Cropland StateThe low topographic relief across the MLRA has resulted in nearly the entire area being converted to agriculture (Eilers and Roosa 1994). 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 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. This state is most common on the gentler slopes on the landscape.
Community 4.1
Conventional Tillage FieldSites 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 FieldThis 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 FieldThis 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 4.2Tillage 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 4.3Tillage 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 4.1Intensive tillage is utilized, and monoculture row-cropping is established.
Pathway 4.2B
Community 4.2 to 4.3Cover crops are implemented to minimize soil erosion.
Pathway 4.3B
Community 4.3 to 4.1Intensive 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 4.2Cover crop practices are abandoned.
State 5
Reconstructed Oak Savanna StateSavanna 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 savanna 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 savanna state is the result of a long-term commitment involving a multi-step, adaptive management process. Oak plantings or selective tree thinning of non-oak species will be required in order to reproduce the overstory canopy (Asbjornsen et al. 2005). Diverse, species-rich seed mixes may be 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 will 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, shrubs, and eventually mature bur oaks. Establishing a prescribed fire regime 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 undesirable woody vegetation (Brudvig et al. 2007).
Community 5.1
Early Successional Reconstructed Oak SavannaThis community phase represents early community assembly and is highly dependent on the timing and priority of planting and/or tree thinning operations and the herbaceous seed mix utilized. If oak planting is needed, acorns should be planted shortly after harvest as acorns germinate shortly after seedfall and require no cold stratification. Browse protection may need to be installed to protect newly established seedlings from animal predation (Gucker 2011). If selective tree removal is needed, canopy reduction should encompass between 16 to 45 percent of the undesirable species in a single year (Asbjornsen et al. 2005). The seed mix should look to include a diverse mix of native cool-season and warm-season annual and perennial grasses and forbs typical of the reference state. Native, cool-season annuals can help to 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 in order 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 and over time close the canopy.
Community 5.2
Late Successional Reconstructed Oak SavannaAppropriately 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 oak savanna communities are dominated by grasses, these species can suppress forb establishment and reduce overall diversity and ecological functioning (Martin and Wilsey 2006; Williams et al. 2007). Reducing accumulated plant litter from such tallgrasses as big bluestem and Indiangrass allows more light and nutrients to become available for forb recruitment, allowing for greater ecosystem complexity (Wilsey 2008). Prescribed fire should be used on a cycle no less than every five years in order to allow the oaks to establish and mature (Gucker 2011).
Pathway 5.1A
Community 5.1 to 5.2Selective herbicides are used to control non-native species, and prescribed fire and/or light grazing help to increase the native species diversity and control non-oak woody vegetation.
Pathway 5.2B
Community 5.2 to 5.1Reconstruction 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 2Long-term fire suppression transitions the site to the fire-suppressed state (2).
Transition T1B
State 1 to 3Cultural treatments to enhance forage quality and yield transitions the site to the forage state (3).
Transition T1C
State 1 to 4Tillage, seeding of agricultural crops, and non-selective herbicide transition the site to the cropland state (4).
Transition T2A
State 2 to 3Cultural treatments to enhance forage quality and yield transitions the site to the forage state (3).
Transition T2B
State 2 to 4Tillage, seeding of agricultural crops, and non-selective herbicide transition this site to the cropland state (4).
Restoration pathway R2A
State 2 to 5Site preparation, invasive species control, and seeding native species transition this site to the reconstructed oak savanna state (5).
Transition T3A
State 3 to 2Land abandonment transitions the site to the fire-suppressed state (2).
Transition T3B
State 3 to 4Tillage, seeding of agricultural crops, and non-selective herbicide transition this site to the cropland state (4).
Restoration pathway R3A
State 3 to 5Site preparation, tree planting, invasive species control, and seeding native species transition this site to the reconstructed oak savanna state (5).
Transition T4A
State 4 to 2Land abandonment transitions the site to the fire-suppressed state (2).
