Search

Leaf area is a key structural characteristic of forest canopies because of the role of leaves in controlling many biological and physical processes occurring at the biosphere-atmosphere transition. High pulse density Airborne Laser Scanning (ALS) holds promise to provide spatially resolved and accurate estimates of plant area density (PAD) in forested landscapes, a key step in understanding forest functioning: phenology, carbon uptake, transpiration, radiative balance etc. Inconsistencies between different ALS sensors is a barrier to generating globally harmonised PAD estimates. The basic assumption on which PAD estimation is based is that light attenuation is proportional to vegetation area density. This study shows that the recorded extinction strongly depends on target detectability which is influenced by laser characteristics (power, sensitivity, wavelength). Three different airborne laser scanners were flown over a wet tropical forest at the Paracou research station in French Guiana. Different sensors, flight heights and transmitted power levels were compared. Light attenuation was retrieved with an open source ray-tracing code (http://amapvox.org). Direct comparison revealed marked differences (up-to 25% difference in profile-averaged light attenuation rate and 50% difference at particular heights) that could only be explained by differences in scanner characteristics. We show how bias which may occur under various acquisition conditions can generally be mitigated by a sensor intercalibration. Alignment of light weight lidar attenuation profiles to ALS reference attenuation profiles is not always satisfactory and we discuss what are the likely sources of discrepancies. Neglecting the dependency of apparent light attenuation on scanner properties may lead to biases in estimated vegetation density commensurate to those affecting light attenuation estimates. Applying intercalibration procedures supports estimation of plant area density independent of acquisition characteristics.

Le 23 septembre 2009, en fin de nuit, 150 mm de pluie se sont abattus brutalement dans le secteur de Redeyef. Ces précipitations ont engendré des ruissellements urbains abondants et des crues très violentes de l'oued Dakhla (5,74 km2 en amont de Redeyef) et de ses affluents (superficie totale de 14,8 km2 en aval de la ville), qui ont fait des victimes et causé des dégâts importants. Malgré des connaissances limitées sur la pluie et l'absence de données hydrologiques, l'étude de cet événement permet, à travers l'exploitation des données de terrain et la cartographie des espaces inondés, de mettre en relation les conditions pluvio-hydrologiques, l'extension du tissu urbain et les aménagements influençant les écoulements. Cet épisode exceptionnel offre un exemple des risques auxquels sont exposées les localités développées en bordure d'un oued en milieu aride. On September 23, 2009 and by the end of the night, 150 mm of rain suddenly fell in the Redeyef region. This precipitation generated abundant urban runoffs and very violent floods in the Dakhla wadi (5.74 km2 upstream of Redeyef) and its tributaries (total area of 14.8 km2 downstream of the city). The runoffs and floods produced victims and caused significant damages. Despite limited knowledge about rainfall and lack of hydrological data, the present study focusses on the event mentioned above. It purports to investigate the connection, through the use of field data collected and the mapping of flooded areas, between the pluvio-hydrological conditions, the extension of the urban fabric, and developments influencing the flows. The September 23, 2009 exceptional floods in the Redeyef region, represent an example of the risks to which the localities bordering a wadi in an arid environment are exposed.

La compréhension et la caractérisation de la variabilité climatique à grande échelle s'avèrent fondamentales pour appréhender ses impacts, la vulnérabilité locale et partant proposer des solutions appropriées. C'est dans ce contexte que se situe cet article, qui vise à analyser les différentes stratégies d'adaptation développées par les cultivateurs des arrondissement de Barkédji, Sagatta Djoloff et Yang-Yang, situés dans le département de Linguère, face à la variabilité climatique. Ce département est soumis, depuis quelques décennies à une forte instabilité pluviométrique, d'après les données de la station de Linguère sur la période 1951-2017. L'analyse de la variabilité à partir du test de rupture de PETTIT fait ressortir trois périodes distinctes : une période très pluvieuse de 1951 à 1969, une autre, sèche, qui va de 1970 aux années 2000, et une période marquée par une nette amélioration de la pluviométrie à la fin des années 2000.Cette situation de variabilité pluviométrique a sévèrement affecté l'agriculture, qui constitue l'une des principales activités des populations, ainsi que leurs moyens de subsistance. C'est ainsi que les paysans ont mis en place plusieurs stratégies d'adaptation. Parmi ces dernières, nous pouvons retenir celles relatives aux méthodes culturales (choix des espèces et variétés cultivées) et à la diversification des activités rurales. Ces différentes stratégies ont été appréhendées à partir d'enquêtes de terrain menées auprès de la population agricole. Understanding and characterizing large-scale climate variability is fundamental to understanding its impacts, local vulnerability and thus proposing appropriate solutions. It is in this context that this article aims to analyze the different adaptation strategies developed by farmers in the sylvopastoral area of the department of Linguère district of Barkédji, Sagatta Djoloff and Yang-Yang located in the department of Linguère, in the face of climate variability. This department has been subject to high rainfall instability for several decades, according to data from the Linguère station over the period 1951-2017. The analysis of variability from the PETTIT rupture test reveals three distinct periods: a very rainy period from 1951 to 1969, another dry period from 1970 to the 2000s, and a period marked by a marked improvement in rainfall in the late 2000s.This situation of rainfall variability has severely affected agriculture, which is one of the main activities of the populations as well as their livelihoods. As a result, the farmers in the department have implemented several adaptation strategies. These include those relating to farming methods (choice of cultivated species and varieties) and to diversification of rural activities. These different strategies were apprehended from field surveys conducted near the agricultural population of the department of Linguère.

International audience; The Sahel is a fragile region, characterized in recent decades by profound changes in land use, which are the result of complex interactions between societies and their environment. These phenomena, which modulate and transform the landscape, take place on several spatial and temporal scales. However, few studies have highlighted this multidimensional reality, most generally focusing only on the local or regional level, and on a single site. In this study, we mobilized two scales (local and regional) on three different sites. On the one hand, we performed a diachronic mapping of land cover by the analysis of multispectral Landsat images and, on the other hand, we studied its articulation with NDVI and rainfall time series.The results bring out an original synthesis of the land cover trends observed in the Sahelian agro-pastoral zone. They help understanding the complexity of the multi-scale phenomena that characterize the evolution of Sahelian areas. If the analysis of the time series confirms, as has been observed by several authors, an overall regreening trend on a regional basis as a result of the improvement in rainfall conditions from the 1990s, the diachronic analyzes proposed in this study found significant contrasts at finer scales. Considering the total area mapped (Landsat images covering each region), the areas of vegetation cover progression between 1999 and 2010 represent 18 % of the Gourma area and 27 % for Fakara. In terms of net change between 1999 and 2010, in Fakara which has the highest rate of progression (+13 %), the Dantiandou municipality shows, in contrast, a negative rate (-35 %) which is not the case in the two other studied municipalities: +7 % for Téssékré (in Ferlo) and +12 % for Hombori (in Gourma).; La bande sahélienne est une région fragile, caractérisée ces dernières décennies par des changements profonds de l'occupation du sol, résultats de processus biophysiques et de complexes interactions entre les sociétés et leur environnement. Ces processus, qui modulent et transforment le paysage, s'expriment à plusieurs échelles spatiales et temporelles. Pourtant peu de travaux mettent en valeur cette réalité multidimensionnelle et rares sont les approches comparatives multiscalaires. Dans cette étude, deux échelles (locale et régionale) ont été conjointement mobilisées, sur trois sites. La cartographie diachronique de la couverture du sol par l'analyse d'images multispectrales Landsat et son articulation avec l'analyse des séries temporelles (pluviométrie et NDVI) ont été couplées.Les résultats mettent en lumière une synthèse originale des tendances observées concernant les changements d'occupation du sol par la végétation en zone agropastorale sahélienne. Ils permettent de mieux cerner la complexité du caractère multiscalaire de l'évolution des espaces sahéliens. À la suite de nombreux auteurs, l'analyse des séries temporelles confirme globalement une tendance au reverdissement à l'échelle régionale comme résultat de l'amélioration des conditions pluviométriques à partir des années 1990. Cependant les analyses diachroniques proposées dans cette étude ont révélé d'importants contrastes puisque par rapport à la surface totale cartographiée (emprise des images Landsat couvrant chaque région) les surfaces de progression de la couverture végétales entre 1999 et 2010 correspondent à 18 % de la zone du Gourma et 27 % pour le Fakara. En termes d'évolution nette entre 1999 et 2010, dans le Fakara, qui présente le plus fort taux de progression (+13 %), la commune de Dantiandou montre, à l'inverse, un taux négatif (-35 %), ce qui n'est pas le cas des deux autres communes étudiées : +7 % pour Téssékré (dans le Ferlo) et +12 % pour Hombori (dans le Gourma).

