Modélisation de la vitesse de séchage du maïs

Cet article consiste à présenter un autre modèle appliqué à la détermination de la vitesse de séchage du produit hygroscopique. Ce modèle est obtenu par la ressemblance entre la cinétique chimique et la cinétique de séchage. L’intérêt de ce présent travail c’est de trouver un modèle simple, facile et fiable pour caractériser la vitesse de séchage du produit. En adoptant ce modèle, nous avons obtenu un autre modèle mathématique de la cinétique de séchage du maïs. Nous validons le modèle adopté par rapport à l’autre modèle, nous observons que les résultats sont en accords.Mots-clés : Modèle, vitesse séchage, cinétique de séchage, produitshygroscopiques, maïs

Validation of agent-based land use model by Markovian model : application to forest-agriculture transitions in Madagascar

The determination of transition rules that farmers adopt to manage crop-fallow after forest clearing, is essential for deciding a sustainable strategy for forest conservation. The effect of the type of farms with respect to these transition rules in forest border may mitigate incentive measures planned by forest conservation policy. Agent-base modeling (ABM) of land use is a relevant approach to manage the dynamics of heterogeneous mosaic landscapes such as the border of the Malagasy Eastern rainforest. Transition rules between six land uses (forest, fallow, crop, grass, plantation and paddy ?eld) are formalized at a plot level. A historical database containing transitions between the ?rst four land use states was used to calibrate transition models for the ecological and farmer land use dynamics. Three land-use models have been built: (1) a Markov chain (stochastic), (2) a timed automaton (deterministic), (3) and an agent-based model, which introduces the farmers. The land use ABM allows to test scenarios of deforestation with both varying initial population and farm spatial organization, size or strategy. The land use ABM is ?rst calibrated via a timed automaton, ?tting time delay parameters, the duration of each land use state (fallow, crop, grass), and the number of cropping cycles since the ?rst forest clearing. It is then validated with the help of a Markovian model, comparing two transition matrices with ?2 metrics. The two transition matrices were respectively created with historical data of plot land use, and with simulated data produced by the land use ABM. We ?nish with a general discussion on the validation of such a complex system with a simple mathematical model. (Résumé d'auteur

Global to local genetic diversity indicators of evolutionary potential in tree species within and outside forests

There is a general trend of biodiversity loss at global, regional, national and local levels. To monitor this trend, international policy processes have created a wealth of indicators over the last two decades. However, genetic diversity indicators are regrettably absent from comprehensive bio-monitoring schemes. Here, we provide a review and an assessment of the different attempts made to provide such indicators for tree genetic diversity from the global level down to the level of the management unit. So far, no generally accepted indicators have been provided as international standards, nor tested for their possible use in practice. We suggest that indicators for monitoring genetic diversity and dynamics should be based on ecological and demographic surrogates of adaptive diversity as well as genetic markers capable of identifying genetic erosion and gene flow. A comparison of past and present genecological distributions (patterns of genetic variation of key adaptive traits in the ecological space) of selected species is a realistic way of assessing the trend of intra-specific variation, and thus provides a state indicator of tree genetic diversity also able to reflect possible pressures threatening genetic diversity. Revealing benefits of genetic diversity related to ecosystem services is complex, but current trends in plantation performance offer the possibility of an indicator of benefit. Response indicators are generally much easier to define, because recognition and even quantification of, e.g., research, education, breeding, conservation, and regulation actions and programs are relatively straightforward. Only state indicators can reveal genetic patterns and processes, which are fundamental for maintaining genetic diversity. Indirect indicators of pressure, benefit, or response should therefore not be used independently of state indicators. A coherent set of indicators covering diversity–productivity–knowledge–management based on the genecological approach is proposed for application on appropriate groups of tree species in the wild and in cultivation worldwide. These indicators realistically reflect the state, trends and potentials of the world’s tree genetic resources to support sustainable growth. The state of the genetic diversity will be based on trends in population distributions and diversity patterns for selected species. The productivity of the genetic resource of trees in current use will reflect the possible potential of mobilizing the resource further. Trends in knowledge will underpin the potential capacity for development of the resource and current management of the genetic resource itself will reveal how well we are actually doing and where improvements are required

Two sides to every coin: farmers’ perceptions of mining in the Maningory watershed, Madagascar

An increasing share of Madagascar’s population is dependent on artisanal and small-scale mining (AMS) as a source of livelihood. However, this unregulated activity has numerous repercussions on the miners themselves and on neighboring communities. This study explores the perception of mining of those indirectly affected by its growing presence. Farmers and fishers were interviewed to better understand the perceived impacts of AMS on communities situated at varying distances from mining activity. The results of this first qualitative study show that positive or negative perception may be linked to geographical distance to mines. Those living in mining-communities may reap more benefits from the proximity than those living further away, who mainly experience negative effects. The results from this small sample will need to further be empirically tested. RÉSUMÉUne part croissante de la population de Madagascar tire l’essentiel de ses moyens de subsistance de l’exploitation minière artisanale et à petite échelle. Cependant, cette activité nonréglementée a de nombreuses répercussions sur les mineurs euxmêmes et sur les communautés voisines. Cette étude explore comment les riverains indirectement touchés perçoivent l’exploitation minière qu’ils rencontrent de plus en plus souvent. Des paysans et des pêcheurs de communautés basées à des distances variées des activités minières ont été interviewés afin de mieux comprendre les impacts perçus de l’exploitation minière artisanale. Les résultats de cette première étude qualitative montrent que des perceptions positives ou négatives pourraient être liées à la distance entre les lieux de vie des communautés et les mines. Les habitants vivant au sein de communautés minières pourraient tirer plus de profit de cette proximité que ceux vivant plus loin et ressentant principalement des effets négatifs. Les résultats de ce premier échantillon devront être vérifiés de manière empirique

Qualitative and Quantitative Evidence on the True Local Welfare Costs of Forest Conservation in Madagascar: Are Discrete Choice Experiments a Valid ex ante Tool?

Protected areas may impose local welfare costs through the enforcement of use restrictions. Predicting their welfare impacts before their establishment could help with the design of compensation schemes. Discrete choice experiments (DCEs) are increasingly used for ex ante evaluations but their validity is largely untested in low-income settings. Using a case study of a new REDD+ (Reducing Emissions from Deforestation and forest Degradation) project in eastern Madagascar, we explore the validity of DCEs in two ways: (i) whether the estimates of welfare costs derived from DCE are affected by respondents’ prior experience of conservation (ii) whether DCE results have high theoretical and content validity. We surveyed households who have varying degrees of experience of restrictions to swidden agriculture. We also qualitatively debriefed a sub-sample of respondents to better understand their thought processes. Latent class analysis shows that DCE outcomes vary with conservation experience. Households more experienced with forest protection are less willing to trade-off rights to clear forest for swidden agriculture with any compensatory interventions whereas less experienced households highly favor support for alternative agricultural techniques and a secure right to clear one hectare of forest. Although the results show apparent non-attendance to some attributes (e.g., cash payments), qualitative debriefings suggest that respondents infact do expect relatively low or no utility from the given attributes and hence have theoretically valid preferences. Similarly, the DCE has generally high content validity. Although DCE can elicit current preferences in this context, using ex ante DCE to estimate the welfare costs of such a long-term intervention requires caution. We conclude that it is difficult to robustly estimate compensation in advance of an intervention, there is therefore a need to rethink conservation approaches, and the feasibility of achieving fair compensations for conservation-imposed restrictions

A proposal for ethical research conduct in Madagascar

This journal provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge. The attached file is the published version of the article