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A new machine-learning model to partition soil organic carbon into its centennially stable and active fractions based on Rock-Eval(r) thermal analysis
No full textInternational audienceThe quantification of soil organic carbon (SOC) biogeochemical stability is important for assessing soil health and its capacity to store carbon. Models simulating SOC stock evolution divide SOC into different kinetic pools with contrasting residence times. The initialization of compartment sizes is a major source of uncertainty for SOC simulations. In a previous study, Cécillon et al. (2021) developed a machine-learning model (PARTYsoc v2) that uses Rock-Eval(r) thermal analysis results as input variables to quantify the proportion of centennially stable and active SOC fractions using samples from long term bare fallow sites. The outputs of PARTYsoc v2 have been shown to be particularly effective for initializing the AMG model, enabling very accurate simulations of SOC stock evolutions for a dozen French sites (Kanari et al., 2022). The objective of the present work is to build a new version of PARTYsoc, validated on a larger sample set, and extend the usefulness of the AMG model initialized with PARTYsoc to different parts of the world. To do so, we have first identified sites with known crop yields and SOC stock evolutions and archived samples available for Rock-Eval(r) characterization. We then determined, for each site, the stable SOC stock value leading to the best simulation accuracy of SOC stock evolution with the AMG model. This optimal stable SOC stock allowed us to quantify the stable SOC proportion for all samples from the selected sites. Finally, we developed PARTYsoc v3 using Rock-Eval(r) measurements as input variables to predict stable SOC proportions sensu AMG model. PARTYsoc v3 is significantly different from PARTYsoc v2. In the v3, the target variable, i.e., the centennially stable SOC proportion, is determined to be optimal for the AMG model whereas in the v2 it was calculated from SOC declines at bare fallow sites. Moreover, the current v3 model uses Support Vector Machine (SVM) regression coupled with a Beta Regression instead of Random Forest. This combination of machine-learning models allows for a non-linear relationship between the target and the features, and predictions are always bounded in the [0, 1] interval. The data set has also been extended to use a larger number of sites (6 sites in the v2, and 12 sites in the v3), including both bare fallows and other types of long-term experiments. The features (Rock-Eval(r) features) are selected by first removing highly-correlated features (Spearman correlation > 0.9) and then ranking them based on their predictive importance when randomly permuted. This procedure allows us to decrease the effects of overfitting the training data. The final model uses 7 Rock-Eval(r) features (18 for the v2). We obtain satisfactory performance in both internal validation (R2=0.82, RMSE=0.07), as well as Leave-One-Site-Out (LOSO) validation (R2=0.76, RMSE=0.09). The proposed model builds upon and significantly improves the work laid out by PARTYsoc v2. Currently, we are working on further extending the data set as well as stabilizing the processes of feature selection and model parameters
To what extent can a phase-out of pesticides in viticulture be achieved? Learning from the efforts of a large farm network after 10 years
No full textInternational audienceIn accordance with European Directive 2009/128/CE, France has set up national policies to curb the reliance of agriculture on phytosanitary inputs. The DEPHY network is one such initiative;, which has been designed to drive, support and document the fieldwork of 3,000 farms voluntarily taking part in a collective input reduction programme. This study aimed to describe the achievements of the network’s viticultural sector, as its perennial crop is heavily reliant on pesticide applications. We chose a sample of 343 wine-growing systems across mainland France, analysed records of their vineyard operations from before they joined the network, and compared them to those from the 2017-2020 period. We used the Treatment Frequency Index (TFI) to assess pesticide reliance together with other techno-economical parameters: production costs, workloads, greenhouse gas emissions and disease control. A significant decrease in pesticide use was found over the whole study period, with, for instance, an average TFI reduction of 24 %, which is consistent with national objectives but unmatched outside of the network. We observed an overall shift towards pesticide inputs with lower repercussions on health or the environment, as well as different TFI reduction trajectories based on initial pesticide dependency. We described the alternative practices introduced to the systems, and our results suggest that reductions in pesticide use stem from quite small and minor changes made to the cropping systems. These new practices only slightly lowered the vineyards’ technical and economical performances in specific situations involving an indepth revamping of the systems; e.g., conversion to organic viticulture. To increase pesticide phase-out, further research is needed on redesigning cropping systems, and on how to scale up the network’s results to the national level
Cocoa Under Heat and Drought Stress
