The Role of Seed Bank and Germination Dynamics in the Restoration of a Tidal Freshwater Marsh in the Sacramento–San Joaquin Delta

Liberty Island, California, is a historical freshwater tidal wetland that was converted to agricultural fields in the early 1900s. Liberty Island functioned as farmland until an accidental levee break flooded the area in 1997, inadvertently restoring tidal marsh hydrology. Since then, wetland vegetation has naturally recolonized part of the site. We conducted a seed bank assay at the site and found that despite a lack of germination or seedling recruitment at the site, the seed bank contained a diverse plant community, indicating that the site’s continuous flooding was likely suppressing germination. Additionally, the frequency of germinating seeds in the seed bank did not represent the dominant adult plant community. We conducted a cold stratification study to determine if this observed disparity could be explained by seed germination dynamics, and whether germination could be enhanced using a pre-germination cold exposure, particularly for species of concern for wetland restoration. The cold stratification study showed that longer durations of pre-germination cold enhanced germination in Schoenoplectus acutus, but reduced germination in Schoenoplectus californicus, and had no effect on Typha latifolia. Overall, germination of S. californicus and S. acutus was much lower than T. latifolia. Our findings suggest that seeding may not be an effective restoration technique for Schoenoplectus spp., and, to improve restoration techniques, further study is needed to more comprehensively understand the reproduction ecology of important marsh species

Intraspecific Variation in Salt Tolerance in Panicum Hemitomon, Spartina Patens, and Spartina Alterniflora: Population Differentiation and Investigations of Underlying Factors.

Although it is known that wetland plant species exhibit considerable interspecific variation in salt tolerance across coastal plant communities, very little is known concerning the amount of intraspecific variation in salt tolerance within plant species. Panicum hemitomon, Spartina patens and Spartina alterniflora are dominant emergent macrophytes of fresh, brackish and salt marshes, respectively. To investigate intraspecific variation in salt tolerance, plant material was collected from Gulf Coast populations of each of these species and subjected to a salinity screening protocol. All three of the plant species displayed significant intraspecific variation in lethal salinity level and plant morphology. Lethal salinity levels ranged from 7.67\perthous to 12.0\perthous in Panicum hemitomon, from 63\perthous to 93\perthous in Spartina patens, and from 83\perthous to 115\perthous in Spartina alterniflora. Population morphological differences were most correlated with salt tolerance in Panicum hemitomon, the fresh marsh dominant and least correlated with Spartina alterniflora, the salt marsh dominant. Investigations conducted at sublethal salinity levels on subsets of populations showed that plant photosynthetic response was able to differentiate highly salt-tolerant and poorly salt-tolerant populations within each species to varying degrees. These differences were greatest in Panicum populations, with the highly salt-tolerant populations having higher photosynthetic rates and greater water use efficiencies. Highly salt-tolerant populations of Panicum hemitomon and Spartina patens were able to limit the total cation concentrations in their leaves, maintain greater leaf xylem pressures, and accumulate less proline than poorly salt tolerant populations, but apparently had only limited control over the ionic composition. Conversely, Spartina alterniflora populations showed no differences in leaf total cation concentrations, but the highly salt-tolerant populations were able to selectively decrease their Na:K ratio and accumulate more glycinebetaine than poorly salt-tolerant populations. It is concluded that in Panicum hemitomon plant size factors and photosynthetic rates are important in explaining population differences in salt tolerance by providing more mature tissue for the translocation of salts away from actively growing regions. The importance of plant morphology decreases as physiological/biochemical responses become progressively more important in explaining intraspecific variation in salt tolerance in Spartina patens and Spartina alterniflora

Stable and Sporadic Symbiotic Communities of Coral and Algal Holobionts

Coral and algal holobionts are assemblages of macroorganisms and microorganisms, including viruses, Bacteria, Archaea, protists and fungi. Despite a decade of research, it remains unclear whether these associations are spatial-temporally stable of species-specific. We hypothesized that conflicting interpretations of the data arise from high noise associated with sporadic microbial symbionts overwhelming signatures of stable holobiont members. To test this hypothesis, the bacterial communities associated with three coral species (Acropora rosaria, Acropora hyacinthus and Porites lutea) and two algal guilds (crustose coralline algae and turf algae) from 131 samples were analyzed using a novel statistical approach termed the Abundance-Ubiquity (AU) test. The AU test determines whether a given bacterial species would be present given additional sampling effort (that is, stable) versus those species that are sporadically associated with a sample. Using the AU test, we show that coral and algal holobionts have a high-diversity group of stable symbionts. Stable symbionts are not exclusive to one species of coral or algae. No single bacterial species was ubiquitously associated with one host, showing that there is not strict heredity of the microbiome. In addition to the stable symbionts, there was a low-diversity community of sporadice symbionts whose abundance varied widely across individual holobionts of the same species. Identification of these two symbiont communities supports the holobiont model and calls into question the hologenome theory of evolution

