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Ocho años de estudio de la ecofisiología del café, a través de experimentación y de modelación y el monitoreo de los servicios del ecosistema (SE) en una gran finca cafetalera en Costa Rica, revelaron varias recomendaciones prácticas para los agricultores y los formuladores de políticas. El sistema de cultivo estudiado dentro de nuestro observatorio colaborativo (Coffee-Flux), corresponde a un sistema agroforestal (SAF) a base de café bajo la sombra de grandes árboles de Erythrina poeppigiana (16% de la cubierta del dosel). Una gran cantidad de SE y limitantes dependen de las propiedades locales del suelo (en este caso Andisoles), especialmente de la erosión/infiltración, el agua/carbono y la capacidad de almacenamiento de nutrientes. Por lo tanto, para la evaluación de SE, el tipo de suelo es crucial. Una densidad adecuada de árboles de sombra (bastante baja aquí por la condición de libre crecimiento), redujo la severidad de las enfermedades de las hojas con la posibilidad de reducir el uso de plaguicidas y fungicidas. Un inventario simple del área basal en el collar de las plantas de café permitió estimar la biomasa subterránea y la edad promedio de la plantación, para juzgar su valor de mercado y decidir cuándo reemplazarla. Las fincas de café probablemente estén mucho más cerca de la neutralidad de C que lo indicado en el protocolo actual de C-neutralidad, que solo considera árboles de sombra, no los cafetos ni el suelo. Se proponen evaluaciones más completas, que ncluyen árboles, café, hojarasca, suelo y raíces en el balance C del SAF. Los árboles de sombra ofrecen muchos SE si se gestionan adecuadamente en el contexto local. En comparación con las condiciones a pleno sol, los árboles de sombra pueden (i) reducir la erosión laminar en un factor de 2; (ii) aumentar la fijación de N y el % de N reciclado en el sistema, reduciendo así los requisitos de fertilizantes; (iii) reducir la severidad de enfermedades de las hojas; (iv) aumentar el secuestro de C; (v) mejorar el microclima y (vi) reducir sustancialmente los efectos del cambio climático. En nuestro estudio de caso, no se encontró ningún efecto negativo sobre el rendimiento del café.

Agro-silvo-pastoralism is a highly representative Land Use in Africa, often presented as a strategical option for ecological intensification of cropping systems towards food security and sovereignty.We set up a new long-term observatory (“Faidherbia-Flux”) to monitor and model microclimate, energy and C balance in Niakhar (central Senegal, rainfall ~ 500 mm), dominated by the multipurpose tree Faidherbia albida (12.5 m high; 7 tree ha-1; 5% canopy cover). Faidherbia is an attractive agroforestry tree species in order to partition fluxes, given that it is on leaf during the dry season (October-June) and defoliated during the wet season, just when crops take over. Pearl-millet and groundnut crops were conducted during the wet season, following annual rotation in a complex mixed mosaic of ca. 1 ha fields.Early 2018, we installed an eddy-covariance (EC) tower above the whole mosaic (EC1: 20 m high). A second EC system was displayed above the crop (EC2: 4.5 m if pearl-millet, 2.5 m if groundnut) in order to partition ecosystem EC fluxes between tree layer and crop+soil layers. Sap-flow was monitored from April 2019 onwards in 5 faidherbia trees (37 sensors).The ecosystem displayed moderate but significant daily CO2 and H2O fluxes during the dry season, when faidherbia (low canopy cover) was in leaf and the soil was evaporating. At the onset of the rainy season, the soil bursted a large amount of CO2. Just after the growth of pearl-millet in 2018, CO2 uptake by photosynthesis increased dramatically. However, this was largely compensated by high ecosystem respiration. Surprisingly in 2019, although the crop was turned to groundnut, the fluxes behaved pretty much the same as with pearl millet in 2018: comparing annual balances between 2018 and 2019 we obtained [454, 513] for rainfall (P: mm yr-1), [3500, 3486] for potential evapotranspiration (ETo: mm yr-1), [0.13, 0.15] for P/ETo, [470, 497] for actual evapotranspiration (E: mm yr-1), [2809, 2785] for net radiation (Rn: MJ m-2 yr-1), [1686, 1645] for sensible heat flux (H: MJ m-2 yr-1), [-3.2, -2.8] for net ecosystem exchange of C (NEE: tC ha-1 yr-1), [-11.8, -11.1] for gross primary productivity (GPP: tC ha-1 yr-1) and [8.6, 8.3] for ecosystem respiration (Re: tC ha-1 yr-1). The energy balance (Rn-H-LE) was nearly nil indicating that the EC system behaved reasonably. E was very close to P, indicating that little or no water would recharge the deep soil layers.Now comparing the dry (2/3 of the year) and wet (1/3) seasons: surprisingly, NEE was more effective during the dry season [-3.9, -1.7]. This was the result of Re being much lower on a daily basis as well as cumulated over the entire seasons [57, 84], whereas GPP was similar [-10.8, -12.1].We found a good match between E measured above the whole ecosystem (EC1), and the sum of tree transpiration (T, measured by sapflow) + E measured just above crops + soil (EC2) throughout the wet and dry seasons.The “Faidherbia-Flux” observatory is registered in FLUXNET as SN-Nkr and is widely open for collaboration.

