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Pennyroyal Plain Wet-Mesic Depression Prairie

Synonyms

Pennyroyal Plain Prairie & Barrens Ecological System (NatureServe 2015)

Distribution

Northwestern Middle Tennessee (Pennyroyal Plain) and central and western Kentucky (Pennyroyal and Elizabethtown Plains) extending northward possibly into southern Indiana (Mitchell Plain). Extant remnants are known primarily from Fort Campbell Army Base (Montgomery & Stewart cos., TN and Christian Co., KY) and from one remnant in northeastern Montgomery Co., TN.  

Vegetation Description

Grasses and forbs dominate this small patch wet grassland community that ranges in height from 0 – 2.5 m. Tree saplings and shrubs may be present but historically many examples of this community would have been nearly treeless.

Physical Characterization

This community occurs in the Pennyroyal Karst Plain ecoregion (Estes & Fleming 2015) at an elevation of 173-176 m (570-580 ft). It is associated with karst depressions with 0-2% slopes. The geology is Paleozoic Mississippian-aged St. Louis and Warsaw limestones. 

The soils associated with this community belong to the Guthrie and Taft soil series. The Guthrie is primarily associated with depressional landforms, which in the Pennyroyal are depressions formed in underlying karst limestone. The Taft is often associated with upland flats developed on ancient alluvium or in depressions. Guthrie soils are often minor inclusions within the Taft series. Guthrie soils are classified as thermic Typic Fragiaquults whereas Taft soils are Glossaquic Fragiudults.

These deep soils are derived from loess and/or loamy alluvium and soils of the Guthrie and Taft series range from silt loam in the upper horizons to silty clay loam at lower depths. A clay fragipan is present at about 18-40 inches below the surface rendering these sites poorly to somewhat poorly drained and may experience ponding during wet seasons. Soil pH ranges from strongly to very strongly acid.

Soil series involved:

  • Gu - Guthrie silt loam
  • Ta - Taft silt loam

Natural Processes

This community occurs in the open rolling Pennyroyal Plain, which is chocked with thousands of depressions. Fires once swept across the plain on an annual basis. Such a high fire-return interval favored the development of open, nearly treeless tallgrass prairie. Fires would have likely burned even many of the wet depressions depending on time of year, standing vegetation, degree of wetness, and whether standing water was present. These communities generally lack long periods of standing water as ponds would and therefore they support perennial vegetation. The combination of frequent burning, grazing by herbivores (e.g. bison), and perennially wet soil resulted in development of wet prairie.

Reports from the late 18th and early 19th centuries indicate Native Americans were setting fires; however, Frost (___) provides data from his study of the fire ecology of Mammoth Cave National Park that suggests at least some of the fires were likely ignited by lightning.  

Beginning in about the 1830s, widespread fire suppression commenced in the Pennyroyal. Frost (___) reports that the rapid influx of domesticated livestock (cattle, horses, sheep) in the 1830s resulted in overgrazing to such an extent that the prairies no longer had enough plant matter to carry fires as they once did prior to overgrazing. With fire suppression, the prairies quickly became susceptible to rapid growth of trees and shrubs. What wasn't cultivated or grazed quickly grew into oak-hickory woodlands. Many of the wet depressions that had been maintained by fire developed into the countless forested wetlands we see on the Pennyroyal Plain today.

Dominant Plants

Herbaceous Layer: Desmodium glabellum (____), Dichanthelium dichotomum sensu lato (____), Dichanthelium scoparium (___), Rhexia mariana (Maryland meadow-beauty), Sorghastrum nutans (Indian grass)

Characteristic Plants

Restricted or Noteworthy Plants

Carex alata (____), Gratiola brevifolia (____)Spartina pectinata (prairie cordgrass)

Invasive Species
Phragmites australis ssp. australis is widely escaping in western Kentucky and southern Illinois and likely will have strong invasive potential in remaining prairie remnants although it is not yet known to be present in TN examples of this community. 

