Tropical savanna restoration: topsoil removal and direct‐seeding promote a biodiverse and invasion‐resistant community

Abstract

Open ecosystems, such as native grasslands and savannas, cover vast tropical areas and sustain multiple ecosystem services. However, they face intense degradation due to conversion into pastures with exotic grasses that invade natural ecosystems. After abandonment, these areas do not naturally regenerate, and active restoration rarely reestablishes all native plant groups. Continuous reinvasion by exotics highlights the need for techniques that enhance invasion resistance while restoring community structure and diversity. We tested the effectiveness of combining topsoil removal and direct‐seeding to restore a tropical savanna degraded by pasture. We established an experiment including topsoil removal, topsoil removal + direct‐seeding, hoeing, and control. We analyzed soil fertility after treatments and monitored vegetation for three growing seasons, assessing plant cover, biomass, species richness, and composition. Comparisons were made to a native reference community. Topsoil removal substantially limited exotic grass invasion by reducing soil fertility to levels comparable to the reference community and likely depleting the invasive seed bank. Topsoil removal also promoted resprouting from deep bud banks, facilitating community re‐structuring and increasing species richness. Furthermore, topsoil removal combined with direct‐seeding enhanced native biomass and ground cover, limiting resources for exotic grasses and allowing communities to reach parameters similar to the reference community. This approach presents a promising strategy for effectively restoring the structure, diversity, and invasion resistance in degraded tropical savannas.