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Huit ans de travaux de recherche sur les services écosystémiques dans une grande ferme caféière du Costa Rica (observatoire collaboratif Coffee-Flux, en système agroforestier à base de caféiers sous de grands arbres d'Erythrina poeppigiana, surface projetée de couronne de l'ordre de 16 %) ont suggéré plusieurs applications pour les agriculteurs et les décideurs. Il est apparu que de nombreux services écosystémiques dépendaient des propriétés du sol (ici des Andisols), en particulier de l'érosion, de l'infiltration, de la capacité de stockage de l'eau et des éléments nutritifs. Nous confirmons qu'il est essentiel de lier les services hydrologiques et de conservation au type de sol en présence. Une densité adéquate d'arbres d'ombrage (plutôt faible ici) permet de réduire la sévérité des maladies foliaires avec, en perspective, une réduction de l'usage de pesticides-fongicides. Un simple inventaire de la surface basale au collet des caféiers permet d'estimer la biomasse souterraine et la moyenne d'âge d'une plantation de caféiers, ce qui permet d'évaluer sa valeur marchande ou de planifier son remplacement. Le protocole de calcul actuel pour la neutralité carbone des systèmes agroforestiers ne prend en compte que les arbres d'ombrage, pas la culture intercalaire. Dans la réalité, si on inclut les caféiers, on se rapproche très probablement de la neutralité. Des évaluations plus complètes, incluant les arbres, les caféiers, la litière, le sol et les racines dans le bilan en carbone du système agroforestier sont proposées. Les arbres d'ombrage offrent de nombreux servies écosystémiques s'ils sont gérés de manière adéquate dans le contexte local. Par rapport aux parcelles en plein soleil, nous montrons qu'ils réduisent l'érosion laminaire d'un facteur 2, augmentent la fixation de l'azote (N2) atmosphérique et le pourcentage d'azote recyclé dans le système, réduisant ainsi les besoins en engrais. Ils réduisent aussi la sévérité des maladies foliaires, augmentent la séquestration de carbone, améliorent le microclimat et atténuent substantiellement les effets des changements climatiques. Dans notre étude de cas, aucun effet négatif sur le rendement n'a été enregistré., Eight years of studying coffee ecophysiology and monitoring ecosystem services (ES) in a large coffee farm in Costa Rica revealed several practical recommendations for farmers and policy makers. The cropping system studied within our collaborative observatory (Coffee-Flux) corresponds to a coffee-based agroforestry system (AFS) under the shade of large trees of Erythrina poeppigiana (16 % of canopy cover). A lot of ES and disservices depend on local soil properties (here Andisols), especially erosion/infiltration, water/carbon and nutrient storage capacity. Therefore, for ES assessment, the type of soil is crucial. An adequate density of shade trees (rather low here) reduced the severity of leaf diseases with the prospect of reducing pesticide-fungicide use. A simple inventory of the basal area at collar of the coffee plants allowed estimating the belowground biomass and the average age of the plantation, to judge of its market value and to decide when to replace it. Coffee farms are probably much closer to C neutrality than predicted by the current C-Neutral protocol, which only considers shade trees. More comprehensive assessments, including trees, coffee, litter, soil, and roots in the C balance of the AFS are proposed. Shade trees offer many ES if they are adequately managed in the local context. As compared to full sun conditions, shade trees may (i) reduce laminar erosion by a factor of 2, (ii) increase N2 fixation and the % of N recycled into the system, thus reducing fertilizer requirements, (iii) reduce the severity of leaf diseases, (iv) increase C sequestration, (v) improve the microclimate, and (vi) substantially reduce the effects of climate change. In our case study, no negative effect on coffee yield was found.