Community Variation and Subtypes

At this time this community remains mostly undescribed. Part of the reason for this is that most of the extant examples are located on Fort Campbell Army Base and due to access issues they have not been adequately studied. Off Fort Campbell, the single known example in TN is of degraded quality with a high percentage of common species with few conservatives and a fairly high percentage of non-native species.

Variation within this community seems to depend on amount of seasonal flooding. Microhabitats on the wet-mesic portion of the spectrum seem to support tallgrass praire. 

mesic-wetSorghastrum nutans Panicum anceps - Dichanthelium scoparium Desmodium glabellum/canescens Vernonia missurica - Conoclinium coelestinum

The closest matches in the USNVC for mesic-wet prairie is the following association:

CEGL004677 Andropogon gerardii - (Sorghastrum nutans) Kentucky Herbaceous Vegetation G1G2
Kentucky Mesic Tallgrass Prairie
Big Bluestem - (Indiangrass) Kentucky Herbaceous Vegetation

Wetter examples prone to more prolonged flooding support less tallgrass species and more species typical of depression marshes. Prairie cordgrass (Spartina pectinata) occurred at one wet prairie in northeastern Montgomery Co. but has not been seen in a few decades.

wet: Dichanthelium scoparium Dichanthelium dichotomum - Rhexia mariana - Scirpus georgianus Hibiscus moscheutos Persicaria spp. - Leersia virginica - Setaria parviflora

The closest matches in the USNVC to this wet prairie association is:

CEGL004118 Spartina pectinata Western Kentucky Herbaceous Vegetation G1Q
Kentucky Prairie Cordgrass Marsh
Prairie Cordgrass Western Kentucky Herbaceous Vegetation

The soils associated with this community belong to the Guthrie and Taft soil series. The Guthrie is primarily associated with depressional landforms, which in the Pennyroyal are depressions formed in underlying karst limestone. The Taft is often associated with upland flats developed on ancient alluvium or in depressions. Guthrie soils are often minor inclusions within the Taft series. Guthrie soils are classified as thermic Typic Fragiaquults whereas Taft soils are Glossaquic Fragiudults.

These deep soils are derived from loess and/or loamy alluvium and soils of the Guthrie and Taft series range from silt loam in the upper horizons to silty clay loam at lower depths. A clay fragipan is present at about 18-40 inches below the surface rendering these sites poorly to somewhat poorly drained and may experience ponding during wet seasons. Soil  pH ranges from strongly to very strongly acid.

Soil series involved:

Natural Processes

This community occurs in the open rolling Pennyroyal Plain, which is chocked with thousands of depressions. Fires once swept across the plain on an annual basis. Such a high fire-return interval favored the development of open, nearly treeless tallgrass prairie. Fires would have likely burned even many of the wet depressions depending on time of year, standing vegetation, degree of wetness, and whether standing water was present. These communities generally lack long periods of standing water as ponds would and therefore they support perennial vegetation. The combination of frequent burning, grazing by herbivores (e.g. bison), and perennially wet soil resulted in development of wet prairie.

Reports from the late 18th and early 19th centuries indicate Native Americans were setting fires; however, Frost (___) provides data from his study of the fire ecology of Mammoth Cave National Park that suggests at least some of the fires were likely ignited by lightning.  

Beginning in about the 1830s, widespread fire suppression commenced in the Pennyroyal. Frost (___) reports that the rapid influx of domesticated livestock (cattle, horses, sheep) in the 1830s resulted in overgrazing to such an extent that the prairies no longer had enough plant matter to carry fires as they once did prior to overgrazing. With fire suppression, the prairies quickly became susceptible to rapid growth of trees and shrubs. What wasn't cultivated or grazed quickly grew into oak-hickory woodlands. Many of the wet depressions that had been maintained by fire developed into the countless forested wetlands we see on the Pennyroyal Plain today.

