The Paullinieae tribe (Sapindaceae) has stems with structural variation highly specialized and unique to this tribe: divided vascular cylinder, compound vascular cylinder and corded vascular cylinder. In Brazil, these stems are used in wood marquetry. The present study is the first to explore the ontogeny of the corded stem through the analysis of Thinouia restingae, an endemic species in Brazil. A normal vascular cambium arises as a continuous cylinder and functions for a long time producing secondary phloem centrifugally and secondary xylem centripetally. New cambia are formed by the pericycle giving rise to the peripheral vascular cylinder. The variant cambia are circular and have cambial activity similar to the regular cambium. Morphologically, the corded type is similar to the compound type. However, while the ontogenesis and presence of pith is found in the compound type, these features are absent in the corded vascular cylinder. Overall, we found that the corded stem of Thinouia restingae differs from other cable structures present in Sapindaceae by its macromorphology, tissue structure, and developmental timing. The commercial importance of Sapindaceae wood gives our findings particular significance in that our study serves as a first step toward incorporating developmental data into the identification of the wood of lianas commercially.

Caloplaca yuchiorum, a saxicolous sorediate species, is described as new to science based on collections from localities in Oklahoma, South Carolina, and Texas, USA.

Persicaria extremiorientalis is native to Japan, the Russian Far East, China, and Korea. It is documented here with specimens from the Atlantic coastal region including the states of Connecticut, New York, New Jersey, Maryland and North Carolina. The earliest collections in North America are from Queens, New York in 1961. The species belongs to Persicaria section Persicaria, and is distinguished from all other North American species by the combination of stems usually hispid or sparsely pilose with long, soft hairs; ocrea outer surfaces strigose and the apices setose; leaf blades eglandular and the abaxial surfaces golden-strigose; racemes dense, often nodding, the bracts short-ciliate; achenes small, brown, lenticular or biconcave (rarely trigonous) and basally tumescent. The existence of this species in North America is substantiated with herbarium specimens and a full description and an identification key to it and related species are provided.

Plant uptake of soil organic N in addition to inorganic N could play an important role in ecosystem N cycling as well as plant nutrition. We measured in situ plant uptake of organic and inorganic N by the dominant canopy species in two contrasting temperate forest ecosystems (bottomland floodplain forest, subxeric sandhills long-leaf pine forest). Seedlings of Acer rubrum L. and Pinus palustris Mill. in floodplain and sandhills forests, respectively, were treated with isotopically-enriched organic N (¹⁵N-[2]-¹³C-glycine) or inorganic N (¹⁵NH₄ ) to examine in situ uptake. We also measured soil organic and inorganic N concentrations to assess the availability of N for plant uptake. Neither species took up organic N as intact ¹⁵N-[2]-¹³C-glycine, but significant root ¹⁵N enrichment in both species indicated that N mineralized from labeled glycine was taken up. Free amino-N dominated the total 2 M KCl-extractable N in floodplain (57 ± 3%) and sandhills soils (75 ± 3%), followed by NH₄ then NO₃⁻ in both soils. Up to 13% of glycine label was mineralized to NH₄ at both sites, suggesting that the majority of label was immobilized or adsorbed in the soil. Recovery of NH₄ label also indicated strong soil immobilization, particularly in sandhills soils after 24 hours. Although uptake of intact organic N did not occur in either species, N mineralized from glycine was taken up by plants in these two contrasting temperate forested ecosystems.

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.

Plant population growth and persistence are strongly influenced by germination and recruitment, which can be dramatically affected by seed dormancy, local site conditions, seed size and seed predation. Understanding factors that limit germination can help to explain low recruitment rates and is particularly important for species of conservation concern. Desmodium cuspidatum has declined dramatically in the northeastern United States and is currently listed as historic, threatened or endangered in all five New England states where it once occurred. Remaining populations exhibit low reproductive success and low recruitment rates, even though seed viability is nearly 100%. Requirements for optimal germination, including the breakdown of physical dormancy, effect of local site characteristics, and seed mass were largely unknown. In addition, while recruitment rates in co-occuring Desmodium species are reportedly higher than those of D. cuspidatum, germination rates in these species were unavailable for comparative purposes. Lastly, the effect of pre-dispersal seed predation, commonly observed in Desmodium species, was unknown. We performed a series of three controlled experiments to assess optimal conditions for germination (D. cuspidatum), the relationship between germination rate and seed size (mass, D. cuspidatum, D. glutinosum and D. paniculatum) and the effect of pre-dispersal seed predation on germination (D. canadense and D. paniculatum). Our results suggest that low recruitment rates observed in New England populations of D. cuspidatum are related to physical dormancy and local site conditions, whereby the highest germination rates are found when seeds are placed on bare soil, regardless of whether they are covered with leaf litter. Germination rates in D. cuspidatum were generally lower than those observed for two more common Desmodium species, D. glutinosum, and D. paniculatum and were positively correlated with seed mass in all three species. Seeds grown with field-collected soil had lower germination rates but higher nodulation rates than those grown in sterilized potting soil. Seed predation by weevils had no detectable difference on germination rates in D. paniculatum and D. canadense.

