References of "Haurez, Barbara"
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See detailShort term impact of selective logging on a western lowland gorilla population
Haurez, Barbara ULg; Tagg, Nikki; Petre, Charles-Albert ULg et al

in Forest Ecology & Management (2016), 364

Selective timber production is implemented over a large proportion of the world’s tropical forests. Within these forest ecosystems, the frugivore community contributes important ecological services ... [more ▼]

Selective timber production is implemented over a large proportion of the world’s tropical forests. Within these forest ecosystems, the frugivore community contributes important ecological services through animal-mediated seed dispersal. However, there is no clear understanding of the impacts of logging on wildlife or of the extent to which seed dispersal is preserved in logged forests. Given its tendency for nesting in light gaps, the western lowland gorilla is likely to provide directed-dispersal services to a wide range of tree species. Production forests preserved from poaching have been reported to harbor high densities of gorillas, but the monitoring of gorilla populations subjected to logging is poorly documented. This study investigated gorilla density and nesting behavior after timber exploitation in a logging concession in southeast Gabon. Nest count censuses were performed on line transects, before and after the second felling cycle. Gorilla density dropped from 1.5 (116.7 nests km 2, 95% CI = 83.4–163.5) to 1.0 (64.9 nests km 2, % CI = 32.6–129.5) weaned gorilla km 2 4–6 months after logging, then rose to 2.6 (176.3 nests km 2, 95% CI = 113.5–274.1) gorillas km 2 9–11 months after logging. A consistent preference for nesting in open canopy terra firma forest was observed during all censuses. This study demonstrates the short-term resilience of the western lowland gorilla to selective timber harvesting, and argues that they offer a continued contribution to directed-dispersal services within months after logging. Although a long-term monitoring of gorillas in a logged forest should be undertaken, the role of this species in logged forest recovery is thought to be important. The preservation of gorilla should receive particular consideration by forest managers. [less ▲]

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See detailRôle du gorille des plaines de l’Ouest (Gorilla gorilla gorilla) dans la régénération des forêts denses humides et interaction avec l’exploitation sélective de bois d’oeuvre
Haurez, Barbara ULg

Doctoral thesis (2015)

According to the IUCN, the western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) is a critically endangered species. This species would play an important role in tropical forest dynamics ... [more ▼]

According to the IUCN, the western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) is a critically endangered species. This species would play an important role in tropical forest dynamics. Indeed, its highly frugivorous diet and its large body mass would result in the implication of gorilla in the seed dispersal of many plant species. Moreover, by building its nest sites in open canopy forest, it would deposit the majority of seeds in habitats displaying potentially suitable light condition for their germination and for the subsequent seedling development. However, given the expansion of timber exploitation in Central Africa, ecological services dispensed by gorilla could be threatened. The objective of this thesis is to characterize the impacts of timber exploitation on gorilla populations and the role of these populations in forest regeneration after logging. The results demonstrate that a viable population of gorilla may be maintained in selectively logged forests (< 2 trees ha-1). Indeed, although gorillas tend to flee areas during timber exploitation activities, their density in logged forest reaches its initial value, or even a higher level, within one year after the end of logging. The preferential selection of open canopy forest areas for nesting was verified, before and after logging. The deposition of seeds in habitats providing favorable light conditions is therefore confirmed, even though the preference for tree fall gaps and forest skid trails was not observed in the course of the monitoring period (one year after logging). The seeds of 59 plant species were found in gorilla feces collected over a period of 20 months. A quarter of these species presented an economically value because of their use as timber or non-timber forest products. The analyzed fecal units contained between one and six different seed species, and on average 81.0 ± 107.8 intact seeds (0-566). Depending on the species considered, germination success varied from 0 to 100 %, with an average of 46 ± 36 %. The gorilla is the main disperser of a timber species, Dacryodes normandii. Over the fructification period, the gorilla consumed fruits of this species in 87.8 % of its visits (of an average length of 85 ± 89 min.). The impact of gut passage was evaluated for two tree species, Santiria trimera and Chrysophyllum lacourtianum. These species displayed higher germination successes after gorilla ingestion because of both pulp suppression and seed coat scarification. In addition, a positive effect of fecal matrix on seedling development was observed for three studied species, S. trimera, C. lacourtianum and Plagiostyles africana. Finally, the development of seedlings is favored in nesting sites, the most frequent seed deposition sites. Two studied species, S. trimera and Dacryodes normandii displayed a growth between two and ten times faster in nest sites than in closed canopy forest. Therefore, gorilla is implicated in directed seed dispersal. Consequently, when poaching is absent, western lowland gorilla populations seem to be resilient to selective logging and they play a critical role in the seed dispersal process, both quantitatively and qualitatively, in logged forests. Some recommendations to improve the management of logged forest that host gorilla populations were proposed in order to favor their preservation within logging concessions. In particular, the generalization of reduced impact logging practices is advisable. [less ▲]

