References of "Gourlet-Fleury, Sylvie"
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See detailVariation of tree allometry and aboveground biomass in central African forests
Loubota Panzou, Grâce Jopaul ULiege; Ligot, Gauthier ULiege; Bastin, Jean-François et al

Conference (2017, August 23)

Quantifying the biomass and carbon stocks contained in tropical forests has become an international priority for the implementation of the REDD+ initiative. Many techniques exist to estimate forest ... [more ▼]

Quantifying the biomass and carbon stocks contained in tropical forests has become an international priority for the implementation of the REDD+ initiative. Many techniques exist to estimate forest biomass at different spatial scales, but all ultimately rely on allometric equations calibrated on destructive measurements of individual tree biomass, in order to convert forest inventory data into biomass estimates. For many tropical forest ecosystems, that are structurally complex and species rich, these allometric equations have not yet been developed and general allometric equations are being used instead, with possibly local adjustment of tree allometry with non-destructive data. Variation in height-diameter allometry and in crown-diameter allometry across forest types and environmental conditions have been demonstrated to be of extreme importance for the estimation of biomass and carbon stocks in tropical forests, but yet poorly explored in central Africa. In this study we aimed to determine the variation in tree height-diameter and crown-diameter allometries across central African forests and the consequences for biomass and carbon stocks. Tree allometry data were collected in two of semi-deciduous forest sites in northern Republic of Congo that have vastly different substrate and soils (clay soils on quartzite and sandy soils on sandstone plateau), and forest communities, but similar rainfall regimes. These data will be analyzed to test two hypotheses: (i) tree allometry strongly varies across forest types with contrasted environmental conditions (and specifically soils), and (ii) both allometry and forest structure contributed to the greater biomass of the site on rich soil (quartzite substrate). Our newly collected data for two sites in northern Congo will be confronted to existing allometry and inventory data available elsewhere in the Congo basin to get a broader picture of allometric variations and its consequences for the estimation of biomass and carbon stocks. [less ▲]

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See detailA look at Intact Forest Landscapes and their relevance to Central African forest policy
Haurez, Barbara ULiege; Daïnou, Kasso ULiege; Vermeulen, Cédric ULiege et al

Conference (2017, February)

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation ... [more ▼]

Tropical forests are important providers of natural resources and ecosystem services but their ecological functions are facing increasing human pressure, linked to economic development. The preservation of tropical forest ecosystems is interrelated with effective land use planning and identification of priority areas for conservation. Initially defined by Greenpeace and the World Resources Institute (WRI) in 2000, Intact Forest Landscapes (IFLs) are large areas of forest minimally impacted by human activities. IFLs were identified by mapping industrial activities, road networks and infrastructure using remote sensing. Since 2014, when IFLs were recognized and adopted by the certification scheme Forest Stewardship Council (FSC), the IFLs have become integrated into forest management policies. In order to trace the history and evaluate the applicability of IFLs for forest management policy in the Central African context, we searched for documents related to the IFL method, and previous similar concepts. The IFL method is simple and cost-effective and enables the monitoring of forest degradation at a global scale. However, the approach mainly considers forest cover and is imprecise at the local scale. For example, hunting, one of the main threats faced by Central African ecosystems, cannot be detected by satellite imagery and is therefore disregarded in IFL identification processes. In contrast, there are other considered anthropogenic activities, such as reduced-impact selective logging, which may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities distribution in the analysis of disturbance, (ii) a thorough evaluation of the impacts of different human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies devised to address social, economic and environmental needs. [less ▲]

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See detailPresent-day central African forest is a legacy of the 19th century human history
Morin, Julie ULiege; Fayolle, Adeline ULiege; Favier, Charly et al

in eLife (2017)

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 ... [more ▼]

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. [less ▲]

