Matchmaking: a meta-analysis of plant growth-promoting microbial partnerships driving tree seedling performance in the Atlantic Forest biome

Abstract

Introduction: The Brazilian Atlantic Forest (BAF) is a biodiversity hotspot, and inoculating native seedlings with plant growth-promoting microorganisms (PGPMs) may enhance seedling vigor for forest restoration. Objectives: We performed a meta-analysis to evaluate the effects of PGPMs on BAF seedlings and identify strategies to optimize restoration outcomes. Methods: We synthesized data from 60 studies reporting biomass and nutrient content in seedlings inoculated with arbuscular mycorrhizal fungi (AMF), plant growth-promoting bacteria (PGPB), nitrogen-fixing bacteria (NFB), or AMF + NFB. Responses were compared across successional stages (pioneer, early, late secondary), functional groups (N2-fixing vs. non-N2-fixing), and experimental conditions (fertilization, inoculum complexity, and substrate sterility). Results: AMF inoculation produced the strongest benefits, particularly for pioneer and early secondary species. Pioneers also showed enhanced growth and N content with NFB, while both AMF and PGPB increased P content. Overall, PGPM inoculation was most effective in non-N-fixing species and early successional species, using single strains under sterile conditions, combined with P fertilization. Conclusions: Matching PGPM inoculants with the successional stage of target species can improve nursery practices and enhance restoration success.