Bidens alba (L.) DC. var. radiata (Sch. Bip.) R. E. Ballard in T. E. Melchert (ASTERACEAE)— LOUISIANA, Orleans Parish: New Orleans, ruderal areas along sidewalk next to gas station…
Ceratopteris thalictroides (L.) Brongn. (PARKERIACEAE)—
MISSISSIPPI, Jackson County: Whiskey Bayou of the Pascagoula River basin,
W of Escatawpa, semiattached to a mostly submerged and rotten log in bayou…
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Leucojum aestivum L. (AMARYLLIDACEAE)—
PENNSYLVANIA, Crawford County: Meadville
Diarrhena obovata (Gleason) Brandenburg is a woodland grass primarily of the central United States in the Mississippi River drainage (Brandenburg et al. 1991). Isolated occurrences of D. obovata in the Appalachian and Piedmont regions of the mid-Atlantic states have been found in the last several decades, and the species is or has been considered to be a rare native species in Pennsylvania (Rhoads and Klein 1993); in West Virginia, Virginia, and New York (NatureServe 2011); and (as Diarrhena americana Beauv.) in Maryland (Maryland Natural Heritage Program 2003).
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ABSTRACT A comprehensive survey of the vascular flora of a constructed wetland in Grady County, Georgia was conducted at monthly intervals between August 2004 and May 2006. The constructed wetland is used as a part of a nutrient remediation system to improve the sustainability of plant nursery water-handling practices. The survey evaluated vegetation in a 3.1 ha, two-stage constructed wetland consisting of two deep cells (Stage 1; mean depth 0.75 m) totaling 1.8 ha that drain into two shallow cells (Stage 2; mean depth 0.2 m) totaling 1.3 ha. Each cell was band planted in 1997 with seedlings or liners of six wetland plant species. During the 2-yr survey, 141 distinct species were collected from the 3.1 ha constructed wetland; of the taxa collected, there were 101 genera from 51 families. Native taxa made up 76.6% of the species recorded, and 24.1% of the taxa were introduced. Hydrophytic plants accounted for 68.1% of the plants collected and the remainder (31.9%) were classified as nonhydrophytes. Because 57.4% of the taxa surveyed were perennial, it is likely that plant propagules introduced by wildlife (waterfowl, reptiles, and amphibians) were the dominant method of plant introduction rather than primary succession. Vascular plant community diversity increased 24-fold during the 9-yr period after constructed wetland installation. Key words: Hydrophyte, macrophyte richness, plant nursery, self-design, treatment wetland.
This addendum to Helm (2010) describes an additional condition to be met when converting and comparing frequencies of randomly distributed plants. Density (number of plants of interest per sample plot area) and frequency (fraction of sample plots with presence of a plant of interest, expressed per sample plot area) can be influenced by plot edge (i.e., plot boundary) effects that differ based on plot shape and size. Abundance comparisons should consider stem base diameter (or size of whatever character is used to establish presence) relative to plot area and distance between plot edges. Base of stem contained entirely within a plot is a common criterion for presence. Concerns could arise, for example, with abundance comparisons in studies that used differently shaped or sized plots, where stem bases are large and may be evident as occurring on both sides of a plot edge (i.e., the plot edge bisecting the stem).
As plot edge length relative to plot size (‘‘edge-to-area ratio’’) increases, the expected percentage of stem bases only partially contained within a plot increases. Edge length refers to the perimeter of a plot, the circumference of a circle, for example. Edge-to-area ratio increases with decreasing plot area of a given shape and differs among plot shapes of a given area, with this ratio increasing from circles to squares to rectangles to thinner rectangles. For example, as a rectangular plot becomes thinner while maintaining a given area, edge length increases. This increase continues to a plot dimension where the long-side edges of a plot become so close to each other that all stems recorded would be only partially contained because stem base diameters would exceed plot width. This would result in a misleading frequency and density of zero, if the criterion for presence requires that stem bases be contained entirely within plots. This is not a practical circumstance but illustrates progression to the most extreme case of edge effects. Greig-Smith (1983) advised against using plots that have high edge-to-area ratios, such as elongated rectangles. Circular or square plots, both of which have low edge-to-area ratios, are recommended and commonly used.
If the criterion for presence under random spatial distribution is based on a dimensionless point, such as the center of a stem for example, edge-to-area ratios are not of concern because those points can not be classified as contained partially within a plot. Edge effects are inconsequential when stem base diameter is small relative to plot area and distance between plot edges, which is typically the case in studies on understory plants because of thin stems and the use of circular or square plots.
Because of edge effects on abundance measures, the additional condition to be met is that the stem-base diameter (or size of whatever character is used to establish presence) is small relative to plot area and to the distance between plot edges such that the character used to establish presence may be reasonably recorded as occurring entirely within a plot or entirely outside a plot, as is typical in studies on understory plants.
LITERATURE CITED Greig-Smith, P. 1983. Quantitative plant ecology, 3rd ed. University of California Press, Berkeley, California.
