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Cacao (Theobroma cacao L.) is among the most important cash crops in tropical countries. The existing cacao genetic diversity represents a key resource to ensure the long-term sustainability of cacao cultivation but it remains vastly underused. The objective of this paper is to describe the current state of conservation and use of cacao genetic materials in six countries in South (Peru and Ecuador) and Central America (Nicaragua, Honduras, El Salvador, Guatemala). For each country, we reviewed the regulations for cacao genetic resources, we carried out a survey of 176 gene banks and nurseries, and we performed a review of breeding and selection programs. We found that all countries had poor systems of certification, verification and traceability. Gene banks conserved many local materials in Peru and Ecuador while they mainly conserved international clones in Central American countries. In all countries except Honduras, more than half of the gene banks did not have any characterization or evaluation data of the conserved materials. Although nurseries in all countries had fair productive capacities, varieties sold were unevenly characterized in Peru, Ecuador and Guatemala, and less than half of the nurseries provided technical assistance to farmers in Ecuador and El Salvador. Breeding and selection programs had not fully used the cacao diversity in these countries. Based on the results, we identified the strengths and weakness, as well as the most appropriate investment areas for each country. A better conservation and use of cacao genetic resources in Latin America would benefit not only these countries but also the whole cacao sector.

An estimated 3.41 million hectares of cocoa and 8.08 million hectares of coffee are cultivated under shade trees i.e. in agroforestry systems. Shade canopies are usually characterized in terms of tree density (N, trees ha-1), tree basal area (G, m2 ha-1) and percent canopy cover (%C). This article shows that these variables have cross-compensation effects that reduce their capacity to inform on the shading conditions in the understory. Density and basal area are not directly related to canopy cover (and hence to shading) and need additional assumptions about both tree size and species-specific allometric relationships between stem diameter and crown diameter. This article explores the compensatory effects between these variables and uses simulations with the software ShadeMotion (www.shademotion.net) to show how 24 different, simple, even-sized, mono-layered, Cordia alliodora shade canopies with constant N, G and %C display significantly different shade levels and temporal patterns of shading depending on tree stem and crown diameters, tree height, spatial planting configurations (square, random and alleys) and leaf fall patterns. A minimum set of variables capable of providing a more informative description of the shading characteristics of a cocoa or coffee shade canopy is proposed. Findings in this study can shed light on the current, heated debate on the pros and cons of definitions of cocoa agroforestry used by chocolate companies, governments, certification companies, NGOs, and donors, especially in West and Central Africa. In this article, emphasis is given to cocoa, but the analysis, results and conclusions are equally applicable to coffee agroforestry systems.

AbstractCocoa farmers must decide on whether to rehabilitate (Rh) or to renovate (Re) a cocoa orchard when its productivity declines due to ageing, disease outbreaks or other causes. Deciding on Rh/Re is often a complex, expensive and conflictive process.In this review, we (1) explore the diversity of contexts, driving forces, stakeholders and recommended management practices involved in Rh/Re initiatives in key cocoa-producing countries; (2) summarise the often conflicting views of farmers and extension agents on Rh/Re programmes; (3) review the evidence of age-related changes in planting density and yield of cocoa, given the weight of these variables in Rh/Re decision processes; (4) describe the best known Rh/Re systems and their most common management practices; (5) propose an agroforestry Re approach that overcomes the limitation of current Rh/Re diagnosis protocols, which do not consider the regular flow of food crop and tree products, and the need to restore site soil quality to sustain another cycle of cultivation of cocoa at the same site; and (6) explore the effects of climate change considerations on Rh/Re decision-making and implementation processes.Each Rh/Re decision-making process is unique and highly context-dependent (household and farm, soil, climate, culture). Tailored solutions are needed for each farmer and context. The analysis, concepts and models presented for cocoa in this paper may also apply to coffee orchards.

