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Western Highland Rim Wet Meadow

Synonyms

South-Central Interior Small Stream & Riparian Ecological System (NatureServe 2015)

Distribution

Western Middle Tennessee (Cheatham, Davidson, Dickson, Giles, Hickman, Houston, Humphreys, Lawrence, Lewis, Maury, Montgomery, Perry, Stewart, Wayne, Williamson) where restricted to narrow floodplains of stream valleys.

Vegetation Description

Sedges, grasses, forbs, and scattered shrubs dominate this small patch community that ranges in height from 0.25 – 1.5 m with some shrubs up to 3-4 m. Scattered shrubs may be present in the interior of these meadows but are especially abundant on the margins toward nearby streams. Today, these occur as scattered meadows in sometimes long, narrow stream valleys where individual meadows are isolated. Historically, meadows probably were maintained by beavers, grazing and browsing megafauna such as bison and elk, and Indian-set fires.

Physical Characterization

This community occurs in the Dissected Western Highland Rim ecoregion (Estes & Fleming 2015) in valleys of small to medium-sized creeks. The meadows are either in the active floodplain (tread) or on slightly elevated terraces at elevations ranging from 103-225 m (340-740 ft). The streams may be meandering or sinuous, but presumably when beavers were common they would have had meandering and probably braided channels. Slopes generally are flat and 0-2%. The bedrock geology is composed of Paleozoic Mississippian-aged limestone and chert of the _______ formation. A thick layer of alluvium overlies the bedrock in these stream valleys.

Soils are thermic Fluvaquentic Endoaquepts derived from gravelly, loamy alluvium weathered from cherty limestone. They are deep, poorly drained (but lacking ponding) with high water table at 0-12 inches deep. pH is moderately to strongly acid in some examples to slightly acid to circumneutral in others. 

Soil series involved:

Natural Processes

These wetlands are likely supplied by two hydrologic sources. The primary source is from groundwater seepage, percolating from adjacent limestone and shale formations that form the hills bordering the stream valleys. For this reason, most of these wetlands qualify as slope wetlands in spite of their relatively flat surface. Their proximity to small streams also makes them prone to periodic overbank flooding, which in the WHR most often occurs in winter and spring. Unlike beaver ponds and associated marshes which were probably historically linked to these meadows, this community rarely has standing water and in drier portions of the year it may be somewhat dry at the surface even though the water table is still relatively high. Due to this periodic dry phase, these meadows are able to be mowed occasionally, keeping many sites free of trees and dominated by graminoids, forbs and shrubs.

Data from Revolutionary War land grant surveys (1779-1804) from the easternmost edge of the WHR (western portions of Cheatham, Williamson, and Maury counties, and eastern sections of Lewis Co.) indicate that some of the narrow floodplains of streams exiting the WHR to the Outer Nashville Basin were not forested at the time of earliest Euroamerican occupation. Some early land survey boundaries in these valleys used "stakes" instead of trees as markers providing evidence that these valleys had openings. In nearby locations, sometimes other markers of the same tract, trees typical of mesic forests were used as marker trees (especially sycamore, elm

Today, these meadows are kept open by periodic mowing but prior to the advent of mechanized mowers they were likely maintained by beaver and megaherbivores (possibly also fire), followed by European livestock, and finally by periodic mowing. Prior to European settlement of the area in the late 1790s-1820s, they may have been maintained by a combination of Indian-set fires and grazing and browsing by bison and elk. Beaver may have played the greatest role in maintaining meadow communities in Tennessee. It is possible that beaver-created wetlands once covered much of the floors of these valleys, with a mosaic of beaver ponds, sedge-grass-herb meadows, shrub wetlands, riparian forest and woodlands, and bottomland forests. Like most areas of the eastern U.S. beavers were trapped in large numbers by the French, Indians, and English prior to 1800, long before naturalists had a chance to document their role and their abundance. More research is needed to investigate the historical importance of beavers across Tennessee.