Dominant Plants

Herbaceous Layer: Desmodium glabellum (____), Dichanthelium dichotomum sensu lato (____), Dichanthelium scoparium (___), Rhexia mariana (Maryland meadow-beauty), Sorghastrum nutans (Indian grass)

Characteristic Plants

Restricted or Noteworthy Plants

Carex alata (____), Gratiola brevifolia (____)Spartina pectinata (prairie cordgrass)

Invasive Species
Phragmites australis ssp. australis is widely escaping in western Kentucky and southern Illinois and likely will have strong invasive potential in remaining prairie remnants although it is not yet known to be present in TN examples of this community. 

Community Variation and Subtypes

At this time this community remains mostly undescribed. Part of the reason for this is that most of the extant examples are located on Fort Campbell Army Base and due to access issues they have not been adequately studied. Off Fort Campbell, the single known example in TN is of degraded quality with a high percentage of common species with few conservatives and a fairly high percentage of non-native species.

Variation within this community seems to depend on amount of seasonal flooding. Microhabitats on the wet-mesic portion of the spectrum seem to support tallgrass praire. 

mesic-wet Sorghastrum nutans  Panicum anceps  -  Dichanthelium scoparium  Desmodium glabellum/canescens  Vernonia missurica  -  Conoclinium coelestinum

The closest matches in the USNVC for mesic-wet prairie is the following association:

CEGL004677 Andropogon gerardii - (Sorghastrum nutans) Kentucky Herbaceous Vegetation G1G2
Kentucky Mesic Tallgrass Prairie
Big Bluestem - (Indiangrass) Kentucky Herbaceous Vegetation

The closest matches in the USNVC for mesic-wet prairie is the following association:

CEGL004677 Andropogon gerardii - (Sorghastrum nutans) Kentucky Herbaceous Vegetation G1G2
Kentucky Mesic Tallgrass Prairie
Big Bluestem - (Indiangrass) Kentucky Herbaceous Vegetation

Wetter examples prone to more prolonged flooding support less tallgrass species and more species typical of depression marshes. Prairie cordgrass (Spartina pectinata) occurred at one wet prairie in northeastern Montgomery Co. but has not been seen in a few decades.

wet: Dichanthelium scoparium Dichanthelium dichotomum - Rhexia mariana - Scirpus georgianus Hibiscus moscheutos Persicaria spp. - Leersia virginica - Setaria parviflora

The closest matches in the USNVC to this wet prairie association is:

CEGL004118 Spartina pectinata Western Kentucky Herbaceous Vegetation G1Q
Kentucky Prairie Cordgrass Marsh
Prairie Cordgrass Western Kentucky Herbaceous Vegetation


Associated Natural Communities

Pennyroyal Plain Dry Prairie, Pennyroyal Plain Mesic Prairie, Pennyroyal Plain Depression Marsh

Similar Communities

Similar wet grasslands, in terms of floristic composition, likely were once abundant in the loess plains of western TN and KY.

Presettlement Distribution and Size

The Pennyroyal Plain Prairie was once the largest tallgrass prairie in the Southeast. By some accounts it once covered as much as 3.7 million acres of west-central KY, northwestern middle TN, and portions of southern IN. Numerous accounts testify to the Pennyroyal being nearly treeless in the 1790s-1810s. The karst plain has thousands of wet depressions that would have once supported thousands, or more likely tens of thousands, of acres of wet prairies. How much wet prairie existed cannot be known but it is clear that more than 99% of this community has been destroyed.

Present Status

This is perhaps the rarest grassland type in TN. High quality examples are extremely rare and perhaps non-existent outside of Fort Campbell. If any high-quality examples exist at Fort Campbell they have yet to be described. This type should be critically imperiled.

Representative Sites

Montgomery Co., TN: roadside strip between Hwy 41 and CSX railroad (36.627971, -87.139021)

Stewart Co., TN: Fort Campbell Army Base impact zone (36.619340, -87.697441)


Threats

The one site known in TN not on Fort Campbell just southeast of Guthrie has escaped being converted to agricultural fields and succession to forests because it is sandwiched between a highway and an adjacent railroad. This narrow strip, just 40 ft wide at its widest point, faces many significant and constant threats. These include herbicide spraying from both the railroad and from the highway by rail and road maintenance crews. The narrow strip is also subjected to excessive mowing. The small size and long, thin shape (0.8 mi long x 30-40 ft wide) of this remnant makes it susceptible to edge effect, degradation from invasive species, and random events.

