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During inventories of lesser-known timber species in eastern Gabon, a new Dialium morphospecies was discovered. To discriminate it from the two other 2–5 leaflets Dialium species, 25 leaf traits were measured on 45 trees (16 Dialium pachyphyllum, 14 Dialium lopense, 15 Dialium sp. nov.). Nine wood chemical traits, as well as infrared spectra, were also examined on harvestable trees (four Dialium pachyphyllum and four Dialium sp. nov.). This study revealed seven discriminant leaf traits that allowed to create a field identification key. Nine significant differences (five in sapwood and four in heartwood) in terms of wood composition were highlighted. The use of the PLS-DA technique on FT-IR wood spectra allowed to accurately identify the new morphospecies. These results provide strong support for describing a new species in this genus. Implications for sustainable management of its populations are also discussed. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]

Aim: Large trees [≥ 70 cm diameter at breast height (DBH)] contribute disproportionately to aboveground carbon stock (AGC) across the tropics but may be vulnerable to changing climate and human activities. Here we determine the distribution, drivers and threats to large trees and high carbon forest. Location: Central Africa. Time period: Current. Major taxa studied: Trees. Methods: Using Gabon's new National Resource Inventory of 104 field sites, AGC was calculated from 67,466 trees from 578 species and 97 genera. Power and Michaelis–Menten models assessed the contribution of large trees to AGC. Environmental and anthropogenic drivers of AGC, large trees, and stand variables were modelled using Akaike's information criterion (AIC) weights to calculate average regression coefficients for all p ossible models. Results: Mean AGC for trees ≥ 10 cm DBH in Gabonese forestlands was 141.7 Mg C/ha, with averages of 166.6, 171.3 and 96.6 Mg C/ha in old growth, concession and secondary forest. High carbon forests occurred where large trees are most abundant: 31% of AGC was stored in large trees (2.3% of all stems). Human activities largely drove variation in AGC and large trees, but climate and edaphic conditions also determined stand variables (basal area, tree height, wood density, stem density). AGC and large trees increased with distance from human settlements; AGC was 40% lower in secondary than primary and concession forests and 33% higher in protected than non‐managed areas. Main conclusions: AGC and large trees were negatively associated with human activities, highlighting the importance of forest management. Redefining large trees as ≥ 50 cm DBH (4.3% more stems) would account for 20% more AGC. This study demonstrates that protecting relatively undisturbed forests can be disproportionately effective in conserving carbon and suggests that including sustainable forestry in programs like reduced emissions for deforestation and forest degradation could maintain carbon dense forests in logging concessions that are a large proportion of remaining Central African forests. [ABSTRACT FROM AUTHOR]

Species delimitation remains a crucial issue for widespread plants occurring across forest-savanna ecotone such as Lophira (Ochnaceae). Most taxonomists recognize two parapatric African tree species, widely distributed and morphologically similar but occurring in contrasted habitats: L. lanceolata in the Sudanian dry forests and savannahs and L. alata in the dense Guineo-Congolian forests. Both species co-occur along a ca. 3000 km long forest-savanna mosaic belt, constituting ideal models for investigating hybridization patterns and the impact of past glacial periods on the genetic structures in two types of ecosystems. We genotyped 10 nuclear microsatellites for 803 individuals sampled across the distribution range of Lophira. Both species exhibit similar levels of genetic diversity [He = 0.52 (L. alata); 0.44 (L. lanceolata)] and are well differentiated, consistent with taxonomic delimitation (FST = 0.36; RST = 0.49), refuting the hypothesis that they might constitute ecotypes rather than distinct species. Furthermore, L. alata displayed two deeply differentiated clusters (FST = 0.37; RST = 0.53) distributed in parapatry, one endemic to Western Gabon while another cluster extended over the remaining species range, suggests that L. alata is made of two cryptic species. We showed that rare hybrids occur in some contact zones between these three species, leaving a weak signal of introgression between L. lanceolata and the northern cluster of L. alata. At the intra-specific level, the latter species also show weak genetic structuring between Upper and Lower Guinea and the intensity did not differ strikingly between rainforest and savanna ecosystems. The discovery of a new species of Lophira with a narrow distribution in West Gabon where it is intensively exploited for its timber requires to evaluate its conservation status. [ABSTRACT FROM AUTHOR]

Crop damage by forest elephants (Loxodonta africana cyclotis) and the resulting human-elephant conflict are issues of great concern for both the conservation of the species and the protection of rural livelihoods in Central Africa. Addressing these problems requires identifying the factors that facilitate or impede crop-raiding by forest elephants. Yet to date, the environmental or anthropogenic factors that influence the occurrence and intensity of crop-raiding by forest elephants are largely unknown. We used a multivariate approach to investigate conditions under which forest elephants raid some fields and not others in the buffer zone of Monts de Cristal National Park (MCNP), Gabon. We first interviewed 121 farmers from 11 villages situated within 10 km of MCNP regarding the occurrence of elephant crop-raiding of their fields. We then collected data on 39 explanatory variables to characterize the agricultural fields. Of these, the most important predictors of elephant raid occurrence of crop damage were presence of fruit trees, elephant deterrents (scarecrows, fire, wire string fences and empty barrels), and field topography. We secondly assessed the effect of stage of crop growth, presence of fruit trees, field topography and presence of elephant deterrents on crop-raiding occurrence and intensity by counting raids and measuring areas of crop damage every week in 17 plantations over 19 weeks in the most elephant-impacted zone of the study area. We found that fruit presence and stage of crop growth led to more intense damage to crops, whereas local deterrents did not inhibit raiding events and crop damage by elephants. We report a tradeoff between non-timber forest products (NTFP) services and crop-raiding by elephants. We show for the first time that steep topography impedes elephant damage to crops with no raids recorded in fields with surrounding slopes greater than 25%. We discuss whether farming on steep fields could be used as a strategy for mitigating crop-raiding to favor human-elephant coexistence and enhance elephant conservation. [ABSTRACT FROM AUTHOR]

