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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.

AbstractClimate change is most strongly felt in the polar regions of the world, with significant impacts on the species that live there. The arrival of parasites and pathogens from more temperate areas may become a significant problem for these populations, but current observations of parasite presence often lack a historical reference of prior absence. Observations in the high Arctic of the seabird tick Ixodes uriae suggested that this species expanded poleward in the last two decades in relation to climate change. As this tick can have a direct impact on the breeding success of its seabird hosts and vectors several pathogens, including Lyme disease spirochaetes, understanding its invasion dynamics is essential for predicting its impact on polar seabird populations. Here, we use population genetic data and host serology to test the hypothesis that I. uriae recently expanded into Svalbard. Both black‐legged kittiwakes (Rissa tridactyla) and thick‐billed murres (Uria lomvia) were sampled for ticks and blood in Kongsfjorden, Spitsbergen. Ticks were genotyped using microsatellite markers and population genetic analyses were performed using data from 14 reference populations from across the tick's northern distribution. In contrast to predictions, the Spitsbergen population showed high genetic diversity and significant differentiation from reference populations, suggesting long‐term isolation. Host serology also demonstrated a high exposure rate to Lyme disease spirochaetes (Bbsl). Targeted PCR and sequencing confirmed the presence of Borrelia garinii in a Spitsbergen tick, demonstrating the presence of Lyme disease bacteria in the high Arctic for the first time. Taken together, results contradict the notion that I. uriae has recently expanded into the high Arctic. Rather, this tick has likely been present for some time, maintaining relatively high population sizes and an endemic transmission cycle of Bbsl. Close future observations of population infestation/infection rates will now be necessary to relate epidemiological changes to ongoing climate modifications.

Though there are surprisingly few estimates of the economic benefits of coordinated infrastructure development and operations in international river basins, there is a widespread belief that improved cooperation is beneficial for managing water scarcity and variability. Hydro-economic optimization models are commonly-used for identifying efficient allocation of water across time and space, but such models typically assume full coordination. In the real world, investment and operational decisions for specific projects are often made without full consideration of potential downstream impacts. This paper describes a tractable methodology for evaluating the economic benefits of infrastructure coordination. We demonstrate its application over a range of water availability scenarios in a catchment of the Mekong located in Lao PDR, the Nam Ngum River Basin. Results from this basin suggest that coordination improves system net benefits from irrigation and hydropower by approximately 3–12% (or US$12-53 million/yr) assuming moderate levels of flood control, and that the magnitude of coordination benefits generally increases with the level of water availability and with inflow variability. Similar analyses would be useful for developing a systematic understanding of the factors that increase the costs of non-cooperation in river basin systems worldwide, and would likely help to improve targeting of efforts to stimulate complicated negotiations over water resources.

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.

Dans cette étude, nous étudions les changements de température et les précipitations extrêmes en Afrique de l'Ouest et du Centre (ci-après, domaine WAF) en fonction de la température moyenne mondiale en mettant l'accent sur les implications du réchauffement climatique de 1,5 °C et 2 °C conformément à l'Accord de Paris. Nous avons appliqué une approche de mise à l'échelle pour capturer les changements dans les extrêmes climatiques avec l'augmentation de la température moyenne mondiale dans plusieurs sous-régions du domaine WAF : Sahel occidental, Sahel central, Sahel oriental, côte de Guinée et Afrique centrale, y compris le bassin du Congo. En este estudio, investigamos los cambios en la temperatura y las precipitaciones extremas en África occidental y central (en adelante, el dominio WAF) en función de la temperatura media global, centrándonos en las implicaciones del calentamiento global de 1,5 °C y 2 °C según el Acuerdo de París. Aplicamos un enfoque de escala para capturar los cambios en los extremos climáticos con el aumento de la temperatura media global en varias subregiones dentro del dominio WAF: Sahel Occidental, Sahel Central, Sahel Oriental, Costa de Guinea y África Central, incluida la Cuenca del Congo. في هذه الدراسة، نقوم بالتحقيق في التغيرات في درجات الحرارة وهطول الأمطار القصوى فوق غرب ووسط أفريقيا (فيما يلي، مجال غرب ووسط أفريقيا) كدالة لمتوسط درجة الحرارة العالمية مع التركيز على الآثار المترتبة على الاحترار العالمي من 1.5 درجة مئوية و 2 درجة مئوية وفقا لاتفاق باريس. طبقنا نهج التدرج لالتقاط التغيرات في الظواهر المناخية المتطرفة مع زيادة متوسط درجة الحرارة العالمية في العديد من المناطق دون الإقليمية داخل نطاق منطقة غرب أفريقيا: الساحل الغربي والساحل الأوسط والساحل الشرقي وساحل غينيا ووسط أفريقيا بما في ذلك حوض الكونغو. In this study, we investigate changes in temperature and precipitation extremes over West and Central Africa (hereafter, WAF domain) as a function of global mean temperature with a focus on the implications of global warming of 1.5 °C and 2 °C according the Paris Agreement. We applied a scaling approach to capture changes in climate extremes with increase in global mean temperature in several subregions within the WAF domain: Western Sahel, Central Sahel, Eastern Sahel, Guinea Coast and Central Africa including Congo Basin.

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.