Biological invasion threatens the sandy-savanna Mussununga ecosystem in the Brazilian Atlantic Forest.
The sandy-savanna Mussununga is a little-known ecosystem that is already presenting signs of degradation due to effects of invasive species, anthropogenic disturbances, and land-use change. We investigated the effect of biological invasion by Acacia mangium and A. auriculiformis, disturbance promoted by fire and Eucalyptus management, as well as land-use change around Mussununga patches in this neglected ecosystem. Acacia occurrence is negatively related to abundance, basal area, and height of native woody species, and positively correlated with the proportion of dead woody plants. There is a trend of change in vegetation type from open savanna to woodland Mussununga promoted by Acacia. Mussununga patches disturbed by the planting of Eucalyptus species in the past have greater richness in the woody layer (large shrubs and trees), but lower abundance of species in the ground layer (small shrubs and herbs). The land-use change from forest to Eucalyptus plantation was associated with an increase of richness and abundance in the ground layer. Acacia tends to dominate the woody community in Mussununga by invading treeless patches, presenting a correlation with death of woody plants. Subsequently, Acacia promotes several changes that culminate in a height increment and change of the vegetation type. Different from Acacia, disturbance and land-use change associated with Eucalyptus, the main economic activity in the study area, affected both woody and ground layers. The conservation of Mussununga should include actions to preclude disturbance and land-use change, as well as monitoring and control of biological invasion.