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The article presents the AMS (accelerator mass spectrometry) radiocarbon dating results of the Giant of Bevoay, which is a very large Grandidier baobab (Adansonia grandidieri Baill.) of Madagascar. The investigation of this baobab shows that it has a cluster structure, which consists of 3 perfectly fused stems. The calculated wood volume of the tree is 520 m3, which makes it the third largest Grandidier baobab and also the third largest individual of all Adansonia species. Two samples were collected from the outer part of the stems. The oldest dated sample segment had a radiocarbon date of 525 ± 23 BP, which corresponds to a calibrated age of 585 ± 10 years. According to this value, the Giant of Bevoay is 825 ± 50 years old.

International audience; Eucalyptus plantations are already planted in or expanding to water-limited regions with a high risk of severe drought. In future drier and more variable climate including extreme events, the ability of trees to recover after severe droughts emerges as a crucial for the sustainability of forest plantations. An original experiment involving 80% reduction in throughfall was set up in Brazil to gain insight into the responses of Eucalyptus grandis trees to prolonged (3-year) extreme water deficit and the ability of this species to recover following water stress. Our study focused on the changes in basal area, stem radius, and total height measured by high-temporal resolution dendrometers and periodical surveys of trees affected by 80% throughfall reduction (treatment group) and in a control group. The differences in basal area, stem radius, and total height growth rate were compared between groups over (i) 37 months of 80% throughfall reduction and (ii) 31 months following the end of 80% throughfall reduction. The correlations among growth rates, stem radius fluctuations, and meteorological variables in each group were determined to gain insights into the trees' responses to environmental conditions and stem water status.The 80% reduction in throughfall over 3 years significantly reduced tree growth rates by 73% in basal area and 95% in total height. However, under normal water availability following throughfall reduction, the basal area growth rate of water-stressed trees was 97% higher than that of the control trees while total height growth rate was only 8% higher. Despite the severe water stress, no tree mortality was observed. Trees recovered 51% of their basal area over the 31-month recovery period. In contrast, only 5% of total height was recovered.In the treatment group, rapid responses to variation in rainfall events were observed during the 80% throughfall reduction period. Also, correlations between stem radius fluctuations and vapor pressure deficit indicate increased transpiration following the end of throughfall reduction. These relationships indicate high conservation of the integrity of the xylem vascular system over the 3 years of 80% throughfall reduction, a key factor in the increased resilience of the trees. In the absence of tree mortality, our results suggest the 80% throughfall reduction had a severe impact on tree growth but demonstrate great recovery ability of Eucalyptus grandis trees in basal area growth following such a severe water deficit.

International audience; In tropical forests, the high proportion of trees showing irregularities at the stem base complicates forest monitoring. For example, in the presence of buttresses, the height of the point of measurement (HPOM) of the stem diameter (DPOM) is raised from 1.3 m, the standard breast height, up to a regular part of the stem. While DPOM is the most important predictor for tree aboveground biomass (AGB) estimates, the lack of harmonized HPOM for irregular trees in forest inventory increases the uncertainty in plot-level AGB stock and stock change estimates. In this study, we gathered an original non-destructive three-dimensional (3D) data set collected with terrestrial laser scanning and close range terrestrial photogrammetry tools in three sites in central Africa. For the 228 irregularly shaped stems sampled, we developed a set of taper models to harmonize HPOM by predicting the equivalent diameter at breast height (DBH′) from a DPOM measured at any height. We analyzed the effect of using DBH′ on tree-level and plot-level AGB estimates. To do so, we used destructive AGB data for 140 trees and forest inventory data from eight 1-ha plots in the Republic of Congo. Our results showed that our best simple taper model predicts DBH′ with a relative mean absolute error of 3.7% (R2 = 0.98) over a wide DPOM range of 17–249 cm. Based on destructive AGB data, we found that the AGB allometric model calibrated with harmonized HPOM data was more accurate than the conventional local and pantropical models. At the plot level, the comparison of AGB stock estimates with and without HPOM harmonization showed an increasing divergence with the increasing share of irregular stems (up to −15%). The harmonization procedure developed in this study could be implemented as a standard practice for AGB monitoring in tropical forests as no additional forest inventory measurements is required. This would probably lead to important revisions of the AGB stock estimates in regions having a large number of irregular tree stems and increase their carbon sink estimates. The growing use of three-dimensional (3D) data offers new opportunities to extend our approach and further develop general taper models in other tropical regions.

Over the past years, our research on baobabs mainly focused on the largest Malagasy species, namely the Reniala or Grandidier baobab (Adansonia grandidieri Baill.). The biggest A. grandidieri are located in the Morombe area, especially in the so-called Andombiry Forest. This giant forest of Reniala hosts well over 6000 mature individuals, out of which more than 30 have very large sizes, i.e., circumferences over 20 m. We investigated, measured and dated by AMS radiocarbon the largest specimens. We found that all large Grandidier baobabs are multi-stemmed. They mostly exhibit a closed ring-shaped structure, with a false cavity inside. In this architecture, which enables Grandidier baobabs to reach very large sizes, the stems that build the ring typically have similar ages. Here we present the AMS radiocarbon investigation of two large baobabs, A 215 (girth 21.50 m) and A 257 (girth 25.70 m). According to dating results, the baobab A 215 has an age of only 375 years. It consists of four fused stems and has a closed ring-shaped structure. The baobab A 257 has the second largest trunk of all known live Reniala trees. It also exhibits a closed ring-shaped structure, with five fused stems around a false cavity, which has an opening toward the exterior. The dating results indicate that A 257 is around 900 years old.