Cocoa cultivation is labeled as a driver of both deforestation and reforestation, yet the extent of the phenomena varies at farm and landscape level and as a response to national and local contexts. In this study, we documented the main pathways and contexts behind cocoa cultivation in two sites with different histories of cocoa cultivation. We combined official statistics, land-use trajectory, satellite imagery, and the Q-analysis to explore the discourses of country experts in Nicaragua and Peru. The Q-statements were based on an analysis of a set of legal, institutional, social, and technical guidelines that the cocoa cultivation/sector influences or is influenced by. Based on the responses of national experts to 31 statements we found four discourses linking cocoa cultivation and reforestation and deforestation in each country-case study. The enabling and limiting conditions driving tree cover change were a combination of landscape configuration, governance, management/commercialization models, and farmer's knowledge. Overall, between 60 and 64% of the variance was explained by four discourse factors in each country. In Nicaragua, the conditions associated with reforestation were the cocoa-agroforestry model promoted by local organizations/NGOs, the existence of incentives, degree of technical knowledge, access to safe market, and availability of improved genetic material. The circumstances associated with deforestation were the age of the farmers, fluctuation of cocoa beans prices, low productivity of cocoa plantations, and weak legal environmental frameworks. Whereas, in Peru, the main factors connecting cocoa cultivation to reforestation were access to market, degree of experimentation in cocoa, the economic weight of cocoa on family's income, certification processes, the existence of incentives, and the level of organization/association of cocoa farmers. The elements linking cocoa farming to deforestation were the influence of stakeholders in the cocoa value chain, weak legal environmental frameworks, fluctuation of cocoa prices, the existence of private investors, and insecure land tenure rights. This article demonstrated the utility of discourse analysis, through its application to two contrasting country case-studies, to elucidate the conditions that might minimize the deforestation footprint of cocoa cultivation and maximize its role as an agent for reforestation/restoration in the agricultural landscape of cocoa-growing areas in Latin America.

Research on urban forests has expanded in the last 30 years in the US, Canada, Europe, and Australia. Nonetheless, urban forestry has been explored to much less extent in the Latin America and the Caribbean region, despite being one of the most urbanized and biodiverse regions in the world. We address this gap by providing a baseline understanding of urban forest research in the region based on a systematic review of the academic literature. Of the 55,000 studies found, 195 were selected for review, and 182 were analysed and synthesized. These studies came from 13 countries and were published from 1970 to mid-2018 (inclusive) in English, Spanish, and Portuguese. Almost half of the studies were based in Brazil, followed by Mexico and Chile. To comparatively assess article output by country, we accounted for country population and Brazil, Chile, Nicaragua, and Puerto Rico had higher than average per capita article output. Most articles were ecological studies (64%) that used field surveys (58%) to research urban vegetation diversity. Most ecological studies did not include any social or management considerations. Only a few studies focused on spatiotemporal dynamics (12%) or the direct opinions of stakeholders (9%). We observed a notable increase in article output from the region during the last decade. The units of analysis targeted by these studies mostly focused on single trees in public areas (streets and parks). Understanding urban forests regionally could be strengthened by scaling up research across multiple units of analysis and across regional cities, which could provide a better understanding of regional spatiotemporal dynamics. To respond to current global trends and nurture regional strengths, research could also focus on a wider range of ecosystem services provided by urban forests, and the relationship of urban forests with poverty, crime, climate vulnerability, biodiversity loss, and social equity. These findings can inform key stakeholders in the region managing urban forests and trees about research trends and gaps to be filled. This article shows that the region indeed has an important body of research in urban forestry that should be recognized in global assessments. © 2019 Elsevier GmbH