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See detailDeforestation and timber production in Congo after implementationof sustainable management policy: A reaction to the article by J.S.Brandt, C. Nolte and A. Agrawal (Land Use Policy 52:15–22)
Karsenty, Alain; Romero, Claudia; Cerutti, Paolo Omar et al

in Land Use Policy (2017), 65

tThis viewpoint paper presents a reaction to the article by Brandt et al. (2016). It highlights the complexitiesinherent to the attribution of deforestation impacts to policy interventions when using ... [more ▼]

tThis viewpoint paper presents a reaction to the article by Brandt et al. (2016). It highlights the complexitiesinherent to the attribution of deforestation impacts to policy interventions when using remote-sensingdata. This critique argues that in the context of the Congo a suite of factors (i.e., population density inparticular) other than those considered by Brandt et al. (e.g., type of forest, distance from roads and mar-kets) play essential roles in determining the fates of forests. It also contends that care is needed whenmaking decisions regarding which units will be included in the comparison group so that contextual fac-tors and on-the-ground information are properly considered (e.g., when logging operations are inactiveor when a concession is used for ‘conservation’ purposes). Finally, it proposes that a focus on an analysisof deforestation rates for a given level of timber production might be a metric that more accurately rep-resents one aspect of the consequences of forest management, which should also consider the appraisalof trade-offs associated with a larger set of social, financial and ecological objectives. [less ▲]

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See detailA look at Intact Forest Landscapes and their relevance in Central African forest policy
Haurez, Barbara ULiege; Daïnou, Kasso ULiege; Vermeulen, Cédric ULiege et al

in Forest Policy and Economics (2017), 80

Tropical forests are major providers of natural resources and ecosystem services but their ecological functions are at threat, due to increasing human pressure linked to economic development. The ... [more ▼]

Tropical forests are major providers of natural resources and ecosystem services but their ecological functions are at threat, due to increasing human pressure linked to economic development. The identification of priority areas for conservation is crucial for land use planning to ensure the protection of biodiversity and ecological function. Intact Forest Landscapes (IFLs), as defined by Greenpeace and World Resources Institute (WRI), are areas of the forest ecosystems not subjected to human activities. They have beenidentified by mapping human disturbances through remote sensing. Contrary to similar global-scale concepts, IFLs have been integrated into the standards of the certification body Forest Stewardship Council (FSC) and therefore have practical implications for forest management policies. The Motion 65, approved in the general assembly of FSC in 2014, mandates the protection of IFLs located in FSC certified logging concessions. Until the implementation of national standards, forestry operations are banished from 80% of the IFL area within each forest management unit. To trace the history and evaluate the suitability of IFLs in the Central African context, we searched for documents related to the IFL method, and related approaches focusing on the identification of areas devoid of human disturbances. The IFL method is simple and cost-effective and allows for a global assessment of the influence of human infrastructures and industrial exploitation on forests However, the method does not consider the situation below the canopy and those forest components not visible by satellites. For example, hunting, one of the main threats faced by wildlife in Central African forests today, cannot be detected with satellite imagery. On the other hand, other anthropogenic activities which remote sensing may detect may be compatible with forest ecosystem conservation. To better tailor the IFL approach to Central African forests, we recommend (i) the consideration of wildlife communities in the intactness analysis, (ii) a thorough evaluation of the impacts of human activities on forest ecosystems, and (iii) the integration of local stakeholders and governments in the design of land management strategies to respond to social, economic and environmental needs [less ▲]

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See detailTerrestrial photogrammetry: a non-destructive method for modelling irregularly shaped tropical tree trunks
Bauwens, Sébastien ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

in Methods in Ecology and Evolution (2016)

1. Irregularly shaped trees including trees with buttresses, flutes or stilt roots are frequent in tropical forests. The lack of an international standard tomeasure the diameter of such trees leads to ... [more ▼]