Les pluies exceptionnelles du 2 octobre 2020 qui ont concerné les montagnes des Alpes-Maritimes, dans le Sud-Est de la France, resteront marquées dans les annales statistiques et, particulièrement, dans l'esprit des habitants des hautes-vallées de la Vésubie et de la Roya, surtout par leurs conséquences catastrophiques. Le risque est ici décrit par l'articulation de trois composantes que sont l'aléa, la susceptibilité et la vulnérabilité.L'aléa, composante initiale constituée par les précipitations et les mécanismes qui les ont engendrées, est remarquable. En effet plusieurs facteurs se sont conjugués pour produire de très vigoureuses ascendances de l'air sur cette région : un cyclonisme particulièrement puissant pour la saison (une dynamique d'hiver en première partie d'automne associée à un puissant talweg très creusé), affectant de l'air instable en basses couches, air très riche en vapeur d'eau après son survol de la Méditerranée encore chaude en cette saison, et la rare coïncidence d'un très fort gradient de pression et ses isobares orientés sud-nord avec un relief pentu et élevé, persistant plus de 24 heures.À l'ouest du fleuve Var (Préalpes de Grasse), le flux de sud à sud-sud-ouest s'est heurté perpendiculairement aux premiers reliefs proches de la mer orientés ouest-est (1200-1800 m d'altitude), d'où de forts cumuls pluviométriques dépassant 200, voire 300 mm en 24 heures à 20-25 km du littoral, par effet de barrage orographique. À l'est du fleuve Var, la topographie orientée cette fois sud-nord, parallèlement au flux de basses couches, a conduit celui-ci loin vers l'intérieur, avec des vents tempétueux le forçant à se soulever progressivement mais avec puissance jusqu'à la ligne de crête du Mercantour (3000 m d'altitude). Les cumuls mesurés atteignent 513 mm en 24 heures à Saint-Martin-Vésubie et 663 mm (dont 336 mm en 6 heures) au lac des Mesches (bassin versant de la Roya) à 40 km du littoral, par effet de guidage.Autre originalité, les surfaces concernées sont très étendues : on estime à environ 2000 km2 la surface ayant reçu plus de 200 mm, occasionnant des lames d'eau de 50 à près de 100 millions de mètres cubes selon les bassins versants.Les périodes de retour de telles précipitations sont hors norme, en particulier pour Saint-Martin-Vésubie où les 7300 ans sont dépassées selon un ajustement avec la loi de GUMBEL, ou encore 486 à 5276 ans (en fonction du paramètre k) avec une distribution de Valeurs Extrêmes Généralisée (GEV) qui s'avère mieux adaptée. À Tende (bourg), la période de retour atteint 550 ans selon GEV (800 ans selon la loi de GUMBEL). Le poste de Breil-sur-Roya est moins affecté, avec une période de retour inférieure à centennale, les pluies les plus abondantes étant tombées en amont.Des volumes d'eau énormes ont pu s'infiltrer et ruisseler, dans des proportions et à des vitesses très variables selon les conditions rencontrées par les gouttes de pluie à la surface du sol, qui sont déterminées par la seconde composante du risque : la susceptibilité, potentiel de production de crues et de mouvements de terrain faisant suite à de fortes précipitations.Celle-ci a généré des phénomènes d'ampleur variable selon les bassins versants, en fonction de plusieurs paramètres : la superficie, la pédologie, la lithologie, le relief, en particulier les pentes, sans oublier le taux de couverture végétale. C'est la combinaison de ces paramètres qui a fait que la crue engendrée fut plus ou moins importante et rapide. En haute altitude les fortes pentes et des terrains plutôt imperméables et assez dénudés ont permis la genèse de ruissellements vigoureux entraînant une quantité innombrable de glissements de terrains et de ravinements sur les flancs des vallées. Ces derniers sont venus alimenter les rivières et torrents devenus furieux en matériaux solides de toutes dimensions, créant des flots boueux dévastateurs. Si les écoulements ont parfois sapé des pans entiers des berges, ils ont également contribué à combler localement le lit des rivières en l'exhaussant de plusieurs mètres à certains endroits.La combinaison de l'aléa et de la susceptibilité a occasionné un risque majeur au regard de la vulnérabilité des fonds de vallées. En effet, les enjeux y sont forts puisqu'elles concentrent des voies de communication et des populations résidant souvent le long des rivières, voire dans leurs lits majeurs par endroits. Les terrains alluviaux ou fluvioglaciaires, sans cohésion, ont été déblayés par ces crues avec les habitations et infrastructures qui s'y trouvaient. Le bilan humain et socio-économique est très lourd : près de 20 morts, des populations traumatisées, des dizaines de bâtiments et maisons totalement détruits ou rendus inhabitables, des paysages dévastés et métamorphosés, des dizaines de ponts et des kilomètres de routes rayés de la carte.En proposant une grille de lecture, l'exposé de l'articulation intra et inter composantes du risque explique que ces dégâts aient dépassé de loin ceux liés aux habituelles crues automnales méditerranéennes (I. BARRET et al., 1994), ainsi que ce qui pouvait être imaginable en référence à une mémoire collective séculaire. Malgré les vies humaines perdues et les dégâts matériels considérables, la catastrophe aurait pu être pire si, d'une part, les moyens de lutte et de prévention immédiate ne s'étaient aussi bien exprimés et si, d'autre part, il n'avait pas existé de culture du risque, dont le degré est séculairement plutôt élevé chez les populations de ces vallées montagnardes, par rapport aux citadins du littoral azuréen. The exceptional rains of October 2, 2020, which affected the mountains of the Alpes-Maritimes, in southeastern France, will remain marked in the annals of statistics, and particularly in the minds of the inhabitants of the high valleys of the Vésubie and Roya, especially by their catastrophic consequences. The risk is described here by the articulation of three components that are the hazard, susceptibility and vulnerability.The hazard, the initial component consisting of rainfall and the mechanisms that generated it, is remarkable. Indeed, several factors combined to produce very strong air ascents over this region: a particularly powerful cyclone for the season, affecting unstable air in low layers, air very rich in water vapor after its overflight of the Mediterranean still warm in this season, and the rare coincidence of a very strong pressure gradient and its isobars oriented south-north with a steep and high relief, for more than 24 hours. To the west of the Var River (Grasse Pre-Alps), the south to south-southwest flow collided perpendicularly with the first reliefs near the sea oriented west-east (1200-1800 m in altitude), resulting in heavy rainfall totals exceeding 200, even 300 mm in 24 hours at 20-25 km from the coast, due to the orographic barrier effect. To the east of the Var River, the topography, this time oriented south-north, parallel to the low-level flow, led the latter far inland, with stormy winds forcing it to rise gradually but powerfully to the Mercantour ridge line (3000 m altitude). Cumulative rainfall measured reached 513 mm in 24 hours at Saint Martin-Vésubie and 663 mm (including 336 mm in 6 hours) at the Mesches lake (Roya watershed) 40 km from the coast, due to the guidance effect.Another originality is that the areas concerned are very extensive: it is estimated that about 2000 km2 received more than 200 mm, causing water levels of 50 to nearly 100 million cubic meters depending on the catchment area. The return periods of such rainfall are out of the ordinary, especially for Saint-Martin-Vésubie where the 7300 years are exceeded according to an adjustment with a GUMBEL law, or 486 to 5276 years (depending on parameter k) with a distribution of Generalized Extreme Values (GEV) which proves to be better adapted. At Tende (town), the return period reaches 550 years according to GEV (800 years according to a GUMBEL law). The station of Breil-sur-Roya is less affected with a value less than 100 years, the most abundant rains having fallen upstream. Huge volumes of water were able to infiltrate and run off, in proportions and at very variable speeds depending on the behavior of the raindrops on the surface of the ground, which is determined by the second component of the risk: susceptibility, the potential for the production of floods and ground movements following heavy rainfall.This generated phenomena of varying magnitude depending on the watersheds, depending on several parameters that distinguish, as their extent, pedology, lithology, or topography and slopes without forgetting the rate of vegetation cover. It is the combination of these parameters that made the flood generated more or less important and fast. At high altitudes, the steep slopes and the rather impermeable and bare ground allowed for the generation of vigorous runoff leading to an innumerable number of landslides and gullies on the sides of the valleys. These have fed the rivers and streams in fury with solid materials of all sizes, creating muddy devastating flows. If the floods have sometimes undermined entire sections of the riverbanks, they have also contributed to locally filling in the riverbed by raising it by several meters in some places.The combination of hazard and susceptibility has caused a major risk in terms of the vulnerability of the valley bottoms. Indeed, the stakes are high because they concentrate communication routes and populations often residing along the rivers, even in their major beds in some places. The alluvial or fluvioglacial soils, without cohesion, have been cleared by these floods with the houses and infrastructures that were there. The human and socio-economic toll is very high: nearly 20 deaths, traumatized populations, numerous buildings and houses totally destroyed or rendered uninhabitable, devastated and metamorphosed landscapes, dozens of bridges and kilometers of roads wiped out. By proposing an interpretation grid, the presentation of the intra- and inter-component articulation explains that this damage far exceeded that linked to the usual Mediterranean autumn floods (I. BARRET et al., 1994), as well as what could be imagined in reference to a secular collective memory. In spite of the human lives lost and the considerable material damage, the disaster could have been worse, if on the one hand the means of fight and immediate prevention had not been so well expressed, and on the other hand if there had not been a culture of risk, the degree of which is secularly rather high among the populations of these mountain valleys, compared to the city dwellers of the Côte d'Azur coast.[traduction effectuée sur https://www.deepl.com/fr/translator]