No full textInternational audienceCocoa ( Theobroma cacao L.) is an important cash crop in many tropical countries, particularly in West Africa. Heat and drought are both known to affect the physiology of cocoa plants through reduced rates of photosynthesis and transpiration, as well as changed physiological processes such as the functions of photosystems, chlorophyll synthesis, stomatal conductance and expression of heat-shock proteins. This in turn leads to decreased yields and increased risks of mortality under severe heat and drought. To help cocoa plants adapt to climate change, the literature suggests agroforestry as a potential farm management practice. It has been argued that the lack of tree cover in cocoa cultivation systems exposes the crop to heat and direct solar radiation, thus increasing evapotranspiration and the risk of drought. Drawing on data generated from two on-field studies, this chapter assesses the shade effect on cocoa’s physiological responses to drought and heat stress to determine whether shade would be beneficial under climate change scenarios. We conclude that shade improves the physiology of cocoa, but that this may not be sufficient to compensate for the negative effects of high temperatures and severe drought exacerbated by climate change in sub-optimal conditions
Can Agroforestry Provide a Future for Cocoa? Implications for Policy and Practice
No full textInternational audienceClimate change is threatening cocoa production in Ghana, the world’s second largest cocoa exporter. Yet, as we have shown in this book, the impacts of climate change must be understood in the context of the multiple socioeconomic and biophysical pressures facing cocoa farmers, including the conversion of farms for other land uses, increasing hired labor costs as well as pests and diseases. This final chapter summarizes the book’s overall findings on cocoa agroforestry as climate change adaption and points to ways forward in terms of policy, practice and research. Our findings suggest that a nuanced view of farmers, agroecosystems and sites is necessary and emphasize the need to study shade tree species and species diversity, in addition to shade levels, to optimize the sustainability of cocoa farming. We further suggest that it may not be possible to sustainably grow cocoa in marginal regions of the cocoa belt, where yields are lower and where agroforestry may be unable to mitigate the negative impacts of the adverse climate. Finally, we point to the importance of considering rights and access to trees, land, extension services and resources, and call for more multidisciplinary research on differently situated farmers’ opportunities and needs
Le rôle des communautés dans la gestion intégrée des ressources en eau
No full textInternational audienceSince its first applications in river valleys in the 1930s, integrated water resources management (IWRM) has become a widely applicable holistic approach for water governance, resting on the key balance of economic, environmental and social aspects. This chapter discusses the history and key components of IWRM. Stakeholder engagement, one such key component, is an ambitious endeavour that requires special consideration to ensure that engagement is equitable and adapted to local contexts. Accordingly, participatory coupled human-water systems modelling and game-based approaches can engage stakeholders’ knowledge to create shared representations of reality. Citizen science and distributed databases also offer opportunities for more direct and sovereign involvement of communities in the IWRM process. Overall, this chapter explores the potential of IWRM to expand collaborative governance in water management strategies, providing an overview of innovative and emerging ideas and tools in this space to be used as a starting point for those interested in exploring different ways of engaging and empowering local communities through resource management
Les usages du numérique servent-ils toujours la durabilité des exploitations ? Le cas de maraîchers en France
No full textNational audienceDigital technology is often considered a lever to enhance farms’ sustainability. However, its effects are controversial. We investigated these associations through an original survey conducted with 157 market gardeners. Digital technology is examined through the diversity of its uses. The authors employ a matching method to analyze the relationship between four digital technology uses and six sustainability goals. They show that while some uses are positively associated with sustainability goals, others are negatively associated or show no significant association. Digital technology appears more suitable for achieving narrow sustainability objectives (farmer well-being and financial health) than broad ones (organic farming and biodiversity preservation).Le numérique est souvent considéré comme un levier pour renforcer la durabilité des exploitations agricoles. Pourtant, ses effets sont controversés. L’article les analyse grâce à une enquête originale menée auprès de 157 maraîchers. Le numérique est considéré à travers la diversité de ses usages. Les auteures mobilisent une méthode d’appariement pour analyser la relation entre quatre usages du numérique et six objectifs de durabilité. Elles démontrent que si certains usages sont positivement associés aux objectifs de durabilité, d’autres sont associés négativement ou n’ont aucun effet. La technologie numérique semble plus indiquée pour atteindre des objectifs de durabilité restreinte (bien-être de l’agriculteur et santé financière) que des objectifs plus larges (agriculture biologique et préservation de la biodiversité)
Antillean contaminated soils amendment with microwave prepared sargassum biochar: A promising solution to reduce chlordecone transfer to laying hens and piglets?