As a highly aggressive non-native invasive and an allelopathic species, Ailanthus altissima (tree of heaven) has the capacity to negatively affect native plant communities by suppressing resident species and altering competitive interactions. We examined effects of A. altissima on the establishment and growth of two herbaceous species common in invaded natural areas. Soil samples were collected from six replicate A. altissima-dominated stands and six control stands (no A. altissima present) in the Appalachian Ridge and Valley province of southwestern Virginia. Two target species, Verbesina occidentalis, native to the southeastern US, and Dipsacus fullonum, non-native and invasive throughout North America, were selected for their high germination success and contrasting native vs. invasive status. Germination and growth of target species were monitored in greenhouse flats for six weeks. We found severe reductions in all measured aspects of V. occidentalis when grown in Ailanthus versus control soils, including seed germination (P  =  0.002), seedling height (P  =  0.001), leaf production (P < 0.001), and root∶shoot ratio (P  =  0.008). In contrast, Dipsacus fullonum appeared resistant to allelopathic effects, with no significant differences in germination or growth relative to soil type (P > 0.25 for all measures). Our results support the role of allelopathy in the invasive success of A. altissima and further suggest that A. altissima may differentially affect resident native versus non-native species, potentially facilitating the spread of other non-natives in the invaded community.

Lycopod and fern species richness and beta diversity were analyzed along elevation gradients in different vegetation types in the Los Mármoles National Park (PNM) in the state of Hidalgo, Mexico. Sampling was conducted at 16 sites located between 1,184 and 2,702 m elevation, including eight vegetation types. Observed species richness was compared with expected species richness using non-parametric methods. The number of shared species and the lycopod and fern species replacement rate were estimated between vegetation types (beta diversity). The number of lycopod and fern species was low at the high and low extremes of the elevation gradient, while at intermediate elevations species richness ranged from low to high. This species richness and distribution pattern for lycopods and ferns is probably related to elevation (moisture), topography and vegetation type. Sampling effort efficiency was 86 to 91%, depending on the estimator used. Beta diversity of these vascular sporogenous plants between vegetation types was high, which was considered to be a reflection of the considerable micro-environmental differences related to tolerance to water availability and other environmental factors.

We documented microhabitat occurrence and growth of Lonicera japonica to identify factors related to its invasion into a southern Illinois shale barren. The barren was surveyed for L. japonica in June 2003, and the microhabitats of established L. japonica plants were compared to random points that sampled the range of available microhabitats in the barren. Vine and leaf characters were used as measurements of plant growth. Lonicera japonica occurred preferentially in areas of high litter cover and species richness, comparatively small trees, low PAR, low soil moisture and temperature, steep slopes, and shallow soils. Plant growth varied among these microhabitats. Among plots where L. japonica occurred, growth was related to soil and light conditions, and aspects of surrounding cover. Overhead canopy cover was a common variable associated with nearly all measured growth traits. Plasticity of traits to improve invader success can only affect the likelihood of invasion once constraints to establishment and persistence have been surmounted. Therefore, understanding where L. japonica invasion occurs, and microhabitat interactions with plant growth are important for estimating invasion success.

This study examined the relationship between direction of treefall, slope-aspect and prevailing wind in five old-growth stands where single-tree canopy gaps characterize the dominant disturbance regime. All live and downed trees were inventoried in 0.45-ha sample plots, and crown sizes of live trees were measured along two perpendicular axes. Directions of fall and slope-aspect of downed trees also were recorded. Regional prevailing winds and wind gusts were obtained from four nearby airports. I used circular statistics to determine if directions of treefall for each study stand had a mean direction or if the directions of fall were uniformly distributed. If directions of treefall had a true mean, they were then compared to mean slope aspect and prevailing wind directions. At two of eight plots, treefall directions were uniformly distributed (i.e., no mean direction). Only one plot showed a statistically significant similarity between mean slope-aspect and mean direction of fall, and only three of the eight study plots showed statistically significant similarities between mean treefall and wind directions. Mean crown asymmetry (ratio of long and short diameters) was 1.26, and there were no significant differences in asymmetry values when current gap border trees and non border trees were compared. While trees may fall downhill and downwind, the high variation in treefall and wind directions precluded establishing a consistent statistical relationship between these data sets. I suggest that crown asymmetry, resulting from differential crown growth of trees on sloped-hillsides and within canopy gaps, exerts a strong additional influence on direction of fall.

