SCP is a 2,448 ha (6,050 ac) tract located between 34.566° and 34.611°N and 77. 614° and 77.720°W in northeastern Pender County, North Carolina, with a small portion extending approximately 0.3 km into Onslow County (Fig. 1). The geographic center of the site is approximately 8.3 km south-southeast of Maple Hill, NC and 21 km northwest of the nearest point in the Atlantic Ocean. The site lies in the outer Coastal Plain ecophysiographic province and within the Cape Fear Arch geological uplift, a region extending from southeastern North Carolina into northeastern South Carolina that is characterized by unusual outcroppings of Cretaceous deposits. This area supports a suite of at least forty-four endemic or near-endemic plant taxa, many of which are rare (LeBlond 2001).

Figure 1.  

Location of areas included in this study. The striped portion designates areas within two miles of Shaken Creek Preserve. Three primary sites—Sandy Run Savannas State Natural Area, Shaken Creek Preserve, and the northern portion of Holly Shelter Gamelands—are labeled in bold. The individual tracts that comprise Sandy Run are labeled with the following abbreviations: H = Hancock, HR = Haw’s Run, N = The Neck Savanna, O = O’Berry, P = Patterson, R = RMK. Baseline imagery from Bing Maps Road, courtesy of Environmental Systems Research Institute (ESRI) (2011).

A small portion of SCP extends to the south of Shaken Creek, which otherwise forms the southern boundary of the property. The northeastern boundary follows Shelter Swamp Creek, while Flo Road west of its intersection with Williams Road forms the northwestern boundary (Fig. 2). With a small exception in the extreme northwest corner of the property, Long Ridge Road outlines the western property boundary. The irregular eastern boundary does not consistently follow any natural features or landmark. SCP is bordered to the southwest by Holly Shelter Gameland; to the northeast by Haw’s Run Mitigation Site, a future component of Sandy Run Savannas State Natural Area; and in other directions by private land. Primary access is south along Williams Road from NC Highway 50, though the site is not openly accessible to the public.

Figure 2.  

Aerial photograph of Shaken Creek Preserve with main roads labeled. Baseline imagery from Bing Maps Aerial, courtesy of Environmental Systems Research Institute (ESRI) (2011).

Sandy Run Savannas State Natural Area (“Sandy Run”) is a 1,214 ha (3,000 ac) site north of SCP (Fig. 1). It is comprised of seven tracts, six of which are currently owned by the NC Division of Parks and Recreation. One tract, Haw’s Run Mitigation Site, which abuts the northeastern portion of SCP, is currently owned by the NC Department of Transportation; however, transfer of this parcel to the NC Division of Parks and Recreation is impending. The various tracts comprising Sandy Run have experienced different management and land use histories, creating an array of habitats including several high-quality savannas and flatwoods. The flora of Sandy Run was recently inventoried by Taggart (2010). Though some portions of Sandy Run are slightly farther than two miles from SCP, vouchers or reports from all Sandy Run tracts were included in this work.

Holly Shelter Game Land is a 26,200 ha (64,742 ac) property south of SCP (Fig. 1). It is owned by the NC Wildlife Resources Commission, which manages the land for public outdoor recreation, particularly hunting and fishing. Only the northeast portion of the property lies within two miles of SCP; as such, plant vouchers or reports from other areas of Holly Shelter are not included in this work.

Prior to its purchase by The Nature Conservancy, the land comprising SCP was owned mostly by members of the Wallace Deer Club, a private hunting group established in the 1920s. The site was virtually unknown to scientists until 1997, when William Blanchard, a member of the Wallace Deer Club and part owner of the land, introduced it to Hervey McIver, a land manager and project coordinator with The Nature Conservancy. With permission from Blanchard, McIver and Richard LeBlond, then a botanist with the NC Natural Heritage Program, undertook the first preliminary surveys of the area and realized quickly that the site contained exceptionally high-quality savannas and numerous rare species. At the time, McIver was working with Blanchard to complete a deed to The Nature Conservancy for fifty acres Blanchard owned in the nearby Neck Savanna, now a tract within Sandy Run Savannas State Natural Area. Blanchard suggested that the land now comprising SCP should also be permanently conserved and eventually agreed to sell his shares of the property. However, purchasing SCP required not just the approval of Blanchard, but of all the approximately fifty landowners who inherited or purchased property rights to the site. After three years of negotiations, The Nature Conservancy closed on the property in 2007. Members of the Wallace Deer Club retained hunting rights to the property, but the site is now owned and managed by The Nature Conservancy.

The excellent quality of many of the savannas on site, as evidenced by the abundance of rare species, the high species richness, and the absence of invasive species, can be directly attributed to the Wallace Deer Club, whose members frequently burned particular areas in order to maintain both the hunting quality and the aesthetic of the land. Evidence of disturbances other than fire in the savannas and flatwoods on site is limited to a few ditches and occasional “borrow pits”, relatively small holes dug to “borrow” the soil in order to regrade and maintain the dirt roads on the property. Based on the size of the canopy trees, many savannas and flatwoods appear to have been logged as recently as the 1980s, though few or no effects on the ground layer are apparent today. Overall, the habitat quality of the site (especially those areas historically burned by members of the hunting club) remains excellent (LeBlond 2000).

The climate at SCP is warm, temperate, and humid for much of the year. The nearest weather station is approximately 29 km away in Jacksonville (Onslow County: 34.7°N, 77.383°W) at 4.9 m above sea level. Over the thirty-year period from 1971 to 2000, the average annual temperature was 17.1 °C, with a mean annual precipitation of 1,397 mm. Average daily maximum temperature was 23.1 °C, and average daily minimum temperature was 11 °C (State Climate Office of NC, http://www.nc-climate.ncsu.edu/; Fig. 3a). The next closest weather station is approximately 35 km away in Willard (Pender County: 34.661°N, 78.046°W) at 16.7 m above sea level. Over the thirty-year period from 1971 to 2000, the average annual temperature was 17.7 °C, with a mean annual precipitation of 1,377 mm. Average daily maximum temperature was 24.2 °C, and average daily minimum temperature was 11.1 °C (State Climate Office of NC, http://www.nc-climate.ncsu.edu/; Fig. 3b). For both stations, monthly average temperatures were highest in July and August and lowest in January and February. Monthly precipitation amounts were highest in July and August for both stations and lowest in April and October in Jacksonville and April and November in Willard.

a

b

Figure 3.