The article discloses the accelerator mass spectrometry (AMS) radiocarbon dating results of the Big Reniala of Isosa, which is a massive Grandidier baobab (Adansonia grandidieri Baill.) of Madagascar. The investigation of this baobab shows that it consists of 5 perfectly fused stems and exhibits a cluster structure. The calculated wood volume of the tree is 540 m 3 , which makes the Big Reniala of Isosa the largest individual of all Adansonia species and also the biggest known angiosperm in terms of volume. Several samples were collected from the outer part of the stems. The oldest dated sample had a radiocarbon date of 934 ± 24 BP, which corresponds to a calibrated age of 845 ± 25 years. This value indicates an age of 1000 ± 100 years for the big Reniala of Isosa.

International audience; Savanna is one of the main African ecosystems. The tree community in the savanna is a key element and provides many ecosystem services. Unmanned aerial vehicles (UAVs) combined with photogrammetric analysis are useful tools to produce accurate 3D maps, which, in turn, help describe the structure of the tree populations. The purpose of this study was to evaluate the use of commercial economical UAVs to assess tree characteristics in the savanna. A Dji Spark UAV was used to map 24 1-ha plots in northern Senegal. The images were processed using Pix4D software to produce a high-resolution canopy height model (CHM). A total of 239 trees were selected and their heights and crown areas were manually measured in the field. A strong correlation was found between UAV and field measurements with R2 = 0.84 for height and R2 = 0.93 for crown area. Based on tree canopy colours and tree morphologies measured by UAV, it was possible to predict tree species with an error rate of 20%, using a random forest classification. This study thus confirms the possibility of using low-cost UAVs to assess tree structures in the savanna not only for research on tree communities in savanna, but also by forestry agencies to inform stakeholders.

Common allometric patterns have been reported across the tropics and good performance on independent data was retrieved for the most recent pantropical model predicting tree aboveground biomass (AGB) from stem diameter, wood density and total height. General models are undoubtedly useful for the estimation and monitoring of biomass and carbon stocks in tropical forests, however specific allometry, allocation, and traits, are at the core of many models of vegetation dynamics, and there is lack of such information for some regions and species. In this study, we specifically evaluated how size-dependent changes in above-ground biomass and biomass allocation to crown relate to other allometric and life-history traits for tropical tree species. We gathered destructive data available in eight terra firme forest sites across central Africa and the combined dataset consisted of 1,023 trees belonging to 54 tropical tree species phylogenetically dispersed, with only two congeneric species. A huge body of field and laboratory measurements was used for computing AGB and crown mass ratio (CMR) at the tree level, and to derive key allometric traits at the species level. For the latter, species-specific relationships between tree diameter and total height, crown exposure to light, wood density, and bark thickness were fitted for 50 species. Our results show interspecific variation in the relationships relating tree diameter to both AGB and CMR, and including species traits in a multi-specific AGB model confirmed that interspecific variation in biomass allometry is primarily determined by species wood density. We also showed that the allocation of biomass to crown increases linearly with tree diameter for most species, and that interspecific variation in the CMR model is associated with the species dispersal mode and maximum height. Trait covariations among our set of tropical tree species widespread and/or locally abundant in central Africa, revealed a continuum between large-statured species, which tended to be light-demanding, deciduous and wind-dispersed, and species with opposite attributes. Information on allometry, allocation, and traits provided here could further be used in comparative ecology and for parameterizing dynamic and succession models. Also importantly, the species-specific AGB models fitted for major tree species, including most timber species of central Africa, will help improve biomass estimates.

The argan tree is well adapted to drought conditions in Algerian western Sahara. The argan forest of Tindouf has a structure of coppice on stumps, characterized by an average height of 4.7m. Regeneration by dense resprouts represents 43% for 1,192 inventoried trees. The mother trees of Argania spinosa have a significant potential to resprout in coppice or suckers, thus forming crowns around mounds on beds of wadis. It should be noted that 21% of the trees are damaged by illegal cutting. The average spacing between the trees is around 13m. The argan tree retains a large volume of soil input with an average of 23.6 ± 36.3m3/ stump in the form of mounds. Linear regression analysis revealed an increasing relationship between mound volume and the number of stems per stump. Thanks to its powerful root system, the argan tree accumulates additional soil and contributes to the slow mechanism of sedimentation of micro-horizons, constituting mounds around the feet of trees., L’arganier est bien adapté aux conditions de sécheresse du Sahara occidental algérien. L’arganeraie de Tindouf a une structure dominée par les taillis sur souches, et caractérisée par une hauteur moyenne de 4,7 m. La régénération par rejets denses représente 43 % pour 1 192 pieds inventoriés. Les souches-mères d’Argania spinosa ont une potentialité importante de rejeter par les cépées ou par les drageons, formant ainsi des couronnes aux alentours des buttes sur lits d’oueds. Il est à signaler que 21 % des souches sont détériorées par les coupes illicites. L’écartement moyen entre les arbres est de l’ordre de 13 m. L’arganier retient un volume important de sol d’apport d’une moyenne de 23,6 ± 36,3 m3/ souche sous forme de buttes. L’analyse de régression linéaire a révélé une relation croissante entre le volume des buttes et le nombre de brins par souche. Grâce à son puissant système racinaire, l’arganier accumule des sols d’apport et contribue au mécanisme lent de sédimentation de micro-horizons en constituant des buttes aux pieds des arbres., Kechairi Réda. Structure élémentaire de l’arganeraie Argania spinosa L. Skeels de Tindouf (Sahara occidental algérien) / Elementary structure of the argan forest Argania spinosa L. Skeels of Tindouf (Algerian western Sahara). In: Ecologia mediterranea, tome 47 n°2, 2021. pp. 73-84.