The hemlock-silverbell (Tsuga canadensis-Halesia tetraptera) association is endemic to several small stands in federally protected lands in the southern Appalachian Mountains and is currently threatened by the hemlock woolly adelgid (Adelges tsugae). Pre-infestation stand structure was still evident at the time of the study but hemlock mortality and associated vegetation responses portend rapid changes in this system. In order to guide potential future restoration efforts and impact assessments, a study was implemented to determine the structure of hemlock-silverbell stands and to identify environmental variables associated with differences in stand composition in areas of Great Smoky Mountains National Park treated to control hemlock woolly adelgid. Halesia tetraptera and T. canadensis exhibited even-aged and uneven-aged stand structures, respectively. Forest composition varied as a function of environmental variables within the hemlock-silverbell association with overstory H. tetraptera relative density positively correlated with higher water availability (Beers aspect and slope) and overstory T. canadensis was negatively correlated with Beers aspect. Relative density of H. tetraptera and T. canadensis in the understory were similarly associated with higher and lower productivity conditions, respectively. In the understory, Acer pensylvanicum relative density was negatively associated with that of understory T. canadensis. The results suggest that partial canopy removal resulting from the loss of T. canadensis due to hemlock woolly adelgid may benefit aggressive tree species such as A. pensylvanicum. The United States Park Service vegetation management policies, here and in other natural areas where non-native invasive species are controlled (but native species responses are unaccounted for), will need to address this phenomenon if T. canadensis restoration is to be accomplished in the event adelgid control can be achieved.

The abundance of old-growth associated herbs in young Pseudotsuga menziesii forests is limited in part by the low availability of propagules of these species, but it remains unclear whether the slow post-logging development of old-growth species in younger forests also reflects a lack of microhabitats suitable for seed germination. This study attempts to fill an almost total lack of knowledge about germination of understory species in second-growth Douglas-fir forests, and in young coniferous forests in general, while providing a preliminary exploration of the relative importance of these two limiting factors. The ability of six common forest herbs to germinate in a 40-year-old Pseudotsuga menziesii stand was tested, and survival and growth were monitored for seven years. Five of the six species germinated well (8–50% germination), while one open-site species failed to germinate. After seven years, survival of four old-growth associated species was ∼10% (of the original seed number), while only 1% of seeds of a disturbance-adapted species were still present as seedlings. For all species, seedlings grew slowly and did not reach reproductive size, forming a seedling bank analogous to that of shade-tolerant tree seedlings. All old-growth associated species showed higher overall seedling numbers or greater survival in gaps than in non-gap microsites, and two species showed higher survival in the more mesic lower part of the watershed. Naturally occurring seedlings were rare and included only easily dispersed species that are forest generalists or characteristic of mature, but not of old-growth forests. I conclude that germination of late-seral herb species in young Pseudotsuga menziesii forests is not strictly microsite limited, but that these species are instead limited by a combination of low propagule availability and low resource levels with concomitant slow growth rates.

Native grasses and forbs are an important component of the longleaf pine (Pinus palustris Mill.) ecosystem; however, information about re-establishment of these species in a restoration context has become available only recently. Understanding the effects of herbicides on non-target native plants can advance the use of herbicides as an effective restoration tool in the control of competing vegetation and in maintenance of seed production fields. The objectives of this study were to determine the effects of several commonly used herbicides on non-target species of grasses, legumes, and composites native to the longleaf pine ecosystem of southwestern Georgia. We assessed the pre- and post-emergent properties of nine herbicides on ten species of grasses, legumes, and composites. For each species, we examined phytotoxic responses to two rates (low rate and high rate) of herbicide at three stages of plant growth: 0 (pre-emergent), 30, and 60 d post-emergent. Plants were visually rated for leaf damage 30 d after herbicide application to assess the phytotoxic effects of the herbicides. Plants were then harvested, dried, and weighed. Regardless of herbicide application rate or age of plant, legumes were extremely vulnerable to applications of aminopyralid, triclopyr, and hexazinone. Most pre-emergent grasses were vulnerable to triclopyr when applied at the high rate. Most 30-day-old grasses were killed when treated with the high rate of hexazinone. Our results indicate that several native species are more sensitive to herbicide application than expected based on the below maximum label rates used and the specificity implied on the herbicide labeling.