Walter climate diagrams for the two weather stations nearest Shaken Creek Preserve. Data from the State Climate Office of North Carolina (2012; see http://www.nc-climate.ncsu.edu). Suppl. material 1

a: Walter climate diagram for the weather station in Jacksonville, NC (Onslow Co.).  
b: Walter climate diagram for the weather station in Willard, NC (Pender Co.).  

The annual growing season, defined as the number of days in five years out of ten during which the daily minimum temperatures exceed 28 °F (-2.2 °C), is 235 days in Pender County and 210 days in Onslow County (Barnhill 1990, Barnhill 1992).

Elevation at SCP ranges from 4 m (13 ft) to 12.9 m (42 ft) above sea level (NC Department of Transportation, http://www.ncdot.gov/it/gis/default.html).

Twelve soil types representing five soil orders are mapped at SCP (Barnhill 1990, Barnhill 1992; Fig. 4). Ultisols are the most abundant in type, though Spodosols are the most abundant in area. Entisols comprise 21.4% of the total area and are the dominant soil order along Shaken Creek and Shelter Swamp Creek. While most areas mapped as Entisols support swamp communities, a few savannas do occur over Entisols, as along Alligator Lake Road and the eastern portion of Mule Pen Road. Histosols comprise 8.7% of the total area and, with one small exception, are restricted to the central western portion of the property, which is dominated by Pond Pine Woodland (Typic subtype) and High Pocosin (Typic subtype) communities (sensu Schafale 2012). No savanna or savanna-like community types are known to occur on Histosols at SCP. Inceptisols comprise 14.2% of the total area and are the dominant order in the central eastern portion of the property, an area that has not been managed with fire in many decades. Excepting one very small area on the west side of the north end of Alligator Lake Road, no savannas or savanna-like areas occur at SCP in areas mapped as Inceptisols. Spodosols comprise 36.6% of the total area and are the dominant soil order in the central, northwestern, and southestern portions of the property. Excellent examples of savannas and flatwoods occurring over Spodosols are apparent along Half Moon Road, Long Ridge Road, and the portion of Flo Road between the powerline right of way and Meadow Lake Road. Ultisols comprise 19.1% of the total area and are the dominant order in the northeastern and southeastern portions of the property. Many of the most species-rich savannas, most notably those along Flo Road east of its intersection with Fill Road, occur in areas mapped as Ultisols.

Figure 4.  

Soil mapping units at Shaken Creek Preserve. Coll. area = collection area; PL = powerline right-of-way; BaB = Baymeade fine sand; Ct = Croatan muck; Fo = Foreston loamy fine sand; LnA = Leon fine sand; Ma = Mandarin fine sand; Mk = Muckalee loam, frequently flooded; Mu = Murville muck; PaA = Pactolus fine sand; Pn = Pantego mucky fine sandy loam; St = Stallings loamy fine sand; To = Torhunta mucky fine sandy loam; Wo = Woodington fine sandy loam. Based on data from Barnhill (1990, 1992). Baseline imagery from Bing Maps Aerial, courtesy of Environmental Systems Research Institute (ESRI) (2011).

A brief synopsis of each of the twelve soil types, arranged by soil order, is provided below.

Entisols

Muckalee (Mk) loam, frequently flooded (Coarse-loamy, siliceous, superactive, non-acid, thermic Typic Fluvaquents)

Poorly-drained soils on floodplains. Slopes are 0–2%. Typical soil texture is loam in the upper 30 cm and sandy loam with thin strata of loamy sand or sand from 30 cm to 150 cm. These soils have a seasonal high water table between 15 cm and 46 cm below the soil surface and are frequently flooded for brief periods (Barnhill 1990). This is the primary mapping unit along Shaken Creek and Shelter Swamp Creek and is occupied predominantly by Blackwater Bottomland Hardwoods (High subtype) and other swamp communities.

Pactolus (PaA) fine sand (Thermic, coated Aquic Quartzipsamments)

Moderately well-drained or somewhat poorly-drained soils in slight depressions in uplands and on low ridges on terraces. Slopes are 0–2%. Typical soil texture is fine sand to 200 cm below the soil surface. These soils have a seasonal high water table between 46 cm and 76 cm below the soil surface and are not subject to flooding (Barnhill 1990). This mapping unit occurs primarily in narrow bands along the southern portion of the property. Three examples of the Very Wet Loamy Pine Savanna community occur on Pactolus soils.

Histosols

Croatan (Ct) muck (Loamy, siliceous, dysic, thermic Terric Haplosaprists)

Very poorly-drained soils on interstream divides. Slopes are 0–2%. Typical soil texture is muck in the upper 89 cm, fine sandy loam between 89 cm and 114 cm, sandy clay loam between 114 cm and 191 cm, and fine sandy loam between 191 cm and 200 cm. These soils have a seasonal high water table at or near the soil surface for about six months and are rarely flooded for brief periods (Barnhill 1990). This mapping unit is nearly restricted to the central-western portion of the property and supports Pond Pine Woodland (Typic subtype) and High Pocosin (Typic subtype) communities.

Inceptisols

Torhunta (To) mucky fine sandy loam (Coarse-loamy, siliceous, active, acid, thermic Typic Humaquepts)

Very poorly-drained soils on interstream areas and on stream terraces. Slopes are 0–2%. Typical soil texture is mucky fine sandy loam in the upper 8 cm, fine sandy loam between 8 cm and 152 cm, and sandy loam and sand to 200 cm. These soils have a seasonal high water table between 15 cm and 46 cm below the soil surface and are rarely flooded for brief periods (Barnhill 1990). This mapping unit occupies the central-eastern portion of the property, a fire-suppressed area that supports few or no savanna, flatwood, or sandhill communities.

Spodosols

Leon (LnA) fine sand (Sandy, siliceous, thermic Aeric Alaquods)

Poorly-drained soils on interstream areas. Slopes are 0–2%. Typical soil texture is fine sand to 200 cm below the soil surface. These soils have a seasonal high water table less than 30 cm below the soil surface and are not subject to flooding (Barnhill 1990). This is the primary mapping unit of the central portion of the property and is well-represented along Half Moon Road and the portion of Flo Road between the powerline cut and Meadow Lake Road. The best and most accessible examples of Wet Pine Flatwoods (Typic subtype), Sandy Pine Savanna (Typic subtype), and Sandy Pine Savanna (Rush featherling subtype) are found in areas mapped as Leon fine sand.