On Fort Campbell, most examples of this community are found in the 25,000 acre impact zone, only the southern portion of which is in TN. These examples are unable to be inventoried because the impact zone is strictly off-limits due to presence of unexploded ordnances. The impact zone supports approximately 20,000+ acres of grassland, much of which is dry to submesic grassland/savanna. However, the impact zone has quite a bit of fine-scale topographic variation, including seasonally wet flats and depressions. Most areas of the impact zone burn on an annual basis. Beavers also inhabit the impact zone and are expanding some wetland areas. Thus the grasslands of Fort Campbell represent the nearest thing left to the original prairie that once covered the Pennyroyal.  

Management Considerations

Previous Studies

Chester (___)'s conducted a floristic survey of __ prairies at Fort Campbell but their work focused mostly on upland types. __ of the __ species they documented are wetland species. These are listed below in the floristic list for this community as they are presumed to occur in this community. No quantitative vegetation studies have been conducted specifically for the Pennyroyal Plain prairie system.

Future Research Needs

A focused effort is needed to inventory the wet prairies at Fort Campbell to document their floristic composition as well as to classify the various associations of wet prairie, most of which are likely undescribed. Such work is needed to inform future conservation work in the region, especially restoration and re-creation of Pennyroyal wetlands.



Associated Natural Communities

Pennyroyal Plain Dry Prairie, Pennyroyal Plain Mesic Prairie, Pennyroyal Plain Depression Marsh

Similar Communities

Similar wet grasslands, in terms of floristic composition, likely were once abundant in the loess plains of western TN and KY.

Presettlement Distribution and Size

The Pennyroyal Plain Prairie was once the largest tallgrass prairie in the Southeast. By some accounts it once covered as much as 3.7 million acres of west-central KY, northwestern middle TN, and portions of southern IN. Numerous accounts testify to the Pennyroyal being nearly treeless in the 1790s-1810s. The karst plain has thousands of wet depressions that would have once supported thousands, or more likely tens of thousands, of acres of wet prairies. How much wet prairie existed cannot be known but it is clear that more than 99% of this community has been destroyed.

Present Status

This is perhaps the rarest grassland type in TN. High quality examples are extremely rare and perhaps non-existent outside of Fort Campbell. If any high-quality examples exist at Fort Campbell they have yet to be described. This type should be critically imperiled.

Representative Sites

Montgomery Co., TN: roadside strip between Hwy 41 and CSX railroad (36.627971, -87.139021)

Stewart Co., TN: Fort Campbell Army Base impact zone (36.619340, -87.697441)


Threats

The one site known in TN not on Fort Campbell just southeast of Guthrie has escaped being converted to agricultural fields and succession to forests because it is sandwiched between a highway and an adjacent railroad. This narrow strip, just 40 ft wide at its widest point, faces many significant and constant threats. These include herbicide spraying from both the railroad and from the highway by rail and road maintenance crews. The narrow strip is also subjected to excessive mowing. The small size and long, thin shape (0.8 mi long x 30-40 ft wide) of this remnant makes it susceptible to edge effect, degradation from invasive species, and random events.

On Fort Campbell, most examples of this community are found in the 25,000 acre impact zone, only the southern portion of which is in TN. These examples are unable to be inventoried because the impact zone is strictly off-limits due to presence of unexploded ordnances. The impact zone supports approximately 20,000+ acres of grassland, much of which is dry to submesic grassland/savanna. However, the impact zone has quite a bit of fine-scale topographic variation, including seasonally wet flats and depressions. Most areas of the impact zone burn on an annual basis. Beavers also inhabit the impact zone and are expanding some wetland areas. Thus the grasslands of Fort Campbell represent the nearest thing left to the original prairie that once covered the Pennyroyal.  

