Lefeuvre P.,CIRAD |
Moriones E.,Institute Hortofruticultura Subtropical Y Mediterranea La Mayora IHSM UMA CSIC
Current Opinion in Virology | Year: 2015
Genetic recombination facilitates the transfer of genetic information in a parasexual reproduction manner even between distantly related species. Within the Geminiviridae family, a group of plant-infecting viruses that severely constrain cropping systems worldwide, it is highly suspected that recombination was pivotal in the emergence as a devastating phytopathological problem. Whereas extensive evidence of recombination suggests that this mechanism might be adaptive in this family, direct demonstration remains scarce. Here we assemble lines of evidences indicating that recombination was crucial in driving host switches and further emergence of geminiviruses, making these viruses such successful plant pathogens. © 2014 Elsevier B.V. All rights reserved.
Liang J.,West Virginia University |
Forest Science | Year: 2013
The Matrix model uses transition matrices to predict future plant and animal population structures. Having been used to study the dynamics of forests all over the world, the Matrix model is thriving in forestry, with applications covering a wide array of areas. Despite its extensive application in forestry, the Matrix model is still suffering from a lack of due attention and appropriate understanding, especially on its advantages and limitations in comparison with those of other forest dynamics models. To facilitate further research and applications, a synthetic review of Matrix models is provided here with an emphasis on its mathematical properties and relationship with other forest dynamics models. In this article, we first introduce the general structure of Matrix models and its representation of forest dynamics components, i.e., upgrowth, mortality, and recruitment. Then, we summarize key properties of Matrix models, including basic assumptions, density dependence, size class width and time step, and the estimation of forest dynamics components will be summarized. Next, we evaluate advantages and limitations of the Matrix model and its relationship with other forest dynamics models. Finally, we share our perspective on the major challenges and future outlooks of Matrix models. © 2013 by the Society of American Foresters.
Dumont Y.,CIRAD - Agricultural Research for Development |
Mathematical Biosciences and Engineering | Year: 2010
We previously proposed a compartmental model to explain the outbreak of Chikungunya disease in Réunion Island, a French territory in Indian Ocean, and other countries in 2005 and possible links with the explosive epidemic of 2006. In the present paper, we asked whether it would have been possible to contain or stop the epidemic of 2006 through appropriate mosquito control tools. Based on new results on the Chikungunya virus, its impact on mosquito life-span, and several experiments done by health authorities, we studied several types of control tools used in 2006 to contain the epidemic. We present an analysis of the model, and we develop a new nonstandard finite difference scheme to provide several simulations with and without mosquito control. Our preliminary study shows that an early use of a combination of massive spraying and mechanical control (like the destruction of breeding sites) can be efficient, to stop or contain the propagation of Chikungunya infection, with a low impact on the environment.
d'Aquino P.,CIRAD |
Bah A.,UMISCO ESP UCAD
Ecology and Society | Year: 2013
Over the centuries, local communities have shaped atypical rules to deal with the uncertainty of their environment. They have developed complex prototypes for flexible overlapping institutions and arrangements to adapt their rules and uses to their uncertain environment. Today, this indigenous way of flexibly institutionalizing access rules could provide blueprints for dealing with uncertainty issues resulting from global change as well as designing practical guidelines for implementing resilient management. However, transforming indigenous skills for developing institutional flexibility into operational management rules that are appropriate in the current environmental and socioeconomic context is a huge challenge. However, communities could easily succeed in this reframing because the structuring principles of institutional flexibility are embedded in their mind frame. In this perspective, a participatory modeling process was applied in Senegal to explore, first, how to design a methodological platform to enable local people to shape different forms of environmental management and policies they consider appropriate in the new context of environmental uncertainty by drawing on their own attitudes to environmental management. Second, to increase the value of such "self-designed" outputs in improving knowledge about, and improving, the practical management of uncertainty, especially in drylands. © 2013 by the author(s).
Teschke R.,Goethe University Frankfurt |
Food and Chemical Toxicology | Year: 2011
Rare cases of hepatotoxicity emerged with the use of kava drugs and dietary supplements prepared from rhizomes and roots of the South Pacific plant kava (Piper methysticum). Their psychoactive, anxiolytic, relaxing, and recreational ingredients are the kavalactones kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin, but there is little evidence that these kavalactones or the non-kavalactones pipermethystine and flavokavain B are the culprits of the adverse hepatic reactions. It rather appears that poor quality of the kava material was responsible for the liver toxicity. Analysis of existing kava quality standardizations with focus on chemical, agricultural, manufacturing, nutritional, regulatory, and legislation backgrounds showed major shortcomings that could easily explain quality problems. We therefore suggest a uniform, internationally accepted device for kava quality standardizations that are in the interest of the consumers because of safety reasons and will meet the expectations of kava farmers, pharmaceutical manufacturers, regulators of agencies, and legislators. The initial step resides in the establishment of Pan-Pacific kava quality legislation as an important part of the proposed Kava Quality Standardization Code. In conclusion, a sophisticated approach to establish kava quality standardizations is needed for safe human use of kava as relaxing traditional beverages, the anxiolytic drugs, and recreational dietary supplements. © 2011 Elsevier Ltd.