Mandarin (Ma) fine sand (Sandy, siliceous, thermic Oxyaquic Alorthods)

Somewhat poorly-drained soils on moderately elevated areas in interstream divides. Slopes are 0–2%. Typical soil texture is fine sand in the upper 101 cm and sand between 101 cm and 200 cm. These soils have a seasonal high water table between 46 cm and 107 cm below the soil surface and are not subject to flooding (Barnhill 1990). This mapping unit is restricted to narrow ridges in the central and western portions of the property. The largest example is in the northwest corner of the property south of Long Ridge Road, which supports extensive Wet Pine Flatwoods (Typic subtype) and Sandy Pine Savanna (Typic subtype) communities.

Murville (Mu) muck (Sandy, siliceous, thermic Umbric Endoaquods)

Very poorly-drained soils on interstream areas and in depressions. Slopes are 0–2%. Typical soil texture is muck in the upper 8 cm, mucky fine sand between 8 cm and 28 cm, fine sand between 28 cm and 124 cm, loamy fine sand between 124 cm and 140 cm, and fine sand between 140 cm and 200 cm. These soils have a seasonal high water table less than 30 cm below the soil surface and are not subject to flooding (Barnhill 1990). This mapping unit is the largest in area at SCP and dominates the west-central and western portions of the property. It is particularly abundant north of Mule Pen Road and along the portion of Indian Grave Road east of the powerline cut. Most areas mapped as Murville support Pond Pine Woodland (Typic subtype) communities.

Ultisols

Baymeade (BaB) fine sand (Loamy, siliceous, semiactive, thermic Arenic Hapludults)

Well-drained soils on low ridges and convex slopes in uplands. Slopes are 1–4%. Typical soil texture is fine sand in the upper 64 cm, fine sandy loam between 64 cm and 148 cm, and fine sand between 148 cm and 200 cm. These soils have a seasonal high water table between 122 cm and 152 cm below the soil surface and are not subject to flooding (Barnhill 1990). The smallest mapping unit on site, Baymeade fine sand is restricted to one area north of Mule Pen Road, approximately 1 km west of the intersection of Mule Pen Road and Williams Road. This small area is among the driest and “hilliest” at SCP and supports a Pine/Scrub Oak Sandhill (Mesic Transition subtype) community.

Foreston (Fo) loamy fine sand (Coarse-loamy, siliceous, semiactive, thermic Aquic Paleudults)

Moderately well-drained soils on slightly convex interstream divides near shallow drainageways. Slopes are 0–2%. Typical soil texture is loamy fine sand in the upper 33 cm, fine sandy loam between 33 cm and 102 cm, fine sandy loam with pockets of loamy fine sand between 102 cm and 140 cm, fine sandy loam with strata of loamy sand between 140 cm and 168 cm, and sandy clay loam with strata of sand and sandy loam between 168 cm and 200 cm. These soils have a seasonal high water table between 76 cm and 107 cm below the soil surface and are not subject to flooding (Barnhill 1990). Scattered throughout the property, this mapping unit is perhaps best represented along Flo Road near its intersection with Fill Road, an area that supports high-quality Wet Loamy Pine Savanna communities and, in depressional areas, Very Wet Loamy Pine Savanna communities.

Pantego (Pn) mucky fine sandy loam (Fine-loamy, siliceous, semiactive, thermic Umbric Paleaquults)

Very poorly-drained soils on interstream areas. Slopes are 0–2%. Typical soil texture is mucky fine sandy loam in the upper 25 cm, fine sandy loam between 25 cm and 61 cm, sandy clay loam between 61 cm and 150 cm, clay loam with strata of sandy clay loam between 150 cm and 183 cm, and sandy clay loam with thin strata of loamy sand between 183 cm and 200 cm. These soils have a seasonal high water table within 46 cm of the soil surface and are rarely flooded for brief periods (Barnhill 1990). This mapping unit is restricted to a small area in the extreme east-central portion of the property. No savannas, flatwoods, or sandhills are known from this area.

Stallings (St) loamy fine sand (Coarse-loamy, siliceous, semiactive, thermic Aeric Paleaquults)

Somewhat poorly-drained soils on interstream areas and in shallow depressions on convex divides. Slopes are 0–2%. Typical soil texture is loamy fine sand in the upper 30 cm, fine sandy loam between 30 cm and 114 cm, fine sandy loam with pockets of sandy clay loam between 114 cm and 168 cm, and sandy clay loam with thin layers of fine sandy loam between 168 cm and 200 cm. These soils have a seasonal high water table between 46 cm and 76 cm below the soil surface and are not subject to flooding (Barnhill 1992). As with the preceding map unit, Stallings loamy fine sand is restricted to a small area in the extreme east-central portion of the property. No savannas, flatwoods, or sandhills are known from this area.

Woodington (Wo) fine sandy loam (Coarse-loamy, siliceous, semiactive, thermic Typic Paleaquults)

Poorly-drained soils on interstream areas and in depressions near drainageways. Slopes are 0–2%. Typical soil texture is fine sandy loam in the upper 43 cm and fine sandy loam with pockets or strata of loamy fine sand between 43 cm and 200 cm. These soils have a seasonal high water table between 15 cm and 30 cm below the soil surface and are not generally subject to flooding, though low areas may be subject to ponding for brief periods (Barnhill 1990). This mapping unit occurs commonly in the northeastern and southeastern portions of the property, particularly along Bug Ridge Road, at the graded end of Half Moon Road, and along the far eastern portion of Flo Road. Scattered and usually small examples of savannas, flatwoods, and sandhills occur in areas mapped as Woodington fine sandy loam.

Seven savanna, flatwoods, or sandhill plant community types were distinguished at SCP following Schafale (2012) (Table 1). Among these community types, three are globally critically imperiled (G1); the remainder are globally imperiled or vulnerable (G2G3). In general, the drier savanna or savanna-like community types (i.e., Pine/Scrub Oak Sandhill (Mesic Transition subtype) and Mesic Pine Savanna (Coastal Plain subtype)) are restricted to slightly-elevated ridges that occur mostly in the central and western portions of the property; other areas on site are typically dominated by wetter community types (i.e., Wet Pine Flatwoods (Typic subtype) or one of the four Wet Pine Savanna community types; Fig. 5).

