Research Paper |
Corresponding author: Jordan T. Coscia ( jtcoscia@vt.edu ) Academic editor: Viktoria Wagner
© 2024 Jordan T. Coscia, J. Berton C. Harris, Devin Floyd, Michael C. Beall, David Bellangue, Drew Chaney, Jared Gorrell, Evie Sackett, Ezra J. Staengl, J. Leighton Reid.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Coscia JT, Harris JBC, Floyd D, Beall MC, Bellangue D, Chaney D, Gorrell J, Sackett E, Staengl EJ, Reid JL (2024) Floristics of Virginia’s Northern and Central Piedmont grasslands. Vegetation Classification and Survey 5: 267-278. https://doi.org/10.3897/VCS.126066
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Aims: The grasslands of the North American Piedmont host diverse communities of sun-loving plants, but more than 90% of these grasslands have been lost across the region. Grasslands of the northern and central Piedmont of Virginia have received little formal study, but they are likely to be as diverse and threatened as they are in other parts of the eastern United States. To conserve the remaining Piedmont grasslands, we need to characterize floristic communities, identify the edaphic factors and disturbance regimes that drive their persistence, and develop methods to restore degraded grasslands. Study Area: Northern and Central Virginia Piedmont, USA. Methods: We surveyed plant communities and collected soil samples in 132 grasslands in old fields, powerline clearings, and roadsides. We used cluster analysis, indicator species analysis, and non-metric multidimensional scaling overlaid with soil and environmental variables to identify community groups. Results: We identified 695 plant taxa (87% of which are native) including 13 species that are rare in Virginia, two of which are globally critically imperiled (Pycnanthemum clinopodioides and P. torreyi). Six of our study sites contained 100 or more species with a maximum of 114 species in a single plot, making them among the most species-rich 100 m2 plots recorded in the United States. Cluster analysis and ordination indicated four community groups, which we refer to as the Northern Prairies, Central Prairies, Savanna/Woodlands, and Wet Grasslands. Conclusions: The descriptions of these community groups can be used as reference information to inform grassland restoration in Virginia. Virginia’s Piedmont grasslands are threatened by fire suppression, development, invasive species, and inappropriate management by utility companies. Swift action to conserve high quality grasslands and restore degraded ones is required to save these diverse plant communities.
Taxonomic reference:
Abbreviations: NMDS = non-metric multidimensional scaling; PERMANOVA = permutational multivariate analysis of variance.
biodiversity, cluster analysis, floristics, grassland, ordination, Piedmont grasslands, savanna, Southeastern grasslands, Virginia, woodland
Temperate grasslands are the most threatened biome globally, with high rates of habitat loss and low levels of protection (
Grasslands host an array of plant and animal species, and their conservation and restoration can help address the 53% decline in North American grassland bird populations since the 1970s (
Among the temperate grasslands in need of increased recognition and study are the grasslands of the southeastern United States. These often-overlooked yet old ecosystems range from open tallgrass prairies to extensive savannas to open woodlands, glades, and barrens, all of which were historically common across the South (
Despite their endemic species richness and previous widespread distribution, southeastern grasslands, including those of Virginia’s Piedmont, have lost an estimated 90% of their former range (
To conserve the remaining Piedmont grasslands and to provide a target reference state for grassland restoration efforts, we need to determine the distribution of these grasslands and characterize grassland floristic groups. The Virginia Department of Conservation and Recreation currently classifies the grasslands of the Piedmont as a subtype of the Piedmont Oak-Hickory Woodlands, Savannas, and Grasslands Group, and this subtype description is based on just six open grassland locations and eleven savanna/woodland sites (
To address these knowledge gaps, we located and surveyed high-quality grassland fragments across the northern and central Virginia Piedmont. We predicted that some sites would host diverse plant communities that included rare species. We also predicted that native plant communities would differ across various substrates based on field observations that suggested that soil factors, notably pH and base cation content, may be drivers of grassland persistence, diversity, and variability. Based on these predictions, we aimed to define general vegetation community groupings that can guide future floristic, conservation, and restoration work.
