Academic literature on the topic 'Plantes – Migration assistée'

The convergent migration of two planets in a gaseous disc can lead to mean motion resonance (MMR) capture. In addition, pairs of planets in or near MMRs are known to produce strong transit timing variations (TTVs). In this paper, we study the impact of disc-induced migrations on the TTV signal of pairs of planets that enter a resonant configuration. We show that disc-induced migration creates a correlation between the amplitude and the period of the TTVs. We study the case of K2-24, a system of two planets whose period ratio indicates that they are in or near the 2:1 MMR, with non-zero eccentricities and large-amplitude TTVs. We show that a simple disc-induced migration cannot reproduce the observed TTVs. Moreover, we propose a formation scenario in which the capture in resonance during migration in a disc with strong eccentricity damping is followed by eccentricity excitation during the dispersal of the disc. This is assisted by a third planet whose presence has been suggested by radial velocity observations. This scenario accounts for the eccentricities of the two planets and their period ratio, and it accurately reproduces the amplitude and period of the TTVs. It allows for a unified view of the formation and evolution history of K2-24, from disc-induced migration to its currently observed properties.

Lupinus elegans is a species used in ecological restoration and agroforestry programs, because it is tolerant to stress and fixes nitrogen. Genetic variation in quantitative traits was studied in six populations of L. elegans collected along an altitudinal gradient (2312 to 2885 m) in the Mil Cumbres region, east-central Michoacán state, México. Provenance tests were planted at 2600 and 2800 m altitude in two common garden field trials. Tests aimed to evaluate the performance at a different altitude than the site of the seed source, simulating an altitudinal-assisted migration. Survival, plant height growth and aerial biomass were measured. For each provenance and experimental sites, climatic variables were estimated for contemporary climate (average 1961-1990) and future climate (decade centered in 2030, by averaging six model scenarios). It was estimated that by the year 2030 there will be, on average, an increment of 1.4 °C in mean annual temperature, an increase of 518 degree-days > 5 °C (DD5), a 90 mm decrease in mean annual precipitation (MAP) (-7.3 % of contemporary MAP), and a 0.0077 increase in an aridity index (DD50.5/MAP). An ANOVA for each site revealed that in the higher altitude site (2800 m) populations exhibited a pronounced pattern of genetic differentiation (P = 0.0001), in which plant height and biomass are associated with the transfer distance between their place of origin and the experimental site. This distance can be expressed in difference in altitude, mean annual temperature, or aridity index. At the site at higher altitude, plants originated from populations growing at higher altitudes were taller and had more biomass than those originated grown at lower altitudes (R2 ≥ 0.85, P ≤ 0.0302). In contrast, in the lower altitude site (2600 m), although there were nearly significant differences (P ≤ 0.0615) between populations for all of the variables, there was no clinal pattern. In general, the populations grew less when they were moved away from their original climate: those from the higher altitudes grew less in the 2600 m site, and those from the lower altitudes grew less in the 2800 m site. This indicates that climate change will likely induce less growth in several populations, thus it is recommended to promote gradual assisted migration.

Assisted migration of forest tree populations through reforestation and restoration is a climate change adaptation strategy under consideration in many jurisdictions. Matching climates in which seed sources evolved with near future climates projected for plantation sites should help reduce maladaptation and increase plantation health and productivity. For threatened tree species, assisted migration outside of the species range could help avert extinction. Here, we examine lessons, limitations, and challenges of assisted migration through the lens of three assisted migration field trials of conifers in Canada and Mexico: Pinus albicaulis Engelm., an endangered subalpine tree species in the mountains of western North America; the Picea glauca (Moench) Voss × P. engelmannii Parry ex Engelm hybrid complex, of great economic and ecological importance in western Canada, and Abies religiosa (Kunth) Schltdl. & Cham., a tree species that provides overwintering sites for the monarch butterfly. We conclude that: (a) negative impacts of climate change on productivity of Picea glauca × P. engelmannii may be mitigated by planting seed sources from locations that are 3 °C mean coldest month temperature warmer than the plantation; (b) it is possible to establish Pinus albicaulis outside of its current natural distribution at sites that have climates that are within the species’ modelled historic climatic niche, although developing disease-resistant trees through selective breeding is a higher priority in the short term; (c) Abies religiosa performs well when moved 400 m upward in elevation and local shrubs (such as Baccharis conferta Kunth) are used as nurse plants; (d) new assisted migration field trials that contain populations from a wide range of climates tested in multiple disparate climates are needed, despite the costs; and (e) where naturalization of a migrated tree species in recipient ecosystem is viewed as undesirable, the invasive potential of the tree species should be assessed prior to large scale establishment, and stands should be monitored regularly following establishment.