Figure 5.  

Approximate locations within Shaken Creek Preserve of the community types treated in this work. All known examples of the four Wet Pine savanna communities on site are mapped. The highest-quality examples of the other communities on site are also shown; however, fire-suppressed examples of some of these community types occur throughout the property and are not mapped. In the legend community types (sensu Schafale 2012) are arranged from driest to wettest (i.e., in order of increasing soil moisture). Areas in which two community types intergrade or co-occur in a mosaic are indicated by including the abbreviations of both community types, separated by a forward slash (e.g., MPS-CP/WPF-T). PL = powerline right-of-way; PSOS-MT = Pine/Scrub Oak Sandhill (Mesic Transition subtype); MPS-CP = Mesic Pine Savanna (Coastal Plain subtype); WPF-T = Wet Pine Flatwoods (Typic subtype); SPS-T = Sandy Pine Savannas (Typic subtype); SPS-RF = Sandy Pine Savanna (Rush Featherling subtype); WLPS = Wet Loamy Pine Savanna; VWLPS = Very Wet Loamy Pine Savanna. Baseline imagery from Bing Maps Aerial, courtesy of Environmental Systems Research Institute (ESRI) (2011).

As is true of most longleaf pine-dominated communities, all the community types treated herein are dependent on frequent, low-intensity fires to maintain their integrity (Figs 6, 7).

a

b

Figure 6.

Variations in fire intensity based on vegetation type.

a: In savannas that are frequently burned and lack significant woody vegetation, fires are small enough to be stepped over harmlessly (photo by R. Thornhill).  
b: Fire intensity increases along the woody margins of savannas and flatwoods (photo by R. Thornhill).  

a

b

Figure 7.

Fire time-series in a Wet Loamy Pine Savanna community type. Many savanna species, particularly bunchgrasses, flower only following growing-season fires. This sequence of photos shows the effects of fire on the flowering of Ctenium aromaticum (toothache grass).

a: April 30, two days after a burn (photo by R. Thornhill).  
b: June 27, just less than two months after a burn. Notice the profusion of flowering stalks of Ctenium aromaticum in the burned area (left) versus their near-absence in the unburned (right) area (photo by R. Thornhill).  

Though this work examines only savanna or savanna-like community types, it is worth noting that numerous other plant community types are present at SCP. Examples include Blackwater Bottomland Hardwoods (High subtype) along Shaken Creek and Shelter Swamp Creek, High Pocosin (Typic subtype) along the domed west-central portion of the property, and Pond Pine Woodland (Typic subtype and Canebrake subtype) along portions of Williams Road and Half Moon Road (Fig. 8).

a

b

Figure 8.

Two community types not formally treated in this thesis: Pocosin and Pond Pine Woodland. The overall species composition of these community types is very similar to (albeit less rich) than the flatwoods and savanna community types formally treated in this work. Indeed, virtually all species in pocosins and pond pine woodlands are also found in flatwoods and/or savannas; consequently, this guide will facilitate the identification of species in pocosins and pond pine woodlands as well as in flatwoods and savannas.

a: Pocosin: note the dense growth of low (mostly evergreen) shrubs and the absence of tall trees (photo by R. Thornhill).  
b: Pone Pine Woodland: note the dense stand of Pinus serotina (Pond pine) that characterizes this community (photo by R. Thornhill).  

In the following discussion community types are presented in order from driest to wettest (i.e., according to increasing soil moisture). For each community type the most similar NatureServe association (see http://www.natureserve.org/explorer) is provided in brackets.

Pine/Scrub Oak Sandhill (Mesic Transition subtype; S2S3, G2G3) [Pinus palustris / Quercus incana / Aristida stricta - Sorghastrum nutans - Anthaenantia villosa Woodland (CEGL003578)]. This community type is somewhat common in the Sandhills and outer Coastal Plain of North Carolina but is rare at SCP. Areas of this community type in which collection efforts have been made comprise approximately 4 ha (10 ac), all in the western portion of the property, particularly along Mule Pen Road. Associated soil series are Baymeade (Arenic Hapludult), Foreston (Aquic Paleudult), and Pactolus (Aquic Quartzipsamment; Barnhill 1990).

The canopy is dominated by Pinus palustris and several oak species, including Quercus falcata Michx., Q. incana W. Bartram, Q. margarettae (Ashe) Small, and Q. marilandica Münchh. var. marilandica. Understory species include Diospyros virginiana L., Gaylussacia dumosa (Andrews) Torr. & A. Gray, G. frondosa (L.) Torr. & A. Gray ex Torr., Sassafras albidum J. Presl, and Vaccinium tenellum Aiton. Vines are not abundant, but Gelsemium sempervirens J. St.-Hil. and Smilax glauca Walter are occasionally present. In the herb layer, Aristida stricta Michx. is abundant, and several dry-mesic species that are not found in the other communities (except sometimes in Mesic Pine Savanna (Coastal Plain subtype)) occur, including Euphorbia ipecacuanhae L., Lespedeza hirta (L.) Hornem. var. curtissii (Clewell) Isely, and Tragia urens L.

This community type is similar to and grades into Mesic Pine Savanna (Coastal Plain Subtype), from which it is distinguished by a substantial component of scrub oaks and by a less diverse herbaceous layer that generally contains fewer legume species. Most examples on site are fire-suppressed; in some cases, fire has not occurred in at least twenty years. To what extent the abundance of oaks in these cases is due simply to fire suppression rather than other environmental factors is unclear. Overall, this community type is not degraded as quickly in the absence of fire as other, wetter community types, which are subject to more rapid shrub invasion.

Mesic Pine Savanna (Coastal Plain subtype; S2, G2G3) [Pinus palustris / Amorpha herbacea var. herbacea / Aristida stricta - Sorghastrum nutans Woodland (CEGL003569)]. This community type is uncommon in North Carolina and rare at SCP. Areas of this community type in which collection efforts have been made comprise approximately 3.6 ha (9 ac), with the largest tract along Indian Grave Road and smaller tracts north of Alligator Lake Road. Sporadic examples of this community type occur in slightly elevated areas within Wet Loamy Pine Savannas and Very Wet Loamy Pine Savannas; however, due to their small size, such examples are not mapped. The soil series most commonly associated with this community type is Pactolus (Aquic Quartzipsamment), though small areas of this commuity type are mapped as Woodington (Typic Paleaquult; Barnhill 1990).

