Inhibited Al diffusion and growth roughening on Ga-coated Al (100)

Ab initio calculations indicate that the ground state for Ga adsorption on Al (100) is on-surface with local unit coverage. On Ga-coated Al (100), the bridge diffusion barrier for Al is large, but the Al$\rightarrow$Ga {\it exchange barrier is zero}: the ensuing incorporation of randomly deposited Al's into the Ga overlayer realizes a percolation network, efficiently recoated by Ga atoms. Based on calculated energetics, we predict rough surface growth at all temperatures; modeling the growth by a random deposition model with partial relaxation, we find a power-law divergent roughness $w\sim t^{\,0.07\pm0.02}$.Comment: 4 pages RevTeX-twocolumn, no figures. to appear in Phys. Rev. Lett., July 199

Current and future effectiveness of the Natura 2000 network for protecting plant species in Sardinia: a nice and complex strategy in its raw state?

Sardinia hosts 186 endemic plant species and represents an important centre for Mediterranean biodiversity. In view of the threats facing its flora, 27 terrestrial vascular plants have been listed in international regulations and 124 sites designated for species and habitat conservation. This study analyses gaps in the Natura 2000 network and the current and future distribution of four representative plants. Each plant population was georeferenced and the effectiveness of the Natura 2000 network was compared according to conservation status and distribution. Future species distributions were modelled by considering current climatic conditions and future scenarios. In apparent discordance with other results, we found that the Natura 2000 network represents most plant species well. This research shows a forward-looking survey on the regional effectiveness of protection measures which led us to confirm the need to enhance the current state of the Natura 2000 network by implementing local legislation and regulations

Does a correlation exist between environmental suitability models and plant population parameters? An experimental approach to measure the influence of disturbances and environmental changes

Due to increasing human pressures, there is a need to understand how environmental and anthropogenic disturbances could affect the conservation status of endangered plant species. When information on distribution or population parameters is poor, Species Distribution Models (SDMs) may offer a valuable additional source to assess threats and to evaluate conservation options. In this sense, if the output of SDMs represents the relationships between habitat features and species occurrence, SDM results can also be related to other key parameters of population. For the endangered yellow gentian, we tested the relationship between six field population parameters and the suitabilities obtained by SDMs with natural and limiting parameters (i.e. proxies of disturbances). Specifically, the six population parameters were the surface area covered by each population, the number of vegetative and reproductive individuals per population, the density of reproductive and all individuals per plot and the proportion of reproductive individuals. Thus, threats were evaluated by testing if relationships between population parameters and suitabilities increased when proxies of disturbances were included in models. Best-fitting models resulted when all natural and human disturbance variables were included. In addition, results show relationships between suitability and population parameters only when disturbance parameters were used for SDMs. When the index related to the sensitivity to climate change was included in SDMs, the density of all individuals and number of reproductive plants were lower than in low suitability sites, suggesting that climate change is likely already challenging the ability of yellow gentian to bloom and germinate. Otherwise, we observed a decrease of the extent of localities in areas with higher suitability obtained through the index related to trail intensity. This confirmed the positive effect of conservation activities, which were mainly implemented in the proximity of trails. Using a thoroughly studied plant species as a straightforward example, we showed the potentiality of SDMs to inform on population parameters instead of only discriminate species presence or absence. This information can suggest the use of disturbance parameters when specific SDMs aim to support strategic decisions in management and conservation

The reliability of conservation status assessments at regional level: Past, present and future perspectives on Gentiana lutea L. ssp. lutea in Sardinia