Our study was conducted within a 17-county region within the Piedmont physiographic province in northern and central Virginia (Figure
We identified a pool of potential grassland fragments across the northern and central Virginia Piedmont through a combination of systematic inspections of satellite imagery, structured driving surveys, and consultations with regional botanical experts. From the grassland fragments initially identified, 132 species-rich sites with a predominance of native, helophytic species were selected for vegetation surveys (Figure
Most of the remaining grasslands on the Virginia Piedmont occur in areas with soils that are unsuitable for agriculture and histories of human management or disturbance that enable heliophytic species to persist. Therefore, many of our sites were located in powerline corridors, old fields (e.g. former pastures mowed every 1–3 years, historical battlefields maintained as parks), and roadside rights-of-ways. We did not sample actively hayed or grazed sites, sites known to be planted with native wildflower seed, or sites containing non-native species indicative of commercially available meadow seed mixes such as Echinacea purpurea (purple coneflower) or Coreopsis tinctoria (plains coreopsis).
We sampled the vegetation at each site between June and November with modified Whittaker plots using a method adapted for sampling small, fragmented grasslands (
For the first surveys conducted in the northern Piedmont in 2020, the survey plots were 2 × 50 m (100 m2), and we estimated percent cover within five 1 m2 quadrats evenly spaced every ten meters along the 50 m edge of the plot. Any species found within these plots but outside the quadrats were included in the plot species list. In subsequent surveys conducted in the Central Piedmont in 2021, the survey plots were modified to 4 × 25 m (100 m2), and we estimated percent cover across the entire plot. To standardize the percent cover estimates from within quadrats in 2020 and across the entire plot in 2021, we calculated the average percent cover of each species across all five quadrats in the 2020 data. We converted percent cover into an ordinal cover class variable with ten possible values: 0 = absent, 1 < 0.1%, 2 = 0.1 to 1%, 3 = 1 to 2%, 4 = 2 to 5%, 5 = 5 to 10%, 6 = 10 to 25%, 7 = 25 to 50%, 8 = 50 to 75%, and 9 = 75 to 100%. This cover class scale follows methods used to determine formal floristic types in forests by the Virginia Department of Conservation and Recreation, though we adapted these methods to include a cover class of 0 in this study (
To assess relationships between soil attributes and plant community composition, we aggregated at least five soil cores that were 15 cm deep and 5 cm in diameter. These cores were taken from locations distributed evenly throughout each study plot to create a single soil sample for each study site. We sent these soil samples to Brookside Laboratories, Inc. to analyze for pH, Mehlich III extractable micronutrients, total cation exchange capacity, percent organic matter, estimated nitrogen release, and bulk density (soil testing methods detailed in Suppl. material
We supplemented our field-collected data with soil unit characteristics and topographic information compiled from publicly available databases using the ArcGIS Pro Spatial Analyst package (Version 3.2.0, Esri Inc., Redlands, CA, US). We derived flood frequency and soil drainage class information from the dominant condition data for each soil unit underlying a site in the USDA Soil Survey Geographic Database (
We obtained the elevation of each site in meters from the 30 m National Elevation Dataset (
We conducted all statistical analyses in R using RStudio (R Version 4.4.1
Three sites with an average Bray-Curtis dissimilarity from all other sites greater than 2.5 standard deviations from the mean were considered outliers and were removed prior to multivariate analysis to avoid distortions in the ordination (
To prepare the ArcGIS data for analysis, we converted the categorical variable for soil drainage class to a numeric ordinal variable with higher values corresponding with increasingly poorer drainage. Flood frequency was similarly transformed, with higher values corresponding to more frequent flooding. These ordinal variables were converted to interval-scaled variables for analysis. The distributions of the continuous soil and geological variables were examined and transformed to linear distributions if necessary to correct for strong positive or negative skew. The variables estimated soil N release (#N/acre), soil bulk density (g/cm3), and relative forb cover were squared. The variables slope, soil P content (mg/kg), soil K content (mg/kg), soil Mg content (mg/kg), soil Zn content (mg/kg), soil Mn content (mg/kg), and soil Ca content (mg/kg) were natural-log-adjusted. The variables relative woody cover and relative graminoid cover were square-root-adjusted. The variables elevation (m), soil pH, soil organic matter content (%), soil Al content (mg/kg), and total cation exchange capacity (meq/100g) were cube-root-adjusted. The variables soil Na content (mg/kg), soil Cu content (mg/kg), soil S content (ppm), soil Fe content (mg/kg), and soil B content (mg/kg) were arctangent adjusted.