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

Objectif : L’urbanisation dans les Pays en voie de développement se traduit par une croissance démographique galopante avec pour corollaire la dégradation de la végétation dans les espaces urbains et péri-urbains. Le présent article s’intéresse particulièrement à l’analyse de la diversité spécifique, de la structure des arbres et du boisement dans les concessions de la ville de Parakou. Méthodologie et résultats : Sur la base d’un échantillonnage raisonné, un inventaire floristique suivi d’une observation sur le nombre d’arbre par concession a été fait dans 140 placettes. Les résultats montrent que 30,32 % des concessions sont dépourvues d’arbre, 21,64 % comptent 1 arbre et 48,04 % comptent 2 arbres et plus. La richesse spécifique est de 94 espèces dont 77 espèces exotiques et 17 espèces locales réparties dans 37 familles. Le peuplement est dominé par l’espèce Mangifera indica. La densité moyenne est de 18 pieds/ha. La distribution selon les classes de diamètre montre une abondance des individus dans la classe de 10 à 30 cm. Conclusion et application des résultats : Il ressort de ces résultats que les concessions de la ville de Parakou sont peu boisées et pauvres en espèces locales et à grand diamètre. Ces résultats suscitent des recherches sur l’importance et les contraintes liées à la plantation des arbres dans le milieu urbain. Par ailleurs cela montre aux gestionnaires de la ville de Parakou, l’urgence de la vulgarisation et l’application des lois qui encadrent la plantation, la conservation et la protection des arbres dans les concessions et les domaines privés de Parakou et au Bénin. Mots clés : Villes de Parakou (Bénin), concessions, arbres, diversité, dendrométrie Zohoun et al., J. Appl. Biosci. 2020 Diversité, structure des arbres et description du boisement dans les concessions de l’espace urbain de Parakou au centre du Bénin 15843 ABSTRACT Diversity, tree structure and description of afforestation in the grants of the urban area of Parakou in central Benin Objective: Urbanization in developing countries results in galloping demographic growth with as a corollary, the degradation of vegetation in urban and peri-urban areas. This article focuses on the analysis of the specific diversity, tree structure and afforestation in the grants of the city of Parakou. Methodology and results: By sampling method, a floristic inventory followed by an observation of the number of trees per grant was made in 140 plots. The results show that 30.32% of the grants have no trees, 21.64% have 1 tree and 48.04% have 2 or more trees. The specific wealth is 94 species, of which 77 species are exotic and 17 local species, distributed among 37 families. The population is dominated by the Mangifera indica species. The average density is 18 plants/ha. The distribution according to diameter classes shows an abundance of individuals in the class of 10 to 30 cm. Conclusion and application of results: It appears from these results that the grants in the town of Parakou are sparsely forested and poor in local and large-diameter species. These results prompt research on the importance of and constraints to tree planting in the urban area. Moreover, it shows the managers of the city of Parakou the urgency of the extension and application of laws that govern the planting, conservation and protection of trees in the grants and the private domains of Parakou and in Benin. Key words: City of Parakou (Benin), grants, trees, diversity, dendrometry

National audience; Depuis le maximum démographique du milieu du XIX siècle, les milieux montagnards connaissent des mutations très rapides liées aux impacts conjoints de la déprise agro-sylvo-pastorale et du réchauffement climatique. Dans l’observatoire Homme-Milieu Pyrénées-Haut Vicdessos, le caractère marginal des activités pastorales durant la phase de plein emploi liée à l’activité industrielle (XX° siècle) interfère avec la hausse des températures moyennes pour expliquer la fermeture rapide des paysages observée depuis le milieu du XX° siècle. Celle-ci se traduit par une afforestation rapide des versants dès la fin des années 1950. Dans ce contexte, sur la base d’une approche dendrochronologique mise en œuvre conjointement sur les peuplements forestiers de haute altitude mais également sur les ligneux bas, notre étude vise à (1) caractériser les patrons spatio-temporels de la recolonisation ligneuse avec une résolution annuelle par la datation - au moyen de méthodes dendrochronologiques - des ligneux hauts et bas ; (2) cerner l’influence de la déprise agro-sylvo-pastorale dans la dynamique de recolonisation ; (iii) mettre en évidence l’impact des fluctuations climatiques sur l’expansion et la croissance radiale des ligneux. Pour cela, plusieurs individus de rhododendrons, genévriers et pins ont été prélevés, datés et analysés.Nos résultats mettent en évidence que les ligneux haut et bas ont colonisé quasi simultanément le versant échantillonné en accord avec le pic de colonisation en 1950 mis en évidence par les études polliniques. La comparaison cerne-climat révèle que les genévriers sont plus sensibles aux températures estivales que les pins, ces deux espèces bénéficiant largement de la hausse des températures. Les ligneux bas, contrairement aux arbres, sont sensibles à l’enneigement, une date de déneigement tardive impactant négativement leur croissance. Cependant, le rhododendron se montre beaucoup moins sensible au climat régional mais est probablement davantage impacté par le microclimat et par les événements extrêmes de sécheresse ou de gel. Des résultats préliminaires issus d’analyses dendrométriques et microclimatiques montrent qu’à quelques mètres de distances, les conditions microclimatiques différent significativement ainsi que la croissance radiale des individus de rhododendrons instrumentés.