A General Algorithm for Reusing Krylov Subspace Information. I. Unsteady Navier-Stokes

A general algorithm is developed that reuses available information to accelerate the iterative convergence of linear systems with multiple right-hand sides A x = b (sup i), which are commonly encountered in steady or unsteady simulations of nonlinear equations. The algorithm is based on the classical GMRES algorithm with eigenvector enrichment but also includes a Galerkin projection preprocessing step and several novel Krylov subspace reuse strategies. The new approach is applied to a set of test problems, including an unsteady turbulent airfoil, and is shown in some cases to provide significant improvement in computational efficiency relative to baseline approaches

Schaffnerella Rediscovered! (Gramineae, Chloridoideae)

From 1876 to 1880 in San Luis Potosí, Mexico, J. G. Schaffner made the first collections of a small grass that later was named Schaffnerella gracilis (Chloridoideae). The monotypic genus apparently was not encountered again by botanists until 2001, when, during a targeted search, we discovered it in the Sierra de San Miguelito growing along the Río Potosino, ca. 6 air km southwest of the city of San Luis Potosí. Most of the 100-150 plants encountered along a 3-km stretch of the Río Potosino above the village of Escalerillas and reservoir EI Potosino were growing in a moist alluvium of rock and sand. Historically known to occur some 10 km or more downstream near Morales, a village at the western edge of the city of San Luis Potosí, S. gracilis has been impacted adversely by the creation of dams. Much additional field work is required to determine the geographic range and frequency of the species. Also needed are life history and population-level studies

Neurochemical enhancement of conscious error awareness

How the brain monitors ongoing behavior for performance errors is a central question of cognitive neuroscience. Diminished awareness of performance errors limits the extent to which humans engage in corrective behavior and has been linked to loss of insight in a number of psychiatric syndromes (e.g., attention deficit hyperactivity disorder, drug addiction). These conditions share alterations in monoamine signaling that may influence the neural mechanisms underlying error processing, but our understanding of the neurochemical drivers of these processes is limited.Weconducted a randomized, double-blind, placebo-controlled, cross-over design of the influence of methylphenidate, atomoxetine, and citalopram on error awareness in 27 healthy participants. The error awareness task, a go/no-go response inhibition paradigm, was administered to assess the influence of monoaminergic agents on performance errors during fMRI data acquisition. A single dose of methylphenidate, but not atomoxetine or citalopram, significantly improved the ability of healthy volunteers to consciously detect performance errors. Furthermore, this behavioral effect was associated with a strengthening of activation differences in the dorsal anterior cingulate cortex and inferior parietal lobe during the methylphenidate condition for errors made with versus without awareness. Our results have implications for the understanding of the neurochemical underpinnings of performance monitoring and for the pharmacological treatment of a range of disparate clinical conditions that are marked by poor awareness of errors

Changes in frailty among ICU survivors and associated factors:Results of a one-year prospective cohort study using the Dutch Clinical Frailty Scale

Contains fulltext : 214092.pdf (Publisher’s version ) (Open Access

A VLA Search for Water Masers in Six HII Regions: Tracers of Triggered Low-Mass Star Formation

We present a search for water maser emission at 22 GHz associated with young low-mass protostars in six HII regions -- M16, M20, NGC 2264, NGC 6357, S125, and S140. The survey was conducted with the NRAO Very Large Array from 2000 to 2002. For several of these HII regions, ours are the first high-resolution observations of water masers. We detected 16 water masers: eight in M16, four in M20, three in S140, and one in NGC 2264. All but one of these were previously undetected. No maser emission was detected from NGC 6357 or S125. There are two principle results to our study. (1) The distribution of water masers in M16 and M20 does not appear to be random but instead is concentrated in a layer of compressed gas within a few tenths of a parsec of the ionization front. (2) Significantly fewer masers are seen in the observed fields than expected based on other indications of ongoing star formation, indicating that the maser-exciting lifetime of protostars is much shorter in HII regions than in regions of isolated star formation. Both of these results confirm predictions of a scenario in which star formation is first triggered by shocks driven in advance of ionization fronts, and then truncated approximately 10^5 years later when the region is overrun by the ionization front.Comment: 30 pages, 20 figures, 3 tables. Accepted for publication by ApJ. Full resolution figures and PS and PDF versions with full-res figures available at http://eagle.la.asu.edu/healy/preprints/hhc0