1. Irregularly shaped trees including trees with buttresses, flutes or stilt roots are frequent in tropical forests. The lack of an international standard tomeasure the diameter of such trees leads to high uncertainties in biomass estimation, tree growth and carbon budget monitoring. 2. In this study, we developed a new method based on terrestrial close-range photogrammetry for measuring andmodelling irregular stems. This approach is cheap and easy to implement in the field as it only requires a camera and a graduated rod. We validated the approach with destructive cross-sectionmeasurements along the stem of three buttressed trees. To demonstrate the broader utility of this method, we extended the validated approach to 43 additional trees belonging to two species: Celtis mildbraedii (Ulmaceae) and Entandophragma cylindricum (Meliaceae). Based on the three dimensional models, we computed shape indices for each tree, and we analysed the stem morphology of the two species. Finally, we analysed some standardized predictors for the estimation of above-ground biomass. 3. We found a high concordance between diameters derived from the photogrammetric process and destructive diameter measurements along the stem for the three calibration trees. We found that C. mildbraedii develop much stronger irregularities than E. cylindricum.We also identified a large intraspecific variation in trunk morphology for E. cylindricum. The basal area at 1 3 mheight (Darea130) seems to be amore robust predictor for biomass estimates (lowest Akaike information criterion and relative squared error) than diameter measured above buttresses (DAB) or diameter at breast height estimated from available taper model. Finally, Darea130 might be estimated with a good precision [root mean square error (RMSE) < 5%] with linear model based on the field measurements DABand the perimeter of the convex hull of the buttresses at 1 3 mheight (Dconvhull130). 4. In this study, we showed the high potential of the photogrammetry for measuring and modelling irregular stems. Photogrammetry could then be used as a non-destructivemeasurement tool to produce correction factors for standardizing the diameter of irregular stems at a reference height which is a key issue in tree growthmonitoring and biomass change estimation. [less ▲]

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See detailThe determinants of tropical forest deciduousness: disentangling the effects of rainfall and geology in central Africa
Ouedraogo, Dakis-Yaoba ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

in Journal of Ecology (2016)

1. Understanding the environmental determinants of forests deciduousness i.e. proportion of deciduous trees in a forest stand, is of great importance when predicting the impact of ongoing global climate ... [more ▼]

1. Understanding the environmental determinants of forests deciduousness i.e. proportion of deciduous trees in a forest stand, is of great importance when predicting the impact of ongoing global climate change on forests. In this study, we examine (i) how forest deciduousness varies in relation to rainfall and geology, and (ii) whether the influence of geology on deciduousness could be related to differences in soil fertility and water content between geological substrates. 2. The study was conducted in mixed moist semi-deciduous forests in the northern part of the Congo basin. We modelled the response of forest deciduousness to the severity of the dry season across four contrasting geological substrates (sandstone, alluvium, metamorphic and basic rocks). For this, we combined information on forest composition at genus level based on commercial forest inventories (62 624 0.5 ha plots scattered over 6 million of ha), leaf habit, and rainfall and geological maps. We further examined whether substrates differ in soil fertility and water-holding capacity using soil data from 37 pits in an area that was, at the time, relatively unexplored. 3. Forest deciduousness increased with the severity of the dry season, and this increase strongly varied with the geological substrate. Geology was found to be three times more important than the rainfall regime in explaining the total variation in deciduousness. The four substrates differed in soil properties, with higher fertility and water-holding capacity on metamorphic and basic rocks than on sandstone and alluvium. The increase in forest deciduousness was stronger on the substrates that formed resource-rich clay soils (metamorphic and basic rocks) than on substrates that formed resource-poor sandy soils (sandstone and alluvium). 4. Synthesis. We found evidence that tropical forest deciduousness is the result of both the competitive advantage of deciduous species in climates with high rainfall seasonality, and the persistence of evergreen species on resource-poor soils. Our findings offer a clear illustration of wellknown theoretical leaf carbon economy models, explaining the patterns in the dominance of evergreen versus deciduous species. And, this large-scale assessment of the interaction between climate and geology in determining forest deciduousness may help to improve future predictions of vegetation distribution under climate change scenarios. In central Africa, forest is likely to respond differently to variation in rainfall and/or evapotranspiration depending on the geological substrate. [less ▲]

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See detailTerrestrial photogrammetry: A non-destructive method for modeling irregularly shaped tropical tree trunks
Bauwens, Sébastien ULiege; Fayolle, Adeline ULiege; Gourlet-Fleury, Sylvie et al

Computer development (2016)

1. Irregularly shaped trees including trees with buttresses, flutes or stilt roots are frequent in tropical forests. The lack of an international standard to measure the diameter of such trees leads to ... [more ▼]

