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Context and background Throughout history, the severity of coastal impacts has varied depending on social and environmental factors. Human activities in general have caused large-scale environmental and morphological changes, and our study area is not outside this context. Goal and Objectives: This study aims to reveal the evolution of urban fabric of the city of Echatt and sidimbarek and their degree of influence on the state of dune cordon last 37 years. Methodology: The methodology followed during this study is based on satellite and topographic data as well as on measurements and observations made in the field. In order to study the evolution of urban fabric of the study area. The approach adopted is based on a study of several satellite images and google Earth pro images at different dates in order to determine the extent of changes that occurred between 1984 and 2021. Results: The results show an increase in coastal urbanization at varying rates amounting to 11.92 ha/year between (1984-2000), 4.95 ha/year between (2000; 2010) and 9. 92 ha/year between (2010,2021); and landscape changes that have developed at different rates over time due to the exploitation of the dune cordon of the city of echatt and sidimbarek in an irrational way that can lead to a total removal of vegetation cover, because according to the results obtained, more than half of the vegetation cover of the coastal dunes has been removed in 37 years Thematic maps and results obtained at different periods show that the forest landscape has gradually converted into dry land despite the entry into force of the Algerian Coastal Law 02-02 on the protection and enhancement of the coast, which aimed at the protection of the coast and sustainable use of its resources., African Journal on Land Policy and Geospatial Sciences, Vol 6, No 2: March 2023

Located in the south of Senegal, the Upper-Casamance (present-day Kolda region) has a strong vegetation dynamic mainly due to the clearing of land for agricultural needs, bush fires, population growth and uncontrolled logging. In such a situation, mapping and quantification of changes in vegetation cover become relevant for a more rational and sustainable management of plant resources, but also for the achievement of the Sustainable Development Goals. This study aims to detect the degradation and regeneration of vegetation cover during the last two decades in Upper-Casamance. It is based on an analysis of the trends of MODIS NDVI images time series acquired over the period 2000-2018, on a land cover and use changes (LULCC) maps established from Landsat images (ETM+ 1999 and OLI 2018), and a joint analysis of NDVIand LULCC trends. Data processing is based on the calculation of the Kendall correlation (τ) and the p significance test at the 10% threshold, and on a multistage unsupervised classification, respectively. The study shows significant changes in land cover and land use, including conversion from forest to savannah (13.5%), and from savannah to crop and habitat areas (7.9%). Significant negative trends in NDVI (related to forest-savanna conversion and forest-cropping and habitat areas) are observed in 2.1% of the study area and indicate vegetation degradation especially along the border with Gambia, on the Pata-Ndorna axis, in the centre of the study area, and around Medina Gounass. On the other hand, significant positive trends on 1.8% of the study area are evidence of regeneration in the south and are linked to the conversion ofcultivated areas into savanna and forest. Joint analysis of NDVI and LULCC trends indicated significant degradation in south of Kerewane and Niaming, on the Ndorna-Pata axis, around Medina Gounass, and towards Saré Coly; and significant regeneration at the northeast border, north of Mampatim, to the south towards Bagadadji and Medina El Hadji, and between Linkering-Paroumba. This analysis also revealed that the two sources of data (NDVI et Landsat) are spatially consistent and that most of the trends in vegetation productivity are explained by changes in land use and not by climate., Cette étude vise à détecter et cartographier la dégradation et la régénération de la couverture végétale durant ces deux dernières décennies en Haute-Casamance, située dans le sud du Sénégal. Elle s'appuie sur l'analyse des tendances de séries temporelles d'images MODIS NDVI acquises sur la période 2000-2018, sur la cartographie des changements d'occupation et d'utilisation des sols (LULCC) faite à partir d'images Landsat (ETM+ 1999 et OLI 2018), et sur une analyse conjointe des tendances de NDVI et LULCC. L'étude a révélé d'importants changements en termes d'occupation et d'utilisation des sols, notamment la conversion de la forêt à la savane (13,5 %), et de la savane aux zones de culture et d'habitat (7,9 %). Des tendances négatives significatives (p

Ground cover management (GCM) is an important agricultural practice used to reduce weed growth, erosion and runoff, and improve soil fertility. In the present study, an approach to account for GCM is proposed in the modeling of pesticide emissions to evaluate the environmental sustainability of agricultural practices. As a starting point, we include a cover crop compartment in the mass balance of calculating initial (within minutes after application) and secondary (including additional processes) pesticide emission fractions. The following parameters were considered: (i) cover crop occupation between the rows of main field crops, (ii) cover crop canopy density, and (iii) cover crop family. Two modalities of cover crop occupation and cover crop canopy density were tested for two crop growth stages, using scenarios without cover crops as control. From that, emission fractions and related ecotoxicity impacts were estimated for pesticides applied to tomato production in Martinique (French West Indies) and to grapevine cultivation in the Loire Valley (France). Our results demonstrate that, on average, the presence of a cover crop reduced the pesticide emission fraction reaching field soil by a factor of 3 compared with bare soil, independently of field crop and its growth stage, and cover crop occupation and density. When considering cover exported from the field, ecotoxicity impacts were reduced by approximately 65% and 90%, compared with bare soil for grapevine and tomato, respectively, regardless of the emission distribution used. Because additional processes may influence emission distributions under GCM, such as runoff, leaching, or preferential flow, further research is required to incorporate these processes consistently in our proposed GCM approach. Considering GCM in pesticide emission modeling highlights the potential of soil cover to reduce pesticide emissions to field soil and related freshwater ecotoxicity. Furthermore, the consideration of GCM as common farming practice allows the modeling of pesticide emissions in intercropping systems. Integr Environ Assess Manag 2021;00:1–15. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