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See detailIs western lowland gorilla a good gardener? Effect of fecal matrix and deposition at nest sites on seedling growth
Haurez, Barbara ULg; Brostaux, Yves ULg; Petre, Charles-Albert ULg et al

Conference (2015, June 25)

The Western lowland gorilla is a key dispersal agent, which disperses viable seeds of various size. In consequence of its nesting behavior, gorilla deposits half of its feces, and therefore about half of ... [more ▼]

The Western lowland gorilla is a key dispersal agent, which disperses viable seeds of various size. In consequence of its nesting behavior, gorilla deposits half of its feces, and therefore about half of dispersed seeds, at nest sites. This study was conducted in a logging concession of southeast Gabon where 78 % of the observed nest sites (n=183) were installed in open canopy terra firma forest. The aim of this research was to assess if seed deposition by gorillas (i) in fecal matrix and (ii) at nest sites is advantageous for seedling growth. To assess the effect of fecal matrix, seeds of Santiria trimera (Burseraceae), Chrysophyllum lacourtianum (Sapotaceae) and Plagiostyles africana (Euphorbiaceae) collected in gorilla feces were sown with and without fecal matrix in a nursery at the study site. The impact of seed deposition at nest sites on seedling growth was evaluated in situ. Seedlings of Santiria trimera and Dacryodes normandii (Burseraceae) were installed at nest sites and at closed canopy terra firma forest sites. For both type of trials, seedling growth was monitored. [less ▲]

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See detailQuantity and spatial distribution of seeds dispersed by a western lowland gorilla population in south-east Cameroon
Petre, Charles-Albert ULg; Tagg, Nikki; Beudels-Jamar et al

in Journal of Tropical Ecology (2015), 35(03), 201-212

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See detailDifferences in dung beetle activity at western gorilla defecation sites in south-east Cameroon: implications for establishment of Uapaca spp. seedlings
Petre, Charles-Albert ULg; Zinque, Marie-Hélène; Tagg, Nikki et al

in Journal of Tropical Ecology (2015), 31(02), 161-174

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See detailWestern lowland gorilla seed dispersal: Are seeds adapted to long gut retention times?
Petre, Charles-Albert ULg; Tagg, Nikki; Beudels-Jamar, Roseline et al

in Acta Oecologica: International Journal of Ecology (2015), 67

The degree of seed scarification in the frugivore gut, partly dependent on gut retention time, is a key component in determining the extent to which gut passage alters germination performances. Another ... [more ▼]