1. Irregularly shaped trees including trees with buttresses, flutes or stilt roots are frequent in tropical forests. The lack of an international standard to measure the diameter of such trees leads to high uncertainties in biomass estimation, tree growth and carbon budget monitoring. 2. In this study, we developed a new method based on terrestrial close range photogrammetry for measuring and modeling irregular stems. This approach is cheap and easy to implement in the field as it only requires a camera and a graduated rod. We validated the approach with destructive cross section measurements along the stem of three buttressed trees. To demonstrate the broader utility of this method, we extended the validated approach to 43 additional trees belonging to two species: Celtis mildbraedii (Ulmaceae) and Entandophragma cylindricum (Meliaceae). Based on the 3D models, we computed shape indices for each tree, and we analyzed the stem morphology of the two species. Finally, we analyzed some standardized predictors for the estimation of above-ground biomass. 3. We found a high concordance between diameters derived from the photogrammetric process and destructive diameter measurements along the stem for the three calibration trees. We found that C. mildbraedii develop much stronger irregularities than E. cylindricum. We also identified a large intra-specific variation in trunk morphology for E. cylindricum. The basal area at 1.3m height (Darea130), seems to be a more robust predictor for biomass estimates (lowest AIC and RSE) than diameter measured above buttresses (DAB) or DBH estimated from available taper model. Finally, Darea130 might be estimated with a good precision (RMSE < 5 %) with linear model based on the field measurements DAB and the perimeter of the convex hull of the buttresses at 1.3 m height (Dconvhull130). 4. In this study, we showed the high potential of the photogrammetry for measuring and modeling irregular stems. Photogrammetry could then be used as a non destructive measurement tool to produce correction factors for standardizing the diameter of irregular stems at a reference height which is a key issue in tree growth monitoring and biomass change estimation. [less ▲]

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See detailThe last 1,000 years in the Northern Congo Basin
Morin, Julie ULiege; Fayolle, Adeline ULiege; Favier, Charly et al

Conference (2015, November)

Review of the events that happened in the northern Congo basin during the last 1,000 yr. Positive impact of human disturbances on the regeneration of light-demanding trees. Negative impact of the European ... [more ▼]

Review of the events that happened in the northern Congo basin during the last 1,000 yr. Positive impact of human disturbances on the regeneration of light-demanding trees. Negative impact of the European colonization and following events on human populations and tree regeneration. [less ▲]

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See detailSeeing Central African forests through their largest trees
Bastin, Jean-François ULiege; Barbier, Nicolas; Réjou-Méchain, Maxime et al

in Scientific Reports (2015)

Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which ... [more ▼]

Large tropical trees and a few dominant species were recently identified as the main structuring elements of tropical forests. However, such result did not translate yet into quantitative approaches which are essential to understand, predict and monitor forest functions and composition over large, often poorly accessible territories. Here we show that the above-ground biomass (AGB) of the whole forest can be predicted from a few large trees and that the relationship is proved strikingly stable in 175 1-ha plots investigated across 8 sites spanning Central Africa. We designed a generic model predicting AGB with an error of 14% when based on only 5% of the stems, which points to universality in forest structural properties. For the first time in Africa, we identified some dominant species that disproportionally contribute to forest AGB with 1.5% of recorded species accounting for over 50% of the stock of AGB. Consequently, focusing on large trees and dominant species provides precise information on the whole forest stand. This offers new perspectives for understanding the functioning of tropical forests and opens new doors for the development of innovative monitoring strategies. [less ▲]

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See detailDid the savannah « flourished » 3000 years ago in the so-called Sangha River Interval of the Guineo-Congolian rainforest ? A retrospective study using stable isotopes and phytoliths
Bentaleb, Ilham; Freycon, Vincent; Gillet, Jean-François et al

Poster (2015, April)

We aim to improve our knowledge of the dynamic of the vegetation in Central Africa during the last 5 kyrs and to discuss the main hypothesis described in the literature - humans versus climatic impacts ... [more ▼]