Accurate estimates of commercial volume in tropical forests are key for the implementation of sustainable forest management plans. Because of the lack of local or generic volumetric equations, most forest managers and forestry services are still using traditional expansion factors (i.e., multiplication of the diameter by a given value) to estimate the volume of commercial tree species in the Amazon. Volumetric models were developed through a unique data set of 1,264 fallen trees fully measured in 150 sample plots located across a broad range of forests in Amapá, Brazil. Forest-specific volumetric models were developed and compared with a generic (i.e., across all forests) model and with published equations developed elsewhere in the Amazon. The generic equation performed well in all forest types and allowed precise predictions. The most efficient sampling design to develop volumetric models consists of measuring approximately 50 trees across four different size classes representing the whole population. The form factors (FF) developed locally generated substantial bias but performed better than the traditional FF (0.7). Overall, our results suggest that it is possible to develop accurate generic models to estimate commercial timber volume, and this study can serve as a guideline for forest managers or scientists interested in calibrating volumetric models in a cost-efficient way. Study Implications: This work provides useful information on volumetric modeling methods for Brazilian Amazon tropical forests. Most of the studies in the literature only investigate the classical modeling using regression models considering only boom metrics with or without bark, and, in this way, they provide incomplete and biased total knowledge and estimates for a given population. Therefore, detailed and accurate analyzes are crucial tools for decisionmaking. If the harvesting interventions are carried out without considering the most appropriate method to estimate the total wood stock, there may be damages or even extinction of some species, as has happened with other forest domains in Brazil and in other rainforest regions in the world. In this work, the results clearly show the importance of testing different methodologies and selecting the one best suited for a particular site, as well as carrying out techniques for the sustainable and correct management of the forest. Because the analysis procedures provide only information on how methodologies behave statistically, our results may contribute to a more refined analysis to be applied in the future in similar environments. Currently, the Brazilian forestry sector is looking for alternatives to obtain forest resources within the concept of sustainability. For the Brazilian Amazon tropical forest domain, it is extremely important to achieve a sustainable management of resources through forest management. Most studies in the literature investigate the management of tropical rainforest, whereas there is a lack of scientific information on the transition range for the cerrado. Made available in DSpace on 2020-12-16T09:06:50Z (GMT). No. of bitstreams: 1 CPAF-AP-2020-Accurate-estimation-of-commercial.pdf: 928769 bytes, checksum: dff30beaa41574825f8df54580bc8d84 (MD5) Previous issue date: 2020

International audience; Dieback of Atlas cedars is a complex phenomenon that has been affecting the cedar forests of the Aurès mountains and Theniet El Had since the 1980s. Its causes are still unknown. This study focused on the cedar forest of Theniet El Had in order to gain a better understanding of the way Atlas cedar dieback is evolving over time and space and to establish whether it has any relationship with environmental factors. Two approaches were applied. In the first, a spatial approach, the distribution of affected trees was mapped out according to altitude, slope, exposure, dendrometric parameters (diameter and height) and state of health (percentage of defoliation). In the temporal approach, radial growth rates were compared between affected and healthy trees in six ecological stations that were representative of Atlas cedar stands in the study zone. The results show that dieback is more severe in the Theniet El Had forest towards its lower limits in steeply sloping low-altitude stations exposed to sunlight and heat. Dieback is advanced and affects adult and/or aging trees. The trees affected stand out for their poor growth and very high average sensitivity to climatic factors. The prolonged drought in the region from 1980 to 2002 has exacerbated the effects of aging, which has affected and worsened the state of health of the Atlas cedars. These results point to the urgency of undertaking sylvicultural work to improve the health of these stands and to establish sampling plots.; El agostamiento del cedro del Atlas en Argelia es un fenómeno complejo que ha afectado a los cedrales de Aurès y Theniet El Had desde los años 1980, y cuyas causas todavía son desconocidas. Para comprender mejor la evolución espaciotemporal del agostamiento del cedro del Atlas y establecer una eventual relación con los factores del medio, nuestro trabajo se ha focalizado en elcedral de Theniet El Had. Este estudio se basa en dos enfoques. Uno, espacial, inventaría la repartición de los árboles agostados según la altitud, la pendiente, la exposición, así como sus parámetros dendrométricos (diámetro, altura) y su estado de salud (tasa de defoliación). El otro, temporal, compara la evolución del crecimiento radial de los árboles agostados y de los árboles sanos en seisestaciones ecológicas representativas de las masas de cedro del Atlas en la zona de estudio. Los resultados muestran que el fenómeno de agostamiento del cedro del Atlas ha afectado más al cedral de Theniet El Had hacia su límite inferior, en estaciones situadas a baja altitud, en terrenos de fuerte pendiente y con exposiciones soleadas y cálidas. Este fenómeno se presenta en un estado avanzado, y los árboles agostados son árboles adultos y/o viejos. Los árboles agostados se distinguen por un débil crecimiento y una sensitividad media al clima muy elevada. Además del efecto de la edad, la sequía prolongada en la región durante el período 1980-2002 afectó y agravó el estado de salud del cedro del Atlas. Estos resultados ponen al día la urgencia de emprender tareas silvícolas para mejorar el estado de salud de las masas e implementar un dispositivo de vigilancia de la salud del cedro.; Le dépérissement du cèdre de l’Atlas en Algérie est un phénomène complexe qui a affecté les cédraies des Aurès et Theniet El Had depuis les années 1980, et dont les causes restent inconnues. Pour mieux comprendre l’évolution spatio-temporelle du dépérissement du cèdre de l’Atlas et établir une éventuelle relation avec les facteurs du milieu, notre travail s’est focalisé sur la cédraie de Theniet El Had. Ce travail est basé sur deux approches. L’une, spatiale, recense la répartition des arbres dépéris selonl’altitude, la pente, l’exposition, ainsi que leurs paramètres dendrométriques (diamètre, hauteur) et leur état de santé (taux de défoliation). L’autre, temporelle, compare l’évolution de la croissance radiale des arbres dépéris et des arbres sains dans six stations écologiques représentatives des peuplements de cèdre de l’Atlas dans la zone d’étude. Les résultats montrent que le phénomène de dépérissement du cèdre de l’Atlas a davantage marqué la cédraie de Theniet El Had vers sa limite inférieure, dans des stations situées à basse altitude, sur des terrains à forte pente et aux expositions ensoleillées et chaudes. Ce phénomène se présente dans un étatavancé, et les arbres dépéris sont desarbres adultes et/ou âgés. Les arbresdépéris se distinguent par une faiblecroissance et une sensitivité moyenneau climat très élevée. En plus de l’effetde l’âge, la sécheresse prolongée dans larégion au cours de la période 1980-2002a affecté et aggravé l’état de santé ducèdre de l’Atlas. Ces résultats mettent aujour l’urgence d’entreprendre des travauxsylvicoles pour améliorer l’état de santédes peuplements et de mettre en placeun dispositif de surveillance de la santédu cèdre.