International audience; Over the past decade, several global maps of above-ground biomass (AGB) have been produced, but they exhibit significant differences that reduce their value for climate and carbon cycle modelling, and also for national estimates of forest carbon stocks and their changes. The number of such maps is anticipated to increase because of new satellite missions dedicated to measuring AGB. Objective and consistent methods to estimate the accuracy and uncertainty of AGB maps are therefore urgently needed. This paper develops and demonstrates a framework aimed at achieving this. The framework provides a means to compare AGB maps with AGB estimates from a global collection of National Forest Inventories and research plots that accounts for the uncertainty of plot AGB errors. This uncertainty depends strongly on plot size, and is dominated by the combined errors from tree measurements and allometric models (inter-quartile range of their standard deviation (SD) = 30–151 Mg ha−1). Estimates of sampling errors are also important, especially in the most common case where plots are smaller than map pixels (SD = 16–44 Mg ha−1). Plot uncertainty estimates are used to calculate the minimum-variance linear unbiased estimates of the mean forest AGB when averaged to 0.1∘. These are used to assess four AGB maps: Baccini (2000), GEOCARBON (2008), GlobBiomass (2010) and CCI Biomass (2017). Map bias, estimated using the differences between the plot and 0.1∘ map averages, is modelled using random forest regression driven by variables shown to affect the map estimates. The bias model is particularly sensitive to the map estimate of AGB and tree cover, and exhibits strong regional biases. Variograms indicate that AGB map errors have map-specific spatial correlation up to a range of 50–104 km, which increases the variance of spatially aggregated AGB map estimates compared to when pixel errors are independent. After bias adjustment, total pantropical AGB and its associated SD are derived for the four map epochs. This total becomes closer to the value estimated by the Forest Resources Assessment after every epoch and shows a similar decrease. The framework is applicable to both local and global-scale analysis, and is available at https://github.com/arnanaraza/PlotToMap. Our study therefore constitutes a major step towards improved AGB map validation and improvement.

Forest landscape restoration (FLR) commitments have been established in the past years to restore over 200 million hectares, as part of the global Bonn Challenge goal, mostly through the implementation of several different restorative practices in degraded lands, ranging from commercial tree monocultures to restoration plantings. The potential of such contrasting restorative practices to support biodiversity conservation and ecosystem services provision vary over space and time, making the monitoring of FLR programs an emerging challenge. Remote sensing techniques, together with innovative technologies for data acquisition, treatment, and analysis have proven to be strategic for planning and monitoring FLR, yet there are still important unresolved questions. Here, we evaluated the potential of multispectral orbital images of the high spatial (5 m) and spectral (12 bands) resolution VENμS microsatellite, joint project of the Israeli Space Agency and CNES, to classify the spectral behavior and diversity of six tree cover classes (savanna woodlands, old- and second-growth semi-deciduous forests, young restoration plantings, and eucalyptus and pine tree monocultures) commonly found in FLR programs in tropical regions. We assessed how these tree cover classes located in a study landscape in southeastern Brazil differ according to their spectral response (winter and summer bands, and vegetation indices), canopy variability (textural features), seasonal behavior (delta layers - difference between summer and winter vegetation indexes), and spectral diversity, and used these attributes as variables to the model. We used the Random Forest algorithm to generate the models and evaluate how the tree cover classes differ in the classification and how the variables supported the model. We achieved high values of global accuracy (91.9%) and “F1 score” (above 0.8) for all tree cover classes, in which second-growth forest presented the lowest accuracy. The textural layers, delta layers, and the spectral diversity layers were the most important attributes to discriminate among tree cover classes. We demonstrate here the potential of using VENμS or similar sensor images together with different image processing and machine learning algorithms to monitor FLR programs, allowing further remote sensing approaches and in-deep field assessments to advance evaluation of FLR benefits for nature and people. We demonstrated how the fusion of all these types of data and innovative approaches to data processing, can result in novel ways to assess restoration performance and open new avenues to upscale monitoring, bridging the gap between FLR expectations and achieved goals.