No full textInternational audienceThe use of Sargassum spp., a brown invasive algae, for the production of biochars (BCs) or activated carbons (ACs) and their efficiency to sequestrate chlordecone (CLD) in soil has been recently suggested. The objective of this study was to assess the potential of microwave prepared Sargasso biochar (BCS) amendment in Andosol on the bioavailability of chlordecone in laying hens and piglets, when exposed to this matrix. The efficiency of BCS was compared to a commercial activated carbon, DARCO® (ACD), used as a positive control and to an unamended soil. Samples of CLD-contaminated Andosol were amended with 2% of each carbonaceous matrix and let maturing for 3 months. Thereafter, adequate doses of soil were administered into the laying hens and piglets diets every day during the exposure phase, to simulate involuntary soil ingestion which may happen in practical conditions when animals are reared outside. Finally, bioavailability tests were carried out on target tissue (liver, muscle, adipose tissues and egg yolk). The results showed that the highest reduction of CLD bioavailability was obtained with ACD in both animal species. For laying hens, ACD showed reductions of around 60% (liver: 59%, muscle: 57% and egg yolk: 56%) whereas the BCS showed reduction of around 30% (liver: 31%, muscle: 26% and egg yolk: 30%) compared to the unamended soil. For piglets, only the liver showed interpretable results with reduction of 65% with ACD and 41% with BCS. Overall, BCS is efficient reducing CLD availability but in a lower extend than ACD. This discrepancy may be explained by the variations of physico-chemical characteristics that exist between the two matrices, resulting, from the additional activation phase for DARCO®. Therefore, to improve the efficiency of BCS it would be interesting to move towards DARCO® characteristics by determining out the optimal microwave pyrolysis parameters
An Anthropocene-Framed Transdisciplinary Dialog at the Chemistry-Energy Nexus
No full textInternational audienceAt the energy-chemistry nexus, key molecules include carbon dioxide (CO2), hydrogen (H2), methane (CH4), and ammonia (NH3). The position of these four molecules and that of the more general family of synthetic macromolecular polymer blends (found in plastics) were cross-analyzed with the planetary boundary framework, and as part of five scientific policy roadmaps for the energy transition. According to the scenarios considered, the use of some of these molecular substances will be drastically modified in the coming years. Ammonia, which is currently almost exclusively synthesized as feedstock for the fertilizer industry, is envisioned as a future carbon-free energy vector. "Green hydrogen" is central to many projected decarbonized chemical processes. Carbon dioxide is forecast to shift from an unavoidable byproduct to a valuable feedstock for the production of carbon-based compounds. In this context, we believe that interdisciplinary elements from history, economics and anthropology are relevant to any attempted cross-analysis. Distinctive and crucial insights drawn from elements of humanities and social sciences have led us to formulate or re-raise open questions and possible blind-spots in main roadmaps, which were developed to guide, inter alia, chemical research toward the energy transition. We consider that these open questions are not sufficiently addressed in the academic arena around chemical research. Nevertheless, they are relevant to our understanding of the current planetary crisis, and to our capacity to properly assess the potential and limitations of chemical research addressing it. This academic perspective was written to share this understanding with the broader academic community. This work is intended not only as a call for a larger interdisciplinary method, to develop a sounder scientific approach to broader scenarios, but also – and perhaps mostly – as a call for the development of radically transdisciplinary routes of research. As scientists with different backgrounds, specialized in different disciplines and actively involved in contributing to shape solutions by means of our research, we bear ethical responsibility for the consequences of our acts, which often lead to consequences well beyond our discipline. Do our research and the knowledge it produces respond, perpetuate or even aggravate the problems encountered by society