During winter, trees have to cope with harsh conditions, including extreme freeze-thaw stress. The present study focused on ice nucleation and propagation, related water shifts and xylem cavitation as well as cell damage, and was based on in situ monitoring of xylem (thermocouples) and surface temperatures (infrared imaging), ultrasonic emissions and dendrometer analysis. Field experiments during late winter on Picea abies growing at the alpine timberline revealed three distinct freezing patterns: (i) from the top of the tree towards the base, (ii) from thin branches towards the main stem’s top and base, and (iii) from the base towards the top. Infrared imaging showed freezing within branches from their base towards distal parts. Such complex freezing causes dynamic and heterogeneous patterns in water potential and probably in cavitation. This study highlights the interaction between environmental conditions upon freezing and thawing and demonstrates the enormous complexity of freezing processes in trees. Diameter shrinkage, which indicated water fluxes within the stem, and acoustic emission analysis, which indicated cavitation events near the ice front upon freezing, were both related to minimum temperature, and upon thawing, related to vapor pressure deficit and soil temperature. These complex patterns, emphasizing the common mechanisms between frost and drought stress, shed new lights on understanding winter tree physiology.

L’observation de la dynamique des milieux naturels et anthropisés à partir de l’espace connaît de profonde évolution grâce aux nouveaux capteurs embarqués à bord des satellites, de l’accès facilité aux données et de la constante progression de leur qualité en termes de résolutions spatiales, spectrales et temporelles. Ces nouveaux flux d’informations ouvrent des perspectives innovantes dans la détection de phénomènes qui s’inscrivent dans l’espace et dans le temps, ainsi que dans la mise en place de dispositifs de suivi/surveillance de type observatoire. Ces journées ont rassemblé des partenaires européens et du Sud qui s’engagent dans le CES Paysage. A partir de retours d’expériences, ont été présentées des méthodes pertinentes (déjà testées) caractérisant des paysages et des unités fonctionnelles cohérentes par télédétection, puis des indicateurs spatiaux sur l’état des ressources, l’impact des pratiques agricoles et forestières, des politiques publiques, le degré de dégradation, des relations santé/environnement, la connectivité de la trame verte....A la suite de ces exposés, des ateliers ont été organisés afin d’établir ensemble les champs scientifiques et les « produits » (méthodes, outils, cartes thématiques, guides méthodologiques) qui engageront les futurs échanges autour du paysage et des images de satellite. Ces journées ont marqué le lancement du CES Paysage. Ces journées sont conçues pour être un moment d’échanges entre experts, représentants de l’ART GeoDEV et d’observateurs extérieurs afin de poser les fondements scientifiques sur lesquels reposera ce CES international du pôle Theia. A terme, l’ambition est de faire émerger un réseau d’acteur publics, privés et de scientifiques (nationaux et internationaux), autour de l’usage des données et produits à valeur ajoutée issus de la télédétection.

This bachelor thesis will focus on determining tree characteristics, which are diameter at breast height (DBH) and tree height using two different methods. The first method is conducted by ground measurement of the instruments currently used. The second method is done by using a combination of ground and aerial photogrammetry using an unmanned aerial vehicle (UAV). Thanks to the subsequent software analysis, DBH and tree position were determined by terrain's photogrammetry, and the aerial photogrammetry generated the height of the individual trees. After colleting all results, these methods were compared for accuracy, time consumption and any potential future use in forestry.

The recent development of REDD+ mechanisms requires reliable estimation of carbon stocks, especially in tropical forests that are particularly threatened by global changes. Even though tree height is a crucial variable for computing aboveground forest biomass (AGB), it is rarely measured in large-scale forest censuses because it requires extra effort. Therefore, tree height has to be predicted with height models. The height and diameter of all trees over 10 cm in diameter were measured in 33 half-hectare plots and 9 one-hectare plots throughout northern French Guiana, an area with substantial climate and environmental gradients. We compared four different model shapes and found that the Michaelis–Menten shape was most appropriate for the tree biomass prediction. Model parameter values were significantly different from one forest plot to another, and this leads to large errors in biomass estimates. Variables from the forest stand structure explained a sufficient part of plot-to-plot variations of the height model parameters to improve the quality of the AGB predictions. In the forest stands dominated by small trees, the trees were found to have rapid height growth for small diameters. In forest stands dominated by larger trees, the trees were found to have the greatest heights for large diameters. The aboveground biomass estimation uncertainty of the forest plots was reduced by the use of the forest structure-based height model. It demonstrated the feasibility and the importance of height modeling in tropical forests for carbon mapping. When the tree heights are not measured in an inventory, they can be predicted with a height–diameter model and incorporating forest structure descriptors may improve the predictions.