Datos disponibles en https://github.com/fmsabatini/sPlotOpen_Code, EU H2020 project BACI, Grant No. 640176 (...), Sabatini, F.M., Lenoir, J., Hattab, T., Arnst, E.A., Chytrý, M., Dengler, J., De Ruffray, P., Hennekens, S.M., Jandt, U., Jansen, F., Jiménez-Alfaro, B., Kattge, J., Levesley, A., Pillar, V.D., Purschke, O., Sandel, B., Sultana, F., Aavik, T., Aćić, S., Acosta, A.T.R., Agrillo, E., Alvarez, M., Apostolova, I., Arfin Khan, M.A.S., Arroyo, L., Attorre, F., Aubin, I., Banerjee, A., Bauters, M., Bergeron, Y., Bergmeier, E., Biurrun, I., Bjorkman, A.D., Bonari, G., Bondareva, V., Brunet, J., Čarni, A., Casella, L., Cayuela, L., Černý, T., Chepinoga, V., Csiky, J., Ćušterevska, R., De Bie, E., de Gasper, A.L., De Sanctis, M., Dimopoulos, P., Dolezal, J., Dziuba, T., El-Sheikh, M.A.E.-R.M., Enquist, B., Ewald, J., Fazayeli, F., Field, R., Finckh, M., Gachet, S., Galán-de-Mera, A., Garbolino, E., Gholizadeh, H., Giorgis, M., Golub, V., Alsos, I.G., Grytnes, J.-A., Guerin, G.R., Gutiérrez, A.G., Haider, S., Hatim, M.Z., Hérault, B., Hinojos Mendoza, G., Hölzel, N., Homeier, J., Hubau, W., Indreica, A., Janssen, J.A.M., Jedrzejek, B., Jentsch, A., Jürgens, N., Kącki, Z., Kapfer, J., Karger, D.N., Kavgacı, A., Kearsley, E., Kessler, M., Khanina, L., Killeen, T., Korolyuk, A., Kreft, H., Kühl, H.S., Kuzemko, A., Landucci, F., Lengyel, A., Lens, F., Lingner, D.V., Liu, H., Lysenko, T., Mahecha, M.D., Marcenò, C., Martynenko, V., Moeslund, J.E., Monteagudo Mendoza, A., Mucina, L., Müller, J.V., Munzinger, J., Naqinezhad, A., Noroozi, J., Nowak, A., Onyshchenko, V., Overbeck, G.E., Pärtel, M., Pauchard, A., Peet, R.K., Peñuelas, J., Pérez-Haase, A., Peterka, T., Petřík, P., Peyre, G., Phillips, O.L., Prokhorov, V., Rašomavičius, V., Revermann, R., Rivas-Torres, G., Rodwell, J.S., Ruprecht, E., Rūsiņa, S., Samimi, C., Schmidt, M., Schrodt, F., Shan, H., Shirokikh, P., Šibík, J., Šilc, U., Sklenář, P., Škvorc, Ž., Sparrow, B., Sperandii, M.G., Stančić, Z., Svenning, J.-C., Tang, Z., Tang, C.Q., Tsiripidis, I., Vanselow, K.A., Vásquez Martínez, R., Vassilev, K., Vélez-Martin, E., Venanzoni, R., Vibrans, A.C., Violle, C., Virtanen, R., von Wehrden, H., Wagner, V., Walker, D.A., Waller, D.M., Wang, H.-F., Wesche, K., Whitfeld, T.J.S., Willner, W., Wiser, S.K., Wohlgemuth, T., Yamalov, S., Zobel, M., Bruelheide, H.

In The Gambia, the vegetation cover has undergone significant changes over the past two decades. To assist policy decision-making, this study seeks to detect trends in changes over the past two decades using a time series of NDVI MODIS images. The methodological approach is based on the calculation of the correlation of Kendall (τ) associated with the p-significance test at the 10 % threshold. The results showed a trend of increasing vegetation productivity during the decade 2000-2009 (98.37% of the study area) in almost all administrative regions. This trend is more significant along the river. In contrast, during the decade 2010-2019, it was noted overall significant downward trend in productivity (44.01% of The Gambia) in all administrative regions except West Coast Region and Banjul, however not significant. The result showed that, over the whole period (2000-2019), 61.86% of the national territory was characterized by a positive trend and 38.14% by a negative trend; and that the significant positive trend percentage is 10%, the significant negative trend percentage is 4%. Significant positive trends are observed much more along the river and central of the Central River Region; significant negative trends are observed mainly in the western part of West Coast Region and Banjul, at the eastern end of the North Bank Region and in the Upper River Region. En Gambie, la couverture végétale connaît d’importantes modifications depuis les deux dernières décennies. Pour aider les politiques dans leur prise de décision, cette étude cherche à détecter les tendances des changements au cours de cette période à l’aide d’une série temporelle d’images MODIS NDVI. L’approche méthodologique est basée sur le calcul de la corrélation de Kendall (τ) associé au test de significativité de p au seuil de 10 %. Les résultats ont montré une tendance à l’augmentation de la productivité de la végétation durant la décennie 2000-2009 (98,37 % de la zone d’étude) dans quasiment toutes les régions administratives. Cette tendance est plus significative le long du fleuve. Par contre, durant la décennie 2010-2019, on a noté globalement d’importantes tendances à la baisse de la productivité (44,01 % de la Gambie) dans toutes les régions administratives excepté la West Coast Region et Banjul, toutefois non significatives. à l’échelle de toute la période étudiée (2000-2019), 61,86 % du territoire national est marqué par une tendance positive et 38,14 % par une tendance négative. Le pourcentage de tendance positive significative est de 10 %, celui significativement négatif de 4 %. Les tendances positives significatives sont le plus souvent observées le long du fleuve et dans le centre de la Central River Region, celles significativement négatives principalement dans la partie ouest de la West Coast Region et de Banjul, à l’extrémité Est de la North Bank Region et de la Upper River Region.