Huit ans de travaux de recherche sur les services écosystémiques dans une grande ferme caféière du Costa Rica (observatoire collaboratif Coffee-Flux, en système agroforestier à base de caféiers sous de grands arbres d'Erythrina poeppigiana, surface projetée de couronne de l'ordre de 16 %) ont suggéré plusieurs applications pour les agriculteurs et les décideurs. Il est apparu que de nombreux services écosystémiques dépendaient des propriétés du sol (ici des Andisols), en particulier de l'érosion, de l'infiltration, de la capacité de stockage de l'eau et des éléments nutritifs. Nous confirmons qu'il est essentiel de lier les services hydrologiques et de conservation au type de sol en présence. Une densité adéquate d'arbres d'ombrage (plutôt faible ici) permet de réduire la sévérité des maladies foliaires avec, en perspective, une réduction de l'usage de pesticides-fongicides. Un simple inventaire de la surface basale au collet des caféiers permet d'estimer la biomasse souterraine et la moyenne d'âge d'une plantation de caféiers, ce qui permet d'évaluer sa valeur marchande ou de planifier son remplacement. Le protocole de calcul actuel pour la neutralité carbone des systèmes agroforestiers ne prend en compte que les arbres d'ombrage, pas la culture intercalaire. Dans la réalité, si on inclut les caféiers, on se rapproche très probablement de la neutralité. Des évaluations plus complètes, incluant les arbres, les caféiers, la litière, le sol et les racines dans le bilan en carbone du système agroforestier sont proposées. Les arbres d'ombrage offrent de nombreux servies écosystémiques s'ils sont gérés de manière adéquate dans le contexte local. Par rapport aux parcelles en plein soleil, nous montrons qu'ils réduisent l'érosion laminaire d'un facteur 2, augmentent la fixation de l'azote (N2) atmosphérique et le pourcentage d'azote recyclé dans le système, réduisant ainsi les besoins en engrais. Ils réduisent aussi la sévérité des maladies foliaires, augmentent la séquestration de carbone, améliorent le microclimat et atténuent substantiellement les effets des changements climatiques. Dans notre étude de cas, aucun effet négatif sur le rendement n'a été enregistré.

The adaptation of semi-arid crops to climate changes is theoretically possible in agroforestry systems (AFS), provided that the trees exert little competition, or even increase the land equivalent ratio (LER). However, the measurement of LER requires sole crop plots which are usually not available in AFS. We designed a geostatistical method to estimate the distance of influence of trees on crops and selected sole crop plots at even higher distances, in order to compute LER. We monitored microclimate, net primary productivity (NPP), CO2 and H2O fluxes in a semi-arid agro-silvo-pastoral system (Niakhar, Senegal), dominated by the multipurpose Faidherbia albida (FA) tree. Undercrops were mainly millet and peanut, under annual rotation. Just before harvest, we scanned a ca. 1 ha millet plot under FA with UAV photogrammetry (drone) in RGB, thermal infrared and multispectral bands. At harvest, we collected 12 subplots, distributed either below the crown of FA, or at 2.5 x the crown radius (CR), or at 5 CR. We separated all organs. The whole millet root system (0-200 cm) was sampled also in 2 m trenches. Whole plot harvest allowed extrapolating yield from subplots, through UAV images. Millet yield per unit ground area was about 3 times higher below FA. The geostatistical method indicated that NDVI was not affected by the FA trees at 5 times the crown radius. LER of millet was computed 1.4, confirming the positive effect FA at distances up to 18 m. The “Faidherbia-Flux” observatory is open for collaboration.

