Wade A. Wall

Recent vicariance and the origin of the rare, edaphically specialized Sandhills lily, Lilium pyrophilum (Liliaceae): evidence from phylogenetic and coalescent analyses

Establishing the phylogenetic and demographic history of rare plants improves our understanding of mechanisms that have led to their origin and can lead to valuable insights that inform conservation decisions. The Atlantic coastal plain of eastern North America harbours many rare and endemic species, yet their evolution is poorly understood. We investigate the rare Sandhills lily (Lilium pyrophilum), which is endemic to seepage slopes in a restricted area of the Atlantic coastal plain of eastern North America. Using phylogenetic evidence from chloroplast, nuclear internal transcribed spacer and two low‐copy nuclear genes, we establish a close relationship between L. pyrophilum and the widespread Turk’s cap lily, L. superbum. Isolation‐with‐migration and coalescent simulation analyses suggest that (i) the divergence between these two species falls in the late Pleistocene or Holocene and almost certainly post‐dates the establishment of the edaphic conditions to which L. pyrophilum is presently restricted, (ii) vicariance is responsible for the present range disjunction between the two species, and that subsequent gene flow has been asymmetrical and (iii) L. pyrophilum harbours substantial genetic diversity in spite of its present rarity. This system provides an example of the role of edaphic specialization and climate change in promoting diversification in the Atlantic coastal plain.

Evidence for range stasis during the latter Pleistocene for the Atlantic Coastal Plain endemic genus, Pyxidanthera Michaux

The general phylogeographical paradigm for eastern North America (ENA) is that many plant and animal species retreated into southern refugia during the last glacial period, then expanded northward after the last glacial maximum (LGM). However, some taxa of the Gulf and Atlantic Coastal Plain (GACP) demonstrate complex yet recurrent distributional patterns that cannot be explained by this model. For example, eight co‐occurring endemic plant taxa with ranges from New York to South Carolina exhibit a large disjunction separating northern and southern populations by >300 km. Pyxidanthera (Diapensiaceae), a plant genus that exhibits this pattern, consists of two taxa recognized as either species or varieties. We investigated the taxonomy and phylogeography of Pyxidanthera using morphological data, cpDNA sequences, and amplified fragment length polymorphism markers. Morphological characters thought to be important in distinguishing Pyxidanthera barbulata and P. brevifolia demonstrate substantial overlap with no clear discontinuities. Genetic differentiation is minimal and diversity estimates for northern and southern populations of Pxyidanthera are similar, with no decrease in rare alleles in northern populations. In addition, the northern populations harbour several unique cpDNA haplotypes. Pyxidanthera appears to consist of one morphologically variable species that persisted in or near its present range at least through the latter Pleistocene, while the vicariance of the northern and southern populations may be comparatively recent. This work demonstrates that the refugial paradigm is not always appropriate and GACP endemic plants, in particular, may exhibit phylogeographical patterns qualitatively different from those of other ENA plant species.

Demographic effects of fire on two endemic plant species in the longleaf pine-wiregrass ecosystem

Fire can have dramatic effects on the vital rates of plant species and has been used successfully for management in a number of ecosystems. However, the demographic response of species to fire in fire-dependent ecosystems is variable, making it important to study the effects of fire on rare and threatened species. We quantified the effects of fire on Astragalus michauxii and Pyxidanthera brevifolia, two rare endemics of the longleaf pine-wiregrass ecosystem of the southeastern USA, by means of periodic matrix models to project the effect of fire frequency on population growth. In contrast to many species in the longleaf pine-wiregrass ecosystem, fire had short-term negative effects on both species, causing reductions in survival, size, flowering, and fruit production. Relative to the three-year fire intervals to which the study populations are currently exposed, more frequent burning is projected to cause population decline, with the most dramatic effects under annual burning. Although the current longleaf pine-wiregrass ecosystem is fire dependent and has experienced frequent fire for at least several thousand years, we propose that the two endemic species may be remnants from a past vegetation assemblage that experienced less frequent fire and thus may be adapted to longer fire-return intervals compared to other species currently in the ecosystem. Despite the short-term negative effects of fire on the vital rates of these species, longer-term benefits such as reduction of woody encroachment and litter removal may be important for the ultimate success of the species.

