Laser double optical resonance excitation-ionization of Mo with optogalvanic detection

We report on measurements of resonant three-step, two-colour ionization of atomic molybdenum, using a hollow cathode lamp (HCL) with optogalvanic detection. Wavelength scans were made for two specific transitions involved in the ionization pathways under investigation, namely 4d5(6S)5s 7S3 - 4d5(6S)5p 7P4 and 4d5(6S)5p 7P4 - 4d5(6S)6d 7D5.So-called ‘slow’ and ‘fast’ optogalvanic signals were observed for each pathway. Results confirm the HCL as a cost effective spectroscopic investigation tool. In particular its use in the optogalvanic mode of operation allows one to precisely, easily and reliably tune the wavelength of one or more lasers to resonances of interest for experiments in the general domain of atomic vapour laser isotope selection (AVLIS). The measurements are closely related to the Selective Production of Exotic Species (SPES) project at the ISOL facility and were performed in the recently established laser laboratory in Legnaro National Laboratories of INFN.

Main drivers of plant diversity patterns of rubber plantations in the Greater Mekong Sub-region

The Greater Mekong Sub-region (GMS) is one the global biodiversity hotspots. However, the diversity has been seriously threatened due to environmental degradation and deforestation, especially by expansion of rubber plantations. Yet, little is known about the impact of rubber plantations on plant diversity. In this study, we analyzed plant diversity patterns of rubber plantations in the GMS based on a ground survey of a large number of samples. We found that diversity varied across countries due to varying agricultural intensities. Laos had the highest diversity, then followed China, Myanmar, Cambodia. Thailand and Vietnam were the lowest among them. Plant species richness of Laos was about 1.5 times that of Vietnam. We uncovered latitudinal and longitudinal gradients in plant diversity across these artificial forests of rubber plantations. These gradients could be explained by the traditional ecological theories. Furthermore, null deviation of observed community to the randomly assembled communities were larger than zero indicating deterministic process were more important for structuring the community. Meanwhile, the results also showed that higher dominance of some exotic species (such as Chromolaena odorata and Mimosa pudica) were associated with a loss of plant diversity within rubber plantations. In conclusion, not only environmental factors (such as elevation and latitude), but also exotic species were the main factors affecting diversity of these artificial stands. Much more effort should be made to balance agricultural production with conservation goals in this region, particularly to minimize the diversity loss in Vietnam and Cambodia.

STUDIES ON THE STIMULATION OF CATALPA BIGNONIOIDES WALT. SEED GERMINATION

Catalpa is a tree with an attractive ornamental value and compact shape. Catalpa bignonioides Walt., is a tree with heights of up to 35 meters and a large trunk. It is an exotic species in North America areal. It grows well in a warm and humid climate, on alluvial, fertile, deep, temperate soils. It has a light temperament, withstands winter frosts well, but is sensitive to late frosts. The degree of germination varies both between species and within them. Within batches of seeds of the same species varies depending on the origin, year of harvest and individual trees. There are different methods and techniques for overcoming drowsiness depending on the seeds. Various pre-treatments are used such as scarification and hot and cold aeration to stimulate the embryo. The paper presents the stimulation of seed germination at catalpa, using different concentrations of Nitragin: 0.1%, 0.3%, 0.5%, 0.7%, 0.9% and following the seed germination interval.

Myrmecological diversity (Hymenoptera: Formicidae) in Tamaulipas, México

This investigation involved analyzing 77 publications, 6 national biological collections and an international collection and determining the myrmecological diversity of Tamaulipas, which consists of 195 species that belong to 60 genera, with 410 records in the state. The genera with the highest species richness were Camponotus Mayr (Formicinae), Pheidole Westwood (Myrmicinae) and Neivamyrmex Borgmeier (Dorylinae), with 17, 15 and 12 species, respectively. The ant fauna of Tamaulipas consists of 95% native species and 5% exotic species. The investigation determined that 25 municipalities had been sampled, and Gómez Farías, Victoria and Jaumave stood out with the highest number of ant species records; however, 18 municipalities that provide opportunities to increase the knowledge of Formicidae remain unexplored.

Marsilea mutica (Marsileaceae) newly reported in Texas, U.S.A.

This paper documents the first occurrence in Texas of a wild population of Marsilea mutica Mett., (Marsileaceae), an exotic species of water-clover fern. The colony's life history and potential for invasive behavior are discussed.

Soil Microbes Alter the Diversity-Invasibility Relationship by Promoting a Complementarity Effect on Community Invasion Resistance

Background Soil microbes can affect both the invasiveness of exotic plants and the invasibility of native plant communities, but it still remains unclear whether soil microbes can influence the relationship between native plant diversity and community invasibility.Methods We constructed native plant communities with three levels of species richness (one, three, or six species) in unsterilized or sterilized soil (i.e., with or without soil microbes) and either prevented their invasion by exotic plants or allowed them to be invaded by each of three exotic species (Solidago canadensis, Erigeron canadensis or Symphyotrichum subulatum), which are highly invasive in China. The soils conditioned by the native plant communities that were not invaded by the exotic species were used as soil microbe inocula to test whether species richness-induced differences in soil microbes affected the growth of each of the three invasive species.Results Compared with soils containing microbes, the absence of soil microbes weakened the negative species richness-invasibility relationship, indicating that soil microbes can contribute to higher invasion resistance in more diverse native plant communities. In the presence of soil microbes, the higher invasion resistance of more diverse communities was mainly ascribed to the complementarity effect. However, soil microbes from communities with a higher species richness did not have a stronger negative effect on the growth of any of the three invasive species. Conclusion Soil microbes can alter the diversity-invasibility relationship by promoting the complementarity effect on community invasion resistance. Our results highlight the importance of integrating the role of soil microbes when testing the diversity-invasibility hypothesis.

Invasion and Dispersion of the Exotic Species Procambarus clarkii (Decapoda Cambaridae) in Yeongsan River Basin, South Korea

The introduction of exotic species negatively affects the distribution and interactions within local biological communities in an ecosystem and can threaten ecosystem health. This study aimed to provide the basic data required to manage P. clarkii in the Yeongsan River basin. We identified the dispersion pattern and evaluated the ecosystem risk of this newly introduced species. The distribution survey investigated Procambarus clarkii populations at 25 sites in the Yeongsan River basin over a four-year period. The initial introduction occurred in Jiseok Stream. The larvae of P. clarkii were most abundant in areas with a dense aquatic plant cover, whereas adults preferred silt/clay areas. The alterations in the water flow by the river refurbishment project (carried out in 2012) increased their preferred habitats and contributed to P. clarkii dispersion. However, stable isotope analysis showed that the dispersion has had little effect on the freshwater ecosystem. The interrelationship between P. clarkii (i.e., larvae and adults) and other biological communities has been limited. Although the rapid dispersion by P. clarkii in the Yeongsan River basin has not impacted the freshwater ecosystem, further ecological information is required on how to manage P. clarkii beyond this early stage of invasion.

Psenulus carinifrons (Cameron, 1902), une nouvelle espèce exotique pour la faune de France (Hymenoptera, Psenidae)

Psenulus carinifrons (Cameron, 1902), a new exotic species for the fauna of France (Hymenoptera, Psenidae). Psenulus carinifrons iwatai (Gussakovskij, 1934), native from Japan, was detected in a reed bed in Camargue, in south-eastern France.