Species of conservation concern and the number of study sites at which they were recorded. A rank of S3 indicates that a species is uncommon in Virginia (20–50 sites state-wide), a rank of S2 indicates that a species is rare in Virginia (5–20 sites state-wide), while a rank of S1 indicates that a species is critically rare in Virginia (1–5 sites state-wide) (
Scientific Name | Common Name | State Rank | Global Rank | Number of Sites | Average Cover Class |
---|---|---|---|---|---|
Symphyotrichum ericoides var. ericoides | white heath aster | S3 | G5T5 | 10 | 3.00 |
Pycnanthemum torreyi | Torrey’s mountain-mint | S2 | G2 | 6 | 3.00 |
Pycnanthemum clinopodioides | basil mountain-mint | S1 | G1G2 | 3 | 4.33 |
Gymnopogon brevifolius | short-leaf beard grass | S3 | G5 | 2 | 5.50 |
Agrostis scabra | rough bentgrass | S3? | G5 | 1 | 3.00 |
Asclepias purpurascens | purple milkweed | S3 | G5? | 1 | 1.00 |
Baptisia australis | blue wild indigo | S3 | G5 | 1 | 3.00 |
Desmodium canadense | showy tick-trefoil | S1 | G5 | 1 | 1.00 |
Dichanthelium annulum | ringed panicgrass | S3 | G4 | 1 | 4.00 |
Dichanthelium ravenelii | Ravenel’s rosette grass | S3 | G5 | 1 | 2.00 |
Hexastylis lewisii | Lewis’ Heartleaf | S3 | G3 | 1 | 4.00 |
Solidago rigida var. rigida | stiff goldenrod | S2 | G5T5 | 1 | 1.00 |
Tragia urticifolia | nettle-leaf noseburn | S3 | G5 | 1 | 4.00 |
To classify sites into plant community groups, we conducted a hierarchical, agglomerative cluster analysis using the R package cluster function agnes() using Bray-Curtis dissimilarity and a flexible linkage method using par.method = 0.625 (
Following cluster analysis, we conducted indicator species analysis to identify characteristic species within each grassland group. Analysis was run using the R package indicspecies function multipatt() with the IndVal.g test statistic based on the Indicator Value index of
To examine the separation of the grassland groups produced by the cluster analysis, we visualized the groups in multivariate space using non-metric multidimensional scaling (NMDS) ordinations of our species matrix. We created all NMDS ordinations with the R package vegan function metaMDS using Bray-Curtis dissimilarity and 100 random starts (
To assess which soil and environmental gradients correlated with the results of the NMDS ordination, we projected soil and environmental variable gradients onto our selected ordination using the R package vegan function envfit() with 100 permutations (
We identified 695 species, subspecies, and varieties of plants across all study sites (Suppl. material
Cluster analysis indicated four broad grassland community groups (PERMANOVA P < 0.001, R2 = 0.19, Figure
(A) Dendrogram of the four major grassland groups produced by the hierarchical agglomerative cluster analysis of 129 sites. The four major groups were supported by PERMANOVA (P < 0.001, R2 = 0.19). (B) Northern Prairie site in Prince William County, VA photographed by JBCH. (C) Central Prairie site in Albemarle County, VA photographed by DF. (D) Savanna/Woodland site in Madison County, VA photographed by DC. (E) Wet Grassland site in Buckingham County, VA photographed by DC.
Number of sites and average species richness and relative cover classes for each grassland group.
