Arbuscular mycorrhizal fungi dynamics in secondary shrublands of Madagascar: ecological insights for nurse plant selection in forest restoration

Abstract

This study aimed to assess the dynamics of arbuscular mycorrhizal fungi (AMF) associated with pioneer plant species across three one-year-old shrublands within Madagascar's natural rainforest ecosystem. Eight (8) pioneer shrub species were selected based on a floristic inventory, their symbiotic status, and their ecological behavior. The AMF communities associated with each species were described, and their symbiotic potential, expressed as mycorrhizal soil infectivity (MSI or MPN), was evaluated under controlled conditions. A total of 2862 spores were extracted, representing seven genera and 19 AMF species. Soils associated with Rubus moluccanus and Urena lobata exhibited significantly higher spore densities and diversity indices. The equitability index decreased in the following order: forest soil (0.68), Urena lobata, Solanum torvum, Lantana camara, Conyza sumatrensis, Rubus moluccanus, Psiadia altissima, Chromolaena odorata, Clidemia hirta, and grassland soil (0.25). Higher MSI values were recorded in C. sumatrensis than in P. altissima. Pearson correlation analysis showed that the relationships between MSI, spore density, and spore diversity were positive but not strong enough to predict functional effectiveness.

In conclusion, nurse plant selection should be guided by a combination of parameters, including their capacity to enhance AMF density, diversity, and infectivity, as well as the physico-chemical properties of soils that shape facilitation. Within this framework, Conyza sumatrensis appears as a promising candidate for forest restoration in Madagascar.