Plant-Soil-Hydrology Relationships in Three Carolina Bays in Bladen County, North Carolina

Abstract This study provides quantitative ecological targets for restoring degraded peat-based Carolina Bays in the Carolina Flatwoods Ecoregion. Cluster analysis of vegetation data from three Carolina Bay reference sites in Bladen County, North Carolina, indicated four plant communities present: pond pine (Pinus serotina) woodland, non-riverine swamp forest dominated by swamp gum (Nyssa biflora), high pocosin dominated by evergreen shrubs with scattered pond pine, and bay forest dominated by loblolly bay (Gordonia lasianthus). We classified bay soils according to surface organic layer thickness (OLT) into mineral, histic, shallow organic, and deep organic types. We monitored the water table of each soil type in one bay throughout one growing season. The soil types with corresponding water table regimes were: mineral (9.4 cm mean OLT with a rooting zone water table [RZWT] 39% of the monitoring period), histic (27.5 cm OLT and 76% RZWT), shallow organic (63.9 cm OLT and 84% RZWT), and deep organic (102.5 cm OLT and 57% RZWT). Pearson residual analysis and correspondence analysis revealed that pond pine woodland was positively associated with mineral and histic soils, non-riverine swamp forest with shallow organic soil, bay forest with deep organic soil, and high pocosin with deep organic soil. We concluded that peat-based Carolina Bay restoration in the Carolina Flatwoods Ecoregion should be gauged against reference data which suggests: 1) pond pine woodland be established on mineral and histic soils; 2) non-riverine swamp forest be established on shallow organic soils; and 3) high pocosin and bay forest be established on deep organic soils.

Effects of light and temperature on germination of Pyxidanthera brevifolia Wells (Diapensiaceae) 1

Abstract Pyxidanthera brevifolia is an evergreen semi-woody cushion plant endemic to the Sandhills of North and South Carolina, with the majority of populations occurring on Fort Bragg Military Reservation in North Carolina. Currently the species is listed as Endangered in North Carolina and is designated as a Species at Risk (SAR) by the US Department of Defense. Previous studies have suggested that seeds may not be viable because they failed to germinate under controlled conditions. Our objectives in this study were to attempt germination of Pyxidanthera brevifolia seeds, determine the best temperature conditions for germination, and understand more about germination requirements to aid in future restoration efforts. Using seeds that had been stored at room temperature for six months, we performed a germination experiment at the NCSU Phytotron with six treatments, all combinations of three temperature regimes (low (18 °C day / 14 °C night), medium (22/18 °C), and high (26/22 °C)) and two light conditions (light and dark). We monitored the experiment for 13 weeks, recording the number of seeds germinating per dish and the number of days to germination for seeds in each treatment. We found that Pxyidanthera brevifolia produces germinable seeds and that there are significant effects of light and temperature on germination. Highest germination occurred under low temperature and high light conditions (78%); the combination of high temperature and no light produced the lowest germination (6%). Seeds exposed to light germinated significantly earlier at the coolest temperature, compared to medium and high temperatures. These results indicate that it is possible to germinate seeds of this rare plant and suggest that germination of Pyxidanthera brevifolia likely occurs in late fall and is dependent on adequate light availability.

Trait space of rare plants in a fire-dependent ecosystem

The causes of species rarity are of critical concern because of the high extinction risk associated with rarity. Studies examining individual rare species have limited generality, whereas trait-based approaches offer a means to identify functional causes of rarity that can be applied to communities with disparate species pools. Differences in functional traits between rare and common species may be indicative of the functional causes of species rarity and may therefore be useful in crafting species conservation strategies. However, there is a conspicuous lack of studies comparing the functional traits of rare species and co-occurring common species. We measured 18 important functional traits for 19 rare and 134 common understory plant species from North Carolinas Sandhills region and compared their trait distributions to determine whether there are significant functional differences that may explain species rarity. Flowering, fire, and tissue-chemistry traits differed significantly between rare and common, co-occurring species. Differences in specific traits suggest that fire suppression has driven rarity in this system and that changes to the timing and severity of prescribed fire may improve conservation success. Our method provides a useful tool to prioritize conservation efforts in other systems based on the likelihood that rare species are functionally capable of persisting.

Operational-scale demonstration of propagation protocols and comparative demographic monitoring for reintroducing five southeastern endangered and at-risk plants : final report

Georgia leadplant (Amorpha georgiana) seedlings NCBG is currently part of a collaborative research project with the US Army Corps of Engineers, and the Department of Defense. The overall objective of this project is to conduct an operational-scale demonstration of recently developed propagation protocols for reintroducing one endangered and four at-risk plant species that occur across multiple military installations in the Southeast. Our specific objectives are to (1) demonstrate that four populations per target species can be successfully reintroduced, (2) identify plant size classes most important in determining positive population growth rates using life table response experiments (LTRE), (3) optimize costs for establishment of self-sustaining populations using data collected from natural a populations, and (4) secure user acceptance.