Transition T4B
State 4 to 3Cultural treatments to enhance forage quality and yield transitions the site to the forage state (3).
Restoration pathway R4A
State 4 to 5Site preparation, tree planting, invasive species control, and seeding native species transition this site to the reconstructed oak savanna state (5).
Transition T5A
State 5 to 2Fire suppression and removal of active management transitions this site to the fire-suppressed forested state (2).
Transition T5B
State 5 to 3Cultural treatments to enhance forage quality and yield transition the site to the forage state (3).
Transition T5C
State 5 to 4Tillage, seeding of agricultural crops, and non-selective herbicide transition this site to the cropland state (4).
Additional community tables
Table 5. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 6. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 7. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 2.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 9. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 3.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 11. Community 3.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 12. Community 4.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 13. Community 4.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 14. Community 4.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 15. Community 5.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 16. Community 5.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Supporting information
Inventory data references
No field plots were available for this site. A review of the scientific literature and professional experience were used to approximate the plant communities for this provisional ecological site. Information for the state-and-transition model was obtained from the same sources. All community phases are considered provisional based on these plots and the sources identified in ecological site description.
Other references
Asbjornsen, H., L.A. Brudvig, C.M. Mabry, C.W. Evans, and H.M. Karnitz. 2005. Defining reference information for restoring ecologically rare tallgrass oak savannas in the midwestern United States. Journal of Forestry 103: 345-350.
Baker, R.G., C.A. Chumbley, P.M. Witinok, and H.K. Kim. 1990. Holocene vegetational changes in eastern Iowa. Journal of the Iowa Academy of Science 97: 167-177.
Baker, R.G., L.J. Maher, C.A. Chumbley, and K.L. Van Zant. 1992. Patterns of Holocene environmental changes in the midwestern United States. Quaternary Research 37: 379-389.
Barrett, S.W. 1980. Indians and fire. Western Wildlands Spring: 17-20.
Bharati, L., K.-H. Lee, T.M. Isenhart, and R.C. Schultz. 2002. Soil-water infiltration under crops, pasture, and established riparian buffer in Midwestern USA. Agroforestry Systems 56: 249-257.
Brudvig, L.A., C.M. Mabry, J.R. Miller, and T.A. Walker. 2007. Evaluation of central North American prairie management based on species diversity, life form, and individual species metrics. Conservation Biology 21: 864-874.
Cleland, D.T., J.A. Freeouf, J.E. Keys, G.J. Nowacki, C. Carpenter, and W.H. McNab. 2007. Ecological Subregions: Sections and Subsections of the Coterminous United States. USDA Forest Service, General Technical Report WO-76. Washington, DC. 92 pps.
Delong, K.T. and C. Hooper. 1996. A potential understory flora for oak savanna in Iowa. The Journal of the Iowa Academy of Sciences 103: 9-28.
Drobney, P.D., G.S. Wilhelm, D. Horton, M. Leoschke, D. Lewis, J. Pearson, D. Roosa, and D. Smith. 2001. Floristic Quality Assessment for the State of Iowa. Neal Smith National Wildlife Refuge and Ada Hayden Herbarium, Iowa State University, Ames, IA. 123 pps.
Eilers, L. and D. Roosa. 1994. The Vascular Plants of Iowa: An Annotated Checklist and Natural History. University of Iowa Press, Iowa City, IA. 319 pps.
Fierer, N., J. Ladau, J.C. Clemente, J.W. Leff, S.M. Owens, K.S. Pollard, R. Knight, J.A. Gilbert, and R.L. McCulley. 2013. Reconstructing the microbial diversity and function of pre-agricultural tallgrass prairie soils in the United States. Science 342: 621-624.
Franzluebbers, A.J., J.A. Stuedemann, H.H. Schomberg, and S.R. Wilkinson. 2000. Soil organic C and N pools under long-term pasture management in the Southern Piedmont USA. Soil Biology and Biochemistry 32:469-478.
Gucker, C.L. 2011. Quercus macrocarpa. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available at https://www.crs-feis.org/feis/. (Accessed 23 March 2018).