Assessing tree growth trends over time is a central but challenging aspect of urban forest management. The potential damage caused by invasive devices used in dendrochronological analysis is a common concern among urban foresters. Thus, the development of a less-invasive method for assessing tree growth rate faster that provides reliable results is clearly beneficial. In this study, resistance drilling (RD) profiles were compared with stem core assessments (Core) to estimate the growth rate of 78 trees of three species (Quercus robur, Ulmus procera, and Platanus x acerofolia). All studied trees were core-sampled in 2013 and then resistance drilled in 2015 at a stem height of 1–1.3 m in both north (N) and west axes (W). The dependency and accuracy of paired annual ring series (CORE measurements and Resi reading) were tested using ANOVA and regression analysis. In addition, point and event year tests were determined to confirm the accuracy of the RD to assess growth trends at both population and tree level. Growth series from both methods were cross-dated to test the reliability of RD to relate historical tree growth to past climatic conditions. ANOVA analysis confirmed that average ring width values and age of 70 out of 78 trees were statistically similar for both methods and similar for both sampled stem axes. Within each tree, regression analysis indicated significant correlation between cored ring datasets and paired resistance drilled ring datasets (R2 = 0.78–0.95, p

PURPOSE While dental implants have displayed high success rates, poor mechanical fixation is a common complication, and their biomechanical response to occlusal loading remains poorly understood. This study aimed to develop and validate a computational model of a natural first premolar and a dental implant with matching crown morphology, and quantify their mechanical response to loading at the occlusal surface. MATERIALS AND METHODS A finite-element model of the stomatognathic system comprising the mandible, first premolar and periodontal ligament (PDL) was developed based on a natural human tooth, and a model of a dental implant of identical occlusal geometry was also created. Occlusal loading was simulated using point forces applied at seven landmarks on each crown. Model predictions were validated using strain gauge measurements acquired during loading of matched physical models of the tooth and implant assemblies. RESULTS For the natural tooth, the maximum vonMises stress (6.4 MPa) and maximal principal strains at the mandible (1.8 me, -1.7 me) were lower than those observed at the prosthetic tooth (12.5 MPa, 3.2 me, and -4.4 me, respectively). As occlusal load was applied more bucally relative to the tooth central axis, stress and strain magnitudes increased. CONCLUSION Occlusal loading of the natural tooth results in lower stress-strain magnitudes in the underlying alveolar bone than those associated with a dental implant of matched occlusal anatomy. The PDL may function to mitigate axial and bending stress intensities resulting from off-centered occlusal loads. The findings may be useful in dental implant design, restoration material selection, and surgical planning.

Most allometric equations currently used to quantify above-ground biomass of urban trees are derived from natural forest stands and can produce unreliable estimates of biomass for individual trees grown in open conditions. In addition, distribution of standing volume between stem, branch and foliage in solitary grown urban trees is poorly understood. In this study, a total of 45 trees of three species (Ulmus procera, n = 15, Corymbia maculta, n = 15 and, Platanus x acerofolia, n = 15) of different size (small, medium and large) were measured. For six trees of each species (18 in total), the stem and all major branches were fully mapped so that an accurate wood volume was established, and various random branch samples (RBS) and composites could be used to estimate standing volume. For the remaining nine trees of each tree species standing volume was estimated by only measuring five RBS pathways. Allometric relationships between diameter and volume were explored using linear, quadratic, cubic, log and exponential models. Slenderness ratio (SR) and bifurcation ratio (BR) were derived to explore canopy structure among species. U. procera trees showed the greatest BR, followed by P. x acerifolia and lowest in C. maculata. In U. procera, SR displayed a decreasing trend from scaffolds to third order branches while the opposite was true for C. maculata and P. x acerifolia. Number and dimensions of scaffolds, first and second order branches of small and medium size trees were similar but differed from that of large trees. Overall, standing volume distribution among species was 40% to the main stem and 60% to the crown. Across species and tree size class, RBS systematically under- or over-estimated standing volume in the range of -30% to +42% as compared to full tree measurements. Regardless of tree size, allometric relationships were similar within species but varied among crown structural parts. Linear models better explained diameter-volume relationships of whole tree and main stem across species. Log-Log and polynomial models better described diameter-volume relationships of branches of all orders. These findings suggest that a set of allometric equations could be developed to more accurately predict standing volume yield of urban trees.