Cette étude analyse l’évolution spatio-temporelle de la couverture végétale dans les forêts classées et aménagées de la Haute-Casamance entre 1965 et 2018. Elle a porté sur six périmètres forestiers qui reflètent l’évolution du couvert végétal en Haute-Casamance, dont trois classés (Pata, Kantora et Dabo) et trois aménagés (Saré Bidji, Medina Salam Dingha et Bonconto). L’approche utilisée s’appuie sur une interprétation visuelle, à partir d’imageries Corona de 1965 et Sentinel 2 de 2018, des tendances de l’occupation des sols et des modifications de la végétation. Les résultats ont indiqué une grande variabilité du couvert végétal selon le domaine, la position géographique de ces périmètres dans la zone d’étude, et la pression anthropique. À l’exception de la forêt classée de Dabo située dans le sud, les forêts du domaine classé (Pata et Kantora qui sont situées dans le nord) ont connu une conversion plus importante du couvert végétal. Elles sont également plus affectées par les actions anthropiques, que les forêts du domaine aménagé. De même, la forêt aménagée de Médina Salam Dingha, située un peu plus au nord, a connu une conversion plus importante de la végétation que celles situées un peu plus dans le sud. D’ailleurs, dans la forêt aménagée de Bonconto, la tendance est à la régénération de la couverture végétale. Ces différentes tendances de la végétation amènent à poser la problématique du statut actuel de certaines forêts classées et de l’importance de l’aménagement forestière., African Journal on Land Policy and Geospatial Sciences, Vol 4, No 2: March 2021

Altres ajuts: these projects are co-funded by European regional development fund (ERDF / FEDER, 2007-2013). Recent studies suggest that carbon (C) is stored in the topsoil of pastures established after deforestation. However, little is known about the long-term capacity of tropical pastures to sequester C in different soil layers after deforestation. Deep soil layers are generally not taken into consideration or are underestimated when C storage is calculated. Here we show that in French Guiana, the C stored in the deep soil layers contributes significantly to C stocks down to a depth of 100 cm and that C is sequestered in recalcitrant soil organic matter in the soil below a depth of 20 cm. The contribution of the 50-100 cm soil layer increased from 22 to 31 % with the age of the pasture. We show that long-term C sequestration in C4 tropical pastures is linked to the development of C3 species (legumes and shrubs), which increase both inputs of N into the ecosystem and the C:N ratio of soil organic matter. The deep soil under old pastures contained more C3 carbon than the native forest. If C sequestration in the deep soil is taken into account, our results suggest that the soil C stock in pastures in Amazonia would be higher with sustainable pasture management, in particular by promoting the development of legumes already in place and by introducing new species.

Biological control can be an effective conservation strategy to manage invasive species when other conventional methods cannot be implemented. Estimating the benefits of biological control for the conservation of native biodiversity remains a challenging task. Following the introduction of a defoliating sawfly, Cibdela janthina, for biological control of invasive giant bramble, Rubus alceifolius, on Reunion Island (Mascarene Archipelago), we monitored the consequent change in R. alceifolius cover as well as species richness and cover of non-native species and native species within a set of patches along an altitudinal gradient in the National Park of Reunion Island. There was an increase in native species richness and cover together with a decrease in R. alceifolius cover, showing that biological control positively impacted the native plant communities. The effectiveness of C. janthina was influenced by the altitudinal range, the surface area of the patches and the location of each patch, i.e forest edge or forest matrix. We discuss the extent to which the use of biological control within an integrated approach can optimize benefits for biodiversity conservation in the short to medium term by selecting complementary and standardised protocols.

Le recours aux intrants de synthèse dans les monocultures intensives entraine une pollution et une dégradation des régulations écologiques de ces systèmes. Dans les systèmes de production bananiers des Antilles françaises, la mise en place d'une jachère après les cycles de production permet d'établir des communautés végétales diversifiées, capables de restaurer ces fonctions écologiques et de fournir des services écosystémiques à l'agriculteur. L'installation de ces communautés peut être orientée par des pratiques comme le semis d'une plante de services (PdS) et un travail du sol avant le semis des PdS. Nous faisons l'hypothèse que les communautés qui vont émerger, associant PdS et espèces spontanées aptes à pousser avec elles, pourront fournir des services d'amélioration de la fertilité azotée du sol, de sa structure, et de contrôle de spontanées dont la gestion s'avère difficile. L'objectif de cette thèse est d'étudier les effets de l'implantation d'une PdS et du travail du sol avant semis de la PdS sur la communauté végétale et les services rendus par cette communauté diversifiée. Il a été décliné en trois questions de recherche: 1) En quoi les communautés associant PdS et spontanées mises en place sous l'influence de deux filtres (PdS et travail du sol) diffèrent au niveau de leur densité, richesse spécifique et composition ? 2) Comment le développement et la composition de la communauté de spontanées et le développement de la population de PdS sont-ils orientés par les compétitions entre PdS et spontanées? 3) Peut-on mettre en évidence l'impact de la communauté végétale sur les services d'amélioration de la fertilité azotée du sol et de sa structure par des relations entre structure fonctionnelle de la communauté et indicateurs de services ? Pour cela, une approche fonctionnelle basée sur la description des traits des espèces a été adoptée. Le cadre effet-réponse de Lavorel & Garnier (2002) a ainsi été adapté au cas d'étude pour comprendre la mise en place de la communauté végétale sous l'action des filtres imposés à cette communauté, puis l'impact de cette communauté sur les services ciblés. Un essai au champ a été conduit sur un an, selon un dispositif en split-plot combinant deux modalités de travail du sol avant semis et trois PdS ainsi qu'un témoin de végétation spontanée. Les compositions des communautés ont été suivies chaque mois. Les traits associés aux compétitions entre espèces ainsi qu'à l'amélioration de la fertilité azotée du sol et de sa structure ont été mesurés sur les 12 espèces les plus fréquentes dans l'essai. Des indicateurs des services ciblés ont été mesurés en début d'expérimentation, puis après 7 et 12 mois. Les résultats montrent la mise en place de communautés aux densités, richesses spécifiques et compositions différentes entre traitements. Des relations de compétitions entre espèces et entre PdS et spontanées ont été partiellement démontrées sur la base de l'observation de traits fonctionnels liés à l'acquisition des ressources lumineuses et de la structure fonctionnelle des communautés. Une relation nette a été établie entre biomasse des PdS et biomasse des spontanées. Enfin, des relations entre marqueurs fonctionnels des communautés et indicateurs des services ont été établies. Certaines communautés ont permis d'améliorer la fertilité azotée du sol ou sa structure, mais ont eu des difficultés à contrôler les spontanées dont la gestion est difficile pour l'agriculteur. De plus, amélioration de la fertilité azotée et structure du sol ont été reliées à des caractéristiques différentes des couverts que nous n'avons pu observer dans une même communauté, suggérant un compromis à trouver entre ces deux services. L'originalité scientifique de cette thèse a résidé dans l'application du cadre effet-réponse de Lavorel & Garnier (2002) au cas de la jachère en bananeraie. Les résultats pourront aider au choix des espèces et couverts à insérer dans les systèmes de culture bananiers diversifiés.

