Biomass, Litter, and Soil Respiration Along a Precipitation Gradient in Southern Great Plains, USA

Knowledge of how ecosystem carbon (C) processes respond to variations in precipitation is crucial for assessing impacts of climate change on terrestrial ecosystems. In this study, we examined variations of shoot and root biomass, standing and surface litter, soil respiration, and soil C content along a natural precipitation gradient from 430 to 1200 mm in the southern Great Plains, USA. Our results show that shoot biomass and soil respiration increased linearly with mean annual precipitation (MAP), whereas root biomass and soil C content remained relatively constant along the precipitation gradient. Consequently, the root/shoot ratio linearly decreased with MAP. However, patterns of standing, surface, and total litter mass followed quadratic relationships with MAP along the gradient, likely resulting from counterbalance between litter production and decomposition. Those linear/quadratic equations describing variations of ecosystem C processes with precipitation could be useful for model development, parameterization, and validation at landscape and regional scales to improve predictions of C dynamics in grasslands in response to climate change. Our results indicated that precipitation is an important driver in shaping ecosystem functioning as reflected in vegetation production, litter mass, and soil respiration in grassland ecosystems.     

Cytogenetic investigations in a new case of Bloom's syndrome

Summary Cytogenetic studies of an 8-year-old caucasian girl with typical but mild manifestation of Bloom's syndrome showed a characteristic increase of homologous chromatid translocations and prematurely condensed chromosomes. The average frequency of sister chromatid exchanges (SCE) in lymphocytes with 133 was much higher than in skin fibroblasts with 49. The inter- and intrachromosomal distributions of SCE in lymphocytes were analyzed.Prof. Dr. H.-R. Wiedemann to his 60th birthday.     

Roadless areas and biodiversity: a case study in Alabama,USA

Roadless areas are important for biodiversity maintenance and nature conservation but remain politically controversial due to conflicting interests of conservation and development. In this study, we applied a recently developed index of roadless volume (RV) across 67 counties of Alabama, USA as a case study to examine the relationships between roadless areas and local species richness. Our results indicated that with the increase of RV across counties, both the number of total fish and exotic fish species increased, but the relationship was not significant for endemic fish species. The number of both herpetofaunal and plant species also increased with the increasing RV. For all included species, there was a significant positive correlation between species richness and RV values. The number of endangered species decreased with the increase of RV per-capita. Wildfire occurrences increased with the increase of RV. Preserving roadless areas is an important component of biodiversity conservation.     

Pleuropulmonary melioidosis in a Cambodian refugee.

A 47-year-old Cambodian refugee presented with an acute respiratory illness that featured consolidation of the lower lobe of the left lung and progressive involvement of the adjacent pleura caused by Pseudomonas pseudomallei. Initial difficulty in identifying the organism resulted in an inadequate duration of therapy. Chronic pleural disease followed, and the organism became resistant to many antibiotics during therapy. A diagnosis of pleuropulmonary melioidosis should be entertained and the microbiology laboratory alerted when patients with pneumonia who are from endemic areas are encountered, so that a diagnosis can be made early and the appropriate treatment begun.     

Bottomland hardwood productivity: case study in a rapidly subsiding,Louisiana, USA,watershed

The Verret basin was formerly an overflow area between the Mississippi and Atchafalaya rivers and contains about 41,000ha of forested wetlands. Water levels are rising at the rate of over 1 cm/year in this area, and the forests are subjected to longer and deeper flooding. Tree growth, litterfall, and species composition were monitored across a flooding gradient during January 1985–December 1986. The driest area was only 20 cm higher in elevation than the wettest area, but the structure of the forest changes greatly over this range. The drier area was dominated by sweetgum (Liquidambar styraciflua L.), oaks (Quercus spp.), and sugarberry (Celtis laevigata Willd.), while green ash (Fraxinus pennsylvanica Marsh.), red maple (Acer rubrum L.), and baldcypress (Taxodium distichum (L.) Rich.) were dominant in the wetter area. Green ash and bitter pecan (Carya aquatica (Michaux. f.) Nutt.) were found in all plots, but these two species are under severe stress in the more flooded area as evidenced by dead and dying trees. Stem wood production increased from 1985 to 1986 in the driest (392 to 473 g/m²/yr) and wettest (199 to 399 g/m²/yr) plots, but remained relatively unchanged in the transitional area (386 to 380g/m²/yr). Leaf litter production decreased across the gradient from dry to flooded plots during both years. Over 40% of the litterfall in the drier plot was from flood-tolerant shrub species. In the flooded plots, red maple and baldcypress were major contributors to total litterfall. Increased flooding of dry bottomland forests in the future could lead to decreased litterfall and increased tree death over the entire watershed.     

