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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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See detailEnvironmental filtering of dense-wooded species controls above-ground biomass stored in African moist forests
Gourlet-Fleury, Sylvie; Rossi, Vivien; Réjou-Méchain, Maxime et al

in Journal of Ecology (2011), 99(4), 981-990

1. Regional above-ground biomass estimates for tropical moist forests remain highly inaccurate mostly because they are based on extrapolations from a few plots scattered across a limited range of soils ... [more ▼]

1. Regional above-ground biomass estimates for tropical moist forests remain highly inaccurate mostly because they are based on extrapolations from a few plots scattered across a limited range of soils and other environmental conditions. When such conditions impact biomass, the estimation is biased. The effect of soil types on biomass has especially yielded controversial results. 2. We investigated the relationship between above-ground biomass and soil type in undisturbed moist forests in the Central African Republic. We tested the effects of soil texture, as a surrogate for soil resources availability and physical constraints (soil depth and hydromorphy) on biomass. Forest inventory data were collected for trees ≥20 cm stem diameter in 2754 0.5 ha plots scattered over 4888 km². The plots contained 224 taxons, of which 209 were identified to species. Soil types were characterized from a 1:1 000 000 scale soil map. Species-specific values for wood density were extracted from the CIRAD’s data base of wood technological properties. 3. We found that basal area and biomass differ in their responses to soil type, ranging from 17.8 m² ha-1 (217.5 t ha-1) to 22.3 m² ha-1 (273.3 t ha-1). While shallow and hydromorphic soils support forests with both low stem basal area and low biomass, forests on deep resource-poor soils are typically low in basal area but as high in biomass as forests on deep resource-rich soils. We demonstrated that the environmental filtering of slow growing dense-wooded species on resource-poor soils compensates for the low basal area, and we discuss whether this filtering effect is due to low fertility or to low water reserve. 4. Synthesis. We showed that soil physical conditions constrained the amount of biomass stored in tropical moist forests. Contrary to previous reports, our results suggest that biomass is similar on resource-poor and resource-rich soils. This finding highlights both the importance of taking into account soil characteristics and species wood density when trying to predict regional patterns of biomass. Our findings have implications for the evaluation of biomass stocks in tropical forests, in the context of the international negotiations on climate change. [less ▲]

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See detailEstimation de l’impact de différents modes d’exploitation forestière sur les stocks de carbone en Afrique centrale
Durrieu de Madron, Luc; Bauwens, Sébastien ULg; Giraud, Adeline et al

in Bois et Forêts des Tropiques (2011), 308(2), 75-86

There has been little in-depth research to date on logging impacts in Central Africa in terms of carbon emissions. The REDD mechanism (Reducing Emissions from Deforestation and forest Degradation), has ... [more ▼]

There has been little in-depth research to date on logging impacts in Central Africa in terms of carbon emissions. The REDD mechanism (Reducing Emissions from Deforestation and forest Degradation), has brought this topic to the forefront, with the increase in managed logging concessions and the spread of low-impact logging methods. The aim of this study was to make a meta-analysis covering different experiences reported in the literature. The data collected were applied to a hypothetical logging operation in order to produce a theoretical assessment of its impact on carbon stocks. Our results show that, based on the assumptions used, managed forestry in a conventional logging concession with no forward planning would reduce carbon losses by one tenth, with 10 to 20 m3 of timber extracted per hectare. Most of the carbon savings would result from an increase in the minimum logging diameter. The other gains from low-impact logging would result from improving the design of logging roads, i.e., 5 to 8% of carbon losses due to conventional logging practice. These gains are higher than the error found for the nearest reality measurements made for clear-felled biomass in French Guiana. However, they are much lower than the errors calculated for biomass estimations in several studies available in the literature. In any case, introducing development planning and low-impact logging techniques in timber concessions are able to induce a favourable difference to carbon stocks in Africa’s dense forests. [less ▲]

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See detailDetecting large-scale diversity patterns in tropical trees: can we trust commercial forest inventories?
Réjou-Méchain, Maxime; Fayolle, Adeline ULg; Nasi, Robert et al

in Forest Ecology & Management (2011), 261(2), 187-194

In this paper we seek to identify the floristic determination biases contained in large-scale commercial inventories conducted by logging companies and to determine whether this impacts on the observed ... [more ▼]

In this paper we seek to identify the floristic determination biases contained in large-scale commercial inventories conducted by logging companies and to determine whether this impacts on the observed patterns of alpha and beta diversity. The study focused on floristic data recently collected by industrial timber companies in the tropical forests of the Central African Republic (28,229 0.5-ha plots spread over 14,000km2). A subset of these plots (n = 1107) was later re-sampled for controlling purposes by experienced botanists. The proportion of agreement between the two samplings was assessed for each species and independently for small and large trees, and at genus and family resolutions. Unsurprisingly, large trees and common species were more accurately identified than small trees and rare species. We found that the quality of the floristic determination increased slightly from species to families. We also detected a significant variation between concessions in the quality of the floristic determination that was more dependent on working conditions during forest inventories than on field workers. Contrary to a widespread belief, we did not find a strong bias toward commercial species, showing that commercial inventory data could also be valid for non-commercial species in ecological studies. Finally, we found that both alpha and beta diversity patterns in commercial inventories were highly consistent with those of the re-sampled inventory. This latter result shows that commercial inventories are well suited to detect large-scale patterns of floristic variation. Large-scale commercial inventories could thus play an important role in the identification of large-scale patterns in tropical tree diversity. This could enhance our ability to manage tropical forests by designing representative reserve networks and developing management plans that integrate diversity patterns at the landscape scale. [less ▲]

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See detailLes taux de reconstitution, un outil pour les gestionnaires forestiers dans le bassin du Congo
Bayol, Nicolas; Cassagne, Bernard; Billand, Alain et al

in Lettre de l'ATIBT (La) (2010), 32

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