Mieux comprendre l'origine de la ressource en eau afin d'en améliorer la gestion est aujourd'hui une nécessité. Les cours d'eau de l'amont cévenol du bassin versant des Gardons, présentent des différences dans leurs débits de basses eaux. Ces écarts entre débits s'expliquent, hors des différences liées aux précipitations (orages...), par des contributions particulières des réservoirs géologiques, dans la mesure où les basses eaux correspondent globalement à un régime hydraulique non influencé (tarissement).L'étude a été réalisée principalement durant les étés 2018 et 2019. Les débits et la minéralisation des eaux de surface et des eaux souterraines ont été suivis sur neuf sous-bassins versants. Un modèle de mélange, appliqué en complément du suivi géochimique, permet de quantifier la contribution des différentes formations aquifères et montre de fortes différences entre elles. À l'étiage, deux formations, les micaschistes noirs et les calcaires, se révèlent primordiales dans le soutien des débits : elles alimenteraient les cours d'eau étudiés à hauteur de 41 et 17 % respectivement, alors qu'elles ne couvrent que 13 et 8 % du secteur considéré. L'analyse de la contribution des différentes formations permet d'expliquer les différences de débit spécifique observées pour les cours d'eau du terrain d'étude. Ces contributions à l'étiage, couplées aux débits, permettent d'identifier les réservoirs les plus productifs, qui sont à protéger en priorité. The increase in the severity of hydrological droughts in the Mediterranean basin in relation to climate change leads to the need to better understand the origin of the water resource to improve its management. The defined study area, the Cevennes upper watershed of the Gardons, presents quite significant variations in terms of low water flows. This article questions these differences and proposes to explain these variances in flows not by a rainfall difference but by a variation in the contribution of the geological reservoirs present in the different watersheds.The study was conducted mainly during the summers of 2018 and 2019 where flows and geochemistry of surface water and groundwater were monitored in 9 watersheds. The use of mixing model in addition to this geochemical-hydrological coupling allows to quantify the contribution of the different formations and shows strong contrast between them. At low water, two formations, black micaschists and limestone, appear to be essential to sustain the flow: they would feed the streams studied to the extent of 41 and 17 % respectively, while they cover only 13 and 8 % of the considered area. The analysis of the contribution of the respective geological formations allows to explain the observed specific discharge of the rivers in the study area.This information of contribution in low water coupled with the flow allows to identify the most productive reservoirs and could help to prioritize the protection of these in view of the scarcity of the resource that will result from climate change.

This present study exposes the results of a work on the island of Martinique, on agroforestry systems (AF) type «complex agroforests» integrating agricultural production under the forest cover. Part of the Regional Forest and Wood Program (RFWP) 2019 – 2029, this study aims to meet several objectives: (i) capitalize and list the maximum information on systems with production under forest cover ; (ii) draft and propose a clear and precise technical definition on the practice of «production under forest cover» in Martinique context; (iii) draft and propose a document of technical itineraries on agroforestry practices encountered in forests during surveys ; (iv) carry out an initial technical and economic evaluation of systems with initial economic returns. This work is accomplished through a qualitative approach to agroforestry systems (through semi-direct interviews) and a semi-quantitative approach to the technico-economic performance of the systems in production.; Cette présente étude expose les résultats d’un travail sur l’île de la Martinique, portant sur les systèmes agroforestiers (SAF) type « agroforêts complexes » intégrant des productions agricoles s’insérant sous le couvert forestier. Inscrite dans le cadre du Programme Régional Forêt et Bois (PRFB) 2019 – 2029, cette étude a pour but de répondre à plusieurs objectifs : (i) capitaliser et répertorier le maximum d’informations sur les systèmes avec productions sous couvert forestier ; (ii) rédiger et proposer une définition technique claire et précise sur la pratique de « production sous couvert forestier » en contexte martiniquais ; (iii) rédiger et proposer un document d’itinéraires techniques sur les pratiques agroforestières rencontrées en forêt lors des enquêtes ; (iv) réaliser une première évaluation technico-économique des systèmes ayant des premiers retours économiques. Ce travail est accompli via une approche qualitative des systèmes agroforestiers (à travers des entretiens semi-directifs) et une approche semi-quantitative des performances technico-économiques des systèmes en production.

Cette étude des changements de l'occupation du sol dans le bassin versant de la Lobo (12767 km2) s'appuie sur les images multispectrales TM (1986), ETM+ (2008) et OLI (2015) des satellites Landsat et sur des levés de terrain servant de contrôle. Les traitements appliqués aux images ont alimenté une base de données gérée dans un SIG. La cartographie de l'occupation du sol en 1986, 2008 et 2015 a permis d'évaluer les mutations entre les différentes dates. Les classes "culture-jachère" et "culture" ont toujours été largement dominantes, mais avec de fortes variations pour chacune d'elles, les deux variant en sens inverse. Dès 1986, la classe forêt ne représentait que 4,6 % du terrain d'étude (584 km2). Sa part est tombée à 0,96 % (123 km2) en 2008, avant de remonter à 2,3 % (299 km2) en 2015, en lien pour partie avec le développement de cultures arbustives. Sur la période d'étude, la forêt a considérablement régressé dans les secteurs où elle aurait dû être protégée, la forêt classée du Haut-Sassandra et le Parc National de la Marahoué. This study of land cover changes in the Lobo watershed (12767 km2) is based on multispectral TM (1986), ETM+ (2008) and OLI (2015) images from Landsat satellites and on field surveys as a control. The processing applied to the images fed a database managed in a GIS. The mapping of land use in 1986, 2008 and 2015 made it possible to assess the changes between the different dates. The "crop-fallow" and "crop" classes have always been largely dominant, but with strong variations for each of them, both varying in opposite directions. As early as 1986, the forest class represented only 4.6 % of the study area (584 km2 ). Its share fell to 0.96 % (123 km2) in 2008, before rising to 2.3 % (299 km2) in 2015, partly in connection with the development of shrub crops. Over the study period, the forest declined considerably in the areas where it should have been protected, the classified forest of Haut-Sassandra and the Marahoué National Park.[Translated with https://www.deepl.com/fr/translator (free version)]

