摘要：Traditionally, sustained yield (SY) has been viewed as a pillar of sustainable forest management (SFM), but this has been increasingly questioned. Ensuring SY of some species, i.e., a “strong sustainability” paradigm, could be an inadequate criterion if consideration of the social and economic components of the SFM concept are desired. SFM was translated into the ATO/ITTO set of principles, criteria, and indicators (PCI) for forest management in the Congo Basin; it resulted in the necessity for a certified logging company to ensure that no significant change in structure and floristic composition would result from logging operations. Besides raising the question of where to place the change threshold, we argue that sustainability must be considered from three indissociable viewpoints: ecological, social, and economic. The issue is how to balance these criteria, knowing that this assessment will involve potential conflicts of representations and beliefs. To discuss these questions, we used the example of two heavily logged timber species in the Congo Basin, sapelli (Entandrophragma cylindricum) and ayous (Triplochiton scleroxylon). Using long-term data collected from permanent sample plots in M’Baïki, Central African Republic, we calibrated a matrix model and performed short- and long-term simulations to examine (1) the potential effect of repeated logging of the species under the current national regulation system and (2) the rules that should be set to reach long-term SY. Ensuring long-term SY would require a 22% and 53% decrease in the felling intensity of E. cylindricum and T. scleroxylon, respectively, at first cut, together with an increase in overall logging intensity targeted toward less-used species. Light-demanding E. cylindricum and T. scleroxylon require open forests to regenerate and grow. This new set of rules is probably economically unsustainable for the current African forest industry, and will not meet the ecological requirements encapsulated in the ATO/ITTO PCI. We thus stress the following points: (1) the importance of most exploited species for the current industry may change as wood processing capacities become more efficient and markets change, potentially providing conditions for harvesting a greater number of species; (2) floristic change is unavoidable in these conditions, but this problem should be addressed at a broad scale, notably by ensuring a network of protected areas; (3) as long as the timber industry remains one of the few sources of employment and revenues in marginalized countries, reducing SFM to SY of the most exploited species on every concession appears questionable.