Group | Number of Sites | Average Species Richness ± Standard Error | Average Relative Graminoid Cover | Average Relative Forb Cover | Average Relative Woody Plant Cover |
---|---|---|---|---|---|
Northern Prairie | 36 | 61.22 ± 2.18 | 0.31 ± 0.01 | 0.50 ± 0.01 | 0.19 ± 0.01 |
Central Prairie | 50 | 67.49 ± 2.07 | 0.30 ± 0.01 | 0.53 ± 0.01 | 0.17 ± 0.01 |
Savanna/Woodland | 32 | 74.25 ± 3.56 | 0.22 ± 0.01 | 0.47 ± 0.02 | 0.30 ± 0.02 |
Wet Grassland | 11 | 67.55 ± 4.65 | 0.36 ± 0.02 | 0.46 ± 0.02 | 0.18 ± 0.03 |
The top five indicator species with the highest indicator values for each group are listed in Table
Group | Scientific Name | Common Name | Specificity | Fidelity | Indicator Value | P Value |
---|---|---|---|---|---|---|
Northern Prairie | Sorghastrum nutans | Indiangrass | 0.60 | 0.78 | 0.68 | 0.001 |
Carex bushii | Bush’s sedge | 0.87 | 0.50 | 0.66 | 0.001 | |
Poa cuspidata | early bluegrass | 0.85 | 0.44 | 0.62 | 0.001 | |
Chamaecrista fasciculata | partridge pea | 0.74 | 0.39 | 0.54 | 0.002 | |
Strophostyles umbellata | pink fuzzybean | 0.79 | 0.36 | 0.53 | 0.005 | |
Central Prairie | Carex glaucodea | blue sedge | 0.83 | 0.48 | 0.63 | 0.001 |
Andropogon gyrans | Elliott’s bluestem | 0.68 | 0.52 | 0.59 | 0.002 | |
Andropogon ternarius | splitbeard bluestem | 0.76 | 0.28 | 0.46 | 0.015 | |
Solidago pinetorum | Small’s goldenrod | 0.90 | 0.22 | 0.45 | 0.013 | |
Aristida dichotoma | churchmouse threeawn | 0.89 | 0.20 | 0.42 | 0.016 | |
Savanna/ Woodland | Dichanthelium boscii | Bosc’s panicgrass | 0.89 | 0.66 | 0.77 | 0.001 |
Carya glabra | pignut hickory | 0.80 | 0.66 | 0.73 | 0.001 | |
Prunus serotina var. serotina | black cherry | 0.67 | 0.63 | 0.65 | 0.001 | |
Clitoria mariana var. mariana | butterfly pea | 0.89 | 0.41 | 0.60 | 0.001 | |
Quercus velutina | black oak | 0.66 | 0.53 | 0.59 | 0.004 | |
Wet Grassland | Eupatorium perfoliatum | common boneset | 0.93 | 1.00 | 0.96 | 0.001 |
Dichanthelium microcarpon | branched panicgrass | 0.83 | 0.91 | 0.87 | 0.001 | |
Juncus effusus | common rush | 0.89 | 0.82 | 0.86 | 0.001 | |
Carex lurida | shallow sedge | 1.00 | 0.73 | 0.85 | 0.001 | |
Persicaria sagittata | arrowleaf tearthumb | 1.00 | 0.73 | 0.85 | 0.001 |
The selected NMDS solution was built on three axes (stress = 0.16, non-metric fit R2 = 0.98, linear fit R2 = 0.87; Figure
Scatterplot of the NMDS ordination in three dimensions (stress = 0.16, non-metric fit R2 = 0.98, linear fit R2 = 0.87). Point shapes and colors indicate the four groups: Northern Prairie, Central Prairie, Savanna/Woodland, and Wet Grassland. Overlaid arrows depict the environmental variables with R2 values greater than 0.25 and P values less than 0.05, with the exceptions of slope (degrees) and soil P content (mg/kg), which nearly overlapped with relative woody cover and soil organic matter content (%), respectively, were removed for legibility (Table
Average values ± standard error and fit of each soil and environmental variable to the NMDS ordination. Group averages were calculated using untransformed data, while variable fitting to the NMDS was performed using transformed data.