Aim of study : To assess terrestrial laser scanning (TLS) accuracy in estimating biometrical forest parameters at plot-based level in order to replace manual survey for forest inventory purposes. Area of study : Monte Morello, Tuscany region, Italy Material and methods : In 14 plots (10 m radius) in dense Mediterranean mixed conifer forests, diameter at breast height (DBH) and height were measured in Summer 2016. Tree volume was computed using the second Italian National Forest Inventory (INFC II) equations. TLS data were acquired in the same plots and quantitative structure models (QSMs) were applied to TLS data to compute dendrometric parameters. Tree parameters measured in field survey, i.e . DBH, height, and computed volume, were compared to those resulting from TLS data processing. The effect of distance from the plot boundary in the accuracy of DBH, height and volume estimation from TLS data was tested. Main results : TLS-derived DBH showed a good correlation with the traditional forest inventory data ( R 2 =0.98, RRMSE=7.81%), while tree height was less correlated with the traditional forest inventory data ( R 2 =0.60, RRMSE=16.99%). Poor agreement was observed when comparing the volume from TLS data with volume estimated from the INFC II prediction equations. Research highlights : The study demonstrated that the application of QSM to plot-based terrestrial laser data generates errors in plots with high density of coniferous trees. A buffer zone of 5 m would help reduce the error of 35% and 42% respectively in height estimation for all trees and in volume estimation for broadleaved trees.

International audience; The measurement of biomass can be obtained from remote sensing analysis and modelling, the impacts of which are related to oil palm cultivation in industrial plantations. Our study aims at producing a spatial model for oil palm biomass estimation, at different scales of spatial analysis. The study was carried out in the industrial plantations of the Cameroonian Society of Palm Groves (SOCAPALM). The developed methodology combined: (i) the mapping of palm groves (Kumar, 2015), (ii) the characterisation of palm groves (Gadal, 2013), (iii) biomass estimation, and (iv) the comparison of the obtained results with Spot 6, Landsat 7 ETM+ and Landsat 8 OLI images from 2001 to 2015. The first results were obtained for the mapping of the SOCAPALM industrial palm groves between 2001 and 2015. The obtained maps were highly correlated (Kappa of 0.91 for Spot 6, 0.92 for Landsat 7 and 0.82 for Lansat8), however, because of the presence of mixed pixels, some confusion between oil palm and other classes were observed. One of the factors affecting biomass estimation is spatial accuracy. Several improvements have been suggested : (1) mapping palm groves at a subpixel scale using super-resolution mapping; (2) developing a classification system of cartographic products. The use of satellites images with different spatial resolutions may also help to generate new data taking into account the level of spatial analysis.

GlobAllomeTree is an international platform for tree allometric equations. It is the first worldwide web platform designed to facilitate the access of the tree allometric equation and to facilitate the assessment of the tree biometric characteristics for commercial volume, bio-energy or carbon cycling. The webplatform presents a database containing tree allometric equations, a software called Fantallomatrik, to facilitate the comparison and selection of the equations, and documentation to facilitate the development of new tree allometric models, improve the evaluation of tree and forest resources and improve knowledge on tree allometric equations. In the Fantallometrik software, equations can be selected by country, ecological zones, input parameters, tree species, statistic parameters and outputs. The continuously updated database currently contains over 5000 tree allometric equations classified according to 73 fields. The software Fantallometrik can be also used to compare equations, insert new data and estimate the selected output variables using field inventory. The GlobAllomeTree products are freely available at the URL: http://globallometree.org for a range of users including foresters, project developers, scientist, student and government staff.

The populations of light-demanding trees that dominate the canopy of central African forests are now aging. Here, we show that the lack of regeneration of these populations began ca. 165 ya (around 1850) after major anthropogenic disturbances ceased. Since 1885, less itinerancy and disturbance in the forest has occurred because the colonial administrations concentrated people and villages along the primary communication axes. Local populations formerly gardened the forest by creating scattered openings, which were sufficiently large for the establishment of light-demanding trees. Currently, common logging operations do not create suitable openings for the regeneration of these species, whereas deforestation degrades landscapes. Using an interdisciplinary approach, which included paleoecological, archaeological, historical, and dendrological data, we highlight the long-term history of human activities across central African forests and assess the contribution of these activities to present-day forest structure and composition. The conclusions of this sobering analysis present challenges to current silvicultural practices and to those of the future. DOI: http://dx.doi.org/10.7554/eLife.20343.001, eLife digest The world’s forests contain trillions of trees. Some of those trees require more light than others to mature, and certain species can only grow to reach the forest canopy if they have access to sunlight throughout their whole life. Central Africa is home to the second largest tropical rainforest in the world. Previous studies showed that few young trees of light-demanding species were growing to replace the old trees in this forest. As a result this population is aging and at risk of disappearing, which is a major concern. Many light-demanding tree species in the Central African forest are cut down for their valuable timber. However, if young trees do not grow to replace the mature ones that are logged, even logging operations that follow national and international environmental rules cannot guarantee the sustainability of these trees. As such, Morin-Rivat et al. set out to understand what changed in the Central African forest in the past to stop the regeneration of the light-demanding trees. The analyses focused on four species classified as light-demanding trees in part of Central Africa called the northern Congo Basin. Most of the trees in these species were about 165 years old. This was the case even though the different species grow at different rates, and it means that they all grew from young trees that settled in the middle of the 19th century. So what was it that changed after this period to stop this population of light-demanding trees in the Central African forest from regenerating? By combining information from a number of datasets and historical records, Morin-Rivat et al. arrived at the following conclusion. Before the mid-19th century, many people lived in the forest and their activities created clearings that turned the forest into a relatively patchy landscape. However from about 1850 onwards, when Europeans started to colonize the region, people and villages were moved out of the forests and closer to rivers and roads for administrative and commercial purposes. Moreover, many people were killed in conflicts or died because of newly introduced diseases, which also led to fewer people in the forest. As a result, the forest became less disturbed. With fewer clearings, fewer light-demanding trees would have had enough access to sunlight to grow to maturity. The findings of Morin-Rivat et al. show that disturbance is needed to maintain certain forest habitats and tree species, including light-demanding species of tree. As common logging operations do not create openings large enough to guarantee that such species will be able to establish themselves naturally, complementary treatments are needed. These might include selectively logging mature trees around young members of light-demanding species, or planting threatened species. DOI: http://dx.doi.org/10.7554/eLife.20343.002