Made available in DSpace on 2021-06-25T11:16:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Agence Nationale Des Parcs Nationaux Centre for International Forestry Research Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS) David and Lucile Packard Foundation European Space Agency Leverhulme Trust Gordon and Betty Moore Foundation Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de Goiás European Research Council Belgian Federal Science Policy Office Vlaamse Interuniversitaire Raad Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Science Foundation Natural Environment Research Council Royal Society National Geographic Society Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of funding agencies. Here we show how a global community is responding to the challenges of tropical ecosystem research with diverse teams measuring forests tree-by-tree in thousands of long-term plots. We review the major scientific discoveries of this work and show how this process is changing tropical forest science. Our core approach involves linking long-term grassroots initiatives with standardized protocols and data management to generate robust scaled-up results. By connecting tropical researchers and elevating their status, our Social Research Network model recognises the key role of the data originator in scientific discovery. Conceived in 1999 with RAINFOR (South America), our permanent plot networks have been adapted to Africa (AfriTRON) and Southeast Asia (T-FORCES) and widely emulated worldwide. Now these multiple initiatives are integrated via ForestPlots.net cyber-infrastructure, linking colleagues from 54 countries across 24 plot networks. Collectively these are transforming understanding of tropical forests and their biospheric role. Together we have discovered how, where and why forest carbon and biodiversity are responding to climate change, and how they feedback on it. This long-term pan-tropical collaboration has revealed a large long-term carbon sink and its trends, as well as making clear which drivers are most important, which forest processes are affected, where they are changing, what the lags are, and the likely future responses of tropical forests as the climate continues to change. By leveraging a remarkably old technology, plot networks are sparking a very modern revolution in tropical forest science. In the future, humanity can benefit greatly by nurturing the grassroots communities now collectively capable of generating unique, long-term understanding of Earth's most precious forests. Resumen: Los bosques tropicales son los ecosistemas más diversos y productivos del mundo y entender su funcionamiento es crítico para nuestro futuro colectivo. Sin embargo, hasta hace muy poco, los esfuerzos para medirlos y monitorearlos han estado muy desconectados. El trabajo en redes es esencial para descubrir las respuestas a preguntas que trascienden las fronteras y los plazos de las agencias de financiamiento. Aquí mostramos cómo una comunidad global está respondiendo a los desafíos de la investigación en ecosistemas tropicales a través de diversos equipos realizando mediciones árbol por árbol en miles de parcelas permanentes de largo plazo. Revisamos los descubrimientos más importantes de este trabajo y discutimos cómo este proceso está cambiando la ciencia relacionada a los bosques tropicales. El enfoque central de nuestro esfuerzo implica la conexión de iniciativas locales de largo plazo con protocolos estandarizados y manejo de datos para producir resultados que se puedan trasladar a múltiples escalas. Conectando investigadores tropicales, elevando su posición y estatus, nuestro modelo de Red Social de Investigación reconoce el rol fundamental que tienen, para el descubrimiento científico, quienes generan o producen los datos. Concebida en 1999 con RAINFOR (Suramérica), nuestras redes de parcelas permanentes han sido adaptadas en África (AfriTRON) y el sureste asiático (T-FORCES) y ampliamente replicadas en el mundo. Actualmente todas estas iniciativas están integradas a través de la ciber-infraestructura de ForestPlots.net, conectando colegas de 54 países en 24 redes diferentes de parcelas. Colectivamente, estas redes están transformando nuestro conocimiento sobre los bosques tropicales y el rol de éstos en la biósfera. Juntos hemos descubierto cómo, dónde y porqué el carbono y la biodiversidad de los bosques tropicales está respondiendo al cambio climático y cómo se retroalimentan. Esta colaboración pan-tropical de largo plazo ha expuesto un gran sumidero de carbono y sus tendencias, mostrando claramente cuáles son los factores más importantes, qué procesos se ven afectados, dónde ocurren los cambios, los tiempos de reacción y las probables respuestas futuras mientras el clima continúa cambiando. Apalancando lo que realmente es una tecnología antigua, las redes de parcelas están generando una verdadera y moderna revolución en la ciencia tropical. En el futuro, la humanidad puede beneficiarse enormemente si se nutren y cultivan comunidades de investigadores de base, actualmente con la capacidad de generar información única y de largo plazo para entender los que probablemente son los bosques más preciados de la tierra. Resumo: Florestas tropicais são os ecossistemas mais diversos e produtivos da Terra. Embora uma boa compreensão destas florestas seja crucial para o nosso futuro coletivo, até muito recentemente os esforços de medições e monitoramento foram amplamente desconexos. É essencial formarmos redes para obtermos respostas que transcendem fronteiras e horizontes de agências financiadoras. Neste estudo nós mostramos como uma comunidade global está respondendo aos desafios da pesquisa de ecossistemas tropicais, com equipes diversas medindo florestas, árvore por árvore, em milhares de parcelas monitoradas à longo prazo. Nós revisamos as maiores descobertas científicas deste trabalho, e mostramos também como este processo está mudando a ciência de florestas tropicais. Nossa abordagem principal envolve unir iniciativas de base a protocolos padronizados e gerenciamento de dados a fim de gerar resultados robustos em escalas ampliadas. Ao conectar pesquisadores tropicais e elevar seus status, nosso modelo de Rede de Pesquisa Social reconhece o papel-chave do produtor dos dados na descoberta científica. Concebida em 1999 com o RAINFOR (América do Sul), nossa rede de parcelas permanentes foi adaptada para África (AfriTRON) e Sudeste asiático (T-FORCES), e tem sido extensamente reproduzida em todo o mundo. Agora estas múltiplas iniciativas estão integradas através de uma infraestrutura cibernética do ForestPlots.net, conectando colegas de 54 países de 24 redes de parcelas. Estas iniciativas estão transformando coletivamente o entendimento das florestas tropicais e seus papéis na biosfera. Juntos nós descobrimos como, onde e por que o carbono e a biodiversidade da floresta estão respondendo às mudanças climáticas, e seus efeitos de retroalimentação. Esta duradoura colaboração pantropical revelou um grande sumidouro de carbono persistente e suas tendências, assim como tem evidenciado quais direcionadores são mais importantes, quais processos florestais são mais afetados, onde eles estão mudando, seus atrasos no tempo de resposta, e as prováveis respostas das florestas tropicais conforme o clima continua a mudar. Dessa forma, aproveitando uma notável tecnologia antiga, redes de parcelas acendem faíscas de uma moderna revolução na ciência das florestas tropicais. No futuro a humanidade pode se beneficiar incentivando estas comunidades basais que agora são coletivamente capazes de gerar conhecimentos únicos e duradouros sobre as florestas mais preciosas da Terra. Résume: Les forêts tropicales sont les écosystèmes les plus diversifiés et les plus productifs de la planète. Si une meilleure compréhension de ces forêts est essentielle pour notre avenir collectif, jusqu'à tout récemment, les efforts déployés pour les mesurer et les surveiller ont été largement déconnectés. La mise en réseau est essentielle pour découvrir les réponses à des questions qui dépassent les frontières et les horizons des organismes de financement. Nous montrons ici comment une communauté mondiale relève les défis de la recherche sur les écosystèmes tropicaux avec diverses équipes qui mesurent les forêts arbre après arbre dans de milliers de parcelles permanentes. Nous passons en revue les principales découvertes scientifiques de ces travaux et montrons comment ce processus modifie la science des forêts tropicales. Notre approche principale consiste à relier les initiatives de base à long terme à des protocoles standardisés et une gestion de données afin de générer des résultats solides à grande échelle. En reliant les chercheurs tropicaux et en élevant leur statut, notre modèle de réseau de recherche sociale reconnaît le rôle clé de l'auteur des données dans la découverte scientifique. Conçus en 1999 avec RAINFOR (Amérique du Sud), nos réseaux de parcelles permanentes ont été adaptés à l'Afrique (AfriTRON) et à l'Asie du Sud-Est (T-FORCES) et largement imités dans le monde entier. Ces multiples initiatives sont désormais intégrées via l'infrastructure ForestPlots.net, qui relie des collègues de 54 pays à travers 24 réseaux de parcelles. Ensemble, elles transforment la compréhension des forêts tropicales et de leur rôle biosphérique. Ensemble, nous avons découvert comment, où et pourquoi le carbone forestier et la biodiversité réagissent au changement climatique, et comment ils y réagissent. Cette collaboration pan-tropicale à long terme a révélé un important puits de carbone à long terme et ses tendances, tout en mettant en évidence les facteurs les plus importants, les processus forestiers qui sont affectés, les endroits où ils changent, les décalages et les réactions futures probables des forêts tropicales à mesure que le climat continue de changer. En tirant parti d'une technologie remarquablement ancienne, les réseaux de parcelles déclenchent une révolution très moderne dans la science des forêts tropicales. À l'avenir, l'humanité pourra grandement bénéficier du soutien des communautés de base qui sont maintenant collectivement capables de générer une compréhension unique et à long terme des forêts les plus précieuses de la Terre. Abstrak: Hutan tropika adalah di antara ekosistem yang paling produktif dan mempunyai kepelbagaian biodiversiti yang tinggi di seluruh dunia. Walaupun pemahaman mengenai hutan tropika amat penting untuk masa depan kita, usaha-usaha untuk mengkaji dan mengawas hutah-hutan tersebut baru sekarang menjadi lebih diperhubungkan. Perangkaian adalah sangat penting untuk mencari jawapan kepada soalan-soalan yang menjangkaui sempadan dan batasan agensi pendanaan. Di sini kami menunjukkan bagaimana sebuah komuniti global bertindak balas terhadap cabaran penyelidikan ekosistem tropika melalui penglibatan pelbagai kumpulan yang mengukur hutan secara pokok demi pokok dalam beribu-ribu plot jangka panjang. Kami meninjau semula penemuan saintifik utama daripada kerja ini dan menunjukkan bagaimana proses ini sedang mengubah bidang sains hutan tropika. Teras pendekatan kami memberi tumpuan terhadap penghubungan inisiatif akar umbi jangka panjang dengan protokol standar serta pengurusan data untuk mendapatkan hasil skala besar yang kukuh. Dengan menghubungkan penyelidik-penyelidik tropika dan meningkatkan status mereka, model Rangkaian Penyelidikan Sosial kami mengiktiraf kepentingan peranan pengasas data dalam penemuan saintifik. Bermula dengan pengasasan RAINFOR (Amerika Selatan) pada tahun 1999, rangkaian-rangkaian plot kekal kami kemudian disesuaikan untuk Afrika (AfriTRON) dan Asia Tenggara (T-FORCES) dan selanjutnya telah banyak dicontohi di seluruh dunia. Kini, inisiatif-inisiatif tersebut disepadukan melalui infrastruktur siber ForestPlots.net yang menghubungkan rakan sekerja dari 54 negara di 24 buah rangkaian plot. Secara kolektif, rangkaian ini sedang mengubah pemahaman tentang hutan tropika dan peranannya dalam biosfera. Kami telah bekerjasama untuk menemukan bagaimana, di mana dan mengapa karbon serta biodiversiti hutan bertindak balas terhadap perubahan iklim dan juga bagaimana mereka saling bermaklum balas. Kolaborasi pan-tropika jangka panjang ini telah mendedahkan sebuah sinki karbon jangka panjang serta arah alirannya dan juga menjelaskan pemandu-pemandu perubahan yang terpenting, di mana dan bagaimana proses hutan terjejas, masa susul yang ada dan kemungkinan tindakbalas hutan tropika pada perubahan iklim secara berterusan di masa depan. Dengan memanfaatkan pendekatan lama, rangkaian plot sedang menyalakan revolusi yang amat moden dalam sains hutan tropika. Pada masa akan datang, manusia sejagat akan banyak mendapat manfaat jika memupuk komuniti-komuniti akar umbi yang kini berkemampuan secara kolektif menghasilkan pemahaman unik dan jangka panjang mengenai hutan-hutan yang paling berharga di dunia. Instituto de Ecología Regional (IER) Universidad Nacional de Tucumán (UNT) Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Facultad de Ciencias Agrarias Universidad Nacional de Jujuy James Cook University (JCU) CSIRO (Commonwealth Scientific and Industrial Research Organisation) School of Land & Food University of Tasmania CSIRO Tropical Forest Research Centre Independent Researcher Environmental Protection Agency (EPA) Centre for Tropical Environmental and Sustainability Science (TESS) College of Marine and Environmental Sciences James Cook University Centre for Tropical Environmental and Sustainability Science College of Science and Engineering James Cook University University of the Sunshine Coast University of York Flamingo Land Ltd. Sommersbergseestrasse Ghent University CAVElab Ghent University Royal Museum for Central Africa - Service of Wood Biology Isotope Bioscience Laboratory-ISOFYS Ghent University Gembloux Agro-Bio Tech Université de Liege Landscape Ecology and Vegetal Production Systems Unit CAVElab Computational & Applied Vegetation Ecology Ghent University Tropical Forestry Forest Resources Management Gembloux Agro-Bio Tech University of Liege Université Libre de Bruxelles (ULB) Evolutionary Biology and Ecology Royal Museum for Central Africa Royal Museum for Central Africa Ghent University Department of Environment Ghent University Service Evolution Biologique et Ecologie Belize Foundation for Research and Environmental Education IBIF Museo de Historia Natural Noel Kempff Mercado Universidad Autonoma Gabriel Rene Moreno PROMAB Museo Noel Kempff Consultor Independiente Jardin Botanico Municipal de Santa Cruz Museo de Historia Natural Noel Kempff Mercado Forest Management in Bolivia Universidad Autónoma del Beni Riberalta Museo de Historia Natural Noel Kempff Herbario del Sur de Bolivia Universidad Autónoma del Beni Conservation International Instituto de Biodiversidade e Floresta Universidade Federal do Oeste do Pará Universidade Federal de Pernambuco Universidade do Estado de Mato Grosso Universidade do Estado de Mato Grosso (UNEMAT) Projeto TEAM – Manaus Universidade Federal de Juiz de Fora (UFJF) Universidade Federal do Rio de Janeiro Instituto Nacional de Pesquisas da Amazônia Projeto Dinâmica Biológica de Fragmentos Florestais Departamento de Genética Ecologia e Evolução Universidade Federal de Minas Gerais Universidade Estadual de Campinas Laboratório de Ecologia de Comunidades e Funcionamento de Ecossistemas-ECoFERP Departamento de Biologia Faculdade de Filosofia Ciências e Letras USP National Institute for Space Research (INPE) Universidade Federal de Roraima (UFRR) UNESP - São Paulo State University Carbonozero Consultoria Ambiental Departamento de Biologia Universidade Federal do Amazonas (UFAM) Centro de Energia Nuclear na Agricultura Universidade de São Paulo UERR - Campus Rorainópolis Universidade Federal do Acre Instituto Agronômico de Campinas Universidade Federal do Rio Grande do Sul Embrapa Universidade Estadual do Norte Fluminense (UENF) Universidade Federal da Bahia (UFBA) Instituto de Biologia Universidade Estadual de Campinas Universidade Federal do Piauí (UFPI) Botany and Plant Ecology Laboratory Federal University of Acre INPA- Instituto Nacional de Pesquisas da Amazônia UERR - Campus Boa Vista Universidade Federal do Ceará Universidade Federal de Campina Grande Universidade Federal do Para Núcleo de Estudos e Pesquisas Ambientais Universidade Estadual de Campinas Instituto Federal de Educação Ciência e Tecnologia do Acre Instituto de Pesquisas Jardim Botânico do Rio de Janeiro Universidade Federal do Oeste do Pará UEFS Depto. de Ciências Biológicas Universidade Federal do Agreste de Pernambuco (UFAPE) Universidade Estadual de Montes Claros FFCLRP-USP/Br UNEMAT Universidade Federal de Jataí Universidade Federal do Pará Instituto de Ciências Biológicas Universidade de Campinas Universidade Federal de Lavras (UFLA) Museu Goeldi Embrapa Amazônia Oriental Instituto Nacional de Pesquisas da Amazônia UFMG - Universidade Federal de Minas Gerais Fundação Universidade Fedral de Rondônia - UNIR INPA- Instituto Nacional de Pesquisas Amazônicas Instituto Nacional de Pesquisas da Amazônia - Coordenação de Pesquisas em Silvicultura Tropical Jardim Botânico do Rio de Janeiro National Institute for Research in Amazonia Universidade Federal de Roraima (UFRR/PRONAT) Universidade Estadual de Campinas/UNICAMP Instituto Nacional de Pesquisas da Amazônia/CPBO Universidade Federal de Santa Catarina (UFSC) INCAPER- Instituto Capixaba de Pesquisa Assistência Técnica e Extensão Rural INPE- Instituto Nacional de Pesquisas Espaciais Universidade de São Paulo Instituto de Biociências Universidade Estadual Paulista Semiarid National Institute (INSA) Universidade de Brasília Departamento de Engenharia Florestal IBAM - Instituto Bem Ambiental Universidade do Estado de Mato Grosso Campus de Nova Xavantina University in Campinas Universidade Estadual do Norte Fluminense Darcy Ribeiro (UENF) LMF Instituto Nacional de Pesquisas da Amazônia Universidade Federal do Vale do São Francisco USP - University of São Paulo Instituto Federal do Espírito Santo (IFES) INPA - Instituto Nacional de Pesquisas da Amazônia Grupo MAUA Universidade Federal de Mato Grosso Instituto de Ciências Naturais Humanas e Sociais Instituto Nacional da Mata Atlântica RAINFOR-PPBIO Universidade Federal Rural da Amazônia - UFRA/CAPES Universidade Federal do Amazonas (UFAM) INPA/Max-Planck Project EMBRAPA- Empresa Brasileira de Pesquisa Agropecuária (Amazônia Oriental) Serviço Florestal Brasileiro Museu Universitário Universidade Federal do Acre Universidade Federal Rural de Pernambuco PUCPR - Pontifícia Universidade Católica do Paraná Museu Paraense Emilio Goeldi Universiti Brunei Darussalam Environmental and Life Sciences Faculty of Science Universiti Brunei Darussalam Institute for Biodiversity and Environmental Research Universiti Brunei Darussalam Plant Systematic and Ecology Laboratory Department of Biology Higher Teachers’ Training College University of Yaounde I Faculty of Science Department of Botany and Plant Physiology University of Buea Faculty of Science Department of Plant Science University of Buea National Herbarium Plant Systematics and Ecology Laboratory Higher Teachers’ Training College University of Yaoundé I Department of Plant Biology Faculty of Sciences University of Yaounde 1 Bioversity International Faculty of Forestry University of Toronto Ministère des Eaux Forêts Chasse et Pêche (MEFCP) Universidad Católica de la Santísima Concepción Universidad de La Serena Research Institute of Tropical Forestry Chinese Academy of Forestry Kunming Institute of Botany Chinese Academy of Sciences Beijing Forestry University Universidad Nacional Abierta y a Distancia Red COL-TREE Corporación COL-TREE Nuevo Estándar Biotropical NEBIOT SAS Universidad del Tolima Asociación GAICA Universidad de Nariño – Red BST-Col Parques Nacionales Naturales Territorial Caribe – Red BST-Col Universidad del Atlantico – Red BST-Col Departamento de Ciencias Forestales Universidad Nacional de Colombia - Sede Medellín Socioecosistemas y Clima Sostenible Fundacion con Vida Parques Nacionales Naturales de Colombia – Red BST-Col Instituto de Investigación de Recursos Biológicos Alexander von Humboldt – Red BST-Col UNAL Instituto de Investigación Recursos Biologicos Alexander von Humboldt – Red BST-Col Fundación Jardín Botánico de Medellín Herbario “Joaquín Antonio Uribe” (JAUM) – Red BST-Col Universidad Nacional de Colombia sede Amazonia Coltree Facultad del Medio Ambiente y Recursos Naturales Universidad Distrital Francisco José de Caldas – Red BST-Col Universidad de Tolima Fundación Orinoquia Biodiversa – Red BST-Col Departamento de Biología Facultad de Ciencias Naturales Universidad Icesi – Red BST-Col Instituto de Ciencias Naturales Universidad Nacional de Colombia Universidad de los Llanos Servicios Ecoysistemicos y Cambio Climatico (SECC) Fundación Con Vida & Corporación COL-TREE Universidad del Rosario Fundacion Ecosistemas Secos de Colombia – Red BST-Col Universidad de los Andes - ANDES herbarium Institute of Botany Czech Academy of Sciences Palacky University Czech University of Life Sciences Mendel University World Wide Fund for Nature Wildlife Conservation Society-DR Congo Lukuru Wildlife Research Foundation Université de Kisangani Faculté des Sciences Laboratoire d'écologie et aménagement forestier Université de Kisangani Université de Kisangani Faculté des Sciences Agronomiques République Démocratique du Congo Ministère de l'Environnement et Développement Durable Aarhus University University of Copenhagen Escuela Politécnica Nacional del Ecuador Herbario Alfredo Paredes (QAP) Universidad Central del Ecuador Universidad Técnica Particular de Loja Grupo de Investigación en Biodiversidad Medio Ambiente y Salud-BIOMAS Universidad de las Américas, Campus Queri Keller Science Action Center The Field Museum, 1400 South Lake Shore Dr. Universidad Estatal Amazónica Facultad de Ingeniería Ambiental Universidad Tecnica del Norte Herbario Nacional del Ecuador Grupo de Ecosistemas Tropicales y Cambio Global Universidad Regional Amazónica ikiam Colegio de Ciencias Biológicas y Ambientales COCIBA & Extensión Galápagos Universidad San Francisco de Quito-USFQ Herbario de Botánica Económica del Ecuador QUSF Universidad San Francisco de Quito USFQ Galapagos Science Center USFQ UNC Chapel Hill University of North Carolina-UNC Chapel Hill University of Florida FindingSpecies Mekelle University Environment Climate Change and Coffee Forest Forum (ECCCFF) University of Turku Centre de coopération International en Recherche Agronomique pour le Développement (CIRAD) CNRS ONF INRAE Centre National de la Recherche Scientifique AMAP Univ Montpellier IRD CNRS CIRAD INRA Forêts et Sociétés (F&S) Centre de coopération International en Recherche Agronomique pour le Développement (CIRAD) Departement Hommes Natures Societes Museum national d'histoire naturelle INRA Cirad UMR Ecologie des Forêts de Guyane (AgroparisTech CNRS INRAE Université des Antilles Université de la Guyane) Ministry of Forests Seas Environment and Climate Rougier-Gabon Agence Nationale des Parcs Nationaux Gabon Commission of Central African Forests (COMIFAC) Agence Nationale des Parcs Nationaux Ministère des Forêts des Eaux de la Mer de l'Environnement Chargé du Plan Climat des Objectifs de Développement Durable et du Plan d'Affectation des Terres Institut de Recherche en Ecologie Tropicale (CENAREST) Gabon/Agence Nationale des Parcs Nationaux Georg-August-University Göttingen University of Freiburg Institute of Botany University of Hohenheim Max Planck Institute for Chemistry Forestry Research Institute of Ghana (FORIG) Mensuration Unit Forestry Commission of Ghana Center for International Forestry Research Iwokrama International Centre for Rainforest Conservation and Development Guyana Forestry Commission Utrecht University Centre for Sustainable Technologies Indian Institute of Science Centre for International Forestry Research (CIFOR) Herbarium Borgoriense Indonesian Institute of Sciences (LIPI) Indonesian Institute of Science Forest Research and Development Agency (FORDA) Balitek-KSDA Samboja University of Florence and MUSE - Museo delle Scienze Cirad Hokkaido University Graduate School of Agriculture Kyoto University Forestry Development Authority of the Government of Liberia (FDA) University of Liberia Sungai Wain Protection Forest South East Asia Rainforest Research Partnership Danum Valley Field Centre Malaysian Palm Oil Board Sabah Forestry Department Forest Research Centre Universiti Malaysia Sabah Sabah Forestry Department Sarawak Forestry Corporation Eduardo Mondlane University Herbarium UNAN-Leon Universidad Nacional Autónoma de Nicaragua University of Abeokuta Natural History Museum of Norway University of Oslo Norwegian University of Life Sciences Universidad Nacional de la Amazonía Peruana (UNAP) Universidad Nacional de Jaén Jardin Botanico de Missouri Andes to Amazon Biodiversity Program Universidad Nacional de San Agustín de Arequipa Facultad de Ciencias Biológicas Universidad Nacional de la Amazonía Peruana Kené - Instituto de Estudios Forestales y Ambientales Instituto de Investigaciones de la Amazonia Peruana (IIAP) Universidad Nacional Jorge Basadre de Grohmann (UNJBG) Universidad Nacional de San Antonio Abad del Cusco Centro de Conservación Investigación y Manejo CIMA Pontificia Universidad Católica del Perú Asociacion Bosques Perú Université Officielle de Bukavu Université Marien N'Gouabi Wildlife Conservation Society Ecole Nationale Supérieure d'Agronomie et de Foresterie Université Marien Ngouabi Univeriste Marien Ngouabi The Gola Rainforest National Park Department of Geography National University of Singapore Departamento de Biología y Geología Física y Química inorgánica Universidad Rey Juan Carlos Real Jardín Botánico – CSIC Departamento de Biología Área de Botánica Universidad Autónoma de Madrid Museo Nacional de Ciencias Naturales (MNCN-CSIC) Centre for Agricultural Research in Suriname (CELOS) Stockholm Environment Institute Department of Plant Ecology and Evolution Uppsala University Southern Swedish Forest Research Centre InfoFlora Conservatoire et Jardin Botanique Geneve National Chung Hsing University Sokoine University of Agriculture Naturalis Biodiversity Center Wageningen University Forest Ecology and Forest Management Group Tropenbos International Institute for Biodiversity and Ecosystem Dynamics University of Amsterdam Bureau Waardenburg BV Van Hall Larenstein University of Applied Sciences Van der Hout Forestry Consulting Utrecht University, Domplein 29 Wageningen University Plant Ecology and Nature Conservation Group Data for Sustainability Department of Zoology Entomology & Fisheries Sciences Makerere University The Institute of Tropical Forest Conservation (ITFC) Mbarara University of Science and Technology (MUST) George Washington University Makerere University Department of Forestry Biodiversity and Tourism Makerere University University of Stirling University of Kent School of Geography University of Leeds UK Centre of Ecology & Hydrology Lancaster University University of Oxford The Landscapes and Livelihoods Group (TLLG) Overseas Development Institute Manchester Metropolitan University University of Aberdeen University of Exeter School of GeoSciences University of Edinburgh University of Cambridge Department of Environment and Geography University of York Department of Geography University College London Imperial College School of Geography Earth & Environmental Sciences Birmingham Institute of Forest Research University of Birmingham University of Plymouth Geography College of Life and Environmental Sciences University of Exeter Lancaster Environment Centre Lancaster University University of Edinburgh School of Biology University of Leeds Royal Botanic Garden Edinburgh CENAREST & ANPN & Stirling University University of Bristol School of Biological Sciences Department of Plant Sciences University of Cambridge Living with Lake Centre Laurentian University Royal Botanic Gardens Kew The Royal Society for the Protection of Birds centre for Conservation Science Environmental Change Institute School of Geography and the Environment University of Oxford UK Centre for Ecology & Hydrology School of Geography and the Environment University of Oxford The Royal Botanic Gardens Department of Geography and Environmental Science University of Dundee School of Biological Sciences University of Southampton University of East Anglia Stirling University School of Earth and Environment University of Leeds Department of Plant & Soil Science School of Biological Sciences University of Aberdeen, Cruickshank Building Institute for Transport Studies University of Leeds UK Research & Innovation University of Nottingham University of Bangor Center for Tropical Research Institute of the Environment and Sustainability University of California Center for Tropical Conservation Nicholas School of the Environment Duke University Ecology and Evolutionary Biology University of Michigan Saint Louis Zoo Department of Organismic and Evolutionary Biology Harvard University Center for Global Discovery and Conservation Science Arizona State University Wildlife Conservation Society – Programme Congo Woods Hole Research Center The University of Michigan Herbarium Nicholas School of the Environment National Park Service University of California ForestGEO Smithsonian Tropical Research Institute University of Texas at Austin Smithsonian Institute Washington University in Saint Louis Center for Conservation and Sustainable Development at the Missouri Botanical Garden Smithsonian Tropical Research Institute Smithsonian Institution Forest Global Earth Observatory (ForestGEO) Forest Global Earth Observatory (ForestGEO) Smithsonian Tropical Research Institute George Mason University Missouri Botanical Garden Broward County Parks and Recreation Nova Southeastern University Science and Education The Field Museum Department of Biology Boston University Wake Forest University Department of Geographical Sciences University of Maryland San Diego Zoo Institute for Conservation Research Biology Department Washington State University Yale School of Forestry & Environmental Studies Columbia University Department of Environmental Science Policy and Management University of California Berkeley School of Earth Sciences and Environmental Sustainability Northern Arizona University Department of Geography and the Environment University of Texas at Austin UNELLEZ-Guanare Programa de Ciencias del Agro y el Mar Herbario Universitario (PORT) Ci Progress GreenLife Universidad Nacional Experimental de Guayana Instituto Venezolano de Investigaciones Científicas (IVIC) Universidad de los Andes Viet Nature Conservation Centre CIRAD School of Life Sciences University of Lincoln UNESP - São Paulo State University Instituto de Biociências Universidade Estadual Paulista Gordon and Betty Moore Foundation: 1656 FAPESP: 2012/51509-8 FAPESP: 2012/51872-5 Fundação de Amparo à Pesquisa do Estado de Goiás: 2017/10267000329 European Research Council: 291585 Gordon and Betty Moore Foundation: 5349 European Research Council: 758873 Belgian Federal Science Policy Office: BR/132/A1/AFRIFORD Belgian Federal Science Policy Office: BR/143/A3/HERBAXYLAREDD Vlaamse Interuniversitaire Raad: CD2018TEA459A103 CNPq: CNPq/PPBio/457602/2012-0 National Science Foundation: DEB 1754647 Natural Environment Research Council: E/M0022021/1 Royal Society: ICA/R1/180100 Natural Environment Research Council: NE/D005590/1 European Research Council: NE/F005806/1 Natural Environment Research Council: NE/F005806/1 FAPESP: NE/K016431/1 Natural Environment Research Council: NE/N004655/1 FAPESP: NE/N012542/1 Royal Society: NE/P008755/1 FAPESP: NE/S011811/1 National Geographic Society: NE/T01279X/1 CNPq: PELD/441244/2016-5 Belgian Federal Science Policy Office: SD/AR/01A/COBIMFO

