42 research outputs found
Quantification Des Stocks De Carbone De Trois Pools ClĂ©s De Carbone En Afrique Centrale : Cas De La ForĂȘt MarĂ©cageuse De La Likouala (Nord Congo)
The data of carbon stock of central African swamps forests are very few. This study carried out an assessment of the carbon stock of living biomass and coarse woody debris of three biotopes (flooded forest, seasonal flooded forest, and terra firm forest) of Likouala swamp forest (North of Congo). The average of the carbon stock are 190.72±98.7 tC/ha, 39.69±21.24 tC/ha, and 9.45±6.6 tC/ha respectively for above ground, billow ground, and coarse woody debris. The carbon stock of our swamp forest tends to increase generally from the flooded forest to the terra firm forest. In addition, the average of the coarse woody debris carbon stock increases with the increasing of the above ground carbon stock
Banque de graines du sol et déterminants de la germination du tali, Erythrophleum suaveolens (Guill. & Perr.) Brenan
peer reviewedCette Ă©tude Ă©value lâabondance des graines dâErythrophleum suaveolens dans la banque du sol des forĂȘts denses humides dâAfrique centrale. Les travaux ont Ă©tĂ© menĂ©s au Nord-Congo dans deux types forestiers : la forĂȘt Ă Celtis sur des sols argilo-sableux Ă sablo-argileux et la forĂȘt Ă Manilkara sur des sols sableux. Les tiges dâE. suaveolens (dhp â„ 10 cm) ont Ă©tĂ© inventoriĂ©es dans deux parcelles de 400 ha, et les structures diamĂ©triques de leurs populations ont Ă©tĂ© comparĂ©es. En outre, 80 fosses (2 x 40 fosses par type de forĂȘt) ont Ă©tĂ© creusĂ©es aux pieds de 20 arbres (10 par forĂȘt), sur trois couches contiguĂ«s de 10 cm chacune, soit Ă une profondeur totale de 30 cm, et lâabondance des graines dans la banque du sol a Ă©tĂ© Ă©valuĂ©e. La dormance des graines rĂ©coltĂ©es a Ă©tĂ© testĂ©e par des essais de germination aprĂšs traitement au H2SO4 et cinq graines prĂ©levĂ©es jusquâĂ une profondeur de 20 cm dans la forĂȘt Ă Celtis ont Ă©tĂ© utilisĂ©es pour estimer leur Ăąge par Spectroscopie de Masse par AccĂ©lĂ©rateur (SMA). La comparaison des structures diamĂ©triques indique une plus grande proportion de tiges de faible diamĂštre dans la forĂȘt Ă Celtis. Alors que les densitĂ©s de tiges (dhp â„ 10 cm) sont proches, avec 0,85 et 1,05 tige/ha respectivement, dans la forĂȘt Ă Celtis et la forĂȘt Ă Manilkara, les densitĂ©s de graines sont significativement plus Ă©levĂ©es dans la forĂȘt Ă Celtis (8,55 graines/m2) que dans la forĂȘt Ă Manilkara (0,15 graine/m2). Le pourcentage maximum de germination obtenu Ă©tait de 19,1 % pour des graines nâayant subi aucun traitement. Les lots traitĂ©s Ă lâacide ont prĂ©sentĂ© de moindres taux de germination. Ces graines pourraient se conserver une dizaine dâannĂ©es dans la banque du sol. Les facteurs pouvant influencer les variations de densitĂ© des graines sont discutĂ©s et des recommandations sylvicoles sont formulĂ©es
ï»żGuide pratique des plantations d'arbres des forĂȘts denses humides d'Afrique
In Africa, tree plantations are likely to be developed for several reasons: restoration of production capacities and services provided by natural forests, enhancement of agroforestry lands, easier harvesting of wood and non-wood forest products, etc. As exotic species only provide specific services, it is important to revitalize the planting of local species. This is the purpose of this guide, which focuses on species of dense rainforests, capitalizing on the results of past and recent trials in six African countries, and on the This is the purpose of this guide, which focuses on species of dense rainforests, capitalizing on the results of past and recent trials in six African countries, and mobilizing individual skills and knowledge. The book provides a practical approach to the various stages of a silvicultural program: seed collection and management, nursery construction and management, and plantation installation and management. An estimate of the costs and profitability of such plantations is also provided. Finally, the book describes in detail the silvicultural itinerary of 50 tree species of the African rainforests. This guide is intended for a wide audience: managers, forestry technicians and engineers, students and scientists interested in tropical silviculture
Pantropical variability in tree crown allometry
Aim
Tree crowns determine light interception, carbon and water exchange. Thus, understanding the factors causing tree crown allometry to vary at the tree and stand level matters greatly for the development of future vegetation modelling and for the calibration of remote sensing products. Nevertheless, we know little about largeâscale variation and determinants in tropical tree crown allometry. In this study, we explored the continental variation in scaling exponents of siteâspecific crown allometry and assessed their relationships with environmental and standâlevel variables in the tropics.
Location
Global tropics.
Time period
Early 21st century.
Major taxa studied
Woody plants.
Methods
Using a dataset of 87,737 trees distributed among 245 forest and savanna sites across the tropics, we fitted siteâspecific allometric relationships between crown dimensions (crown depth, diameter and volume) and stem diameter using powerâlaw models. Standâlevel and environmental drivers of crown allometric relationships were assessed at pantropical and continental scales.
Results
The scaling exponents of allometric relationships between stem diameter and crown dimensions were higher in savannas than in forests. We identified that continental crown models were better than pantropical crown models and that continental differences in crown allometric relationships were driven by both standâlevel (wood density) and environmental (precipitation, cation exchange capacity and soil texture) variables for both tropical biomes. For a given diameter, forest trees from Asia and savanna trees from Australia had smaller crown dimensions than trees in Africa and America, with crown volumes for some Asian forest trees being smaller than those of trees in African forests.
Main conclusions
Our results provide new insight into geographical variability, with large continental differences in tropical tree crown allometry that were driven by standâlevel and environmental variables. They have implications for the assessment of ecosystem function and for the monitoring of woody biomass by remote sensing techniques in the global tropics