Variable | Northern Prairie | Central Prairie | Savanna/Woodland | Wet Grassland | R2 | P Value |
---|---|---|---|---|---|---|
Organic Matter Content (%) | 4.47 ± 0.27 | 4.4 ± 0.17 | 7.57 ± 0.55 | 5.03 ± 0.96 | 0.48 | 0.01 |
Relative Woody Cover | 0.19 ± 0.01 | 0.17 ± 0.01 | 0.3 ± 0.02 | 0.18 ± 0.03 | 0.46 | 0.01 |
Elevation (m) | 116.08 ± 9.55 | 136.98 ± 4.29 | 176.71 ± 9.21 | 138.35 ± 7.26 | 0.44 | 0.01 |
Relative Graminoid Cover | 0.31 ± 0.01 | 0.30 ± 0.01 | 0.22 ± 0.01 | 0.36 ± 0.02 | 0.42 | 0.01 |
Fe (mg/kg) | 139.43 ± 7.96 | 186.02 ± 10.87 | 176.91 ± 9.22 | 367.73 ± 35.67 | 0.37 | 0.01 |
K (mg/kg) | 61.43 ± 7.27 | 69.65 ± 6.51 | 78.88 ± 6.73 | 42.45 ± 10.68 | 0.33 | 0.01 |
P (mg/kg) | 9.14 ± 2.14 | 8.04 ± 0.66 | 14.61 ± 3.17 | 8.36 ± 1.70 | 0.32 | 0.01 |
Slope (degrees) | 2.37 ± 0.38 | 2.32 ± 0.19 | 6.49 ± 0.84 | 3.21 ± 0.59 | 0.31 | 0.01 |
Mn (mg/kg) | 129 ± 21.45 | 65.45 ± 8.72 | 81.66 ± 12.37 | 39.73 ± 8.05 | 0.27 | 0.01 |
Bulk Density (g/cm3) | 1.05 ± 0.02 | 1.00 ± 0.01 | 0.90 ± 0.02 | 0.85 ± 0.05 | 0.24 | 0.01 |
Topographic Position Index | 1.11 ± 0.53 | 1.70 ± 0.63 | 4.69 ± 1.20 | -3.26 ± 0.87 | 0.23 | 0.01 |
Al (mg/kg) | 709.00 ± 31.10 | 784.43 ± 29.68 | 854.22 ± 53.34 | 605.64 ± 71.01 | 0.22 | 0.01 |
Relative Forb Cover | 0.50 ± 0.01 | 0.53 ± 0.01 | 0.47 ± 0.02 | 0.46 ± 0.02 | 0.21 | 0.01 |
Drainage Class | 4.47 ± 0.22 | 3.22 ± 0.09 | 3.03 ± 0.12 | 3.30 ± 0.50 | 0.20 | 0.01 |
B (mg/kg) | 0.27 ± 0.02 | 0.35 ± 0.03 | 0.37 ± 0.03 | 0.52 ± 0.04 | 0.19 | 0.01 |
Cu (mg/kg) | 1.82 ± 0.19 | 1.33 ± 0.17 | 1.47 ± 0.20 | 2.97 ± 1.43 | 0.19 | 0.01 |
pH | 5.65 ± 0.11 | 5.22 ± 0.06 | 5.26 ± 0.12 | 5.17 ± 0.10 | 0.18 | 0.01 |
Na (mg/kg) | 24.29 ± 3.70 | 13.37 ± 0.66 | 13.34 ± 0.9 | 55.91 ± 36.02 | 0.13 | 0.01 |
Cation Exchange Capacity (meq/100g) | 10.73 ± 1.51 | 7.54 ± 0.56 | 9.26 ± 0.57 | 5.94 ± 1.33 | 0.11 | 0.02 |
Flood Frequency Class | 1.31 ± 0.15 | 1.06 ± 0.03 | 1.09 ± 0.09 | 1.20 ± 0.20 | 0.08 | 0.02 |
Zn (mg/kg) | 4.14 ± 2.27 | 6.51 ± 1.18 | 4.30 ± 0.56 | 16.08 ± 11.06 | 0.03 | 0.31 |
Species Richness | 61.22 ± 2.18 | 67.49 ± 2.07 | 74.25 ± 3.56 | 67.55 ± 4.65 | 0.03 | 0.42 |
Estimated N Release (#N/acre) | 92.71 ± 2.58 | 88.22 ± 3.17 | 91.06 ± 7.22 | 92.73 ± 4.87 | 0.02 | 0.45 |
The Northern Prairie group was named for its restriction to the northern Virginia Piedmont. In comparison to the other subgroups, Northern Prairie sites have somewhat more basic soils with notably higher Mn contents. The northern character of this group is reinforced by the presence of Carex bushii (Bush’s sedge), a sedge that is most frequently found in Northern Virginia, as its second-strongest indicator species.
Likewise, the Central Prairie group was named for its restriction to the central Virginia Piedmont. Though there are indications that this subgroup could extend to the southern Virginia Piedmont as well, this will need to be confirmed by future studies. In contrast to the Northern Prairie group, the strongest indicator species for the Central Prairie group include species such as Solidago pinetorum (Small’s goldenrod) and Andropogon ternarius (splitbeard bluestem) that are common in the central and southern Piedmont but infrequent in the northern Piedmont. Furthermore, the Central Piedmont sites were correlated with intermediate values for many soil and environmental variable gradients in our analyses in comparison to sites from the other three groups.
The Savanna/Woodland group, the group with the highest average species richness of over 74 species per 100 m2 study plot, was named for the prevalence of woodland and woody species in its indicator species list and the high average relative woody cover classes among its study sites. Though our study plots did not contain adult trees due to the routine mowing of the roadside rights-of-way, powerline corridors, and old fields that comprised the majority of our sites, the herbaceous and shrubby vegetation in these plots contain many species with affinities for woodland habitats despite the lack of woodland structure. Three of the top five indicator species for this group, Carya glabra (pignut hickory), Prunus serotina var. serotina (black cherry), and Quercus velutina (black oak) are trees, while another top indicator species, Dichanthelium boscii (Bosc’s panicgrass), is often found in woodlands and forests. In addition to higher average relative woody cover classes, Woodland/Savanna study sites were correlated with higher elevations, steeper slopes, and had the highest average topographic position index value of 4.69 ± 1.20 among the four groups, indicating that the Woodland/Savanna group grasslands are associated with slopes and uplands.
Finally, the Wet Grassland group was named for both the prevalence of wet-soil tolerant species in its indicator species list and for the correlation of its sites with characteristics indicative of wet habitats along the soil and environmental variable gradients. All five of its top indicator species are frequently found in or restricted to wet habitats such as floodplains, swamps, wet meadows, and other low habitats. The Wet Grassland group has the only negative average topographic position index of -3.26 ± o.87, indicating that its sites are found in low-lying areas such as seeps and depressions. Wet Grassland sites also had notably higher soil Fe and Zn content than sites from the other three subgroups.
Our study provides an initial synopsis of the floristic composition and variability of Virginia’s most diverse and least studied ecological community. In our surveys of grassland fragments across the northern and central Virginia Piedmont, we have documented 604 native taxa in 132 survey sites. Many of these sites have notably high species richness: six of our study sites have 100 species or more within a single 100 m2 plot, with a maximum of 114 species. We have distinguished four major community groups among our study sites, which we refer to as the Northern Prairies, the Central Prairies, the Savanna/Woodlands, and the Wet Grasslands. Each group has distinctive species composition and edaphic characteristics that should be considered in future conservation and restoration efforts in these threatened habitats.