La forêt du haut massif du Mont-Liban, entre 1400 et 3086 mètres d'altitude, renferme la plus grande masse forestière de ce pays. Cependant, sous l'emprise des multiples besoins des riverains, le milieu forestier a été fragilisé et sa surface réduite. Les déboisements ont livré les versants fragiles à l'érosion hydrique. La combinaison des photos aériennes et des images satellitaires multi-dates permettent une analyse diachronique du paysage forestier ainsi qu'une description synthétique de l'organisation et de la répartition spatiale de ces formations végétales. L'interprétation des résultats, qui doit tenir compte de l'interaction entre l'Homme et son environnement, révèle une régression des surfaces forestières entre 1962 et 1984 et une progression sur les périodes 1984-2000 et 2000-2018. The forest of the hight Mount Lebanon massif, at altitudes between 1400 and 3086 meters, holds the largest forest extent in Lebanon. However, under the pressure of meeting local residents' needs, the forest gradually lost its density, causing the disappearance of this landscape. Deforestation has exposed fragile slopes to water erosion. The effects of deforestation have the direct impact of exposing fragile slopes to water erosion. The combination of aerial photographs and multi-date satellite images allows for a diachronic analysis of the forest landscape as well as a synthetic description of the organization and spatial distribution of these tree formations. Interpreting the results, that should account for the interaction between people and their environment, revealed a decline in the forest area between the years 1962-1984, while an increase is marked in the two periods 1984-2000 and 2000-2018.