We aim to improve our knowledge of the dynamic of the vegetation in Central Africa during the last 5 kyrs and to discuss the main hypothesis described in the literature - humans versus climatic impacts- both suggested as responsible of the Congo basin rainforest decline observed between 3 and 2.5 kyrs. We use the carbon isotopic composition of well-dated Central African soils to reconstruct the dynamic of the vegetation cover. We will discuss the carbon isotopic composition of the soil organic carbon methodology for reconstructing palaeovegetation in the light of Rayleigh distillation model. We showed that numerous sites exhibit a carbon isotopic ratios reflecting the Rayleigh distillation but few sites recorded real vegetation changes. Our study suggests that the vegetation of the Guineo-Congolian Region was disturbed between 3000 and 2000 BP (Before Present) without an extreme savannah expansion. We discussed the two hypotheses human versus climate impacts that may conduct to such new physiography of the vegetation. We suggest that the climate hypothesis is more likely than the human impact to explain the reduction of the Guineo-Congolian rainforest 3000 years ago. [less ▲]

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See detailComparative effectiveness of silvicultural interventions for increasing timber production and sustaining conservation values in natural tropical production forests. A systematic review protocol
Petrokofsky, Gillian; Sist, Plinio; Blanc, Lilian et al

in Environmental Evidence (2015), 4(8),

Background: Currently, about 400 million hectares of tropical moist forests worldwide are designated production forests, about a quarter of which are managed by rural communities and indigenous peoples ... [more ▼]

Background: Currently, about 400 million hectares of tropical moist forests worldwide are designated production forests, about a quarter of which are managed by rural communities and indigenous peoples. There has been a gradual impoverishment of forest resources inside selectively logged forests in which the volume of timber extracted over the first cutting cycle was mostly from large, old trees that matured over a century or more and grew in the absence of strong anthropological pressures. In forests now being logged for a second and third time, that volume has not been reconstituted due in part to the lack of implementation of post-logging silvicultural treatments. This depletion of timber stocks renders the degraded forests prone to conversion to other land uses. Although it is essential to preserve undisturbed primary forests through the creation of protected areas, these areas alone will not be able to ensure the conservation of all species on a pan-tropical scale, for social, economic and political reasons. The conservation of tropical forests of tomorrow will mostly take place within human-modified (logged, domesticated) forests. In this context, silvicultural interventions are considered by many tropical foresters and forest ecologists as tools capable of effectively conserving tropical forest biodiversity and ecosystem services while stimulating forest production. This systematic review aims to assess past and current evidence of the impact of silviculture on tropical forests and to identify silvicultural practices appropriate for the current conditions in the forests and forestry sectors of the Congo Basin, Amazonia and Southeast Asia. Methods: This systematic review will undertake an extensive search of literature to assess the relative effectiveness of different silvicultural interventions on timber production and the conservation value of forests, and to determine whether there is a relationship between sustainability of timber harvesting and the maintenance/conservation of other ecosystem services and biodiversity in production forests. Data will be extracted for meta-analysis of at least sub-sets of the review questions. Findings are expected to help inform policy and develop evidence-based practice guidelines on silvicultural practices in tropical forests. [less ▲]

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See detailNineteenth century human history explains the dominance of light-demanding tree species in Central African moist forests
Morin, Julie ULiege; Fayolle, Adeline ULiege; Favier, Charly et al

Poster (2015, March 21)

The canopy of central African moist forests is dominated by light-demanding trees. Most of these species show a distribution of diameters that indicates a regeneration shortage. Here we show through the ... [more ▼]

The canopy of central African moist forests is dominated by light-demanding trees. Most of these species show a distribution of diameters that indicates a regeneration shortage. Here we show through the combined analysis of botanical, palaeoecological, archaeological and historical data that most of these trees are not older than ca. 180 years. This age corresponds to the early 19th century (around 1830) when the slave-raiding, the interethnic wars and the colonization of the inlands by the Europeans disturbed the human spatial occupancy. After 1885, the spatial clumping of people and villages along the main communication axes induced less itinerancy in the forest. We believe that former activities such as shifting cultivation created scattered openings in the canopy, large enough to allow light-demanding trees to establish. Nowadays, common logging operations do not create openings sufficiently large for the regeneration of these high value timber species. Our findings emphasize the need to include considerations about the history of human spatial occupancy and activities to understand forest dynamics. We need silvicultural guidelines adapted to the autecology of the species. Population enforcements (e.g. enrichment) will be needed to ensure the sustainability of timber yields in forests dominated by long-lived light-demanding trees. [less ▲]

