Matière organique et transformations structurales superficielles dans un sol ferrallitique rouge de la zone forestière du Cameroun

Les sols ferrallitiques modaux de la zone forestière du sud Cameroun présentent, dans la partie supérieure du profil, un horizon plus compact résultant de la dégradation de la structure initiale en microagrégats et d'une illuviation de l'argile. Cette étude vise à établir les relations entre les différenciations morphologiques et organiques se produisant dans cet horizon. Il semble que la matière organique agisse directement en développant une acidité qui favorise le lessivage de l'argile lorsqu'elle est faible, l'altération de l'hématite et des argiles lorsqu'elle est plus élevé

Carbon losses and sequestration with land use change in the humid tropics.

Changes in carbon stocks associated with the different land use systems combined with details on the time course of these changes during the land use rotation are necessary to estimate the net carbon losses and sequestration potential associated with these different land use conversions

Community Capacity for Implementing Clean Development Mechanism Projects Within Community Forests in Cameroon

There is a growing assumption that payments for environmental services including carbon sequestration and greenhouse gas emission reduction provide an opportunity for poverty reduction and the enhancement of sustainable development within integrated natural resource management approaches. Yet in experiential terms, community-based natural resource management implementation falls short of expectations in many cases. In this paper, we investigate the asymmetry between community capacity and the Land Use Land Use Change Forestry (LULUCF) provisions of the Clean Development Mechanism within community forests in Cameroon. We use relevant aspects of the Clean Development Mechanism criteria and notions of “community capacity” to elucidate determinants of community capacity needed for CDM implementation within community forests. The main requirements are for community capacity to handle issues of additionality, acceptability, externalities, certification, and community organisation. These community capacity requirements are further used to interpret empirically derived insights on two community forestry cases in Cameroon. While local variations were observed for capacity requirements in each case, community capacity was generally found to be insufficient for meaningful uptake and implementation of Clean Development Mechanism projects. Implications for understanding factors that could inhibit or enhance community capacity for project development are discussed. We also include recommendations for the wider Clean Development Mechanism/Kyoto capacity building framework

Carbon dynamics in slash and burn systems and land use alternatives: findings of the alternative to slash and burn programme

Conversion of natural ecosystems to agriculture, particularly through tropical deforestation, is a major source of greenhouse gas emission into the atmosphere. Too often, fallow intervals become increasingly shortened or eliminated as land use intensifies in recently cleared forests resulting in a large net loss of total system carbon. Total system carbon (TSC) was calculated for 116 sites in the humid forest zones of S.E. Asia (Indonesia), Africa (Cameroon) and the Amazon (Brazil and Peru) based on estimates of tree, understorey and root biomass, surface necromass and soil organic carbon. The land use categories examined were original forests (10), managed and logged-over forests (9), recently burned croplands (IS), bush and young improved fallows (17), tree fallows (8), secondary' forests (8), pastures (9), /mpercra spp. grasslands (8). immature experimental agroforests (10) and mature agroforests and tree plantations (19). The land uses were arranged into chronosequences based upon land use transition and duration. TSC in a 20 year ’’traditional” slash-and-bum sequence were (t ha l): original forest (305) to burned cropland (52) to bush fallow (85) to tree fallow (136) to secondary forest (219). Logging reduced forest system carbon by 124 t ha '. Ten year-old pastures and 13 year-old Imperóla spp. grasslands contained less TSC than croplands (-4 and -5 t C ha , resDectively). Recently established agmforesrry systems contain more TSC than did croplands (+11 t C ha1). Mature agroforests (130 t C ha1) contained significantly greater TSC than croplands, pastures and grasslands (p<0.00l) but significantly less than secondary forests of similar age (p < 0.001). Soil organic carbon (SOC) represented 25% of the TSC stocks in original forests and 84%, 82% and 91% in croplands, pastures and Imperóla spp. grasslands, respectively. Aboveground C accounted for a majority of the loss from forests converted to croplands (82%) but the SOC content of croplands was also reduced by 17% to 35 t C ha1 (approximately 0-20 cm). Carbon sequestration rates were calculated for three land use patterns derivéd from croplands. Natural fellows re-accumulated 7.9 t C ha * yr‘ following land abandonment (r = 0.92). Agroforestry systems, established at the time of initial land clearing, sequestered 3.3 t C ha1 yr1 (r = 0.70) and pastures/grasslands tended to lose C at a slow rate (600 kg ha1 yr'1, n.s.). Land use systems where trees are planted and managed have greater potential to sequester C than field crops or pastures, but at sequestration rates less than those of natural succession

Carbon sequestration and trace gas emissions in slash-and-burn and alternative land uses in the humid tropics

Alternatives to Slash-and-Burn Programme (ASB) were to determine those land-use systems that sequester more carbon and reduce trace gas emissions. The research consisted of three activities:1. Collect strategic information on changes in carbon stocks and land use, 2. Develop a database on trace gas fluxes from different land-use systems, and 3. Assess land rehabilitation techniques for increasing carbon sequestration. These activities were conducted through a collaborative effort involving numerous international and national partners. Research at the benchmark sites was done by EMBRAPA-Acre, EMBRAPA- Rondônia, CENA and ICRAF- Perú in Brazil; IRAD in Cameroon; and CRIFC-AARD, ICRAF, BIOTROP-GCTE Impact Centre Southeast Asia, and University of Brawijaya in Indonesia. In addition, ICRAF and INIA in Perú conducted crucial research on trace gas emissions. Modeling activities were led by Colorado State University. TSBF led the Climate Change Working Group and assisted with the design of standardized protocols, training, field measurements and the global synthesis