Three decades of satellite observations provide unprecedented information about forest change trajectories in the humid tropics., Accurate characterization of tropical moist forest changes is needed to support conservation policies and to quantify their contribution to global carbon fluxes more effectively. We document, at pantropical scale, the extent and changes (degradation, deforestation, and recovery) of these forests over the past three decades. We estimate that 17% of tropical moist forests have disappeared since 1990 with a remaining area of 1071 million hectares in 2019, from which 10% are degraded. Our study underlines the importance of the degradation process in these ecosystems, in particular, as a precursor of deforestation, and in the recent increase in tropical moist forest disturbances (natural and anthropogenic degradation or deforestation). Without a reduction of the present disturbance rates, undisturbed forests will disappear entirely in large tropical humid regions by 2050. Our study suggests that reinforcing actions are needed to prevent the initial degradation that leads to forest clearance in 45% of the cases.

International audience; The ForestAtRisk Python package can be used to model the spatial probability of deforesta-8tion and predict future forest cover in the tropics. The spatial data used to model deforestation9comes from georeferenced raster files which can be very large (several gigabytes). The func-10tions available in theForestAtRiskpackage process large rasters by blocks of data, making11calculations fast and efficient. This allows deforestation to be modeled over large geographic 12 areas (eg. at the country scale) and at high resolution (eg.30 m). TheForestAtRisk13package offers the possibility of using a logistic regression with auto-correlated spatial random14effects to model the deforestation process. The spatial random effects make it possible to15structure the residual spatial variability in the deforestation process which is not explained by16the variables of the model and is often very large. In addition to providing new features, the17ForestAtRiskPython package is open source (GPLv3 license), cross-platform and scriptable18(via Python), user-friendly (functions provided with full documentation and examples), and19easily extendable (with statistical models for example). The Python package ForestAtRisk20was recently used to model deforestation and predict future forest cover by 2100 across the humid tropics

Made available in DSpace on 2022-04-28T17:20:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 French Space Study Center (CNES, TOSCA 2020 project) National Research Institute for Agriculture, Food, and the Environment (INRAE) Over the past two decades spaceborne LiDARsystems have gainedmomentumin the remote sensing community with their ability to accurately estimate canopy heights and aboveground biomass. This article aims at using the most recent global ecosystem dynamics investigation (GEDI) LiDAR system data to estimate the stand-scale dominant heights (H-dom), and stand volume (V) of Eucalyptus plantations in Brazil. These plantations provide a valuable case study due to the homogenous canopy cover and the availability of precise field measurements. Several linear and nonlinear regression models were used for the estimation of H-dom and V based on several GEDI metrics. H-dom and V estimation results showed that over low-slopped terrain the most accurate estimates of H-dom and V were obtained using the stepwise regression, with an root-mean-square error (RMSE) of 1.33m(R-2 of 0.93) and 24.39 m(3).ha(-1) (R-2 of 0.90) respectively. The principal metric explaining more than 87% and 84% of the variability (R-2) of H-dom and V was the metric representing the height above the ground at which 90% of the waveform energy occurs. Testing the postprocessed GEDI metric values issued from six available different processing algorithms showed that the accuracy on H-dom and V estimates is algorithm dependent, with a 16% observed increase in RMSE on both variables using algorithm a5 vs. a1. Finally, the choice to select the ground return from the last detected mode or the stronger of the last two modes could also affect the H-dom estimation accuracy with 12 cm RMSE decrease using the latter. Univ Montpellier, French Natl Res Inst Agr Food & Environm INRAE, AgroParisTech, CIRAD,CNRS,TETIS, F-34093 Montpellier, France UNESP, Fac Ciencias Agron, BR-18610034 Botucatu, SP, Brazil Suzano SA, BR-13465970 Limeira, Brazil Univ Montpellier, LISAH, Inst Agro, INRAE,IRD, F-34060 Montpellier, France IRD, CNRS, UPS, Ctr Study Biosphere Space,CNES,INRAE, F-31401 Toulouse, France CIRAD, UMR Eco & Sols, F-34398 Montpellier, France IRD, INRA, CIRAD, Eco & Sols, Montpellier, France Univ Montpellier, SupAgro, F-34060 Montpellier, France UNESP, Fac Ciencias Agron, BR-18610034 Botucatu, SP, Brazil

International audience; Degraded tropical forests dominate agricultural frontiers and their management is becoming an urgent priority. This calls for a better understanding of the different forest cover states and cost-efficient techniques to quantify the impact of degradation on forest structure. Canopy texture analyses based on Very High Spatial Resolution (VHSR) optical imagery provide proxies to assess forest structures but the mechanisms linking them with degradation have rarely been investigated. To address this gap, we used a lightweight Unmanned Aerial Vehicle (UAV) to map 739 ha of degraded forests and acquire both canopy VHSR images and height model. Thirty-three years of degradation history from Landsat archives allowed us to sample 40 plots in undisturbed, logged, over-logged and burned and regrowth forests in tropical forested landscapes (Paragominas, Pará, Brazil). Fourier (FOTO) and lacunarity textures were used to assess forest canopy structure and to build a typology linking degradation history and current states. Texture metrics capture canopy grain, heterogeneity and openness gradients and correlate with forest structure variability (R2 = 0.58). Similar structures share common degradation history and can be discriminated on the basis of canopy texture alone (accuracy = 55%). Over-logging causes a lowering in forest height, which brings homogeneous textures and of finer grain. We identified the major changes in structures due to fire following logging which changes heterogeneous and intermediate grain into coarse textures. Our findings highlight the potential of canopy texture metrics to characterize degraded forests and thus be used as indicators for forest management and degradation mitigation. Inexpensive and agile UAV open promising perspectives at the interface between field inventory and satellite characterization of forest structure using texture metrics.

International audience; Almost half of the total organic carbon (C) in terrestrial ecosystems is stored in forest soils. By altering rates of input or release of C from soils, forest management activities can influence soil C stocks in forests. In this review, we synthesize current evidence regarding the influences of 13 common forest management practices on forest soil C stocks. Afforestation of former croplands generally increases soil C stocks, whereas on former grasslands and peatlands, soil C stocks are unchanged or even reduced following afforestation. The conversion of primary forests to secondary forests generally reduces soil C stocks, particularly if the land is converted to an agricultural land-use prior to reforestation. Harvesting, particularly clear-cut harvesting, generally results in a reduction in soil C stocks, particularly in the forest floor and upper mineral soil. Removal of residues by harvesting whole-trees and stumps negatively affects soil C stocks. Soil disturbance from site preparation decreases soil C stocks, particularly in the organic top soil, however improved growth of tree seedlings may outweigh soil C losses over a rotation. Nitrogen (N) addition has an overall positive effect on soil C stocks across a wide range of forest ecosystems. Likewise, higher stocks and faster accumulation of soil C occur under tree species with N-fixing associates. Stocks and accumulation rates of soil C also differ under different tree species, with coniferous species accumulating more C in the forest floor and broadleaved species tending to store more C in the mineral soil. There is some evidence that increased tree species diversity could positively affect soil C stocks in temperate and subtropical forests, but tree species identity, particularly N-fixing species, seems to have a stronger impact on soil C stocks than tree species diversity. Management of stand density and thinning have small effects on forest soil C stocks. In forests with high populations of ungulate herbivores, reduction in herbivory levels can increase soil C stocks. Removal of plant biomass for fodder and fuel is related to a reduction in the soil C stocks. Fire management practices such as prescribed burning reduce soil C stocks, but less so than wildfires which are more intense. For each practice, we identify existing gaps in knowledge and suggest research to address the gaps.