At least 30% of main sequence stars host planets with sizes of between 1 and 4 Earth radii and orbital periods of less than 100 days. We use N-body simulations including a model for gas-assisted pebble accretion and disk–planet tidal interaction to study the formation of super-Earth systems. We show that the integrated pebble mass reservoir creates a bifurcation between hot super-Earths or hot-Neptunes (≲15 M⊕) and super-massive planetary cores potentially able to become gas giant planets (≳15 M⊕). Simulations with moderate pebble fluxes grow multiple super-Earth-mass planets that migrate inwards and pile up at the inner edge of the disk forming long resonant chains. We follow the long-term dynamical evolution of these systems and use the period ratio distribution of observed planet-pairs to constrain our model. Up to ~95% of resonant chains become dynamically unstable after the gas disk dispersal, leading to a phase of late collisions that breaks the original resonant configurations. Our simulations naturally match observations when they produce a dominant fraction (≳95%) of unstable systems with a sprinkling (≲5%) of stable resonant chains (the Trappist-1 system represents one such example). Our results demonstrate that super-Earth systems are inherently multiple (N ≥ 2) and that the observed excess of single-planet transits is a consequence of the mutual inclinations excited by the planet–planet instability. In simulations in which planetary seeds are initially distributed in the inner and outer disk, close-in super-Earths are systematically ice rich. This contrasts with the interpretation that most super-Earths are rocky based on bulk-density measurements of super-Earths and photo-evaporation modeling of their bimodal radius distribution. We investigate the conditions needed to form rocky super-Earths. The formation of rocky super-Earths requires special circumstances, such as far more efficient planetesimal formation well inside the snow line, or much faster planetary growth by pebble accretion in the inner disk. Intriguingly, the necessary conditions to match the bulk of hot super-Earths are at odds with the conditions needed to match the Solar System.

Abstract Woody plants have been cultured in vitro since the 1930s. After that time much progress has been made in the culture of tissues, organs, cells, and protoplasts in tree species. Tree biotechnology has been making strides in clonal propagation by organogenesis and somatic embryogenesis. These regeneration studies have paved the way for gene transfer in forest trees. Transgenics from a number of forest tree species carrying a variety of recombinant genes that code for herbicide tolerance, pest resistance, lignin modification, increased woody bio-mass, and flowering control have been produced by Agrobacterium-mediated and biolistic methods, and some of them are undergoing confined field trials. Although relatively stable transgenic clones have been produced by genetic transformation in trees using organogenesis or somatic embryogenesis, there were also unintended unstable genetic events. In order to overcome the problems of randomness of transgene integration and instability reported in Agrobacterium-mediated or biolistically transformed plants, site-specific transgene insertion strategies involving clustered regularly interspaced short palindromic repeats (CRISPR-Cas9) platform offer prospects for precise genome editing in plants. Nevertheless, it is important to monitor phenotypic and genetic stability of clonal material, not just under greenhouse conditions, but also under natural field conditions. Genetically modified poplars have been commercialized in China, and eucalypts and loblolly pine are expected to be released for commercial deployment in USA. Clonal forestry and transgenic forestry have to cope with rapid global climate changes in the future. Climate change is impacting species distributions and is a significant threat to biodiversity. Therefore, it is important to deploy Strategies that will assist the survival and evolution of forest tree species facing rapid climate change. Assisted migration (managed relocation) and biotechnological approaches offer prospects for adaptation of forest trees to climate change.

Les semences forestières génétiquement améliorées pourraient ne plus être adaptées aux sites où elles sont destinées à cause des changements climatiques. La migration assistée figure parmi les stratégies d'adaptation proposées pour maintenir la productivité forestière et diminuer la vulnérabilité des écosystèmes. Les réponses morpho-physiologiques des plants d’épinette blanche (Picea glauca (Moench) Voss) issus de huit vergers à graines ont été évaluées en pépinière et sur trois sites de plantation. La modélisation des courbes de croissance a montré que la hauteur des vergers méridionaux et de deuxième génération est significativement supérieure à celle des autres vergers. Un modèle à régression multiple a montré que la hauteur finale des plants était significativement corrélée aux conditions climatiques d’origine des vergers. Le verger et le site de plantation ont affecté significativement la croissance en hauteur des plants. Les résultats de la présente étude et ceux obtenus à long terme contribueront à raffiner les règles opérationnelles de transfert des semences propres à la migration assistée.
Due to climate change, genetically improved trees may no longer be adapted to the sites where they are intended to be planted. Assisted migration is a potential adaptation strategy for maintaining forest productivity and reducing vulnerability in the face of a changing climate. Morpho-physiological responses of white spruce (Picea glauca (Moench) Voss) seedlings from eight seed orchards were evaluated in a nursery and at three planting sites. The modeling of growth curves showed that the height of both the southern orchards and second generation orchards was significantly higher than the other orchards. A multiple regression model showed that the final height of the plants was significantly correlated with climatic conditions of the orchards. The orchard and the planting site significantly affected height growth of seedlings. The results of this study and those obtained over the longer term should help to refine the operational rules of seed transfer for assisted migration.