Management Considerations

Previous Studies

Chester (___)'s conducted a floristic survey of __ prairies at Fort Campbell but their work focused mostly on upland types. __ of the __ species they documented are wetland species. These are listed below in the floristic list for this community as they are presumed to occur in this community. No quantitative vegetation studies have been conducted specifically for the Pennyroyal Plain prairie system.

Future Research Needs

A focused effort is needed to inventory the wet prairies at Fort Campbell to document their floristic composition as well as to classify the various associations of wet prairie, most of which are likely undescribed. Such work is needed to inform future conservation work in the region, especially restoration and re-creation of Pennyroyal wetlands.

References

Baskin, J.M., Baskin, C.C. and Chester, E.W., 1994. The Big Barrens Region of Kentucky and Tennessee: further observations and considerations. Castanea, pp.226-254.

Chester, E.W., Wofford, B.E., Baskin, J.M. and Baskin, C.C., 1997. A Floristic Study of Barrens on the Southewestern Pennyroyal Plain, Kentucky and Tennessee. Castanea, pp.161-172.

DeSelm, H. R., and N. Murdock. 1993. Grass-dominated communities. Pages 87-141 in: W. H. Martin, S. G. Boyce, and A. C. Echternacht, editors. Biodiversity of the southeastern United States: Upland terrestrial communities. John Wiley and Sons, New York.

DeSelm, H.R., 1994. Tennessee barrens. Castanea, pp.214-225.

Geology available at Tennesse Spatial Data Server which can be found at http://www.tngis.org/geology.html which links to a USGS Water Resources Division site: http://water.usgs.gov/lookup/getspatial?geo250k Tennessee Spatial Data Server site notes: Thanks goes to Jim Julian for researching this improved geology layer from the Tennessee Division of Geology. **Note** - The Tennessee Division of Geology does not endorse this coverage, stating this version is still incomplete and not fit for distribution.Noss,

NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed: March 1, 2015).

Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed [02/25/2015].

USNVC [United States National Vegetation Classification]. 2016. United States National Vegetation Classification Database, V2.0. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC. [usnvc.org] (accessed 27 Dec 2016)

Floristic Checklist 

List adapted from publication by Chester et al. (1997) with supplemental entries provided from survey notes by D. Estes

References

Baskin, J.M., Baskin, C.C. and Chester, E.W., 1994. The Big Barrens Region of Kentucky and Tennessee: further observations and considerations.  Castanea , pp.226-254.

Chester, E.W., Wofford, B.E., Baskin, J.M. and Baskin, C.C., 1997. A Floristic Study of Barrens on the Southewestern Pennyroyal Plain, Kentucky and Tennessee.  Castanea , pp.161-172.

DeSelm, H. R., and N. Murdock. 1993. Grass-dominated communities. Pages 87-141 in: W. H. Martin, S. G. Boyce, and A. C. Echternacht, editors. Biodiversity of the southeastern United States: Upland terrestrial communities. John Wiley and Sons, New York.

DeSelm, H.R., 1994. Tennessee barrens. Castanea, pp.214-225.

Geology available at Tennesse Spatial Data Server which can be found at http://www.tngis.org/geology.html which links to a USGS Water Resources Division site: http://water.usgs.gov/lookup/getspatial?geo250k Tennessee Spatial Data Server site notes: Thanks goes to Jim Julian for researching this improved geology layer from the Tennessee Division of Geology. **Note** - The Tennessee Division of Geology does not endorse this coverage, stating this version is still incomplete and not fit for distribution.Noss,

NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed: March 1, 2015).

Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed [02/25/2015].

USNVC [United States National Vegetation Classification]. 2016. United States National Vegetation Classification Database, V2.0. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC. [usnvc.org] (accessed 27 Dec 2016)

Floristic Checklist 

List adapted from publication by Chester et al. (1997) with supplemental entries provided from survey notes by D. Estes