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See detailIdentification of charred botanical remains provides more accurate information on past history in Central Africa
Morin, Julie ULiege; Biwolé, Achille; Bourland, Nils et al

Poster (2015, January 30)

In palaeoenvironmental studies, charred botanical remains have rarely been identified to the species level before being sent to radiocarbon dating. Moreover, the age of most tropical spp. and thereby the ... [more ▼]

In palaeoenvironmental studies, charred botanical remains have rarely been identified to the species level before being sent to radiocarbon dating. Moreover, the age of most tropical spp. and thereby the age of the carbon sequestered during plant growth is not known. Dating unidentified charred wood in the tropics should be thus treated with caution because the accuracy of the dates is not guaranteed. Here we present 71 dates obtained on charred endocarps and wood charcoals sampled in soil pits in Cameroon and in the Rep. of the Congo. We taxonomically identified 43 samples then selected both identified and unidentified individual fragments for radiocarbon dating. We performed summed probability distributions of the dates calibrated in BP for the 43 identified and the 28 unidentified samples separately then for the whole dates. Results showed that the dates obtained on unidentified samples better fit the established chronology for Central Africa but that they also presented less precise standard deviations than the dates obtained on identified short-lived material, and that the dates on identified samples provide more detailed trends about the phases of human occupation in Central Africa after 2,500 BP. We can assume that dating unidentified material may introduce some blur into chronologies and that the selection of identified charred botanical remains should be systematically applied for palaeoenvironmental reconstructions in tropical contexts to refine the chronologies. [less ▲]

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See detailTree roots can penetrate deeply in African semi-deciduous rain forests: evidence from two common soil types
Freycon, Vincent; Wonkam, Christelle; Fayolle, Adeline ULiege et al

in Journal of Tropical Ecology (2015), 31(1), 13-23

Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to ... [more ▼]

Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than the 95 cm depth previously reported in the literature for tropical rain forests. As sampling depth could explain this discrepancy, we recommend a sampling depth of at least 3–5 m to accurately estimate root distribution. The drier the dry season, the deeper the sampling depth should be. Our results are consistent with global models of root distribution in forest ecosystems, which are driven by climate variables. We thus suggest that deep rooting could be common in rain forests with a marked dry season. [less ▲]

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See detailRecords of human activity during the late-Holocene in the soils of the African dense humid forest
Morin-Rivat, Julie ULiege; Biwolé, Achille; Bourland, Nils ULiege et al

Conference (2014, April 30)

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past ... [more ▼]

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic coast, but very little information is available further inland. In this perspective, soil records seem to be the most appropriated so as to appraise the spatial and temporal extent of human activity in the African dense humid forest. In this paper, we thus aimed to present a synthesis of the archaeological and archaeobotanical data obtained during several fieldwork campaigns in an archaeologically unexplored area of 200,000 km² located in southern Cameroon and the northern Republic of Congo. A total of 275 test pits, among them 30 pedological pits up to 150 cm deep, were excavated in the study area. So as to get a long temporal scale as well as a fine resolution spatial scale, we quantified wood charcoal and charred endocarps in soil samples by layers of 10 cm taken for 100 pits located along transects of systematic sampling. Spatial projections were performed using statistics together with multivariate analyses. AMS radiocarbon dating allowed interpreting the temporal framework. Evidence of past human activities through either artifacts or charred botanical remains was observed in all pits, in particular with the ubiquitous presence of charcoal at each site. Main charcoal peaks were interpreted as fields (slash-and-burn agriculture) in the vicinity of ancient villages, the later marked by the presence of both potsherds and oil palm endocarps. The dichotomy of these kinds of activities may have impacted differentially the environment during the past. The set of 73 radiocarbon dates extending from 15,000 BP to the present time provided more dates in the late-Holocene showing a bimodal distribution which was interpreted as two phases of human expansion with an intermediate phase of population crash. The 2300–1300 BP phase is correlated with the migrations of supposed farming populations from northwestern Cameroon. Between 1300 and 670 BP, less material could be dated. Following that population collapse, the 670–20 BP phase corresponds to a new period of human expansion known as the Late Iron Age. The dates obtained support the established chronology reported for whole central Africa. This study underlines the necessity of fieldwork efforts and of the usefulness of archives sealed in soil records so as to bring new, extensive and precise evidence of human activities in the Congo Basin. [less ▲]

