Forest ecological research in the perspective of mitigating climate change in tropical ecosystem: case study of Cameroon (Central Africa)

There is a growing recognition that climate change is an important issue that impact adversely people livelihood and sustainable development Mitigating climate change through afforestation, reforestation and reducing emissions from deforestation and forests degradation (REDD) can become key components of land use planning and land use management in several tropical countries. Challenges in most countries include the design and implementation of sound research programs that satisfy the information needs of a national and international agenda on climate change. In the perspective of guiding forest-related research activities associated with climate change mitigation, this review synthesizes past research activities and provides baseline orientation for ecological research oriented towards climate change mitigation in Cameroon. The ecological and socioeconomic diversity offered by the country offers great opportunities for pilot mitigation research initiatives that can be extrapolated in other parts of central African sub region. However there is a need for enhanced research infrastructure, financial resources and capacity building in order to ensure continuous production of new scientific informatio

Biological nitrogen fixation potential by soybeans at two lowP soils of southern Cameroon

Biological nitrogen fixation (BNF) potential of 12 soybean genotypes were evaluated in condition of low and sufficient supply in two acid soils of southern Cameroon. The P sources were Togolese phosphate rock (PR) and triple super phosphate (TSP). The experiment was carried out during two consecutive years (2001 and 2002) at two locations with different soil types. Shoot dry matter, nodule dry matter, N and P uptake were assessed at flowering and the grain yield at maturity. Shoot dry matter, nodule dry matter, N and P uptake, and grain yield significantly varied with site and genotypes (P < 0.05). On Typic Kandiudult soil, nodule dry matter ranged from 0.3 to 99.3 mg plant-1 increasing significantly with P application (P < 0.05). Total N uptake of soybean ranged from 38.3 to 60.1 kg N ha-1 on Typic Kandiudult and from 18 to 33 kg N ha-1 on Rhodic Kandiudult soil. Under P limiting conditions, BNF ranged from -5.8 - 16 kg N ha-1 significantly higher values for genotype TGm 1511 irrespective of soil type. Genotype TGm 1511 can be considered as an important companion crop for the development of smallholder agriculture in southern Cameroon

Phosphorus benefits from grain-legume crops to subsequent maize grown on acid soils of southern Cameroon

We conducted field experiments over 2 years on two acid soils of southern Cameroon to test whether efficient uptake and use of phosphorus (P) from less available sources by grain legume genotypes could benefit subsequent rotational maize. We grew two crops each year. For the first crop we grew 4 genotypes of soybean and of cowpea, plus maize. For the second crop we grew maize. The first crops were fertilized with 0, 90 kg P ha?1 as phosphate rock (PR) or 30 kg P ha?1 as triple super phosphate (TSP). P application highly significantly increased shoot dry matter, P uptake, N2 fixation and grain yields of the grain legumes with TSP generally more effective than PR. Two of the soybean and two of the cowpea genotypes were more efficient at using P. Only the P-efficient soybean and cowpea genotypes increased subsequent maize yields. Yields of the subsequent maize grown in rotation were significantly correlated with shoot P uptake for which the quantity of P applied with the crop residues of the pre-crop appeared to be a major factor. We also grew the grain legumes in nutrient solutions and measured organic acid-anion exudation from roots, root-surface phosphatase-activity, and root morphological characteristics. Enhanced exudation of organic acid anions from roots of P-deprived plants might have contributed to the P acquisition efficiency under field conditions of the P-efficient cowpea genotypes and one of the P-efficient soybean genotypes. A higher activity of root-surface acid phosphatase might have been important for the other P-efficient soybean genotype. The results show, that the potential positive rotational effect of cowpea and soybean on the acid, highly P-sorbing soils of southern Cameroon depends on breeding and using P-efficient genotypes when sparingly soluble and suboptimal rates of soluble P fertilizers are used

Estoques de carbono no solo e na biomassa em plantações de eucalipto Carbon storage in the soil and in the biomass of eucalypt plantations

O eucalipto é a principal espécie florestal plantada no Brasil. Todavia, são escassas informações acerca do C estocado no solo e na biomassa desses plantios. Este trabalho teve como objetivos avaliar o estoque de C no solo (ECS) em plantações de eucalipto e determinar quais características edafoclimáticas determinam esse estoque. O estudo foi conduzido em eucalipto cultivado na região centro-leste do Estado de Minas Gerais, abrangendo cinco regiões: Cocais (CO), Rio Doce (RD), Sabinópolis (SA), Santa Bárbara (SB) e Virginópolis (VI). Foi calculado o estoque de C no solo até 100 cm de profundidade em plantações de eucalipto em áreas com predomínio de seis classes de solo: Cambissolo Háplico (CX), Latossolo Amarelo (LA), Latossolo Vermelho (LV), Latossolo Vermelho-Amarelo (LVA), Neossolo Flúvico (RU) e Plintossolo Pétrico (FF). Os estoques de C no solo variaram entre regiões e classes de solo. O maior ECS ocorreu no LV, com 183,07 t ha-1 de C, seguido pelas classes de CX, LVA, LA, FF e RU, com 135,65, 130,95, 121,58, 112,01 e 95,08 t ha-1 de C, respectivamente. Em relação ao estoque médio de C no solo por região, considerando todas as classes de solo, o maior ECS foi de 141,22 t ha-1; determinado na região de VI, na profundidade até 100 cm de profundidade, seguida pelas regiões SA, CO, SB e RD, com 135,54, 127,26, 112,89 e 80,79 t ha-1 de C, respectivamente. Ao se considerar o estoque de C total no sistema solo-planta, aos 84 meses de idade, a região de SA foi a que apresentou maior estoque, com 251,61 t ha-1; e a região de RD, o menor estoque, com 186,84 t ha-1 de C. O ECS pode ser estimado por equações compostas por características edofoclimáticas, sendo a variação em ECS explicada por características como teor de argila e de Al3+; pela altitude e pelo déficit hídrico da região.<br>Eucalypt is the main commercial forest species in Brazil, but very little information is available in the literature on the amount of carbon stored in the soil and in the biomass of these forest stands. The main objective of this study was to estimate the amount of soil-stored carbon (SSC) of eucalypt plantations and determine soil and climate characteristics that influence SSC. The study was carried out in the Central-Eastern region of Minas Gerais State, Brazil, in five micro-regions (CO, RD, SB, SA, and VI) with varying soil and climatic conditions. Soil carbon was determined to a depth of 100 cm. Carbon in the forest floor was estimated by allometric equations. The carbon stored in the soil-plant system differed among micro-regions and soil classes. SSC ranged from 183.1 t ha-1 in Red Latosol to 95.1 t ha-1 in Inceptisol, and was negatively correlated to soil K, Ca2+; and Mg2+ content and density in the top soil layer. SSC was highest in the micro-region VI (141.2 t ha-1; average value for all soil types) and lowest in RD (80.8 t ha-1). Considering the soil-plant ecosystem and the usual rotation age (84 months), the absolute SSC value was greatest in the micro-region SA (251.6 t ha-1) and lowest in RD (186.8 t ha-1). Regression equations showed that the clay and aluminum content and altitude and water stress explained most of the SSC variation