1. Plant-soil microbes interactions play a central role in plant nutrient acquisition and thus ecosystem functioning and nutrient availability in agroecosystems. Adjustments in root morphology, root exudation and associations with microorganisms such as arbuscular mychorrizal fungi are common for phosphorus acquisition. Yet how plant belowground functional traits interact with microbial communities for P-acquisition remains largely unknown, limiting our understanding of phosphorus availability in agroecosystems.

2. Interactions between belowground functional traits and rhizosheath soil microbial communities for P-acquisition were investigated across eight herbaceous species with contrasting root traits. Root morphological and physiological traits involved in P-acquisition were quantified simultaneously with PLFA (phospholipid fatty acid) and NLFA (neutral lipid fatty acid) microbial bioindicators.

3. Multiple correlations were observed between root morphology, root exudates and rhizosheath fungal and bacterial communities. Root exudates and in particular release of malate and malonate were strongly linked with indicators of Gram-negative bacteria, which were correlated with changes in rhizosheath soil P concentration and plant P content.

4. Our results suggest that root exudation of carboxylates may play an important role in plant-soil microorganism interactions for P-acquisition, underlining their likely role in shaping microbial communities. Incorporating these interactions in biogeochemical models would lead to better predicting power and understanding of P cycling and ecosystem functioning.

Michel-Pierre Faucon, David Houben and Anissa Lounès-Hadj Sahraoui helped define the experimental design. Hacène Meglouli and Nicolas Honvault carried out the experiment. Stéphane Firmin, Hans Lambers and Arnaud Coutu helped process and interpret the data. All authors contributed to the final version of the manuscript.

Missing values indicated by "NA"