In Montane Southeast Asia, deforestation and unsuitable combinations of crops and agricultural practices degrade soils at an unprecedented rate. Typically, smallholder farmers gain income from "available" land by replacing fallow or secondary forest by perennial crops. We aimed to understand how these practices increase or reduce soil erosion. Ten land uses were monitored in Northern Laos during the 2015 monsoon, using local farmers' fields. Experiments included plots of the conventional system(food crops and fallow), and land uses corresponding to new market opportunities (e.g. commercial tree plantations). Land uses were characterized by measuring plant cover and plant mean height per vegetation layer. Recorded meteorological variables included rainfall intensity, throughfall amount, throughfall kinetic energy (TKE), and raindrop size. Runoff coefficient, soil loss, and the percentage areas of soil surface types (free aggregates and gravel; crusts; macro-faunal, vegetal and pedestal features; plant litter) were derived from observations and measurements in 1-m(2) micro-plots. Relationships between these variables were explored with multiple regression analyses. Our results indicate that TKE induces soil crusting and soil loss. By reducing rainfall infiltration, crusted area enhances runoff, which removes and transports soil particles detached by splash over non-crusted areas. TKE is lower under land uses reducing the velocity of raindrops and/or preventing an increase in their size. Optimal vegetation structures combine minimum height of the lowest layer (to reduce drop velocity at ground level) and maximum coverage (to intercept the largest amount of rainfall), as exemplified by broom grass (Thysanolaena latifolia). In contrast, high canopies with large leaves will increase TKE by enlarging raindrops, as exemplified by teak trees (Tectona grandis), unless a protective understorey exists under the trees. Policies that ban the burning of multi-layered vegetation structure under tree plantations should be enforced. Shade-tolerant shrubs and grasses with potential economic return could be promoted as understorey.

© 2017 Elsevier B.V. Deforestation and forest degradation cause the deterioration of resources and ecosystem services. However, there are still no operational indicators to measure forest status, especially for forest degradation. In the present study, we analysed the thermal response number (TRN, calculated by daily total net radiation divided by daily temperature range) of 163 sites including mature forest, disturbed forest, planted forest, shrubland, grassland, savanna vegetation and cropland. TRN generally increased with latitude, however the regression of TRN against latitude differed among vegetation types. Mature forests are superior as thermal buffers, and had significantly higher TRN than disturbed and planted forests. There was a clear boundary between TRN of forest and non-forest vegetation (i.e. grassland and savanna) with the exception of shrubland, whose TRN overlapped with that of forest vegetation. We propose to use the TRN of local mature forest as the optimal TRN (TRNopt). A forest with lower than 75% of TRNopt was identified as subjected to significant disturbance, and forests with 66% of TRNopt was the threshold for deforestation within the absolute latitude from 30° to 55°. Our results emphasized the irreplaceable thermal buffer capacity of mature forest. TRN can be used for early warning of deforestation and degradation risk. It is therefore a valuable tool in the effort to protect forests and prevent deforestation.

Terrestrial evapotranspiration (ET) for each plant functional type (PFT) is a key variable for linking the energy, water and carbon cycles of the atmosphere, hydrosphere and biosphere. Process-based algorithms have been widely used to estimate global terrestrial ET, yet each ET individual algorithm has exhibited large uncertainties. In this study, the support vector machine (SVM) method was introduced to improve global terrestrial ET estimation by integrating three process-based ET algorithms: MOD16, PT-JPL and SEMI-PM. At 200 FLUXNET flux tower sites, we evaluated the performance of the SVM method and others, including the Bayesian model averaging (BMA) method and the general regression neural networks (GRNNs) method together with three process-based ET algorithms. We found that the SVM method was superior to all other methods we evaluated. The validation results showed that compared with the individual algorithms, the SVM method driven by tower-specific (Modern Era Retrospective Analysis for Research and Applications, MERRA) meteorological data reduced the root mean square error (RMSE) by approximately 0.20 (0.15) mm/day for most forest sites and 0.30 (0.20) mm/day for most crop and grass sites and improved the squared correlation coefficient (R2) by approximately 0.10 (0.08) (95% confidence) for most flux tower sites. The water balance of basins and the global terrestrial ET calculation analysis also demonstrated that the regional and global estimates of the SVM-merged ET were reliable. The SVM method provides a powerful tool for improving global ET estimation to characterize the long-term spatiotemporal variations of the global terrestrial water budget. (Resume d'auteur)