Multiscale assessment of listed and at-risk species’ climate change vulnerabilities

Climate change is of concern to the U.S. Department of Defense because climate change-driven increases in the number of species Federally listed under the U.S. Endangered Species Act (ESA) and stress to listed species can lead to additional requirements and potential restrictions on training land use. A first step in guiding management strategies to promote climate change adaptation is to assess species’ vulnerabilities. However, vulnerability assessments conducted at a single scale or for arbitrary regions offer limited information to guide management decisions. This work developed and demonstrated an approach for multiscale species vulnerability assessments that integrates weighted estimates of range-wide and local vulnerability, and vulnerability on Federal land, where species’ occurrence often influences ESA listing decisions. The approach was applied to 16 plant and animal species on five regionally representative Army installations. The assessments were used to rank species based on their occurrence on multiple installations across the Army and to rank the five study installations based on aggregate species’ vulnerabilities. This approach is suitable for integrating climate change considerations into installation Integrated Natural Resource Management Plans, for evaluating whether climate change-driven impacts to listed species will affect installation resilience, and for identifying potential conservation partners among Federal land managers. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CERL TR-17-21 iii

Canebrakes of the Sandhills Region of the Carolinas and Georgia: Fire History, Canebrake Area, and Species Frequency

ABSTRACT  Canebrakes formerly occupied hundreds of thousands of hectares across the southeastern USA, but habitat conversion and fire suppression have reduced their size and extent. Currently, canebrakes are among the rarest vegetative communities in the southeastern USA. Research has focused on Arundinaria gigantea (river cane), with very little focus on Arundinaria tecta (switch cane). The fire history, area, associated flora, and species frequency of 13 canebrakes, dominated by switch cane, were examined at three Department of the Army locations and one game land in the Sandhills physiographic region. We determined canebrake area by identifying its unique vegetative signature in aerial photography at three time steps: earliest aerial photography, the beginning of the recorded burn history, and current aerial photography. We compared fire-return intervals to changes in canebrake area. We created a checklist and tallied 330 taxa of vascular plants (plus Sphagnum sp.) from the 13 canebrakes in our study and calculated species frequency. Estimated area of the 13 observed canebrakes has increased from 25.6 ha historically to 592.8 ha. Mean fire-return interval is within a range of 1–2.3 yr. As fire-return intervals decrease, canebrake area increases, but that increase starts to decline after 2 yr. The highest number of taxa recorded for individual canebrakes were found on Fort Jackson, South Carolina, at Buffalo Creek (236 species) and Fort Bragg, North Carolina, at Black Creek (201 species). Species frequency demonstrates that canebrakes are capable of supporting a mix of herbaceous, shrubby, and arboreal species, which includes rare taxa.

Lost and Found: Remnants of the Big Savannah and Their Relationship to Wet Savannas in North Carolina

Abstract Conversion to agriculture and plantations, development, and fire suppression have reduced the extent of savannas in the southeastern United States, and there is a need to catalog and classify the remaining savannas for both restoration and resource management purposes. The Big Savannah was a wet savanna in North Carolina that was destroyed in the 1950s, and subsequent vegetation classifications have generally not accommodated well the unique natural plant community of the Big Savannah. Vegetation reminiscent of that described for the Big Savannah was discovered north of the original site and designated as Wells Savannah. To evaluate the uniqueness of the savanna vegetation at Wells Savannah, we compiled a data set from permanent quadrats with information on vegetation and environmental variables from other Outer Coastal Plain savannas to compare with similar data from the natural community at Wells Savannah. We also inventoried an additional 26 quadrats on a tract adjacent to Wells Savannah that had experienced fire suppression. Results from multivariate analyses demonstrated clear differences between the Wells Savannah quadrats and other regional wet savanna quadrats based on both vegetation and soils. A number of species and several soil characteristics (higher clay percentage, and higher available iron and boron) distinguish Wells Savannah from other wet savannas. Although the fire suppressed quadrats near Wells Savannah had lower species richness, typical savanna species such as Ctenium aromaticum and Calamovilfa brevipilis were still present. Further exploration of fire-suppressed tracts in the area may yield more wet savanna inclusions similar to the former Big Savannah.