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Two studies conducted in Guadeloupe (West Indies) and Réunion (Indian Ocean) islands were designed to investigate the benefits of producing sugarcane as an energy crop and to assess the influence of agroclimatic factors on energy efficiency, respectively. In this context, it is essential to know the low heating value of the dry above-ground biomass (LHVd, MJ/kg) and its energy yield (EY, MJ/m2) in order to select the best varieties and set up a payment method for growers. Eighteen Poaceae (sugarcane and Erianthus) cultivars were compared under wet tropical environmental conditions in Guadeloupe. Three sugarcane cultivars were studied in four contrasting environments in Réunion. The partition sampling and biomass measurement procedures were identical at both locations. Low heating value (LHV) predictions were achieved using near-infrared reflectance spectroscopy (NIRS) after specific calibration (Guadeloupe), or arithmetically after lignocellulosic compound prediction (Réunion). In both studies, LHV variability was very low and slightly dependent on the site, cultivar and above-ground biomass components (millable stalks and tops, and green and dead leaves). Considering the overall dry above-ground biomass (DAB, kg/m2), the LHVd was calculated by averaging 159 samples (mean 16.65 MJ/kg) in Guadeloupe and 315 samples (mean 16.45 MJ/kg) for Réunion. An excellent linear relationship between the DAB and its EY, regardless of cultivar, age and environment, was found (n = 474 and R² = 0.99). Sugarcane energy content assessment could thus be simplified by measuring the DAB, while enabling development of a faster method of payment for growers based on the DAB measurement and the correlation between DAB and EY. Finally, the findings of this study should allow growers to rapidly determine the commercial value of their sugarcane crops, and also enable purchasers to assess the amount of recoverable energy. (Résumé d'auteur)

Abstract The introduction of nitrogen fixing species (NFS) in fast-growing tree plantations is an alternative option to reduce fertilizer inputs. However, the success of mixed-species plantations depends on the balance between positive interactions among species (resulting from facilitation and/or complementarity) and the negative effects of interspecific competition. Using a carbon budget approach and coupling measurements of standing biomass, aboveground litterfall and soil CO2 efflux, we assessed the influence of replacing half of eucalypt trees by Acacia mangium on total belowground carbon flux (TBCF), net primary production (NPP) and its partitioning between above- and belowground growth at two tropical sites in Brazil (Itatinga) and in Congo (Kissoko) exhibiting contrasting climates, edaphic conditions and wood productions. Annual soil CO2 efflux (FS) was significantly lower in the acacia monocultures than in eucalypt monocultures and mixed-species stands at both sites. Annual FS was significantly lower at Itatinga compared to Kissoko for all stands while TBCF was significantly lower in the eucalypt stands only. In the eucalypt monocultures we found a significantly lower aboveground NPP (ANPP) and wood production (wood NPP) at Kissoko compared to Itatinga that was almost fully balanced by a significantly higher belowground NPP (BNPP), leading to similar NPP. Similarly, acacia monocultures exhibited significantly higher ANPP and wood NPP at Itatinga than at Kissoko. The mixed-species stands exhibited a significantly lower wood NPP and ANPP than the eucalypt monocultures at the Brazilian site while NPP of the mixture was not significantly different than the average NPP of the two monocultures. At the Congolese site, NPP of the mixture was significantly higher than the average NPP of the two monocultures. NPP was similar in the mixed-species stand and the eucalypt monoculture with a significantly lower partitioning of NPP to belowground production, leading to a one third higher wood biomass at harvest in the mixed-species stand. A positive effect of growing eucalypts with the nitrogen fixing acacia trees on stand wood production occurred at Kissoko but not at Itatinga. Mixed-species plantations with NFS can be advocated at sites where the productive gains resulting from nitrogen fixation are not compromised by other resource limitations.

