Increasing functional diversity in a plant community is thought to improve its global productivity by allowing species to partition more efficiently in the niche space, limiting their competition for ressources. Considering this theory, soil microorganisms such as arbuscular mycorrhizal fungi (AMF) symbionts are of major interest because they are known to enhance nutrient acquisition for the majority of land plants and harbour very distinct and conserved functional strategies among their three main taxonomic families. The aim of this study was to determine if increasing phylogenetic diversity in AMF communities positively influence plant community productivity and affect its global structure. A glasshouse experiment was perform were we manipulate AMF phylogenetic diversity by designing AMF communities containing taxa of one two or three families. These communities were inoculated in artificial mesocosms containing a set of 18 plant species known to naturally coexist. Three month after inoculation, we measured total productivity by recording plant dry mass production in each mesocosm. We also estimate community structure by analysing the mycorrhizal response of each plant species individually according to their phylogenetic relationships.
Results/Conclusions
Results showed that most of the time, total plant community productivity increased when AMF were present, especially when the AMF communities included two families. The distribution of mycorrhizal response along the plant phylogenetic tree showed that closely-related plants tends to have more dissimilar response than expected by chance, especially at high level of AMF phylogenetic diversity. Finally, the correlation between community productivity and estimation of community structure suggest that an intermediate level of AMF phylogenetic diversity is likely to maximize plant community productivity by reducing soil environmental constrain without enhancing too much plant-plant competition. This study emphasizes the importance of considering microorganism community structure in the soil to better understand plant community assemblage and productivity.