Helm, S.R. 2010. A calculation of expected plant frequency. Castanea 75:226–231.
ABSTRACT Harperella (Harperella nodosum) is the only federally listed endangered plant species in the Chesapeake and Ohio Canal National Historical Park (C&O Canal NHP) in the National Park Service in Maryland and one of four federally listed endangered plant species in West Virginia. This paper contrasts unsuccessful and successful efforts to reintroduce harperella seedlings in the main stem of the flood-prone Potomac River and on opposite sides of the river in damp sites in western Maryland and in streams in northeastern West Virginia. The reintroduction efforts in Maryland unsuccessfully transplanted seedlings on cobble bars on the Maryland side of the Potomac River and in artificial sites in the prism of the C&O Canal where harperella had never been found; the reintroduction efforts in West Virginia successfully transplanted seedlings on cobble bars in two tributaries of the Potomac River in West Virginia where harperella populations once flourished but in the last decade or so had been decimated by floods and ice damage. This investigation has contributed to defining harperella’s life-cycle characteristics and ecological requirements. The data and observations presented can be used as a guide for reintroducing harperella seedlings and, by extension, other semiaquatic plant species into appropriate sites.
ABSTRACT Three sites with populations of federally endangered golden sedge (Carex lutea LeBlond) were sampled to investigate whether circumneutral soil conditions were associated with a species distribution restricted to 208 km2 within two adjacent counties of the lower North Carolina Coastal Plain. Populations were selected to include different soil series found in a stateowned natural area. Observed golden sedge rhizome and root depths among three specimens, one per site, ranged from 6 to 8 cm below the soil surface, which suggested primarily topsoil influence. A total of 96 soil samples, 48 topsoil and 48 subsoil, were collected in transects and analyzed. Mean pH values within populations were very strongly (4.7) to moderately (5.7) acid for topsoils and moderately (5.8) to slightly (6.5) acid for subsoils. These values did not differ significantly inside versus immediately outside each population, but varied among topsoils and subsoils between populations. Other soil variables associated with marl and limestone parent material influence (i.e., cation exchange capacity, base saturation, calcium, and magnesium) did not exhibit any consistent trends either inside versus outside, or between populations. A prior study found a mean soil pH of 6.7 within golden sedge populations, but choices of sample sites and analysis techniques were questionable. Lack of soil specificity for this species encourages both searches for golden sedge populations outside the known range and restoration or enhancement of local populations.
ABSTRACT Hemlock woolly adelgid, Adelges tsugae, is spreading throughout the northeastern United States, causing large-scale dieback of the eastern hemlock, Tsuga canadensis. This study examined soil nitrogen transformations and stream water nitrogen content at five hemlock-dominated stands in southern Pennsylvania, spanning a spectrum of hemlock mortality, from no mortality to total A. tsugae–induced mortality with subsequent regrowth. Organic content, extractable nitrate, and net nitrification and mineralization rates, as well as nitrate and ammonium movement through the soil were significantly higher at sites with high mortality. Our results suggest that stand-level hemlock mortality is leading to increased nitrogen inputs to stream water. Stream water nitrate concentrations were lowest at the site with little to no mortality (0.035 mg/L NO3 -) and highest at the site with intermediate mortality (0.69 mg/L NO3 -). In the sites with the longest time since infestation and highest mineralization and nitrification rates, regenerative seedling growth (Betula spp. in particular) is leading to increased uptake of nitrate, likely reducing nitrate leaching rates once substantial regeneration occurs. However, for a period of several years after infestation, hemlock dieback may be a significant source of nitrate in headwater streams, potentially altering headwater aquatic community composition and increasing downstream nutrient pollution
ABSTRACT North American Castanea consists of three morphologically variable species: Castanea dentata, Castanea pumila, and Castanea ozarkensis. Taxonomy of these species has been complicated by intermediate morphology, similarity in growth habit due, in part, to the chestnut blight, and putative naturally occurring hybridization in the southern Appalachians. The primary goal of this study was to determine if chloroplast DNA (cpDNA) distribution reflects the morphological variation observed in North American Castanea. To that end, we sequenced a single cpDNA gene region for 233 accessions collected from much of the range of the genus in North America. Once samples were grouped into haplotypes, we sequenced additional cpDNA regions to ensure that the observed haplotypic relationships were robust.We identified four main lineages and observed that for three of these, leaf and twig morphology are reliable predictors of haplotype identity (especially outside of the southern Appalachians). Haplotypes of the fourth lineage are shared among accessions of C. dentata and C. pumila, and trees with intermediate morphology. Geographic mapping of the haplotypes showed that they are largely found in separate geographic ranges but overlap in the southern Appalachians. While three clades closely correspond to the morphology of North American Castanea, it appears that the fourth lineage may have been recognized in the past as the hybrid taxon Castanea · neglecta because of its morphology that is intermediate between C. dentata and C. pumila.