Successional patterns of plant species and community diversity in a semi-deciduous tropical forest under shifting cultivation.

Question: Does shifting cultivation contribute to plant diversity in an Afrotropical semi-deciduous forest lacking large-scale natural disturbance? Location: Sanaimbo forest, Côte d'lvoire (Ivory Coast). Methods: We surveyed species assemblages, structural attributes of diversity, and life-history traits along a 30-year chronosequence of abandoned fields, comparatively to old- growth and selectively logged forest stands. Results: Patterns of species assemblages strongly changed with fallow area age, with respect to species' light requirements, suggesting niche partitioning along the successional gradient. Species richness, diversity and equitability were all increasing along this gradient. There were clear shifts in life-history traits spectra as the forest recovered, especially regarding leaf shape, lifespan and hairiness, diaspore dispersal, seed size, resprouting capacity, and life forms. Early colonization by the invasive Chromolaena odorata did not appear to impair secondary succession. Soil type influenced old-growth forest vegetation but not fallow vegetation. After 30 years of forest regrowth, plant communities exhibited endemism rates similar to those of ancient forests. Conclusions: Shifting cultivation appears to be a sustainable land use when small-sized fields are embedded in a forest matrix and when agriculture lasts only one to few years, preserves remnant trees, excludes fire and keeps several years between two clearing episodes. It may even contribute to the high biodiversity maintenance at the whole forest scale, by conserving the successional mosaic. However, conservation of old-growth forest patches is required for a number of climax tree species. [ABSTRACT FROM AUTHOR]