International audience; Agricultural research has to tackle complex questions such as the design of sustainable cropping systems. System experiments are innovative approaches to address this challenge and a framework to iteratively design annual cropping systems has been proposed by Debaeke et al. (2009). However, specificities of some other cropping systems are not considered. Orchards are complex perennial agroecosystems formed of grass and tree layers aiming at the production of fresh fruit that require specific design and management over space and time. To identify orchard specificities and adapt the design framework to such perennial systems, we used two case studies of orchards aiming at decreasing pesticide use in temperate (apple, system experiment) and tropical (citrus, on-farm network) fruit productions. Specificities to take into account in the design framework are: (1) the spatial heterogeneity of the orchard with grass and tree layers, and tree rows and alleys; (2) the succession and interrelations among a young unproductive and then a productive stage; (3) the permanency of the fruit-tree crop constraining the management of soil fertility, (4) ground cover and (5) pest control, especially for pests that complete their lifecycle in the orchard and can build up important populations or inoculum across years. This is especially true in tropical areas where there is no dormant season. (6) Conversely, the permanency of the orchard habitats facilitates the sowing, planting or conservation of plant assemblages (e.g., ground covers, lining hedgerows) to enhance conservation biocontrol and/or compete weeds, provided non-disruptive practices are applied. Because of their longevity, orchards contribute to foster both plant-mediated (e.g., bottom-up) and natural enemy-mediated (e.g., top-down) processes in the foodweb to avoid direct measures against pests. Interactions among the orchard life stages, spatial and functional dimensions and practices need to be explicitly considered to optimize the efficiency of the system as a whole. Using the generic framework proposed by Debaeke et al. (2009) to design annual cropping systems, our framework includes adaptations to account for orchard specificities: (i) Agronomic objectives have to be fixed for each orchard stage; (ii) The cultivar choice and the composition and spatial arrangement of plants within the orchard are key elements to provide the expected services in the long term. This entails to include an additional step of perennial spatial design; (iii) Within-time and −space interactions have to be considered in the decisional system; (iv) Evaluation has to consider all the orchard stages in the global impact or performance, to account for carry-over effects and possible ‘paybacks’ of a given stage or period to the orchard whole lifetime. Last, to handle such complex interactions, design needs knowledge from many stakeholders in the food system (growers, advisors, scientists etc.) and requires more and renewed interactions among those stakeholders in a co-design process.

Les systèmes de culture conduits en semis direct sous couvert sont basés sur une réduction totale du travail du sol et une couverture du sol maximale (couverts, mulch). Les modifications d'habitats induites par la mise en place de ces pratiques peuvent agir sur la composition qualitative et quantitative de la flore adventice des cultures, en particulier lorsque la période d'inter-culture est longue (succession cultures d'hiver-cultures d'été). Matériel & Méthodes : La flore spontanée de cultures de blé d'hiver et de soja a été suivie sur une vingtaine de parcelles. Des relevés selon un itinéraire en W sur une zone de 2000m2 ont été réalisés à 2 (soja) ou 3 (blé) périodes pendant l'année culturale. Résultats : Sur l'année culturale, les résultats mettent en avant une richesse taxonomique importante dans les parcelles, avec un nombre de taxons observés qui varie peu en fonction de la culture (35 taxons en moyenne en blé tendre et 37 en soja). La flore qui s'exprime est cependant différente en terme de composition qualitative et quantitative. Suivant les périodes de relevé, on constate que la différence de composition de la flore adventice entre une culture d'été et d'hiver n'est pas aussi marquée que dans les études classiques. Les différences apparaissent surtout sur le relevé avant récolte en soja. Conclusions : La présence d'une couverture maximale du sol en semis direct sous couvert (couvert et culture) empêche la flore adventice de s'exprimer et masque la différence de composition entre culture d'été et d'hiver.

Forests play a crucial role in the global carbon (C) cycle by storing and sequestering a substantial amount of C in the terrestrial biosphere. Due to temporal dynamics in climate and vegetation activity, there are significant regional variations in carbon dioxide (CO₂) fluxes between the biosphere and atmosphere in forests that are affecting the global C cycle. Current forest CO₂ flux dynamics are controlled by instantaneous climate, soil, and vegetation conditions, which carry legacy effects from disturbances and extreme climate events. Our level of understanding from the legacies of these processes on net CO₂ fluxes is still limited due to their complexities and their long-term effects. Here, we combined remote sensing, climate, and eddy-covariance flux data to study net ecosystem CO₂ exchange (NEE) at 185 forest sites globally. Instead of commonly used non-dynamic statistical methods, we employed a type of recurrent neural network (RNN), called Long Short-Term Memory network (LSTM) that captures information from the vegetation and climate’s temporal dynamics. The resulting data-driven model integrates interannual and seasonal variations of climate and vegetation by using Landsat and climate data at each site. The presented LSTM algorithm was able to effectively describe the overall seasonal variability (Nash-Sutcliffe efficiency, NSE = 0.66) and across-site (NSE = 0.42) variations in NEE, while it had less success in predicting specific seasonal and interannual anomalies (NSE = 0.07). This analysis demonstrated that an LSTM approach with embedded climate and vegetation memory effects outperformed a non-dynamic statistical model (i.e. Random Forest) for estimating NEE. Additionally, it is shown that the vegetation mean seasonal cycle embeds most of the information content to realistically explain the spatial and seasonal variations in NEE. These findings show the relevance of capturing memory effects from both climate and vegetation in quantifying spatio-temporal variations in forest NEE., 28 Feb 2019: The PLOS ONE Staff (2019) Correction: Memory effects of climate and vegetation affecting net ecosystem CO2 fluxes in global forests. PLOS ONE 14(2): e0213467. https://doi.org/10.1371/journal.pone.0213467.