Motifs d’intégration morphologique entre les sinus paratympaniques et le crâne chez lescrocodiliens actuels
No full textInternational audienceLes sinus paratympaniques des crocodiliens sont des structures pneumatiques contenues dans la boˆıte crˆanienne et reli ́ees a` l’oreille moyenne et au pharynx. Leur diversit ́e de forme remar- quable chez les esp`eces actuelles comme fossiles a men ́e de nombreux auteurs a` proposer leur utilisation en phylog ́enie, ou en tant que proxy pour inf ́erer des variables ́ecologiques. Cepen-dant, les processus d ́eveloppementaux a` l’origine de ces structures sont tr`es peu connus, et leur(s) fonction(s) exacte(s) reste(nt) à ce jour un mystère. De plus, en tant qu’organes internes contraints par les os de l’arrière-crâne, leur morphologie est potentiellement corrélée avec la morphologie externe du crâne. Pour comprendre l’ ́evolution de ces structures et de leurs relations au cours du développement et entre les espèces de crocodiles, nous présentons l’ ́etude en morphométrie géométrique de 107 spécimens représentant les 9 genres actuels de crocodiliens, depuis l’éclosion jusqu’à l’âge adulte. Les spécimens ont été scannés en tomographie à rayons X, puis segmentés pour reconstruire le crâne et les sinus en 3D, afin de quantifier leur forme grâce à des points homologues. La forme des sinus se révèle être d ́ependante de la taille et est contrainte par la forme du crâne durant son développement, montrant des trajectoires développementales différentes selon les familles, les genres, voire certains groupes d’espèces. Des variations de volume et d’extension des sinus sont observées entre les espèces brévirostres et longirostres, impliquant un lien entre la forme des sinus et la conformation crânienne, peut-être lié à des contraintes fonctionnelles dues à l’environnement aquatique. Finalement, des analyses de covariation ont été menées à l’échelle intra- et interspécifique pour évaluer précisément les motifs d’int ́egration entre les structures crˆaniennes et pneumatiques li ́es au développement ou liés à l’écologie des espèces
Morphological convergences of the masticatory apparatus associated with fossorial life in rodents
No full textInternational audienceMany mammals, especially rodents, show behavioural, morphological and physiological adap- tations to fossorial life, mainly to gain access to food resources and escape predators and extreme climatic fluctuations. Adaptations to fossorial life are found in more than ten families of ex- tant and extinct rodents on most continents. The constraints imposed by burrowing and living underground have led to strong behavioural and morphological convergences, notably involving the functioning of the rodent masticatory apparatus. While most mammals use their claws for digging, rodents are unique in that some species use their ever-growing incisors for this purpose, and most subterranean species have become chisel-tooth diggers. Here, we review examples of convergence found in the main morphological and functional components of the rodent digging apparatus in relation to burrowing activity. Several morphological specializations of the skull have been described according to 3D geometric morphometrics. Specializations of the incisor shape and of the main jaw adductor muscles are also highlighted. Our focus on families showing extreme specializations, such as Bathyergidae (African mole-rats) and Spalacidae (blind mole- rat, root-rats, Asian zokors and bamboo rats) underscores the fact that multiple modifications of the different components of the masticatory apparatus have led to similar overall morphologies and functions, overcoming phylogenetic inheritance. Interestingly, the morphological disparity recorded in each family is consistent with the putative number of independent occurrences of fossorial lifestyle during their evolutionary history, which is likely to be confirmed by further analyses of their masticatory muscles