Herrmann L.,Deakin University |
Applied Microbiology and Biotechnology | Year: 2013
The interest in biofertilizers is increasing and so is the potential for their use in sustainable agriculture. However, many of the products that are currently available worldwide are often of very poor quality, resulting in the loss of confidence from farmers. The formulation of an inoculant is a crucial multistep process that should result in one or several strains of microorganisms included in a suitable carrier, providing a safe environment to protect them from the often harsh conditions during storage and ensuring survival and establishment after introduction into soils. One of the key issues in formulation development and production is the quality control of the products, at each stage of the process. This review presents the different components and the major steps involved in the formulation of good quality biofertilizers, including the techniques used to assess the quality of the products following production. The quality of currently available inoculants is also reviewed, emphasizing the need for better quality control systems worldwide. © 2013 Springer-Verlag Berlin Heidelberg.
Small-scale Forestry | Year: 2013
In Cameroon, community forests are frequently presented as a relevant option to increase the welfare of rural populations and simultaneously improve local governance and forest resources conservation. But apart from community forests, rural livelihoods also depend on forest areas, designated as 'domestic forests' in this article, where local users enjoy informal customary rights. The specific contributions of community and domestic forests to the evolution of the prevailing socio-ecological system are assessed through a diachronic study of a village which is located in southern Cameroon. The Sustainable Livelihoods Framework is used to compare the progress of this social-ecological system between January 2008 and December 2009. The overall evolution of livelihoods was found to be positive during that period. In this case study, domestic forests and community forests are based on complementary models, which are often observed in southern Cameroon. Domestic forests constitute the basis of socio-economic development, while community forests might offer opportunities for a local-level carbon sequestration payment mechanism. © 2012 Steve Harrison, John Herbohn.
Molto Q.,University of the French West Indies and Guiana |
Rossi V.,CIRAD |
Methods in Ecology and Evolution | Year: 2013
Reliable above-ground biomass (AGB) estimates are required for studies of carbon fluxes and stocks. However, there is a huge lack of knowledge concerning the precision of AGB estimates and the sources of this uncertainty. At the tree level, the tree height is predicted using the tree diameter at breast height (DBH) and a height sub-model. The wood-specific gravity (WSG) is predicted with taxonomic information and a WSG sub-model. The tree mass is predicted using the predicted height, the predicted WSG and the biomass sub-model. Our models were inferred with Bayesian methods and the uncertainty propagated with a Monte Carlo scheme. The uncertainties in the predictions of tree height, tree WSG and tree mass were neglected sequentially to quantify their contributions to the uncertainty in AGB. The study was conducted in French Guiana where long-term research on forest ecosystems provided an outstanding data collection on tree height, tree dynamics, tree mass and species WSG. We found that the uncertainty in the AGB estimates was found to derive primarily from the biomass sub-model. The models used to predict the tree heights and WSG contributed negligible uncertainty to the final estimate. Considering our results, a poor knowledge of WSG and the height-diameter relationship does not increase the uncertainty in AGB estimates. However, it could lead to bias. Therefore, models and databases should be used with care. This study provides a methodological framework that can be broadly used by foresters and plant ecologist. It provides the accurate confidence intervals associated with forest AGB estimates made from inventory data. When estimating region-scale AGB values (through spatial interpolation, spatial modelling or satellite signal treatment), the uncertainty of the forest AGB value in the reference forest plots has to be taken in account. We believe that in the light of the Reducing Emissions from Deforestation and Degradation debate, our method is a crucial step in monitoring carbon stocks and their spatio-temporal evolution. © 2012 The Authors. Methods in Ecology and Evolution © 2012 British Ecological Society.