National audience

Comment analyser la réponse de la biodiversité à la mise en réserve intégrale ? La première étape est d'explorer les données de structure forestière et de description spatiotemporelle pour identifier les caractéristiques déterminantes, les « variables explicatives » de modèles destinés à expliquer les variations de biodiversité entre forêts exploitées et réserves. Originalité du projet GNB : la démarche se réfère à la notion de naturalité(s), en distinguant variables de naturalité anthropique et variables de naturalité biologique.

Anthropogenic effects on rodent richness, diversity, abundance, and relative density were studied in 4 habitats of the Masako Reserve, situated in the northeastern part of the Democratic Republic of the Congo. A primary forest dominated by Gilbertiodendron dewevrei as well as 3 anthropogenic habitats (secondary forest, fallow land, and the edge zone situated between the fallow land and the secondary forest) were sampled for rodents between May 2009 and April 2010. 1275 specimens (24 species and 5 families) were captured to quantify the differences in composition and abundance between the non disturbed habitat and the anthropogenic habitats, and between the edge zone and its adjacent habitats. Results indicated a non uniform rodent distribution across the four habitats. Richness and diversity were high in the edge habitat and low in the primary forest. Every habitat was characterized by a different relative density, of which the highest values were observed for the secondary forest and for the fallow habitat; the lowest value was observed for the primary forest. Edge zone characteristics differed from the adjacent habitats which suggested the existence of edge effects. Abundances differed significantly between habitats except between the secondary forest and the fallow land. The low evenness values observed in all habitats reflected the relative instability of the ecosystems at study. A chi-squared test confirmed the existence of seasonal effects on rodent abundance; the impact of anthropogenic activities on rodent presence was shown in the same way for the anthropogenic habitats but not for the primary forest habitat. © Léon Iyongo Waya Mongo, Marjolein Visser, Charles De Cannière, Erik Verheyen, Benjamin Dudu Akaibe, Joseph Ulyel Ali-Patho and Jan Bogaert., SCOPUS: ar.j, info:eu-repo/semantics/published

Many tropical tree species have buttresses at the standard breast height (1.3 m above ground) of diameter measurement, with a presumable role in improving nutrient acquisition or tree anchorage in the ground (Newbery et al. 2009, Richter 1984). Measuring the diameter using standard dendrometrical tools such as callipers or graduated tapes, which require that the cross-section of the trunk has a convex shape, is then impossible (Nogueira et al. 2006). The recommended method in this case is to measure the diameter above the buttress (DAB), thus possibly leading to biased estimates of the basal area (West 2009), of tree above-ground biomass (Dean & Roxburgh 2006, Dean et al. 2003) and of tree growth (Metcalf et al. 2009). As an alternative, one can measure the basal area at breast height of buttressed trees, using a method that can deal with the irregular non-convex shape of the cross-section of the stem such as the Picus calliper, photogrammetry or 3D laser scanning (Badia et al. 2003, Dean 2003, Newbery et al. 2009).

Ce travail est axé sur une étude morphométrique de Leucaena leucocephala dans la région d’Adrar.Il se trouve dans un étage bioclimatique de type saharien à hiver frais.La diversité floristique montre la dominance des chamaephytes et des phanérophytes au profil des thérophytes. La texture du sol est de type sablonneux, basique à faible degré de salinité, de conductivité basse et de pH élevé.L’étude morphométrique montre de très bonne corrélation entre les différents paramètres mesurés. L'étude dendrométrique a révélé une nette dominance des sujets jeunes à faible diamètre dans les sites d'étude. Mots clés: Leucaena leucocephala, morphométrie, Dendrométrie, sol, Adrar. الملخص في ولاية أدرار . ذات مناخ صحراوي و leucaena leucocephala تنصب هذه الدراسة حول دراسة مرفولوجية لنبات قوام التربة . thérophytes على حساب phanérophytes و chamaephytes شتاء بارد. التنوع النباتي بين هيمنة هو ذات نوع رملي و ملوحة منخفضة ودرجة حموضة عالية. الدراسة المورفومترية سجلت علاقة جيدة بين مختلف الثوابت المقاسة. أظهرت دراسة القياس الشجري أن غالبية الأفراد المكونة هي أفراد فتية تتميز جذوعها بقطر ضعيف. مورفومترية - القياس الشجري - تربة – أدرار - Leucaena leucocephala ׃ الكلمات المفتاحیة Abstract: This work is centred on a morphométrique study of Leucaena leucocephala in the region of Adrar. It is located in a bioclimatic Saharan type cool winter. Floristic diversity shows the predominance of the chamaephytes and the phanérophytes to the profile of the thérophytes. Soil texture is sandy type basic low salinity, low conductivity and high pH. The morphometric study shows very good correlation between the measured Parameters. The dendrometric study revealed a clear predominance of the young subjects with low diameter in the sites of study. Key words: Leucaena leucocephala, Morphometry, dendrometry , Sol, Adrar.