• Cylicodiscus gabunensis is an important timber species with a poor regeneration in evergreen forest. • This study aims to define the conditions needed for optimal regeneration and silviculture of C. gabunensis in Gabon. • Establishment of the studied population coincides with the abandonment of agricultural land 148 years ago. • Cylicodiscus gabunensis stems are located on soil with relatively high content in Fe, K, P and total nitrogen. Despite the implementation of management plans, commercial tree species densities are declining in the forests of Central Africa. In the region, Cylicodiscus gabunensis Harms (Fabaceae-Caesalpinioideae; common name 'okan'), is one such species most exploited, but its ecology remains poorly understood. The rarity of its regeneration in evergreen forest suggests that, like other commercial light-demanding species, the conditions that allowed populations to become established are no longer present. Using a combined archaeobotanical and pedological approach, the aim of this study is to identify the factors explaining the current distribution of C. gabunensis individuals at local scale. Within a plot of 1050 ha in a forest concession in south-eastern Gabon, we installed 40 archaeological pits equally divided between sites with and without C. gabunensis. The artefacts encountered were collected and analysed. Charcoal masses were quantified and 18 charcoals were dated. These ages were compared with the average age of the tree population, using growth data from 50 individuals and heartwood dating from 4 individuals. An analysis of the physico-chemical properties of the soil was carried out on composite samples from each archaeological pit. Pottery sherds were found in two pits while charcoal was present in all pits, suggesting widespread human occupation and fire throughout the study area. Human occupation occurred in two phases: between 2480 and 1010 BP and from 590 to 80 BP. The abandonment of agricultural land at the end of this second phase could coincide with the establishment of the C. gabunensis cohort whose average age has been estimated at between 90 and 148 years. Soil analyses showed that C. gabunensis individuals were located on soils that were comparatively richer in element potentially toxic (Fe) and in some plant nutrients (K, P) and total nitrogen. The current scarcity of young trees argues for the implementation of a silviculture that integrates the light requirements of the species as well as the chemical fertility of the soil. [ABSTRACT FROM AUTHOR]

The African walnut ( Coula edulis) is a tree species of African evergreen forests, the seeds of which are collected and traded by African people. Many animal species consume African walnut diaspores; however, their roles as dispersers or predators have yet to be clarified. In this study, we present observations conducted in two different habitats of a Gabonese region over a 3-year period. The originality of this research resides in the combination of three complementary approaches: (i) the use of camera-traps (ii) the exploration of land rodent burrows and (iii) the examination of elephant dung. In total, 408 camera-trap photographs have shown seven animal species involved in the dispersal/predation of C. edulis. Among these seven frugivorous species, the bush pig was found to be the main consumer and predator of seeds. Land rodents (Muridae) are potential predators, as they damaged the seeds and buried them deep in the soil. They may also play a role in the regeneration process as a result of the loss of seeds during transportation. Finally, no seeds appeared to emerge intact from elephant faeces. These results indicate that the natural regeneration rate of this tree species is low, unless other complex mechanisms are involved. [ABSTRACT FROM AUTHOR]

Copyright of Biotechnologie, Agronomie, Societe et Environnement is the property of Les Presses Agronomiques de Gembloux and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simple Summary: Forest duikers are one of the most important groups of mammals in Central African rainforests and over the whole Guineo-Congolian Region. To better understand the mechanisms of habitat use and sharing among duiker species, we quantified duiker activity, temporal and spatial interactions. Data were collected using camera traps over five years, in 12 sites scattered in four countries: Cameroon, Congo, Democratic Republic of Congo, and Gabon. We found that duikers usually have two main peaks of activity, which are mostly dependent on sunrise and/or sunset. In addition, analyses of temporal interactions (for five species) identified four species pairs with strong interactions and six pairs with weak interactions. Spatial interaction tests revealed no competitive habitat use among species. Our results contribute to a better understanding of the ecology of duikers in Central African rainforests, in order to improve their conservation and management. The duiker community in Central African rainforests includes a diversity of species that can coexist in the same area. The study of their activity patterns is needed to better understand habitat use or association between the species. Using camera traps, we studied the temporal activity patterns, and quantified for the first time the temporal overlap and spatial co-occurrence between species. Our results show that: (i) Two species are strongly diurnal: Cephalophus leucogaster, and Philantomba congica, (ii) two species are mostly diurnal: C.callipygus and C. nigrifrons, (iii) one species is strongly nocturnal: C.castaneus, (iv) and one species is mostly nocturnal: C.silvicultor. Analyses of temporal activities (for five species) identified four species pairs that highly overlapped ( Δ ^ ≥   0.80), and six pairs that weakly overlapped ( Δ ^ between 0.06 and 0.35). Finally, co-occurrence tests reveal a truly random co-occurrence (plt > 0.05 and pgt > 0.05) for six species pairs, and a positive co-occurrence (pgt < 0.05) for four pairs. Positive co-occurrences are particularly noted for pairs formed by C.callipygus with the other species (except C. nigrifrons). These results are essential for a better understanding of the coexistence of duikers and the ecology of poorly known species (C. leucogaster and C. nigrifrons), and provide clarification on the activity patterns of C. silvicultor which was subject to controversy. Camera traps proved then to be a powerful tool for studying the activity patterns of free-ranging duiker populations. [ABSTRACT FROM AUTHOR]