9 research outputs found
Effect of carbon allocation, land use change, and ozone pollution on global crop yields of major cereals: a modelling approach
Agriculture is currently facing environmental challenges like climate change, air pollution, and land degradation, affecting agricultural productivity and threatening global food security. Besides, the increase in per capita food consumption among medium and high-income population, plus the expected increase in global population to around 9 billion by 2050, will lead to an unprecedented demand for food sustainably produced. To reach this aim, a holistic understanding of agroecosystems and their complexities is required. The Global Gridded Crop Models (GGCMs) have been developed to fullfill this requirement. Therefore, studies about the food systems require accurate crop models with explicit simulations of the productive processes and interactions with the environment.
This thesis aims to contribute to this broad effort to improve the performance of GGCMs by improving the representations of crop growth, stress response and yield with the Lund-Postdam-Jena General Ecosystem Simulator (LPJ-GUESS) model. The improvement focused on three aspects: (1) carbon assimilation and allocation processes, (2) the impact of past land cover change, and (3) the effect of ground-level O3 pollution on crop yields. The thesis evaluated how these factors affect simulated crop production and how the model can assess crop production under different environmental and management conditions at different spatial and temporal scales. Each of the three aspects also represents different types of uncertainty that the model has to address and are finally reflected in the model outputs, such as parameter uncertainty, input uncertainty and structural uncertainty.
LPJ-GUESS was improved, enhancing its capability to replicate yields, crop productivity processes, and the harmful effects on yield and harvest index simulated by the ozone module. These improvements have significant implications for developing more comprehensive and precise crop simulations that account for the complex interactions between crop production, environmental and management factors, and ozone. These advancements contribute to potentially more accurate global and large-scale yield simulations to better understand the impacts of climate change and terrestrial biogeochemical cycles on food production.
Overall, this thesis represents an improvement in the representation of productive crop processes and will increase the consistency of results in strategic research performed with LPJ-GUESS on the global food system. This is critical for researchers and policymakers to meet the current challenges of agriculture in feeding an increasing population in an environmentally and socially sustainable way
Modelling crop yield and harvest index: the role of carbon assimilation and allocation parameters
Crop yield improvement during the last decades has relied on increasing the ratio of the economic organ to the total aboveground biomass, known as the harvest index (HI). In most crop models, HI is set as a parameter; this empirical approach does not consider that HI not only depends on plant genotype, but is also affected by the environment. An alternative is to simulate allocation mechanistically, as in the LPJ-GUESS crop model, which simulates HI based on daily growing conditions and the crop development stage. Simulated HI is critical for agricultural research due to its economic importance, but it also can validate the robust representation of production processes. However, there is a challenge to constrain parameter values globally for the allocation processes. Therefore, this paper aims to evaluate the sensitivity of yield and HI of wheat and maize simulated with LPJ-GUESS to eight production allocation-related parameters and identify the most suitable parameter values for global simulations. The nitrogen demand reduction after anthesis, the minimum leaf carbon to nitrogen ratio (C:N) and the range of leaf C:N strongly affected carbon assimilation and yield, while the retranslocation of labile stem carbon to grains and the retranslocation rate of nitrogen and carbon from vegetative organs to grains after anthesis mainly influenced HI. A global database of observed HI for both crops was compiled for reference to constrain simulations before calibrating parameters for yield against reference data. Two high- and low-yielding maize cultivars emerged from the calibration, whilst spring and winter cultivars were found appropriate for wheat. The calibrated version of LPJ-GUESS improved the simulation of yield and HI at the global scale for both crops, providing a basis for future studies exploring crop production under different climate and management scenarios
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and lowâmiddle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of âsingle-useâ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for lowâmiddle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both highâ and lowâmiddleâincome countries
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Modeling dormancy in grapevines (Vitis vinifera L.)
