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Among agroecological practices, the diversification of cropping systems with the introduction of trees is an adaptation solution to mitigate climate change (Bradshaw et al., 2004). Those combining trees and crops present functionally varied root systems that explore different soil depths. Moreover, while the production of aboveground biomass is recognized as one of the main levers to foster C storage in soils, the fate of root biomass has been less studied, especially in deep horizons. Deep roots from annual and perennial plants play a central role in the sustainable C sequestration through their turnover (Pradier et al., 2017), their exudation, and could become a determining criterion for plant selection. Indeed, root decomposition slows down with soil depth (Pries et al. 2018), and thus promote soil C storage.Our study aims to assess the contribution of roots to soil C sequestration, at different soil depth, under annual crops and trees in a sub-sahelian agroforestry ecosystem. The experiment was carried out in Sob village (Niakhar district, Senegal) in order to measure the root decomposition of two annual crops (pearl millet and cowpea) under the influence or not of a Legume tree (Faidherbia albida) and at different soil depth, down to 2m. Fine root decomposition of Faidherbia albida was also measured.Two pits of 2*2*2m were dug, one located at 1.5m from a Faidherbia albida tree of more than 80 year old (under the crown) and the second pit was located at 30m from the same tree, supposed with no tree influence. On three faces out of four of each pit, soil samples were collected at several depths and were analyzed (texture, C, N and P content, pH, bulk density). Soil humidity was monitored through TDR sensors from topsoil to 1.6m soil depth. The above- and belowground biomass of the annual crop (pear millet the year of sampling) was measured over the surface of each pit (4m²) including 4 plants. Pearl millet, Faidherbia and cowpea roots (from a juxtaposed field) were collected, washed and separated as a function of their diameter. Fine roots (Ø

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.

Content: Among agroecological practices, the diversification of cropping systems with the introduction of trees is an adaptation solution to mitigate climate change (Bradshaw et al., 2004). Those combining trees and crops present functionally varied root systems that explore different soil depths. Moreover, while the production of aboveground biomass is recognized as one of the main levers to foster C storage in soils, the fate of root biomass has been less studied, especially in deep horizons. Deep roots from annual and perennial plants play a central role in the sustainable C sequestration through their turnover (Pradier et al., 2017), their exudation, and could become a determining criterion for plant selection. Indeed, root decomposition slows down with soil depth (Pries et al. 2018), and thus promote soil C storage.Our study aims to assess the contribution of roots to soil C sequestration, at different soil depth, under annual crops and trees in a sub-sahelian agroforestry ecosystem. The experiment was carried out in Sob village (Niakhar district, Senegal) in order to measure the root decomposition of two annual crops (pearl millet and cowpea) under the influence or not of a Legume tree (Faidherbia albida) and at different soil depth, down to 180 cm. Fine root decomposition of Faidherbia albida was also measured.Two pits of 2 × 2 × 2 m were dug, one located at 1.5 m from a Faidherbia albida tree of more than 80 year old (under the crown) and the second pit was located at 30 m from the same tree, supposed with no tree influence. On three faces out of four of each pit, soil samples were collected at several depths and were analyzed (texture, C, N and P content, pH, bulk density). Soil humidity was monitored through TDR sensors at different depths. The above- and belowground biomass of the annual crop (pear millet the year of sampling) was measured over the surface of each pit (4 m²) including 4 plants. Pearl millet, Faidherbia and cowpea roots (from a juxtaposed field) were collected, washed and separated as a function of their diameter. Fine roots (Ø

International audience; Greenhouse gas (CO2, N2O and CH4) exchange measurements between soil and atmosphere are important data when studying agrosystem functioning. These data can be measured on high temporal resolution with automatic chambers. However, automated chamber systems are expensive which limits the number of measuring points on a same site. Besides, researchers are restrained to integrate and understand the spatial variability of the soil metabolic activity and more generally biogeochemistry cycles that are associated to. For this study, we propose a construction plan for a self-made multiplexed system of automated chambers. We chose a system with an horizontal closure to minimise effects due to overpressure during closing events, and to allow the system to be installed under low branches. Here we present some results of leakage tests and at field functioning during several months. A particular attention has been brought to the material cost, to the electric consumption as well as the implementation simplicity. Technical information about the conception, construction and the use of these chambers and output data analyses are detailed in this paper with the drawings, pilot programming and codes for the data analysis.; Les mesures d’échanges des principaux gaz à effet de serre (CO2, N2O et CH4) entre le sol et l’atmosphère sont des données importantes dans l’étude du fonctionnement des agrosystèmes. Ces données peuvent être mesurées à haute résolution temporelle grâce à des chambres de mesure automatiques qui constituent actuellement la technique de référence. Les systèmes automatisés commerciaux sont coûteux, ce qui limite le nombre de points de mesure sur un même site, et donc, la capacité des équipes de recherche à mieux intégrer et comprendre la variabilité spatiale de l’activité métabolique du sol et plus généralement les cycles biogéochimiques qui lui sont associés. Dans cette étude, nous proposons les plans pour réaliser soi-même un système multiplexé original de chambres de mesure automatisées. Nous avons opté ici pour une fermeture horizontale, afin de minimiser les effets liés à la surpression lors de la fermeture et/ou passer sous des branches basses. Des résultats de tests de fuite et de fonctionnement en plein champ pendant plusieurs mois sont présentés. Une attention particulière a été apportée au coût du matériel, à la consommation énergétique ainsi qu’à la simplicité de mise en oeuvre. Les informations techniques relatives à la conception, à la fabrication, à l’utilisation de ces chambres et à l’analyse des données de sortie sont détaillées dans cet article, avec les plans, les programmes de pilotage et les codes pour l’analyse de données.