Dominant Plants

Shrubs: Amorpha fruticosa (wild indigo bush), Cephalanthus occidentalis (buttonbush), Cornus amomum (silky dogwood), Salix sericea (silky willow). Herbaceous Layer: Carex frankii (Frank's sedge), C. lurida (lurid sedge), C. normalis (normal sedge), C. vulpinoidea (fox sedge), Coleatania rigidulum (___), Cyperus strigosus (____), Dichanthelium dichotomum var. ramulosum (cypress panic grass), Dichanthelium scoparium (___), Helenium autumnale (autumn sneezeweed), Hibiscus moscheutos (___), Juncus coriaceus (leathery rush), Juncus effusus (___), Scirpus atrovirens (green bulrush), S. georgianus (Georgia bulrush), Solidago gigantea (late-flowering goldenrod), Symphyotrichum lanceolatum (white panicled aster).

Characteristic Plants

Boehmerica cylindrica (false nettle), Chelone glabra (smooth turtlehead), Cirsium muticum (swamp thistle),  Cuscuta compacta (compact dodder), Epilobium coloratum (purpleleaf willowherb), Eupatorium perfoliatum (boneset), Hymenocallis caroliniana (Carolina spider lily), Leersia oryzoides (rice cutgrass), Oxylepis rigidior (cowbane), Platanthera peramoena (purple fringeless orchid), Solidago patula (roughleaf goldenrod), S. rugosa (wrinkle-leaf goldenrod), Thelypteris palustris (marsh fern)

Restricted or Noteworthy Plants

Lilium michiganense (Michigan lily); Pedicularis lanceolata (swamp lousewort)

Invasive Species

Arthraxon hispidus (hairy jointgrass)

Community Variation and Subtypes
These community appears to be undescribed in the National Vegetation Classification. The closest matches found in the NVC are provided in the table below, though both seem to describe marshes with standing water associated with beaver impoundments, whereas these meadows are in fact wet-mesic grasslands.

CEGL004112 Juncus effusus Seasonally Flooded Herbaceous Vegetation G5
Common Rush Marsh
Common Rush Seasonally Flooded Herbaceous Vegetation
CEGL004290 Polygonum (hydropiperoides, punctatum) - Leersia spp. Herbaceous Vegetation G4?
Smartweed - Cutgrass Beaver Pond
(Swamp Smartweed, Dotted Smartweed) - Cutgrass species Herbaceous Vegetation

Within the known higher quality examples of this community there are a number of different associations that have been observed but not yet described. These include the following tentative groupings:

Associated Natural Communities

Western Highland Rim Beaver Pond, Western Highland Rim Small-Stream Floodplain Forest, Western Highland Rim Riparian Forest

Similar Communities

Naturally this wetland communtiy bears floristic similarity to other wet meadow communties, particularly those in the adjacent Transition Hills ecoregion, Eastern Highland Rim, and Ridge and Valley. These communities share a number of species in common with calcareous fens.

Presettlement Distribution and Size

The pre-settlement distribution and acreage of this community is not known. A decent estimate can perhaps be gained from determining the acreage of the wetland soils that support this community though that would likely be an overestimate.

Present Status

The current distribution and extent of this community is almost certainly greatly reduced from presettlement times, probably by more than 90%. This community is highly imperiled and only a few good examples are known. High-quality sites are extremely rare.

Representative Sites

Lawrence Co.: private property near Fall River community (35.131483, -87.221307)

Stewart Co.: Land Between the Lakes National Recreation Area (36.507709, -87.985121); (36.570474, -87.933337)

Williamson Co.: private property near Fairview (36.014079, -87.098098)

Threats

This community is highly threatened from wetland drainage and filling, dredging for floodplain gravels and topsoil, too-frequent mowing, invasive species, and succession to forested wetlands. The lack of recognition of this community as a "natural" vegetation type, as evidenced by the lack of matching communities in NatureServe Explorer and the National Vegetation Classification, is harmful to the long-term conservation of this community because it is essentially "out of sight, out of mind" as a natural vegetation type. This is probably because of the current bias towards forested wetlands which has led many of these sites to be so-called "improved" by the planting of trees in an ill-informed attempt to create more forested wetland acreage.