The degree of seed scarification in the frugivore gut, partly dependent on gut retention time, is a key component in determining the extent to which gut passage alters germination performances. Another potential benefit of gut passage arises as a result of the removal of fruit pulp which otherwise may act as a germination inhibitor. Using experiments designed to disentangle the respective effects of pulp removal (germination deinhibition) and seed scarification, and gut retention time as an explanatory variable, we investigated the effect of gut passage on germination performances (percentage and latency) of five tropical tree species dispersed by the western lowland gorilla (Gorilla g. gorilla). The percentage of seeds germinating after gut passage increased for three species, respectively, through the effects of scarification only, deinhibition only, and scarification and deinhibition combined. A negative scarification effect was observed for one species, and no effect of gut passage for another. Passage through the gut led to a decrease in germination latency of three species, as a result of the depulping of seeds. However, seed scarification resulted in germination delays for another species. The gut retention time of the five species averaged 39e56 h and had no effect on intra-specific germination performances except for one species whose germination probability increased as gut retention time increased. As gut retention time often correlates with dispersal distance, the fact that gut retention time per se does not reduce seed viability of these tropical tree species may have positive implications for their population dynamics and maintenance of genetic diversity. If no detrimental effect of gut retention time on germination performance is a general trait among tropical species, the extirpation of large frugivores with long gut retention time, such as the western lowland gorilla, would likely have negative long-term implications for tropical forests. [less ▲]

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See detailIs the western lowland gorilla a good gardener ? Evidence for directed dispersal in Southeast Gabon
Haurez, Barbara ULg; Brostaux, Yves ULg; Petre, Charles-Albert ULg et al

in Bois et Forêts des Tropiques (2015), 324(2), 39-50

In Central African tropical forests, the western lowland gorilla deposits most of the seeds it disperses in well-lit nesting sites that can favour seedling growth. The faecal matrix surrounding the seeds ... [more ▼]

In Central African tropical forests, the western lowland gorilla deposits most of the seeds it disperses in well-lit nesting sites that can favour seedling growth. The faecal matrix surrounding the seeds can act as a fertiliser and further enhance seedling development. This fertilisation effect had never been tested. Our research therefore aimed to determine whether seed deposition by gorillas (i) in faecal matter and (ii) in nest sites is advantageous for seedling development (growth rate and foliation rate) and survival (% of surviving seedlings). To assess the effect of the faecal matrix, seeds of Santiria trimera (Burseraceae), Chrysophyllum lacourtianum (Sapotaceae) and Plagiostyles africana (Euphorbiaceae) collected from gorilla faeces were sown in a nursery with and without a faecal matrix. Seedlings of Santiria trimera and Dacryodes normandii (Burseraceae) were established in nest sites and in closed canopy terra firme forest sites to assess the impact of seed deposition on seedling development and survival. The faecal matrix was observed to positively influence seedling development in the species studied, but showed no effect on survival. Regarding seed deposition sites, the development rates observed were two to ten times higher in the nest sites than in closed-canopy forest. This enhanced seedling development was positively correlated with canopy openness. In situ studies of seed germination, seedling growth and survival are needed to characterise the fate of gorilla-dispersed seeds more precisely. However, our results offer evidence that gorillas provide important directed dispersal services by depositing seeds most frequently in open canopy sites. [less ▲]

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See detailThe role of great apes in seed dispersal of the tropical forest tree species Dacryodes normandii (Burseraceae) in Gabon
Haurez, Barbara ULg; Daïnou, Kasso ULg; Tagg, Nikki et al

in Journal of Tropical Ecology (2015), 31(05), 395-402

The identification of seed dispersers and predators is essential to understand the effect of anthropogenic disturbances, and the associated defaunation process, on tropical forest dynamics in Central ... [more ▼]

The identification of seed dispersers and predators is essential to understand the effect of anthropogenic disturbances, and the associated defaunation process, on tropical forest dynamics in Central Africa. In this study, the animals involved in seed predation and dispersal of Dacryodes normandii (Burseraceae), an endozoochorously dispersed tree species endemic to Gabonese forests, were identified in a site in south-east Gabon using two complementary methods: direct observation and camera-trap monitoring of fruit piles. The combined sampling effort (172 h of direct observations and 796 d of camera trapping) led to the identification of six disperser and eight predator species of D. normandii seeds. With high frequency of consumption (88% and 57% of their visits, respectively) and long visit duration (83 and 23 min, respectively), the western lowland gorilla and central chimpanzee were identified as the main dispersers of this species. Seeds passed through the gorilla gut exhibited high germination success (68%). Rodents were identified as predators of D. normandii seeds, potentially displaying rare secondary dispersal through scatter-hoarding. The results of this study highlight the importance of great apes in the seed dispersal of this tree species. [less ▲]