The material presented in the chapters of Carnivorous Plants: Physiology, Ecology, and Evolution together provide a suite of common themes that could provide a framework for increasing progress in understanding carnivorous plants. All speciose genera would benefit from more robust, intra-generic classifications in a phylogenetic framework that uses a unified species concept. As more genomic, proteomic, and transcriptomic data accrue, new insights will emerge regarding trap biochemistry and regulation; interactions with commensals; and the importance of intraspecific variability on which natural selection works. Continued elaboration of field experiments will provide new insights into basic physiology; population biology; plant-animal and plant-microbe relationships; and evolutionary dynamics, all of which will aid conservation efforts and contribute to discussions of assisted migration as the climate continues to change.

AbstractThis chapter examines the development of UK child migration to Australia in the inter-war period. Following the opening of Kingsley Fairbridge’s experimental farm school for child migrants at Pinjarra in 1913, the 1920s and 1930s saw a gradual increase in the number of voluntary societies involved in this work and of residential institutions in Australia receiving child migrants. The growth of these programmes in the wider context of the UK Government’s assisted migration policies is discussed. During the 1930s, the global financial depression weakened governmental support for assisted migration, and greater caution emerged within the UK Government about the value of some planned migration schemes. Nevertheless, by 1939, child migration to Australia was seen by UK policy-makers as a small but important part of the attempt to strengthen ties with Britain’s Dominions and to make more efficient use of their collective human and material resources.

The Annual Report on Migration and Asylum 2016 provides an overview of trends, policy developments and significant debates in the area of asylum and migration during 2016 in Ireland. Some important developments in 2016 included: The International Protection Act 2015 was commenced throughout 2016. The single application procedure under the Act came into operation from 31 December 2016. The International Protection Office (IPO) replaced the Office of the Refugee Applications Commissioner (ORAC) from 31 December 2016. The first instance appeals body, the International Protection Appeals Tribunal (IPAT), replacing the Refugee Appeals Tribunal (RAT), was established on 31 December 2016. An online appointments system for all registrations at the Registration Office in Dublin was introduced. An electronic Employment Permits Online System (EPOS) was introduced. The Irish Short Stay Visa Waiver Programme was extended for a further five years to October 2021. The Second National Action Plan to Prevent and Combat Human Trafficking was published. 2016 was the first full year of implementation of the Irish Refugee Protection Programme (IRPP). A total of 240 persons were relocated to Ireland from Greece under the relocation strand of the programme and 356 persons were resettled to Ireland. Following an Oireachtas motion, the Government agreed to allocate up to 200 places to unaccompanied minors who had been living in the former migrant camp in Calais and who expressed a wish to come to Ireland. This figure is included in the overall total under the IRPP. Ireland and Jordan were appointed as co-facilitators in February 2016 to conduct preparatory negotiations for the UN high level Summit for Refugees and Migrants. The New York Declaration, of September 2016, sets out plans to start negotiations for a global compact for safe, orderly and regular migration and a global compact for refugees to be adopted in 2018. Key figures for 2016: There were approximately 115,000 non-EEA nationals with permission to remain in Ireland in 2016 compared to 114,000 at the end of 2015. Net inward migration for non-EU nationals is estimated to be 15,700. The number of newly arriving immigrants increased year-on-year to 84,600 at April 2017 from 82,300 at end April 2016. Non-EU nationals represented 34.8 per cent of this total at end April 2017. A total of 104,572 visas, both long stay and short stay, were issued in 2016. Approximately 4,127 persons were refused entry to Ireland at the external borders. Of these, 396 were subsequently admitted to pursue a protection application. 428 persons were returned from Ireland as part of forced return measures, with 187 availing of voluntary return, of which 143 were assisted by the International Organization for Migration Assisted Voluntary Return Programme. There were 532 permissions of leave to remain granted under section 3 of the Immigration Act 1999 during 2016. A total of 2,244 applications for refugee status were received in 2016, a drop of 32 per cent from 2015 (3,276). 641 subsidiary protection cases were processed and 431 new applications for subsidiary protection were submitted. 358 applications for family reunification in respect of recognised refugees were received. A total of 95 alleged trafficking victims were identified, compared with 78 in 2015.