Antestiopsis thunbergii (Gmelin 1790) est un ravageur majeur du café Arabica en Afrique. L'insecte préfère le café aux plus hautes altitudes, contrairement à d'autres ravageurs majeurs. Les objectifs de cette étude étaient de décrire la relation entre les populations d'A. thunbergii et l'altitude, d'élucider cette relation en utilisant nos connaissances de la biologie thermique des ravageurs et de prédire la distribution des ravageurs sous le réchauffement climatique. La densité de population d'Antestiopsis thunbergii a été évaluée dans 24 plantations de café situées le long d'un transect délimité par un gradient d'altitude compris entre 1000 et 1700 m asl, sur le mont. Kilimandjaro, Tanzanie. La densité a été évaluée pour trois saisons climatiques différentes, la saison sèche fraîche en juin 2014 et 2015, la courte saison des pluies en octobre 2014 et la saison sèche chaude en janvier 2015. La distribution des ravageurs a été prédite sur le même transect à l'aide de trois indices de risque : l'indice de risque d'établissement (ERI), l'indice de génération (GI) et l'indice d'activité (AI). Ces indices ont été calculés à l'aide de paramètres de la table de survie simulés obtenus à partir de modèles de développement dépendant de la température et de données de température provenant 1) d'enregistrements sur le terrain à l'aide d'enregistreurs de données déployés sur le transect et 2) de prédictions pour l'année 2055 extraites de la base de données AFRICLIM. La densité de population observée était la plus élevée pendant la saison sèche fraîche et augmentait significativement avec l'augmentation de l'altitude. Pour la température actuelle, l'ERI a augmenté avec une augmentation de l'altitude et a donc été distribué de manière similaire aux populations observées, contrairement aux autres indices. Ce résultat suggère que la sensibilité au stade immature aux températures extrêmes était un facteur clé de la répartition de la population affectée par l'altitude. À l'avenir, la distribution des indices de risque à l'échelle mondiale a indiqué une diminution du risque à basse altitude et une augmentation du risque aux plus hautes altitudes. Sur la base de ces résultats, nous avons conclu avec des recommandations pour atténuer le risque d'infestation par A. thunbergii. El insecto antestia, Antestiopsis thunbergii (Gmelin 1790) es una plaga importante del café Arábica en África. El insecto prefiere el café en las alturas más altas, a diferencia de otras plagas importantes. Los objetivos de este estudio fueron describir la relación entre las poblaciones de A. thunbergii y la elevación, dilucidar esta relación utilizando nuestro conocimiento de la biología térmica de las plagas y predecir la distribución de las plagas bajo el calentamiento climático. La densidad de población de Antestiopsis thunbergii se evaluó en 24 fincas de café ubicadas a lo largo de un transecto delimitado a través de un gradiente de elevación en el rango de 1000-1700 m s.n.m., en el monte Kilimanjaro, Tanzania. La densidad se evaluó para tres estaciones climáticas diferentes, la estación seca fría en junio de 2014 y 2015, la estación lluviosa corta en octubre de 2014 y la estación seca cálida en enero de 2015. La distribución de Pest se predijo sobre el mismo transecto utilizando tres índices de riesgo: el índice de riesgo de establecimiento (ERI), el índice de generación (GI) y el índice de actividad (AI). Estos índices se calcularon utilizando parámetros de la tabla de vida simulada obtenidos de modelos de desarrollo dependientes de la temperatura y datos de temperatura de 1) registros de campo utilizando registradores de datos desplegados en el transecto y 2) predicciones para el año 2055 extraídas de la base de datos AFRICLIM. La densidad de población observada fue la más alta durante la estación seca fresca y aumentó significativamente con el aumento de la altitud. Para la temperatura actual, el ERI aumentó con un aumento en la elevación y, por lo tanto, se distribuyó de manera similar a las poblaciones observadas, a diferencia de los otros índices. Este resultado sugiere