Molecular, cytogenetic, and clinical investigations of Prader-Willi syndrome patients.

Thirty-seven patients presenting features of the Prader-Willi syndrome (PWS) have been examined using cytogenetic and molecular techniques. Clinical evaluation showed that 29 of these patients fulfilled diagnostic criteria for PWS. A deletion of the 15q11.2-q12 region could be identified molecularly in 21 of these cases, including several cases where the cytogenetics results were inconclusive. One clinically typical patient is deleted at only two of five loci normally included in a PWS deletion. A patient carrying a de novo 13;X translocation was not deleted for the molecular markers tested but was clinically considered to be "atypical" PWS. In addition, five cases of maternal heterodisomy and two of isodisomy for 15q11-q13 were observed. All of the eight patients who did not fulfill clinical diagnosis of PWS showed normal maternal and paternal inheritance of chromosome 15 markers; however, one of these carried a ring-15 chromosome. A comparison of clinical features between deletion patients and disomy patients shows no significant differences between the two groups. The parental ages at birth of disomic patients were significantly higher than those for deletion patients. As all typical PWS cases showed either a deletion or disomy of 15q11.2-q12, molecular examination should provide a reliable diagnostic tool. As the disomy patients do not show either any additional or more severe features than typical deletion patients do, it is likely that there is only one imprinted region on chromosome 15 (within 15q11.2-q12).     

Danazol in acquired amegakaryocytic thrombocytopenic purpura: a case report

Acquired amegakaryocytic thrombocytopenic purpura is a rare disease. Most reported patients did not respond to any therapeutical approach. Recently we observed a striking improvement of this disorder in a female patient shortly after therapy with danazol had been initiated. This observation and its possible implication for the treatment of amegakaryocytic thrombocytopenia are reported herein.     

Insights into the Establishment of the Manila Clam on a Tidal Flat at the Southern End of an Introduced Range in Southern California,USA

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam’s post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.     

A case study in resort climatology of Phoenix, Arizona, USA

Tourists often use weather data as a factor for determining vacation timing and location. Accuracy and perceptions of weather information may impact these decisions. This study: (a) examines air temperature and dew points from seven exclusive resorts in the Phoenix metropolitan area and compares them with official National Weather Service data for the same period, and (b) utilizes a comfort model called OUTCOMES—OUTdoor COMfort Expert System—in a seasonal appraisal of two resorts, one mesic and one xeric, compared with the urban Sky Harbor International Airport first-order weather station site in the central urban area of Phoenix, Arizona, USA (lat. 33.43°N; long. 112.02°W; elevation at 335 m). Temperature and humidity recording devices were placed within or immediately adjacent to common-use areas of the resorts, the prime recreational sites used by guests on most resort properties. Recorded data were compared with that of the official weather information from the airport station, a station most accessible to potential tourists through media and Web sites, to assess predicted weather for vacation planning. For the most part, Sky Harbor’s recorded air temperatures and often dew points were higher than those recorded at the resorts. We extrapolate our findings to a year-round estimate of human outdoor comfort for weather-station sites typical of resort landscapes and the Sky Harbor location using the OUTCOMES model to refine ideas on timing of comfortable conditions at resorts on a diurnal and seasonal basis.     

Sediment Contamination along Desert Wash Systems from Historic Mining Sites in a Hyperarid Region of Southern Nevada,USA

Abandoned mining sites in hyperarid environments are generally assumed to present an insignificant risk to water availability. This study investigated the impact abandoned mine sites in Southern Nevada can have on the wider environment. Southern Nevada is characterized with little precipitation and prolonged droughts. Precipitation in Southern Nevada is often in the form of short and intense events with the potential to mobilize and transport contaminated sediments down gradient. This work evaluated the movement of trace elements (Ag, As, Ba, Cd, Cr, Hg, Pb, and Se) and cyanide in surface sediments of three desert washes near the historic mining town of Nelson, a hyperarid region of Southern Nevada. Results indicate trace elements have been mobilized and transported down gradient from sources to areas not directly impacted by mining. Contaminants used in mining operations (Hg and CN^?) as well as those of geogenic nature migrated as far as 6000 m, providing evidence of their transport in hyperarid environments, contrary to the generally held belief. Although contaminants in this study are below levels that are environmentally significant, the findings show that transport is possible. This study demonstrates that large amounts of contaminant-laden sediments might be a significant threat in hyperarid environment and to areas down gradient from source materials.     