Le processus d’arénização initialement conceptualisé pour la région sud-ouest du Rio Grande do Sul a également lieu dans d'autres régions du pays. Des études montrent que le type de sol, les Neosols Quartzo-arénitiques (RQo), convergent vers ces zones. Dans ces conditions, le présent travail propose d’analyser le comportement temporel de la couverture végétale de ces zones. Les objectifs de cette étude étaient d’analyser les variations spatio-temporelles de la couverture végétale dans les zones de RQo dues au NDVI et à l’EVI, associée à l'apparition d’arenização à Gilbués/PI, Mateiros/TO, Serranópolis/GO et Maçambará/RS, dans le but de: vérifier l'occurrence d'un comportement saisonnier des indices. Pour atteindre les objectifs, des échantillons de polygones ont été sélectionnés dans les zones d'étude et l'outil Web SATVeg a généré les spectres temporels NDVI et EVI du capteur MODIS de 2000 à 2015. Pour l'analyse des caractéristiques de la série chronologique des images MODIS a utilisé la méthodologie créée par Forkel et al. (2013), mis en oeuvre dans le logiciel R via le package greenbrown. Les données de précipitation et de température ont également été collectées à l'aide de l'outil Web SeriesView afin de les corréler avec les données NDVI et EVI. En conséquence, nous avons observé un comportement saisonnier des spectres temporels de NDVI et EVI influencé par la dynamique climatique de chaque zone. À Gilbués, Mateiros et Serranópolis, la saisonnalité de la couverture végétale naturelle du Cerrado convertie en pâturage est directement liée à la dynamique des précipitations dans cette région. À Maçambará/RS, la température est responsable de la saisonnalité des formations de campagne de la Pampa. Le package greenbrown fournissait les schémas spatiaux de moyenne, tendance, IAV, saisonnalité et STV de chaque série temporelle NDVI et EVI des zones RQo, montrant les similitudes et les spécificités entre les zones en fonction du type de couverture végétale et d'utilisation des terres. intensités des processus de ponçage. L'analyse des résultats a permis d'établir des caractéristiques similaires et distinctes des facteurs analysés liés à la variation spatio-temporelle de la couverture végétale des NDVI et EVI, dans des zones de sols RQo, associées à la survenue d'une arénisation à Gilbués, Mateiros, Serranópolis et à Maçambará. O processo de arenização conceituado inicialmente para a região sudoeste do Rio Grande do Sul, também ocorre em outras áreas do país. Estudos demonstram que o ponto convergente dessas áreas é o tipo de solo, o Neossolos Quartzarênicos Órticos (RQo). Diante disso, o presente trabalho propõe analisar o comportamento temporal da cobertura vegetal dessas áreas. Como objetivos buscou-se analisar a variação espaço-temporal de NDVI e EVI da cobertura vegetal em áreas de RQo, associados a ocorrência de arenização em Gilbués/PI, Mateiros/TO, Serranópolis/GO e em Maçambará/RS, com o intuito de verificar uma ocorrência de comportamento sazonal dos índices. Para atingir os objetivos, selecionou-se polígonos amostrais nas áreas de estudo e por meio da ferramenta web SATVeg gerou-se espectros temporais de NDVI e EVI do sensor MODIS do período de 2000 a 2015. Para a análise das características da série temporal das imagens MODIS utilizou a metodologia criada por Forkel et al. (2013), implementada no software R por meio do pacote greenbrown. Coletou-se também dados de precipitação e temperatura por meio da ferramenta web SeriesView para correlacioná-los com os dados de NDVI e EVI. Como resultados, observou-se um comportamento sazonal dos espectros temporais de NDVI e EVI influenciados pela dinâmica climática de cada área. Em Gilbués, Mateiros e Serranópolis a sazonalidade da cobertura vegetal do Cerrado natural e convertido em pastagens relaciona-se diretamente com a dinâmica das chuvas dessa região. Em Maçambará/RS é a temperatura responsável pela sazonalidade das formações campestres do Pampa. O pacote greenbrown forneceu os padrões espaciais da média, tendência, IAV, sazonalidade e STV de cada série temporal de NDVI e EVI das áreas de RQo, evidenciando semelhanças e especificidades entre as áreas de acordo com o tipo de cobertura vegetal e uso do solo e intensidades dos processos de arenização. A partir da análise dos resultados foi possível estabelecer características semelhantes e distintas dos fatores analisados que se relacionam com a variação espaço-temporal de NDVI e EVI da cobertura vegetal em áreas de solos RQo, associados à ocorrência de arenização em Gilbués/PI, Mateiros/TO, Serranópolis/GO e em Maçambará/RS. The sandization process initially conceptualized for the southwest region of Rio Grande do Sul also occurs in other areas of the country. Studies show that the converging point of these areas is the soil type, the Neossolos Quartzarênicos Órticos (RQo). Given this, the present work proposes to analyze the temporal behavior of the vegetation cover of these areas. The objectives of this study were to analyze the NDVI and EVI spatiotemporal variation of vegetation cover in RQo areas, associated with the occurrence of sanding in Gilbués / PI, Mateiros/TO, Serranópolis/GO and Maçambará/RS, aiming at verify an occurrence of seasonal behavior of the indices. To achieve the objectives, sample polygons were selected in the study areas and the SATVeg web tool generated NDVI and EVI temporal spectra of the MODIS sensor from 2000 to 2015. For the analysis of the characteristics of the time series of the images MODIS used the methodology created by Forkel et al. (2013), implemented in software R through the greenbrown package. Precipitation and temperature data were also collected using the SeriesView web tool to correlate them with NDVI and EVI data. As a result, we observed a seasonal behavior of NDVI and EVI temporal spectra influenced by climate dynamics of each area. In Gilbués, Mateiros and Serranópolis the seasonality of the natural Cerrado vegetation cover and converted to pasture is directly related to the rainfall dynamics of this region. In Maçambará / RS is the temperature responsible for the seasonality of the Pampa countryside formations. The greenbrown package provided the spatial patterns of mean, trend, IAV, seasonality and STV of each NDVI and EVI time series of the RQo areas, showing similarities and specificities between areas according to the type of vegetation cover and land use. intensities of sanding processes. From the analysis of the results it was possible to establish similar and distinct characteristics of the analyzed factors that are related to the NDVI and EVI spatiotemporal variation of the vegetation cover in areas of RQo soils, associated to the occurrence of arenization in Gilbués / PI, Mateiros / TO, Serranópolis / GO and in Maçambará / RS.