que la susceptibilidad de la etapa inmadura a temperaturas extremas fue un factor clave de la distribución de la población afectada por la altitud. En el futuro, la distribución de los índices de riesgo a nivel mundial indicó una disminución del riesgo a baja altitud y un aumento del riesgo a las alturas más altas. Con base en estos resultados, concluimos con recomendaciones para mitigar el riesgo de infestación por A. thunbergii. The antestia bug, Antestiopsis thunbergii (Gmelin 1790) is a major pest of Arabica coffee in Africa. The bug prefers coffee at the highest elevations, contrary to other major pests. The objectives of this study were to describe the relationship between A. thunbergii populations and elevation, to elucidate this relationship using our knowledge of the pest thermal biology and to predict the pest distribution under climate warming. Antestiopsis thunbergii population density was assessed in 24 coffee farms located along a transect delimited across an elevation gradient in the range 1000-1700 m asl, on Mt. Kilimanjaro, Tanzania. Density was assessed for three different climatic seasons, the cool dry season in June 2014 and 2015, the short rainy season in October 2014 and the warm dry season in January 2015. The pest distribution was predicted over the same transect using three risk indices: the establishment risk index (ERI), the generation index (GI) and the activity index (AI). These indices were computed using simulated life table parameters obtained from temperature-dependent development models and temperature data from 1) field records using data loggers deployed over the transect and 2) predictions for year 2055 extracted from AFRICLIM database. The observed population density was the highest during the cool dry season and increased significantly with increasing elevation. For current temperature, the ERI increased with an increase in elevation and was therefore distributed similarly to observed populations, contrary to the other indices. This result suggests that immature stage susceptibility to extreme temperatures was a key factor of population distribution as impacted by elevation. In the future, distribution of the risk indices globally indicated a decrease of the risk at low elevation and an increase of the risk at the highest elevations. Based on these results, we concluded with recommendations to mitigate the risk of A. thunbergii infestation. حشرة أنتيستيا، Antestiopsis thunbergii (Gmelin 1790) هي آفة رئيسية من قهوة أرابيكا في أفريقيا. يفضل الحشرة القهوة على أعلى المرتفعات، على عكس الآفات الرئيسية الأخرى. كانت أهداف هذه الدراسة هي وصف العلاقة بين مجموعات A. thunbergii والارتفاع، لتوضيح هذه العلاقة باستخدام معرفتنا ببيولوجيا الآفات الحرارية والتنبؤ بتوزيع الآفات في ظل الاحترار المناخي. تم تقييم الكثافة السكانية لـ Antestiopsis thunbergii في 24 مزرعة بن تقع على طول مقطع عرضي محدد عبر تدرج الارتفاع في نطاق 1000-1700 متر، على جبل. كليمنجارو، تنزانيا. تم تقييم الكثافة لثلاثة مواسم مناخية مختلفة، وموسم الجفاف البارد في يونيو 2014 و 2015، وموسم الأمطار القصير في أكتوبر 2014 وموسم الجفاف الدافئ في يناير 2015. تم التنبؤ بتوزيع الآفات على نفس المقطع باستخدام ثلاثة مؤشرات للمخاطر: مؤشر مخاطر المؤسسة (ERI) ومؤشر التوليد (GI) ومؤشر النشاط (AI). تم حساب هذه المؤشرات باستخدام معلمات جدول الحياة المحاكاة التي تم الحصول عليها من نماذج التطوير المعتمدة على درجة الحرارة وبيانات درجة الحرارة من 1) السجلات الميدانية باستخدام مسجلات البيانات المنتشرة عبر المقطع و 2) التنبؤات لعام 2055 المستخرجة من قاعدة بيانات AFRICLIM. كانت الكثافة السكانية المرصودة هي الأعلى خلال موسم الجفاف البارد وزادت بشكل كبير مع زيادة الارتفاع. بالنسبة لدرجة الحرارة الحالية، زاد مؤشر الاستبدال الانتقائي مع زيادة في الارتفاع وبالتالي تم توزيعه بشكل مشابه للمجموعات المرصودة، على عكس المؤشرات الأخرى. تشير هذه النتيجة إلى أن قابلية المرحلة غير الناضجة لدرجات الحرارة القصوى كانت عاملاً رئيسياً في توزيع السكان حيث تأثر بالارتفاع. في المستقبل، أشار توزيع مؤشرات المخاطر على مستوى العالم إلى انخفاض المخاطر عند الارتفاعات المنخفضة وزيادة المخاطر عند أعلى الارتفاعات. وبناءً على هذه النتائج، خلصنا إلى توصيات للتخفيف من خطر الإصابة بمرض A. thunbergii.

