© iForest -Biogeosciences and Forestry IntroductionThe tropical rainforests of southern Cameroon as African rainforests are subjected to deforestation due to shifting cultivation, commercial timber and forest exploitation (Archard et al. 2002). This is stimulated by demographic and economic crisis forces. To counteract this process, the Cameroonian government has decided to develop, through the Tropenbos Cameroon Programme (TCP), methods and strategies for sustainable management of his rainforests (Foahom & Jonkers 1992). Fine roots are one of the factors to take into consideration in sustainable forest management, because of their critical role in nutrient cycling and tree regeneration (Saterson & Vitousek 1984). No information on roots is currently available for the tropical rainforests of southern Cameroon, especially on their changes among forest types and the rate of their recovery after selective logging.Because of their high nutrient absorption capacity and quick turnover, fine roots (0.5 to 2 mm diameter) play a key role in nutrient cycles (Castellanos et al. 2001). These roots tend to concentrate in the upper layers of the soil containing most of the nutrients released from decomposing litter. It is therefore a nutrient conservation mechanism in forests (Jordan 1991). Fine roots which are dynamic components of below-ground biomass represent about 30% of the above-ground biomass (Noordwijk et al. 1996) and between 40 and 85% of the net primary production according to the soil type (Hoffmann & Usoltsev 2001). The mortality and decomposition of fine roots contribute substantially to the carbon and nutrients stock in the soil. This contribution is equivalent (or even higher) to that of litterfall that returns carbon and nutrients from canopy to the soil (Hendrick & Pregitzer 1993).Most of the research on fine roots has been carried out in the temperate region (Vogt et al. 1986). However, available information on tropical forests, even though insufficient, show that fine root biomass is higher in tropical forests (4.5 -92.5 t ha -1 ) than in the temperate ones (0.5 -13.0 t ha -1 -Noij et al. 1993). Root biomass assessments as well as the study of root distribution in forest were very studious processes (Hendricks et al. 2006) because of the difficulty involved in sampling and extraction (Noij et al. 1993, Hoffmann & Usoltsev 2001. Moreover, contrary to the situation in temperate forests, where the period of dead vegetation material including roots and turnover are asynchronous, the production and mortality of fine root occur simultaneously, making it difficult to distinguish between living and dead roots.The aim of the present work is to assess the change of fine root biomass and their nutrient content in three undisturbed forests, developed on different soil types according to soil Taxonomy-USDA and differed also by soil chemical characteristic as K, Mg and Ca amount (t ha -1 ) and available P and water content (Van Gemerden & Hazeu 1999). The rate of fine root and their nutrient recovery after selective l...