Regional assessments could be more reliable than global ones, especially for species in peripheral parts of their range. In this sense, distribution criteria proposed by the IUCN, expressed by the Extent of Occurrence (EOO) and the Area of Occupancy (AOO), are of critical importance to evaluate the risk category at any scale. Our study was focused on the yellow gentian (Gentiana lutea L. subsp. lutea), a rhizomatous mountain plant of central and southern Europe, included in the Annex V of the Directive 92/43/EEC. The exhaustive and updated regional distribution and the recently published extinct localities, allowed for review of option to increase the number of criteria used for its regional conservation status assessment. In particular, the current restricted EOO and AOO extents and reductions occurred during the last three generations led this plant being considered as Endangered (EN), according to the IUCN sub-criteria A2, B1 and B2. Additionally, Species Distribution Models based on the extant localities and the respective current and future climate scenarios (2050 and 2070) predicted a decrease of its environmental niche reducing its altitudinal range towards higher elevations. This reduction was greater than 50% and confirmed the regional conservation status of EN, also according to the sub-criterion A3.This paper shows the reliability of regional risk assessment of peripheral and/or narrow populations, which is an effective tool for helping the development of the necessary conservation management, underling a diversified set of solutions for each specific past, present and future threat that could occur in each locality

The impact of climatic variations on the reproductive success of Gentiana lutea L. in a Mediterranean mountain area

Increases in temperature have been predicted and reported for the Mediterranean mountain ranges due to global warming and this phenomenon is expected to have profound consequences on biodiversity and ecosystem functioning. We hereby present the case of Gentiana lutea L. subsp. lutea, a rhizomatous long-lived plant living in Central-Southern Europe, which is at the edge of its ecological and distributional range in Sardinia. Concretely, we analysed the reproductive success experienced during three phenological cycles (2013/2014, 2014/2015 and 2015/2016) in four representative populations, with particular attention to the phenological cycle of 2014/2015, which has been recorded as one of the warmest periods of the last decades. The Smirnov-Grubbs test was used to evaluate differences in temperature and precipitation regimes among historical data and the analysed years, while the Kruskal-Wallis followed by the Wilcoxon test was used to measure differences between anthesis and reproductive performances among cycles and populations. In addition, generalised linear models were carried out to check relationships between climate variables and reproductive performance. Significant differences among climate variables and analysed cycles were highlighted, especially for maximum and mean temperatures. Such variations determined a non-flowering stage in two of the four analysed populations in 2014/2015 and significant differences of further five reproductive traits among cycles. These results confirmed that in current unstable climatic conditions, which are particularly evident in seasonal climates, reproductive success can be a sensitive and easily observable indicator of climatic anomalies. Considering the importance of this issue and the ease and cost-effectiveness of reproductive success monitoring, we argue that research in this sense can be a supporting tool for the enhancement of future crucial targets such as biodiversity conservation and the mitigation of global warming effects

Effect of L-cysteine on acetaldehyde self-administration

Acetaldehyde (ACD), the first metabolite of ethanol, has been implicated in several behavioural actions of alcohol, including its reinforcing effects. Recently, we reported that L-cysteine, a sequestrating agent of ACD, reduced oral ethanol self-administration and that ACD was orally self-administered. This study examined the effects of L-cysteine pre-treatment during the acquisition and maintenance phases of ACD (0.2%) self-administration as well as on the deprivation effect after ACD extinction and on a progressive ratio (PR) schedule of reinforcement. In a separate PR schedule of reinforcement, the effect of L-cysteine was assessed on the break-point produced by ethanol (10%). Furthermore, we tested the effect of L-cysteine on saccharin (0.2%) reinforcement. Wistar rats were trained to self-administer ACD by nose poking on a fixed ratio (FR1) schedule in 30-min daily sessions. Responses on an active nose-poke caused delivery of ACD solution, whereas responses on an inactive nose-poke had no consequences. L-cysteine reduced the acquisition (40 mg/kg), the maintenance and the deprivation effect (100 mg/kg) of ACD self-administration. Furthermore, at the same dose, L-cysteine (120 mg/kg) decreased both ACD and ethanol break point. In addition, L-cysteine was unable to suppress the different responses for saccharin, suggesting that its effect did not relate to an unspecific decrease in a general motivational state. Compared to saline, L-cysteine did not modify responses on inactive nose-pokes, suggesting an absence of a non-specific behavioural activation. Taken together, these results could support the hypotheses that ACD possesses reinforcing properties and L-cysteine reduces motivation to self-administer ACD