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See detailHistoire humaine des forêts tropicales du nord du Bassin du Congo durant les deux derniers millénaires
Morin-Rivat, Julie ULiege; Biwolé, Achille; Bourland, Nils ULiege et al

Scientific conference (2014, March 26)

Identifier les indices d’activités humaines anciennes et les mettre en relation avec la composition floristique actuelle grâce à une approche multidisciplinaire.

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See detailThe end of roaming in the forest causes a loss of timber resources: the paradox of slash-and-burn agriculture
Morin-Rivat, Julie ULiege; Fayolle, Adeline ULiege; Favier, Charly et al

Conference (2014, February 27)

Tropical forests are not believed as pristine anymore. Their structure and specific composition are induced by past climatic and human disturbances over years. In the African moist forests, the emergent ... [more ▼]

Tropical forests are not believed as pristine anymore. Their structure and specific composition are induced by past climatic and human disturbances over years. In the African moist forests, the emergent trees are mainly light-demanding. These trees are considered to derive from the recent disturbances of the last centuries. Most of them are exploited for their timber. However, several of these tree species are currently suffering from a lack of regeneration that threatens the specific diversity of the forests and the sustainability of timber exploitation. Through dendrometric and radiocarbon analyses we found that the majority of the trees of the Congo Basin are not older than 160 years. This corresponds to about the year 1850 when the Europeans colonized the inner regions of Central Africa. By reassembling people along the road axes, the colonial administration reduced the forest roaming. Former activities such as slash and burn agriculture created large openings in the canopy that allowed light-demanding tree species to establish. Currently we observed that timber logging does not provide openings large enough for the recruitment of these species. We thus anticipate that adjustments in forest management strategies shall be made to preserve the forest resources, for instance by recreating the conditions of slash and burn agriculture. [less ▲]

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See detailNew Evidence of Human Activities during the Holocene in the Lowland Forests of the Northern Congo Basin
Morin-Rivat, Julie ULiege; Fayolle, Adeline ULiege; Gillet, Jean-François ULiege et al

in Radiocarbon (2014), 56(1), 209-220

In the last decade, the myth of the pristine tropical forest has been seriously challenged. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic forests ... [more ▼]

In the last decade, the myth of the pristine tropical forest has been seriously challenged. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic forests, but very little information is available about human activities further inland. In this study, we aimed at determining the temporal and spatial patterns of human activities in an archaeologically unexplored area of 110,000 km² located in the northern Congo Basin and currently covered by dense forest. Fieldwork involving archaeology as well as archaeobotany was undertaken in 36 sites located in southeastern Cameroon and in the northern Republic of Congo. Evidence of past human activities through either artifacts or charred botanical remains was observed in all excavated test pits across the study area. The set of 43 radiocarbon dates extending from 15,000 BP to the present time showed a bimodal distribution in the Late Holocene which was interpreted as two phases of human expansion with an intermediate phase of depopulation. The 2300–1300 BP phase is correlated with the migrations of supposed farming populations from northwestern Cameroon. Between 1300 and 670 BP, less material could be dated. This is in agreement with the population collapse already reported for central Africa. Following this, the 670–20 BP phase corresponds to a new period of human expansion known as the Late Iron Age. These results bring new and extensive evidence of human activities in the northern Congo Basin and support the established chronology for human history in central Africa. [less ▲]

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See detailImprove the characterization of tropical forests to improve management: policy brief
Gourlet-Fleury, Sylvie; Aleman, Julie; Bayol, Nicolas et al

Report (2014)

CoForChange has shown that management plans based on timber stock recovery are not enough to ensure the sustainability of these production forests. The variability of forest characteristics and their ... [more ▼]

CoForChange has shown that management plans based on timber stock recovery are not enough to ensure the sustainability of these production forests. The variability of forest characteristics and their different responses to disturbance should be considered in management decisions. [less ▲]

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