The canopy is dominated by Pinus palustris; oak species are generally absent or sparse. Understory species include Gaylussacia dumosa, G. frondosa, and Vaccinium tenellum. Amorpha georgiana Wilbur and A. herbacea Walter var. herbacea are excellent indicators when present, though these are not usually abundant. Vine species include Apios americana Medik. and Centrosema virginianum (L.) Benth., which are generally absent in other communities. The diverse ground layer includes several species not known from other community types, including Danthonia sericea Nutt., Lechea minor L., Lespedeza angustifolia (Pursh) Elliott, and Stylosanthes biflora (L.) Britton, Sterns & Poggenb.

This community type is similar to Pine/Scrub Oak Sandhill (Mesic Transition subtype), from which it is best distinguished by the absence of scrub oaks or their presence combined with wetland species, and a more diverse herbaceous layer that contains a relatively abundant and diverse component of legume species. It is distinguished from the Wet Pine Savanna community types by the lack of carnivorous plants species, the relative abundance and diversity of legume species, and the dominance of only one bunchgrass species, Aristida stricta, with little or no Sporobolus pinetorum Weakley & P.M. Peterson, no Ctenium aromaticum, and no Muhlenbergia expansa (Poir.) Trin.

Wet Pine Flatwoods (Typic subtype; S3, G3) [Pinus palustris / Ilex glabra / Aristida stricta Woodland (CEGL003648)] (Fig. 9)

a

b

Figure 9.

Wet Pine Flatwoods (Typic subtype)

a: A typical wet pine flatwoods (photo by R. Thornhill).  
b: When frequently burned, the physiognomy of wet pine flatwoods resembles that of Pine Savannas; however, species diversity and overall richness, especially at a small scale, is lower in in this community type than in true savannas (photo by R. Thornhill).  

The canopy consists of Pinus palustris and Pinus serotina Michx., with occasional Pinus taeda L. In addition to those species listed for the preceding community types, the sometimes-dense shrub layer also contains species characteristic of wetter soils, such as Ilex glabra (L.) A. Gray, Kalmia carolina Small, Lyonia mariana (L.) D. Don, Morella pumila (Michx.) Small, Rhododendron atlanticum (Ashe) Rehder, and R. viscosum (L.) Torr. Few vine taxa are present, though Smilax laurifolia L. is sometimes abundant. The dense herbaceous layer is dominated by Aristida stricta, usually with Vaccinium crassifolium Andrews codominant. Pyxidanthera barbulata Michx. and Pteridium aquilinum (L.) Kuhn var. pseudocaudatum (Clute) A. Heller are often subdominant and, when abundant, are good indicators of this community type.

The use of the terms “flatwoods” and “savannas” is notoriously variable, and sometimes contradictory, from person to person. In general “flatwoods” has been used to designate savanna-like areas that are shrubbier and/or less floristically diverse than true savannas. This work follows Schafale (2012) in distinguishing flatwoods by their floristic composition and lower small-scale species richness. While Wet Pine Flatwoods (Typic subtype) may have a naturally denser shrub layer than savannas, essentially all the community types treated in this work become shrubby in the absence of fire; relative shrub dominance is, therefore, a poor indicator of community type. Wet Pine Flatwoods (Typic subtype) often grades into Sandy Pine Savanna (Typic subtype), particularly on Spodosol soils. In these cases Wet Pine Flatwoods (Typic subtype) can be distinguished by the abundance of Pyxidanthera barbulata, Pteridium aquilinum var. pseudocaudatum, and Vaccinium crassifolium; the absence or near-absence of bunchgrass species characteristic of wetter sites, particularly Ctenium aromaticum and Muhlenbergia expansa; the absence of carnivorous species (with the exception of species of Drosera L.); and an overall lower small-scale species richness. In fire-suppressed areas, it is often difficult to determine whether the natural community type is Wet Pine Flatwoods (Typic subtype) or one of the Wet Pine Savannas, though some insight can be obtained by searching for remnant bunchgrasses and carnivorous plants, particularly species of Sarracenia L.

Sandy Pine Savanna (Typic subtype; S3, G3) [Pinus palustris - Pinus serotina / Ctenium aromaticum - Muhlenbergia expansa - Carphephorus odoratissimus Woodland (CEGL003658)]. Relatively common in North Carolina, this community type is the most common Wet Pine Savanna community at SCP. It often occurs in a mosaic with the closely related Wet Pine Flatwoods (Typic subtype). In areas where these two community types co-occur, Wet Pine Flatwoods (Typic subtype) generally occurs on slightly-elevated, drier sites and Sandy Pine Savanna (Typic subtype) on sites that are somewhat lower and wetter. The total area occupied by this community type at SCP is estimated at 13 ha (33 ac), with another 24 ha (60 ac) existing in a mosaic with Wet Pine Flatwoods (Typic subtype). Associated soil series are Leon (Aeric haplaquod) and Mandarin (Typic haplohumod; Barnhill 1990).

Canopy species are Pinus palustris and P. serotina. The composition of the shrub layer is geneally the same as Wet Pine Flatwoods (Typic subtype), though shrub density is often somewhat lower. As above, vines are sparse, but Smilax laurifolia is sometimes abundant, particularly in unburned areas. The species-rich herbaceous layer usually contains all the species present in Wet Pine Flatwoods (Typic subtype) plus many more, including several grasses (Andropogon glaucopsis Steud., A. glomeratus (Walter) Britton, Sterns, & Poggenb., Sporobolus pinetorum, and, less commonly, Ctenium aromaticum), carnivorous plants (Dionaea muscipula J. Ellis and Sarracenia flava L.), and other herbs (Osmundastrum cinnamomeum (L.) C. Presl and Polygala lutea L.).

While Pleea tenuifolia Michx. is often found in Sandy Pine Savanna (Typic subtype), occurrences are scattered, and the species as a whole comprises only a minor component of the flora. In the closely-related Sandy Pine Savanna (Rush Featherling subtype), Pleea tenuifolia is a dominant species, generally as or more abundant than any single bunchgrass species. Sandy Pine Savanna (Typic subtype) can be distinguished from Wet Loamy Pine Savanna and Very Wet Loamy Pine Savanna by its coarser-textured soils and by the absence of a suite of species characteristic of wetter, richer sites, including Chaptalia tomentosa Vent., Cirsium virginianum (L.) Michx., Eryngium spp., Lysimachia loomisii Torr., Polygala hookeri Torr. & A. Gray, P. ramosa Elliott, and many species of Rhynchospora Vahl.

