Leonardo Rivera

Does plant diversity benefit agroecosystems? A synthetic review

Predictive theory on how plant diversity promotes herbivore suppression through movement patterns, host associations, and predation promises a potential alternative to pesticide-intensive monoculture crop production. We used meta-analysis on 552 experiments in 45 articles published over the last 10 years to test if plant diversification schemes reduce herbivores and/or increase the natural enemies of herbivores as predicted by associational resistance hypotheses, the enemies hypothesis, and attraction and repellency model applications in agriculture. We found extensive support for these models with intercropping schemes, inclusion of flowering plants, and use of plants that repel herbivores or attract them away from the crop. Overall, herbivore suppression, enemy enhancement, and crop damage suppression effects were significantly stronger on diversified crops than on crops with none or fewer associated plant species. However, a relatively small, but significantly negative, mean effect size for crop yield indicated that pest-suppressive diversification schemes interfered with production, in part because of reducing densities of the main crop by replacing it with intercrops or non-crop plants. This first use of meta-analysis to evaluate the effects of diversification schemes, a potentially more powerful tool than tallies of significant positive and negative outcomes (vote-counting), revealed stronger overall effects on all parameters measured compared to previous reviews. Our analysis of the same articles used in a recent review facilitates comparisons of vote-counting and meta-analysis, and shows that pronounced results of the meta-analysis are not well explained by a reduction in articles that met its stricter criteria. Rather, compared to outcome counts, effect sizes were rarely neutral (equal to zero), and a mean effect size value for mixed outcomes could be calculated. Problematic statistical properties of vote-counting were avoided with meta-analysis, thus providing a more precise test of the hypotheses. The unambiguous and encouraging results from this meta-analysis of previous research should motivate ecologists to conduct more mechanistic experiments to improve the odds of designing effective crop diversification schemes for improved pest regulation and enhanced crop yield.

Decision Support System for Operational Risk Management in Supply Chain with 3PL Providers

For organizations, it is essential to make good decisions regarding risks present both in the company and in its supply chain. The risk management process includes risk identification, evaluation, prioritization and quantification. The participation of Third Party Logistics providers (3PL) in supply chains has been increasing, and it is important to consider how their presence affects risk management. Finally, a decision support system helps decision makers to process, analyze and define actions related to large amounts of data. We present a multicriteria decision support system for effective management of the operational risks present in a supply chain that includes 3PL providers, specifically in ground transportation of goods. The model is supported by Fuzzy QFD for the prioritization of risks in terms of their impact on the performance indicators that are considered relevant by the actors in the supply chain. Findings indicate that the proposed model allows to prioritize the risks according with the most important indicators and for the case of study we found the most critical risks.

Priorización de Riesgos Operacionales para un Proveedor de Tercera Parte Logística - 3PL

espanolSe presenta una metodologia para la gestion de los riesgos operacionales en una compania proveedora de servicios logisticos, particularmente para los servicios de transporte y almacenamiento. Segun informes nacionales e internacionales, estos servicios son los que mas se subcontratan en la actualidad. La metodologia desarrollada utiliza una lista de chequeo para la identificacion de los riesgos, y la matriz de probabilidad e impacto, ademas del analisis jerarquico difuso (fuzzy analytic hierarchy process, AHP) para la priorizacion de los mismos. La metodologia ha sido validada en una empresa 3PL colombiana (servicios de logistica tercerizados) encontrandose que los riesgos mas relevantes son delitos como robos y actos terroristas. Tambien aparecen otros problemas tales como las huelgas y los defectos tecnicos en el transporte terrestre de las mercancias y el robo de la mercancia, desastres naturales y deterioro en el almacenamiento. Esta metodologia le permite a la organizacion emprender acciones para minimizar los riesgos que mayor impacto tienen en los resultados globales de la organizacion. EnglishA methodology for managing operational risks in a company that provides transportation services, specifically for its transportation and warehousing services is presented. According to domestic and international reports these are currently the most commonly outsourced services. The proposed methodology uses a checklist for the identification of risks, and the probability-impact matrix, besides the fuzzy analytic hierarchy process, AHP for their prioritization. The methodology was applied in a Colombian 3PL company (Third-Party Logistics) finding that the most relevant risks were crimes such as thefts and terrorist acts. It also appears other problems such as road blockages caused by protests, technical problems in ground transportation operations, product thefts, natural disasters, and product deterioration during storage. This methodology allows the organization to direct their actions to minimize risks that have higher global impact on the organization.

Performance Measurement in Lean Manufacturing Environments

This chapter presents the main metrics suggested for a lean manufacturing environment, as well as their use and application. The selection of metrics arises from a process that starts with the examination of a lean implementation, followed by the dimensions of improvement that will be examined. Then we suggest a set of metrics for each of the improvement dimensions, and we characterize the a priori impact that tools considered typical of lean manufacturing might have on the metrics. Based on this characterization we perform two types of analyses: A horizontal analysis to uncover the most critical performance indicators and a vertical analysis to present the lean tools that are most influential on the manufacturing system. We then propose different ways to use the indicators, based on their focus (results-oriented or process-oriented) and based on their scope (organizational scope and time scope). Finally, we propose future work to evaluate the impact and cost of implementing and operating a performance measurement system based on the metrics and their application we propose.