Management Considerations

Though baseline floristic, vegetation, and ecological research is lacking for this community, management for the health of the community should probably consider restoration of natural hydrology (with beavers where possible), prescribed fire, and removal of invasive species (if present). Where possible, attempts should be made to restore large sections of small-stream floodplains. The small stream floodplains where this community is found are particularly susceptible to yearly flooding and is a complicating factor for county highway/road departments. Each year counties within the WHR ecoregion have to spend large amounts of money to repair roads after floods. Long-term, large-scale restorations of floodplain meadow communities involving beaver may not be practical in many places because beaver impoundments may exascerbate problems with flooding and road maintenance.

Future Research Needs

Baseline data on the flora and vegetation structure of WHR meadows is needed similar to the recent floristic inventory of Western Highland Rim Calcareous Seeps and Fens by Redden (2017). This community was sampled by Chester (___) in his flora of Land Between the Lakes Natl. Rec. Area and by Estes (2005) in his Flora of Giles County. No known vegetation studies have been conducted in these meadows. Paleovegetation studies of sediments in stream floodplains could be informative in elucidating long-term vegetation changes in WHR valleys but it isn't known to the author whether these stream systems have been stable to allow for reconstruction of vegetation changes. Similar studies of soil charcoal might, or might not, prove useful in determining the importance of fire in the region. Additional research is needed to evaluate the historical role that beavers, megafauna, and Indian burning played in maintaining floodplains. It would be interesting to know whether LIDAR technology could be useful in determining historical presence of beaver wetland complexes, old channels, etc. Lastly, more work is needed to study land survey records post-1804 to determine the extent to which floodplains were open at first settlement by Eureopeans.

Previous Studies

Studies of meadow communities and historical descriptions are available for meadows in other parts of the eastern U.S., especially from New England (___), Ohio (___), and southeastern Canada (___), where beavers have been implicated in their presence and maintenance.

In contrast, no studies have been conducted that focus solely on meadow communities in Tennessee. Neel (1914) describes what he called "glades" or ____ from the Cumberland Plateau near Crossville. Many of these sites were presumably associated with streams today named Glade Branch or Meadow Branch. 

Baseline data on the flora and vegetation structure of WHR meadows is needed similar to the recent floristic inventory of Western Highland Rim Calcareous Seeps and Fens by Redden (2017). Unfortunately, descriptions and studies of WHR meadows have not been conducted. DeSelm (1988, 1994) did not mention any floodplain meadow communities in his description of grasslands (barrens) of the Western Highland Rim. DeSelm and Murdock (1993) ______. A few examples of community were sampled by Chester and Estes in their fieldwork to document the flora of Land Between the Lakes Natl. Rec. Area (Chester et al. 2002) and Giles County, Tennessee (Estes 2005), but these studies were not focused on this community. A basic description of this community was provided by Estes (2005).

References

Chester, E.W., Jensen, R.J. and Schibig, J., 2002. The flora of Land Between the Lakes: a review. Land Between the Lakes Kentucky and Tennessee: four decades of Tennessee Valley Authority Stewardship. Center for Field Biology, Austin Peay State University, Clarksville, TN, pp.251-265.

DeSelm, H.R., 1988. The barrens of the western Highland Rim of Tennessee. In D.H. Snyder ed.,, Proceedings of the first annual symposium on the natural history of the lower Tennessee and Cumberland river valleys. Austin Peay St. University, Center for Field Biology, Clarksville, TN (pp. 199-219).

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.

Estes, D., 2005. The vascular flora of Giles County, Tennessee. SIDA, Contributions to Botany, pp.2343-2388.

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, R. F. 2013. Forgotten grasslands of the South: Natural history and conservation. Island Press, Washington, DC. 317 pp.

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).

Redden, J. 2017. Vascular flora of Western Highland Rim Seepage Fens. Master's thesis, Austin Peay State University, Clarksville, TN.

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 compiled by surveys by D. Estes