National audience

Le but de ce travail c’était de caractériser l’état actuel du peuplement de chène zéen et d’appréhender de la succession du chêne liège par le chêne zéen par contre concernant le chêne liège qui présente un dépérissement et une régression significative. Les comparaisons dendrométriques entre les stations d’études montre une bonne productivité de bois au niveau de la station n° 2 , par contre la densité est relativement élevée dans la station n° 3. Aux niveaux du cortège floristiques on note que l’espèce Vuburnum Tumus et Hedera canariensis est toujours présente dans les trois stations. La stratégie de préservation efficace de ces peuplements repose sur une politique encourageante basé sur la mise en place d’une série d’action soit arrêtera la régression de chêne liège, soit laisser le développement du chêne zéen. Mots clés : Peuplement – dendrométrie – matière organique – The aim of this study was to characterize the current state of zeen oak stand and grasp of the estate of cork oak by oak zeen by cons on cork oak decline and that presents a significant regression. Comparisons between stations dendrometric study shows good productivity of timber at station N. 2, against the density is relatively high in station N. 3. In terms of floristic we note that the species vebernum Tumus is always present in the three stations for the same case. The efficient conservation strategy of these stands is based on a policy based on encouraging the establishment of a series of action is to stop the exploitation of cork oak, or leave the development of zéen oak. Keywords: Stand – dendrometric - organic matter الھدف من ھتھ الدراسة ھي وصف الحالة الراھنة لأشجار بلوط الزان و الوقوف على مدى وجود شجرة الفین بصفة دائمة مع شجرة بلوط الزان مع أن شجرة الفلین توجد في حالة تراجع كبیر و نقصان شدیدین. المقارنة الدندرومتریة بین المواقع بینت إنتاجیة خشب جیدة بالمقارنة مع مواقع المعاینة الأخرى أما موقع المعاینة 3 فیتمیز بنسبة عالیة من أشجار بلوط الزان. بالنسبة للغطاء النیاتي الموجود نلاحظ ان نبتة دائمة الوجود في كل مواقع المعاینة مع طریقة المحافظة الجیدة على ھتھ الأشجار تتركز في سیاسة مشجعة إما الحد من تفاقم ظاھرة قطع أشجار الفلین و اما ترك شجرة بلوط الزان تاخد اتزانھا . الكلمات المفتاحیة بلوط الزان- بلوط الفلین – الدندرومتریة – الغطاء النباتي – القطع المفرط للأشجار

Pistacia atiantica est une espèce qui a une large répartition géographique. On la retrouve au nord comme au sud. Dans cette investigation nous avons ciblé une étude dendrométrique des pieds qui constituent le peuplement de Sidi Makhlouf (commune d'Ouled Brahim) d'une part et analysé le sol sur lequel se développent ces pieds de l'autre part. Les résultats obtenus dans cette investigation montrent l'état actuel des peuplements de la pistacheraie ; nous avons noté la présence de pieds très intéressants avec des diamètres pouvant atteindre 3 m. Sur le plan pédologique l'ensemble des sols analysés sont de texture limoneuse. Mots clés : Pistacia atiantica, dendrométrie, pédologie, Sidi Makhlouf, Ouled Brahim. JLil ,i )ji+ y Jsaz 5it UjSj J1tI I.A r»U4 "Jj "-j L»& '-L 'u eL411 4jaJ eAue Summary: Pistacia allantica is a species that has a wide geographical distribution. it is found both north and south. In this investigation we focused on a study dendrometric feet that constitue the population of Sidi Makhlouf (common Ouled Brahim) on the one hand and analyzed the soil in which grow the feet of the other. The resuits obtained in this investigation show the current state of the stands pistacheraie; we noted the presence of very intersting feet with diameters of up to 3 m. On the soil map of ail analyzed sous are loamy. Keywords : Pistaci atiantica, mensuration, pedology, Sidi Maklilouf, Ouled Brahim

The importance of measuring forest biophysical properties for ecosystem health monitoring and forest management encourages researchers to find precise, yet low-cost methods especially in mountainous and large areas. In the present study, geoscience laser altimeter system (GLAS) on board Ice, Cloud, and land Elevation Satellite (ICESat) was used to estimate three biophysical characteristics of forests located in the north of Iran: 1) maximum canopy height ( ${\text {H}_{{\max}}}$ ); 2) Lorey’s height ( ${{\text H}_{\text{Lorey}}}$ ); and 3) forest volume (V). A large number of multiple linear regressions (MLR) and also random forest (RF) regressions were developed using different sets of variables including waveform metrics, principal components (PCs) produced from principal component analysis (PCA) and wavelet coefficients (WCs) generated from wavelet transformation (WT). To validate and compare models, statistical criteria were calculated based on a fivefold cross validation. Best model concerning the maximum height was an MLR ( ${\text {RMSE}} = {5.0}\;{\text m}$ ) which combined two metrics extracted from waveforms (waveform extent “ ${{\text W}_{\text{ext}}}$ ” and height at 50% of waveform energy “ ${{\text H}_{{50}}}$ ”), and one from digital elevation model (terrain index, TI). The mean absolute percentage error (MAPE) of maximum height estimates was 16.4%. For Lorey’s height, a simple MLR (including ${{\text W}_{\text{ext}}}$ and TI) represented the highest performance ( ${\text {RMSE}} = {5.1}\;{\text m}$ , ${\text {MAPE}} = {24.0}\% $ ). Generally, MLR models had a better performance when compared to the RF models. In addition, the accuracy of height estimations using waveform metrics was greater than those based on PCs or WCs. Concerning forest volume, regression models estimating volume directly from GLAS data led to a better result ( ${\text {RMSE}} = {128.8}\;{{\text m}^{3}}/\text {ha}$ ) rather than volume– ${{\text H}_{\text{Lorey}}}$ relationship ( ${\text {RMSE}} = {167.8}\;{{\text m}^{3}}/\text {ha}$ ).

Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions. We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions. We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate “wall-to-wall” remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (