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Forest is Life (University of Liège)

Goal: The CARE Forest is life aims to study forest ecosystems and, more generally, landscape structures with a low degree of anthropisation, whether in temperate or tropical regions.

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Nicolas Latte
added a research item
La surface de la pessière wallonne a diminué de 30 % entre 1980 et 2010. L’exploitation d’un grand nombre de peuplements arrivés à maturité ces deux dernières décennies et un faible taux de replantation expliquent cette tendance. La crise des scolytes que nous avons connue ces dernières années, si elle a accentué la pression sur la ressource en épicéa, n'a pas modifié significativement la tendance. L’objet de cet article est de présenter une image aussi fidèle et actualisée que possible de la ressource en épicéa au niveau de la Wallonie (surfaces, volumes récoltés, volumes sur pied, classes de circonférence, types de propriétaire, niveau d’aptitude stationnelle). Les résultats présentés proviennent du croisement de plusieurs travaux de recherches développés par l’équipe de Gembloux Agro-Bio Tech (ULiège).
Alexandre Delplanque
added a research item
Survey and monitoring of wildlife populations are among the key elements in nature conservation. The use of unmanned aerial vehicles and light aircrafts as aerial image acquisition systems is growing, as they are cheaper alternatives to traditional census methods. However, the manual localization and identification of species within imagery can be time-consuming and complex. Object detection algorithms, based on convolutional neural networks (CNNs), have shown a good capacity for animal detection. Nevertheless, most of the work has focused on binary detection cases (animal vs. background). The main objective of this study is to compare three recent detection algorithms to detect and identify African mammal species based on high-resolution aerial images. We evaluated the performance of three multi-class CNN algorithms: Faster-RCNN, Libra-RCNN and RetinaNet. Six species were targeted: topis (Damaliscus luna-tus jimela), buffalos (Syncerus caffer), elephants (Loxodonta africana), kobs (Kobus kob), warthogs (Phacochoerus africanus) and waterbucks (Kobus ellip-siprymnus). The best model was then applied to a case study using an independent dataset. The best model was the Libra-RCNN, with the best mean average precision (0.80 AE 0.02), the lowest degree of interspecies confusion (3.5 AE 1.4%) and the lowest false positive per true positive ratio (1.7 AE 0.2) on the test set. This model was able to detect and correctly identify 73% of all individuals (1115), find 43 individuals of species other than those targeted and detect 84 missed individuals on our independent UAV dataset, with an average processing speed of 12 s/image. This model showed better detection performance than previous studies dealing with similar habitats. It was able to differentiate six animal species in nadir aerial images. Although limitations were observed with warthog identification and individual detection in herds, this model can save time and can perform precise surveys in open savanna.
Bastien Vandendaele
added a research item
UAV laser scanning (ULS) has the potential to support forest operations since it provides high-density data with flexible operational conditions. This study examined the use of ULS systems to estimate several tree attributes from an uneven-aged northern hardwood stand. We investigated: (1) the transferability of raster-based and bottom-up point cloud-based individual tree detection (ITD) algorithms to ULS data; and (2) automated approaches to the retrieval of tree-level (i.e., height, crown diameter (CD), DBH) and stand-level (i.e., tree count, basal area (BA), DBH-distribution) forest inventory attributes. These objectives were studied under leaf-on and leaf-off canopy conditions. Results achieved from ULS data were cross-compared with ALS and TLS to better understand the potential and challenges faced by different laser scanning systems and methodological approaches in hardwood forest environments. The best results that characterized individual trees from ULS data were achieved under leaf-off conditions using a point cloud-based bottom-up ITD. The latter outperformed the raster-based ITD, improving the accuracy of tree detection (from 50% to 71%), crown delineation (from R 2 = 0.29 to R 2 = 0.61), and prediction of tree DBH (from R 2 = 0.36 to R 2 = 0.67), when compared with values that were estimated from reference TLS data. Major improvements were observed for the detection of trees in the lower canopy layer (from 9% with raster-based ITD to 51% with point cloud-based ITD) and in the intermediate canopy layer (from 24% with raster-based ITD to 59% with point cloud-based ITD). Under leaf-on conditions, LiDAR data from aerial systems include substantial signal occlusion incurred by the upper canopy. Under these conditions, the raster-based ITD was unable to detect low-level canopy trees (from 5% to 15% of trees detected from lower and intermediate canopy layers, respectively), resulting in a tree detection rate of about 40% for both ULS and ALS data. The cylinder-fitting method used to estimate tree DBH under leaf-off conditions did not meet inventory standards when compared to TLS DBH, resulting in RMSE = 7.4 cm, Bias = 3.1 cm, and R 2 = 0.75. Yet, it yielded more accurate estimates of the BA (+3.5%) and DBH-distribution of the stand than did allometric models −12.9%), when compared with in situ field measurements. Results suggest that the use of bottom-up ITD on high-density ULS data from leaf-off hardwood forest leads to promising results when estimating trees and stand attributes, which opens up new possibilities for supporting forest inventories and operations.
Cédric Vermeulen
added a research item
L’intensification des activités humaines, la demande croissante en protéines animales suite à l’explosion démographique et le braconnage organisé (ivoire, écailles de pangolins,...) entrainent une pression croissante sur la faune sauvage des forêts d’Afrique centrale. Pour répondre à ces menaces, des stratégies sont mises en place aux échelles nationales et régionales. Une gestion efficace de la faune sauvage au sein des concessions certifiées concourt à l’objectif global d’une gestion raisonnée et durable du patrimoine forestier d’Afrique centrale. Le présent guide constitue un outil opérationnel à destination des exploitants forestiers d’Afrique centrale. Il présente de manière pragmatique et illustrée la démarche d’élaboration et de mise en oeuvre d’un plan de gestion de la faune, en partant des cadres législatifs et règlementaires à respecter jusqu’à l’évaluation de sa performance. Les principales mesures de gestion et de conservation de la faune à mettre en place sont décrites dans des fiches thématiques. Un canevas modèle de plan de gestion de la faune proposant une hiérarchisation dans la mise en oeuvre de ces différentes mesures est présenté. Cet ouvrage vise à améliorer les pratiques des exploitants forestiers en termes de gestion de la faune et à les accompagner dans une démarche de certification de légalité ou de durabilité.
Nicolas Latte
added a research item
Riparian ecosystems are home to a remarkable biodiversity, but have been degraded in many regions of the world. Vegetation biomass is central to several key functions of riparian systems. It is influenced by multiple factors, such as soil waterlogging, sediment input, flood, and human disturbance. However, knowledge is lacking on how these factors interact to shape spatial distribution of biomass in riparian forests. In this study, LiDAR data were used in an individual tree approach to map the aboveground biomass in riparian forests along 200 km of rivers in the Meuse catchment, in southern Belgium (Western Europe). Two approaches were tested, relying either on a LiDAR Canopy Height Model alone or in conjunction with a LiDAR point cloud. Cross-validated biomass relative mean square errors for 0.3 ha plots were, respectively, 27% and 22% for the two approaches. Spatial distribution of biomass patterns were driven by parcel history (and particularly vegetation age), followed by land use and topographical or geomorphological variables. Overall, anthropogenic factors were dominant over natural factors. However, vegetation patches located in the lower parts of the riparian zone exhibited a lower biomass than those in higher locations at the same age, presumably due to a combination of a more intense disturbance regime and more limiting growing conditions in the lower parts of the riparian zone. Similar approaches to ours could be deployed in other regions in order to better understand how biomass distribution patterns vary according to the climatic, geological or cultural contexts.
Davy Fonteyn
added 2 research items
Cette étude évalue l’abondance des graines d’Erythrophleum suaveolens dans la banque de semences du sol des forêts denses humides d’Afrique centrale. Les travaux ont été menés au Nord-Congo dans deux types forestiers : la forêt à Celtis sur des sols argilo-sableux à sablo-argileux et la forêt à Manilkara sur des sols sableux. Les tiges d’E. suaveolens (dhp ≥ 10 cm) ont été inventoriées dans deux blocs de 400 ha, et les structures diamétriques de leurs populations ont été comparées. En outre, 80 fosses (2 x 40 fosses par type de forêt) ont été creusées au pied de 20 arbres (10 par forêt), sur trois couches contiguës de 10 cm chacune, soit à une profondeur totale de 30 cm, et l’abondance des graines dans la banque de semences du sol a été évaluée. La dormance des graines récoltées a été testée par des essais de germination après traitement au H2SO4 et cinq graines prélevées jusqu'à une profondeur de 20 cm dans la forêt à Celtis ont été utilisées pour estimer leur âge par spectroscopie de masse par accélérateur (AMS). Dans les deux types forestiers, les structures diamétriques présentent une distribution gaussienne, illustrant un déficit de régénération. Alors que les densités de tiges (dhp ≥ 10 cm) sont proches, avec 0,85 et 1,05 tige/ha respectivement, dans la forêt à Celtis et la forêt à Manilkara. Les densités de graines sont significativement plus élevées dans la forêt à Celtis (8,55 graines/m2) que dans la forêt à Manilkara (0,15 graine/m2). Le pourcentage maximum de germination obtenu était de 19,1 % pour des graines n’ayant subi aucun traitement. Les lots traités à l’acide ont présenté de moindres taux de germination. Ces graines semblent pouvoir se conserver une dizaine d’années au moins dans la banque du sol. Les facteurs pouvant influencer les variations de densité des graines sont discutés et des recommandations sylvicoles sont formulées.
We present new Gabonese locality records, ecological and morphological data or unpublished material for Kinixys erosa (Testudinidae), Trachylepis albilabris (Scincidae), Calabaria reinhardtii (Boidae), Dasypeltis fasciata, Hapsidophrys smaragdinus, Philothamnus carinatus, P. heterodermus and P. nitidus nitidus, Thrasops flavigularis, Toxicodryas blandingii and T. pulverulenta (Colubridae), Dendroaspis jamesoni jamesoni, Naja melanoleuca (Elapidae), Mehelya poensis, Polemon collaris (Lamprophiidae), Natriciteres fuliginoides (Natricidae), Python sebae (Pythonidae), Bitis gabonica and Causus maculatus (Viperidae). One snake species is newly recorded from Loango National Park, and three from Estuaire Province.
Gauthier Ligot
added 42 research items
The mid-successional sessile oak (Quercus petraea (Matt.) Liebl.) and the late-successional European beech (Fagus sylvatica L.) are two major species of temperate forests. According to the literature, in mixed stands, large canopy openings should promote the growth of the light-demanding oak over the shade tolerant beech. Nevertheless, foresters who manage mixed oak and beech forests with continuous-cover silviculture in Western and Central Europe, face difficulties to promote the regeneration of oak. In the Belgian Ardennes, we monitored the mixed advanced regeneration of 7–13 year old oak and beech trees scattered across 23 sites to test the hypotheses regarding the relative advantage of the two species across the light gradient, the outcome of interspecific competition exerted by neighbouring saplings, the effect of direct and diffuse radiation and the site effect. We adjusted a set of mixed non-linear models of the height growth of saplings for the two species and selected the best model for the two species. In contrast to expectations, we found that beech saplings had the highest height growth rate at all light levels. Beech saplings reached an optimum growth at transmittance of 10%, whereas oak saplings needed more than 20%. The two species responded positively to soil richness but only oak saplings responded to direct radiation and micro-climatic variations. These results indicate that oak saplings are systematically outcompeted by beech saplings across the light gradient. Thus, the control of canopy opening is not sufficient to promote the natural regeneration of oak beneath a stand also containing beech in the Belgian Ardennes.
Radiation is fundamental in forest ecosystem ecology as it drives plant photosynthesis, morphogenesis, and fluxes of carbon, water, and energy between soil, vegetation, and the atmosphere. Though all approaches of forest radiative transfer models (FRTM) share general properties, they differ greatly in terms of calibration parameters, required assumptions, and model objectives. They use different precision levels of canopy description (from one to three dimensions) and different mathematical relationships to model the attenuation of radiation through the canopy. To date, no general guideline has been given to help the modeler choose the approach that best suits his needs. We therefore reviewed evaluation, sensitivity, and performance of FRTMs recently reported in the literature. We quantified FRTM uncertainty and identified the most sensitive parameters relative to the modeling choices. Their advantages and drawbacks are discussed, and recommendations are made relative to application potential.
Nicolas Latte
added 10 research items
L’essentiel de la ressource en bouleau (verruqueux et pubescent) se situe en Russie et en Scandinavie (15 mil- liards de m 3 ) et cette ressource augmente graduellement depuis plusieurs années. Il y est fortement valorisé en sciage, déroulage et trituration. En Europe de l’Ouest, cette croissance s’observe aussi, même si seulement 1 % de la ressource s’y concentre (dû notamment à la plus grande diversité d’essences commerciales présentes). En Wallonie, les évolutions du contexte socio-économique et environnemental jouent en faveur d’une augmentation de la présence du bouleau (parcelles non reboisées, entretien insuffisant, mélanges spontanés...). Le bouleau représente souvent une belle opportunité pour les mélanges, une excellente essence d’accompagnement et une diversification de la production. Mais sans une sylviculture adaptée, les grumes sont généralement de faible dimension et présentent de nombreux défauts. C’est le cas de l’essentiel de la ressource actuelle en Wallonie. Aujourd’hui, les besoins sont de mieux le connaître, notamment les opportuni- tés de valorisation, et d’aboutir à des recommandations sylvicoles. Il ne s’agit donc pas de vouloir faire du bouleau à tout prix mais plutôt de tirer profit d’une étape transitoire de la succession forestière.
Sentinel-2 (S2) imagery is used in many research areas and for diverse applications. Its spectral resolution and quality are high but its spatial resolutions, of at most 10 m, is not sufficient for fine scale analysis. A novel method was thus proposed to super-resolve S2 imagery to 2.5 m. For a given S2 tile, the 10 S2 bands (four at 10 m and six at 20 m) were fused with additional images acquired at higher spatial resolution by the PlanetScope (PS) constellation. The radiometric inconsistencies between PS microsatellites were normalized. Radiometric normalization and super-resolution were achieved simultaneously using state-of-the-art super-resolution residual convolutional neural networks adapted to the particularities of S2 and PS imageries (including masks of clouds and shadows). The method is described in detail, from image selection and downloading to neural network architecture, training, and prediction. The quality was thoroughly assessed visually (photointerpretation) and quantitatively, confirming that the proposed method is highly spatially and spectrally accurate. The method is also robust and can be applied to S2 images acquired worldwide at any date.
Forest monitoring tools are needed to promote effective and data driven forest management and forest policies. Remote sensing techniques can increase the speed and the cost-efficiency of the forest monitoring as well as large scale mapping of forest attribute (wall-to-wall approach). Digital Aerial Photogrammetry (DAP) is a common cost-effective alternative to airborne laser scanning (ALS) which can be based on aerial photos routinely acquired for general base maps. DAP based on such pre-existing dataset can be a cost effective source of large scale 3D data. In the context of forest characterization, when a quality Digital Terrain Model (DTM) is available, DAP can produce photogrammetric Canopy Height Model (pCHM) which describes the tree canopy height. While this potential seems pretty obvious, few studies have investigated the quality of regional pCHM based on aerial stereo images acquired by standard official aerial surveys. Our study proposes to evaluate the quality of pCHM individual tree height estimates based on raw images acquired following such protocol using a reference filed-measured tree height database. To further ensure the replicability of the approach, the pCHM tree height estimates benchmarking only relied on public forest inventory (FI) information and the photogrammetric protocol was based on low-cost and widely used photogrammetric software. Moreover, our study investigates the relationship between the pCHM tree height estimates based on the neighboring forest parameter provided by the FI program. Our results highlight the good agreement of tree height estimates provided by pCHM using DAP with both field measured and ALS tree height data. In terms of tree height modeling, our pCHM approach reached similar results than the same modeling strategy applied to ALS tree height estimates. Our study also identified some of the drivers of the pCHM tree height estimate error and found forest parameters like tree size (diameter at breast height) and tree type (evergreenness/deciduousness) as well as the terrain topography (slope) to be of higher importance than image survey parameters like the variation of the overlap or the sunlight condition in our dataset. In combination with the pCHM tree height estimate, the terrain slope, the Diameter at Breast Height (DBH) and the evergreenness factor were used to fit a multivariate model predicting the field measured tree height. This model presented better performance than the model linking the pCHM estimates to the field tree height estimates in terms of r² (0.90 VS 0.87) and root mean square error (RMSE, 1.78 VS 2.01 m). Such aspects are poorly addressed in literature and further research should focus on how pCHM approaches could integrate them to improve forest characterization using DAP and pCHM. Our promising results can be used to encourage the use of regional aerial orthophoto surveys archive to produce large scale quality tree height data at very low additional costs, notably in the context of updating national forest inventory programs.
Corentin Bolyn
added 4 research items
La connaissance de la ressource forestière à l’échelle d’une région ou d’un pays est un préalable à la mise en place d’une politique forestière réfléchie. Complémentaire aux inventaires par échantillonnage, la télédétection constitue une source alternative d’information pour la description des ressources forestières aux échelles régionales, nationales et transnationales. Avec le lancement récent des satellites Sentinel-1 et Sentinel-2 (Copernicus) en 2014-2016, l’offre en image satellitaire a connu une petite révolution. Ces nouvelles données ont agrandi le champ des possibles en termes de cartographie des forêts et de leur composition spécifique. Dans ce contexte, une méthode a été développée pour cartographier les principaux types de peuplement de Belgique et du Nord de la France. Bien que la précision atteinte à ce jour reste trop faible pour en faire un outil de gestion local suffisamment fiable, les résultats ont démontré le très grand potentiel des images Sentinel pour réaliser la cartographie des essences forestière sur une échelle transfrontalière. Cette approche en développement laisse entrevoir des améliorations conséquentes à moyen termes pour soutenir les acteurs de la gestion forestière.
Il est aujourd’hui admis qu’une part importante de la ressource ligneuse se trouve en dehors de la forêt. Les « arbres hors forêt » ont un rôle important dans notre environnement grâce à leurs multiples fonctions : production de bois, préservation de la biodiversité, qualité paysagère… Bien que l’évolution récente des politiques environnementales tendent à leur donner plus d’importance, ils restent peu étudiés et ne font que rarement l’objet d’un inventaire ou d’un suivi à l’échelle régionale ou nationale. Face au besoin d’outils pour l’évaluation de cette ressource, une méthode de cartographie et de description des éléments arborés situés hors forêt a été développée. Elle repose sur l’utilisation de données LiDAR aérien au travers d’une série d’algorithmes intégrée dans une procédure automatique. Les éléments arborés de plus de 2 mètres de hauteur sont cartographiés avec une résolution de 1 mètre et catégorisés en cinq classes en fonction de leurs dimensions et de leur organisation spatiale. Les utilisations de cette couche cartographique sont nombreuses : calcul de statistiques, analyses spatiales, étude de la dynamique temporelle… À titre d’exemple, nous présentons les résultats obtenus sur trois sites : les communes rurales de Ohey et de Paliseul en Wallonie, et un périmètre regroupant douze communes françaises situées au Nord-Est de Valencienne.
Trees have important and diverse roles that make them essential outside of the forest. The use of remote sensing can substantially support traditional field inventories to evaluate and characterize this resource. Existing studies have already realized the automated detection of trees outside the forest (TOF) and classified the subsequently mapped TOF into three geometrical classes: single objects, linear objects, and ample objects. This study goes further by presenting a fully automated classification method that can support the operational management of TOF as it separates TOF into seven classes matching the definitions used in field inventories: Isolated tree, Aligned trees, Agglomerated trees, Hedge, Grove, Shrub, and Other. Using publicly available software tools, an orthophoto, and a LIDAR canopy height model (CHM), a TOF map was produced and a two-step method was developed for the classification of TOF: (1) the geometrical classification of each TOF polygon; and (2) the spatial neighboring analysis of elements and their classification into seven classes. The overall classification accuracy was 78%. Our results highlight that an automated TOF classification is possible with classes matching the definitions used in field inventories. This suggests that remote sensing has a huge potential to support the operational management of TOF as well as other research areas regarding TOF.
Chloé Dupuis
added a research item
In the context of the climate and biodiversity crisis facing our planet, tropical forests playing a key role in global carbon flux and containing over half of Earth's species are important to preserve. They are today threatened by deforestation but also by forest degradation, which is more difficult to study. Here, we performed a systematic review of studies on moist tropical forest degradation using remote sensing and fitting indicators of forest resilience to perturbations. Geographical repartition, spatial extent and temporal evolution were analyzed. Indicators of compositional, structural and regeneration criteria were noted as well as remote sensing indices and metrics used. Tropical moist forest degradation is not extensively studied especially in the Congo basin and in southeast Asia. Forest structure (i.e., canopy gaps, fragmentation and biomass) is the most widely and easily measured criteria with remote sensing, while composition and regeneration are more difficult to characterize. Mixing LiDAR/Radar and optical data shows good potential as well as very high-resolution satellite data. The awaited GEDI and BIOMASS satellites data will fill the actual gap to a large extent and provide accurate structural information. LiDAR and unmanned aerial vehicles (UAVs) form a good bridge between field and satellite data. While the performance of the LiDAR is no longer to be demonstrated, particular attention should be brought to the UAV that shows great potential and could be more easily used by local communities and stakeholders.