Catena | Year: 2013
Many soil maps were drawn up after World War II with different soil classifications that have significantly evolved since. Updating such old maps with a new version or a new classification system is always complex: (i) we do not always possess all the original information; (ii) the criteria for determining references are often different, and (iii) on the most accurate scales, correlations come up against the complexity and specificities of each classification system. On Reunion, a volcanic tropical island in the Indian Ocean, we undertook a comprehensive overview of the old existing soil studies. This article describes (i) the procedure used to update the soil maps and the toposequence acquired with the old French Commission de Pédologie et de Cartographie des Sols (CPCS) classification system, without any new information, using the World Reference Base for soil resources (WRB); (ii) the construction of a new soil map drawn up with completely new information, and (iii) a comparison of these two approaches. At elevations below 350. m asl (above sea level), without any new pedological information, we updated Brown ferruginous soils, Reddish-brown ferrallitic soils, and Fersialitic soils into Haplic Nitisols (Humic, Eutric). The acquisition of new data showed that this update was incorrect because not all the diagnostic criteria of the Nitic horizons were met. The correct diagnostic horizons were a Mollic horizon when the thickness was 25. cm or more, or a Cambic horizon. Leptic Phaeozems and Leptic Cambisols were then the correct Reference Soil Group (RSG). At elevations from 350 to 900. m asl, without any new information, Brown and Reddish-brown ferrallitic soils, Andic ferrallitic soils, and Brown and Andic brown soils were updated into Haplic Nitisols (Humic, Dystric) and Andic Umbrisols (Humic). The acquisition of new data showed that this update was incorrect because Andic properties and the diagnostic criteria of the Nitic horizons were not met. Over 900. m asl, Pozols were correctly updated, as were the Andosols except from 900 to 1050. m asl where not all the Andic properties were met. Without any new information, incorrect updates were observed for both the determination of RSG and the qualifiers. Despite the field descriptions, the lack of any analytical determinations on the old soil studies was a source of updating errors for the more developed soils formerly qualified as ferrallitic. In order to update limits for Andic properties and Andosols, the systematic use of analytical determinations has to be considered for updating old soil maps, as the diagnostic criteria are more restrictive than in the past. © 2013 Elsevier B.V.
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 151.87K | Year: 2015
The climate of West Africa is subject to some of the most variable rainfall patterns observed anywhere in the world. In the past, the region has suffered several decades of severe droughts, whilst more recently major flood events have struck a number of the regions rapidly expanding cities. The consequences of these climatic extremes for the population have been particularly pronounced due to widespread and severe poverty. Global climate change, coming on top of such a variable and unpredictable regional climate, poses a major threat to the populations and economies of West Africa. Although the pathway from climate change to human suffering in West Africa is very short, there are some key bottlenecks to using climate projections to mitigate against risks to the population. Critical gaps exist in knowledge of how West African climate will change over the course of the 21st century, and the uncertainties make it almost impossible for agencies to deliver well-informed plans for the coming decades in critical areas such as food security, urban development and water. Even with the best climate information, it remains a significant challenge to integrate the scientific knowledge into planning and management structures. This collaborative project between scientists and policy makers in West Africa and Europe will, on the one hand, increase understanding of the regional climate and how it will change, and on the other, apply that knowledge to practical development questions. One of the key challenges for climate science is to understand how the changing composition of the atmosphere (notably CO2) will impact on the frequency and intensity of extreme events such as floods and droughts. In West Africa, these events are tied to the behaviour of convective rain storms; when storms are particularly intense or occur in rapid succession, devastating floods may result, whilst a week or two without storms during the wet season can trigger crop failure. Climate scientists rely on computer simulations of the global atmosphere, oceans and continents, yet these models have a very crude description of convective storms. For the first time, a new generation of regional climate models is emerging which realistically depict storms, and critically, how storms respond to factors such as land and ocean conditions, and increases in CO2. AMMA-2050 will use these new computer simulations alongside conventional climate models and historical observations, to understand why the statistics of key climate extremes are changing, and what this tells us about climate and its extremes in future decades. The outputs from the models will be used to examine impacts on key sectors in West African society, notably water and agriculture. Adaptation options will be explored, for example through the use of alternative crops, taking account of the inherent uncertainties in climate information, and the ways in which it is interpreted by decision-makers. We will focus on two questions. Firstly, in Senegal we will identify sustainable agricultural adaptation strategies and the policy frameworks to support those options. Secondly, we will examine how climate changes are likely to affect flooding in the rapidly growing city of Ouagadougou in Burkina Faso. The research and capacity building work of AMMA-2050 will help develop a new generation of African researchers and decision-makers, well-placed to respond to the requirements of West African nations. Within AMMA-2050, end-users have an important role, and their needs are embedded in project design and delivery, such that outputs will be responsive to their needs, and delivered in a format that is easily used. Enhanced resilience is an important aim of the project: it starts with improving our understanding of the climate signal over West Africa and leads through to decisions being made in specific pilot studies that showcase the importance of using improved and impact-sensitive science outputs.