Sandy Pine Savanna (Rush Featherling subtype; S1, G1) [Pinus palustris - Pinus serotina / Pleea tenuifolia - Aristida stricta Woodland (CEGL003661)] (Fig. 10)

a

b

Figure 10.

Sandy Pine Savanna (Rush Featherling subtype)

a: A super-abundance of the white-flowered Pleea tenuifolia (Rush featherling) characterizes this community type (photos by R. Thornhill).  

This community type is very similar to Sandy Pine Savanna (Typic subtype); both share the same canopy and vine species and most of the same herb species. However, the Rush Featherling subtype is distinguished by the dominance of Pleea tenuifolia, whose abundant white flowers in early autumn give rise to the colloquial community name “Snow in September.” The thick rhizomes of Pleea tenuifolia produce dense, broad clumps that create a somewhat hummocky topography. Species richness and diversity are sometimes lower in the Rush Featherling subtype than in the Typic subtype due to the sheer dominance of Pleea tenuifolia. The environmental factors responsible for this community type are unclear. At SCP both the Rush Featherling and Typic subtypes occur on Leon soils and in close proximity to one another. However, the author has noticed that Pleea tenuifolia is sometimes abundant in local depressions within the Typic subtype, an observation that suggests that P. tenuifolia possibly favors wetter soils. Perhaps, then, the Rush featherling subtype has a somewhat higher water table than the Typic subtype, though this hypothesis has not been tested.

Wet Loamy Pine Savanna (S1, G1) [Pinus palustris - Pinus serotina / Ctenium aromaticum - Muhlenbergia expansa - Rhynchospora latifolia Woodland (CEGL003660)] (Fig. 11a)

a

b

Figure 11.

Two Loamy Pine Savanna community types

a: This Wet Loamy Pine Savanna, treeless and dominated by the charismatic Sarracenia flava (yellow pitcher plant), is one of the most stunning vistas in Shaken Creek Preserve – or perhaps anywhere (photo by R. Thornhill)!  
b: Very Wet Loamy Pine Savannas harbor a suite of exceptionally rare species, often found in slight depressions, like the narrow one running from left to right in this photograph (photo by R. Thornhill).  

a

b

c

d

Figure 12.

Distribution of taxa by habit and community type in the savannas and flatwoods in Shaken Creek Preserve ("SCP") and vicinity (i.e., within two mile of Shaken Creek Preserve, including Sandy Run Savannas State Natural Area; “SR+V”). “Taxa” includes species, subspecies, and varieties. Values include taxa vouchered or known only from reports. Suppl. material 5

a: Taxonomic distribution of herbaceous taxa. Families represented by ≥ 8 herbaceous taxa in either Shaken Creek Preserve or in the vicinity are represented individually; families represented by < 8 herbaceous taxa in both Shaken Creek Preserve and in the vicinity are subsumed in the “Other families” category.  
b: Taxonomic distribution of tree and shrub taxa. Families represented by ≥ 2 tree or shrub taxa in either Shaken Creek Preserve or in the vicinity are represented individually; families represented by only 1 tree or shrub taxon in both Shaken Creek Preserve and in the vicinity comprise the “Other families” category.  
c: Taxonomic distribution of vines (herbaceous or woody plants that climb by means of holdfasts or by twining). All families containing vine taxa are included.  
d: Distribution by community type of taxa collected or reported from Shaken Creek Preserve. Values above columns indicate the total number of taxa (i.e., rare and non-rare) collected or reported from each community type. "Rare taxa” are those taxa listed by the NC Natural Heritage Program as Significantly Rare or Watch List (Gadd and Finnegan 2012). Community types follow Schafale (2012) and are arranged according to increasing soil moisture (i.e., from the driest to wettest community type). Abbreviations are as follows: PSOS-MT = Pine/Scrub Oak Sandhill (Mesic Transition subtype); MPS-CP = Mesic Pine Savanna (Coastal Plain subtype); WPF-T = Wet Pine Flatwoods (Typic subtype); SPS-T = Sandy Pine Savanna (Typic subtype); SPS-RF = Sandy Pine Savanna (Rush Featherling subtype); WLPS = Wet Loamy Pine Savanna; VWLPS = Very Wet Loamy Pine Savanna.  

The canopy is dominated by Pinus palustris and P. serotina, with occasional P. taeda. The sparse to nearly absent understory consists of species similar to other Wet Pine Savanna community types. Vines are scarce, though several Smilax species treated in this work have been collected in thickets along the roadside edge of Wet Loamy Pine Savannas. The herbaceous layer is very diverse and generally includes all taxa present in the Sandy Pine Savanna communities plus many other taxa. Among bunchgrasses, Ctenium aromaticum, Muhlenbergia expansa, and Sporobolus pinetorum dominate or co-dominate with Aristida stricta. Herbs that are often present in Wet Loamy Pine Savannas but not in Sandy Pine Savannas include Chaptalia tomentosa, Cirsium virginianum, Eryngium L. spp., Lysimachia loomisii, Polygala hookeri, P. ramosa, and many Rhynchospora spp.

As their names imply, both Loamy Pine Savanna community types are distinguished from Sandy Pine Savanna community types by somewhat finer-textured soils. In general, finer-textured soils are more fertile than and have a higher water-holding capacity than coarser-textured soils—conditions that would seem to be favorable to the growth of most plant species. These environmental factors may explain, at least partially, the exceptionally high species richness of the Loamy Pine Savanna communities (Schafale 2012). Wet Loamy Pine Savannas are distinguished from Mesic Pine Savannas (Coastal Plain subtype) by the abundance of wetland plants and the near absence of legumes. Wet Loamy Pine Savannas are distinguished from Very Wet Loamy Pine Savannas by a lower abundance of boggy species (e.g., Eriocaulon decangulare L. var. decangulare, Lachnocaulon anceps (Walter) Morong, and Taxodium ascendens Brongn.) and by the absence of a suite of rare species (Allium species 1, Carex lutea LeBlond, and Thalictrum cooleyi H.E. Ahles).