Iowa Natural Areas Inventory [INAI]. 1984. An Inventory of Significant Natural Areas in Iowa: Two Year Progress Report of the Iowa Natural Areas Inventory. Iowa Natural Areas Inventory, Iowa Department of Natural Resources, Des Moines, IA.
Karol, P. and D.A. Wardle. 2010. How understanding aboveground-belowground linkages can assist restoration ecology. Trends in Ecology and Evolution 25: 670-679.
LANDFIRE. 2009. Biophysical Setting 4213940 North-Central Interior Oak Savanna. In: LANDFIRE National Vegetation Dynamics Models. USDA Forest Service and US Department of Interior. Washington, DC.
Leake, J., D. Johnson, D. Donnelly, G. Muckle, L. Boddy, and D. Read. 2004. Networks of power and influence: the role of mycorrhizal mycelium in controlling plant communities and agroecosystem functioning. Canadian Journal of Botany 82: 1016-1045.
Martin, L.M. and B.J. Wilsey. 2006. Assessing grassland restoration success: relative roles of seed additions and native ungulate activities. Journal of Applied Ecology 43: 1098-1110.
Martin, L.M. and B.J. Wilsey. 2012. Assembly history alters alpha and beta diversity, exotic-native proportions and functioning of restored prairie plant communities. Journal of Applied Ecology 49: 1436-1445.
National Climate Data Center [NCDC]. 2006. Climate of Iowa. Central Region Headquarters, Climate Services Branch, National Climatic Data Center, Asheville, NC.
NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1 NatureServe, Arlington, VA. Available at http://explorer.natureserve.org. (Accessed 13 February 2017).
Nowacki, G.J. and M.D. Abrams. 2008. The demise of fire and “mesophication” of forests in the eastern United States. BioScience 58: 123-138.
Peel, M.C., B.L. Finlayson, and T.A. McMahon. 2007. Updated world map of the Köppen-Geiger climate classification. Hydrology and Earth System Sciences 11: 1633-1644.
Prior, J.C. 1991. Landforms of Iowa. University of Iowa Press for the Iowa Department of Natural Resources, Iowa City, IA. 153 pps.
Prior, J.C., J.L. Boekhoff, M.R. Howes, R.D. Libra, and P.E. VanDorpe. 2003. Iowa’s Groundwater Basics: A Geological Guide to the Occurrence, Use, & Vulnerability of Iowa’s Aquifers. Iowa Department of Natural Resources, Iowa Geological Survey Educational Series 6. 92 pps.
Pyne, S.J., P.L. Andrews, and R.D. Laven. 1996. Introduction to Wildland Fire, Second Edition. John Wiley and Sons, Inc. New York, New York. 808 pps.
Skinner, R.H. 2008. High biomass removal limits carbon sequestration potential of mature temperate pastures. Journal for Environmental Quality 37: 1319-1326.
Smith, D.D. 1998. Iowa prairie: original extent and loss, preservation, and recovery attempts. The Journal of the Iowa Academy of Sciences 105: 94-108.
Smith, D.D., D. Williams, G. Houseal, and K. Henderson. 2010. The Tallgrass Prairie Center Guide to Prairie Restoration in the Upper Midwest. University of Iowa Press, Iowa City, IA. 338 pps.
Society for Ecological Restoration [SER] Science & Policy Working Group. 2002. The SER Primer on Ecological Restoration. Available at: http://www.ser.org/. (Accessed 28 February 2017).
Teague, W.R., S.L. Dowhower, S.A. Baker, N. Haile, P.B. DeLaune, and D.M. Conover. 2011. Grazing management impacts on vegetation, soil biota and soil chemical, physical and hydrological properties in tall grass prairie. Agriculture, Ecosystems and Environment 141: 310-322.
Tirmenstein, D.A. 1991a. Quercus alba. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available at https://www.crs-feis.org/feis/. (Accessed 23 March 2018).
Tirmenstein, D.A. 1991b. Carya ovata. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Available at https://www.crs-feis.org/feis/. (Accessed 29 March 2018).
Tomer, M.D., D.W. Meek, and L.A. Kramer. 2005. Agricultural practices influence flow regimes of headwater streams in western Iowa. Journal of Environmental Quality 34:1547-1558.
Undersander, D., B. Albert, D. Cosgrove, D. Johnson, and P. Peterson. 2002. Pastures for Profit: A Guide to Rotational Grazing (A3529). University of Wisconsin-Extension and University of Minnesota Extension Service. 43 pps.
United States Department of Agriculture – Natural Resources Conservation Service (USDA-NRCS). 2003. National Range and Pasture Handbook, Revision 1. Grazing Lands Technology Institute. 214 pps.
United States Department of Agriculture – Natural Resource Conservation Service (USDA-NRCS). 2006. Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. 682 pps.
United States Department of Agriculture – Natural Resources Conservation Service (USDA-NRCS). 2007. Iowa NRCS Plant Community Species Lists. Des Moines, IA. Available at https://www.nrcs.usda.gov/wps/ portal/nrcs/detail/ia/technical/ecoscience/bio/?cid=nrcs142p2_008160. (Accessed 19 January 2018).
U.S. Environmental Protection Agency [EPA]. 2013. Level III and Level IV Ecoregions of the Continental United States. Corvallis, OR, U.S. EPA, National Health and Environmental Effects Research Laboratory, map scale 1: 3,000,000. Available at http://www.epa.gov/eco-research/level-iii-andiv-ecoregions-continental-united-states. (Accessed 1 March 2017).
White, J. 1994. How the terms savanna, barrens, and oak openings were used in early Illinois. In: J. Fralisch, ed. Proceedings of the North American Conference on Barrens and Savannas. Illinois State University, Normal, IL.
Williams, D.A., L.L. Jackson, and D.D Smith. 2007. Effects of frequent mowing on survival and persistence of forbs seeded into a species-poor grassland. Restoration Ecology 15: 24-33.
Wilsey, B.J. 2008. Productivity and subordinate species response to dominant grass species and seed source during restoration. Restoration Ecology 18: 628-637.Contributors
Lisa Kluesner
Ryan DermodyApproval
Suzanne Mayne-Kinney, 11/04/2024
Acknowledgments
This project could not have been completed without the dedication and commitment from a variety of partners and staff (Table 6). Team members supported the project by serving on the technical team, assisting with the development of state and community phases of the state-and-transition model, providing peer review and technical editing, and conducting quality control and quality assurance reviews. Organization Name Title Location Drake University: Dr. Tom Rosburg Professor of Ecology and Botany Des Moines, IA Iowa Department of Natural Resources: Kevin Andersen Private Lands Biologist Fairfield, IA John Pearson Ecologist Des Moines, IA LANDFIRE (The Nature Conservancy): Randy Swaty Ecologist Evanston, IL Natural Resources Conservation Service: Rick Bednarek Iowa State Soil Scientist Des Moines, IA Leland Camp Soil Scientist Waverly, IA Stacey Clark Regional Ecological Site Specialist St. Paul, MN Ryan Dermody Soil Survey Leader Waverly, IA Tonie Endres Senior Regional Soil Scientist Indianapolis, IN John Hammerly Soil Data Quality Specialist Indianapolis, IN Lisa Kluesner Ecological Site Specialist Waverly, IA Sean Kluesner Earth Team Volunteer Waverly, IA Jeff Matthias State Grassland Specialist Des Moines, IA Kevin Norwood Soil Survey Regional Director Indianapolis, IN Doug Oelmann Soil Scientist Des Moines, IA James Phillips GIS Specialist Des Moines, IA Jason Steele Area Resource Soil Scientist Fairfield, IA Doug Wallace Ecologist ACES Program Columbia, MO This site was originally published by Lisa Kluesner on 7/1/2019.
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date 07/18/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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PrintThe Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
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