Dormancy in plants is an evolutionary strategy to overcome the adverse climatic conditions during winter through the detention of growth and the decrease in the metabolism. This period is defined in greater depth as endodormancy when the growth is inhibited by internal signs in the buds, and ecodormancy when the adverse environmental conditions inhibit the growth. When conditions are suitable again, ecodormancy ends, growth resumes, and bud break occurs. Nevertheless, the transitions between stages during dormancy do not have visual symptoms, obstructing the decision-making process and the associated timing of management activities in the vineyard. Therefore, the goal of this study was to develop a model to predict the occurrence of the phenological stages during dormancy and bud break in grapevines âCabernet Sauvignonâ and âChardonnay.' In the first part of this study, the effect of photoperiod and temperature on endodormancy induction were evaluated. In the second part, the dates of the onset and release of endodormancy for an experimental vineyard were estimated for four years. In the final part of this study, an integrated phenological model was developed. The model assumes that the shortening of the photoperiod induces the onset of endodormancy when a critical day length (CDL) specific for each cultivar is reached. Then, a period of exposure to chilling temperatures leads the transition from endodormancy to ecodormancy, and finally, a period of warm temperatures forces bud break. The model showed that âCabernet Sauvignonâ has a longer endodormancy period caused by the cultivar-specific sensitivity to CDL, as well as a faster completion of the chilling requirement in âChardonnay.â While the forcing effect of different temperatures and the length of the ecodormancy period were similar in both cultivars, resulting in an earlier bud break for âChardonnay.â Predicted dates of bud break were compared against 31 observed dates, showing a correlation of 0.95, an RMSE of 3.9 days and a MBE of -0.97 days was found, meaning that bud break estimations tend to occur earlier than the observed bud break. The accuracy of the model could be improved including an interaction effect between temperature and CDL for the endodormancy onset
Time-to-event analysis to evaluate dormancy status of single-bud cuttings: an example for grapevines
Abstract Background The reduced growth of plants during the winter causes a lack in the perceptibility of the phenological events making challenging the study of dormancy. For deciduous crops, dormancy is generally determined by evaluating budbreak of single-node cuttings that are exposed to conditions suitable for growth. However, the absence of a statistical basis for analyzing and interpreting the budbreak behavior evaluated as the percent budbreak, the average time to budbreak and the time to reach 50% budbreak, has caused inconsistent and contradictory criteria to identify the dormancy status of different deciduous crops. Results In this study, a method was developed to analyze the duration between sampling and budbreak of single-node cuttings and to estimate the dormancy status for grapevines (Vitis vinifera L.) based on the time-to-event distribution of the observations. This method estimates the probability curve of budbreak for each sample and classifies each curve into paradormancy, endodormancy, and ecodormancy according to the significance when compared to a sample curve estimated from cuttings collected during paradormancy and referred to as âreference.â Conclusion The approach described in this study provided a comparison of the budbreak distribution of cuttings collected during distinct phases with a confidence of 95%. It also allowed the estimation of the date of occurrence of the dormancy stages for two grapevine cultivars âCabernet Sauvignonâ and âChardonnay,â based on the variability within the sampling season rather than on fixed arbitrary criteria. This approach can also be used to analyze budbreak data of single-node cuttings from other common deciduous crops
Time-to-event analysis to evaluate dormancy status of single-bud cuttings: an example for grapevines
Report from Working Group 3: Beyond the Standard Model physics at the HL-LHC and HE-LHC
This is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as ab of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as ab of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will, generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics
Report from Working Group 3 : Beyond the Standard Model Physics at the HL-LHC and HE-LHC
CERN Yellow Reports: Monographs, vol 7 (2019)Contribution to: HL/HE-LHC WorkshopThis is the third out of five chapters of the final report [1] of the Workshop on Physics at HL-LHC, and perspectives on HE-LHC [2]. It is devoted to the study of the potential, in the search for Beyond the Standard Model (BSM) physics, of the High Luminosity (HL) phase of the LHC, defined as ab of data taken at a centre-of-mass energy of 14 TeV, and of a possible future upgrade, the High Energy (HE) LHC, defined as ab of data at a centre-of-mass energy of 27 TeV. We consider a large variety of new physics models, both in a simplified model fashion and in a more model-dependent one. A long list of contributions from the theory and experimental (ATLAS, CMS, LHCb) communities have been collected and merged together to give a complete, wide, and consistent view of future prospects for BSM physics at the considered colliders. On top of the usual standard candles, such as supersymmetric simplified models and resonances, considered for the evaluation of future collider potentials, this report contains results on dark matter and dark sectors, long lived particles, leptoquarks, sterile neutrinos, axion-like particles, heavy scalars, vector-like quarks, and more. Particular attention is placed, especially in the study of the HL-LHC prospects, to the detector upgrades, the assessment of the future systematic uncertainties, and new experimental techniques. The general conclusion is that the HL-LHC, on top of allowing to extend the present LHC mass and coupling reach by on most new physics scenarios, will also be able to constrain, and potentially discover, new physics that is presently unconstrained. Moreover, compared to the HL-LHC, the reach in most observables will, generally more than double at the HE-LHC, which may represent a good candidate future facility for a final test of TeV-scale new physics