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See detailSeed dispersal by western lowland gorillas: what about gut passage effect?
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2014, July 21)

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of ... [more ▼]

Animal-mediated seed dispersal is an essential ecological process in the tropics. Among African primates, the critically endangered western lowland gorilla (WLG) seems to fulfill many characteristics of an effective seed disperser. WLG preferentially disperses species of various seed-size into open canopy habitats suitable for seedling growth. However, few studies have addressed the effects of the passage through the digestive tract on germination. Thus, the effectiveness of WLG in ecological processes governing forest dynamics and regeneration is still poorly known. Seed dispersal by WLG was studied in Central Gabon and Southeast Cameroon. Dispersed seed were identified from fresh fecal samples. Comparative germination trials based on 5 treatments (seeds from fresh fruits, seeds from fresh fruits surrounded by pulp, seeds from fresh fruits with fecal matrix, seeds from feces and seeds from feces with fecal matrix) were realized for 13 species. We recorded germination success for all species and germination delay for 6 species. Our results suggest a neutral gut passage effect for 54% and positive effect for 40% of tested species. Germination success enhancement was linked to another factor than pulp suppression. For two species, pulp suppression enhanced germination success, but not gut passage. The presence of pulp or fecal matrix surrounding the seed seemed to longer germination delay, while gut passage would not fasten germination. Globally, we conclude that WLG dispersed seeds are not damaged by gut passage. Consequently, WLG is thought to provide effective ecological services that could be essential to the maintenance and the recovery of forest ecosystems. [less ▲]

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See detailWestern lowland gorilla in a logging concession: comparison of density and nesting behavior before and after logging
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Conference (2014, May 22)

Timber exploitation is rapidly expanding throughout the Congo Basin. In Gabon, timber industry is currently the second working sector and logging concessions cover 45% of the country forest area, largely ... [more ▼]

Timber exploitation is rapidly expanding throughout the Congo Basin. In Gabon, timber industry is currently the second working sector and logging concessions cover 45% of the country forest area, largely overlapping with the range of western lowland gorilla (Gorilla gorilla gorilla WLG). Logging may negatively impact gorilla because of an increase in hunting pressure linked to human concentration and easier access to forest. On the other hand, WLG might benefit from forest opening and the associated growth in Terrestrial Herbaceous Vegetation, following timber felling and roads/trails implementation. In the present study, gorilla density and nesting behavior were studied in a 617,000-ha logging concession located in Central Gabon. A Standing Crop Nest Count census was realized 25 years after the first timber harvesting cycle, consisting in the assessment of the potentiality of logged forest to hold viable WLG populations. A second census was undertaken four to six months after the second logging wave. Comparing nesting behavior and estimated gorilla density between the two census allows to highlight the short-term effects of logging on gorilla populations. A relatively high WLG density was observed during the first census (2.1 weaned gorillas/km²). This figure dropped down to 1.0 weaned gorillas/km² after the second felling cycle. Both density values fall within the range of documented WLG densities documented at other sites. Gorillas consistently nested preferentially in open terra firme forest and built the majority of their nests using herbs of the Marantaceae and Zingiberaceae families. Both these observations underline the importance of Terrestrial Herbaceous Vegetation for nesting. The results of this study suggest that timber exploitation and WLG conservation are not mutually exclusive. The initial high density might traduce an effective anti-poaching strategy for now. The decline in gorilla density observed directly in the second census is probably linked with the avoidance of the disturbance of logging operations. Monitoring the evolution of WLG density would be important in order to control if the figure will rise over time to reach its initial value, but also to assess if a positive effect of Terrestrial Herbaceous Vegetation growth will be observed. [less ▲]