Simon Lhoest
added 9 research items
Des dizaines de millions de personnes dépendent des forêts tropicales pour leur subsistance en Afrique centrale. Ces écosystèmes abritent une biodiversité unique et fournissent d'importants services écosystémiques (SE), qui peuvent varier en fonction des stratégies de gestion. Dans cette thèse de doctorat, nous avons évalué la biodiversité et les services écosystémiques dans le paysage du Dja au Cameroun, dans trois affectations des terres forestières : une aire protégée, une concession forestière certifiée FSC et trois forêts communautaires. Tout d'abord, nous avons évalué la valeur de conservation des forêts sur la base de la richesse et de la composition en espèces de deux groupes taxonomiques : les mammifères et les bousiers. Les espèces les plus grandes et les plus menacées ont été détectées dans l’aire protégée et les zones les plus éloignées de la concession forestière, mieux préservées de l'influence humaine. En revanche, les forêts communautaires sont particulièrement défaunées et dégradées en raison de leur proximité avec les routes et les villages, mais elles couvrent des superficies beaucoup plus limitées et conservent une canopée fermée. Deuxièmement, des entretiens identifiant les perceptions de l'offre en SE ont montré que, contrairement aux services de régulation qui ont été rarement mentionnés, les services d’approvisionnement et culturels sont les plus importants pour les populations locales. Parmi ceux-ci, la viande de brousse est le seul service pour lequel l’offre de la forêt n’est pas suffisante pour les populations locales. Troisièmement, en combinant des entretiens et enquêtes de terrain, nous avons quantifié l'utilisation de huit SE d'approvisionnement et culturels par les populations locales. Nous avons constaté que le bois de feu et le bois d'œuvre sont utilisés de manière durable par les populations locales, tandis que la chasse et la consommation de viande de brousse dépassent les seuils de durabilité. Concilier la conservation de la faune sauvage, la sécurité alimentaire et les pratiques de chasse durable est un défi majeur en Afrique centrale. Pour ce faire, il est essentiel d’intégrer toutes les parties prenantes dans les stratégies de gestion forestière durable, permettant d’identifier les leviers sociaux qui sous-tendent les changements de comportement des utilisateurs des forêts.
In Central Africa, local populations are deeply dependent on tropical forests, which provide numerous ecosystem services (ES). For the first time in Central Africa, we assessed the perceptions of ES provided by tropical forests to local populations, considering three land allocation types: a protected area, a Forest Stewardship Council (FSC)-certified logging concession, and three community forests. We conducted a questionnaire survey with 225 forest stakeholders in southeastern Cameroon, combining an open-ended question and 16 directed questions to evaluate the perceptions of ES significance and abundance, respectively. The ES most frequently reported as significant were provisioning (93% of respondents) and cultural & amenity services (68%), whereas regulating services were less mentioned (16%). Bushmeat provision was the only ES perceived as highly significant but not very abundant. There were slight variations of perceptions among forest land allocation types and respondents, suggesting a relative homogeneity in ES abundance. For further integrative ES assessment, we suggest quantifying ES with complementary ecological and economic approaches, such as meat provision, recreation, tourism, timber provision, spiritual experience, firewood provision, water quality regulation, and inspiration for culture. We also give three concrete recommendations for forest management, the most urgent being to provide sources of protein alternative to bushmeat.
Camera traps (CTs) have been increasingly used for wildlife monitoring worldwide. In the tropics, most CT inventories target wildlife‐friendly sites, and CTs are commonly placed towards wildlife trails. However, it has been argued that this placement strategy potentially provides biased results in comparison to more systematic or randomized approaches. Here, we investigated the impact of CT placement on the remotely sensed mammal diversity in a tropical forest in Gabon by comparing pairs of systematically placed and wildlife‐trail‐oriented CTs. Our survey protocol consisted of 15–17 sampling points arranged on a 2 km2 grid and left for one month in the field. This protocol was replicated sequentially in four areas. Each sampling point comprised a CT pair: the ‘systematic CT’, installed at the theoretical point and systematically oriented towards the most uncluttered view; and the ‘trail CT’, placed within a 20‐m radius and facing a wildlife trail. For the vast majority of species, the detection probabilities were comparable between placements. Species average capture rates were slightly higher for trail‐based CTs, though this trend was not significant for any species. Therefore, the species richness and composition of the overall community, such as the spatial distribution patterns (from evenly spread to site‐restricted) of individual species, were similarly depicted by both placements. Opting for a systematic orientation ensures that pathways used preferentially by some species—and avoided by others—will be sampled proportionally to their density in the forest undergrowth. However, trail‐based placement is routinely used, already producing standardised data within large‐scale monitoring programmes. Here, both placements provided a comparable picture of the mammal community, though it might not be necessarily true in depauperate areas. Both types of CT data can nevertheless be combined in multi‐site analyses, since methods now allow accounting for differences in study design and detection bias in original CT data.
Gauthier Ligot
added a project goal
The CARE Forest is life aims to study forest ecosystems and, more generally, landscape structures with a low degree of anthropisation, whether in temperate or tropical regions.