Very Wet Loamy Pine Savanna (S1, G1) [Pinus palustris - Pinus serotina / Magnolia virginiana / Sporobolus teretifolius - Carex striata Woodland (CEGL004500)] (Fig. 11b)

Canopy species include those of other Wet Pine Savannas, though Pinus palustris is often less abundant. Taxodium ascendens, not usually found in the other communities, also frequently occurs. Shrub species that are more common in this community type than in others include Morella cerifera (L.) Small and Ilex myrtifolia Walter. Vines are generally uncommon, though Mikania scandens (L.) Willd. and Toxicodendron radicans (L.) Kuntze var. radicans are more likely to be found in this community type, particularly along swampy margins or in unburned sites, than in other community types. The herbaceous layer may include all taxa present in other Wet Pine Savannas plus an additional suite of rare species: Allium species 1, Carex lutea, and Thalictrum cooleyi, all of which are strong indicators for this community type. Aristida stricta is often scarce or even entirely absent, replaced by other bunchgrass species, particularly Muhlenbergia expansa. Many wetland herbs that are sometimes found in Wet Loamy Pine Savannas are often much more abundant in Very Wet Loamy Pine Savannas. Examples inlcude Carex striata Michx., Chaptalia tomentosa, and Eryngium spp. Boggy species, like Eriocaulon decangulare var. decangulare and Lachnocaulon anceps, which are restricted to borrow pits and depressions in other community types, are also more likely to occur in the savannas proper of this community type.

Globally, Very Wet Loamy Pine Savannas have a small, patchy distribution, and the environmental factors responsible for their occurrence are unclear. As noted by Schafale (2012), the abundance of wetland species would seem to indicate a wetter soil than that of Wet Loamy Pine Savannas. In most cases, however, Wet Loamy Pine Savannas grade directly into swamps or pocosins on their wet edges; why in rare cases Very Wet Loamy Pine Savannas form in these ecotonal positions is uncertain. The natural fire frequency of Very Wet Loamy Pine Savannas is also unclear but may be somewhat lower than that of the other savanna communities due to a higher water table and a suspected slightly higher natural shrub density. Some Very Wet Loamy Pine Savannas exhibit localized inclusions of calcium (in the form of marl) that increase soil pH in small areas (Schafale 2012). Rare in the Coastal Plain of NC, these inclusions were once thought to explain the curious distribution of this community type; however, many calcium deposits underlying Very Wet Loamy Pine Savannas appear to be several feet below the soil surface, where they would presumably exert little impact on the pH of the upper portion of the soil in which most plants root. Moreover, one study (Taggart 2012) suggested that even in Very Wet Loamy Pine Savannas in which inclusions of high pH have been reported, most of the soil throughout the savanna is still strongly acidic. Further research into the environmental factors associated with this community type is certainly warranted.

A preliminary list of plant taxa reported from SCP by LeBlond (2000) and by the Carolina Vegetation Survey (Peet et al. 2004) was compiled. Taxa collected or reported from various tracts comprising Sandy Run Savannas State Natural Area were also included; for these taxa, the following sources were referenced: LeBlond and Weakley (1991), LeBlond (1999), LeBlond (2000), Taggart (2010). Finally, taxon reports for Pender and Onslow Counties were obtained from the US Southeastern Flora Atlas (http://www.herbarium.unc.edu/seflora/firstviewer.htm), a resource that incorporates pertinent records from the USDA PLANTS Database (United States Department of Agriculture, Natural Resources Conservation Service 2012), Radford et al. (1968), and any specimens databased to-date by several herbaria, including those of North Carolina State University (NCSC) and the University of North Carolina at Chapel Hill (NCU). Culled from this initial checklist were taxa either reported by the various sources in habitats other than those studied in the present thesis or, in the case of the county records obtained through the Southeastern Flora Atlas, taxa whose habitat description in Weakley (2010) did not include savannas, flatwoods, or similar habitats. The resulting condensed list was subsequently used to search the herbarium collections of Duke University (DUKE), NCSC, NCU, and the University of North Carolina Wilmington (WNC) for any historic collections made from pertinent habitats in SCP, in tracts now comprising Sandy Run Savannas State Natural Area, or in other areas within two miles of SCP (Fig. 1).

Field work began in August 2010 and continued through October 2012. In order to capture the floristic diversity of SCP throughout the growing season, collecting trips (N=81) were made approximately weekly from mid-March 2011 through November 2011, biweekly from December 2011 to February 2012, weekly from early March 2012 through early September 2012, and biweekly from early September 2012 through mid-October 2012. Collecting efforts in 2011 centered on the extensive Wet Pine Savanna and Wet Pine Flatwoods community types along Flo Road and Half Moon Road (Fig. 2). In 2012 collection efforts extended to include all Wet Pine Savanna and Wet Pine Flatwoods community types throughout the property and the relatively few examples of Mesic Pine Savanna and Pine/Scrub Oak Sandhill community types on site (Fig. 5). Voucher specimens were collected in duplicate (or more) and deposited at NCSC. In addition, leaf samples were taken from most vouchers, desiccated in silica gel, and deposited in the NCSC DNA bank (see herbarium.ncsu.edu), where available for use by the scientific community. Specimen determinations were made by Robert Thornhill and were verified by the following: Richard LeBlond (Dichanthelium), Dr. Jon Stucky (Cyperaceae, Juncaceae, and Poaceae excluding Dichanthelium), and Dr. Alexander Krings (all other taxa). A list of all voucher specimens and associated data (except location data for rare or over-collected taxa) can be found in Suppl. material 6.