“Faidherbia-Flux” , a new long-term highly-instrumented observatory of the critical zone of Sahelian western Africa has been launched early 2018 through international cooperation. We aim at fostering agro-silvo-pastoralism and sustainable intensification research. Namely, ecosystem services, GHG (CO2, H2O, N2O, CH4) fluxes and balances, annual crop (millet, groundnut, cowpea, water melon…) production, the role of livestock, and the effects of management options are targeted. The initiative is hosted at the Niakhar Health-Population-Environment Observatory (> 50 yrs. of past research). We chose a Faidherbia albida tree parkland owing to the attractiveness of this species that is maintained by the people, exhibits reverse phenology, N2 fixation, phreatophytic behavior (hydraulic redistributions?), forage for animals during the dry season, and positive effect on crops, microclimate and infiltration. We assume Faidherbia is a lever for ecological intensification, compatible with other levers, such as mixed crops, livestock, or precision agriculture). To date, “Faidherbia-Flux”1 offers: • Eddy-covariance (EC) measurements (30 m tall tower) since February 2018 for CO2, H2O and energy over the whole ecosystem, with ancillary measurements (soil temperature profile and humidity) (UMR Eco&Sols, LMI IESOL). Drone cover (UMR AGAP, UMR SELMET). • 2 towers (4 m) over millet (UMR Eco&Sols, LMI IESOL) and groundnut+cowpea (GET AMMA-CATCH), recording the 2018 wet season • One field trial in 8 blocks to assess and model the effect of cowpea on millet (ISRA+ UC Davis) • 8 stations for hydrology (infiltration, aquifers, salinization, N transfer) and hydraulic redistributions (sapflow) experiments under construction (UMR Eco&Sols, UMI RESILIENCES) • Minirhizotrons and automatic root scanners under construction (UMR Eco&Sols, LMI IESOL) • Soil gas exchange (CO2, N2O, CH4) experiments under construction Our philosophy is to mutualize efforts into one complex but representative ecosystem and for the long term. Collaborations for science & development are highly welcome. Any scientist, student, institution, NGO… can apply. Complementarity and facilitation will be fostered, overlaps will be minimized. Expected outcomes include high-level trans-disciplinary research, common projects, training, networking, international visibility…

A new long-term flux Observatory was launched (2017) in a semi-arid agro-silvo-pastoral parkland of Senegal. Agroforestry trees are mostly Faidherbia albida, a multi-purpose legume tree, phreatophytic and displaying a reverse phenology, emblematic for agroforestry in dry lands (Roupsard et al., 1999; Sida et al., 2018). Crops are pearl millet, groundnut and cowpea mainly. The soil is sandy and yield is highly limited in water, N and P mainly. The aim of “Faidherbia-Flux” is to assess energy and GHG balances (CO2, H2O, N2O, CH4), together with some major Ecosystem Services (NPP, yield, erosion) at the plant, plot, watershed and landscape scales and separating strata (trees, crops, surface soil, deep soil, aquifer). Observation, experimentation, modelling and remote-sensing are combined, collecting data and calibrating models locally, then upscaling to larger regions. The project will run on the long term through projects, in order to encompass seasonal and inter-annual fluctuations. Faidherbia-flux is a platform where collaborative research is promoted: data are being shared between collaborators and positive interactions are enhanced. The philosophy is to concentrate several investigations on one specific site and for several years, to share a useful common experimental database, to develop modelling, to publish results in highly-ranked scientific journals and share databases internationally (FLUXNET, ICOS, ANAEE, etc.) for meta-analyses purposes. Applied research is also highly encouraged (agronomy, agro-ecological intensification, breeding, etc.). Faidherbia-flux benefits from infrastructure (People-Health-Environment Observatory of Niakhar, 50 years of research), and very good security, ready to welcome complementary scientific investigations and collaborations. The project is wide open to complementary projects, scientists and of course to students.