Tropical cyclones (TCs) are large‐scale disturbances that regularly impact tropical forests. Although long‐term impacts of TCs on forest structure have been proposed,a global test of the relationship between forest structure and TC frequency and intensity is lacking. We test on a pantropical scale whether TCs shape the structure of tropical and subtropical forests in the long term. We compiled forest structural features (stem density, basal area, mean canopy height and maximum tree size) for plants ≥10 cm in diameter at breast height from published forest inventory data (438 plots ≥0.1 ha, pooled into 250 1 × 1‐degree grid cells) located in dry and humid forests. We computed maps of cyclone frequency and energy released by cyclones per unit area (power dissipation index,PDI) using a high‐resolution historical database of TCs trajectories and intensities.We then tested the relationship between PDI and forest structural features using multivariate linear models, controlling for climate (mean annual temperature and water availability) and human disturbance (human foot print). Forests subject to frequent cyclones (at least one TCs per decade) and high PDI exhibited higher stem density and basal area, and lower canopy heights. However,the relationships between PDI and basal area or canopy height were partially masked by lower water availability and higher human foot print in tropical dry forests. Synthesis. Our results provide the first evidence that tropical cyclones have a long term impact on the structure of tropical and subtropical forests in a globally consistent way. The strong relationship between power dissipation index and stem density suggests that frequent and intense tropical cyclones reduce canopy cover through defoliation and tree mortality, encouraging higher regeneration and turnover of biomass. The projected increase in intensity and pole ward extension of tropical cyclones due to anthropogenic climate change may therefore have important and lasting impacts on the structure and dynamics of forests in the future. Refereed/Peer-reviewed

International audience; Variations in crown forms promote canopy space-use and productivity in mixed-species forests. However, we have a limited understanding on how this response is mediated by changes in within-tree biomass allocation. Here, we explored the role of changes in tree allometry, biomass allocation and architecture in shaping diversity-productivity relationships (DPRs) in the oldest tropical tree diversity experiment. We conducted whole-tree destructive biomass measurements and terrestrial laser scanning. Spatially explicit models were built at the tree level to investigate the effects of tree size and local neighbourhood conditions. Results were then upscaled to the stand level, and mixture effects were explored using a bootstrapping procedure. Biomass allocation and architecture substantially changed in mixtures, which resulted from both tree-size effects and neighbourhood-mediated plasticity. Shifts in biomass allocation among branch orders explained substantial shares of the observed overyielding. By contrast, root-to-shoot ratios, as well as the allometric relationships between tree basal area and aboveground biomass, were little affected by the local neighbourhood. Our results suggest that generic allometric equations can be used to estimate forest aboveground biomass overyielding from diameter inventory data. Overall, we demonstrate that shifts in tree biomass allocation are mediated by the local neighbourhood and promote DPRs in tropical forests.

International audience; To fulfill their growth and reproductive functions, trees develop a three-dimensional structure that is subject to both internal and external constraints. This is reflected by the unique architecture of each individual at a given time. Addressing the crown dimensions and topological structure of large tropical trees is challenging considering their complexity, size and longevity. Terrestrial laser scanning (TLS) technology offers a new opportunity for characterizing and comparing these properties across a large number of individuals and species. In the present study, we specifically developed topology and geometry metrics of crown architecture from TLS data and investigated how they correlated with metrics of tree and crown form, crown position and shade tolerance. Fifty-nine trees belonging to 14 coexisting canopy species in semideciduous forests of Cameroon were scanned with TLS and reconstructed using quantitative structural models (QSMs). The species belonged to different shade-tolerance groups and were sampled in different crown positions. Crown-form metrics and branch topology metrics were quantified from the TLS data, and principal component analysis (PCA) was used to study how the 59 sampled trees were distributed along axes of architectural diversity. Allometric scaling parameters derived from West Brown and Enquist (WBE) metabolic theory were also quantified from the QSMs, and their correlations with the PCA axes were evaluated. The results revealed that the branch topology and crown-form metrics were not correlated since similar topologies could lead to contrasting crown forms. Crown form, but not branch topology, changed with tree shade tolerance, while convergence in tree topology and towards expected WBE parameters was observed for all trees reaching dominant crown positions independent of species shade tolerance. This convergence is interpreted as resulting from a liberation effect of canopy trees from side-shading constraints, leading to crown development processes through sequential reiteration.

Monitoring Vegetation Fraction Cover of French Mediterranean Forests for Evapotranspiration and Water Stress Mapping. ESA Living Planet Symposium 2019

Dans le cadre du processus REDD+, la République du Congo s’est lancée dans une étude relative à la connaissance de la situation antérieure et actuelle de son couvert forestier. Cinq produits cartographiques ont été réalisés à cet effet, présentant chacun des caractéristiques qui lui sont spécifiques. Ces produits, élaborés à des différentes dates, présentent des superficies forestières variables, entre 22 et 24 millions d’hectares. Les pertes par contre, présentant un taux annuel faible, variant entre 0,02% et 0,07%, placent la République du Congo dans la catégorie des pays à forte couverture forestière et un taux faible de déforestation. Ces produits cartographiques, d’auteurs différents ayant utilisé des méthodologies qui leurs sont propres, sont complémentaires et pertinents, et ont permis à la Républiques du Congo de poser des bases solides pour son système de suivi des forêts.

In understory trees, height–diameter allocation is subject several constraints: maximal height growth is limited, height growth is never null and, in terms of time dependency, diameter growth always precedes height growth. Understory trees experience a succession of canopy opening and closure events during their lifetime. Preferential allocation of their biomass to height or diameter growth is part of the acclimation process to their immediate environment. In this study, we investigated annual height and diameter increments in Fagus sylvatica understory trees submitted to canopy release. Annual height and diameter increments were obtained from retrospective stem analysis from the top of the tree to the stump on 39 understory trees. The relationship between height and diameter increments was investigated and temporal correlations among successive annual height and diameter increments were analyzed. An asymptotic relationship between annual height and diameter increment indicates that stem height growth was limited in understory trees. The intercept significantly differed from zero suggesting that height growth never stopped even when diameter growth was null. Following canopy release events, immediate diameter growth increase was observed while the height growth response was delayed, resulting in a time shift in the growth allocation strategy. Strong and asymmetric temporal correlations between annual height and diameter increments were observed: past annual diameter growth was positively correlated to present height growth. In understory trees, tree height is the main factor determining their potential growth since it determines their access to above-canopy light. However, the precedence of diameter growth over height growth suggests that tree growth is driven by diameter instead of height. This apparent discrepancy may be explained by the fact that, under closed canopy conditions, stem allometry reaches a functional threshold that forces tree to grow in diameter before growing in height.

Tree cover is a key variable for ecosystem functioning, and is widely used to study tropical ecosystems. But its determinants and their relative importance are still a matter of debate, especially because most regional and global analyses have not considered the influence of agricultural practices. More information is urgently needed regarding how human practices influence vegetation structure. Here we focused in Central Africa, a region still subjected to traditional agricultural practices with a clear vegetation gradient. Using remote sensing data and global databases, we calibrated a Random Forest model to correlatively link tree cover with climatic, edaphic, fire and agricultural practices data. We showed that annual rainfall and accumulated water deficit were the main drivers of the distribution of tree cover and vegetation classes (defined by the modes of tree cover density), but agricultural practices, especially pastoralism, were also important in determining tree cover. We simulated future tree cover with our model using different scenarios of climate and land-use (agriculture and population) changes. Our simulations suggest that tree cover may respond differently regarding the type of scenarios, but land-use change was an important driver of vegetation change even able to counterbalance the effect of climate change in Central Africa.

Thailand has undergone significant forest cover changes in recent decades, and this is likely to have altered the hydrological functioning of many watersheds; however, such potential impacts are not fully understood. To contribute towards a better understanding of the potential hydrological impacts of forest cover changes, this study examines the temporal trends of several hydrological indices in eight watersheds of Thailand over the period from 1982 to 2013. A number of hydrological indices (runoff coefficient, baseflow index, flow duration indices, streamflow elasticity, dryness index) were analysed using a combined Thiel–Sen/Mann–Kendall trend-testing approach, to assess the magnitude and significance of patterns in the observed data. These trend tests indicated that the change in the hydrological response of watersheds varied with the change in structure and composition of forest species. A significant increase in runoff (viz. average flow) was observed in those watersheds covered with natural forests, whereas a significant reduction in runoff (viz. baseflow and low runoff) was observed in those watersheds where the land cover was changed to Para rubber plantations and reforested areas. It is also noteworthy that the watersheds covered by natural forest showed more streamflow elasticity than plantations or reforested areas. These results highlight the importance of considering both forest types/dynamics and watershed characteristics when assessing hydrological impacts.

While high resolution spatial variables contribute to a good fit of spatially-explicit deforestation models, socio-economic processes are often beyond the scope of these models. Such a low level of interest in the socio-economic dimension of deforestation limits the relevancy of these models for decision making and may be the cause of their failure to accurately predict observed deforestation trends in the medium term. This study aims to propose a flexible methodology for taking into account multiple drivers of deforestation in tropical forested areas, where the intensity of deforestation is explicitly predicted based on socio-economic variables. By coupling a model of deforestation location based on spatial environmental variables with several sub-models of deforestation intensity based on socio-economic variables, we were able to create a map of predicted deforestation over the period 2001–2014 in French Guiana. This map was compared to a reference map for accuracy assessment, not only at the pixel scale but also over cells ranging from 1 to approx. 600 sq. km. Highly significant relationships were explicitly established between deforestation intensity and several socio-economic variables: population growth, the amount of agricultural subsidies, gold and wood production. Such a precise characterisation of socio-economic processes allows to avoid overestimation biases in high deforestation areas, suggesting a better integration of socio-economic processes in the models. While considering deforestation as a purely geographical process contributes to the creation of conservative models unable to effectively assess changes in the socio-economic and political contexts influencing deforestation trends, this explicit characterisation of the socio-economic dimension of deforestation is critical for the creation of deforestation scenarios in REDD+ projects. This article is protected by copyright. All rights reserved.