We documented 695 taxa across our study sites, which represent over 21% of the 3,164 species documented in the Flora of Virginia (
Six of our study sites had survey plots containing over 100 species, making these plots some of the most species-rich 100 m2 plots recorded in the state of Virginia. Furthermore, our six plots may be among the most species-rich 100 m2 plots recorded across the entire United States: of the 4,773 100 m2 plots from the United States with publicly available data on VegBank at the time of writing, only six plots contained over 100 species, with a maximum of 129 species (
With their high species richness and the presence of threatened endemic species, our study sites are pockets of biodiversity threatened by a changing climate and landscape (
The current community type description for the Piedmont Oak-Hickory Woodlands, Savannas, and Grasslands defined by the Virginia Department of Conservation and Recreation describes the herb layer of these habitats as “highly variable in both density and composition” and notes the presence of Schizachyrium scoparium var. scoparium (little bluestem), Sorghastrum spp. (indiangrasses), Andropogon spp. (broomsedges), Danthonia spicata (poverty oatgrass), Desmodium spp. (tick-trefoils), Lespedeza spp. (bush-clovers), Eupatorium spp. (thuroughworts), and Solidago spp. (goldenrods), particularly Solidago nemoralis var. nemoralis (gray goldenrod) and S. juncea (early goldenrod) (
Our evidence suggests that there are at least four broad grassland community groups in the northern and central Virginia Piedmont. This expands the current description of Piedmont grasslands as a subtype of the Piedmont Oak-Hickory Woodlands, Savannas, and Grasslands Group defined by the Virginia Department of Conservation and Recreation, whose ability to survey the powerline, roadside, and battlefield sites that comprise the majority of our study has been limited by their designation as Seminatural/Modified landscapes under the U.S. National Vegetation Classification (
By defining the floristic and environmental variation, our study can provide more accurate guidelines and define more detailed community composition and species richness goals to guide conservationists and restoration practitioners who manage native grasslands across Virginia. In the time since we have conducted our surveys, we have witnessed the degradation of several of our study sites. A population of the state-rare Solidago rigida var. rigida (stiff goldenrod) was sprayed with herbicide in a powerline clearing in Prince William County, and a population of the globally imperiled Pycnanthemum torreyi (Torrey’s mountain-mint) was eliminated by the construction of a sidewalk in Albemarle County. These incidents exemplify the threats of habitat loss and degradation faced by grasslands across the Southeast. With habitat loss and destruction rates of 90–100% across their historic range, improving the management of known high quality Southeastern grasslands is an urgent priority (
The native grasslands of the Southeastern United States are among the most diverse and threatened habitats in the country, yet they are understudied and largely unprotected. We need to increase recognition of their ecological value to encourage their conservation and restoration. Through our surveys of species-rich grassland fragments in the northern and central Virginia Piedmont, we have found evidence of at least four grassland community groups in need of further description and documentation. By defining these groups, we can promote the conservation of their endemic biodiversity and create more nuanced reference models for the ecological restoration of degraded Piedmont grassland landscapes.
The data and code used in the preparation of this manuscript (with site locations expunged for the protection of rare species) are openly available in the Virginia Tech Data Repository (http://data.lib.vt.edu/) at DOI https://doi.org/10.7294/25267117.
J.B.C.H., D.F., J.L.R., and J.T.C. designed the study; all authors collected field data. J.T.C. compiled supplementary GIS data, conducted analyses, and wrote the first draft of the manuscript. All authors edited the manuscript.
We thank the staff and volunteers at the Piedmont Discovery Center, the Clifton Institute, and Virginia Working Landscapes for their efforts in site selection and data collection. This research would not have been possible without the Piedmont Discovery Center staff, who contributed hundreds of hours to site identification and survey. We also thank the private landowners who generously allowed us to survey grasslands on their properties. Special thanks to Gary P. Fleming for assistance on selecting study sites, identifying voucher specimens, and providing guidance and feedback on early drafts of the manuscript. Work at Manassas National Battlefield and in Fairfax County Parks was done under the relevant research permits. Funding was provided by the Virginia Native Plant Society, the Piedmont Discovery Center, the Virginia Tech College of Agriculture and Life Sciences.
Scree, stress, and scatter plots for the selected NMDS solution. (*.pdf)
Species lists for each of the four grassland types. (*.pdf)