Establishment failure in biological invasions: a case history of Littorina littorea in California, USA

Background

The early stages of biological invasions are rarely observed, but can provide significant insight into the invasion process as well as the influence vectors have on invasion success or failure.

Methodology/Principal Findings

We characterized three newly discovered populations of an introduced gastropod, Littorina littorea (Linné, 1758), in California, USA, comparing them to potential source populations in native Europe and the North American East Coast, where the snail is also introduced. Demographic surveys were used to assess spatial distribution and sizes of the snail in San Francisco and Anaheim Bays, California. Mitochondrial DNA was sequenced and compared among these nascent populations, and various populations from the North American East Coast and Europe, to characterize the California populations and ascertain their likely source. Demographic and genetic data were considered together to deduce likely vectors for the California populations. We found that the three large California L. littorea populations contained only adult snails and had unexpectedly high genetic diversity rather than showing an extreme bottleneck as typically expected in recent introductions. Haplotype diversity in Californian populations was significantly reduced compared to European populations, but not compared to East Coast populations. Genetic analyses clearly suggested the East Coast as the source region for the California introductions.

Conclusions and Significance

The California L. littorea populations were at an early, non-established phase of invasion with no evidence of recruitment. The live seafood trade is the most likely invasion vector for these populations, as it preferentially transports large numbers of adult L. littorea, matching the demographic structure of the introduced California L. littorea populations. Our results highlight continued operation of live seafood trade vectors and the influence of vectors on the demographic and genetic structure of the resulting populations, especially early stages of the invasion process.     

Scorpionid Resting Trace from The Lower Permian of Southern New Mexico,USA

We describe an arthropod body impression associated with arthropod trackways of the ichnogenus Stiaria from the Lower Permian (upper Wolfcampian) Robledo Mountains Formation (Hueco Group) in the Prehistoric Trackways National Monument of southern New Mexico. The probable producer of these traces was a scorpion, and we name the likely scorpionid resting trace Alacranichnus braddyi, new ichnogenus and ichnospecies. There are no prior reports of scorpionid body impressions from terrestrial settings in the fossil record.     

Age and growth of the Giant Kelpfish,Heterostichus rostratus Girard 1854, in Southern California,USA

In order to update existing life history parameters, age and growth patterns were determined for Giant Kelpfish, Heterostichus rostratus sampled from nearshore kelp forest and estuary habitats in southern California (USA) from April 2012 through June 2015. Fish were collected by pole spear, beach seine, beam trawl, purse seine, and square enclosure. Using age‐at‐length data derived from otolith readings, Giant Kelpfish were found to have a relatively short life span with the largest examined fish reaching a maximum total length of 413 mm at an age of 5 years. Von Bertalanffy growth parameters estimated for this species were: L_∞ = 45.1 cm, k = 0.25, t₀ = ?0.66. Standard length (SL, cm)‐total length (TL, cm) and total length (TL, cm)‐weight (W, g) relationships were described by the equations: SL = 0.90 TL – 1 and W = 2.21 × 10^?3 TL^3.39, respectively. Wild juvenile Giant Kelpfish collected for this study had a higher growth rate than laboratory‐reared fish from a previous study.     

Molecular dynamics investigations of hammerhead ribozyme RNA

The hammerhead ribozyme, a small catalytic RNA molecule, cleaves, in the presence of magnesium ions, a specific phosphodiester bond within its own backbone, leading to 23-cyclic phosphate and 5-OH extremities. In order to study the dynamical flexibility of the hammerhead RNA, we performed molecular dynamics simulations of the solvated crystal structure of an active hammerhead ribozyme, obtained after flash-freezing crystals soaked with magnesium. Because of a careful equilibration protocol and the use of the Ewald summation in calculating the electrostatic interactions, the RNA structure remained close to the crystal structure, as attested by a root-mean-square deviation below 2.5 A after 750 ps of simulation. All Watson-Crick base pairs were intact at the end of the simulations. The tertiary interactions, such as the sheared G.A pairs and the U-turn, important for the stabilisation of the three-dimensional RNA fold, were also retained. The results demonstrate that molecular dynamics simulations can be successfully used to investigate the dynamical behaviour of a ribozyme, thus, opening a road to study the role of transient structural changes involved in ribozyme catalysis.