AbstractMaximizing initial aboveground woody biomass (AGB) accumulation in order to obtain early payments for carbon stocking is essential for the financial viability of reforestation programs fostered by climate mitigation efforts. Intensive silviculture, i.e., silviculture traditionally used in commercial forestry to maximize productivity and gains, has recently been advocated as a promising approach to enhance AGB accumulation in restoration plantations. However, this approach may hamper natural forest regeneration and ecological succession due to high competition between colonizing plants and planted trees. We investigated the impacts of different silvicultural treatments applied to restoration plantations with 20 native tree species on AGB accumulation and spontaneous regeneration of native woody species in an experiment set up in the Atlantic Forest of Brazil. Intensive silviculture demonstrated a remarkable potential to enhance AGB accumulation in restoration plantations by increasing up to three times the AGB of tree stands (from ~25 to 75 Mg/ha in the 12th year). Intensive fertilization/weed control enhanced AGB accumulation, while higher tree density and the proportion of pioneers did not have a significant effect on AGB over the time. In spite of higher costs (cost increase of 13–19%), the cost‐effectiveness for AGB accumulation of intensive silviculture was comparable to that of traditional silviculture applied to restoration (US$50–100/Mg AGB for 3 × 2 m spacing). Contrary to our expectations, we did not find a trade‐off between AGB accumulation by planted trees and the spontaneous regeneration of tree species, since intensive silviculture enhanced the regeneration of both planted (total of 12 species) and colonizing woody species (total of 30 species) in the plantation understory. Specifically, a strong association was found between AGB stocks and the abundance and richness of colonizing species, a vast majority of which (90% of species and 95% of individuals) were dispersed by animals. We report a case of positive correlation between AGB stocking and woody species regeneration in the restoration of the Atlantic Forest. Fostering the establishment and maintenance of restoration tree plantations can, in some cases, be a win‐win strategy for climate mitigation and biodiversity conservation in human‐modified tropical landscapes.

Conservation agriculture (CA) is considered a possible option for reducing the environmental impact of tilled maize on sloping land in two mountainous districts of northern Vietnam. Within this context, our study aimed at building a regional farm typology that can support the design of CA cropping systems, suiting different farm types. 411 maize-producing farms were surveyed. Using multivariate analysis, we identified 5 farm types with contrasting resources and sustainability performances. We discuss the range of possible CA systems to be designed for each type, according to its specific constraints and opportunities. We especially consider diverse intensification levels and kinds of cover plants. We propose the development of farm models to further explore the economic attractiveness of the options selected for each type.

Air gasification of Solid Recovered Fuels (SRF) from wood, tire, plastics and sewage sludge has been performed in a pilot fixed bed reactor. As wastes contain pollutants precursors, it is of great interest regarding technical and environmental aspects to study their behavior in air gasification. Five fuels have been studied: Poplar, SRF wood, and three different mixtures of SRF wood and 20% of either tire (mix A), or plastics (mix B) or sewage sludge (mix C). After confirming their capacity of substituting raw wood in order to produce synthetic gas (syngas), emissions analyses have been performed on syngas, condensable matter and remaining char. A focus on sulfur, nitrogen and heavy metals brought to light differences and similarities between different SRF and raw wood. Proceedings of the 26th European Biomass Conference and Exhibition, 14-17 May 2018, Copenhagen, Denmark, pp. 478-485