Following the completion of field work, herbarium research, and a digital querying of rare taxa reports within 2 miles of SCP (using the North Carolina Natural Heritage Program's MapViewer application http://www.ncnhp.org), a data-rich checklist of all the vascular flora collected or reported from savannas, flatwoods, or sandhill community types in SCP or the vicinity was prepared. (The checklist is available in spreadsheet format in Suppl. material 7.) Within the checklist, taxa are organized by major plant groups (i.e., Pteridophytes; Gymnosperms; Monocotyledons; Basal Angiosperms, Magnoliids, and Eudicotyledons), then alphabetically by family, genus, and species. Each taxon is accompanied by a brief entry that contains the following three sections:

• Conservation Status: For rare taxa (i.e., those listed by Gadd and Finnegan 2012), status and rank designations are provided in the following order: states status, federal status; state rank, global rank. The following abbreviations are used: STATE STATUS: E = Endangered; T = Threatened; SC = Special Concern: -V = Vulnerable, -H = Historical; SR = Significantly Rare: -L = Limited to North Carolina and adjacent states (endemic/near endemic), -T = Throughout, -P = Periphery of Range, -O = Other; W = Watch List: W1 = rare but relatively secure, W2 = rare but taxonomically questionable, W5B = exploited plants, W7 = rare and poorly known. FEDERAL STATUS: E = Endangered; FSC = Federal Species of Concern. STATE RANK: SH = historical (known only from historical populations); S1 = Critically imperiled, 1–5 populations in state; S2 = Imperiled, 6–20 populations in state; S3 = Vulnerable, 21–100 populations in state; S4 = Apparently secure, 101–1000 populations in state; S5 = Secure, 1001⁺ populations in state. GLOBAL RANK: G1 = Critically imperiled, 1–5 populations in world; G2 = Imperiled, 6–20 populations in world; G3 = Vulnerable, 21–100 populations in world; G4 = Apparently secure, 101–1000 populations in world; G5 = Secure, 1001⁺ populations in world; T# = Global rank of a subspecies or variety; Q = Questionable taxonomy; ? = Uncertain. (For a synopsis of all taxa of conservation concern treated in this work, see Tables 2, 3.)
• Distribution: The distribution of taxa is provided by listing the community types in which the taxa have been collected or reported within the study area. For taxa collected or reported from SCP, the community types (sensu Schafale 2012) in which the taxa occur on site are listed from driest to wettest (i.e., in order of increasing soil moisture) and are abbreviated as follows (see Table 1): PSOS-MT = Pine/Scrub Oak Sandhill (Mesic Transition subtype); MPS-CP = Mesic Pine Savanna (Coastal Plain subtype); WPF-T = Wet Pine Flatwoods (Typic subtype); SPS-T = Sandy Pine Savanna (Typic subtype); SPS-RF = Sandy Pine Savanna (Rush Featherling subtype); WLPS = Wet Loamy Pine Savanna; VWLPS = Very Wet Loamy Pine Savanna. For taxa not collected or reported from SCP but collected in the vicinity by Taggart (2010) or reported from the vicinity by LeBlond (1999) or LeBlond (2000), community types as provided by those authors are given. For all other taxa (i.e., those taxa collected or reported from the vicinity by sources other than the afoermentioned), habitat according to Weakley (2012) is provided in lieu of community types.
• Notes: Within each "notes" section, several bits of information are provided in the following order: 1) an estimate of abundance adadpted from Palmer et al. (1995) (see Table 4) for taxa collected by the senior author in SCP; 2) flowering and fruiting phenology from Weakley (2012) and supplemented, in some cases, with personal observation; 3) voucher information from specimens deposited in the following herbaria: DUKE, NCSC, NCU, and WNC. Within a list of vouchers, specimens collected in SCP are listed first, followed by specimens collected from the vicinity, which are arranged alphabetically by site name, then by tract name (if within Sandy Run), and finally by collector last name. For taxa of conservation concern that were collected in Sandy Run, the name of the tract in which the voucher was collected is purposefully omitted; and 4) in brackets, synonymy with Radford et al. (1968), the Flora of North America Project, and Weakley (2012).

Six taxa included in this guide bear numeric "placeholder" epithets, as currently listed in Weakley (2012). Of these six taxa, the following four are presumed to be new to science: Allium species 1, Coreopsis species 1, Scleria species 1, and Xyris species 1. The remaining two taxa–Dichanthelium species 3 and D. species 12–were recognized by previous authors (see synonymy for those taxa in the checklist); however, the appropriate combination has yet to be made within Dichanthelium.Based on field observations by the senior author, instances of known hybridization appear to be rare in the flora. (Actual hybridization events may be more common but are beyond the scope of this research.) One notable exception, however, is Sarracenia × catesabaei Elliott (= S. flava L. × S. purpurea L.). (See the key to Sarracenia for a discussion of hybridization within that genus.) Hybrids are nottreated as separate taxa in this guide.

Dichotomous keys were created to all taxa collected or reported from savannas, flatwoods, or sandhill community types in SCP and the vicinity (i.e., in areas within two miles of SCP, including all tracts within Sandy Run Savannas State Natural Area). The order of the keys follows that of the checklist (i.e., a key is first provided to four main vascular plant groups, then within each of these groups, keys proceed alphabetically by family and then genus). In addition, three “auxiliary keys” are provided: a vegetative key to common savanna bunchgrasses (following the key to genera of Poaceae); a key to herbaceous eudicotyledonous taxa with simple, opposite, more-or-less ovate leaves (following the key to families of basal angiosperms, magnoliids, and eudicotyledons); and a vegetative key to frequently confused ericaceous subshrubs (following the key to genera of Ericaceae). Keys were adapted from Radford et al. (1968), the cited Flora of North America treatments, Weakley (2012), and personal notes. In the keys exceptional values for numeric character ranges are indicated in parentheses (e.g., leaf blade 1–2(–4) cm wide). Definitions, explanatory notes, and exceptional non-numeric character states are also placed in parentheses (e.g., corolla pink (rarely white)).

During herbarium searches, vouchers of taxa collected by others in SCP or in the vicinity but not collected by the senior author in SCP were carefully examined. In five cases the senior author disagreed with the determinations of such vouchers. Nevertheless, since the original determinations were always of taxa whose habitat and distribution make them plausible components of the flora, these taxa were included in the keys, where indicated by a plus (+) symbol. These taxa are not, however, formally treated in this work (i.e., they do not appear in the checklist) and are not included in summary statistics. Additionally, forty-four taxa that are not known from the habitats treated in this work but that often occur in roadsides or other disturbed areas immediately adjacent to such habitats, are also included in the keys, where indicated by a double-dagger (‡) symbol. These taxa, too, are neither formally treated in this work nor included in the summary statistics. Finally, though only one exotic taxon is reported in this work, several of the forty-four aforementioned taxa (those strictly of roadsides or disturbed areas) are exotic (i.e., not native to the Coastal Plain of North Carolina, sensu Weakley 2012). Exotic taxa are indicated in the keys with an asterisk (*).