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See detailLes concessions forestières peuvent-elles contribuer à la conservation du gorille des plaines de l'Ouest? Exemple d'une concession au Sud-Est du Gabon
Haurez, Barbara ULg; Petre, Charles-Albert ULg; Doucet, Jean-Louis ULg

Poster (2013, November)

Vingt pourcents des forêts du Bassin du Congo sont actuellement principalement affectées à la production de produits ligneux et non-ligneux [FAO-OIBT, 2011]. L'exploitation est un agent de perturbation de ... [more ▼]

Vingt pourcents des forêts du Bassin du Congo sont actuellement principalement affectées à la production de produits ligneux et non-ligneux [FAO-OIBT, 2011]. L'exploitation est un agent de perturbation de ces forêts [WILKIE ET AL., 2000]. Au vu de l’importance économique des industries d’extraction pour les pays de cette région, l’étendue des forêts exploitées pour leur bois ne devrait pas diminuer dans les années à venir, au contraire. La survie de nombreuses espèces animales de forêt dense humide dépend donc de leur capacité à survivre en milieu exploité [JOHNS, 1985]. A ce jour, les concessions forestières jouent potentiellement un rôle crucial pour la protection des différentes espèces de grands singes. En effet, plus de 50% de l'aire de distribution des grands singes d’Afrique de l'Ouest est localisée dans les concessions forestières [MORGAN & SANZ, 2007]. Or, la faune sauvage joue un rôle essentiel pour la durabilité de l'exploitation forestière car elle assure la dissémination des graines [WRIGHT, 2003], dont celles des espèces commerciales. En particulier, le gorille des plaines de l'Ouest (Gorilla gorilla gorilla Savage & Wyman, 1847), espèce en danger critique d'extinction (IUCN), semble jouer un rôle fondamental dans la dispersion des diaspores des espèces ligneuses [ROGERS ET AL., 1998 ; VOYSEY ET AL., 1999]. Cette étude vise à déterminer les interactions entre les gorilles des plaines de l'Ouest et l'exploitation forestière, afin d'évaluer dans quelle mesure ces deux acteurs peuvent être bénéfiques l'un envers l'autre. Plus particulièrement, la densité en gorilles a été estimée dans une zone exploitée 25 ans plus tôt. Le comportement nidificateur des gorilles dans cette zone a été décrit. D'autre part, le rôle potentiel joué par les gorilles dans la dynamique de régénération des forêts exploitées est abordé au travers de l'étude de la dispersion des graines (identification des graines dispersées, contrôle du pouvoir germinatif et détermination de l'impact du passage dans le tractus digestif sur la germination). La densité en gorilles observée au sein du site d'étude est relativement élevée (1,5 gorille/km²). Les gorilles établissent leurs sites de nidification préférentiellement au sein de forêts de terre ferme à canopée ouverte. Ils utilisent fréquemment les anciennes routes d'exploitation, densément couverte de végétation herbacée, pour l'alimentation et la nidification. Au bout de 10 mois de suivi, 45 espèces végétales ont été identifiées comme étant dispersées par les gorilles. Le potentiel germinatif a été évalué pour 36 taxons. Les taux de germination observés dépendent de l'espèce considérée, et varient de 0 à 100%. L'impact du tractus digestif sur la germination a actuellement été testé pour deux espèces, Santiria trimera (Burseraceae) et Chrysophyllum lacourtianum (Sapotaceae). Pour ces deux espèces, les graines passées dans le tractus digestif des gorilles présentent des taux de germination significativement plus élevé que les graines extraites de fruits frais (entourées de pulpe ou non). Les résultats préliminaires de cette étude suggèrent que les forêts exploitées peuvent supporter des densités en gorilles comparables à celles des aires protégées. En outre, via son rôle en tant que disperseur, le gorille pourrait avoir un rôle crucial dans la régénération des forêts post-exploitation. L'exploitation forestière et la conservation des gorilles des plaines de l'Ouest paraissent donc compatibles. [less ▲]

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