Eight years of monitoring ecophysiology and ecosystem services (ES) in a large coffee farm of Costa Rica yields a range of practical applications for the farmer and stakeholders, thanks to numerous scientific actors and disciplines contributing to our collaborative observatory (Coffee-Flux). • A lot of ecosystem services depend on the soil properties, such as runoff/infiltration, water and nutrient storage capacity. It is essential to relate hydrological and soil conservation services to the soil type, since this might have even more importance than the crop itself for ES. Regarding the use of fertilizer, we show that some soils may have a large storage capacity, allowing producing coffee at normal yields with just a reduced, or even a minimum amount of fertilizers, for instance when the economic conditions are unfavorable. Also, due to the soil variability within the farm, it is possible to adjust fertilization to micro-local conditions and reduce the total expenses and risks of leaching of N to the environment. VNIRS and MIR are promising broadband tools for screening the variability in soils. Adjusting N fertilizer to the optimum will also considerably reduce the N2O emissions and improve the GHG balance of the farm. • Pesticides-fongicides: we show that an adequate amount of shade trees allows reducing the severity of the whole complex of leaf diseases. This also should reduce expenses and impacts on the ecosystem. • Roots: a simple survey of basal area at collar allows estimating the belowground biomass and the average age of a plantation, to judge of its market value and to decide when to replace it. • Also starch plays a key role in the trophic equilibrium between the perennial parts of the coffee plant (aerial stump, belowground stump, coarse roots) and its ephemeral parts (resprout, leaves, fruits, fine roots). Coffee plants accumulate starch in the stumps by the end of the life of their resprout, as a strategy for survival. Breeding plants with less starch build-up capacity would probably allow increasing the fraction of productive years during the lifespan of the resprouts. • Coffee farms are probably much closer to C neutrality than currently admitted using the C-Neutrality protocol. We stress the prevailing role of coffee plants + litter + soil in the ecosystem C balance. If those are excluded from the calculations as done so far, coffee farms are GHG sources, by definition. We argue that either full assessments (as proposed here, at the ecosystem level, including trees, coffee, litter, soil and roots) or consensus on “sequestration factors” (the counterpart of emission factors) would allow performing a more realistic assessment of the GHG balance. • Finally, we bring new data confirming that shade trees offer numerous ecosystem services, when adequately managed for the local context. As compared to full sun conditions, they may (i) reduce laminar erosion by a factor of ca. 2, (ii) increase the atmospheric N2 fixation and the % of N recycled into the system, thus reducing the fertilizer requirements, (iii) reduce the severity of the leaf disease complex, (iv) increase C sequestration, (v) improve the microclimate, and (vi) be a large part of the solution to face climate changes. All this is possibly without negative effects on profitability or yield, if managed properly. In our particular case-study, we encount.

Les plantations d'arbres tropicaux sont en expansion rapide pour satisfaire la demande croissante en bois et produits non ligneux. Les recherches actuelles visent à améliorer le rôle d'atténuation du changement climatique de ces plantations ainsi que leur adaptation, en associant écophysiologie, génétique et génomique fonctionnelle. L'effet positif de l'augmentation du gaz carbonique atmosphérique sur la photosynthèse pourrait induire une augmentation de la production de biomasse, mais les besoins accrus en eau et en nutriments devront être satisfaits pour que cet effet soit durable. Des plantations plurispécifiques bénéficiant d'interactions positives entre espèces pourraient contribuer à maintenir la production des plantations d'arbres tropicaux dans un contexte d'augmentation des stress biotiques et abiotiques.