This study focused on leaf and root density dynamics of the most dominant tree species (Vitellaria paradoxa) of West African savannas in two land use types (farmed land and forest). Ten trees located at least 100 m from each other were selected, with five trees each located in the field and in the forest. Five of the trees were of small-diameter [two in the fields (diameter at breast height or DBH 20.1–20.7 cm) and three in the forest (DBH 7.0–8.0–10.8 cm)] and five others were of large-diameter [three in the fields (DBH 38.2–81.8–81.9 cm) and two in the forest (DBH 20.1–20.7 cm)]. One near-vertical rhizotron was installed under each tree to evaluate root density while canopy openness, diffuse and directly transmitted light were monitored by taking hemispheric photograph monthly. After a two-year period of monitoring, the results revealed a strong seasonality in root density with peak root density observed during the rainy season in August and the lowest production during the dry season in April. Significant lowest canopy openness was observed from August to September while the highest occurred from March to May, which was found to be synchronous with fine root dynamics. The light interception followed the same trends as the leaf production. Furthermore, both mature and young trees showed significant higher root density in the fields compared to the forest while the mean values of all the parameters of canopy openness and light transmittance were higher in the forest than the fields.

National audience

International audience; Monitoring vegetation cover during winter is a major environmental and scientific issue in agricultural areas. From an environmental viewpoint, the presence and type of vegetation cover in winter influences the transport of pollutants to water resources. From a methodological viewpoint, characterizing spatio-temporal dynamics of land cover and land use at the field scale is challenging due to the diversity of farming strategies and practices in winter. The objective of this study was to evaluate the respective advantages of Sentinel optical and SAR time-series to identify land use in winter. To this end, Sentinel-1 and -2 time-series were classified using Support Vector Machine and Random Forest algorithms in a 130 km(2) agricultural area. From the classification, the Sentinel-2 time-series identified winter land use more accurately (overall accuracy (OA) = 75%, Kappa index = 0.70) than that of Sentinel-1 (OA = 70%, Kappa = 0.66) but a combination of the Sentinel-1 and -2 time-series was the most accurate (OA = 81%, Kappa = 0.77). Our study outlines the effectiveness of Sentinel-1 and -2 for identify land use in winter, which can help to change agricultural practices.

International audience; Timely and efficient land-cover mapping is of high interest, especially in agricultural landscapes. Classification based on satellite images over the season, while important for cropland monitoring, remains challenging in subtropical agricultural areas due to the high diversity of management systems and seasonal cloud cover variations. This work presents supervised object-based classifications over the year at 2-month time-steps in a heterogeneous region of 12,000 km(2) in the Sao Paulo region of Brazil. Different methods and remote-sensing datasets were tested with the random forest algorithm, including optical and radar data, time series of images, and cloud gap-filling methods. The final selected method demonstrated an overall accuracy of approximately 0.84, which was stable throughout the year, at the more detailed level of classification; confusion mainly occurred among annual crop classes and soil classes. We showed in this study that the use of time series was useful in this context, mainly by including a small number of highly discriminant images. Such important images were eventually distant in time from the prediction date, and they corresponded to a high-quality image with low cloud cover. Consequently, the final classification accuracy was not sensitive to the cloud gap-filling method, and simple median gap-filling or linear interpolations with time were sufficient. Sentinel-1 images did not improve the classification results in this context. For within-season dynamic classes, such as annual crops, which were more difficult to classify, field measurement efforts should be densified and planned during the most discriminant window, which may not occur during the crop vegetation peak.