Les mesures d'échanges des principaux gaz à effet de serre (CO2, N2Oet CH4) entre le sol et l'atmosphère sont des données importantes dans l'étude du fonctionnement des agrosystèmes. Ces données peuvent être mesurées à haute résolution temporelle grâce à des chambres de mesure automatiques qui constituent actuellement la technique de référence. Les systèmes automatisés commerciaux sont coûteux, ce qui limite le nombre de points de mesure sur un même site, et donc, la capacité des équipes de recherche à mieux intégrer et comprendre la variabilité spatiale de l'activité métabolique du sol et plus généralement les cycles biogéochimiques qui lui sont associés. Dans cette étude, nous proposons les plans pour réaliser soi-même un système multiplexé original de chambres de mesure automatisées. Nous avons opté ici pour une fermeture horizontale, afin de minimiser les effets liés à la surpression lors de la fermeture et/ou passer sous des branches basses. Des résultats de tests de fuite et de fonctionnement en plein champ pendant plusieurs mois sont présentés. Une attention particulière a été apportée au coût du matériel, à la consommation énergétique ainsi qu'à la simplicité de mise en oeuvre. Les informations techniques relatives à la conception, à la fabrication, à l'utilisation de ces chambres et à l'analyse des données de sortie sont détaillées dans cet article, avec les plans, les programmes de pilotage et les codes pour l'analyse de données.

Arbuscular mycorrhizal (AM) fungi are crucial for plant nutrition and the sustainability of agroforestery systems. However, the contribution of each agroforestry component (i.e. trees, under-tree herbaceous vegetation -UtHV- and crops) in the establishment and maintenance of AM communities is poorly documented particularly in temperate areas. This study investigates the spatio-temporal dynamics of AM fungi colonizing roots of the three agroforestry components in southwest France. Standing fine root length density and production, AM activity (colonization and extraradical hyphal growth) and diversity of walnut trees, UtHV and soft wheat were assessed over one year in two agroforestry systems at different distances from the perennial tree-UtHV alley. Compared to UtHV, trees showed a higher ability to colonize superficial layers far into the cultivated alleys due to their wider root system in summer. However, due to higher root densities and well established AM fungi observed throughout all the year, UtHV appeared to be more ecologically relevant to maintain an active source of AM inoculum for newly developing crop roots in winter. High degree of root proximity and similarity of AM fungal communities among the three agroforestry components provide new perspectives in deciphering the significance of common mycorrhizal networks in plant to plant interactions.

International audience; 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.

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.

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.

Agroforestry systems (AFS) can provide many services, among which sequestering atmospheric carbon (C) dioxide (CO2) into both tree biomass and soil organic matter for mitigating climate warming. Such high performances were documented in several studies, but data are still scarse for covering the broad range of agrosystems – climate combinations. More particularly, data of the different C stocks and fluxes among the different components of the AFS needs to be documented for robust estimates of C sink strength. This study aims at providing values of C stocks and fluxes of a black locust (Robinia pseudoacacia L.)-based agroforestry site in Mauguio, Southern France. The different compartments of the AFS were investigated: the black locust rows, the herbaceous strip planted of various grassland species along the trees and the intercropping, constituted by a rotation cereals/legumes. The crop rotations comprised durum wheat, barley, chickpea and pea, but we presented the data for the barley planting year in 2021. A forest plantation and a pure crop planting systems were also studied as control modalities. The three planting systems were repeated in three independent blocks. Aboveground tree biomass growth was estimated for the agroforestry and the forestry plots from allometric models. Black locust litter fall was quantified also in the agroforestry and forestry plots. For each planting systems, root biomasses, root C contents and root growth were estimated . Aboveground herbaceous biomasses and C contents were also measured in 1m2 squared plots at different seasons. Soil microbial biomass and soil CO2 efflux were measured in all components and planting systems. All data currently under processing will be normalized per area unit. The effect of the planting system was assessed in order to determine the added value of the agroforestry system with respect to the pure planting systems.