Résumé
The plantation of fast-growing exotic species is an increasing phenomenon in tropical regions, with eucalyptus being the most prevalent species. Eucalyptus plantations (EP) have the potential to facilitate the regeneration of native species; however, in some cases, they may also hinder this process. The factors influencing the effects of EP on the regeneration of native species remain poorly understood. This study aims to identify the conditions that make these plantations favorable or unfavorable for the regeneration of native species.We investigated EP in agricultural landscapes in the south-eastern Malagasy highlands, located at the edge of dense rainforest. Floristic surveys were conducted in 20 EP situated at varying distances from natural forest fragments (near950?m in savannah). The understory of EP was characterised by a high abundance of native species. However, they were found to be more abundant and diverse in the intermediatestory of EP located near natural forest fragments. These native species are still in the early stages of plant succession, as they have essentially occupied the understory of the EP and contribute minimally to the basal area. The basal areas of native species in EP sites adjacent to natural forests are, in fact, comparable to those found in 0-5-year-old slash-and-burn fallows, which also occur on the periphery of natural forests. EP established in savannahs away from natural forests can act as catalysts for the natural regeneration of native species that would not occur without them. Conversely, EP on the edge of or within natural forests slow down the natural regeneration of native species, which would develop more rapidly in their absence. This study emphasises the significance of landscape spatial context in optimising the role of EP in the conservation and restoration of tropical forest ecosystems.